A sequence boundary related aeolian sand record in a continental basin: The Cretaceous-Paleogene White Sandstone Member, Tabei Uplift, Tarim Basin, NW China

Abstract

A sequence boundary typically corresponds to an unconformity, with fluvial incised-valley fills representing a classic depositional model. However, aeolian deposits associated with sequence boundaries, though equally significant, have received less attention in studies of continental basins. Therefore, this study investigates aeolian sand sedimentary records near a sequence boundary in a continental basin based on an integrated analysis of 3D seismic volumes, wireline logs and cores from the Cretaceous-Paleogene deposits in the Tabei Uplift (Tarim Basin, NW China). The Cretaceous-Paleogene White Sandstone Member was formed in a salt-lake margin desert environment above a local unconformity surface that is well recognized on seismic profiles. The studied sandstone sequence is characterized by its friable texture and exhibits distinctive aeolian depositional features, including developed grainfall strata and grainflow strata within the core samples. Scanning electron microscopy (SEM) analysis reveals the presence of abundant dish-shaped impact pits on quartz grain surfaces, providing compelling evidence for the aeolian origin of these sandstones. During the Late Cretaceous to Paleogene period, the study area underwent significant geomorphological changes due to the tectonic uplift of the Tianshan and Kunlun Orogenic Belts. This tectonic activity resulted in the progressive erosion of Cretaceous strata in both the northwestern and southeastern regions of the research area. During this period, with regression of the Tarim Sea, aridity gradually increased, leading to the formation of extensive aeolian sands in the area. The aeolian sandstone pinches out from the southeast to the northwest in the area east of the WM7 fault belt. In the Paleogene, incised valleys were developed and transported eroded aeolian sands to the salt lake in the northwest. This study demonstrates the transformation of Cretaceous-Paleogene aeolian sand in a "sandstone factory" in the northern Tarim Basin during a greenhouse period. The "sandstone factory" provides an opportunity for research on sequence boundary-related aeolian sandstone unrelated to a fluvial incised valley in a continental basin.