Abstract:

A analysis of detailed field observations drilling data, as well as paleontological, paleoecological, and stratigraphic
correlations were carried out to characterize the sedimentary facies and understand the evolution of the Changhsingian (Late Permian)
carbonate platform margin to the west of the Chengkou-Western Hubei Trough. These data demonstrate the constructive effects of the
sedimentation and ecology of the marginal skeletal reefs and the thrombolite mud mounded on the architecture of the carbonate
platform. The model of reef and shoal complexes rim carbonate platform in Changhsingian underwent a three-stages evolution: (1) the

slope break of the carbonate platform margin had not yet formed. The reefs and shoals were not fully developed, and the foreslope of the
platform was not especially steep; (2) The rim of the carbonate platform began to form. Skeletal reefs and shoal facies were developed in
vertical progradation-aggradation association sequences. The foreslope of the platform also became steeper; (3) The ecological niche of
metazoan was occupied by microbe in Late Changhsingian. The thrombolite mud mounds were formed at this time, when a vertical
aggradation sequence with the shoals developed on top of them. This fostered the further building up of the positive relief features of the
margin. Meanwhile, the platform margin became much steeper and slump breccia developed on the foreslope of the margin. The
ecological succession of reef-building organisms, together with changes in relative sea level, influenced and controlled the evolution of
the carbonate platform margin throughout the Changxingian Stage.

Key words: carbonate platform margin, reef-shoal, ecological and sedimentary evolution, Changhsingian, Chengkou-Western Hubei
Ocean Trough