A westerly dominated Early Cretaceous eolian system in the Hami Basin, NW China

Cretaceous eolian deposits provide evidence of variations in the tropical-subtropical atmospheric circulation under greenhouse conditions. However, the misinterpretation of many such deposits as fluvial or deltaic originally hindered precise paleoclimatic reconstructions. Here we report a newly identified Early Cretaceous desert in the Hami Basin, China, which helps understand spatial-temporal variations in aridity and atmospheric circulations within central East Asia during the Early Cretaceous. The Liushuquan Formation is composed of >300-m-thick eolian deposits interpreted as an intermontane erg environment. Paleocurrent indicators within the straight-crested dunes of the Liushuquan Formation yield a mean trend of 101.3° (± 10.1°, 1 standard deviation) throughout the formation, consistent with near-surface westerly winds. Paleo-atmospheric circulation superimposed on topographic effects led to widespread eolianite accumulation during the Early Cretaceous. Combined with the spatiotemporal changes in desert distributions and prevailing surface wind patterns in East Asia, these observations are consistent with the migration of the subtropical high-pressure belt during the Early Cretaceous. We propose the following paleo-atmospheric model: (1) During the late Berriasian−Valanginian, the subtropical high belt drifted southward and northward over shorter time scales within the spatial domain of the paleo-Ordos Basin, then shifted southward at least past the Ordos Basin; (2) until the late Hauterivian−Barremian, the subtropical high-pressure zone was primarily located between the northwestern Tarim Basin and the Ordos Basin; and (3) a significant southward shift of the subtropical high-pressure zone occurred during the Aptian−Albian.