Late Albian to Maastrichtian Sequences of Crimea Penninsula: Biostratigraphy, Sea level Changes and Tectonostratigraphyтезисы доклада

Дата последнего поиска статьи во внешних источниках: 28 мая 2015 г.

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[1] Late albian to maastrichtian sequences of crimea penninsula: Biostratigraphy, sea level changes and tectonostratigraphy / L. Kopaevich, A. Nikishin, R. Gabdullin, E. Yakovishina // 2nd Symposia IGCP 609 Project and Workshop the EARTHTIMESequence Stratigraphy Workshop, Abstract book. Mihaela C. Melinte-Dobrinescu . and Andrei Briceag (eds). — UNIVERSITATEA DIN BUCURESTI, Romania Bukharest, Romania, 2014. — P. 19–19. Late Albian-Maastrichtian deposits of Crimea comprise around 700 meters mainly of carbonate sediments. Diagnostic fauna are confined to a few levels: ammonites for K1Alb3 – K2Cen; inoceramids for K2Con; ammonites and belemnites for the K2Camp-Mst. The K2Sant2 is dated by crinoids of Uintacrinus and Marsupites. Microfossils are quite abundant in Crimean Albian-Maastrichtian rocks. For age determination purposes, the standard planktonic foraminifer zonation may be used (Kopaevich, 2010). Late Albian-Maastrichtian deposits are part of the cover of the Cimmerian mountain-folded structure of Crimea. As part of the cover can be identified K1Alb3 and K2Cen-Mst megasequences. K1Alb forms an almost continuous cover and are characterized by a transgressive system tract (TST). Infilled erosional paleovalleys are seen at the base of the K1Alb3 section. The K1Alb3 formations comprise Transgressive System Tract (TST) and High Stand System tract (HST). An erosional surface is present between K1Alb3 and K2Cen. It is likely that this sedimentary unit was formed synchronously with volcanism and normal faulting. The K2Cen-Mst sequence consists of neritic planktonic limestones and marls. Within this megasequence two subdivisions can be recognized: K2Cen-Sant1, K2Sant2-Mst. The first subdivision forms the regional cover to 100-150 m thick. K2Cen2 deposits include a horizon with volcanic ashes up to 2-3 cm thick (Nikishin et al., 2013), mid-Cenomanian non-sequence is also present. Within the SW Crimea, the K2Cen comprises three full sequences 3-4th order, and the fourth one corresponds to the K2Cen-Tur boundary interval (Gale et al., 1999). At the end of the K2Cen, a layer of “black shales” was deposited up to 1m thick, with TOC content up to 5-8%. A regional sedimentation hiatus took place within the K2Sant. The intra-Santonian vertical movements were likely caused by the short-term tectonic compression. TST, HST and Lowstand System Ttract (LST) can be allocated within this sequence. The K2Sant2-Mst sequence has a thickness about to 150-250 m. Horizons of former volcanic ashes (bentonites clays) are known from the K2Camp deposits: their age coincides with the time of maximum volcanism of the Pontides in the north of Turkey. All K2Camp interval coincides with short LST, TST and HST of 3th order. The K2Mst succession presents an example of a fast regression record, with sediments indicative of a transition from an open shelf to a coastal environment. The HST was followed by LST. The terminal unit of the K2Mst indicates a short-term transgression. This transgression and warming seem could correspond to a global-scale event. At the top of the K2Mst a well expressed hard ground is ubiquitous. This work was supported by Russian Foundation for Basic Research, projects no 12-05-00263a, 12-05-00690a. References Gale, A.S., Hancock, J.M, Kennedy W.J., 1999. Biostratigraphical and sequence correlation of the Cenomanian successions in Mangyshlak (W. Kazakhstan) and Crimea (Ukraine) with those in southern England. Bull. Inst. Royal Sci. Nat. Belgique. Sci. Terre. 69, suppl. A, pp. 67-86. Kopaevich L.F., 2010. Zonal scheme for the Upper Cretaceiys of Crimea-Caucasus area on globotruncanids (planktonic foraminifers). Byulleten’ Moskovskogo Obstshestva Ispytateley Prirody, Otdel Geologicheskiy. 85(5), pp.40-52.[In Russian]. Nikishin, A.M., Khotylev A. O., Bychkov A. Yu., Kopaevich L. F., Petrov E. I., Yapaskurt V. O., 2013. Cretaceous Volcanic Belts and the Evolution of the Black Sea Basin. Moscow University Geology Bulletin.68(3), pp. 141-154.

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