QUATERNARY TECTONICS & SEDIMENTATION NARMADA RIFT VALLEY CENTRAL INDIA

ABSTRACT The SONATA LINEAMENT ZONE embodies the two Quaternary basins of tectonic origin on the two margins of Sapura Crustal Block. The Satpura block traversed by enechelon system of faults and lineaments is characterized by thinner crust (33-38 km deep, basement depth >2.5 km) with series of ENE-WSW trending gravity high (viz. Sendwa, Khandwa, Chicholi, Tikaria etc.) with amplitudes of 10-35 mgal. The chain of gravity high indicates extensive magmatic and emplacement of derivatives at shallow crustal levels. The associated Narmada South (Satpura North) fault and Satpura South Fault marking the two hinges of the Satpura block are fundamental in nature and extend to Moho level. The Narmada Quaternary basin in the north and Tapti-Purna basin in the south are two Graben which formed prominent loci of sedimentation in lineament zone. The area of lineament zone studied tectonically encompasses two crustal provinces of Central India Shield, namely, the Northern Crustal Province (NCP) and the Southern Crustal Province (SCP). The two provinces are separated by a crustal level shear zone, referred as Central Indian Suture. The zone has been a major locus of episodic tectonism with evidences of reactivation. The Narmada Rift valley forms a ENE-WSW lineament where Quaternary deposits are confined in a trough like basin on unstable platform which forms a prominent lineament with profound geomorphologic and geological asymmetry between the northern and southern valley walls, giving it a tectonic significance. The alluvial deposits of the Narmada valley represent the thickest Quaternary deposits in peninsular India. These sediments were deposited in faulted and sinking platform under structural riparian rift trench remained silent and unrevealed. The quaternary blanket of Narmada consists of sediments of various domains which were deposited in different environment in vertical chronology in faulted trough in time and space. The Quaternary sedimentation in Narmada Rift valley incepting from glacial activity, followed by fluvio-glacial, lacustrine and fluvial phase within the rinsing and sinking environment, block faulting and linear displacement and dislocation, uplifting and isolated domal up- lift, Neogene rifting and Quaternary sedimentation. The rift-bound Pliocene–Pleistocene rifting and volcanic activities specifically during glacial and fluvio-glacial phase are major component of the Quaternary period and tectonic processes of the Rift System which form the base of quaternary deposits. The Narmada rift system basin platform provided a unique setting for dynamic ecosystems that were characterized by Rift-related subsidence and coeval sedimentation and environment for the accumulation of sediments volcanic fabrics sediments, burial, digenesis, and preservation of organic remains. The present disposition of Narmada blanket of Narmada, in SONATA LINEAMENT ZONE revealed that the rift occurred after widespread Quaternary sedimentation and accumulation of sediments in the linear trench by glacial activity in late Pleistocenc.The Fluvio-glacial phase is represents by boulder conglomerate which has formed the persistent horizon in the valley. The Narmada has in the area under study has sculptured the alluvial tract into stepped sequence forming four alluvial terraces along its course. These are designated as NT0 to NT3, NT0 being the youngest terrace and NT-3 the oldest terrace where the sub terraces are designated NT2-A is NT2-B, NT2 B, besides NT2-C, NT3-A & NT3-B in increasing order of antiquity. These are both erosional and depositional terraces and confined at an elevation of, between 280 to 380 are separated by the scarp both of curvilinear and linear in nature facing towards river side. These are abandoned flood plains represent the level of former valley floor in the area, and were formed by cumulative climato-tectonic changes in the watershed of Narmada in the Quaternary times Khan et.al (2016) The Jabalpur- Bharuch Harda section of Narmada possess the complete sequence of all three domain of sediments in increasing antiquity from the bottom of the rift trench, Boulder bed (glacial), Boulder conglomerate (fluvial-glacial) sediments of paleo-domain of Narmada (fluvial). The intense tectonic activities within the basins of the Narmada Rift System during the Neogene and Quaternary periods have destroyed fossil record except the fossiferous horizons exposed in river sections. The erosional-sedimentary cycle has persisted in the rift valley environment for millions of years as a result of the interplay between depositional and erosional forces driven by tectonic processes; there are numerous gaps in the fossil record, particularly in the important time period between Mio-Pliocene Pleistocene times. It is pertinent to the understand the origin of Hominid during the late Miocene, but it is difficult to disclose mysteries of human evolution in Narmada due to concealed nature of these deposits in rift system, however the complementary part of Tapti-Purna Quaternary blanket may be potential and possessive of human remain and should be studied to trace further the imprints of fossil man taking in to account of SONATA LINEAMENT ZONE as single ecosystem for evolution of man in Indian subcontinent. However, evidence of the effects of tectonics on fauna and flora are distinct and its signatures on dislocation and concealing of fossiliferous horizons are uncontrolled and ill-defined in the ecosystem in the valley during the Pliocene–Pleistocene periods. The boulder conglomerate which yielded the skull cap of Homo eructs in Narmada rift from Hathnora Sonakia (1984) remained only discovery of hominid fossil in last two and half decade due to concealed and hidden nature of Mio-Pliocene Pleistocene deposits in rift system and inconsistency in exposure of fosiliferous horizon due faulting, dislocation ad subsidence of Quaternary blanket of Narmada rift system. The Boulder Conglomerate which is of fluvio-glacial origin and has yielded human skull from Sonakia (1982) Khan & Sonakia (1992) is exposed impersistently in scarp section of Narmada at few places only. The type section of Boulder Bed and Boulder Conglomerate which are potential sediments of human remains of Pliocene Pleistocene time are hidden and concealed under sediments of present and paleo- domain of Narmada in the valley. The present study is a systematic attempt studies in Jabalpur _Bharuch section along the length of about 1300 Kms five critical and crucial section were selected across Narmada valley viz Jabalpur section , Hoshangabad section, Harda section, Gurudeshwar section and Bharuch section and about 310 samples were collected both from from exposed section and bore hole logs across the vertical column 210 m to regional modal of sedimentation, source of sediments, mode of transportation deposition tectonic environment of sedimentation and overall sedimentlogical aspects to conceive the model sediment in vertical chronology n faulted trough in time and space may provide clues in understanding the modal of quarter nary deposits and sedimentation. The Quaternary deposits of Narmada valley represent the thickest sequence which was deposited in faulted and sinking platform under structural riparian rift trench which remained silent and unrevealed. The work so far carried out is restricted to few exposed section of 18 m of river as such on work has been done on concealed strata of quaternary deposits The statistical parameters viz MZ, STD, SKI, and KG of sediment samples were computed from vertical column of 210 m of Quaternary blanket of Narmada. The synthesis of various parameters their binary relation, concentration of plots their pattern and trend revealed that the quaternary deposits consists of sediments of three mega lithostartigraphic units viz Boulder bed, boulder conglomerate and fluvial deposits. The fluvial deposits include sediments of paleo-domain of Narmada and present domain of Narmada which constitute fluvial terraces (NT1 to NT3) of Narmada. These three domains of sediments were deposited, from Pleistocene to Upper Pleistocene time in increasing antiquity in the valley. The study of statistical parameters and their binary relation distinctly display contrasting and relative heterogeneity in sediment characteristics throughout across the Quaternary blanket in Narmada valley. The study of sediments display diagnostic characteristics of glacial , fluvio-glacial and fluvial environment at different depth and levels 000.m to150, 150 to 350, and 350 to 550 m from glacial, fluvio-glacial fluvial , and fluvial deposit (150 samples). The critical analysis of these parameters exhibits sediment textural linkage to long evolution in glacial, fluvio-glacial and fluvial environment in time and space in increasing antiquity in the valley. The characteristics inherited by the sediments from pre-existing domain of sediments are glacial & terrestrial & environment. The digenetic and diagnostic features; varying degrees of heterogeneity, sediment angularity roundness, degree of sorting indicate evolution and sedimentation of quaternary sediments in a high-energy turmoil glacial environment on tectonically dislocated and unstable platform. The sediments confined up to 150 m below ground level represent paleo fluvial domain of Narmada and represent multi cycle sedimentation under varying energy condition on oscillating platform. The vertical variation in increasing antiquity in textural parameters and distinct breaks at specific level identified indicate changes of environments of sedimentation in vertical columns from glacial at the bottom of valley trough subsequently followed by fluvio-glacial and further overlain by fluvial deposits which is related with change of climate and tectonic in watershed of Narmada. The binary relation of these parameters effectively used in differentiating and fencing the sediments of these domains and their environment of sedimentation in time and space Khan et.al (2015). The study of statistical parameters across the entire thickness of Quaternary deposits revealed three breaks in sedimentation at 350 -290,190-220,100-150 which represent glacial, Fluvioglacial and Fluvial environment of in increasing antiquity in from bed rock in Narmada valley.