Abstract:

In China, shales are widely distributed, continuous in time and complex in space. In this paper, the distribution of shales in the North China, South China and Tarim Plates are systematically sorted out and discussed. The Middle and Upper Proterozoic shales are dominated by marine facies with some continental facies, of which the littoral-neritic to neritic shelf, marine and continental moraine shales are developed, and the field shale sections are characterized by the distribution on the edges of different paleoplates. The Lower Paleozoic shales are dominated by marine facies, with the development of open shelf to neritic shelf shales, which are mainly distributed in the South China Plate and the Tarim Plate. The Upper Paleozoic shales which are dominated by marine-continental transitional facies and locally by marine and continental facies have the largest development and distribution in China. The Mesozoic and Cenozoic shale types are diverse but dominated by continental facies. The Mesozoic shales are mainly developed longitudinally along Yunnan, Sichuan and Shanxi and latitudinally from Xinjiang to Heilongjiang via Shanxi, while the Cenozoic shales are primarily developed in the eastern and western sides of the North China Plate. The plate margins, fold belts and complex tectonic activity areas exert an important impact on the distribution of shales. The ancient trough has a significant influence on the shale deposition, so do the depositional environment on the shale components, and the components on the weathering resistance of field shale sections. The development of field shale sections in different epochs and regions are affected by multi-factors, and each has specific geological characteristics. Shale in sections can be divided as manganese, siliceous, calcite or dolomite, silty, carbonaceous, coal and mixed types, in which carbonaceous shale can occur in various sections. Manganese shale is primarily developed in the strata before Middle Permian in South China Plate, while siliceous shale is mainly found in the open shelf facies, coal-type shale is developed later and mainly deposited in the marine-continental transitional facies and continental facies, The silty, calcite or dolomite shales are widely distributed. Each type of shale has specific epochal and regional distribution characteristics, so a systematic review of the shale strata in China could be helpful for the discovery for more shale gas in new strata or new areas.

Key words: plate, shale age, shale lithology, shale distribution, field outcrop, shale type, significance for shale gas