A. Physiography the Two Major Geographical Regions Of
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PART I : THE ENVIRONMENT A. Physiography The two major geographical regions of Maharashtra are, the Konkaa or coastal tract and the Desh or plateau region. They present a striking contrast to each other in terms of physiography, vegetation and climate - the three environmental ractors, urbicb to a greater or lesser degree, influence cultural development. The present study is concemea with the Konkan (Fig.lj which stretches from the Damanganga river in the north, to the Terekhol river in the south. This region is some 530 km long and 30-50 km wide between 20^ and 16® N. Latitude and 72® 40* and 73® 55* B. Longitude. The whole, is divided into several administrative districts of which Thana, BomDay, Kolaha, Katnagiri and bawantwadi are referred to in the present study. Physiographically the Konkan can be diviaed into three more or less parallel zones : 1. Eastern - The Sayhadris (or western Ghats) form the vertebral column of Maharashtra (Fig.i), with arterial drainage flowing both to the east and to the west. In the sub->Sayhadrian tract, the transverse ridges of the Ghats extend westward, producing an appearance of general ruggedness characterised by bare rocky expanses. These denuded, bevelled surfaces, suriaouated by Isolated hills stand out in direct contrast to the thick monsoon forests on the Ghats. 8 The foothills are thinly populated, economically backward and villages are concentrated along the main river courses and at the base of the Ghat passes. 2, Central > To the west of the eastern zone, the landscape, in Ratnagiri district widens into gently undulating plateaus, while in Kolaba district, the outliers of the Ghats are higher (sometimes rising to 600 m) and are more sharply outlined than in the other districts. This is the zone where the rivers enter the plain and wJiere their courses are characterised by meanders as they wind their way among the isolated hills and the transverse ridges of the Ghats. 3* Western - Mainly because they tend to interfinger, the actual line of demarcation between the central and western zones cannot be clearly defined. However, the point at which the rivers become tidal can be considered an effective boundary. There is a gradual opening out into the estuaries, which form the focus of human activity. On the coast, headlands alternate with bays giving this part of the coast its ria-like appearance (Pl. la ). These headlands might almost be said to constitute watersheds on a micro-scale. Characteristic features of the north Konkao are the sand spits merging with mud flats near the sea, (uid low coastal ranges alternating with longitudinal Talleys further inland. The south Konkan is rocky, rugged country with elevated plateaus and Intersecting creeks. The coastland gradually widens from north to south as the Ghats recede from the coast, but nowhere are there wide river plains, because the off-shoot ridges of the Sayhadris have restricted the spread of alluvium. The only large basin is that of the Ulhas river near Bombay. The 100 m contour stands out as a prominent topographic feature. It more or less separates the Konkan river basins from the hills and also separates these hills from each other. In the river valleys, the debris washed down from the Sayhadris by the monsoon torrents has created large shingle beds in the streams. Near the mouths of the silted estuaries, sandbars developed by marine activity, have blocked many of the rivers, so that the partially impounded waters spread out laterally to form swamps. In historical times this process has i rendered once-flourishing ports useless, for example Kalyan and Sopara. The crastllne of the Ghats varies from 600 - 900 \The peaks of maximum height (e .g . Kalsubai - 1,599 n) V.not always coincident with each other, nor does the wa^rshed between the east-west drainage always follow I the' Crestline. The latter has aptly been described (Spate \ and t«armonth, 196?) as a succession of high and low plateau iO tops (like Paachganl and Mahableshwar) which are connected by saddles and occasional rounded, isolated columns. The western Xlank of the Sayhadris is a fractured edge of the Deccan Plateau marked by a series of terraces typiced of the lava landscape. Geomorphologists (Spate and Learmonth, 1967; Dikshit, 19 71) are generally of the opinion that the Konkan appears to be a plane of marine erosion, the bevelled surfaces in the Deccan lava surmounted by isolated hills which look very much like old off-shore islands (Spate and Learmonth, 1967:643)* The drowned river valleys and submerged forests (e .g . at Bombay, Mangalore and Cochin) suggest subsidence on a macro-regional scale, probably followed by a period of stability to account for the development of sandbars and mangrove swamps. The Konkan is a land of contrasts: of hills and plains, wet and dry seasons, forests and cultivated valleys, bare rocks and laterite plateaus. 11 B. Geology The geological formations of the Konkan can be divided into four main groups (Fig. 2 ): 1. Pre-Cambrian metamorphics; 2. Cretaceous-Eocene volvanlcs, or the Deccan trap; 3. Tertiary laterites and submarine fossill- ferous sediments; 4. Quaternary soils, alluvia, laterites and littoral formations. 1. Pre-Cambrian Metamorphics These include the Peninsular gneisses, the Oharwarian schists, quartzltes, etc., and the indurated shales and quartzltes of the Cuddapah series. They are exposed only in south Ratnagiri district. Quartzltes and crush conglomerates occur as narrow bands almost parallel to the coast and show a steep easterly dip, while the banded haematite quartzltes and mica schists further inland have a northerly dip. These quartzltes have been used to manufacture Palaeolithic artifacts and are white^ pinkish and red-brown. They are also hard, compact and fine-grained. In addition, there are quartettes vhich are coarse-grained and friable and more akin to sandstone. Both types occur around Malvan. 2. Cretaceous-Gocene Volcanics The most conspicuous geological formation - the 12 Deccan Trap covers the whole of the Konkan with the exception of the southern part of Ratnaglrl district. The lavas are sub-horizontal and petrologically uniform in coraposition. These peninsular volcanic eruptions are believed to have begun at the end of the Cretaceous and to have ceased soioetlme during the Socene. On a limited scale, however, there has been a continuation of eruptive activity (possibly even in the late Tertiary or early (Quaternary) indicated by a few isolated lava flows seen to occur in the post-Miocene valleys in parts of Ahmednagar and Satara districts of upland Maharashtra (S.N . ftajaguru, personal conuauni- cation). The most common rocks are amygadaloidal, compact, porphyritic and agglomeratic basalts, and it is only around Bombay that acid traps occur. The latter show a gentle dip (l2^ - 15°) a little south of west (Sukheswula, 1953). The compact basalts are well Jointed and the master joints or fractures observed in the Ulhas valley for example (B.M, Karmarkar, personal communication), appear to have controlled the drainage of some of the tributary streams in this basin. The basalts are extensively traversed by post-trappean basaltic and doleritic dykes, particularly in the north Konkan. Inter-trappean shales and sandstones, at times 13 fossillferous, occur only around Bombay, e .g . at Worli (Sukheswala, 1953) and Utan (P I.l b ). Accessory minerals like Chalcedony, agate, calcite, magnetite, etc., occur as cavity fillings or veins in the basalt. Cherts are seen to occur as local siliceous segregates in the inter-trappean rocks in north liombay, for example, at Kandivli. These rocks have been used in the manufacture of Middle Palaeolithic and Mesolithic artifacts. 3. Tertiary Formations a) Laterite. The laterites can be divided into two groups, (i) Tertiary and (ii) Quaternary. They occur infrequently in the north Konkan, but comprise one of the prinncipal geological formations of Ratnagiri district. Laterite occurs at various elevations throughout the region (Pig. 3 ), ranging from 600 m to about 5 m above sea level. Occasionally, (e.g. at Borlai), the laterite is rich in bauxite. Essentially these formations are non-fossiliferous. The Ratnagiri laterites alone have been studied by the writer and are discussed in greater detail ahead (B.1-5). b) Suomarine fossiliferous sediments. Patches of blue and white clays have been reported (Vilkinson, 1871, 1872) lying on the weathered trap surface at Ratnagiri. Only a few meters thick, this clay contains imbedded fruit and thin carbonaceous seams composed for 14 the most part of leaves,' These beds are overlain by laterlte. Suryanaruyana (1970) has identified fossil fruit of the genus Terminalia and Nyssa. from a deposit near Kalinudi (Ratna^iri district). The fossils are associated with a post-trappean lateritised sediment comprising carbonaceous, pyritlc and ferruginous shales, with intercalated peaty resinous material. More plant fossil beds hare been recently discovered (K.R. Dikshit, personal communication). The writer has also exaotined one of these deposits excavated from a well section at Nandivde, JaygHd. Unfortunately, the fossil impressions were damaged during excavation and could not be identified, but a general description of the stratigraphy is given in Figure kh. These beds are believed to be homotaxial with the Cuddedore sandstones of late Tertiary age. 4 . Quaternary Formations These can be divided into five groups: a) coastal, b) alluvial, c) intermediate, d) slope deposits and e) soils. Of these, the first two are discussed in detail in sections I I . 6 and 8. c) The intermediategroup comprises estuarine and lagoonal muds and clays, which form a wide belt in the north Konkan and narrow down as one moves southward. The clays, generally bluish in colour, have variously been described as marine or alluvial. The influence of the tide which extends a number of km upstream, is pronounced, 15 so that what In other areas remains as purely alluvial soil, here becomes a mixture of aliuTium and marine clay, d) Slope deposits are noticibly rare in this region.