DISCOVERY OF EVIDENCE OF EXPLOSIVE HYDROVOLCANICS IN INTERTRAPEAN BEDS OF MADHYA PRADESH, INDIA
SIKDER, Arif1, DAS, Priyabrata2, PAUL, Sharmistha3, D'ORAZIO, Gabriela1, MAYER, Carl4, TURNER, Joseph B. McGee5, PESTOV, Dmitry4, VERMA, Vishal Gyaneshwar6, BISWAS, Partha Pratim7 and GANGOPADHYAY, Tapas Kumar3, (1)Virginia Commonwealth University (VCU)Center for Environmental Studies (CES), 1000 W Cary St, Richmond, VA 23284-9013, (2)Physical Research Laboratory, Council of Scientific and Industrial Research (CSIR), Government of India, Ahmedabad, VA 380009, India, (3)Department of Earth Sciences, Indian Institute of Engineering Science and Technology (IIEST), Shibpur Howrah, VA 711103, India, (4)Nanomaterials Core Characterization Facility (NCC), Virginia Commonwealth University (VCU), 620 West Cary Street, Richmond, VA 23284, (5)Virginia Commonwealth University (VCU), Department of Chemistry, 1001 West Main Street, Richmond, VA 23284, (6)U. M. Shikshak, Govt. Excellent School, Bakaner, Dhar Madhya Pradesh, VA 110011, India, (7)Dept.of Zoology, R.K.Mission V.C.College, Kolkata, VA 700118, India
The Intertrapean beds are thin sedimentary sequences, ranging between tens of centimeters to meters in thickness. These beds were deposited in the intermittent, apparently quiescent periods between two successive volcanisms and are sporadically exposed in isolated patches at widely separated geographical areas in the peripheral regions of the Deccan volcanic province. The present study was conducted in one such newly uncovered and well preserved intertappen beds in Gandhwani of Madhya Pradesh.
In contrary to the overall paleontological observation that the fossil species of the intertrapean varies from transitional marine to terrestrial, the geochemical signature of these newly exposed intertrappen beds show dysoxic to anoxic (i.e. Ni/Co>1, V/Cr>2 and U/Th>0.75) conditions prevailed with a strong marine influence (Sr/Ba ratio >0.5), during the formation of Gandhwani intertrapean sequence.
Mineralogical analysis revealed an rapid upward diagenetic changes of Celadonite [K(Mg,Fe++)(Fe+++,Al)[Si4O10](OH)2] to Nontronite [Na0.3Fe+++2(Si,Al)4O10(OH)2•n(H2O)], an Fe3 rich member of smectite, Celadonite is almost exclusively found associated with basic-eruptive rocks in deep-marine environments due to low-grade metamorphism, <250°C. On the other hand Nontronite is usually forms above the basalt on the seafloor at temperatures <70°C where hydrothermal fluids mix with sea water. Such a rapid change indicates sudden changes in overall geologic setting.
Finally the discovery of the Rhyolitic volcanic ash and Rhodonitic micro-lapillies in the middle of studied sections, which were concealed by several phases of alterations since it’s deposition in Late Cretaceous. indicates that the intertrapean may not represent a quiescent geologic period, but rather a violent episode full of proximal to distal explosive hydrovolcanism that was followed by basalt flooding, at the end of Cretaceous,
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