Dispersion of sandy sediments during marine-continental transition: An integrated study from the Late Paleozoic western Ordos Basin

The western Ordos Basin is located at the intersection of multiple tectonic units and is a key area in the resto-ration of the palaeogeographic pattern of the East Asia region. The stability of the area and well-developed Paleozoic strata in the basin provide ideal conditions for revealing the relationships among the tectonic processes apparent there. However, within the constraints of extensive post-depositional modification, poor-quality seismic data, and a lack of wells, sediment dispersion differences, source attribution, and source-to-sink processes are still unclear. In this study, we integrated sedimentology, mineral, and geochemical data obtained from marine, continental, and marine-continental transition sedimentary environments in the study area in order to reveal the evolution from source-to-sink. The results show that the western Ordos Basin was predominantly supplied by the Alxa block, Yinshan orogenic belt, Qilian orogenic belt, and the North Qinling orogenic belt during the Late Paleozoic era. As a result of the closure of the Paleo Asian Ocean, the Alxa block and Yinshan orogenic belt became the primary source areas to the north, being composed of granite and alkaline basalt and some sedimentary rocks. In the southern area, the Qilian and the Northern Qinling orogenic belts were subjected to the PaleoTethys remnant ocean basin subduction during the Early Permian. Granite and alkaline basalt were the source rocks of the North Qinling orogenic belt, which became the source area during the Shanxi period. The Qilian orogenic belt contains some sedimentary rocks. The continuous uplift of the southern and northern orogenic belts. The tectonic setting of the northern source area transitions from a passive continental margin to an active continental margin with a mixture of continental arc. The tectonic setting of the southern source area transitions from a mixture of passive continental margin and active continental margin to an active continental margin and continental island arc. The climate changes gradually from humid to semi-arid and then to arid, and meanwhile, the sea level shows a decreasing trend, leading to an increasing distance of advancement for each source-to-sink system, and gradually converged in the central and eastern regions of the basin. Tidal and fan delta sandy sediments in the study area were transformed into fluvial delta sandy sediments in the northern two source-to-sink systems. The southern source-to-sink systems gradually changed from scattered sandbarrier and coastal sandy sediment to fluvial sandy sediment after the Shanxi Formation.