Distribution of the Upper Triassic terrigenous organic matter in Mungaroo delta of North Carnarvon Basin, Australia
Li Dan1,2,3, Yang Xianghua1,2, Chang Yinshan1,2, Liu Haoran1,2, Xu Xiaoming3, Zhu Guanghui3
1 Key Laboratory of Tectonics and Petroleum Resources, Ministry of Education,China University of Geosciences(Wuhan),Wuhan 430074, Hubei; 2 Faculty of Earth Resource,China University of Geosciences(Wuhan),Wuhan 430074, Hubei; 3 CNOOC Research Institute,Beijing 100027
Abstract：The giant shallow water braided fluvial delta, Mungaroo delta, was developed in the Mungaroo Formation in North Carnarvon Basin during the Middle and Upper Triassic. Based on logging data and core data,together with the regional geological setting,the Mungaroo delta is divided into four sedimentary sub-facies,including the proximal delta plain,the distal delta plain,the delta front and the prodelta. The proximal delta plain and the distal delta plain are widely spread,while the delta front and the prodelta are underdeveloped. Analysis of the terrigenous organic matter in the different sub-facies suggests that: (1)During the deposition of sediments, the peat bog underwent a scouring transformation due to the influence of the circum-Tethys giant monsoon flood,hence the organic matter is mainly dispersed and the thin coal strata is only developed in the distal delta. (2)The influence of monsoon floodvary greatly from sub-facies to sub-facies. The proximal delta plain was transformed intensively by the flood and was rich in glutenite although thin mudstone could also be found in it. The maceral of the mudstone is mainly inertinite because most of the vitrinite was oxidized. (3)Although the marsh sediments in the distal delta plain underwent frequent scour of the flood,there are still many thin coal beds developed in dark mudstone. The content of terrigenous organic matter in the mudstone is highest with vitrinite as the main type. (4)The delta front and the prodelta are narrow. The terrigenous organic matter content is low in these facies. The distal delta plain is the most potential hydrocarbon-generating facies of the four facies and its average total organic carbon(TOC) content can be up to 4.11％. The terrigenous organic distribution reflects that the braided river delta sedimentary features underwent a megamonsoon influence.
Li Dan,Yang Xianghua,Chang Yinshan et al. Distribution of the Upper Triassic terrigenous organic matter in Mungaroo delta of North Carnarvon Basin, Australia[J]. JOPC, 2014, 16(2): 193-204.
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