Lithofacies types, mineralogical assemblages and depositional model of the Maastrichtian–Danian successions in the Western Desert of Iraq and eastern Jordan

Abstract

An integrated lithofacies and mineralogical assemblage was used to describe a depositional model and sequence stratigraphic framework of the Maastrichtian–Danian succession in the Western Desert of Iraq and eastern Jordan. Fifteen lithofacies types were grouped into three associations recognized in a distally steepened ramp characterized by an apparent, distinct increase in a gradient paleobathymetric deepening westward. The clay and nonclay minerals are dominated by smectite and palygorskite, with trace amounts of kaolinite, sepiolite, illite and chlorite. Meanwhile, quartz, calcite, dolomite, opal CT (Cristobalite - Tridymite), and apatite are the main nonclay minerals. The widely dominated smectite in the Western Phosphatic Basin of Iraq (WPB) refers to warm, subhumid climates and low topographic relief in the source area, which increased significantly with transgressive cycles. In contrast, the palygorskite was generated under seasonal semiarid/arid climates associated dominantly with regressive cycles. Five sequence boundaries are documented in the present study according to hiatus, erosional surfaces, Thalassinioides burrows, reworked fauna, and extensively bored hardground. These sequence boundaries separate the studied sequences into four third-order depositional sequences correlated to their regional and global counterparts. The combined effects of the local tectonic activity of the Rutbah High and sea-level drops are amalgamated inside the Western Desert of Iraq and eastern Jordan because of a long-time gap, particularly across the Cretaceous/Paleogene (K/Pg) and Danian/Selandian (Da/Se) transitions.