Abstract

Stable isotope analysis of oxygen (δ18O) and carbon (δ13C) is applied to samples from the Cretaceous – Paleogene boundary (K/Pg boundary) sequence at five localities (Chinarok, Dokan, Dartw, Deramazan, Qalbaza) from Kurdistan Region of NE Iraq. The boundary is located within a thick section of flysch sediments belong to the Tanjero Formation (Maastrichtian) and Kolosh Formation (Paleocene). The purpose of this work is to give an insight into the significance of the isotopes signals in paleoclimatic and paleoenvironmental changes across the boundary zone. Stable isotopes of oxygen (δ18O) and carbon (δ13C) were calculated for three samples at each examined locality of a previously well determined K/Pg boundary sequence using nannofossils. The resulted (δ13C) during Maastrichtian shows negative shift in the samples of the Chinarok, Dartw, and Deramazan localities and the other two localities have positive excursion. This indicate rise of sea water temperature for the first group of samples, i.e. rise of water temperature close to K/Pg boundary. The other two localities have controversial isotopes signals. For the early Danian samples, the Dokan, Deramazan and Qalbaza localities have positive signals with clear increase of the ratio value, the other two localities show positive excursion. This implies a drop of water temperature for the first group which is compatible with global climatic changes, whereas the other two shows contrasted signals. The oxygen isotope ratio (δ 18O) shows similar variable signals among the examined localities. During late Maastrichtian and up to the K/Pg boundary the oxygen isotopes ratio (δ 18O) at four localities (Chinarok, Dokan, Dartw, and Deramazan) show relative drop of value indicating relatively warmer temperature. This drop continue through the early Danian time in two localities (Dokan and Dartw) while the other three have positive excursion suggesting cooler sea water. The heterogeneity of the isotopes signals among the studied localities could be explained in term of environmental effects alterations such as diagenesis or other sedimentation processes. Additional possible explanation is related to the variable sampling spacing at each locality, which could generate mismatching results during correlation.

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The article was added to IASJ on 2021-12-05

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