Sedimentary characteristics and tectonic background of Bantou period in Fujian

Abstract：The Early Cretaceous Bantou Formation in Fujian Province is of river and lacustrine facies of fragmental sediments with well-developed black shales. The lake and swamp were widely distributed, which could be assigned to mild mid-latitude climate geographical environment. It has rich and different kinds of fossils. The Zhenghe-Dabu fault zone is a boundary, with which Fujian continent can be easily divided into west and east parts. There are obvious differences in appearance and characteristics of Bantou Formation in these two parts. There are some problems concerning Bantou Formation which deserve further studies. In this paper, knowledge was obtained through scientific investigation by the combination of field survey with in-door analysis. The sedimentary period of Bantou Formation belonged to Aptian Stage in an active island arc belt in Early Cretaceous. Graden basins were extensively developed, which subsided at the early stage and was faulted at the late stage. The tectonic background of Bantou Formation resulted from the interaction between palaeo-Pacific plate and Eurasian plate, with the crust thickness subtracted probably in partial areas. There were no continuous large scale subsidence of graden basin in Early Cretaceous in Fujian and Taiwan Strait, and the source rocks and reservoirs with considerable thickening could be hardly formed. Oil and gas potential can hardly be delineated without the knowledge of thickened detrital deposition and good allocations. As thermal events were violent volcanic movements in Fujian and Taiwan Strait from Cretaceous to Cenozoic, they might have strongly affected the transformation and migratory concentration of organic materials at the late stage of Early Cretaceous. The understanding obtained by the authors is of great significance, showing that the investigation of tectonic, lithofacies and palaeogeographic factors is very important in oil and gas exploration in Bantou Formation.