THE EVOLUTION OF THE NW-TRENDING SECTION OF THE SHUICHENG-ZIYUN AULACOGEN IN GUIZHOU PROVINCE, CHINA

The Shuicheng-Ziyun Aulacogen is the NW-trending section of the Danchi-Ziyun Rift in the southwest of the Yangtze Plate. The aulacogen is composed of the Late Paleozoic deep-water, basin-slope facies, which runs in a northwest-southeast narrow belt.

In this Aulacogen, different strata of the Late Paleozoic have different distribution patterns. The stratigraphic framework from the Devonian to Permian strata exposed in the Aulacogen was studied by analyzing the stratigraphic distribution, sequence, and spatial variation in this region. According to the lithologic characteristics, sedimentary assemblages, stratigraphic contacts, vertical sequences (stratigraphic column) and tectonic setting of the strata, the Late Paleozoic strata were classified into three sequences of basin-filling strata, which were subdivided into nine sedimentary sequences.

The evolution of the Shuicheng-Ziyun Aulacogen was divided into four stages: the pre-rift uplift and denudation, crustal extension and thinning, faulting and subsidence, and mantle plume activity. It was found that the inhomogeneous activity of fault blocks was the major cause the formations of the platform-basin pattern and the aulacogen. The narrow range, large thicknesses, and highly varying distribution of the Lower Permian Longyin Formation may be attributed to the development of the extensional basin. Additionally, similar distribution pattern of the Upper Permian Linghao Formation may result from the development of strike-slip structures.

It was proposed that the strong crustal uplift caused by the rapid rise of the Emeishan mantle plume and the related basaltic eruption during the Late Permian altered the geography and topography of the region. Therefore, the crustal uplift was considered to be one important factor that terminated the development of the Shuicheng-Ziyun Aulacogen. This was a significant conclusion for future research on the evolution of the basins of this type worldwide.