TY - JOUR
T1 - Paleoenvironmental changes across the Cretaceous-Tertiary boundary at Koshak, Kazakhstan, based on planktic foraminifera and clay mineralogy
AU - Pardo, Alfonso
AU - Adatte, Thierry
AU - Keller, Gerta
AU - Oberhänsli, Hedi
N1 - Funding Information:
We thank Norman MacLeod, the reviewer Mark Leckie, Xavier Orue-etxebarria, and two anonymous reviewers for their comments and suggestions, N.P. Naidin (Moscow State University) for his guidance and help in the field and J. Richard (Neuchâtel) for XRD samples preparation. This study was partially supported by grants from DGICYT Pb94-0566 and DGES Pb97-1016 (AP), the Swiss National Fund No. 8220-028367 (TA) and NSF OCE 9021338 (GK).
Copyright:
Copyright 2011 Elsevier B.V., All rights reserved.
PY - 1999/11
Y1 - 1999/11
N2 - The Koshak section of the Mangyshlack Peninsula, Kazakhstan, is one of the most complete Cretaceous-Tertiary (K-T) transitions known from the boreal Paratethys. Cretaceous species richness is low (11 to 13 species), except for a peak of 20 species near the K/T boundary in the uppermost Maastrichtian (top 50 cm) that represents the temporary incursion of low-latitude taxa. This maximum species richness occurred during climatic warming associated with increased humidity, as suggested by clay mineral analyses. Biofacies analysis suggests external platform conditions at this time, followed by a more humid climate, a sea-level transgression, and deepening basinal facies in the lower Danian Subzone P1a. Shallower platform conditions resumed in Danian Subzones P1b and P1c, accompanied by a cooler and probably more arid climate. No abrupt mass extinction occurred at the Koshak K/T boundary which is marked by an Ir anomaly, a clay layer and the first appearance of Tertiary planktic foraminifera. The influx of lower-latitude species ends at or before the K/T boundary, whereas the majority of the indigenous Cretaceous assemblage survived into the Danian. These data suggest that long-term climatic changes may have been the principal factors in the progressive demise of the Cretaceous planktic foraminifera in the eastern boreal Paratethys.
AB - The Koshak section of the Mangyshlack Peninsula, Kazakhstan, is one of the most complete Cretaceous-Tertiary (K-T) transitions known from the boreal Paratethys. Cretaceous species richness is low (11 to 13 species), except for a peak of 20 species near the K/T boundary in the uppermost Maastrichtian (top 50 cm) that represents the temporary incursion of low-latitude taxa. This maximum species richness occurred during climatic warming associated with increased humidity, as suggested by clay mineral analyses. Biofacies analysis suggests external platform conditions at this time, followed by a more humid climate, a sea-level transgression, and deepening basinal facies in the lower Danian Subzone P1a. Shallower platform conditions resumed in Danian Subzones P1b and P1c, accompanied by a cooler and probably more arid climate. No abrupt mass extinction occurred at the Koshak K/T boundary which is marked by an Ir anomaly, a clay layer and the first appearance of Tertiary planktic foraminifera. The influx of lower-latitude species ends at or before the K/T boundary, whereas the majority of the indigenous Cretaceous assemblage survived into the Danian. These data suggest that long-term climatic changes may have been the principal factors in the progressive demise of the Cretaceous planktic foraminifera in the eastern boreal Paratethys.
KW - Clay minerals
KW - K/T boundary
KW - Kazakhstan
KW - Planktic foraminifera
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U2 - 10.1016/S0031-0182(99)00114-5
DO - 10.1016/S0031-0182(99)00114-5
M3 - Article
AN - SCOPUS:0032727441
SN - 0031-0182
VL - 154
SP - 247
EP - 273
JO - Palaeogeography, Palaeoclimatology, Palaeoecology
JF - Palaeogeography, Palaeoclimatology, Palaeoecology
IS - 3
ER -