The Late Cretaceous palaeocurrents in the Chishui region, Guizhou and their tectonic significance

A succession of 1300-m thick continental strata was deposited during the Late Cretaceous in the Chishui region, Guizhou on the southwestern margin of the Sichuan Basin. In this paper, the Late Cretaceous sediments filling processes and tectonic significance are explored on the basis of field observation and indoor analysis of the palaeocurrents indicated by the surface outcrops in the Chishui region. The palaeocurrents in the braided streams were directed from northeast to southwest during the Late Cretaceous, indicating that the sediments detritus in the Chishui region may come mainly from the northern and eastern parts of the Basin. Judged from the provenance, stratigraphic distribution and regional geological background, it is inferred that the Late Cretaceous continental sedimentary basin in the Chishui region may belong to the intracontinental foreland basin, and the intracontinental orogenic zones appear in the eastern part of the Basin as a major provenance. The formation of the Late Cretaceous intracontinental foreland basin in the Chishui region may be governed by the intracontinental orogeny caused by the tectonic compression events in South China during the Late Cretaceous, and thus the Sichuan Basin has gone through the evolution from a fresh lake to a saline lake.