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

Abstract

Some element concentrations were measured and element profiles were made for the Cretaceous-Tertiary (K-T) boundary layers in Medetli, Golpazari, 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.