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Geochemical Journal
Geochemical Journal An open access journal for geochemistry
Published for geochemistry community from Geochemical Society of Japan.

Element profiles and Ir concentration of Cretaceous-Tertiary (K-T) boundary layers at Medetli, Gölpazari, northwestern Turkey

Yoji Arakawa, Xiaolin Li, Mitsuru Ebihara, Engin Meriç, Izavel Tansel, Simau Bargu, Hayrettin Koral, Kuniteru Matsumaru
Geochemical Journal, Vol. 37, No. 6, P. 681-693, 2003


Some element concentrations were measured and element profiles were made for the Cretaceous-Tertiary (K-T) boundary layers in Medetli, Gölpazari, northwestern Turkey. In Medetli region, gray-colored medium to coarse grained sandstone (layer A) is overlain by yellow-colored fine-grained sandstone with intercalated thin goethite-rich layers (layer B). White colored limestone (layer C) overlies on the layer B. The layer A is latest Cretaceous and layer C is early Paleocene, and in layer B (28–37 cm in thickness) fossils are absent, and is regarded as a K-T transitional layer. In several goethite-rich layers, siderophile elements such as Fe, Cr, Ni, Co, and chalcophile element, such as As, Sb, and Zn, are enriched, and have maximum in succession from layer A to C. The enrichment of these elements are common features in most of K-T boundary sediments of the world. However, Ir concentration is relatively low (0.05–0.10 ppb) in the goethite-rich layers. The analyzed Ir concentration is slightly elevated (0.24 ppb) only in the top part of layer A. Iridium may have been diluted during sedimentation and diagenesis. The actual K-T boundary may be situated between the top of layer A and the bottom of layer B. The section from the top part of layer A to layer B is assumed to have been formed during the K-T and its successive events.

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