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ASPECTS ABOUT PRUT RIVER TERRACES IN ROMANIAN-MOLDAVIAN BASIN SECTOR, WITH SPECIAL VIEW ON GEOMORPHOLOGYCAL
PROCESS
Florin VARTOLOMEI
1 Spiru Haret University, Faculty of Geography, Email [email protected]
Abstract
Strating with Mio-Pliocene of Moldavian Plateau rising, the old tracks of Carpathian rivers was oriented to South-East direction, following the decreasing and shoreline oscilation. In the same way, but from North direction, the evolution of Prut river was marked. The other valleys was generated later by transformations and re-traking, often visible in landscapes and in hydrographical basin configuration. Stream action, powered by rising of entire area in late Pliocene and Quaternare pariod, was united with versants and interfluves evolution process, so that the old marine acumulation plane was destroyed (the South part of Moldavia was excepted, where interfluves still keep some sections of Romanian-Pleistocene Plain), also replace with derived landforms, mostly sculptural, with hilly aspect, where litologycal and structural particularities of geologycal base was strongly underlined Keywords: valley, terrace, Prut river, paleogeographycal evolution, landforms, floodplain.
1. INTRODUCTION
Location and morphometric elements: Prut basin is situated in the eastern part of
Romania, being a pool of contact between the Moldavian Plateau, from Romania to the west and
Podolia Plateau, from the Republic of Moldova in the east. Evolution and geographical aspects are
related to the Moldavian Plateau, some authors considering this unit subdivision of this plateau.
Prut catchment occupies in Romania area of 10,970 sqkm and with related areas in Ukraine and
Moldova a total of 28,396 sqkm (Fig. 1).
Currently, Prut river is the natural border between Romania and Rep. of Moldova with
length of 695 km (Vartolomei F., 2003).
Geological conditions: under this aspect, Prut basin overlaps three structural units:
Moldavian Platform (up to Fălciu - Plopana fault), Bârladului Platform (between Falciu- Plopana
and Adjud - Oancea faults) and Platform Covurluiului, each presenting a folded socket
configurations covered by a blanket, with parties willing homocline (Bacauanu et al., 1980).
The landscape is presented as a set of inter-fluves stretched-looking bridges, hills separated
by wide valleys carved in sedimentary monocline. General landscapes orientation to the south -
southeast, the same direction as the major valleys orientation, reflects an obvious adaptation to the
structure. Monoclinic structure favored the emergence of positive and subsequent valleys (Fig. 2).
©Department of Geography. Valahia University of Targoviste Annals of Valahia University of Targoviste. Geographical Series
Tome 13/2013 Issues 2: 88-98
http://fsu.valahia.ro/avutgs/home.html
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Fig. 1. Placing Prut river basin in Danube basin
(GIS processing vectors of EEA source)
The main steps to be taken in morphology, have values of 300-500 m in the north-west, 300-
400 m in the central part, 150-200 m in the north-east and south and a relatively balanced
distribution. Altitudes above 500 m are few and isolated. The lowest shares are found along the
corridor Prut (130 m to Oroftina, 32 m near Ungheni and below 15 m to confluence) (Bacauanu,
1968).
Climate: because of its position in extra-carpathian region, away from the influence of air
masses from Atlantic Ocean, but wide open to continental air masses action originating from the
east, northeast and north, Prut basin receives moderate rainfall quantities. Prut basin, superimposed
on the Plain of Moldavia, is directly exposed to continental air masses in which, air from the west
descent surrounding physical and geographical units, frequently suffer föehn processes, so rainfall
is low, ranging generally around 500 mm (Radauti 564.0 mm, 529.4 mm Iasi) (Bogdan, 2007).
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Fig. 2. The hydrographic basin of the Prut - general view (GIS vector processing of source www.geo-spatial.org)
2. EVOLUTION OF PRUT VALLEY
Since the first studies on the Moldavian Plateau, area including Prut basin, from those of
Cobălcescu Gr. beginner, it was shown that the general inclination of the layers that make up the
covers this basin is NW to SE, as successive product withdrawal sea. The main rivers follows
consistent slope classes. Compared to current knowledge on the basement area, things do not seem
so simple, for while the river main flow direction is generally indicated (NW-SE), Moldavian
Plateau natural region shows a cross routing to these courses (Muşinschi, 2000).
So, Tufescu V. (1946) distinguishes four units (called by the author "zone") of the
Moldavian Plateau from N to S, passing the one side of the Prut valley, radial Carpathian arch:
a) to north, Plain of Moldavia (consisting of the Jijia and Raut);
b) in the middle, the Massif Central Moldavian and Bacu’ Massif;
c) to south Bârladul’ Hills and Hotărniceni Hill
d) the extended zone of Bârladul’ Hills to lower Siret Plain and Bugeac.
In general, the conduct of these natural regions in the form of a central transverse ridges
(SW-NE direction) is presented high, bounded on the north and south by two lowland areas.
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Crossing this ridge, which extends transversely, formed in high regions of middle
Moldavian Plateau, the main rivers prints local changes in their courses, in all courses presented
approximate N-S direction (from NW-SE to tributary) and valleys with sectors that are narrow,
presented like a real "gates" for longitudinal movement (Bacauanu, 1961). Prut valley is suffering a
real stranglehold between Tutora and Răducăneni (Tutora’s Gate).
Floodplain of Prut river, very well individualized, located on the axis of this basin is the
largest alluvial plain of the whole area, with widths of 3-6 km up to 10 km, with sectors
enlargement (common field Jijia-Prut) or narrow (Cernăuţi’s Gate, Tutora’s Gate) and lower slopes
of up to 0.6 ‰ (Bacauanu, 1973).
Prut basin formation begins after the Sarmatian regression wich favored, in the upper valley
of the Prut, the continental conditions appearance extended gradually to the southwest. In
Bessarabia, Upper Prut sector present a plain where denudation processes and lacustrine-deltaic
sedimentary as well had the same intake. Shoreline marine basin was located in the north of the
Central Moldavian Plateau. In south sea basin was continous, with clays sedimentary process. In
Kersonian denudation processes have been intensified in all area, corresponding upper and middle
basin of the Prut (Muşinschi, 2000).
In the radius of the Central Moldavian Plateau predominate fluvial-deltaic accumulation
facies and denudation processes had a minimal contribution. Marine shoreline met in the south of
Codrilor Hills. Fluvial network have west-east general direction.
In the Pliocene, the recent plain from upper and middle sectors of the Prut basin, the primary
fluvial network had north-south direction. Subsequently, this fluvial deposits system have been
eroded. They have kept only the Central Moldavian Plateau watershed and in the Lower Prut river
crossing in marine deposits. This package consists of fluvial-deltaic seven horizons (Fig. no. 3). The
last four are supposed to belong to paleo-fluvial Prut system, which form in the Carpathian
Mountains and therefore Bucatciuc et al (1988) attributes the Stolniceni, Buciumeni, Văleni-
Leuseni Obileni-Ungheni terrace deposits (Muşinschi, 2000).
Fig. 3. Longitudinal profile on Prut river, from entering the country to its mouth
(source Muşinschi, 2000, processing after Gojâc, 1964)
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At the end of the Pliocene began a new stage of development of the region, under the
influence of eustatic tectonic movements and several climate cycles succession when exondate
surfaces was extended and when the current Prut valley was created. Lithological structure, fossils
forms in these deposits and morphological-sculptural character enable us to share the Prut valley
evolution in seven phases, spatial limited in line with Black Sea developments.
All phases of training valley are summarized in Table. no. 1, where it is possible to catch
them in succession from Sarmatian to Holocene.
3. EVOLUTION OF PRUT TERRACES
Age, evolution and valleys hierarchy is evidenced by the number and distribution of terraces
altitude. They are characterized by a series of fragmented bridges that keeps obvious parallelism
with the longitudinal profile of river beds, through a perfect connection of steps along the main
valleys and tributaries, as well as by a decrease in the number and altitudes for younger generations
of valleys.
Table 1. Stages of Prut valley evolution*
Sectors
Phase Upper Middle Lower
MIOCENE
Buglovian
Denudation-
sedimentary (very
lacustrine)
Sedimentary (very
marine) Sedimentary (very marine)
Basarabian Denudation
Denudation-
sedimentary (very
lacustrine)
Sedimentary (very marine)
Kersonian Denudation Denudation Sedimentary (very lacustrine-
marine)
PLIOCENE
Stolniceni Denudation Denudation Sedimentary (very lacustrine-
marine)
Buciumeni Denudation Denudation Sedimentary (very lacustrine-
marine)
Văleni-Leuşeni Denudation Denudation Sedimentary (very lacustrine-
marine)
Obileni- Ungheni Denudation Denudation Denudation- sedimentary
(very lacustrine)
PLEISTOCENE
Văleni Denudation Denudation Denudation
Obileni-Slobozia Mare Denudation Denudation Denudation- sedimentary
(very haven)
Sculeni- Giurgiuleşti Denudation Denudation Denudation- sedimentary
(very haven)
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Călineşti -Câşliţa Prut Denudation Denudation Denudation- sedimentary
(very haven)
Chetriş- Giurgiuleşti Denudation Denudation Denudation- sedimentary
(very haven)
Fălciu-Cahul Denudation Denudation Denudation- sedimentary
(very haven)
Bolotina- Vetrişoara Denudation Denudation Denudation
* after Muşinschi, 2000, with additions
A comparative analysis of studies of various authors who have dealt with Prut terraces
dating we conclude the existence of two or three steps of meadow and seven or eight terraces
relative altitudes up to 160-170 m in Prut Valley and all along Bahlui (Table 2).
Table 2. Altitude of terraces on the right bank of Prut*
Moldavian Plain Huşi Depression The shedding area
V. Băcăuanu I. Gugiuman V. Sficlea
T1 10-15 m 5-11 m 8-15 m
T2 20-25 m 18-32 m -
T3 30-35 m - 30-35 m
T4 60 m 57-58 m 60-75 m
T5 90-100 m 100-105 m 110-120 m
T6 110 m - -
T7 140-150 m 134-140 m 130-150 m
* benchmarking of studies conducted by different authors
Tectonic platform regime with slight epirogenetical Pleistocene lifting, is reflected in
maintaining unchanged the relative altitudes of the terraces on the distances of tens and even
hundreds of kilometers. In general, all terraces with heights up to 60-70 m are well kept, wider and
wider near the confluences (Fig. 4).
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Fig. 4. Prut terraces map (processing after V. Muşinschi, 2000)
Regarding the particle size composition and beds west mobility mostly of the Prut river beds
consist of fine sand (0.1-1 mm), have a high coefficient of meandering, surface deformation and
depth.
The Prut floodplain sometimes occur two to three steps with relative altitudes between 1 and
7 m, cut into the same alluvial complex. These steps with relative altitudes, along them outlines
numerous old and abandoned meanders, popin (isle), micro-depressions of terraces, lower areas
with excess moisture (Fig. 5).
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Fig. 5. Morphological elements in the lower Prut - south of Oancea village
(processing after 1:25000 scale topographic map)
Significant are the old courses called "Prutuleţ" or "old Jijia". Processes and natural forms
are modified increasingly stronger through hydrotechnical works or gravel ballast exploitations (the
Prut, Jijia).
4. CURRENT ISSUES ON GEOMORPHOLOGICAL PROCESSES
Movements of land shapes alike foreheads terraces and slopes of the interfluves . They are
facilitated by the geological, hydrogeological, climatic, lithological, morphological and
anthropogenic influence.
This process contributes to redistribution of the masses of land semi-dynamics and
dynamics with various thickness as well as the separation of the rock in situ, at the same time
making the transfer to the axis of the drainage of huge amounts of diluvial. Overall, we are dealing
with local reactivation of older colluvial masses, but there are cases when gravitational process are
very recently activated (Fig. 6).
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Wingspan most significant have landslides mainly located in the lower half of the slope,
where implies otherwise normal erosion , whether it Jijia or its tributaries. Dynamics, morphology
and thickness of colluvial are varied in relation to the specific geological substrate, with slope land,
vegetation cover, human activities and other factors. Some deluvial fragmented form steps (with
rotational movements), others form mounds or waves or mixed form. Bodies slided occupies the
triangular or cvasicircular shape, and linear or slightly sinusoidal surfaces (isolated cases), the latter
being own to deluvial plastic or streams, formed under conditions of temporary water excess
(Posea, 2005).
Field observations indicate that deluvial thickness varies, usually between 2 and 5 to 7 m
and by entwining of deployed bodies were formed extensive aprons, sometimes by thousands of
sqm (eg: Miletin, Sitna, Başeu basins) (Bacauanu, 1968).
Fig. 6. Current geomorphological processes in the bank of Prut belonging Iasi county
(Photo source: F. Vartolomei)
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Many reactivation are regressive propagate (delapsive type) and are caused by disruption of
riverbanks or bank-slope, a situation that appears to generalize across the Prut valley. In torrents
cases, deluvial so reactivated manage to temporarily obstruct bed of collector river, as often
happened on the Prut tributary valleys in Iasi county. Although relatively rare, we meet shallow
lenticular, elongated, lobed or circular landslides. Some are grouped by area of several hundred of
sqm in Bahlueţ, Volovăţ and Sitna basin. Picture of mass movements enriched with subsidence and
collapse, processes that rarely intermingle. They employ both deposits in relative balance and layers
of rocks in place. The most common situations characterized steep banks and slopes strongly
sloping hillsides (Prut, especially between Corogea river and the confluence with Jijia) and flysch
cliffs of detachment sliding, not exempt any edges of terraces (Fig. 6). Individualization badlands
sites show current morphodynamics paroxysm relief under the joint action of a plurality of
processes favored by many factors. "Bad lands" are exemplified in many parts of the Prut basin,
especially the Moldavian Plain (Fig. 7).
Fig. 7. Surface erosion processes and their effects in Prut basin
(Photo source: F. Vartolomei)
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Landform visible changes from one month to another and especially in early summer, when
mass movements appear to be the maximum dynamic, more relief microforms, whether it is
increasing or even disappear more and more from alluvial material composition roofs is moved Prut
river bed. In a word, it is pronounced reactivation process that imparts a highly accelerated
evolution of the slope.
5. CONCLUSIONS Lately syntheses and generalizations conclude that meadow steps with altitude below 5 m
are Holocene age and terraces between 5 and 40 m are upper-Pleistocene age. Floodplains were
formed in the Holocene age, but have been remarkable changes in the contemporary period, when
the degradation is very obvious.
The dimensions of terraces will vary depending on the size of the river, having width of a
few tens or hundreds of meters, in tributarries cases and up to 5-10 km and even more in the middle
and lower Prut basin. Increasing silt downstream thickness from 2-5 m to 30-40 m in the Prut
floodplain.
REFERENCES
Băcăuanu, V., 1961, Observaţii geomorfologice asupra văii Prutului dintre Rădăuţi şi Stânca-
Ştefăneşti, Analele Şt. ale Univ. “Al. I. Cuza” din Iaşi, seria II, Ştiinţe Naturale, Fascicola 2, p.
433-440, Iaşi;
Băcăuanu, V., 1968, Câmpia Moldovei-studiu de geomorfologie, Editura Academiei, p. 163, p. 176-
177, Bucureşti;
Băcăuanu, V., 1973, Evoluţia văilor din Podişul Moldovenesc, Realizări în Geografia României-
Culegere de studii, p. 227-235, Bucureşti;
Băcăuanu, V., Barbu, N., Pantazică, Maria, Ungureanu, Al., Chirac, D., 1980, Podişul Moldovei -
Natură, om, economie, Editura Ştiinţifică şi Enciclopedică, p. 98-129, Bucureşti;
Bogdan, Octavia, 2007, Caracteristicile precipitaţiilor din sectorul vestic al văii Prutului
(România), Studii şi cercetări de Geografie, Editura Academiei Române, tom. LI-LII/2004-
2005, p. 13-28, Bucureşti;
Muşinschi, V., 2000, Terasele Prutului, Revista Geografică, Studii şi cercetări de Geografie,
Editura Academiei Române, tom. LI-LII/2004-2005, Bucureşti;
Posea, Gr, Cruceru, N., 2005, Geomorfologia generală, Editura Fundaţiei România de Mâine, p.
154-189, Bucureşti;
Tufescu, V., 1946, Confluenţele şi formarea luncilor Siretului şi Prutului, Revista Geografică,
ICGR III, , Bucureşti, p. 76-98;
Vartolomei, F., 2003, Graniţele pe ape ale României, Revista Forţelor Terestre, Nr. 1 din 2003, pag.
66-71, Bucureşti;
* * Bază de date în format GIS, www.geo-spatial.org;
* * www.gisdevelopment.net/glossary.
* * http://www.eea.europa.eu/