PROVENANCE AND CLASTIC PETROFACIE9 OF WADHWAN FORMATION, SURENDRA NAGAR
AREA. GUJARAT, INDIA
Maittt of $]^Uos[opl^ IN
GEOLOGY
ARSHAD ZAMAN KHAN
DEPARTMENT OF GEOLOGY ALIGAAH MUSLIM UNIVERSITY
ALIGARH
1993
DS2243
D E P A R T M E N T O F G E O L O G Y ALIGARH MUSLIM UNIVERSITY
ALIGARH—202 002
Ofited 15.^.8U..ia3_
CERTIFICATE
Research v/ork on this dissertation
Provenance and Clastic Petrofacies of Wadhwan
Formation, Surendra Nagar Area, Gujarat, India,
was carried out by Mr. Arshad Zaman Khan at the
Department of Geology, Aligarh Muslim
University, Aligarh under my supervision.
I certify that the research work is an
original contribution of the candidate and he
is allowed to submit the dissertation for the
award of M.Phil Degree of this University.
(DR. KHURSHED AKHTAR) M.Sc.(Luck. ) ,Ph.D.(Alig.)
Reader
ACKNOWLEDGEMENTS
The author is grateful and deeply indebted to
Dr. Khurshed Akhtar, v/hose guidance and help at all the
time bring this work at the final stage.
The author is thankful to Professor S.N. Bhalla,
Chairman, Department of Geology^ . Aligarh Muslim
University/ Aligarh* for providing n^essary facilities
for research work.
Valuable help rendered by Dr. Shahid Farooq and
Dr. A.H.M. Ahmad/ Lecturers, Department of Geology/
A.M.U., Aligarh at various stages of this study requires
special mention.
Thanks are due to Dr». M.M. Khan, Mr. M. Alam and
Kazim Rangzan with whom the author had made a fruit ful
discussions at the time of work.
Lastly the author is thankful to Mr. H.S. Sharma
and Mr. Saleemuddln for taking up the job of typing and
drawing.
(ARSHAD^AMAN KHAN)
CONTENTS
CHAPTER I
INTRODUCTION
REGIONAL GEOLOGICAL SETTING OF VVESTERN INDIA 1
SAURASHTRA BASIN 4
LOCATION OF THE STUDY AREA 10
AIM AND SCOPE OF WORK 11
CHAPTER II
TEXTURE OF THE WADHWAN SANDSTONE 14
TECHNIQUE AND DATA PRESENTATION 15
STATISTICAL PARAMETERS OF GRAIN SIZE 16
ROUNDNESS 24
SPHERICITY 26
TEXTURAL MATURITY 29
BIVARIANT PLOTS 31
GRAIN CONTACTS AND COMPACTION 35
CHAPTER III
DETRITAL COMPOSITION OF THE WADHWAN SANDSTONES
METHODOLOGY 40
FRAMEWORK GRAINS 41
CEMENTS (AUTHIGENIC) 49
FACTORS CONTROLLING THE DETRITAL MINERALOGY 52
CHATPER IV
PETROFACIES AND PROVENANCE INTERPRETATION 6 6
PETROFACIES 70
PLATE TECTONIC SETTING 75
CHAPTER 4
SUMMARY AND CONCLUSIONS 81
REFERENCES 89
APPENDICES 101
XX
LIST OF TABLES
1. Generalized stratigraphic sequence of the
Saurashtra Penisula (After Biswas and Deshpande,
1983). 8
2. Statistical parameters of grain size
(percentile) of the Wadhwan sandstones. 17
3. Statistical parameters of grain size
distribution (M , (J^, SK^, K ) of the Wadhwan
sandstones based on Folk's (1980) method. 18
4. Roundness of sandsize detrital grains of the
Wadhv^an Sandstones. 25
5. Sphericity of the detrital grains of the
Wadhwan Sandstone. 27
6. Textural maturity of the Wadhwan sandstones. 30
7. Percentages of various types of grain to grain
contacts of the Wadhwan Sandstones. 37
8. Percentages of detrital minerals in the Wadhwan
Sandstones. 4 2
9. Percentage of detrital grains, clay, cements
and void spaces of the Wadhwan Sandstones. 50
10. Classification and symbols of grain types
(After Dickinson, 1985). 71
11. Percentage of detrital modes of the Wadhwan
sandstones (based on classification scheme of
Dickinson, 1985). 74
.11
LIST OF FIGURES
1. Regional Tectonic map of Western India showing
prominent rift basins and Precambrian orogenic
trends (After Biswas and Deshpande, 1983). 2
2. Geologic and Tectonic map of Saurashtra
Pc- insula (After Biswas and Deshpande, 1983). '1
3. Composite histograms of statistical parameters
of grain size distribution of the VJadhv/an
Sandstones (A-Mean size, B-Sorting, C-Skev;ness
and D-Kurtosis). 2 0
4. Composite histogram of grain roundness of the
Wadhwan sandstones. 28
5. Composite histogram of grain sphericity of the
Wadhwan sandstones. 28
6. Bivariant plots of different textural parameters
of the Wadhwan sandstones (A-Mean size versus
roundness, B-Mean size versus sphericity, C-Mean
size versus sorting). 33
7. Bivariant plots of different textural parameters
of theWadhwan sandstones (A-sorting versus
sphericity,B-sorting versus roundness). 34
8. Photomicrograph shovi?ing mostly grain • to grain
point contacts in the Wadhwan sandstones (X-90,
crossed).
9. Photomicrograph of a typical recrystallized
metamorphic quartz grain in the Wadhwan
sandstones showing mostly equant subindividuals
(X-90, crossed). 44
i V
10. Photomicrograph of a typical stretched
metamorphic quartz grain in the Wadhwan
sandstones showing elongated subindividuals
(X-90, crossed). # 44
11. Photomicrograph of ,a typical chert grains in the
Wadhwan sandstones chert has recrystallized to
microcrystalline quart; {X-90, crossed). 46
12. Photomicrograph of a pleochroic tourmaline grain
in the VJadhwan sandstone (X-90, uncrossed). 46
13. Scanning electron micrograph of the Wadhwan
sandstone showing well-developed hexagonal plates
of authegenic kaolinite arranged in vermicular
form.
14. Scanning electron micrograph of the Wadhwan
sandstone showing irregular aggregates of
allogenic kaolinite with rugged plate outlines.
Incipient silica overgrowths are seen on quartz
grain surfaces.
48
48
15. Photomicrograph of the Wadhwan sandstone showing
iron oxide cement filling up intergranular spaces
and fractures within the detrital quartz grains
(X-90, uncrossed). 51
16. Photomicrograph of the Wadhwan sandstone showing
oversized pore spaces lined with iron oxide
cement (X-90, uncrossed). 51
17. Photomicrograph of the Wadhwan sandstone showing
rare carbonate cement which has corroded detrital
quartz grains (X-90, crossed). 53
18. Classification of the Wadhvi?an sandstones
(According to the scheme of Folk, 1980). 69
19. Classification of the Wadhwan sandstones (Based on
the scheme of Dickinson, 1985). ^2
CHAPTER I
INTRODUCTION
REGIONAL GEOLOGICAL SETTING OF WESTERN INDIA
In many parts of the world including India the
Mesozoic Era is a tectonically important Era. Pangea which
existed in Palaeozoic Era was gradually torn apart during
Mesozoic Era v/ith the opening of Proto-Atlantic and Proto-
Indian Oceans. The separation of North America and Gondwana-
land took place in Late-Triassic Period. Gondwanaland itself
dismembered in Late-Jurassic resulting in the separation of
India and Africa from Australia, Antarctica and South
America.
The breakup of Gondwanaland along with opening of
Indian Ocean and northward drift of India with the final
detachment from East Africa/Madagascar and Antarctica were
discussed by many authors (Norton and Sclater, 1979; Patriat
and Segoufin, 1988; Powell et al, 1988; Scotese et al. 1988;
Westermann, 1988).
At different stages of evolution of the Indian
subcontinent during Mesozoic times three prominent rift
basins were formed in the western periphery of Indian
peninsula (Biswas 1982). The rift basins of western India
including Narmada, Cambay and Kutch are styled by three
principal Precambrian erogenic trends and their reactivation
in Mesozoic and Tertiary times (Fig. 1).
gt^^
», BOMBAY HIGH ^1^'rjr-SA
^ "%
\
l -n
0 1 0 0 2 9 OKm
Precombrion Tectonic Trend Rift Faults With Downthrow Major Structurol Trend Within Ri f t System
F i g . l , : Regional Tectonic map of Western Ind ia showing prominent r i f t ba s in s and Precambrian orogenic t r e n d s (After Biswas and Deshpande, 1983) .
The major tectonic boundry which divides the Indian
shield into a southern peninsular block and a northern
foreland block is the ENE-WSW Narmada-Sone lineament which
is parallel to Satpura orogenic trend (West 1962; Mathur et
al. 1968). The Narmada rift is formed in western part of
this megalineament by a fault parallel to the lineament.
This rift continues south of the Saurashtra block. The west
coast fault parallel to the NNW-SSE Dharwar trend is
responsible for shaping the present coastline. A series of
extension faults on the western Indian continental shelf,
which are sub-parallel to the Dharwar trend, have given rise
to horsts and grabens which are typical of a passive margin
(Pratsch, 1978; Biswas, 1982). The West coast fault extends
northward across the Narmada rift and forms the Cambay rift.
The Gulf of Cambay is considered as a trijunction with
Cambay basin as the aborted rift. The third important
Precambrian trend, the NE-SW Delhi-Aravalli trend continues
across Cambay basin into the Saurashtra platform.
The major events of plate tectonic activity and
development of the rift basins were synchronous (Pratsch,
1978; Biswas, 1982). The tectonic evolution of the basins
have been correlated v;ith the stages of - drifting of the
Indian plate since the time of its breakup from Gondwana-
land and till its collision with Eurasia. The rifting
developed progressively from north to south around
Saurashtra horst. The Kutch basin was formed in Early
Jurassic, followed by Cambay basin in Early Cretaceous.
Saurashtra area remained as a horst between Kutch and
Narmada basins till Early Cretaceous when it became a
depositional basin.
The Mesozoic sedimentation in Kutch-Saurashtra-
Cambay area was terminated by a major tectonic episode which
was accompanied by the extrusion of flood basalts (Deccan
Trap) during Late Cretaceous-Early Paleocene time.
SAURASHTRA BASIN
The Saurashtra basin which forms a horst block is
bounded by Kutch and Cambay rift basins to its north and
east respectively and by Surat depression to the south
(Fig. 1). The southern WSW^ENE trending fault is an
extension of Narmada geofracture. Towards western part of
the basin no major fault exists and it gradually deepens in
that direction. The Saurashtra basin is surrounded on three
sides by the Gulf of Kutch, Arabian sea and Gulf of Cambay
whereas the Gujarat alluvial plains extend to its
northeastern limit. The Precambrian basement of the basin
forms an ENE-WSW trending arch which plunges WSW.
Tectonic history
The transgression of sea into the coastal areas of
other parts of Gondwanaland during Jurassic-Cretaceous time
also invaded parts of the western margin of the Indian plate
(Krishnan 1960). At the same time Kutch basin opened up to
the north of the Saurashtra Peninsula which was uplifted and
a shallow epicontinental Jurassic sea ingressed into the
Kutch basin (Bisv/as, 1987; Krishna, 1987). The Saurashtra
basin developed in Early Cretaceous coinciding with uplift
of northerly Jurassic basin. The elongated Saurashtra rift
basin extending southwest to northeast from Gujarat coast to
Aravalli over a length of nearly 400 Km and bounded by major
faults to north and south (Biswas, 1982; Varadarajan and
Ganju, 198 9) represents a pericratonic composite rift system
(Sengor et al, 1978).
According to Cannon et al. (1981) and Tankard et al.
(1982) the beginning of plate separation in other parts of
the Gondwanaland during Jurassic and Early Cretaceous was
marked by the formation of pericratonic rift basins which
were similar to the pericratonic rifts (Kutch and
Saurashtra) of India.
Both of these basins (Kutch and Saurashtra) may
represent parts of an elongated extensional trough where up
and down rifting during Jurassic - Cretaceous time brought
about basin formation and sedimentation, first in northern
part (Jurassic of Kutch) and latter in southern part (Early
Cretaceous of Saurashtra) (Casshyap and Aslam, 1992).
Stratigraphy and Age
The Saurashtra basin comprises Mesozoic and Tertiary
sedimentary rocks and the Deccan Trap basaltic flows, the
later covering the major part of the Saurashtra Peninsula
(Fig. 2). The Mesozoic sedimentary rocks outcrop only in the
northeastern part of the Saurashtra peninsula. In the
outcrop area, the Mesozoic sequence is nearly 600 ra thick.
Besides the outcrop around Surendranagar, these rocks extend
in subsurface below the Alluvium (Recent) and Deccan basalt
(Late Cretaceous) towards the eastnortheast-westsouthwest
and north and south.
The Mesozoic sedimentary rocks which are exposed in
the northeastern part of the Saurashtra basin comprise two
formations: Dharangadhra Formation and Wadhwan Formation,
which are unconformably overlain by the Deccan Traps of Late
Cretaceous age. Thin Neogene and Quaternary deposits occur
along the Arabian Sea coast of the Saurashtra peninsula. The
generalised complete stratigraphic sequence of Saurashtra
peninsula is given in Table 1.
7 0^ 72^
23 • D h r a n g a d h r a
S u r e n d r a n a g a r Wadhwan
DWQ
22'
Porbanda
20 0 20 AO • — I 1 I
Kms
LEGEND
ALLUVIUM
PLEISTOCENE
^ PLIOCENE] EOCENE (LATERITE)
MIOCENE [ V ^ V ] (^^f.l^'^.^fOUS PALAEOCENE
APPROXIMATE POSITION OF PRECAMBRIAN BASEMENT ARCH
)
1 OHRANGAOMRA DOME 2 BHAUNAGAR NOSE 3 GOGHA NOSE
Gulf of Cambay
MeS020lC
Fiy.2t Geologic and Tectonic map of Saurashtra Peninsula (After Biswas and Deshpande, 1983).
Table 1: Generalised stratigraphic sequence of the
Saurashtra peninsula (after Biswas and Deshpande,
1983)
Age Formation
Recent to subrecent Alluvium
Unconformity
Quaternary Porbandar Formation
Unconformity
Mio-Pliocene Dwaraka Formation
Early Miocene Gaj Formation
Unconformity
Paleocene (?) Laterites
Unconformity—
Late Cretaceous Decoan Trap Foirmation (Basaltic flows)
-Unconformity-
Early Cretaceous Wadhwan Formation Dhrangadhra Formation
Unconformity
Precambrian Basement
The Dhrangadhra Formation which is more than 500 m
thick mainly comprises coarse elastics with minor amount of
shale and clay. The overlying Wadhwan Formation, about 50 m
thick, is made up of brick red to reddish brown sandstones
with small pockets of shales, and at places thin brownish
grey limestones are developed. The Wadhwan Formation is
overlain by Deccan Trap basalt flows. The Mesozoic
sedimentary sequence of the Saurashtra basin ranges in age
from Late Jurassic to Early Cretaceous (Upper Tithonian to
Albian: 145-97 m.y.). The Dharangadhra and Wadhwan Formation
are correlated with Bhuj Formation and Ukra Member of Bhuj
Formation. Marine fossils of Wadhwan Formation reported by
Chiplonkar and Borokar (1975) were correlated with those
fossils found in the Bagh beds and upper part of Nimar
Sandstone (Chiplonkar et al. 1977). Thus the Wadhwan and
Bagh sediments may be synchronous in age.
Palaeoclimate, Palaeogeography and Depositional Environmen-ts
The palaeogeographic reconstruction of the earth at
100 m.y. by Thompson and Barron (1981) shows that in
Cretaceous period the Surendranagar area was located at 44°
latitude, south of the equator, which lies within the wide
humid tropical belt. At this latitude the average annual
temperature was estimated as 21°C.
Palaeogeographic evolution of Mesozoic rocks in
Saurashtra basin was reconstructed on the basis of
lithofacies and palaeocurrent study by Casshyap and Aslam
(1992) .
10
The sedimentation in Saurashtra during Early
Cretaceous time started with deltaic environment which is
represented by Dharangadhra Formation. The deltaic
environment was follov>red by a short marine transgressive
phase of Aptian-Albian age which resulted in the deposition
of Wadhwan Formation, which is correlated with the
transgression of Kutch basin represented by Ukra beds
According to Casshyap et al. (1983), the Cretaceous
sedimentation in Saurashtra rift began with*the deposition of
shoreline conglomerate, and interbedded sandstone and shale
around Himatnagar near Aravalli highlands. The sedimentation
followed southwestward which is represented by dominance of
sandstone.
The calcareous lenses of coral and bryozoa in
uppermost Wadhwan Formation suggest onshore marine
ingression during the course of Wadhwan sedimentation.
Progressive downwarping of the basin may account for
transgression of shoreline environment towards northeast as
sedimentation progressed through time.
LOCATION OF STUDY AREA
Saurashtra basin is one of the three prominent
basins of western India. It is bounded by the Kutch and
11
Cambay rift basins to the north and east and Surat
depression to the south. It is the \7esternm0st basin in
peninsular India where the strata have been refered to as
Mesozoic Gondwana rocks (Pascoe, 1959). The basin extends
for about 400 km from Aravalli highland in the northeast to
the Gujarat coast in the southwest.
The study area (Surendranagar) lies on the northeast
part of the Saurashtra basin. It is situated about 200
kilometer southwest of Ahmadabad on the State Highway. It is
well connected with the other tov/ns of the area by private
and government road transport agencies. Excellent exposures
of the VJadhwan Formation are found in the sandstone quarries
located around the Surendranagar town (Longitude 71°50' and
Latitude 22^48').. Several of these quarries were visited and
representative samples of the VJadhwan Sandstone were
collected.
AIM AND SCOPE OF WORK
' The Cretaceous rocks of Gujarat have been
extensively studied for the purpose of depositional
environment and facies interpretation (Aslam, 1987; Ahmad
and Akhtar 1990; Casshyap and Aslam, 1992) but very little
research work has been carriedout on the provenance and
petrofacies evoluation of clastic rocks in general and
12
Mesozoic rocks of Gujarat in particular (Akhtar and Ahmad
1991; Akhtar et al, 1992).
The present study of the sandstones of Wadhwan
Formation of Surendranagar area mainly aims to reconstruct
their provenance and plate tectonic setting of their
deposition on the basis of petrofacies study. A critical
study of various factors influencing the provenance
interpretation has also been made.
The field work \\?as carried out for the purpose of
the collection of sandstone samples from different quarries
located around the Surendranagar town.
Thin sections prepared from 36 sandstone samples
from study area v/ere used for petrographic study. Textural
attributes of the sandstones were determined and included
grain size analysis and estimation of grain roundness.
Statistical parameters of grain size were computed with the
help of cumulative frequency curves and formulae according
to the method of Folk (1980).
For petrographic classification of the sandstones
and provenance interpretation, their detrital mineralogy was
studied. Folk's(1980) scheme of classification based on
composition of the detrital constituents and Dickinson's
(1985) classification emphasing the tectonic setting of
provenance were used.
13
Diagenetic processes of the sandstones were studied
with a view to checking the modification of detrital
mineralogy by diagenetic processes and their effect on
provenance interpretation.
CHAPTER II
TEXTURE OF THE WADHWAN SANDSTONES
A Study of texture of the Wadhwan sandstones was
taken up in view of the fact that the texture and
composition of detrital sediments are controlled by
provenance and other factors, such as transportation,
depositional environment and diagenesis (Suttner 1974).
The textural study of the VJadhwan sandstones
included their grain size analysis. A large number of
v;orkers have studied grain size distribution of clastic
sediments. Their studies were mainly related to hydrodynamic
conditions, processes and environments of deposition of
clastic sediments. Review of grain size parameters and their
relation v/ith depositional processes have been published by
Folk (1966), Visher (1969) and Friedman (1979).
The dependence of sandstone detrital modes on grain
size has been demonstrated by several workers (Blatt, 1967;
Young et al, 1975; Basu, 1976; Mack and Suttner, 1977).
The grains of various sizes may be produced by the
processes of rock disintegration and modified by other
processes like transportation and deposition. Some rocks
characteristically yield grains and detritus of different
sizes. For example, disintegration of quartzite will produce
15
blocks vi?hile other rocks (coarse grained acid igneous rocks
and gneisess) may undergo granular disintegration and yield
sand size grains. Smalley (1966) pointedout that size
distribution of quartz must be closely restricted by the
size distribution of quartz in the crystalline rocks of
source area.
The textural attributes of the VJadhwan sandstones/
such as size, roundness and sphericity were studied with a
view to interpreting the provenance of the sandstones, and
estimating the influence of texture on the detrital modes
and petrofacies. Interrelationship of various textural
attributes of the Wadhwan sandstones were studied with the
help of bivariant plots.
TECHNIQUES AND DATA PRERSENTATION
Different techniques of size measurement apply to
widely different size ranges. Riviere (1977) has described
various techniques for grain size measurements.
36 sandstone samples of Wadhv/an Formation were used
for grain size analysis. Thin sections were used for grain
size analysis because samples being hard enough were not
easily disaggregated. The examination of thin sections
showed that the original fabric is largely preserved. As a
whole there is a little modification of texture either by
16
reaction between the grains and cement, or by mechanical
compaction.
The grain size measurements were carried out with
the help of a micrometer eye piece, and 300 to 400 grains
were point counted per thin section. The present study
employed phi (0 ) scale and the size data was grouped into
half phi ih ^ ) class intervals.
Statistical parameters of grain size distribution
were determined with the help of cumulative frequency curve
plotted on the basis of grain size data. For plotting the
curves, grain size in phi ( f6 ) units was represented on the
X-axis and cumulative frequency percent on y-axis. From the
cumulative frequency curves the phi ( ^ ) units represented
by 9i5, yJ16, 025, f650, f675, 084, 095 percentiles were read
(Table 2). Statistical parameters of grain size were
calculated with the help of formulae given by Folk (1980).
The calculated parameters included Graphic mean (M )
inclusive graphic standard deviation (CJ-, ), inclusive graphic
skewness (SK_) and Graphic Kurtosis (K_) (Table 3). i G
STATISTICAL PARAMETERS OF GRAIN SIZE
Folk's (1980) statistical parameters of grain size
determined for the Wadhwan sandstones samples are described
as follows:
17
Table 2: Statistical parameters of grain size (Percentiles) of
the Wadhwan sandstones.
SainplG No'.
Q2 03 04 09 10 12 13 14 15 16 17 18 20 21 22 23 24 25 29 30 31 32 33 34 36 39 41 42 43 44 45 46 47 49 50 55
izJ5
- 0 . 1 5 0 . 1 0 . 2 0 . 4 0 . 1 5
- 0 . 7 5 0 . 4 5 0 . 1 5 0 . 3 5 0 . 1 5 0 . 2 5 0 . 7 5 0 . 0 0 . 2 0 . 0 5 0 . 7
- 0 . 2 5 0 . 1 5 0 . 8 0 . 2 5 1 . 1 0 . 4 5 1 . 4 0 . 8 5 0 . 3 0 . 1 0 . 0 5 0 . 3 0 . 4 0 . 8 0 . 0 1 . 3 0 . 7 5 0 . 3 5 0 . 0
- 0 . 4 5
jzJ16
0 . 4 0 . 9 0 . 8 1 . 0 5 0 . 7 5
- 0 . 1 5 1 . 0 5 0 . 8 0 . 7 5 0 . 7 0 . 7 5 1 . 0 0 . 4 0 . 5 5 0 . 8 5 1 . 3 5 0 . 0 0 . 5 1 . 2 0 . 7 5 1 . 8 0 . 8 5 1 . 7 1 . 3 0 . 8 5 0 . 4 5 0 . 4 5 0 . 7 0 . 8 1 . 1 0 . 5 1 . 5 5 1 . 2 0 . 6 1 . 1 0 . 1
(z$25
0 . 7 5 1 . 3 1 . 0 1 . 3 1 . 0 0 . 1 1 . 3 0 1 . 0 5 0 . 9 0 . 9 5 0 . 9 5 1 . 2 5 0 . 6 5 0 . 7 5 1 . 1 1 . 6 5 0 . 2 0 . 7 1 . 4 5 0 . 9 5 2 . 0 1 . 0 1 . 9 5 1 . 5 1 . 1 0 . 6 0 . 6 5 0 . 9 5 1 . 0 5 1 . 3 0 . 8 5 1 . 8 1 . 5 0 . 9 1 . 5 5 0 . 5 5
jzJ50
1 . 4 5 1 . 4 5 1 . 6 1 . 9 5 1 . 5 0 . 8 5 1 . 9 1 . 8 0 1 . 3 5 1 . 5 1 . 3 5 1 . 8 1 . 3 5 1 . 3 1 . 6 2 . 1 5 0 . 9 1 . 5 5 2 . 0 1 . 6 2 . 4 5 1 . 5 2 . 4 5 2 . 0 1 . 6 5 1 . 0 1 . 1 1 . 6 5 1 . 6 1 . 7 5 1 . 5 2 . 1 2 . 1 5 1 . 6 2 . 3 1 . 7
jz$75
2 . 5 2 . 0 2 . 3 5 2 . 4 2 . 3 5 1 . 6 5 2 . 5 2 . 1 5 2 . 1 2 . 3 5 2 . 0 5 2 . 4 5 2 . 2 5 2 . 1 5 2 . 2 2 . 8 2 . 1 2 . 5 5 2 . 6 2 . 3 3 . 2 5 2 . 2 2 . 9 5 2 . 4 5 2 . 5 5 1 . 7 1 . 8 5 2 . 2 5 2 . 4 5 2 . 3 5 2 . 2 2 . 5 5 2 . 6 2 . 1 5 2 . 7 5 2 . 6 5
tz$84
2 . 8 2 . 2 5 2 . 7 5 2 . 7 2 . 7 5 1 . 9 5 2 . 8 5 2 . 4 0 2 . 3 5 2 . 7 5 2 . 4 5 2 . 8 2 . 7 5 2 . 5 2 . 6 3 . 0 5 2 . 5 5 3 . 1 2 . 9 5 2 . 7 3 . 7 2 . 6 5 3 . 3 2 . 6 5 3 . 1 2 . 0 5 2 . 2 5 2 . 5 0 3 . 0 5 2 . 7 5 2 . 4 5 2 . 7 5 2 . 9 2 . 4 3 . 0 5 3 . 3
jzJ95
3 . 3 2 . 7 3 . 7 5 3 . 6 5 3 . 5 2 . 8 3 . 6 5 3 . 0 5 2 . 7 5 3 . 6 2 . 8 5 4 . 0 3 . 5 3 . 9 3 . 7 5 3 . 9 5 3 . 2 5 3 . 9 3 . 9 5 4 . 0 5 4 . 3 5 3 . 4 3 . 8 5 3 . 1 5 3 . 8 5 2 . 6 5 3 . 2 5 2 . 9 4 . 1 5 3 . 8 2 . 9 5 3 . 4 5 3 . 5 5 2 . 9 4 . 1 5 4 . 4
18
Table 3: Statistical paramctcrn of grain size distribution of Hadhwan sandstones based on Folk'i
(1968) method (graphic incluaiv* graphic standard deviation - O", , inolualm
graphic skcwness • SK., graphic kurtosls •KG)
!IO. Verbal limit Verbfll Limit SK, Verbal U n i t Verbal limit
02 03 04 09 10
12 13 14 15 16 17 18 20 21
22 23 24
25 29 30 31 32 33 34
36 39. 41
42 43
44 45 46
47 49 50 55
1.55
1.50 1.7 1.9 1.6
0.88 1.93 1.66 1.4 1.65 1.5 1.8 1.5 r.45
1.6 2.18 1.15
1.7 2.05 1.6 2.65 1 .66 2.48 1.98
1.86 1-16 1.26
1.6 1.81
1.86 1.48 2.1
2.08 1.53 2.15 1.7
Medium Mertiura Medium MeHiun Mvrtlum
COflrsp Medium Medium Medium Medium Medium Medium Medium Medium
Medium Fine Medium
Medium Fine Medium Fine Medi urn Fine Medium
Medium Medium Medium
Medium Medium
Medium Medium Fine
Fine Medium Fine Medium
1.12 0.72 1.01 0.89 1.0
1.05 0.93 0.8 0.76 1.0 0.79 0.9 1.11 1.04
0.99 0.91 1.16
1.21 0.9 1.05 0.96 0.89 0.77 0.67
1.09 0.78 0.93
0.84 1.12
0.86 0.92 0.62
0.84 0.83 1.1 1.53
Poorly sorted Moderately sorted Poorly sorted Moderately sorted Modaratoly sorted
Poorly sorted Moderately sorted Moderately sorted Moderately sorted Moderately sorted Moderately sorted Moderately sorted Poorly sorted Poorly sorted
Moderately sorted Moderately sorted Poorly sorted
Poorly sorted Moderately sorted Poorly sorted Moderately sorted Moderately sorted Moderately sorted Moderately well sorted Poorly sorted Moderately sorted Moderately sorted
Moderately sorted ' Poorly sorted
Moderately sorted Moderately sorted • Moderately well sorted Moderately sorted • Moderately sorted • Poorly sorted Poorly sorted
0,13 Fine skewed 0.08 Near symmetrical 0.18 Fine skewed
-0.02 Hoar symmetrical 1.09 Strongly Fine
skewed 0.06 Near symmetrical
-0.09 Near symmetrical -0.18 Coarse skewed 0.2 Fine skewed 0.20 Fine skewed 0.21 Fine skewed 0.22 Fine skewed 0.2 Fine skewed 0.31 Strongly fine
skewed 0.15 Fine skewed 0.07 Near symmetrical 0.31 Strongly fine
skewed 0.21 Fine skewed 0.15 Fine skewed 0.2 Fine skewed 0.23 Fine skewed 0.27 Fine skewed 0.1 Fine skewed
-0.01 Near symmetrical
0.25 Fine skewed 0.28 Fine skewed 0.3 Strongly fine
skewed -0.03 Near symmetrical 0.32 Strongly fine
skewed 0.28 Fine skewed -0.01 Near symmetrical 0.16 Fine skewed
•0.05 Near symmetrical •0.04 Near symmetrical -0.16 Coarse skewed 0.05 Near symmetrical
0.80 1.50 1.10 1.2 1.0
93 09 70 82 01 0 22 89
1.08
1.38 1.16 0.76
83 12 18 06 01 0 0
0 95 10
.83 ,09
17 92 17
1.0 0.83 1.43 0.9
Platy kurtic Lepto kurtic Mesokurtic Lspto kurtic Mesokurtic
Mesokurtic Mesokurtic Platy kurtic Platy kurtic Mesokurtic Mesokurtic Lepto kurtic Platy kurtic Mesokurtic
Lepto kurtic Lepto kurtic Platy kurtic
Platy kurtic Lepto kurtic Lepto kurtic Mesokurtic Mesokurtic Medokurtic Mesokurtic
Mesokurtic Mesokurtic Mesokurtic
Platy kurtic Mesokurtic
Lepto kurtic Mesokurtic Lepto kurtic
Mesokurtic Platy kurtic Lepto kurtic Mesokurtic
19
Graphic Mean (M )
Folk (1980) proposed the Graphic Mean (M^) as a
measure of average size. This parameter is much better than
the median, because it is based on three points and gives a
better overall picture and it is much easier to determine
as compared to the mean computed by the method of moments.
Mean size of sandstones under study was calculated on the
basis of the following formula devised by Folk (1980).
M z
^16 + ^50 - 84
The sandstones were classified on the basis of
verbal limits of grain size proposed by Folk (1980).
The Graphic Mean (M ) of various samples from the
study area ranges from 0.88 to 2.65 ^ (Table 3). The mean
size of 78 percent of samples falls within the medium sand
range and 19 percent belong to fine sand and only 3 percent
fall within the coarse sand range (Fig. 3A). Thus, the
sandstone^ are mainly medium grained and some are fine
grained. Coarse grained sandstones are rare.
Inclusive Graphic Standard Deviation ( O", )
Inclusive Graphic Standard Deviation as a measure of
sorting of sediments was proposed by Folk (1980). Sorting is
determined by dispersion around central tendency. Because
20
TOO
80
£ 60 u
a> A O
20
0
A
1
Mean s i ze
1
100
80
60
AO
20
0
B
S o r t i n g
1 C M F PS MS MWS
100
80
c 60 it u i AO
20
0
Skewness
SFS FS NS CS
100
80
60
^0
20
0
D
Kurtosis
M
Fiy. 3: Composite histograms of statistical parameters of grain size distribution of the Wadhwan sandstones
A - Mean size (C=coarse grained, M = medium grained, F = Fine grained)
B - Sorting (PS= poorly sorted, MS=Moderately sorted, MWS = moderately well sorted)
C - Skewness (SFS = Strongly fine skev/ed, FS = Fine skewed, NS = near symmetrical, CS = coarse skev/ed).
D - Kurtosis (P = Platykurtic, M= Mesokurtic, L=Leptokurtic)
21
the tails of a distribution have been thought to be
environmentally sensitive, estimates of sorting have been
designed to reflect them.
The inclusive graphic standard deviation of grain
size was calculated with the help of Folk's (1980) formula
given below:
Q- = _^84_1_^16_ _ 1 95 - < 5 6.6
The samples were also classified according to the
verbal limits proposed by Folk (1980).
Inclusive graphic standard deviation values of
samples under study range from 0.62 to 1.53 f6. Out of 36
samples, 22 samples (61.0%) are moderately sorted, 12
samples (33.0%) poorly sorted and 2 samples (6.0%)
moderately v ;ell sorted (Fig. 3B). Thus, the sandstones are
mainly moderately to poorly sorted.
Sorting of sediments generally depends upon
stability and competency of currents. If currents are of
'relatively constant strength, sediments will be very well
sorted to well sorted but fluctuating currents will give
rise to poorer sorting. In the Wadhwan sandstones most of
the samples are moderately sorted to poorly sorted which
22
indicate that the currents were not strong and persistent
enough to produce a well sorted sediment.
Inclusive Graphic Skewness {SK_)
The asymmetry of distribution is measured by
skewness and is determined by the relative importance of the
tails of the distribution. The skewness or asymmetry is also
determined by the position of the mean with respect to
median. The skewness is negative and the sample is coarse
skewed when the mean is located towards the coarse side of
the median. When skewness value is positive, the sample is
described as fine skewed because the mean is located towards
the finer side of the median.
Skewness of the sandstones under study was
calculated on the basis of the following formula devised by
Folk (1980).
I +
The sandstones were classified on the basis of
verbal limits of skewness proposed by Folk(1980).
Inclusive graphic Skewness (SK^) values of the
samples under study range from - 0.01 to 1.0 fi. Out of 36
samples, 5 samples (14.0%) are strongly fine skewed, 18
23
samples (50%) are fine skewed, 11 samples (30.0%) are near
symmetrical and 2 samples (6.0%) are coarse skewed (Table 3
and Fig. 3C). Thus, majority of the samples are fine skewed.
Graphic Kurtosis (K^)
Kurtosis is a measure of peakedness of the
distribution and measures the ratio between the sorting in
the tails of the curves and sorting in the central position.
If the central position is better sorted than the tails, the
curve is said to be excessively peaked or Leptokurtic; when
tails are better sorted than the central portion, curve is
deficiently or flatpeaked and platykurtic.
Kurtosis of the sandstones understudy Vi?as
calculated on the basis of the following formula devised by
Folk (1980).
J 95 " " 5 ^G
2.44 (jz5 5- izi25)
The sandstones were classified on the basis of
verbal limits of kurtosis proposed by Folk (1980).
The kurtosis values of the studied samples range
from 0.70 to 1.5 «J. Out of 36 samples, 8 samples (22.0%)
are platykurtic, 18 samples (50.0%) are mesokurtic and 10
samples (28%) are leptokurtic (Table 3 and Fig. 3D). Thus,
24
mesokurtic samples are dominant and the rest are almost
equally divided leptokurtic and platykurtic ones.
ROUNDNESS
Roundness of grain depends upon the sharpness of its
edges and corners. In many cases roundness have been used
interchangeably with shape but roundness is different from
and independant of shape.
Wentv/orth (1919) first clearly defined roundness and
quantitatively measured it as ^i/'^ii where r is the radius
of curvature of the sharpest edge and R^ is one half the
longest diameter.
Wadell (1935) defined roundness as the ratio of the
average radius of curvature of the several corners and edges
to the radius of curvature of the inscribed sphere. But both
Wentv/orth's and Wadell's methods for determining the
roundness require measurements in three dimensions and thus
are difficult, cumbersome, and time-consuming.
Russel and Taylor (1937), Krumbein (1940), Powers
(1953) employed tvi?o-dimensional images of particles for
estimating roundness. Russel and Taylor (1937) proposed five
roundness classes but their class limits were not
systematically chosen and arthmatic means of the class
intervals v/ere used as mid points. Krumbein (1940) presented
nine different roundness values which were however very close
together.
25
Table 4i Roundnoon of dotrltnl grains of the Hadhwan sandstones, Surondranagar area (Roundness
clasncn according to Powers' scale)
Eamplf Total Vory angular Angular Subangular Subroundod Rounded Well rounded Mean Ho. grain (0.12 - 0.17) (0.17-0.25) (0.25-0.37) (0.37-0.49) (0.49-0.70)(0.70 - 1.0) Roundness
N N i N % N « N % N 8 N i
02 03 04 09 10 12 13 14 15 16 17 ic 20 21 22 23 24 25 29 30 31 32 33 34 36 39 41 42 43 44 45 46 47 49 50 55
94 18.3 126 115 99 109 101 105 126 145 112 120 136 112 115 121 67 69 120 172 llfl 125 131 136 144 124 102 118 112 122 124 139 136 141 124 112
7 9 11 6 6 9 7 5 13 14 11 7 9 6 12 3 8 6 11 12 10 12 11 19 16 13 9 12 12 14 12 20 17 21 23 15
8 7 9 5 6 8 7 5 10 10 10 6 7 5 10 2 12 8 9 7 8 10 8 14 11 10 9 10 11 11 10 15 12 15 19 13
19 29 15 17 10 13 23 9 27 38 24 32 21 16 29 18 12 15 23 21 23 28 23 28 33 33 20 26 22 35 30 25 28 26 26 24
20 22 12 15 10 12 23 8 21 26 21 27 15 14 25 15 18 22 19 12 20 22 18 21 23 27 20 22 20 29 24 18 21 18 21 22
22 32 23 31 22 29 26 20 46 39 26 39 45 40 34 42 21 17 27 48 30 30 26 31 34 39 28 28 26 29 33 27 31 29 34 25
23 24 18 27 22 27 26 19 36 26 23 32 33 36 30 35 31 25 22 28 25 24 20 23 24 31 27 24 23 24 27 19 23 21 27 22
26 38 51 44 45 45 31 52 15 30 37 32 42 43 28 43 16 24 32 65 31 35 44 42 46 2B 25 25 31 22 27 27 35 39 27 27
28 28 40 38 46 41 31 50 12 21 33 27 31 38 25 36 24 35 27 38 26 28 34 31 32 23 24 21 28 18 22 19 26 28 22 24
16 20 17 14 12 10 8 14 15 20 11 8 11 4 8 9 6 5 19 21 16 15 19 10 12 B 14 20 14 14 18 28 19 20 8 15
17 15 14 12 12 9 8 13 12 14 10 6 8 4 7 7 9 7 16 12 14 12 14 7 8 7 14 17 12 11 14 20 14 14 6 13
4
e 9 3 4 3 6 5 11 4 3 2 8 3 4 6 4 2 8 5 8 5 8 6 3 3 6 7 7 8 4 12 6 f. 6 6
4 4 7 3 4 3 6 5 9 3 3 2 6 3 3 5 6 3 7 3 7 4 6 4 2 2 6 6 6 7 3 9 4 4 5 6
0.38 0.37 0.40 0.38 0.39 0.37 0.36 0.41 0.36 0.34 0.35 0.33 0.37 0.35 0.33 0.38 0.35 0.35 0.38 0.38 0.38 0.36 0.39 0.34 0.34 0.32 0.37 0.38 0.37 0.35 0.35 0.39 0.35 0.36 0.32 0.36
26
In the present study roundness scale given by Powers
(1953) has been used. This scale has six roundness grades in
such a way that the class limits closely approximate a y/2
geometric scale. Mean roundness of each sample was determined
by conventional statistical method employing the Powers'
class limits values.
The roundness of detrital particles of the Wadhwan
sandstones was measured in 2S samples and average of about
100 grains per thin section were measured.
The roundness data and mean roundness of individual
sample is given in Table 4. in various samples roundness of
grains ranges from very angular to well rounded. But in most
samples majority of the grains are subangular to subrounded.
The generalized grain roundness distribution based on
aggregate data of all the 36 samples is unimodal (Fig. 4).
The modal class of the aggregate distribution is subrounded
class. Mean roundness of individual samples range from 0.32
to 0.41 and for aggregate distribution the mean roundness is
0.36.
SPHERICITY
Sphericity of a particle might be defined as s/S
where s is the surface area of the sphere of the same volume
as the particle in question, and S is the actual surface area
of the particle.
Wadell (1935) proposed a sphericity index given by
the formula dn/Ds where dn, is the diameter of the sphere
with the same volume as the object and Ds is the diameter of
27
Table 5: Sphericity of detrital grains of Wadhwan
Surendranagar area
sandstones,
Sanple No
02 03 04 09 10 12 13 14 15 16 17 18 20 21 22 23 24 25 29 30 31 32 33 34 36 39 41 42 43 44 45 46 47 49 50 55
Total No. of grains
N
94 134 126 115 99 109 101 105 126 145 112 120 136 112 115 121 67 69 120 172 IIB 125 131 136 144 124 102 117 112 112 124 139 136 141 124 112
High >
No.
42 58 53 27 29 28 20 15 34 27 22 20 27 21 27 31 19 17 24 45 28 23 27 28 21 30 25 37 28 27 26 36 28 28 37 19
sphericity (0.9)
%
45 43 42 23 29 26 20 14 27 19 20 20 20 19 27 26 28 25 20 26 24 18 21 21 15 24 25 31 25 22 21 26 21 20 30 17
Low sphericity <(0.3)
No.
52 78 73 88 70 81 81 90 92 118 90 100 109 91 88 90 48 52 96 127 90 102 104 108 123 94 77 81 84 95 98 103 108 113 87 93
%
55 57 58 77 71 74 80 86 73 81 80 80 80 81 77 74 72 75 80 74 76 82 79 79 85 76 75 69 75 78 79 74 79 80 70 83
Mean sphericity
0.56 0.56 0.55 0.44 0.47 0.45 0.41 0.38 0.46 0.41 0.41 0.40 0.41 0.41 0.44 0.45 0.47 0.44 0.42 0.45 0.44 0.41 0.42 0.42 0.38 0.44 0.44 0.49 0.45 0.43 0.42 0.45 0.42 0.41 0.47 0.40
100. 28
80
60 c
Q- 40
V A = Very A n g u l a r
A = A n g u l a r
S A = S u b A n g u l a r
SR = S u b R o u n d e d
R = R o u n d e d
W : W e l l R o u n d e d
F i g . 4 : Composite histogram of grain roundness of the Wadhwan sandstones.
20
0 L VA SA SR WR
100
80
^ 60
(J
a. AO
20
Fig. 5:
Composite histogram of grain sphericity of the Wadhwan sandstones,
LOW HIGH
29
circumscribed sphere. All these methods of expressing
sphericity require measurements which can not be done on
sand grains.
In the present study, sphericity of the various
grains was classified as low and high as suggested by
Powers' (1953) comparison chart (Table 5). The mean
sphericity values of the grains in the studied sandstones
range from 0.38 to 0.56. The composite histogram shows that
majority of the grains are of low sphericity (Fig. 5). About
75% grains are of low sphericity and 25% grains are of high
sphericity.
TEXTURAL MATURITY
Texture of the sediments have two aspects:
(1) description of properties (grain size, shape etc) and
(2) integration of these properties into an assumed
sequential development, comprising the four stages of
textural maturity (Folk, 1980). According to this concept,
as sediments suffer a greater input of mechanical energy
through abrasive and sorting action of waves or currents,
they pass sequentially through the four stages, from
immature to submature, mature and supermature stage.
The sediment is texturally immature if it contains
over 5% terrigenous clay matrix and poorly sorted and
30
Tabla (i T*Ktaral BCtttrity of aandstonas, Madhwan formation (Lowar CraCacaoua), Suraadranaqar «z«a
Saai>l
Xo.
02 03 04 09 10 12 13 14 IS 1«
n 18 20 21 22 23 24 2S 29 30 31 32 33 34
3i 39 41 42 43 44 4S 4(
47 49 SO
ss
. " , < * >
l.JS 1 .so 1.7 1.» l.« 0.8S 1.93 1.66 1.4 1.6S l.S 1.8 1.5 1.4S 1.6 2.18 I.IS 1.7 2.OS 1.6 2.6S 1.66 2.48 1.98
1.86 1.16 1.26 1.6 1.81 1.86 1.48 2;i
3.08 1.S3 2.IS 1.7
Kaan alia
Kadlua Madlua Hadlua Hadluai MadluB Coaraa Hadlua MadiiiH Hadiua Hadiua Hadlua Hadiua Hadiua Nadlua Hadiua rinc Hedlua Hedlua rina Hadiua rina Hadiua Flna Hadiua
Hadiua Hadiua Hadiua Hadiua Hadiua Hadiua Hadiua rina
rina Hadiua rina Hadiua
Clay «
3.0
-2.0 1.0
-1.0 1.0 2.0 2.0 1.0 2.0 2.0 1.0 1.0 1.0 1.0 3.0 1.0 2.0 1.0 2.0
--2.0
2.0 1.0
-2.0 3.0 2.0 1.0 7.0
1.0 3.0 3.0 1.0
s<
1.13 0.72 1.01 0.89 1.0 1.05 0.93 0.80 0.76 1.0 0.79 0.9 1.11 1.04 0.99 0.91 1.16 1.21 0.9 1.05 0.96 0.89 0.77 0.67
1.09 0.78 0.93 0.84 1.12 0.86 0.92 0.62
0.84 0.83 1.1 1.S3
Sorting ^ Haan Noundnaaa of grain
TaHtural aaturlty
Poorly aortad Modarataly aortad Poorly aortad Hodarataly aortad Hodarataly aortad Poorly aortad Hodarataly aortad Hodarataly aortad Hodarataly aortad Hodarataly aorted Hodarataly aortad Hodarataly aortad Poorly aortad Poorly aortad Hodarataly aortad Hodarataly aortad Poorly aorted Poorly aortad Modarataly aortad Poorly aortad Hodarataly aorted Modarataly corted Modarataly aorted Hodarataly wall aortad Poorly aortad Hodarataly aortad Moderately aorted Hodarataly aorted Poorly aorted Moderately aorted Moderately aorted Moderately well aorted Moderately aorted Moderately aorted Poorly aorted Poorly aorted
0 0 0 0 0 0 0 0 0 0 0 0. 0 0. 0. 0. 0, 0. 0. 0. 0. 0. 0. 0.
0. 0. 0. 0. 0. 0. 0. 0.
0. 0. 0. 0.
.38
.37
.40
.38
.39
.37
.36
.41
.36
.34
.35
.33
.37
.35
.33
.38
.35
.35
.38
.38 38 .36 39 34
34 32 37 38 37 35 35 39
36 36 32 36
Subrounded Subroundad Subrounded Subrounded Subrounded Subrounded Subangular Subroundad Subangular Subangular Subangular Subangular Subrounded Subangular Subangular Subrounded Subangular Subangular Subroundad Subrounded Subrounded Subangular Subrounded Subangular
Subangular Subangular Subrounded Subrounded Subrounded Subangular Subangular Subroundad
Subangular Subangular Subangular Subangular
Subaatura Mature Subaatura Suboiatura Hatur* Subaatura Subaatura Subauiture Subaatura Suboiatura Subaatura Subaatura Subawture Subnature Subaatura SubaMtura Subaiature Subaatura Subaiature Subaature Subnature Mature Mature Subawtura
Subaatura Subaatura Mature Subaatura Subaatura Subaiature Subautura laaature
Subaature sufaaatoce Subaatura Subaatura
31
angular sand grains. In submature stage, sediments contain
under 5% clay but grains are poorly sorted and not well
rounded; while in mature stage sediments contain little or
no clay and sand grains are well sorted but not rounded. The
supermature stage of sediments contains well sorted and well
rounded sandgrains with no clay.
Out of a total 36 studied sandstone samples, 29
samples (80%) are submature, 6 samples (17%) are mature and
only one sample (3%) is immature (Table 6).
BIVARIANT PLOTS
To show the interrelationship of various textural
attributes, the bivariant plotswere used. Different textural
parameters were plotted against each other and their
relationship \i?as determined statistically by computing their
correlation coefficient values, following Karl Pearson's
correlation coefficient method:
r = Six y
E x X ^ y
A computer programe in Fortron 77 language was
developed using Vax-11/780 computing system.
The different plots which were used for the Wadhwan
sandstones included, mean size versus roundness, mean size
32
versus sphericity, mean size versus sorting, sorting versus
sphericity, and sorting versus roundness.
Mean Size Versus Roundness
For the study of the relationship between mean size
and roundness of the studied sandstones, 36 samples were
used and their mean size were plotted against their mean
roundness. The correlation coefficient determined for the
plot (0.19) shows a weak relation between the size and
roundness (Fig. 6A) . Roundness of the grains increases as
their size decreases.
Mean Size Versus Sphericity
The mean size versus sphericity diagram shows a
poor inverse relationship (Fig. 6B). This statement is
verified by the correlation coefficient value (-0.15)
determined for the plot. As the size of the grains
decreases, their sphericity increases.
Mean Size Versus Sorting
The mean size versus sorting plot of the studied
sandstones shows a very weak inverse relationship (Fig. 6C)
with a correlation coefficient of -0.16. The inverse
relationship suggests that sorting of the sand grains
increases with a decrease in their size.
33
3.0
0,30 0.35 0./.0 0 A 5 M E A N R O U N D N E S S INCREASES —
3 0
2 0
1 0
.« . * •
• • ^ • •
0 0 J I I L.
r = - 0 , 15
0.35
3.0
20
0.45 0.55 0.6 5 MEAN SPHCniCITV I N C R E A S E S »
. • a* .
10
00 L
r - - 0 IC
0 60 0.80 VO 1.2 SORTING ( ^ ) OF C R E A S E S - >•
"' l.>. VG
Fig. 6: Bivariant plots of different textural parameters of the Wadhwan sandstones (A-Mean size versus roundness, B-Mean size versus sphericity, C-Mean size versus sorting).
34
0.60
0.50
2 •* O.AO 3
0.35 0.60
• • • • • •
• • • • • o
• • • • • • • • • • •
0,80 1.0 1.2 SORT1NO(0) D E C R E A S E S >-
r - 0.A6
].i. 1.6
0.A5
O-AO
<
z 0.35
0.30
B
• %i • • •
• * • • •• • «• • •
• • • o
• • •
0.6 0
<•= - 0 . 1 2
.0.80 1.0 1.2 S O R T I N G [^ ) D E C R E A S E S »-
1.^ 1.6
Fig. 7: Bivariant plots of different textural parameters of the VJadhwan sandstones (A-sorting versus sphericity, B-sorting versus roundness).
35
Sphericity versus Sorting
Sphericity plotted against sorting and
correlation coefficient value for the plot (0.46) shows a
medium relationship between sorting and sphericity of the
Wadhwan sandstones (Fig. 7A). Sorting of the grain decreases
as their sphericity increases.
Roundness versus Sorting
The bivariant plot of roundness versus sorting has
a correlation coefficient value of -0.12 which shows weak
relationship between sorting and roundness (Fig. 7B ) Sorting
of the grain decreases as their roundness decreases.
It may be summarized that within the size range of
the Wadhwan sandstones, which is mainly medium sand, a
decrease in mean size is attended by an increase in
roundness and sphericity and a decrease in sorting. Whereas
a decrease in sorting is accompanied by a decrease in
roundness and an increase in sphericity.
GRAIN CONTACTS AND COMPACTION
Compaction may bring about crushing of soft
detrital grains, especially pelitic rock fragments resulting
in the formation of pseudomatrix. Thus, compaction may
modify the original framework composition of a sandstone and
36
present a problem in the interpretation of such a rock.
Therefore, a study of compaction of the Wadhwan sandstones
was also undertaken to evaluate the effect of diagenetic
processes on sandstone composition.
Compaction is a process of pore volume reduction in
sediments due to over burden load (Chilingarian/ 1983).
Compaction includes bgth mechanical as well as chemical
compaction (pressure solution).
Grain to grain contacts of sediments give an idea
about pore space reduction and compaction history of
sediment. Taylor (1950) classified the grain contacts as
floating, point, long, concavo-convex and sutured.
Grain contacts of the Wadhwan sandstones were
studied in 36 thin sections for determination of the
compactional history of the formation. Type of grain
contacts (Taylor 1950) were recognized and their pecentages
were detemined in diffrent samples (Table 7).
Ip various samples of the Wadhwan sandstones,
floating grains range from 2.0 to 21.0 percent and average
about 7.9% of the total grain contacts. High percentages of
floating grains in few samples are largely the result of
modification of texture by reaction between cement and
grains.
37
Table 7: Percentage of various types of grain to grain contacts,
Wadhwan sandstones
Sanple No.
02 03 04 09 10 12 13 14 15 16 17 18 20 21 22 23 24 25 29 30 31 32 33 34 36 39 41 42 43 44 45 46 47 49 50 55
Floating
9.0 4.0 4.0 3.0 7.0 4.0 6.0 9.0 4.0 3.0 19.0 5.0 6.0 3.0 9.0 2.0 3.0 14.0 16.0 7.0 8.0 4.0 12.0 11.0 4.0 3.0 11.0 12.0 7.0 6.0 18.0 14.0 7.0 9.0 3.0 21.0
Point contact
47.0 57.0 64.0 73.0 62.0 78.0 81.0 65.0 70.0 78.0 57.0 66.0 58.0 74.0 57.0 74.0 61.0 63.0 38.0 43.0 70.0 77.0 36.0 62.0 68.0 57.0 55.0 65.0 65.0 68.0 33.0 64.0 39.0 44.0 59.0 41.0
Long contact
35.0 34.0 23.0 18.0 25.0 13.0 9.0
23.0 19.0 15.0 18.0 20.0 33.0 17.0 26.0 18.0 28.0 12.0 38.0 42.0 14.0 13.0 42.0 22.0 22.0 31.0 22.0 15.0 23.0 21.0 33.0 15.0 47.0 39.0 30.0 27.0
Concavo-convex contact
4.0 2.0 3.0 2.0 2.0 2.0 2.0 1.0 3.0 2.0 3.0 3.0 1.0 2.0 2.0 3.0 2.0 4.0 3.0 1.0 3.0 2.0 3.0 1.0 2.0 1.0 3.0 2.0 2.0 2.0 3.0 2.0 2.0 4.0 2.0 2.0
Suture contact
5.0 3.0 6.0 4.0 4.0 3.0 2.0 2.0 4.0 2.0 3.0 6.0 2.0 4.0 6.0 3.0 6.0 7.0 5.0 7.0 5.0 4.0 7.0 4.0 4.0 8.0 9.0 6.0 3.0 3.0 13.0 5.0 5.0 4.0 6.0 9.0
38
Point contacts range from 33.0 to 81,0 percent and
average 60.25 percent (Fig. 8); while long contacts vary
betv^een 9.0 to 47.0 percent and average 24.50 percent.
Concavo-convex and sutured contacts are not very common. The
average percentages of sutured and concavo-convex contacts
are 4.90 percent and 2.3 percent respectively.
Taylor (1950) suggested that floating grains and
tangential (point) contacts represent original packing. The
long contacts may be the product of either original packing
or little pressure and precipitated cement. The concavo-
convex and sutured contacts are the result of overburden
pressure and compaction.
In the Wadhwan sandstones floating and point graih
contacts together form about 68.0 percent. Abundance of
these contacts suggests that little compaction has taken
place and original texture and packing are largely
preserved.
39
Fig. 8: Photoinicroyraph showing mostly grain to grain point contacts in the Wadhwan sandstones (X-90, crossed).
CHAPTER III
DETRITAL COMPOSITION OF THE WADHWAN SANDSTONES
Sandstones are mixtures of mineral grains and rock
fragments coming from disaggregated products of erosion of
rocks of all kinds. The processes determining mineral
composition of sandstones are more complex than simple mining
ones from source areas of different kinds.
Minerals may be lost or modified by weathering in
source area, by transportation to site of sedimentation and
by diagenesis.
Mineralogy of a sandstone is the derived product from
the source area as modified by sedimentary processes. A
mineraological examination is one of the most practical
studies that can be made to obtain information on provenance,
including tectonism and climate, effect of transportation
including distance and direction and addition of chemically
deposited minerals during sedimentation and diagenesis.
METHODOLOGY
Detrital composition of the Wadhwan sandstones was
evaluated both quantitatively and qualitatively in 36 thin
sections. About 200-300 grains per thin section were counted
for quantitative analysis and for determining the modal
composition of rocks under investigation.
41
Terminology proposed by Folk (1980) was followed for
identifying and describing the detrital grains of the
sandstones.
FRAMEWORK GRAINS
The sandstones of the Wadhwan Formation are composed
of mainly quartz of several varieties followed by micas,
rock fragments, feldspars and heavy minerals as minor
constituents. The average composition of the sandstones is:
quartz, 98.24%; rock fragments, 1.0%; feldspars, 0.19%; and
other minor constituents (mica and heavy minerals etc),
0.57% (Table 8) .
Quartz
Quartz is the dominant framework constituent of the
sandstones, forming on an average of about 98.24% of the
rocks. On the basis of Folk's (1980) classification the
various types of quartz recognized include common quartz,
vein quartz, recrystallized metamorphic quartz and stretched
metamorphic quartz. The average percentages of various types
of quartz are: common quartz, 88.62%; vein quartz, 3.96%;
recrystallized metamorphic quartz, 4.25%; stretched
metamorphic quartz 3.15%.
Common Quartz
The common quartz occurs as subequant and mostly
subangular to subrounded grains. The grains are
42
Table 8: Percentages of detrital minerals in the Wadhwan Sandstones
Sample No.
02 03 04 09 10 12 13 14 15 16 17 18 20 21 22 23 24 25 29 30 31 32 33 34 36 39 41 42 43 44 45 46 47 49 50 55
Quartz-tall
Common quar
92 94 89 84 80 77 82 78 78 86 86 87 96 81 95 90 80 87 94 92 94 89 93 86 92 74 86 83 83 96 85 85 92 93 91 90
tz
Monocrys-ine Vein quartz
2 2 1 5 6 7 8 5 6 6 4 4 1 3 1 5 9 2 1 1 2 2 1 6 4 6 6 8 '8
-3 6 -
1 1 2
Quartz-tall
Recrysta-llized metamor-phic quartz
3 2 6 5 8 9 3 5 5 5 7 4 2 8 2 3 6 7 1 3 3 3 2 4 2 9 4 4 5 2 4 3 2 1 5 4
•Polycrys-ine Stretched metamor-phic quartz
1 1 1 5 4 6 4 10 8 2 3 3 1 7 1 1 5 2 2 2 — 3 1 3 1 9 3 3 3 -
4 2 2 2 3 2
MicQ
—
-----------------
1 --1 1 --— -
1 --
1 1 ---
1
Feldspar
_
----—
1 — --— -— — -— --— -— -— --
2 1 — --
1 -
2 — -
-
Rock fragment
1 -
2 -
2 1 1 2 3 1 -2 —
1 1 1 — — — 1 1 2 1 1 1 _ -
1 1 2 1 1 2 2 -
1
Heavy mineral
1 1 1 1 -—
1 — ----— — -— — 2 1 1 — -
1 .r»
-w
-— -—
1 2 —
1 -
—
43
monocrystalline with clear appearance having few inclusions
of tourmaline, mica and opaques. It forms 74.0 to 96.0%
(average 87.2%) by volume in different samples.
Vein quartz
It consists of 1.0 to 9.0% (average 3.9%) of the
detrital fraction. It occurs in the form of monocrystalline
grains. These grains have abundant vacuoles imparting a
cloudy appearance.
Recrystallized Metamorphic Quartz
It occurs in the form of polycrystalline grains of
fine to coarse size and equant to sub-equant shape. The
grains are made up of a mosaic of microcrystalline to fine
grained subindividuals (Fig. 9). It comprises 1.0 to 9.0%
(average 4.19%) of the total detrital constituents of the
Wadhwan sandstones.
Stretched metamorphic quartz
It occurs as polycrystalline grains which are mostly
made up of elongated and lensoid subindividuals of micro-
quartz and fine grained quartz. The subindividuals have
subparallel to almost parallel orientation with sutured
boundaries and show highly undulose extinction (Fig. 10). It
constitutes generally 1.0 to 10.0% (average 3.1%) of
detrital fraction.
44
Fig. 9: Photomicrograph of a typical recrystallized metamorphic quartz grain in the Wadhwan sandstones showing mostly equant subindividuals (X-90, crossed).
Fig. 10: Photomicrograph of a typical I stretched metamorphic quartz
grain in the Wadhwan sandstones showing elongated subindividuals (X-90, crossed).
45
Mica
Both muscovite and biotite occur as tiny flakes. The
percentage of mica is very low in the Wadhwan sandstones,
averaging about 0.19% of the detrital constituents. However,
muscovite is more common than biotite. ' ~
Feldspars
In the studied sandstones feldspars are not common.
They are present only in some samples and constitute 1.0 to
2.0% of the detrital component averaging 0.19%. The feldspar
grains belong to mainly orthoclase. The grains are
weathered. Kaolinite is common in the Wadhwan sandstones and
possibly formed by the weathering of feldspars grains.
Rock Fragments
In the Wadhwan sandstones rock fragments are present
in almost all the samples except few of them. The rock
fragments comprise 1.0 to 3.0% and average 1.0%. Both
sedimentary and metamorphic rock fragments occur in the
studied sandstones. Sedimentary rock fragments include
mainly chert (Fig. 11) and some siltstone. Low rank
metamorphic rock fragments include phyllite and quartzite
fragments.
Fig. H : Photomicrograph of typical chert grains in the Wadhwan sandstones, Chert has recrystallized to microcrystalline quartz (X-90, crossed).
Fig. 12: Photomicrograph of a pleochroic tourmaline grain in the VJadhwan sandstones (X-90, uncrossed).
47
Heavy Minerals
Heavy minerals were observed in about one third of
the total samples. Heavy minerals constitute 1.0 to 2.0% and
average 0.31%. Opaques, tourmaline (Fig. 12) and zircon are
the main types of heavy minerals.
Clay Matrix
Percentages of clay in the Wadhwan sandstones
generally range from. 1.0 to 7.0 percent/ and average about
1.6 percent.
The clay minerals in sandstones can originate either
as detrital particles brought into the basin of deposition
as a result of erosion and redistribution of rocks or by
insitu alteration of unstable grains such as feldspars,
micas etc. or deposited from solution in intergranular pores
of sediments during diagenesis as an interstitial cement.
In the Wadhwan sandstones both allogenic and
authigenic clays are present. The authigenic kaolinite is
dominant and shows well' L developed crystalline habit and
book form as is clearly seen in SEM photographs (Fig. 13)
which distinguish it from allogenic clay. The allogenic
kaolinite shows irregular aggregates of plates which have
rugged outlines (Fig. 14).
48
Fig. 13: Scanning electron micrograph of the Wadhwan sandstone showing well-developed hexagonal plates of authigenic kaolinite arranged in vermicular form.
Fig. 14; Scanning electron micrograph of the Wadhwan sandstones showing irregular aggregates of allogenic kaolinite with rugged plate outlines. Incipient silica overgrovv ths are seen on quartz grain surface.
49
CEMENTS (AUTHIGEHIC)
In the Wadhwan sandstones three types of cementing
materials occur which include iron oxide/ silica and
calcite, in order of abundance.
Iron oxide
In the Wadhwan sandstones iron oxide is most
abundant cementing material which forms 2.0 to 25.0%
(average 6.5%) by volume of the rocks (Table 9).
Iron oxide cement occurs in the form of a thin
coating around detrital grains as well as patches which
show corrosion of detrital grains and replacement along
fractures (Fig. 15). Corroded quartz grains suggest the
presence of an earlier calcite cement which was replaced by
iron oxide. In some thin sections oversized pore spaces are
seen to be lined with a thin coating of iron oxide (Pig»
16).
The ove^fsized pore spaces have resulted from
destruction and leaching of labile framework grains,
possibly feldspars.
Iron oxide cement was possibly derived from
weathering and leaching of the overlying traps. The thin
iron oxide coating on detrital grains is possibly inherited
from the source rocks.
50
Table 9: Percentages of detrital grains, clay, cements and
spaces of the Wadhwan sandstones Void
Sampl-e No
02 03 04 09 10 12 13 14 15 16 17 18 20 21 22 23 24 25 29 30 31 32 33 34 36 39 41 42 43 44 45 46 47 49 50 55
Detrital grain
77 83 83 73 82 87 86 86 78 85 87 86 77 81 76 61 83 84 80 84 69 79 83 f2 ly) wf 0^ ' 82 80 72 81 87 64 80 79 80
Clay
3 -2 1
1 1 2 2 1 2 2 1 1 1 1 3 1 2 1 2 -• 2 2 1 «• 2 2 2 1 7 1 3 2 1
Iron Oxide Cement
4 6 6
11 7 2 3 2 5 4 7 5 8 6 9 6 7 5 4 5
15 10 9 8 8 4 f 3 S -8 -25 6 8 9
Silica Cement
2 2 1 2 2 1 2 2 1 2 1 1 1 2 1 2 2 3 2 1 4 2 1 4 1 2 2 2 1 3 2 2 3 1 2 —
Carbonate Cement
__ ---
^
-------— ----------mm
--* — 21 -----2
Void Space
14 9 8
13 9 9 8 8
14 8 3 6
13 10 13 10 5 7
12 9
10 9 7 4 9 7 5
11 12 2 8 4 7
10 9 8
51
Fig, 15: Photomicrograph of the Wadhwan sandstones showing iron oxide cement filling up intergranular spaces and fractures within the detrital quartz grains (X-90, uncrossed).
Fig. 16: Photomicrograph of the Wadhwan sandstone showing oversized pore spaces lined with iron oxide cement (X-90, uncrossed).
52
Silica cement
Silica cement in the studied sandstones generally
ranges from 1.0 to 4.0% and averages about 1.86 percent. In
most of the samples silica cement occurs in the form of
quartz overgrowths. The authigenic quartz overgrowths on
detrital quartz grains are seen and observed to partially
fillup the intergranular spaces. SEM micrographs of quartz
grain surfaces show incipient silica overgrowth (Figs. 13
and 14) .
Carbonate cement
Calcite cement occurs in few samples of the Wadhwan
Formation. These are generally white coloured sandstones. In
thin section calcite cement show patchy distribution and
ranges in percentage from 2.0 to 21.0 and averages about
0.63%.
The calcite cement has partially replaced detrital
grains which are marked by corroded boundaries (Fig. 17).
The replacement cementation implies chemical instability of
quartz grains and slow rate of cementation resulting in
solution of the silica grains (Dapples, 1971).
FACTORS CONTROLLING THE DETRITAL MINERALOGY OF THE WADHWAN
SANDSTONES
Detrital mineralogy does not depend only on a single
factor but a group of factors are responsible for detrital
53
Fig. 17: Photomicrograph of the Wadhwan sandstone showing rare carbonate cement which has corroded detrital quartz grains {X-90, crossed).
54
composition of a sandstone which include the types of source
rocks, distance of transport , tectonism, palaeoclimate/
palaeogeography and depositional environments and diagenetic
modifications of the original detrital constituents.
Identification of the Source Area
In order to interprete the detrital mineralogy of a
sandstone in terms of the provenance/ one has to find out
where and at what distance was the source area* located and
what was its relation to the configuration and bathymetry of
the depositional basin. In other words we have to
reconstruct the palaeogeography of the time period during
the deposition of a particular sandstone formation. For
this we need to ascertain the paleoslope, paleocurrent
system operative during the depositional process and the
facies distribution.
The Cretaceous rocks of Saurashtra including the
Wadhwan sandstones were deposited in a failed rift and a
schematic model of its tectonic setting and broad
paleogeography have been reconstructed by Casshyap and Aslam
(1992). The commencement of Cretaceous sedimentation in the
Saurashtra rift was marked by the deposition of shoreline
conglomerate and interbeded sandstone and shale around
Himatnagar near Aravalli highlands (Casshyap et al 1983).
The study area lies about 150 kilometer southwest of
Himatnagar. Towards southwest sedimentation continued in the
55
subsiding distal parts of the rift. A considerably thick
clastic sequence was deposited within the rift which shows
an increasing proportion of fine clastic to the southwest
along the length of the basin.
The paleogeographic reconstruction of the Saurashtra
rift suggests that the provenance of the Wadhwan sandstones
was located towards the northeast, in the Aravalli highlands
a few hundred kilometers from the study area.
Source Rock Composition
Each type of source rock tends to yield a
distinctive suite of minerals which constitute a guide to
the character of that rock. Both light and heavy minerals
of a sandstone are important in the study of provenance.
The quartz isand is the main product of rock
disintegration and decomposition and is the dominant
constituent of most sands. A number of attempts have been
made to utilize quartz as a guide to the provenance. Among
the earlier notable attempts Krynine'-s (1946) approach is
based on grain shape, character of the inclusions and
extinction. It v/as presumed that a discrimination between
igneous (plutonic) and .metamorphic origins of common
monocrystalline quartz could be made based on inclusions,
shape and extinction (undulatory or not). But these critaria
56
are usually difficult to apply (Bokman, 1952). Quartz of
source rocks shows that difference in inclusions, shape and
extinction either do not exist or there is a wide range of
variation.
Many workers have emphasized the usefulness of
polycrystalline or composite quartz that is those grains
which are composed of more than one crystal unit (Blatt and
Christie, 1963; Conolly 1965; Voll, 1960). Polycrystalline
quartz showing tv/o distinctly different sizes of crystals
v;ithin a single grain is diagonastic of metamorphic quartz.
High ratio of polycrystalline quartz to total quartz also
suggests a metamorphic source. Voll (1960) has noted that
polycrystalline quartz of metamorphic origin is of two
types: (1) polygonized quartz in which component grains form
polygonal units, with straight boundaries which tend to meet
at 120 degree angles; and (2) polycrystalline quartz which
exhibit sutured boundaries.
Feldspar is the second most common mineral of sand.
Based on zoning, intergrowth habits, twining, fracturing
etc. the feldspars are defined into nine classes. Type of
zoning or/and lack of zoning may be clues to the provenance
of the feldspar (Pittnan, 1963). "Ehe plagioclase in volcanic
and hypabyssal rocks is characterized by oscillatory zoning,
v here as this type of zoning is rare in plutonic igneous and
57
metamorphic rocks. Zoned plavioclase is strongly Indicative
of an igneous rock.
Feldspars are very sensitive to the v/eathering
processes which require not only suitable climate but also a
proper length of tine. The duration of time through which
processes of decomposition act is determined by relief. The
presence or absence of feldspar is therefore the result of
the balance between the rate of erosion and decomposition.
Detrital feldspar is therefore an index of both climatic
vigor and tectonism.
The micas are never a major constituent of
sandstone. They are derived from schists and gneisses, from
plutonic igneous rocks and from volcanic sources. Muscovite
is more common in sand than biotite, because of its greater
stability. In general, abundant mica suggests a metamorphic
provenance for the sand.
Besides the quartz and feldspa?", sandstones commonly
contain rock fragments. These may be volcanic, or be
sedimentary mainly pelitic particles and also be
metamorphic such as slate, phylite and mica schists.
The heavy minerals of sandstone have long been used
as indices of provenance and that certain species are i I
characteristics of certain source rocks is a well
established conclusion (Folk, 1980).
58
The Wadhwan sandstones consist of igneous quartz
(common quartz, vein quartz), metamorphic quartz
(recrystallized metamorphic quartz, stretched metamorphic
quartz), micas and rock fragments.
The common quartz is dominant in the Wadhwan
sandstones. Common quartz is derived mainly from granite
batholith or granite-gneisses. Vein quartz, recrystallized
metamorphic quartz and stretched metamorphic quartz occur in
low percentages in the Wadhwan sandstones. Vein quartz in
the Wadhwan sandstones suggests derivation from pegmatites,
hydrothermal and rarely sedimentary vein fillings.
Recrystallized metamorphic quartz indicates origin from
recrystallized metaquartzite, highly metamorphosed granite and
gneissic rocks. Stretched metamorphic quartz of the studied
sediments is probably derived from granites, schists or
quartz veins.
Mica in the Wadhwan sandstones include mainly
muscovite and few biotite grains which might have been
derived frpm granites, pegmatite or schists.
Rarity of feldspar and very small amounts of rock
fragments in the Wadhwan sandstones indicate prolonged
abrasion or high intensity of weathering in the source area.
To the north and northeast of Himatnagar, where
Cretaceous sedimentation began in the Saurashtra rift,
59
Precambrian rocks of Delhi and Aravalli Supergroup outcrop.
Around Himatnagar the Cretaceous sedimentary rocks rest on
the Precambrian basement with a pronounced unconformity.
The Precambrian rocks identified as the provenance of
/7adhwan sandstones consist of mainly quartzites and
ohyllites which have been intruded by the Idar granite. Thus
on the basis of present day distribution of Precambrian
rock types in combination with detrital mineralogy of the
sandstones it may be concluded that most of the Cretaceous
sediment was derived from metasedimentary rocks and granites
and granite-gneisses.
Tectonism
The effect of tectonism on detrital mineralogy of
the Wadhwan sandstones has been discussed in detail in the
following chapter of this dissertation which deals with
petrofacies and plate tectonic setting of the sandstones.
Distance of Transport
The residues produced by disintegration and
decomposition of source rocks are subjected to further
changes during their transport from the place of release
from a source rock to the place of their ultimate
deposition. The processes operative during transport not
only bring about rounding of the detritus but also modify
60
the composition by selective abrasion. Downstream changes in
composition of river gravels have long been noted. Gravels
can become compositionally mature in a relatively short
distance of travel by rapid elimination of less durable
components v ith resulting enrichment in more stable rock
types.
On the other hand, evidence concerning the selective
wear and elimination of minerals in sand range is some what
ambiguous. Large streams show few or no changes in mineral
composition even during prolonged transport and feable
changes that do occur are not the result of differential
abrasion (Russell, 1939). There appears to be only a small
loss of feldspar relative to quartz and no appreciable loss
of other relatively soft and cleavable minerals. However,
other VN orkers have shown that there is an appreciable loss
of feldspar in comparatively short distance in high gradient
gravel-carrying streams (Plumblay, 1948).
The detrital grains of the Wadhwan sandstones are in
the sand size range and in all probability they have
undergone transportation for a distance of a few hundred
kilometers. The Wadhwan sandstones are deficient in
feldspars and one possible reason for this deficiency may be
the transportation of sediment by high gradient streams and
rapid destruction of feldspars by abrasion. Since deposition
61
of the Wadhwan sandstones took place in a tectonically
active rift, presence of high gradient stream is quite
likely within the basin. However this premise does not stand
to scrutiny because rock fragments which could have been
destroyed more easily are more common than the feldspars.
Therefore some factor other than transportation was
responsible for the paucity of feldspars in the Wadhwan
sandstones.
Palaeoclimate
Climate is an important factor that controls the
detrital mineralogy of clastic rocks because the type of
weathering is dependent on climate. Under tropical
conditions where temperature is high and moisture is most
abundant, weathering appears to be most intense. Most
feldspars and labile constituents are destroyed and
sediments become enriched in quartz which is the only
chemically and physically durable mineral. Whereas colder or
more arid climates are marked by products of lesser
maturity. The general absence of water tends to retard
chemical action.
Palaeoclimate of the Cretaceous period was studied
by different workers who selected different parameters for
palaeoclimate reconstruction. Among the various parameters,
the latitudinal position is considered as the most important
62
factor. The palaeogeographic reconstruction of the earth at
100 m.y. (Thompson and Barron, 1981) suggests that during
the Lower Cretaceous the study area was located at latitude
44° south of the equator and within the wide humid tropical
belt with luxuriant plant life that extended upto 45° north
and south of the equator. Therefore the Precambrian basement
rocks which provided sediments to the Saurashtra rift must
have undergone rigorous weathering under humid tropical
conditions resulting in destruction of much of the feldspars
and labile constituents. Palaeoclimate was possibly a very
important factor in the formation of highly quartzose
sandstones of the Wadhwan Formation. Akhtar and Ahmad (1991)
have demonstrated the active role played by tropical climate
in the deposition of quartz rich Nimar Sandstone which is
believed to be equivalent in age to the Wadhwan Formation.
Depositional Environments
The Lower Cretaceous rocks of the Saurashtra rift
basin represent deposits of a general tansgression
proceeding' from SW to NE consequent upon progressive
downwarping with intermittent rifting of the basin. A large
part of the lithofacies of the riftrfill represents
deposition in the nearshore coastal delta plain with a
gradual northeastward transgression recognized by the facies
changes from the basal deposits to the upper most Wadhwan
63
Formation. The Wadhwan Formation represents localized
deposition in estuaries and embayments as part of continuing
marine transgression. The highlands to the east and
northeast supplied the clastic sediments into the estuarine
environment. Deposits of shoals and sand bars are
represented by the associated pebbly coarse sand.
Depositional reworking effects the relative
abundance of detrital grains in terrigenous sediments
(Suttner, 1974). The most effective modification of
sandstone composition may take place in those environments
where rates of erosion and sedimentation are low. A long
residence time at the sediment water interface of shallow
marine environments enhances the destruction " of labile
detrital grains (Suttner et al. 1981). The sandstones of
Wadhwan Formation which are mostly texturally submature
might have been deposited in rather protected environments
of estuaries and embayments. Therefore, it seems that
depositional reworking has not been very effective in
controlling the detrital composition of the Wadhwan
sandstones which show a very high degree of compositional
maturity but lack the same degree of textural maturity.
Diagenetic Modifications
The depositional composition of sands may be altered
by diagenetic processes which must be taken into
64
consideration while making provenance interpretation
(McBride, 1985). The modifying diagenetic processes operate
from the zone of weathering to the deep subsurface where
diagenesis grades into metarraorphism. Many authors including
Blatt, 1966; Fuchtbauer, 1967, 1974; Nagtegall, 1978;
Chilingarian, 1983; McBride, 1985; and Akhtar at al, 1992
have studied the diagenetic processes and their effects on
modification of detrital composition. The diagenetic
modifications include loss of detrital framework grains by
dissolution, alteration of grains by replacement or
recrystallization, and the loss of identity of certain
ductile grains during compaction which give rise to
pseudomatrix.
The presence of highly weathered feldspar grains
as~well-as oversize pores indicate dissolution of detrital
grains in the Wadhwan sandstones. I have estimated that
about 2% of the existing porosity of the Wadhwan sandstones
has resulted from dissolution of detrital grains, mainly
feldspars.. The process of replacement has not been very
effective in modifying the detrital composition of the
Wadhwan sandstones. The replacement of quartz grain by
carbonate and iron oxide is only partial and localized and
hence composition of the original grain is determinable.
Therefore this factor has not been much of a problem in
65
provenance interpretation of the Wadhwan sandstones. A study
of grain contacts of the Wadhwan sandstones, as described
under chapter II indicates that the sandstones have not
suffered much compaction during burial and their original
texture and fabric has not been modified to any appreciable
extent by the process of compaction.
CHAPTER IV
PETROFACIES AND PROVENANCE INTERPRETATION
The word "Provenance" has been derived from French
word 'provenier' and Latin word 'Proveniens' meaning origin
or place where produced. In sedimentary petrology provenance
refers to the identify and composition of source rocks,
relief and climate in source area, and to some extent
includes transportation factors (Suttner, 1974). During the
last two decades sedimentologist v/orking on problems of
detrital composition and provenance of sedimentary rocks
have increasingly realised that the key relations between
provenance and basin are governed by plate tectonics, which
thus ultimately controls the distribution of different types
of sandstone (Dickinson and Suczek, 1979). The studies
attempting to interprete detrital modes of sandstones to
plate tectonic settings have led to the recognition and
discription of "Petrofacies" in sedimentary sequences. The
term 'petrofacies is employed for those facies which can be
distinguished principally by their composition and
appearance.
Krynine (1942) interpreted mineral composition in
terms of the geosynclinal cycles, which effected rates of
the source area uplift and basin subsidence and controlled
the geological composition of source terranes. Middleton
(1960) similarly concluded by using chemical composition of
67
sandstones. Many ideas and conclusions of Krynine and
Middleton have been adapted to plate tectonic theory.
To interpret detrital mineral and chemical
composition in terms of plate tectonism, attempts were made
by several workers, which included Dickinson (1970; 1985),
Dickinson and Rich (1972), Crook (1974), Schwab (1975),
Dickinson and Suczek (1979), Valloni and Maynard (1981).
Petrofacies studies help in interpreting the
tectonic setting for ancient detrital sequences. The
appearance of a particular mineral assemblage may indicate
an important tectonic event such as uplift and erosion of
an arc, plutonic suite or an ophiolites assemblages along a
suture and this may help to date the time of intrusion or of
continental collision (Ingersoll, 1978; Eisbacher, 1981;
Schwab, 1981).
The use of quantitative detrital modes, calculated
from point counts of thin section, to infer sandstone
provenance is now well established (Dickinson, 1985). The
detrital modes of sandstone primarily reflect the different
tectonic setting of the provenance but various other factors
which effect sandstone composition are relief, climate,
transport mechanism, depositional environment and diagenetic
change. Diagenetic changes are also secondary importrant
68
factor which modify sandstones composition (Akhtar et al.
1992) .
In the present investigation, the detrital minerals
of the Wadhwan sandstones have been studied for the purpose
of petrographic classification of the sandstones and inter
pretation of their provenance and plate tectonic setting.
The classification of sandstone is a shorthand
method of summarising important discriptive and/genetic
features of a particular rock. Sandstone classification has
been attempted by several authors. These classifications
have been reviewed by Klein (1963), McBride (1963), Okada
(1971) and Pettijohn et al (1972).
Folk's (1980) classification based on the
composition of detrital framework constituents is most
commonly used classification for the description and
comparison of sandstones. This classification was used in
the present study of the Wadhwan sandstones for a meaningful
comparison with other sandstones. The detrital framework
grains were grouped into three end members.
(i) all types of quartz including metaquartzite
(ii) all single feldspar grains plus granite and gneiss
fragments.
(iii) all other rock fragments (chert, slate, phyllite,
schist, volcanics, limestone,sandstone, shale).
69
Q
Quar t z a r e n i f e
F i g . 18 : C l a s s i f i c a t i o n of t h e V7adhv/an sands tones (According t o t h e scheme of Folk, 1980) .
70
The average composition of the framework grains of
the Wadhwan sandstones is 98.8% quartz, 1.0% rock fragments,
0.19 feldspar and other constituents. All the 36 sample
points plotted on the Folk's (1980) classification triangle
fall in the quartzrich end member designated Quartz arenite
(Fig. 18).
PETROFACIES
The classification based on Dickinson's (1985)
scheme puts emphasis on tectonic setting of the provenance
which primarily controls the sandstone composition. The
other secondary factors (relief, climate, transport
mechanism, depositional environment, diagenesis) also play
their roles in determining sandstone composition. The roles
of these factors in influencing the detrital composition
of the Wadhwan sandstones have been discussed earlier in
chapter III of this dissertation.
In accordance with Dickinson's (1985) scheme the
detrital modes of the Wadhwan sandstones were identified and
recalculated to 100 percent as the sum of Qm, Qp, P,K, Lv
and Ls (Table 10). The sandstones donot contain intrabsinal
grains ( Zuf f i, 1980).
71
Table 10: Classification and symbols of grain types (after
Dickinson 1985)
A. Quartzose Grain (Qt = Qm + Qp)
Qt = Total quartz grain
Qm = Monocrystalline quartz
Qp = Polycrystalline quartz
B. Feldspar Grain (F = P + K)
F = Total feldspar grains
P = Plagioclase grains
K = K-Feldspar grains
C. Unstable lithic fragments (L = Lv + Ls)
L = Total unstable lithic fragments
Lv = Volcanic/metavolcanic lithic fragments
Ls = Sedimentary/metasedimentarylithic fragments
D. Total lithic fragments (Lt = L + Qp)
Le = Extrabasinal detrital lime clasts
(not included in L or Lt)
Two complementary triangular diagrams (Fig.l9A/B)/
each of which involves a different set of grain populations,
were employed for the analysis of the data on detrital modes
of the Wadhwan sandstones. These diagrams i.e. Qt-F-L and
RECYCLED OROGEN PROVENANCES
CONTINENTAL BLOCK PROVENANCES WITH SOURCES ON STABLE CRATONS
(C) AND IN UPLIFTED BASEMENT(B)
DECREASING MATURITY OR STABILITY
INCREASING RATIO OF OCEANIC TO COTINENTAL MATERIALS
72
CONTINENTAL BLOCK PROVENANCE
MERGER OF FIELDS FOR MATURE ROCKS WITH STABLE FRAME WORKS
RECYCLED OROGEN PROVENANCES
INCREASING RATIO OF CHERT TO QUARTZ
MERGER OF FIELDS FOR BASEMENT AND ARC / INCREASING RATIO ROOTS / OF PLUTON(C(PJ TO
Fig . 19: Classificaticxi of the VJacahv/an sandstone (Based on the Gcherr? of Dickincon, 1985).
73
Qm-F-Lt plots, presented by Dickinson (1985) represent
actual reported distribution of mean detrital modes for
sandstone suites derived from different types of provenances
plotted on standard triangular diagrams. The two diagrams
both show full grain population, but with different
emphasis. The Qt-F-L plot where all quartzose grains are
plotted together puts emphasis on grain stability, and thus
on weathering, provenance, relief, and transport mechanism
as-well-as source rocks. In the Qm-F-Lt plot where all
lithic fragments are grouped together, the emphasis is
shifted toward the grain size of the source rock, because
finer grain rocks yield more lithic fragments in the sand
size range (Dickinson and Suczek, 1979).
Detrital modes of the Wadhwan sandstones calculated
according to Dickinson's (1985) classification scheme are
described below and their percentages are shown in Table 11.
Qm(monocrystalline quartz) is the dominant detrital
mode and form 79 to 98 percent in various samples,
averaging 91.6 percent. Qm grains are mostly subrounded.
Qp (polycrystalline quartz) includes recrystallized
metamorphic quartz and stretched" metamorphic quartz. Qp
ranges from 2.0 to 21.0 percent in various samples,
averaging 7.1 percent.
74
Table 11: Percentage of framework modes of the Wadhwan
sandstones (based on the classification scheme- of
Dickinson, 1985)
Sample IIo.
02 03 04 09 10 12 13 14 15 16 17 18 20 21 22 23 24 25 29 30 31 32 33 34 36 39 41 42 43 44 45 46 47 49 50 55
Qt
99 100 98 100 98 99 98 98 97 99
100 98 100 99 99 99
100 100 100 99 99 98 99 99 99 98 99 99 99 98 98 99 96 98
100 99
F
0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 1 0 0 0 1 0 2 0 0 0
L
1 0 2 0 2 1 1 2 3 1 0 2 0 1 1 1 0 0 0 1 1 2 1 1 1 0 0 1 1 2 1 1 2 2 0 1
Qm
95 98 91 90 86 84 91 83 83 93 90 90 97 84 96 96 89 89 97 95 96 91 97 93 96 77 92 92 92 96 90 95 93 95 92 94
F
0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 1 0 0 0 1 0 2 0 0 0
Lt
5 2 9
IS) 14 16 8
17 17 7
10 10 3
16 4 4
11 11 3 5 4 9 3 7 4 21 7 8 8 4 9 5 5 5 8 6
75
K-feldspar grains are not conunon in the Wadhwan
sandstones and were observed in very fevi? samples. The.
feldspar grains consist of weathered orthoclase and their
percentages range from 1.0 to 2.0 percent in the few
samples in which the grains occur. The feldspar grains
average about 0.19%.
Ls (rock fragments) comprises 1.0 to 3.0 percent of
the detrital fraction. They include metasedimentary/
sedimentary lithic fragments of phyllite, quartzite, chert/
sandstone and siltstone etc.
PLATE TECTONIC SETTING
On the standard Qt-F-L plot, the studied samples lie
in the continental block provenances with sources on stable
cratons because most of the points fall near the Qt pole
(Fig. 19A). On the Qm-F-Lt plot most points lie in the
transition zone between the fields of continental block
provenances and recycled orogen provenances. The points are
mostly located on the Qm-Lt leg of the triangular diagram
(Fig. 19B).
The continental blocks are tectonically consolidated
regions which represent amalgamated ancient erogenic belts
that have been eroded to their deep seated roots and lack
any relict genetic relief (Dickinson, 1985). Detritus from
76
nonorogenic continental block forms a spectrum of sand types
derived from the broad positive areas of stable cratons at
one extreme and from locally uplifted, commonly fault-
bounded basement block at the other extreme.
The petrofacies analysis of the Wadhwan sandstones
suggest their sources on stable craton (Fig. 19A). The main
sources for craton-derived quartzose sands are low-lying
granitic and gneissic exposures, supplemented by recycling
of associated flat lying platform sediments. It has been
mentioned elsewhere that the source rocks of the Wadhwan
sandstones, located northeast of the study area, consisted
of Precambrian metasediments and granite-gneisses of Delhi
and Aravalli Supergroup.
The location of the study area within a humid
tropical belt during the lower Cretaceous (Thompson and
Barron,1981) and the prevailing warm and humid climate must
have affected the weathering pattern of the source rocks. An
intense chemical weathering possibly destroyed most
feldspars and labile constituents. Therefore the continental
block provenance that provided detritus to the study area
during the deposition of the Wadhwan sandstones was deeply
weathered.
The formation of mature quartzose sands/ such as
those of the Wadhwan sandstones, have been ascribed to
77
multicyclic reworking on cratons by several workers. However
recent work has shown conclusively that quartzose sand is
also being produced as first-cycle sediment from deeply
weathered granite and gneissic bed rock exposed in tropical
low lands of the modern Amazon basin (Franzinelli and
Potter, 1983). In view of the intense and deep weathering
envisaged for the source rocks of the Wadhwan sandstones/
recycling was perhaps not an important factor in the
formation of quartzrich Wadhwan sandstones.
The development of first cycle quartzrich sand
requires low relief in the provenance to allow prolonged
weathering. This is demonstrated by quartz-poor nature of
both fluvial and littoral Holocene sands derived from
drainage basins in tropical highlands with high relief
(Ruxton, 1970). Thus, even where the climatic potential for
intense weathering exist, quartz rich sands will not be
produced unless the relief is low. It follows therefore that
a low relief marked the continental block provenance from
where the Wadhwan sandstones were derived.
A large majority of the Wadhwan sandstones are
texturally submature, that is, they contain under 5% clay
but detrital grains are poorly sorted and not well rounded.
This indicates that the Wadhwan sandstones were mostly
deposited in environments rather protected^£^lSHF^S*=at^tence
~Dsa.zLv3 \\-^'
78
wave and current action. This seems quite likely as the
Wadhwan Formation represents localised deposition in
estuaries and embayments (Casshyap and Aslam, 1992). The
waves and currents had sufficient strength to winnow away
the mud, but were not strong enough to bring about sorting
and rounding of the detrital grains.
The detrital grains of the Wadhwan sandstones are in
the sand-size range and are believed to be transported from
a distance of a few hundred kilometers, considering the
location of the Aravalli highlands with respect to the study
area. This distance of transportation is not sufficient to
bring about rounding and sorting of detrital grains within
the sandsize range exhibited by the Wadhwan sandstones.
It is now a well established fact that the lower
Cretaceous sedimentary rocks of Saurashtra were deposited in
faulted troughs (Biswas, 1982). A recent study of these
sediments, specially their facies, helped in constructing
their tectono-sedimentary model (Casshyap and Aslam 1992).
The Lower Cretaceous sedimentary rocks including the Wadhwan
Formation of Saurashtra basin were deposited in a failed
rift. The development and infilling of the Lower Cretaceous
Saurashtra failed rift was concomittent with the
pericratonic rifting and opening of the Arabian sea to the
west.
79
Fault-bounded basement uplifts along incipient rift
belts within continental blocks shed arkosic sands mainly
into adjacent linear troughs (Dickinson, 1985; Dickinson and
Suczek, 19 79). These authors have demonstrated that in such
a tectonic setting, a spectrum of lithic-poor quartzo-
feldspathic sands forms a roughly linear array on Qt-F-L and
Qm-F-Lt plots linking these arkosic sands with the craton-
derived quartzose sands that plot near the Qt and Qm poles.
However the Qm-F-Lt plot of Wadhwan sandstones (Fig. 19B)
shows that the points are mostly located on the Qm-Lt leg of
the diagram and lie in the transition zone between the
fields of continental block provenances and recycled orogen
provenances. The basement uplifts may shed sands having
affinity with detritus derived from recycled orogens
provided erosion has been insufficient to remove cover rocks
from basement (Mack, 1984). This may explain the false
signatures of recycled orogen provenance in the case of the
Wadhwan sandstones.
From the foregoing discussion, we can now construct
a plate-tectonic model for the tectonic setting of the Lower
Cretaceous Saurashtra basin during the deposition of the
Wadhwan sandstones. An incipient rift developed within the
Precambrian Aravalli continental block. The metasedimentary
and granite rocks of the Aravalli craton were deeply
80
weathered under the warm and humid climate during Lower
Cretaceous. Thus most of the labile constituents of the
source rocks v/ere destroyed by weathering, and quartzrich
detritus was shed into the Saurashtra rift. The relief of
the provenance was low and erosion processes were not strong
enough to remove the cover rocks from the basement.
CHAPTER V
SUMMARY AND CONCLUSIONS
Several prominent rift basins including the
Saurashtra basin developed in Western India at different
stages of evolution of the Indian subcontinent duing
Mesozoic. The Saurashtra basin developed in Early Cretaceous
conciding with uplift of northern Jurassic basin. The Kutch
and Saurashtra basins represent parts of an elongated
extensional trough where up and down rifting during
Jurassic-Cretaceous time brought about basin formation and
sedimentation, first in northern part (Jurassic of Kutch) and
latter in southern part (Early Cretaceous of Saurashtra).
The Early Cretaceous (Upper Tethonian to Albian:
145-97 m.y.) sedimentary rocks which are exposed in the
northeastern part of the Saurashtra basin comprise two
formations: Dharangadhra Formation (500m thick) and V7adhwan
Formation (50m thick) which are unconformably overlain by
the Deccan Traps of Late Cretaceous age.
The present study of the sandstones of Wadhwan
Formation (Early Cretaceous) of Surendranagar area mainly
aims to reconstruct their provenance and plate tectonic
setting of their deposition on the basis of petrofacies
study. A critical study of various factors influencing
detrital mineralogy of the sandstones and their provenance
interpretation has also been made.
82
The field work was carried out for the purpose of
the collection of sandstone samples from different quarries
located around the Surendranagar town. Thin sections were
made from these samples and 36 sandstone samples showing
undisturbed fabric were selected for petrographic study.
The textural attributes of the Wadhwan sandstones,
such as size, roundness, sphericity and textural maturity
were studied with a view to interpreting the provenance of
the sandstones, and estimating the influence of texture on
the detrital modes and petrofacies. Interrelationship of
various textural attributes of the Wadhwan sandstones were
studied with the help of bivariant plots.
Statistical parameters of grain size of the Wadhwan
sandstones were computed with the help of cumulative
frequency curves and formulae according to the method of
Folk (1980). The sandstones are mostly medium grained (78%),
some fine grained (19%) and very few coarse grained (3%).
Their M ranges from 0.88 0 to 2.65 jz$. The Wadhwan
sandstone^ are generally moderately sorted (61%) to poorly
sorted (33%) and occasionally moderately well sorted (6%),
their O", values ranging from 0.62 to 1.53 s6. The sandstones
are mostly strongly fine to fine-skewed (64%) and mesokurtic
(50%). Their SK^ values range from -0.01 to 1.0 and. K^
values from 0.70 to 1.5.
83
In various samples of the Wadhwan sandstones,
roundness of grains range generally from subangular to
subrounded. The mean roundness of individual samples ranges
from 0.32 to 0.41. According to their mean roundness the
individual samples are almost equally divided among
subrouned class (17 samples) and subangular class (19
samples). The aggregate data on grain roundness shows a
unimodal distribution with subrounded as the modal class.
The detrital grains of the Wadhwan sandstones are
mainly of low sphericity. Their mean sphericity values range
from 0.38 to 0.56 in various samples.
According to their textural attributes sandstones of
the Wadhwan Formation are mostly submature (80%), few are
mature (17%) and very few immature (3%).
Bivariant plots of various textural parameters, such
as mean size versus roundness, mean size versus sphericity,
mean size versus sorting, sorting versus sphericity and
sorting versus roundness show generally weak relationship.
However sorting versus sphericity plot shows a medium
relationship.
A study of grain to grain contacts of the Wadhwan
sandstones provided an idea about the degree of compaction
to which they were subjected. The average percentages of
84
various types of grain contacts in the sandstones are;
floating, 7.9 percent; point, 60.25 percent; long, 24.50
percent; concavo-convex and sutured contacts, 7.3 percent.
Abudance of floating and point contacts suggest that the
Wadhv/an sandstones have suffered little compaction and
therefore their original texture and packing are largely
preserved.
Detrital composition of the Wadhwan sandstones was
evaluated both quantitatively and qualitatively for the
purpose of (i) petrographic classification of the
sandstones and (ii) for the interpretation of their
provenance. Detrital quartz is the predominant constituent
and all the sandstones examined are quartzarenites. The
average composition of the sandstones is quartz, 98.3%; rock
fragments, 1.0%; feldspars, 0.19% and other minor
constituents (mica and heavy minerals etc), 0.57%. Among the
detrital quartz, the quartz of igneous origin (both common
and vein quartz) predominate which forms 91.0% of total
detrital quartz. The remaining grains of quartz belong to
recrystallized metamorphic quartz and stretched metamorphic
quartz. Rock fragments averaging 1.0% include chert and lov/
rank metamorphic rocks. Feldspars are not common and occur in
some samples. Feldspars average 0.19 percent. The feldspar
grains belongs to mainly orthoclase which arc weathered. The
other minor constituents are mica and heavy minerals.
85
Muscovite is more common than biotite. Opaques, tourmaline
and zircon are the main types of heavy minerals.
The clay matrix, averaging 1.6 percent, comprises
mainly kaolinite. The clay minerals appear to be both
allogenic and authigenic as indicated by their crystal habit
and morphology observed under SEM. Allogenic kaolinite was
derived by intense weathering of granites and gneisses in
the provenance, while the authigenic clay is the product of
diagenesis.
The cementing materials in the Wadhwan sandstones
are iron oxide, silica, and carbonate. The iron cement
occurs in the form of coatings around the detrital grains as
well as patches, which show replacement and corrosion of
detrital grains. The silica cement occurs in the form of
overgrowth on detrital quartz grains. The calcite cement
occuring in very few samples shov/s patchy distribution and
has corroded quartz grains.
A critical analysis of the various factors
influencing the detrital mineralogy of the Wadhwan
sandstones and hence the provenance and petrofacies
interpretation was carried out to arrive at a meaningful
conclusion. The various factors examined included
paleogeography, source rock composition, distance of
86
transport, paleoclimate, depositional environments and
diagenetic modifications.
The paleogeographic reconstruction of the Saurashtra
rift suggests that the provenance of the sandstones was
located tov/ards northeast/ in the Aravalli highlands, a few
hundred kilometer from the study area. The Precambrian rocks
of Delhi and Aravalli Supergroups identified as the
provenance of the sandstones consist of mainly quartzites
and phyllites which are intruded by granites. Detrital
mineralogy of the Wadhwan sandstones matches the composition
of the identified source rocks. The sandstones were mainly
derived from metasedimentary rocks and granite-gneisses.
The Lower Cretaceous period was marked by warm and
humid climate in the study area which was responsible for
rigorous weathering of the Precambrian basement rocks in the
provenance resulting in destruction of much of the feldspars
and labile constituents. Paleoclimate was therefore a
leading factor in the formation of highly quartzose
sandstones of the Wadhwan Formation.
The sandstones are mainly texturally submature
because they were deposited in rather protected environments
of estuaries and embayments• The compositional maturity of
the sandstones is not the result of depositional reworking,
as the sandstones do not show a comparable degree of
textural maturity.
87
Diagenetic processes such as dissolution/
replacement and compaction have brought about little
modification of the original detrital constituents.
Dissolution of feldspars has created about 2.0 percent of
secondary porosity. The replacement of quartz grain by iron
oxide and carbonate cements is only partial and localized.
The grain to grain contacts of the sandstones indicate very
little compaction.
The plate-tectonic setting and provenance of the
sandstones were interpreted with the help of Dickinson's
(1985) method of recognizing detrital modes and plotting
them on Qt-F-L and Qm-F-Lt triangular diagrames. The
detrital modes recognized and their average percentages are:
Qm (91.6%) Qp (7.1%); K-feldspar (0.19%) and Ls (1.0%). The
petrofacies analysis of the sandstones suggest continental
block provenances with source on stable craton which has
been recognized as the Aravalli craton. The continental
block provenance that supplied detritus to the Saurashtra
rift was, deeply weathered. A low relief marked the
continental block provenance permitting detritus a long
residence time in soil. The fault-bounded basement uplifts
along incipient rift belts within continental block are
known to shed arkosic sands into adjacent linear troughs,
but quartz-rich detritus was deposited into the Saurashtra
rift because of v/arm and humid climate, low relief and long
88
residence time in soil. The false signature of recycled
orogen provenance in the case of Wadhwan sandstones may be
attributed to insufficient erosion that failed to remove
cover rocks from the basement.
REFERENCES
AHMAD, A.H.M. and AKHTAR, K., 1990. Clastic environments
and facies of the Lower Cretaceous Narmada basin,
India; Cretaceous Res., V. 11, pp. 175-190.
AKHTAR, K. and AHMAD, A.H.M., 1991. Single-cycle cratonic
quartzarenites produced by tropical weathering: the
Nimar Sandstones (Lower Cretaceous), Narmada basin,
India; Sediment. Geol., V. 71, pp. 23-32.
AKHTAR, K., KHAN, M.M. and AHMAD, A.H.M., 1992. Diagenetic
evolution of a Cretaceous 'quartz arenite', Narmada
rift basin, India; Sediment. Geol., V. 76,
pp.99-109.
ASLAM, M., 1987. Sedimentation and Palaeogeography of
Mesozoic Gondwanaland rocks, Saurashtra, Gujarat
(Unpublished Ph.D. Thesis); Aligarh Muslim
University, pp. 192.
BASU, A., 1976. Petrology of Holocene fluvial sand derived
from Plutonic source rocks: Implications to
Paleoclimate interpretation; Jour. Sed. Petrol.,
V. 46, pp. 694-709.
BISWAS, S.K., 1982. Western rift basin of India and
hydrocarbon prospects; ONGC Bulletin, pp. 223-232.
BISWAS, S.K., 1987. Regional tectonic framework, structure
and evolution of the western marginal basins of
India; Tectonophysics, V. 135, pp. 307-327.
90
BISWAS, S.K. and DESHPANDE, S.V., 1983. Geology and hydro
carbon prospect of Kutch, Saurashtra, and Narmada
basin. In: Petroliferous basins of India (Ed. by
L.L. Bhandari et al.) . Petroleum Asia Journal/
Dehradun, India* V. 6, pp. 111-126.
BLATT, H. and CHRISTIE, J.M., 1963. Undulatory extinction
in quartz of igneous and metamorphic rocks and its
significance in provenance studies of sedimentary
rocks; Jour. Sed. Petrol., V. 33, pp. 559-579.
BLATT, H., 1966. Diagenesis of sandstones: Processes and
problems; Symp. 12th Ann. Conf. Wyoming Geol.
Assoc, pp. 63-65.
BLATT, H., 1967. Provenance determination and recycling of
sediments; Jour. Sed. Petrol., V. 37, pp.
1031-1044.
BOKMAN, J., 1952. Clastic quartz particles as indices of
provenance; Jour. Sed. Petrol., V. 22, pp. 17-24.
CANNON, R.T., SIMIYU SIAT IBI, W.M.N. , and KARANJA, F.M.,
1981. The proto-Indian Ocean and a probably
Paleozoic/Mesozoic triradial rift system in East
Africa; Earth and Planet. Scien. Lett., V. 52,
pp. 419-426.
91
CASSHYAP, S.M., DEV, P., TEWARI, R.C., and RAGHUVANSHI,
A.K.S., 1983. Ichno-fossils from Bhuj Formation
(Cretaceous) as paleoenvironmental parameter;
Current Sci., V. 52, pp. 73-74.
CASSHYAP, S.M. and ASLAM, M. 1992. Deltaic and Shoreline
Sedimentation in Saurashtra Basin, Western India:
An Example of Infilling in an Early Cretaceous
Failed Rift; Jour. Sed. Petrol., V. 62, pp.
972-991.
CHILINGARIAN, G.V., 1983. Compactional diagenesis; In:
Sediment Diagenesis, (Ed. A. Parker and Sellwood),
D. Reidel Publishinv^ Company, Holland, pp.57-167.-
CHIPLONKAR, G.W., and BOROKAR, V.D., 1975. Stratigraphy of
the area around Wadhwan, Saurashtra, Gujarat State,
in Verma, V.K. ed.; Recent Research in Geology,
V. 2, pp. 229-239.
CHIPLONKAR, G.W., GHARE, M.A., and BADVE, R.M., 1977. Bagh
beds their fauna, age and affinities; a retrespect
and prospect, Biovigyanam, India, V. 3, pp. 33-60.
CONOLLY, J.R., 1965. The occurence of polycrystalline and
undulatory extinction in quartz in sandstones;
Jour. Sed. Petrol., V. 35, pp. 116-135.
92
CROOK, K.A.W., 1974. Lithogenesis and geotectonics: the
significance of composition variation in flysch
arenites (graywackes) , in R.H. Dott and R.H.
Shaver, eds. Modern and ancient geosynclinal
sedimentation; Soc. Econ. Paleon. Mineral. Spec.
Publ., V. 19, pp. 304-310.
DAPPLES, E.G., 1971. Physical classification of carbonate
cement in quartzose sandstones; Jour. Sed. Petrol.
V. 41, pp. 196-204.
DICKINSON, W.R., 1970. Interpreting detrital modes of
graywacke and arkose; Jour. Sed. Petrol. V. 40 pp.
695-707.
DICKINSON, W.R., and RICH, E.I., 1972. Petrologic intervals
and petrofacies in the Great Valley Sequence,
Sacramento Valley, California; Geol. Soc. Am.
Bull., V. 83, pp. 3007-3024.
DICKINSON, W.R., and SUCZEK, C.A., 1979. Plate-tectonics
and sandstones composition; Am. Assoc. Pet. Geol,
Bull., V. 63, pp. 2164-2182.
DICKINSON, W.R., 1985. Interpreting relations from detrital
models of sandstones. In; G.G. Zuffa (editor)
Provenance of Arenites. Reidel, Dordrecht - Boston-
Lancaster, pp. 333-361.
93
EISBACHER, G.H., 1981. Late Mesozoic - Paleogene Boswer
Basin molasse and Cordilleran tectonics. Western
Canada, in A.D. Miall; ed. Sedimentation and
tectonics in alluvial basins; Geol. Assoc. Can.
Spec, paper, V. 23, pp. 125-151.
FOLK, R.L., 1966. A review of grain size parameters;
Sedimentology, V. 6, pp. 73-93.
;> FOLK, R.L., 19 .Petrology of Sedimentary Rocks. Hemphills
Austin, Texas, pp. 182.
FRANZINELLI, E. and POTTER, P.E., 1983. Petrology,
Chemistry and texture of modern river sands, Amazon
River System; Jour. Geol., V. 91, pp. 23-40.
FRIEDMAN, G.M., 1979. Difference in size distributions
populations of particles among sands of various
origins; Sedimentology, V. 26, pp. 3-32.
FUCHTBAUER, H. 1967. Influence of different types of
diagenesis on sandstone porosity; Proc. 7th World
Pet. Congr., Mexico, V. 2, pp. 353-369.
FUCHTBAUER, H., 1974. Sediments and sedimentary rocks I:
part II, 2nd ed. pp. 464, Stuttgart: E.
Schwei zerbart.
INGERSOLL, R.V. 1978. Petrofacies and Petrologic evolution
of Late Cretaceous fore-arc basin, northern and
Central California; Jour. Geol. V. 86, pp. 335-352.
94
KLEIM, G. deV, 1963, Analysis and review of sandstones
classification in the North American Geological
Literature. 1942-1960; Geol. Soc • Amer. Bull., V.
74, pp. 555-576.
KRISHNATI, n.s , I960. Geoloyy of India and Burma; Madras,
Higyinbothams, pp. 604.
KRISHNA, J., 1987. Jurassic - Cretaceous ammonoid geography
vis-a-vis marine Seaways and plate tectonics in the
Indian ocean region; Geol. Survey of India, Spec.
Pub. No. 11, pp. 453-482.
KRUMBEIN, W.C., 1940. Flood gravel of San Gabriel Canyon,
California; Bull. Geol. Soc. Amer., V. 51, pp.
636-676.
KRYNINE, P.D., 1946. Microscopic morphology of quartz
types.; An. 2nd Congr. Panamer. Ing. Minas Geol.,
V. 33, pp. 35-49.
MACK, G.H., 1984. Exception to the relationship between
plate tectonics and sandstone composition; Jour.
Sed. Petrol., V. 54, pp. 212-220.
MACK, G.H. and SUTTNER, L.J., 1977. Paleoclimate
interpretation from a petrographic comparison of
Holocene sands and the Fountain Formation
(Pennsylvanian). in the Colorado Front Range; Jour.
Sed. Petrol., V. 47, pp. 89-100.
95
MATHUR, L.P., K.L.N., RAO and A.N. CHAUBE, 1968. Tectonics
framework of Cambay Basin, India; ONGC Bull., V. 5,
pp. 7-28.
McBRIDE, E.F., 1963. Classification of conunon sandstones;
Jour. Sed. Petrol., V. 33, pp. 664-669.
HcBRIDE, E.F., 1985. Diagenetic processes that effects
provenance determination in sandstones. In: G.G.
Zuffa (Editor), Provenance of Arenites, Reidel,
Dordecht, pp. 95-114.
MIDDLETON, G.V., 1960. Chemical composition of sandstone;
Geol. Soc. Am. Bull., V. 71, pp. 1011-1026.
MOSS, A.J., 1966. Origin, Shaping and significance of
quartz sand grains; Jour. Geol. Soc. Australia, V.
13, pp. 97-136.
NAGTEGALL, P.J.C., 1978. Sandstone framework unstability as
a function of burial depth; Jour. Geol. Soc.
London., V. 135, pp. 101-106.
NORTON, I.O. and SCLATER, J.G., 1979. A model for the
Evolution of the Indian ocean and the breakup of
Gondwanaland; Jour. Geophy. Res., V. 84, pp.
6803-6830.
OKADA, H., 1971. Classification of sandstone: Analysis and
proposal; Jour. Sed. Petrol., V. 79, pp. 509-525.
96
PASCOE, E.H., 1959. Manual of Geology of India and Burma;
Govt, of India Press, Calcutta; V. 2, pp. 1280.
PATRIAT, P. and SEGOUFIN, J., 1988. Reconstruction of the
Central Indian Ocean; Tectonophysics, V. 155,
pp.211-234.
PETTIJOHN, F.J., POTTER, P.E. and SIEVER, R., 1972. Sand
and Sandstone; New York, Springer, pp. 618.
PITTMAN, E.D., 19L63 . Use of zoned plagioclases as an
indicator of provenance; Jour. Sed. Petrol., V. 33,
pp. 380-386.
PLUMBLAY, W.J., 1948. Black Hills terrace gravel: a study
in sediment transport; Jour. Geol., V. 56,
pp.526-577.
POWELL, C , McA. ROOTS, S.R. and VEEVERS, J. J. 1988.
Pre-breakup continental extension in East
Gondwanaland and early opening of the Eastern
Indian Ocean; Tectonophysics, V. 155, pp. 261-283.
POWERS, M.C., 1953. A new roundness scale for sedimentary
particles; Jour. Sed. Petrol., V. 23, pp. 117-119.
PRATSCH, J.C, 1978. Future hydrocarbon exploration on
continental margins and plate tectonics; Jour.
Petrol. Geol., V. 1, pp. 95-105.
RIVIERE, A., 1977. Methods granulometriques: techniques et
interpretation; Paris, Masson, pp. 170.
97
RUSSEL, R.D., 1939. Effect of transportation on sedimentary
particles in Recent marine sediments (Trask, P.D.
ed.); Tulsa, Okla; Amer. Assoc. Pet. Geol. pp. 32-47.
RUSSEL, R.D. and TAYLOR, R.E., 1937. Bibliography on
roundness and shape of sedimentary rock particles.
Kept. Comm. Sedimentation, 1936-1937; Nat. Res. Coum.
pp. 65-80.
RUXTON, B.P., 1970. Labile quartz-poor sediments from Young
mountain ranges in northeast Papua; Jour. Sed.
Petrol., V. 40, pp. 1262-1270.
SCHWAB, F.L., 1975. Framework mineralogy and chemical
composition of continental margine-type sandstones;
Geology, V. 3, pp. 487-490.
SCHWAB, F.L., 1981. Evolution of the western continental
margin, French-Italian Alps: Sandstone mineralogy as
an index of plate tectonic setting; Jour. Geol.,
V.89, pp. 349-368.
SCOTESE, C.R., GAHAGAN, L.M. and LARSON, R.L., 1988. Plate
.tectonic reconstruction of the Cretaceous and
Cenozoic Ocean basins; Tectonophysics, V. 155,
pp.27-48.
SENGOR, A.M.C., BURKE, K. and DEWEY, J.F., 1978. Rifts at
high angles to erogenic belts; tests for their origin
and the upper Rhine Graden as an example; Amer. Jour.
Scien., V. 278, pp. 24-40.
98
SMALLEY, I.J., 1966. Origin of quartz sand; Nature, V. 211,
pp. 476-479.
SUTTNER, L.J., 1974. Sedimentary petrographic provinces: An
evolution; SEPM Sp. Pub. No. 21, PP. 75-84.
SUTTNER, L.J., BASU, A. and MACK, G.H., 1981. Climate and
origin of quartz arenites; Jour. Sed. Petrol., V. 51,
pp. 1235-1246.
TANKARD, A.J., JACKSON, M.P., ERIKSON, K.A., HOBDAY, D.K.,
HUNTER, D.R., and WINTER, W.E.L., 1982. Crustal
evolution of South Africa; New York, Springer-Verlog,
pp. 523.
TAYLOR, J.M., 1950. Pore-space reduction in sandstones; Bull.
Am. Assoc. Pet. Geol., V. 34, pp. 701-716.
THOMPSON, S.L. and BARRON, E.J., 1981. Comparison of
Cretaceous and present earth Albedos: Implications
for the causes of Palaeoclimates; Jour. Geol., V. 89,
pp. 143-167.
VALLONI, R. and MAYNARD, J.B., 1981. Detrital modes of recent
deep sea sands and their relation to tectonic setting:
a first approximation; Sedimentology, V. 28,
pp.75-84.
99
VARADARAJAN, K. and GANJU, J.L., 1989. Lineament analysis of
coastal belt of Peninsular India, in Qureshy, M.N.
and Hinze, W.J., eds. Regional Geophysical
Lineaments; Geol. Soc. of Ind. Mem., V. 12, pp.49-58.
VISHER/ G.A., 1969. Grain size distribution and depositional
processes; Jour. Sed. Petrol., V. 39, pp. 1074-1106.
Voll, G., 1960. New work on petrofabics: Liver-Pool and
Manchester; Jour. Geol., V. 2, Pt. 3, pp. 503-567.
WADELL, HAKON, 1935. Volume, Shape and roundness of rock
particles; Jour. Geol. V. 40, pp. 443-451.
WEN-n-^ORTH, C.K. 1919. A laboratory and field study of cobble
abrasion; Jour. Geol., V. 27, pp. 507-521.
WEST, W.D., 1962. The line of the Narmada and Son Valleys;
Curr. Sci., V. 31, No. 4, pp. 143-144.
WESTERMANN, G.E.G., 1988. Middle Jurassic ammonite
biogeography support ambi-Tethyan origin of Tibet, in
Audley-Charles, M.G. and Hallam, A. eds. Gondwana and
Tethys, Oxford, Oxford University Press; Geol. Soc.
Spec. Pub. No. 37, pp. 235-239.
YOUNG, S.W., BASU, A., MACK, G., DARNELL, N. and SUTTNER,
L.J., 1975. Use of size-composition trends in
Holocene soil and fluvial sand for Paleoclimatic
interpretation; Ninth Intern. Sedimentology Congr.
theme., 1, pp. 201-209.
100
ZUFFA, G.G., 1980. Hybrid arenites: their composition and
classification; Jour. Sed. Petrol./ V. 50, pp. 21-30.
APPENDICES
KAR.RCSI7
• NAME OF sssssrsssss
X S S S 3 S S S X S S S
1 . 5 5 0 1 . 5 0 0 1 . 7 0 0 1 , 9 0 0 1 . 6 0 0 0 . 8 8 0 1 . 9 3 0 1 . 6 6 0 1 , 4 0 0 1 . 6 5 0 1 , 5 0 0 1 , 8 0 0 1 . 5 0 0 1 . 4 5 0 1 . 6 0 0 2 . 1 9 0 1 . 1 5 0 1 . 7 0 0 2 . 0 5 0 1 , 6 0 0 2 . 6 5 0 1 . 6 6 0 2 . 4 8 0 1 . 9 8 0 1 . 8 6 0 1 . 1 6 0 1 . 2 6 0 1 . 6 0 0 1 . 8 1 0 1 . 8 6 0 1 . 4 8 0 2I08O 1,530 2.150 1.700
sBBsaasrssss 61.
Z S S 8 S S S S X 3 S S
BLOCK =
Y
'.»
SIZE Vs
27-MAY-1093
R0UNDNEv*5S ;rsrssrsss = r:
• ij t *
.380
.370
.400
.380
.390
.370 ,360 .410 .360 .340 .350 .330 .370 .350 .330 .380 .350 .350 .380 . tHO .3«0 .360 .3*»0 .340 .340 .320 .370 .380 .370 .350 .3 50 .390 .360 .360 .320 .360
xssssssas 660 ssssssssx
0, 0, 0. 0, 0, 0, 0, 0, 0, 0. 0, 0. 0. 0, 0,
0, 0, 0, 0, 0. 0, 0, 0, 0, 0. 0, 0. 0. 0.
0, 0. 0, 0, 0,
S s S
sas
Dx . 0 . 1 6 3 . 0 . 2 1 3 . 0 . 0 1 3 0 . 1 8 7 :S:JH 0 . 2 1 7
' 0 . 3 1 3 '0 • 06 3 '0 ,21 ' 0 , 0 8 ^ 0 . 2 1 3 0 , 2 6 3 VM= . 0 . 5 6 1 •O.Ol i 0 . 3 3 7
• 0 . 1 1 3 0 .Q3^
. 0 . 0 5 3 0 . 7 6 7 0 . 2 6 7 0 . 1 4 7
• 0 . 5 5 3 0 . 4 5 3 0 . 1 1 3 0 . 0 9 7 0 . 1 4 7 0 . 2 3 3 o'Ali 0 , 1 8 3 0 , 4 3 7 0 . 0 1 3
Dv 0 . 0 1 7 0 . 0 0 7 0 . 0 3 7 0 . 0 1 7 0 . 0 2 7 0 . 0 0 7
- 0 . 0 0 3 0 . 0 4 7
- 0 . 0 0 3 - 0 . 0 2 3 - 0 . 0 1 3 - 0 . 0 3 3
0 . 0 0 7 - 0 . 0 1 3 - 0 . 0 3 3
0 , 0 1 7 - 0 , 0 1 3 - 0 , 0 1 3
0 , 0 1 7 0 . 0 1 7 0 . 0 1 7
- 0 . 0 0 3 0 . 0 2 7
- 0 . 0 2 3 - 0 . 0 2 3 - 0 . 0 4 3
0 . 0 0 7 0 . 0 1 7 0 . 0 0 7
- 0 . 0 1 3 - 0 . 0 1 3
0 . 0 2 7 - 0 . 0 0 3 - 0 . 0 0 3 - 0 . 0 4 3 - 0 . 0 0 3
DXS
0 , 0 2 6 0 . 0 4 5 0 . 0 0 0 0 , 0 3 5 0 . 0 1 3 0 , 6 9 4 0 , 0 4 7 0 , 0 0 3 0 , 0 9 8 0 . 0 0 4 0 . 0 4 5 0 , 0 0 8 0 , 0 4 5 0 , 0 6 9
0 . 2 1 8 0 , 3 1 7 0 , 0 0 0 0 . 1 1 4 0 . 8 7 8 0 . 0 0 3 0 , 5 8 9 0 , 0 7 1 0 , 0 2 2 0 , 3 0 6
0 , 0 1 3 0 . 0 0 9 0 . 0 2 2 0 , 0 5 4
oioli 0 , 0 0 0
1 3 , 0 7 0 0 , 0 0 0
rsasss Dy
:3sssa 0 0 0 0
0 0 0 0
rsaaaa Bsaass
ssssssxa S D saaasass .000 .000 ,001 ,000 ,001 ,000 ,000 .002 .000 .001 . 000 .001 .000 .000 .001 .000 .000 .000 .000 .000 .000 .001 .001 .001 .002 .000 .000 .000 .000 .000 .001 .000 .000 .002 .000 aaaaai
0,000 saaaasas
isaasaa: xDv aasssBi -0.003 -0.001 0.000 0.003
-0,003 -0.006
•5«50i -0.002 0.001 0.001
.?:SSl
0.016 0.000
-0!006 -0.003 0.024
-0,003 •0.002 0.001
-0.002 $.003
0.001 -0,019 0.000
asvaaaaaa:
r s 0,1925. Prcent«ne= 3,7o730 r Squar Or CoeffI*^rIentof determination a 0.16829 standard errors 1,14412
aasaaasssassssssassBssssassasssssaaaasaasaasasaaasaaaaaaaaaaaaaaaaaaaaaa: -1 to tl is ranac of r IF r < 0.3 the Correlation beween varlableg is weak, r 0,3 to 0,7 mertinm. r > 0,7 strono
'^ KAR.RES;10
NAMK -OF BLOCK = sssrsszssrss:==r:=s:
X Y S 8 X S S P S S 3 = S S S Z S S S S S :
27-MAy-l993 20:37 P«ae 1 SIZE VS SHAPE
Dx
1 . 5 5 0 1 . 5 0 0 1 . 7 0 0 1 . 9 0 0 1 . 6 0 0 0 . 8 8 0 1 . 9 3 0 1 . 6 6 0 1 . 4 0 0 1 . 6 5 0 1 . 5 0 0 1 . 8 0 0 1 . 5 0 0 1 . 4 5 0 1 . 6 0 0 2 . 1 8 0 1 . 1 5 0 1 . 7 0 0 2 . 0 5 0 1 . 6 0 0 2 . 6 5 0 1 . 6 6 0 2 . 4 8 0 1 . 9 8 0 1 . 8 6 0 1 . 1 6 0 1 . 2 6 0 1 . 6 0 0 1 . 8 1 0 1 . 8 6 0 1 . 4 8 0 2 . 1 0 0 2 . 0 9 0 1 . 5 3 0 2 . 1 5 0 liZ22-_
6? s B s r r s s r s s s
0 . S 6 0 0 , 5 6 0 0 , 5 5 0 0 . 4 4 0 0 , 4 7 0 0 , 4 5 0 0 , 4 1 0 0 . 3 8 0 0 . 4 6 0 0 . 4 1 0 0 , 4 1 0 0 , 4 0 0 0 , 4 1 0 0 , 4 1 0 0 . 4 4 0 0 , 4 5 0 0 . 4 7 0 0 . 4 4 0 0 , 4 ? 0 0 . 4 5 0 0 , 4 1 0 0 . 4 1 C 0 , 4 2 0 0 . 4 2 0 0 . 3 8 0 0 , 4 4 0 0 , 4 4 0 0 , 4 9 0 0 . 4 5 0 0 . 4 3 0 0 . 4 2 0 0 , 4 5 0 0 , 4 2 0 0 . 4 1 0 0 . 4 7 0 0 . 4 0 0
7660 s s s s s s s s s s s
- 0 . 1 6 3 - 0 . 2 1 3 - 0 , 0 1 3
0 , 1 8 7 - 0 . 1 1 3 - 0 , 8 3 3
0 . 2 1 7 - 0 . 0 5 3 - 0 . 3 1 3 - 0 . 0 6 3 - 0 . 2 1 3
0 . 0 8 7 - 0 . 2 1 3 - 0 . 2 6 3 - 0 , 1 1 3
0 . 4 6 7 - 0 . 5 6 3 - 0 , 0 1 3
0 , 3 3 7 - 0 , J 1 3
0 , 9 3 7 - 0 , 0 5 3
0 . 7 6 7 0 . 2 6 7 0 , 1 4 7
- 0 , 5 5 3 - 0 , 4 5 3 - 0 , 1 1 3
0 , 0 9 7 0 . 1 4 7
- 0 . 2 3 3 0 , 3 8 7 0 . 3 6 7
- 0 . 1 8 3 0 . 4 3 7
- o . o n TRTS
s s s s s s s
DV
0 0 0
• 0 0 0
• 0 • 0 0
• 0 . 0 •0 . 0 - 0 .0 0 0
. 0
. 0 0
-0 >0 • 0 • 0 •0 •0 •0 0 0
•0 • 0 0
• 0 • 0 0
• 0
,119 .119 ,109 ,001 .029 ,009 .031 .061 .019 ,031 ,031 ,041 ,031 ,031 ,001 ,009 ,029 001
DXS DyS DxDv : S S S S B B B S S S S 3 S S S S S S 3 S 3 S B 8 S S S S a S :
-0.021 0.009
001 ,031 ,021 ,021 ,061 ,001 ,001 ,049 ,009 .011 ,021 ,009 ,021 ,031 ,029 ,041
0,026 0.045 0.000 0,035 0.013 0.694 0.047 0.00 3 0.098 o.ooa 0.045 0.008
045 069 013
..218 0.317 0,000 0.114
013 878 003 589 071
,.022 0.306 0.205 0.013 0.009 0.022 0.054 0.150 0,135 0,033 0,191 0,000
0 .014 0 ,014 0 .012 0 .000 0 .001 0 .000 0 . 0 0 1 0 . 0 0 4 0 .000 0 .001 0 . 0 0 1 0 . 0 0 2 0 . 0 0 1 0 .001 0 . 0 0 0 0 . 0 0 0 O.OOl 0 .000 0 . 0 0 0 0 .000 0 .000 0 .001 0 .000 0 .000 0 . 0 0 4 0 .000 0 .000 0 .002 0 .000 0 . 0 0 0 0 .000 0 .000 0 .000 O.OOl
km
- 0 . 0 1 9 - 0 . 0 5 5 - 0 , 0 0 1
0 . 0 0 0 -0-002 - 0 . 0 0 7 - 0 . 0 0 7
0 . 0 0 3 - 0 , 0 0 6
0 .008 0 , 0 0 0 0 . 0 0 4
- 0 , 0 1 6 0 . 0 0 0
- 0 , 0 0 7 - 0 . 0 0 1 - 0 , 0 0 1
0 . 0 0 2 - 0 . 0 1 6 - 0 . 0 0 6 - 0 , 0 0 9
0 .001 0 , 0 0 1
- 0 , 0 0 6 -olSoi
0 , 0 0 5 0 .003
- 0 , 0 0 8 0 , 0 0 6 S:8i? B Z S S S S S S S S S S B S B B S B B S B S S B a a S S a S :
0,000 0,000 BBBssBSBSssBSBBsssassasaaaaaaa:
r = -O.J521 Prcentaoe= -2,3t280 * .,«.^ r Squar nr Coeffleclentof determination s 0.16950 standard errors -0,89720
iBsssBssBssssBsssBsssSBssssBSBSsBSBSsssssBssBsassaBsaBBBsaaaaaaaaaaaas •1 to 41 is r«nae of r - , ^. . IF r < 0.3 the correlation beween variables Is weak. r 0.3 to 0.7 mer'lijm. r > 0,7 . trono
KAR,RES;7
NAME OF asBrsrsssss
X aasrssBBSSs
1.120 0.720 l.OJO 0.890 1.000 1.050 0.930 0.800 0.760 1.000 0.790 0.900 l.llO 1.040 0.990 0.910 1.160 1,210 0.900 1.050 0,960 0.890 0.770 0,670 1,090 0,780 0.930 0.840 1,120 0,860 0,920 0.620 0.840 0,830 1,100 1.530
BLOCK s
Y sssssssss
0,380 0.370 0.400 0.380 0.390 0.370 0.360 0.410 0.360 0.340 0,350 0.330 0.370 0.350 0,330 0.380 0.350 0.350 0,380 0,380 0.380 0.360 0.390 0,340 0.340 0.320 0.370 0.380 0.370 0.350 0.350 0.390 0.360 0.360 0.320 0.360
BXBsatsaBSBsastfSBaass 34,
r :
.090
SORTING sss~S7Ssss—:
nx S S S S S S B S S S B :
0.173 -0.227 0.063 -0.057 0,053 0,103 -0.017 -0.147 -0,lfl7 0.053 -0.157 -0.047 0,163 0.093 0.043 -0.037 0.213 0.263 -0.047 0.103 0.013
-0.05^ -0.177 -0,277 0,143 -0,167 -0,017 -0.107 0.173 -0.087 -0.027 -0,327 -0.107 -0,117 0,153 0.583
sss—saBSSss: 13.070
s -0.1228 Prcentaqes 1 r Squar Or Coeff
,50716 ('•clentof d«
27-MAY-1993 20110
VS ROUNDNFSS SSSSSSSSZSSB
DV
0.017 0.007 0.037 0.017 0.027 0.007 -0.003 0.047
-0.003 -0.023 -0,013 -0.033 0.007 -0.013 -0,033 0.017
-0.013 -0.013 0,017 0.017 0,017
-0.003 0.027 -0.023 -0,023 -0,043 0.007 0.017 0.007
-0.013 -0.013 0.027
-0,003 -0.00 3 -0.043 -0.003
S B S S B B S B : DXS
0.030 0.052 0,004 0.003 0.003 o.on 0.000 0.022 0.035 0,003 0.025 0.002 0.027 0,009 0.002 0.001 0.045 0.069 0,002 0.011 0.000 0.003 "•921 0.077 0,020 0,028 0,000 0.011 0.030 0,008 8:?8; i-.m 0.023 0.340
rSSBBSSBBXBXBBBSaSSSa 0,000
zxssasssssBSBssssasas
'termtnatIon = 0.
Paae 1
:ssssssxsBBS9CBaasBs Dys
ESSSBBXBB 0.000 0.000 0.001 0.000 0,001 0.000 0.000 0,002 0.000 0,001 0.000 0.001 0.000 0.000 0,001 0.000 0,000 0.000 0,000 0,000 0,000 ?:88! 0,001 0,002 0,000 0,000 0,000 0,000 0.000 0.001 0.000 0,000 0,002 0,000
aasaaaaB 0.
w S B B B ^ i B S
17020
DxOv SSSSSBSBBBB
0,003 -o.oof .8:8Sf o.oo! 0.001 O.OOQ
-0.007 o.ooi -0.001 0.002 0.002 0.001 -0.001 -0.001
•oIooS -0.003
-S:8?i t'M
•8:S8I -8:8?? 0.000 -0,002 0.001
O.ooi 0.000 -0.009 0.000 0.000
-0.007 •0.002
mmmmmmMmmm* 000
standarfi «»rror* '^•^21^2 _ - -
-1 to *l Is ranae of r -IF r < 0 3 the correlation beween variables is weak, r 0,3 to 0.7 medium, r > 0,7 strona
SaSBSB8BBB: