Sedimentological and geochemical evidence of Aptian-Albian transition in Dezful Embayment, Zagros sedimentary basin

The study of Aptian-Albian sequence in many parts of the Zagros Basin and the Arabian plate has always been limited due to the discontinuity of sediments during this period. The Tang-e Maghar, located in the Dezful Embayment, is one of the few continuous sequences of the Aptian-Albian marine sediments on the Arabian plate, the study of which provides valuable information about the paleogeological status of this period. In this study, in addition to examining the trend of changes in% TOC and% CaCO3 values through the Aptian-Albian transition sequence in order to analyze the state of the oceans, sedimentary micro-losses have also been investigated using a thin section study. In the Tang-e Maghr section, the TOC level at the base of the albino turbulence has reached 5.8%, which indicates the presence of black shale in this section. This important finding, along with the biostratigraphic data of previous studies, in addition to determining the chronostratigraphic position of this shale, has made it possible to accurately match it with other black shale horizons in other sedimentary basins. Changes in CaCO3 levels have also been recorded in different layers with different values. The most important of these fluctuations in terms of paleoecological interpretations have been at the end of Aptian and the beginning layers of Albian, which is known for a significant decrease in CaCO3 levels. This combined with fossil data from previous studies can confirm the acidic conditions of seawater at the time of Aptian-Albian sediment deposition.