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Nagendra R.,Anna University | Sathiyamoorthy P.,Anna University | Pattanayak S.,Anna University | Nallapa Reddy A.,Majestic | Jaiprakash B.C.,Regional Geoscience Laboratory
Stratigraphy and Geological Correlation

The Karai shale Formation of the Uttatur Group is exposed in a bad land area at the western margin of the Cauvery Basin. This shale has been investigated based on foraminiferal fauna and clay minerals. The foraminiferal assemblages obtained contain predominantly calcareous benthic foraminifera, rare planktic and arenaceous foraminifera. The planktic foraminiferal index taxa Planomalina buxtorfi, Rotalipora reicheli, Praeglobotruncana stephani, and Hedbergella portsdownensis suggest the late Albian to middle Turonian age. The benthic assemblage dominated by Lenticulina, Gavelinella, Osangularia and Quadrimorphina, suggests an outer neritic (100-200 m) environment. The clay mineral content dominated by kaolinite-illite-montmorillonite indicates that the Karai shale was formed from weathering of igneous rocks. © 2013 Pleiades Publishing, Ltd. Source

Keller G.,Princeton University | Jaiprakash B.C.,Regional Geoscience Laboratory | Reddy A.N.,Regional Geoscience Laboratory
Journal of the Geological Society of India

Late Maastrichtian through middle Eocene planktic foraminiferal biostratigraphy and erosion patterns from three Cauvery basin wells are compared with the Krishna-Godavari basin, Madagascar and South Atlantic Site 525A. Maastrichtian sedimentation appears continuous at DSDP site 525A and substantially complete in the Cauvery basin and Madagascar for the interval from ~70.3 to 66.8 Ma (zones CF6-CF3). But the latest Maastrichtian through early Paleocene record is fragmented, except for some Krishna-Godavari and Cauvery basin wells protected from erosion by Deccan traps or graben deposition, respectively. Hiatuses are observed correlative with sea level falls at 66.8, 66.25, 66.10, 65.7, 63.8 and 61.2 Ma with erosion amplified by local tectonic activity including doming and uplift due to Deccan volcanism. Throughout this region the Cretaceous-Paleogene transition (magnetochron C29r-C29n, 66.25-65.50 Ma) is preserved only in deep wells of the Krishna-Godavari basin where Deccan Traps protected intertrappean sediments from erosion. The late Paleocene to middle Eocene marine record was recovered from two Cauvery basin wells with hiatuses correlative with low sea levels at ~49.0-56.5 Ma (zones P4c-E6) and ~53.0-55.3 Ma (zones E1-E4) at the ridge well KALI-H. A nearly complete record was recovered from well AGA, including the PETM event (zones E1-E2), which marks this an excellent reference section for India. Similarity in erosion and sedimentation patterns of the late Maastrichtian to middle Paleocene from India to Madagascar and South Atlantic is mainly attributed to climate changes and sea level falls, regional tectonic activity from the Bay of Bengal to Madagascar, and uplift and doming in the Cauvery and K-G basins as a result of Deccan volcanism. Directly correlative with Deccan volcanism are high stress environments for marine calcifiers, as observed by species dwarfing, reduced diversity and blooms of the disaster opportunist Guembelitria cretacea in magnetochron C30n (zones CF4-CF3) correlative with Deccan phase-1 and Ninetyeast Ridge volcanism, in C29r (zones CF2-CF1) correlative with Deccan phase-2 and in C29n (zone P1b) correlative with Deccan phase-3 marking volcanism as the most important stress factor in the end-Cretaceous mass extinction and delayed evolution of planktic foraminifera. © 2016, Geological Society of India. Source

Eller G.K.,Princeton University | Bhowmick P.K.,KDMIPE | Upadhyay H.,KDMIPE | Dave A.,KDMIPE | And 3 more authors.
Journal of the Geological Society of India

A scientific challenge is to assess the role of Deccan volcanism in the Cretaceous-Tertiary boundary (KTB) mass extinction. Here we report on the stratigraphy and biologic effects of Deccan volcanism in eleven deep wells from the Krishna-Godavari (K-G) Basin, Andhra Pradesh, India. In these wells, two phases of Deccan volcanism record the world's largest and longest lava mega-flows interbedded in marine sediments in the K-G Basin about 1500 km from the main Deccan volcanic province. The main phase-2 eruptions (∼80% of total Deccan Traps) began in C29r and ended at or near the KTB, an interval that spans planktic foraminiferal zones CF1-CF2 and most of the nannofossil Micula prinsii zone, and is correlative with the rapid global warming and subsequent cooling near the end of the Maastrichtian. The mass extinction began in phase-2 preceding the first of four mega-flows. Planktic foraminifera suffered a 50% drop in species richness. Survivors suffered another 50% drop after the first mega-flow, leaving just 7 to 8 survivor species. No recovery occurred between the next three mega-flows and the mass extinction was complete with the last phase-2 megaflow at the KTB. The mass extinction was likely the consequence of rapid and massive volcanic CO 2 and SO 2 gas emissions, leading to high continental weathering rates, global warming, cooling, acid rains, ocean acidification and a carbon crisis in the marine environment. Deccan volcanism phase-3 began in the early Danian near the C29R/C29n boundary correlative with the planktic foraminiferal zone P1a/P1b boundary and accounts for ∼14% of the total volume of Deccan eruptions, including four of Earth's longest and largest mega-flows. No major faunal changes are observed in the intertrappeans of zone P1b, which suggests that environmental conditions remained tolerable, volcanic eruptions were less intense and/or separated by longer time intervals thus preventing runaway effects. Alternatively, early Danian assemblages evolved in adaptation to high-stress conditions in the aftermath of the mass extinction and therefore survived phase-3 volcanism. Full marine biotic recovery did not occur until after Deccan phase-3. These data suggest that the catastrophic effects of phase-2 Deccan volcanism upon the Cretaceous planktic foraminifera were a function of both the rapid and massive volcanic eruptions and the highly specialized faunal assemblages prone to extinction in a changing environment. Data from the K-G Basin indicates that Deccan phase-2 alone could have caused the KTB mass extinction and that impacts may have had secondary effects. © GEOL. SOC. INDIA. Source

Keller G.,Princeton University | Adatte T.,Geological and Paleontological Institute | Bhowmick P.K.,KDMIPE | Upadhyay H.,KDMIPE | And 3 more authors.
Earth and Planetary Science Letters

In C29r below the Cretaceous-Tertiary boundary (KTB) massive Deccan Trap eruptions in India covered an area the size of France or Texas and produced the world's largest and longest lava megaflows 1500. km across India through the Krishna-Godavari (K-G) Basin into the Bay of Bengal. Investigation of ten deep wells from the K-G Basin revealed four lava megaflows separated by sand, silt and shale with the last megaflow ending at or near the KTB. The biologic response in India was swift and devastating. During Deccan eruptions prior to the first megaflow, planktic foraminifera suffered 50% species extinctions. Survivors suffered another 50% extinctions after the first megaflow leaving just 7-8 species. No recovery occurred between the next three megaflows and the mass extinction was complete with the last mega-flow at or near the KTB. The last phase of Deccan volcanism occurred in the early Danian C29n with deposition of another four megaflows accompanied by delayed biotic recovery of marine plankton. Correlative with these intense volcanic phases, climate changed from humid/tropical to arid conditions and returned to normal tropical humidity after the last phase of volcanism. The global climatic and biotic effects attributable to Deccan volcanism have yet to be fully investigated. However, preliminary studies from India to Texas reveal extreme climate changes associated with high-stress environmental conditions among planktic foraminifera leading to blooms of the disaster opportunist Guembelitria cretacea during the late Maastrichtian. © 2012 Elsevier B.V. Source

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