Abstract: The paper presents a datdaset of marine carbonate rocks from the Sinian Dengying Formation on the northwestern margin of the Yangtze, which is the first large-scale carbonate formation deposited in the Upper Yangtze region after the Nanhua Ice Age. It records not only the Sinian response to global warming, but also information on the evolution of marine microorganisms and the growth of carbonate rocks on the eve of the Early Cambrian skeletal animal outbreak. Moreover, mound-shoal dolomite has currently become an important indicator of deep-seated ancient carbonate oil and gas in Sichuan Basin. Microscopic images of the 119 rock thin sections collected from Qingping, Mianzhu, Luchi, and Zhenba sections in the northwestern margin of the Yangtze Platform revealed that the composition and structural characteristics of the rocks change with time, and the sections generally manifest to have the sequence of siliceous rock, micrite dolomite, algae dolomite and granular dolomite, reflecting the development process of the edge of the carbonatite platform margin affected by secondary sea level fluctuations during a slow sea level rise against the epeiric sea on the northwestern margin of the Yangtze Platform. The dataset records in detail such information as the location, approximate stratigraphic age, rock composition and structural characteristics of the samples. It can be applied to the study of rock microfacies of the Sinian Dengying Formation on the northwestern margin of the Yangtze Platform, and to the interdisciplinary research concerning, for example, intelligent image recognition. It also provides basic information services for production activities such as oil and gas reservoir description and formation mechanism analysis, teaching and science popularization.
Keywords: northwestern margin of Upper Yangtze; Dengying Formation of the Sinian; carbonate rocks; polarized photomicrograph