Abstract:

Researches on the sediments, paleocurrents and depositional environments of the Early Cretaceous in northern QilianJiuxi areas show that an extensive basin (Northern QinlianJiuquan Lake), covering areas from the midQinlian Mountains in the south to the Beishan in the north and from the western Altyn Fault to Jiudong in the east, existed in the Early Cretaceous. Current study indicates that the Northern QinlianJiuquan Lake was involved in a sedimentary and palaeogeographical evolutionary history in succession, i.e., from initial alluvial fan, and then fluvial, followed by lacustrine and fluvial environment finally. Depositional succession consisting of sediments in a varied grain size from coarser, fine to coarser vertically was a result of the initial, increasing and maximum extension of the Northern QinlianJiuquan Lake. In addition, research suggests that Changma, Hanxia and Hongliuxia areas of the southern basin became the centers of subsidence and deposition resulting from strikeslip of Altyn Fault in the Early Cretaceous, and furthermore the basin extended to the maximum in space as a result.

Key words:  Early Cretaceous, sedimentary characteristics, paleogeography, northern QilianJiuxi Basin