Paleoenvironmental changes across the Cretaceous-Tertiary boundary at Koshak, Kazakhstan, based on planktic foraminifera and clay mineralogy

Détails

ID Serval
serval:BIB_5D53CE86FC7E
Type
Article: article d'un périodique ou d'un magazine.
Collection
Publications
Titre
Paleoenvironmental changes across the Cretaceous-Tertiary boundary at Koshak, Kazakhstan, based on planktic foraminifera and clay mineralogy
Périodique
Palaeogeography, Palaeoclimatology, Palaeoecology
Auteur(s)
Pardo A., Adatte T., Keller G., Oberhansli H.
ISSN-L
0031-0182
Statut éditorial
Publié
Date de publication
1999
Peer-reviewed
Oui
Volume
154
Pages
247-273
Langue
anglais
Résumé
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. (C) 1999 Elsevier Science B.V. All rights
reserved.
Création de la notice
28/09/2012 10:02
Dernière modification de la notice
20/08/2019 14:15
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