Geochemical data from Tanuma carbonate reservoir (Central Iraq) indicates higher terrigenous input and deoxygenation during Coniacian- Early Santonian age

A negative carbon isotopic excursion (CIE), typically overlaid atop a long term positive pattern, and significant environmental and climatic shifts are two characteristics that identify the Coniacian–Santonian, according to a variety of sedimentary records. But there is still no evidence to support the theory that variations in oceanic deoxygenation and continental weathering input in shallow seas could contribute to carbonate-platform crisis at low latitude. Here, carbonate content and carbonate-hosted elements from the Tanuma carbonate platform in Central Iraq (East Baghdad Oilfield; EB10 well) are analyzed for the Coniacian–Early Santonian transitional phase. The OAE3 boundary is marked by a clear increase in the elements that are most water insoluble (such as Al, Sc, Th, Ti, and all of the rare earth elements), which is followed by a modest increase or comparatively high-level values throughout the OAE CIE's negative phase. This implies that the improved terrigenous input may be connected to the rapid global warming that occurred throughout this time period. The increase in the abundance of these water-insoluble elements is immediately followed by an increase in the Mn, Ce, and Ce anomaly, which are then better values throughout the negative CIE interval. These data suggest that throughout this time period, shallow water experienced the process of deoxygenation and the growth in Mn (suboxic) condition. These events were probably related to increased nutrient input and continental weathering, which favored oxygen consumption as well as primary productivity. In CIE's recovery phase, the stratigraphically elevated insoluble in water elements exhibit a gradually declining trend in parallel to heightened redox proxy values, indicating a drop in the intensity of continental weathering and associated second the deoxygenation at shallow seas. In this case, increased recycling in bioessential nutrients or a slowing of the ocean's circulation could have contributed to deoxygenation. The interdependent connection among carbonate content, geochemical data, and biotic changes indicates that:1- the Tanuma carbonate platform probably noticed a minor degradation around the OAE3 boundary period due to the beginning of increasing terrigenous input and the deoxygenation at shallow seas.2- during the CIE's negative phase, the heightened terrigenous input and deoxygenation probably contributed significantly to the more serious situation facing benthic carbonate producers.