Palaeontological characteristics and sedimentary environments of the Jurassic Buqu Formation in the Northern Qiangtang Basin
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Abstract:
Based on studies of the six sections of the Jurassic Buqu Formation in Shenglihe, Donghu and Maomaoshan areas in the south central parts of the North Depression of the Northern Qiangtang Basin, their lithological characters, and their rich paleontological data (including abundant brachiopods and bivalves), we propose that the age of the Buqu Formation is constrained to the Middle Jurassic Bathonian to early Callovian (probably extending to early Bajocian). Results from our observations and regional correlations indicate that the Buqu Formation in the Northern Qiangtang Basin is diachronic. Characteristics of rock assemblages of the Buqu Formation indicates that the sediments can obviously divided into three parts. Both the lower and upper parts consist of a series of low-energy carbonate rocks dominated by microcrystalline and grain-muddy structures, and the middle part consists of a series of high-energy carbonate rocks dominated by pelsparite. Combined with the palaeoecological habits of the paleontological, the overall depositional environments of the Buqu Formation are considered as a near-shore shallow water open platform and a platform margin carbonate sedimentary system, which constitute multiple depositional cycles. This basic data provides a foundation for further analysis of the lithofacies paleogeography of the Buqu Formation in the south central parts of the Northern Qiangtang Depression.
