Elemental and Sr isotope profiles of Cretaceous-Tertiary (K-T) boundary layers at Medetli, Gölpazari, northwestern Turkey(松丸国照教授退職記念特集)<数学・自然科学>

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  • Elemental and Sr isotope profiles of the Cretaceous-Tertiary (K-T) boundary layers at Medetli, Golpazari, northwestern Turkey

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Major and trace element concentrations and Sr isotope ratios were determined for theCretaceous-Tertiary (K-T) transitional layers in Medetli. Gblpazari. northwestern Turkey. Late Maastrichtian gray colored sandstone layer (layer A) is overlain by yellow colored sandstone layer (layer B) with thin goethite-rich layers. Lower Paleocene limestone (layer C) overlies layer B. Fossils are absent in layer B. Major elements such as Ab03. MgO. MnO. NazO and K20 are slightly lower in layer B compared with layer A. Trace elements. such as Ba. Rb and Y. are relatively high in layer A than in layer B. while Sr is clearly rich in layer B. Distinct peaks of Fe. Ni. Co, Cr. As and Sb are found in a goethite-rich layer. The Sr isotope ratios (initial 87Sr /86S r ratios) of samples change from layer A (0.7099-0.7112) to layer B (0.7079-0.7084). This abrupt change of Sr isotoperatios is explained by a drastic increase of precipitation rate of sea water Sr to layer B rather than in layer A. and this change may b related to the K-T event. Association with these results and element concentrations including Ir (Arakawa et aJ .. (2003). the actual K-T boundary is situated probably between the top of layer A and the bottom of layer B. In the Medetli region. The deposition of the top of layer A and probably the layer B are considered to have been formed by the K-T and its successive events.

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