Keywords: 
• North Carnarvon Basin /
• Mungaroo Group /
• Locker Shale /
• the transformation of sedimentary framework /
• source rock

Abstract: The North Carnarvon basin is Australia's most important oil and gas basin, also one of main gas- rich basins in the world. In Triassic, North Carnarvon basin belongs to pericratonic depression and the strata are hugely thick and widely distributed. Mandatory regression occurred in northwest shelf of Australia in Late middle Triassic, causing the transformation of Triassic sedimentary framework, North Carnarvon basin, and the depositional environment of North Carnarvon basin from offshore turn into the transition facies, thus two distinct strata-Locker shale and Mungaroo group deposited in North Carnarvon basin. In this article, paleogeographic setting of Locker shale and Mungaroo group and characteristics of associated source rock and organic maceral are elaborated under macro-micro scales, and organic-inorganic aspects.
On a macro level, Mungaroo group is dominated by large-scale delta interbedded distributary channel sandstones and dark mudstones. The mudstone in proximal delta plain is thin, of which terrigenous organic matter content is high and TOC content can be up to 1.59%, besides, thin coal seams just developed locally. The mudstone in remote delta plain is thick, of which terrigenous organic matter content is high and TOC content is highest and can be up to 4.11%, besides, thin coal seams developed widely. The mudstone in delta front is thick, of which terrigenous organic matter content is low and TOC content can be up to 1.05%. Locker Shale is composed of major shallow sea depositional association and small-scale delta. The source rock in open shallow sea subfacies is the thick, what's more, prodelta, offshore and open shallow sea subfacies TOC content is much lower, and three sub-phases average TOC is 1.16%.
On a micro level, sedimentary facies of Mungaroo group from the proximal plain facies-distal plain facies-front subfacies liptinite content gradually increased, with that vitrinite first increased and then decreased, but inertinite first decreased and then increased. As Locker Shale, by the prodelta to neritic facies liptinite increased, with that both vitrinite and inertinite reduced.
The distribution of source rocks and organic maceral is closely related to special paleogeographic and monsoon flood paleoclimate setting of the southern margin of Thethys. The distal delta plain of Mungaroo group is the most favorable environment for the development of source rock. Lithofacies palaeogeographic framework and Sedimentary evolution regularity in Trassic of North Carnarvon Basin reflect the sedimentary characteristics which is dominated by paroxysmal water under the effect of greenhouse climate, providing a new train of thought for oil and gas resource evaluation in a similar geological setting.