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Chapter - I INTRODUCTION In the annals of Peninsular India, geologically a significant catastrophy engulfed about 1/3rd of the land area at the end of cretaceous era. The so called catastrophic event was manifested in the form of outpouring of enormous volume of Basaltic lava that covered hundreds of square km. of the land through spasmodic eruptions which gave rise to piles of lava flows. These piles carved the Landscape of Deccan Plateau. The term Deccan Trap was first introduced by W.H. Sykes in 1833 after Swedish word Trapp / Trappa meaning stair to describe step like or terrace like formation (Fig.1.1). This is the second most extensive geological formation after Igneous and Metamorphic complex of Archaean era in Peninsular India (Fig. 1.2). It occupies a large tract between Bombay in the west, Cutch in North West, Sarguja and Jashpur in the East, Belgum in the south, and as far as Rajmahendri in South East, covering parts of states of, Maharashtra, Gujrat, Madhya Pradesh and Karnataka. Major part of Deccan Plateau in Maharashtra runs through Kelod, Nagpur and Pandharkawada in Vidarbha, East of Nanded, Deglur, Udgir and Umarga in Marathwada and East of Akkalkot and Miraj in Southern Maharashtra. In the West, Deccan Trap extends far beyond West Coast up to Bombay high and even beyond that. In Ratnagiri off shore Deccan Trap has been encountered in deep drill wells (Kalia 1988). Except Eastern part of Nagpur district, whole of Bhandara, Chandrapur and Gadchiroli districts and southern part of Sindhudurg district, all other districts of Maharashtra are occupied by Deccan Trap. Thus Maharashtra can be considered as house of Deccan Trap. Wadia (1967, p.292 p.301) and Krishnan (1968, p.407) have advocated perfect horizontality of DeccanTrap Basalts.Crookshank (1936, p.277) has mentioned deviation from horizontality near Morghat. However these cases are not of Basalt to Basalt contact, but they represent the contact between Deccan trap and Gondwana rocks.Wadia (1967, p.294) has attributed deviation from horizontality at Rajpipala hills and other areas to the disturbances subsequent to consolidation of flows. (1) Fig.1.1: Distant View of Deccan Trap Basalt Flows. Fig. 1.2: Area covering Deccan Trap formation. (2) The Deccan Traps are made of layers of several lava flows with thickness of individual flow ranging from few meters (7m) to as much as 40m maximum and can be traced for a distance of 20 Km. (Karmarkar-1974, Gupte et.al.1974). In Jawahar–Igatpuri section in Western Ghats about 700m thickness is reported to be composed of 15 flows (Subbarao et.al 1988). On the western slope of Sahyadri between Kasara and Kalsubai, 21 flows are exposed in vertical span of 1381 m. From Poladpur to Mahabaleshwar within a vertical distance of 1200 m there are 47 flows. Compound flows of amygdaloidal basalts range in thickness from 30m to 200 m. The total thickness of Deccan Trap is also variable in different parts because of undulating nature of ground over which the flows are overlying. The trap cover is thickest near Bombay coast, where it is almost 3000 m.The section at Matheran is about 850 m thick, at Mahabaleshwar it is 1700 m thick. The Lava pile in Western Ghat is having combined thickness of 2500 m. In Melghat scarp, north of Achalpur in Amravati District the flows have total thickness of 700 m. In the Eastern part of Vidarbha total thickness varies from 70 m to 225 m. At Hingana in neighborhood of Nagpur, in bore holes drilled for coal prospecting thickness of traps has been found to vary between 50m to 70m. The lava flows of two different types have been recognized. They are pahoehoe or ropy lava and the aa or block lava. Pahoehoe is mobile, solidifies with smooth and glazed surface have rope like wrinkles hence called as ropy structure. The flows are also recognized as compound (Amygdaloidal) when made of several smaller units. Karmarkar et.al. (1974), called such flow units as Thin and Thicker irregular Amygdaloidal Basalt Flows, as each unit possesses criteria of demarcation of flows with irregular top surface. Simple flows are uniform over large area and made of single units. In general compound flows show Pahoehoe characters, whereas simple flows show characteristics of Block or aa flows. The former predominate in western Maharashtra between Dhule, Buldhana, Aurangabad, Pune and Nasik whereas in the rest of the region of Maharashtra Simple flows are predominant (Fig. 1.3). (3) The Compact Basalt flows are Thick extensive and free from vesicles, amygdales, except for small portions at the top and bottom of the flows. The major portion of these flows is jointed. The undulated Basalt flows having vesicles are called as Vesicular Basalts (Compound Flows). However these vesicles rarely remain empty but are generally filled with secondary minerals like varieties of silica, calcite, zeolites and these vesicular Basalts containing infilling of the secondary minerals are called as Amygdaloidal Basalts. In nature therefore Vesicular Basalts are rare in occurrence and Amygdaloidal Basalts are more. As mentioned earlier many of the amygdaloidal flows may be made of several smaller units forming compound flows. Kulkarni P.S. (1985) demarcated various flows in different ghat sections of NE and Central part of Maharashtra, e.g. Buldhana Ghat section-10 flows, Mhaismal Ghat section-17 Flows, and Nagapur Ghat section-18 Flows, etc. Tejankar (2002) studied the basalt flows along Toranmal section of Western Satpura region and concluded that Toranmal section exposes maximum thickness of Deccan Basalt in the Western part of Satpura range comprising 50 Basalt flows within a vertical pile of 787 m, lying between 348 m and 1135 m above MSL. These flows represent Quartz and Olivine normative Tholeiite Deccan Trap flows have horizontal attitude which can be observed along Western ghats and in the areas of Khandesh to Solapur and throughout Vidarbha region (Fig. 1.4). However in the regions like Mumbai and Salsette islands and in the hills between Thane and Kalyan and west of panvel the flows show dip varying between 8° and 12° towards west. In some areas very low dip between 2° to 5° is observed which may be due to slope of original land surface on which lava is outpoured. A study of Land-Sat imagery carried out by Rajurkar et.al. (1990) has revealed several lineaments traversing Maharashtra Plateau (Fig. 1.5). This study is summarized in Table No. 1.1. (4) Fig. 1.3 : Regional Distribution of Basalt Flows Fig. 1.4 : Panoramic View of Basalt Flows exposed in Chikhaldara Ghat section (5) Lineament Sahyadri Chiplun Warna Ghod Upper Godavari Kaddam Lineament Tapi Purna Sr. No. 1 2 3 4 5 6 7 8 200 Km. long from south of Amravati up to Jalgaon in west where it joins Tapi lineament 1200 Km. long extending from vicinity of Jalgaon in west to Dhanbad in Bihar in the East 280 Km. long West of Nasik up to neighborhood of Parbhani 280 Km. long 225 Km. long 100km length Mumbai to Ratnagiri 50 Km. wide Extent (6) WNW-ESE Northern border of Maharashtra (Course of Tapi River) Course of Kaddam River WNW-ESE NW-SE (Course of Ghod River) NW-SE (Course of Warna River) NNW-SSE Parallel to west coast Direction Remarks Towards east it possibly continues up to south east of Nagpur and further east to join Balaghat lineament It represents Achalpur fault which is along the southern foot of Gawilgad hills. The fault was recorded by Blanford in 1869. In Yavatmal district Basalt flows show dips towards north along this line which has been considered due to faulting. Shows evidence of Quaternary Tectonic movements. Set of fractures observed in the Basalts of this region. In North West part faulting is suspected along this lineament. Represents fault in Achaean basement below and was reactivated in post Deccan Trap period Marked by presence of hot springs The lineament is mainly represented by fractures and dykes. No evidence of faulting Table No. 1.1: Lineaments Traversing Maharashtra Plateau These lineaments throw some light on the nature of tectonic activity in the region. The Tapi lineament, which form southern margin of Satpura horst represents a zone of weakness along which there has been recurrent activity during different geologic periods, as is evidenced from the inliers of Achaeans and Gondwana rocks in the Deccan Trap and thick alluvial deposits of quaternary age in the Tapi and Purna valleys. The crustal block, south of Tapi Purna lineaments comprising the Maharashtra plateau appears to be tectonically a stable block forming basement for Pakhal, Sullavai, Penganga and Gondwana sedimentary sequences and thick Deccan Trap lava pile. The Godavari lineament of Pranhita Godavari valley has controlled formation of these basins and their sedimentation. The faulted margins of these basins indicate that some of the lineaments are fault lineaments which had recurrent activity during different geological periods. Over the Maharashtra plateau, in addition to NNW to NW trending Godavari lineaments, there are dominantly ENE-NE trending lineaments which represent cooling joints and fractures in the lava flows with no tectonic significance. The Godavari lineament occurring in the trap flows appear to be manifestations of the basement lineaments, the activation of which in post Deccan Trap period is observed in Warna and Kaddam. Although some evidences of recurrent activity have been observed in the case of some fault lineaments in the Maharashtra crustal block south of Tapi-Purna lineaments, the block as a whole appears to be tectonically stable. (7) (8) Fig. 1.5 : Major Lineaments of Maharashtra (Source CGWB Nagpur) Literature Survey:Deccan trap is major geological formation occurring in peninsular India, covering an area of about 516000 Sq. Km. in western and central part of India (Fig.1.2), about 82% of Maharashtra state (Fig.1.3). After independence observations which have been made during geological investigations by experts for engineering sites in various parts of Deccan trap area and for ground water exploration in drought prone areas have revealed that there is considerable variation in its field characters which have not been mentioned by earlier workers. These observations have initiated the government organizations like GSI, ONGC and a few Geology Departments at University and College levels in Maharashtra state to undertake further studies which were mainly confined to Geochemical studies of Basalts. The literature survey shows that the earliest work on Deccan trap was of Capt. Danger field (1824), who prepared geological map showing outcrops of basalts of Malwa plateau of Madhya Pradesh. Subsequently a valuable contribution was made to the knowledge of Deccan Trap formation by Blandford who studied Deccan trap formation of western India (1856), the geology of Taptee and lower Narbada valley (1869), The Geology of Nagpur (1872) and Geology of Mahabaleshwar (1921). Holland (1892, 1906, 1908-1909), Fermor and Fox (1916) and Fermor (1926, 1934) have also made significant contribution in the studies of Deccan Trap. It was for the first time Washington (1922) has studied petrochemistry of the traps. Subsequently Mathur and Naidu (1932), Mathur (1934), Vemban (1947), Auden (1949), Sukeshwala (1953), Sukeshwala and Poldervaart (1958) and A.C. Chatterjee (1961) have published papers on Deccan trap and associated formations. Agashe, L.V. (1956) studied dykes between Pune and Khandala. Agashe L.V., Gupte R.B. and Deshpande M.G. (1964) studied volcanic vents of Alandi and Charholi and published in College of Engineering Poona Magazine. Beane, J.E. and Hooper P.R. (1988) published a note on picrite Basalts of Western Ghats, Deccan traps, India, in Deccan Flood Basalts, Mem. Geol. Soc. of India, No.10 pp. 117-134. Beane J.E., Turner C.A., Hooper P.R., Subbarao K.V. and Walsh J.N. (1986) published a paper on Stratigraphy, Composition and form of Deccan Basalts, westrn ghats, India, in Bulletin, Volcanologique, volume, 48 pp. 61-83. Bodas M.S, Khadri S.F.R. and (9) Subbarao K.V. (1988) studied stratigraphy of Jawahar and Igatpuri formations and published in ‘Deccan Flood Basalts’ Geological Society of India, Mem.10, pp. 235-252. The paleomagnetic studies of Deccan trap basalt flows and dykes were carried out by Sahasrabuddhe et.al. (1963), Athawale et.al. (1970), Pal and Bhimsankaram (1971), Wensink and Klootwijk (1971) and Wensink (1973). The work on tectonic aspects of Deccan trap was also carried out by Krishna Brahmam and Negi (1973), Bakshi A.K. (1994) carried out Geochronological studies on whole rock basalts, Deccan Traps; India. Mahoney et.al. (1985) carried out an isotopic investigation of some alkalic and tholeiitic basaltic lavas in the northern Deccan area along the Narmada River. These lavas are essentially contemporaneous. Mahoney et.al. determined that the alkali and tholeiitic lavas have similar isotopic composition and are roughly equal in volume in that particular Narmada section. Although it has long been known that the Deccan Trap lavas are predominantly tholeiitic, Mahoney et.al. justifiably wondered whether other unexplored areas of the Deccan might be found, where alkalic basalts occur in insignificant volumes. Devey C.W. and LightFoot P.C. (1986) worked on volcanological and Tectonic control of stratigraphy and structure in western Deccan Trap (Bull. Volcanology, v. 48, pp. 195-207). Duncan R.A. and Pyle D.G. (1988) published paper on “Rapid eruption of Deccan Flood Basalts at the cretaceous tertiary boundary in “Nature” (vol. 333, pp. 841-843). Ghosh Pradip K. and Pal R.N. (1984) have given evidence of Fissure eruption observed in Khargone and Dhar Districts (GSI spl. publ. No.14 pp. 108-110). Jeffery K.L., Henderson P., Subbarao K.V. and Walsh J.N. (1988) studied distribution of Zeolites in Deccan Flood Basalts (Geol. Soc. of India, Mem.10. pp. 151-162). Kalia K.L. (1988) mapped thickness of Deccan Trap basalt Flows in India from DSS studies (‘Deccan Flood Basalts’ Geol.soc.of India Mem. 10, pp. 91-116). Khadri S.F.R., Subbarao K.V., Hooper P.R. and Walsh J.N.(1988) worked out Stratigraphy of Thakurwadi formation, in Western Deccan Basalt Province. (“Deccan Flood Basalts”, Geol. Soc. of India Mem.10 pp. 281—304). Recent (10) investigations carried out by Raman and Subbarao (1994) have indicated rare element partial melting model and its petrogenetic significance in Deccan Traps. Subbarao et.al. (1994) have given stratigraphy and structure of Central Deccan Basalt Province and proposed various eruptive models which appear to have been originated due to iso-static adjustment. Khadri et.al (1996) have proposed stratigraphy, form and structure of east Pune Basalts and reported the occurrence of new pyrite basalt horizons in Wai sub groups. On the basis of Geological and Geophysical evidences ,West (1959) stated that the Deccan trap flows originate in those areas where dykes are found, namely in Cutch, Saurashtra, North Konkan, The Tapi and Narmada valleys and the Gondwana basins of Satpuras and further east and they travel long distance to other parts of the outcrop. The first Paleomagnetic measurement on Deccan Traps was carried out by Irving (1994). The next detailed work on Deccan Trap samples from Khandala and Linga areas by a group of British Scientists (Clegg et.al. 1956). A group at Osmania University, Hyderabad carried out paleomagnetic investigations on Deccan trap from a few different localities (Pal et.al. 1971). Verma and Mittal (1972, 1974) studied Deccan Trap of mount Girnar and mount Pavagarh areas with respect to paleomagnetic aspect. Normal-Reverse-Normal paleomagnetic sequence was reported by Sreenivasa Rao et.al. (1985) in the Narmada region. While the above extensive studies of Deccan Traps were completed or were in progress by overseas groups, Japan (Keno et.al. 1972) and France (Courtillot et.al. 1986). Sano et.al. (2001) describes differentiation processes of Deccan Trap Basalts based on Geochemical and Petrological studies. He further stated that the Phenocryst assemblage and Chemical Trend of the least contaminated basalts can be explained by fractional crystallization in shallow chambers under Faylite–Magnetite-Quartz (FMQ) buffered conditions.Mudholkar (2001) studied the magnetic evolution of the fresh Basalts from the ridge axis near Egaria fracture zone, Central India ridge, on the basis of Geochemical and Petrographic studies. The origin of Deccan volcanic province has been much debated. The debate concerns whether the magmas formed by melting a giant mantle plume, Normal Plate tectonic processes or impact of large extra terrestrial bollide (e.g. (11) Mahoney 1988, Richard et.al. 1989, Chandrasekharam and Parthsarathy 1978, Chatterjee and Rudra 1992, Sen 1995, Seth 2005 a, b). In the 1960 several authors recognized the difficulties in explaining all volcanic phenomena on Earth with the shallow mantle melting model required in the plate tectonic theory and proposed the concept of hot spots (Wilson 1963). Wilson felt that the Hawaiian island chain, which is located in the middle of large oceanic plate, could not be explained by shallow mantle processes required by Plate Tectonics. Wilson model for the Hawaiian volcanic chain called for generation of magmas from a spatially fixed thermal plume rooted in the deep, non convecting mantle. Soon after Wilson, Morgan (1972) presented concept of mantle plumes. Whereas hot spot sensustrictorefers to a hot jet or thermal plume, Morgan’s plume would include material transfer from deep to shallow mantle. In the subsequent years, geochemists and geophysists have used the term “plume” at random to mean different things; but in general, “Plumes are upwellings and downwellings that are maintained either by thermal or chemical buoyancy or by both in concert” (Anderson and Natland 2005). The Deccan Traps eruption is often used as a spectacular example of mantle plume activity (Richard et.al. 1989; Duncon and Richards 1991). The basic idea is that the Deccan magmas formed by melting a giant “plume head” that rose from the core mantle boundary. This plume head was anchored to the source by long tail that created the Chagos-Laccadive volcanic chain. A jump of a ridge that is now the Central Indian Ridge about 40 million years ago broke up the chain and the original plume tail is now creating volcanism on Reunion Island. There are several authors who have doubted the plume theory as far as the origin of the Deccan Trap is concerned (e.g., Seth 2005a). Chandrasekharam and G. Sen and D. Chandrasekharam, Parthsarathy (1978) noted that Deccan Basalts predominantly erupted through fissures in the crust and proposed a model of shallow mantle melting in which pre existing rift zones were reactivated and magma simply poured out of fissures (Chandrasekharam and Parthsarathy 1978). An important argument in favor of the plume origin of the Deccan is that too much lava came out in too short a time requiring some special melting mechanism that does not fit the normal Plate Tectonic schemes (Sen, 1995). (12) Much finer age refinement with radioisotope dating of the lavas and a more accurate estimate of the volume of the lavas are needed to have a stronger constraint on the eruption rate of the Deccan. Without such refinement, the mean eruption rate could have varied between 1 and 40 Km3 per year. A paleomagnetic study by Chenet et.al. (2007) suggests that there were episodic bursts of lava eruption with intermittent quiescence. Considering the research of the earlier workers, in the present investigation the attempt has been made to decipher the nature of volcanicity that has produced basalt flows in time and space. Most of the workers attributed Deccan Trap as the product of fissure type of volcanicity, but Agashe and Gupte (1968, 1971) have shown that in addition to fissure type, central type of volcanicity also existed in some part of Deccan Trap area of Western Maharashtra. Subsequently on the basis of systematic studies of the field characters of basalt flow exposed in road cuts and in railway cuts taken for ghat sections from R.L. 40 m to R.L. 1220 m over a large area of Deccan Trap formation Gupte et.al. (1971), Karmarkar (1974, 1978) Kulkarni S.R. (1975) Marathe (1976, 1980), Kulkari P.S. (1984) and Tejankar A.V. (2002) have shown that there is distinct variation in the nature of volcanicity at different times and at different places in Western Maharashtra, Marathwada and Khandesh region of Maharashtra state. Hence the present work is concentrated on these lines for Vidarbha region of Maharashtra state. Area of Present investigation:In the present investigation attempt has been made to determine nature of volcanicity in the north-east part of Deccan Trap formation i.e. Vidarbha region of Maharashtra. The area selected for the investigation is Ghat section known as Chikhaldara Ghat in which basalt flows are clearly exposed in the approach road to Chikhaldara Hill Station ( R.L. 1092 m) and hill ranges 77˚ 19' North 21˚ 24' East. The Chikhaldara ghat section is situated at a distance of 100 Km. North West of Amravati. It is approachable by all weather road from Amravati (Fig.1.6). There is Melghat Tiger Reserve forest on this hill station. (13) (14) Fig No. 1.6 : Location Map of Chikhaldara The Methodology of Investigation:A) Study of field characters of Basalt flows:As shown by the earlier workers (Gupte 1974), Karmarkar (1974, 1978), Kulkarni S.R. (1975) Marathe (1976, 1980) , Kulkarni P.S. (1984) and Tejankar A.V. (2002), who gave more stress on the field studies of the Basalt flows which can give clues to the nature of volcanicity. Therefore much stress has been given to the studies of field characters of basalt flows exposed in the Chikhaldara Ghat section (Fig. 1.7). For this purpose traverses were taken from the foot of the ghat (R.L. 600 m) up to Chikhaldara hill station (R.L. 1092 m) during four summer seasons between 2006 to 2011, when road cuts remain free from cover of vegetation and moss. During the field work individual basalt flows were demarcated and traced in the cuttings along the road to determine their extent, thickness and field characters. The vertical variations from top to bottom of each flow were critically studied. Wherever possible the vertical thicknesses of the basalt flows were actually measured. On the basis of demarcation of the basalt flows their chronological sequence in the vertical stretch of 492 m is depicted. B) Petrographic studies:To determine mineralogical and textural variation in basalt flows a large number of specimens from the basalt flows were collected and their thin sections examined under petrological microscope. Critical observations of about 150 thin sections were carried out to determine mineralogical and textural characters of the flows (Fig. 1.9). The relative proportion of different minerals by volume in basalt flows was determined by Dalesse-Rosiwaal method. Anorthite content of plagioclase phenocrysts was determined by Michael Levy method. C) Chemical studies:Suitable specimens from the flows have been chemically analyzed. The major element-oxides content, Trace elements and also rare earth elements of sixteen basalt flows were obtained by utilizing facilities available at National Institute of Oceanography Goa. The results of these analyses are utilized to (15) determine chemical variations in the basalt flows occurring in the area studied. Attempt is also made to determine nature of the magma. These results are compared with the chemical characters of basalt flows occurring in other parts of Maharashtra state. Fig. 1.7 : Basalt Flows of Chikhaldara (16) Previous work:In the area of Chikhaldara Ghat Section very little work in this problem has been carried out. However the work on the similar lines has been carried out in different parts of Deccan plateau. Preliminary petrographic and paleomagnetic studies of lava flows around Boral region Chikhaldara plateau, Amravati district MS, carried out by Dr. S. F. R. Khadri (SGB Amravati University Journal Vol: 3(1), 2008). Rock magnetic and palaeomagnetic investigations of lava flows around Chikhaldara plateau Amravati Dist. (MS Journal Geological society of India). A brief reference of the Geology of the district is made by Blanford (1869), pertaining to the Geology of the Taptee and Narmada valleys and some adjoining districts, wherein salient features of the southern parts of the Gawilgarh range and the Purna plain are outlined. The main aspect of this thesis is to decipher nature of volcanicity that has produced basalt flows and has been discussed at length. Marathe S.S. (1976) studied petrology and structural peculiarities of the Godavari valley Basalts near Nasik. He had reported 27 dykes exposed in the vicinity of 2.5 to 3 Km. from Right and Left bank of Gangapur Dam. He discussed their influence in topographic expression. Karmarkar B.M. (1973) noticed 85 fractures in 20 Km. stretch of Borghat section along Pune–Mumbai railway track and in Tunnels from Khandala to Karjat. Basalt flows show closely spaced jointing pattern around these fractures. Kulkarni P.S. (1985) studied different Ghat sections of Central Maharashtra. He had correlated various flows exposed in these Ghat sections and concluded that the sequence of flows in all these ghats are different. This means that the flows building up one ghat have not reached the neighboring ghat, even 18 Km. away from each other. Chande D.G. (1986), on the basis of field and laboratory studies showed that out of 28 dykes located in Gangapur–Vaijapur area 21 dykes are of Compact Basaltic nature while remaining seven dykes are of Amygdaloidal Basalt. The dykes of Compact Basalt further show field evidences of their feeder and hypabyssal nature. Out of 21 dykes of Compact Basalt, 13 (17) dykes are showing their feeder nature and remaining 8 dykes are hypabyssal injections. Anirudha De (1996) studied Deccan Trap lava flows in Satpura and states that these are simple lava flows characterized by several zones of primary volcanic structures. Subbarao (2000) studied the basalt flows with reference to their rare earth elements and concluded that “Sr” isotopic ratio for the tholeitic spilite flow and associated mineral phases which can provide direct evidence for spilitic degradation of tholeiites and increase in rare earth elements from basalt to spilite. Ray and Bose (1996) concluded that the genesis of Deccan Basalt has been considered to be a two step process involving major petrogenetic problems. The primary state in the generation of magma type with distinct geochemical characterization, where as the second stage involves contamination. Godbole (1996) studied Geology and Chemical stratigraphy of the Basalt Flows of Akot Harisal section from Satpura range of Amravati District. Deshmukh (1996) carried out geochemical studies of Basalt Flows exposed at Chikhaldara and Bairamghat area and on the basis of vertical variation in chemistry of basalt flows the Lava pile is divided into five and four groups respectively. These groups are separated by chemical marker flows. Flows present in these areas show chemical affinity to Ambanali formation.Chatterjee (1996) carried out petrographic and Geochemical studies of Narmada-Tapi-Satpura dykes system between 74° and 76° longitudes of Central India. Bulk of these dykes is of Basalt and dolerite with intermediate and acidic dykes being scanty. Chawade (1996) studied the petrology and Geochemistry of dykes in Deccan Basalts in parts of Lower Narmada valley. Keshav (1998) reported the field Geology and Petrography of greater than 40 Km. long East-West trending Dhule-Parola dyke of Southern Tapi Rift. Sethna (1996) studied Petrology of the basic dolerite dykes around Nandurbar area, south of Tapi River and observed that these dykes contain large amount of Pigeonitic pyroxene, which is not so common among dolerites encountered along the west coast part of the Deccan Volcanic Province. Sengupta (1996) studied Petrology and Geochemistry of Deccan Trap flows intersected in Salbardi drill hole near Salbardi hot spring in Amravati (18) District. The drill hole intersected 604 m thick basaltic lava pile comprising 26 flows. The Basalt sequence is underlained by Lameta sediments. The basaltic flows of this area are of simple type and range in thickness from 4 m to 75 m. They are Porphyritic in varying degree (5% to 22% phenocryst) set in ground mass of plagioclase, clinopyroxene, opaque, glass etc. Further he also divided the lava pile in to three stratigraphic units on the basis of vertical variation in Chemical characteristics and shows the close compositional similarity of these units with Ambanali and Mahabaleshwar formations of Western Deccan Basalts. Venkata Rao (1996) carried out Paleomagnetic studies along five sections in the Western Sempra region and showed that the Shahada–Toranmal section at western edge has given R-N-R polarity pattern with the flows above 900 m height showing random directions. The basalts along Eastern part of this sector along Paratwada-Chikhaldara section, reveal transitional directions at lower elevations and reverse polarity flows above. James Peter and Sing (2001) studied Satpura basin and stated that Satpura basin could be considered in terms of Pre- rift, synrift, and post rift phases of Gondwana sedimentation. (19) (19)