Nannostratigraphy, nannofossil events, and paleoclimate fluctuations in the lower boundary of Kalat formation in East Ko
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ORIGINAL PAPER
Nannostratigraphy, nannofossil events, and paleoclimate fluctuations in the lower boundary of Kalat formation in East Kopet Dagh (NE Iran) Fatemeh Hadavi & Marziyeh Notghi Moghaddam
Received: 15 August 2012 / Accepted: 11 December 2012 # Saudi Society for Geosciences 2012
Abstract The biostratigraphy and the response of calcareous nannofossils to the End Cretaceous warming are investigated in the lower boundary of Kalat formation through the record of species richness, diversity, distribution patterns, and statistical treatments. The Kalat formation comprised of coarse-grained detritus limestone with subordinate sandstone intercalations. In the studied sections, the number of ten samples were taken and prepared with smear slide. In Dobaradar, section 22 species; in Kalat, section 25 species; and in Chahchaheh, section 32 species have been determined. Based on nannoplanktons and as a result of biostratigraphic studies, the nannofossil standard zones (CC25–CC26) were identified in all of sections. According to these zones in all of sections, the age of the studied thickness is Late Maastrichtian–Late Late Maastrichtian. In these sections, the presence of Micula murus at the end of Neyzar formation and the presence of this species at the lower part of Kalat formation indicate that the investigated boundary is Late Maastrichtian in age. The paleoecological results point to warm climate. The presence of warm water indicators (M. murus and Micula prinsii) and the absence of cool water indicators (Ahmuellerella octoradiata, Kamptnerius magnificus, and Nephrolithus frequens) suggest warm surface water conditions in these areas. In the lower boundary of Kalat formation, base on Lithraphidites spp. and Watznaueria barnesae, lowered fertility condition with low productivity at the end of the Maastrichtian were suggested, and the studied area was deposited in shallow marine environment in relatively low latitude. Keywords Nannostratigraphy . Paleoclimate . Kalat . Iran . Kopet Dagh F. Hadavi : M. N. Moghaddam (*) Department of Geology, Ferdowsi University of Mashhad, Azadi Square, Mashhad 9177948974, Iran e-mail: [email protected]
Introduction The well-documented long-term cooling trend that started in the Late Campanian and continued into the Early Paleogene (Douglas and Savin 1975; Boersma and Schackleton 1981) was interrupted by a short warming event between 65.6 and 66 Ma. Cooling resumed in the last 100 kyr of the Maastrichtian (Li and Keller 1998; Gradstein and Ogg 2004). (All ages given in the literature prior to this publication may therefore differ by at least 0.5 Ma.) The Kopet Dagh rang, which stretches over nearly 7,000 m in a WNW–ESE direction east of the Caspian Sea, from the FSU over Iran into Afghanistan, comprises 5,000–7,000 m of Middle Jurassic to Paleogene strata (Afshar Harb 1969; 1979). This paper discusses the results relative to the Campanian and Maastrichtian climate evolution and presents new calcareous nannofossil data from lower boundary of Kalat formation in East Kopet Dagh
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