PALEOENVIRONMENTAL SIGNIFICANCE OF CLAY

MINERALS

BY

ADEYINKA SOLOMON

08/30GA011

OUTLINE

INTRODUCTION

ANALYTICAL TECHNIQUES

PALEOENVIRONMENTAL PROXIES

CASE STUDY

CLAY MINERALOGY IN OIL AND GAS

CLAY MINERALS AND THEIR PALEOENVIRONMENTAL SIGNIFICANCE

INTRODUCTION

The clay mineralogical composition of sediments can reflect several Paleoenvironmental conditions such as Paleoclimatic conditions, Burial history, Paleotectonic regimes, sea level fluctuations, as well as continental and basin morphology, evolutionary history and the timing of various geologic events.

INTRODUCTION

Clay mineralogy is considered a powerful tool for the interpretation of weathering conditions and Paleoclimate in a source area (Ahlberg et al., 2003; Chamley, 1989; Deconinck et al., 2005; Dera et al., 2009; Ruffell et al., 2002).

ANALYTICAL TECHNIQUES

X-Ray Diffraction Analysis

Scanning Electron Microscopy

Transmission Electron Microscopy

Infrared Spectroscopy

Differential Thermal Analysis

Thermo-Gravimetric Analysis

Chemical Analysis

ANALYTICAL TECHNIQUES

Neutron Scattering

Electron Spin Resonance,

Neutron Magnetic Resonance,

Mossbauer Spectroscopy and

Ultraviolet and Visible Light Spectroscopy

PALEOENVIRONMENTAL PROXIES

Illite Crystallinity

Smectite:Illite Ratio

Kaolinite:Illite Ratio

Smectite:(Illite+Chlorite)

Figure1. Illite crystal structure under Scanning Electron microscope

Figure2. Kaolinite, Illite and Smectite under Scanning Electron Microscope

CASE STUDY- PINJOR FORMATION

Figure 3. Geological map of the Pinjor Formation in the type area Pinjor and surrounding regions (After Chaudri and Singh, 2012).

CASE STUDY- PINJOR FORMATION

Pinjor Formation is Late Pliocene-Early Pleistocene in age.

The three lithostratigraphic units of the Formation are the Kona Clay Member, the Tanda Bhagwanpur Wacke Member and the Chauki Nadah Pebbly Bed Member which are well exposed along the Berwala-Mandhna section, the Kona-Karaundanwala section and the Ghagar River-Chauki Nadah section on, northwestern Himalaya, India.

PINJOR FORMATION

X-ray diffraction techniques have been utilized for analyzing the clays of the Pinjor Formation mainly because of availability of instrument and reliability of the technique (Rostasi et al., 2009).

Forty seven representative samples from each of the measured section and random samples of the Pinjor Formation were analyzed for clay mineral studies. The area of investigation spreads over 504 sq. km. in the frontal Himalayan terrain.

PINJOR FORMATION

Schoonmaker et al. (1986) found that the depth distribution of Illite/Smectite (I/S) compositions showed an irregular, zig-zag trend with depth. This trend indicates multi-stage reverse faultings which resulted from the compressional tectonic movement.

I/S data were also used to infer several kilometers of uplift and subsequent erosion of the section.

CLAY MINERALOGY IN OIL AND GAS

Figure 4. Generalized relationship between temperature, hydrocarbon generation, diagenesis, source rock maturity (vitrinite reflectance), changes in mixed-layer illite/smectite. Figure and data summarized

from Foscolos et al (1976), Hoffman and Hower (1979), Waples (1980), Tissot and Welte (1984).

CLAY MINERALS AND THEIR PALEOENVIRONMENTAL SIGNIFICANCE

Paleoclimate is inferred from the presence of certain clay mineral species in a sediment.

Knowledge of the Physicochemical condition that surrounds the formation of these mineral species are used to infer the Paleoclimatic condition of the environment as at time of their formation

CLAY MINERALS AND THEIR PALEOENVIRONMENTAL SIGNIFICANCE Formation of illite and chlorite is typical during the

initial stages of chemical weathering by the transformation of micas and ferro-magnesian minerals, respectively (Fürsich et al., 2005; Weaver, 1989).

They are common products in low-hydrolysis weathering regimes, typical of cool and temperate or dry climates because they are insensitive to chemical weathering relative to mafic rock forming minerals and feldspars.

Additionally, they are typical clay minerals of the present-day high latitudes indicating the predominance of physical weathering over continental hydrolysis (Weaver, 1989).

CLAY MINERALS AND THEIR PALEOENVIRONMENTAL SIGNIFICANCE

Presence of illite and kaolinite suggests their derivation from crystalline rocks containing feldspar and mica as also from pre-existing soils and sedimentary rocks

During the advanced stages of chemical weathering, formation of smectite and kaolinite are typical (Chamley, 1989; Fürsich et al., 2005; Weaver, 1989).

CLAY MINERALS AND THEIR PALEOENVIRONMENTAL SIGNIFICANCE

The abundance of kaolinite is a particularly good marker for the weathering of landmasses with steep slopes and good drainage under a hot and humid (subtropical to tropical) climate (Chamley, 1989; Fürsich et al., 2005; Ruffell et al., 2002).

Smectite forms under seasonally wet and dry climates and indicates landmasses with low and poorly drained relief (Fürsich et al., 2005; Ruffell et al., 2002). Accordingly, kaolinite/illite, smectite/illite and smectite/(illite+chlorite) ratios are used by many authors for palaeoclimatic reconstructions (e.g. Deconinck et al., 2003, 2005; Liu et al., 2005; Raucsik and Varga, 2008 ).

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