Luanping basin is one of many small rift basins that developed in northeast China during mid-Cretaceous time. It is ¢lled by alluvial, fan-deltaic and lacustrine strata of the Lower Cretaceous (post 130 Ma) Xiguayuan Formation. Distribution of facies and stacking patterns are controlled by position within the basin with respect to fault-bounded basin margins. Luanping basin is bounded by a normal fault consisting of two segments that are perpendicular to each other in map view; one or both of these faults probably accommodates a component of strike-slip.This geometry gave rise to three distinct depozones within the basin: (1) a region of maximum sediment thickness located near the intersection of these two basin-bounding fault segments; (2) a shallower part of the basin, located near the tip of the normal fault segment bounding the basin to the north; and (3) a low-gradient, north-dipping ramp.The facies found in each of these settings are di¡erent. Coarse sublacustrine sediment gravity £ows inter¢nger with profundal black shale near the basin depocentre at the intersection of the two basin-bounding fault segments. Fan delta and shallow lacustrine sedimentation dominated in the shallower part of the basin near the northeastern tip of the masterbounding fault. Fine-grained shallow lacustrine sedimentation predominated along the low-gradient ramp.The facies in Luanping basin are di¡erent from those found in basins of similar size elsewhere in the northeastern China extensional tract. Speci¢cally, profundal, organic-rich black shales are found in Luanping basin but are largely lacking in neighbouring basins.We suggest that this is due to higher rates of subsidence along more steeply dipping normal faults in Luanping basin, as opposed to the other basins.

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The Paleozoic strata in the Tarim Basin, Sichuan Basin and Ordos Basin are the major targets for marine petroleum exploration, with developed high quality hydrocarbon, mainly argillite. The deep burial of these source rocks suggests that they mainly develop gas instead of oil. But different maturities of organic matter may lead to different hydrocarbon facies. Through thermochemical sulfate reduction (TSR), the hydrocarbon in the carbonate rocks may undergo a process of pyrolytic cracking and be catalyzed into gases. The marine reservoirs mainly consist of carbonate and clastic rocks, and the former is controlled by sedimentary facies, dolomitization, solution, TSR and cracking. The multiphase tectonic cycling develops multiple source-reservoir-cap combinations and diversified types of traps and reservoirs, featuring multiphase reservoir formation, mainly late-phase formation or consolidation. Palaeo-uplifts play a controlling role in hydrocarbon accumulation. Differences in major source rocks in the three basins lead to different locations of oil-gas accumulation layers, different types and patterns of reservoirs and different features of reservoir formation.

There are plenty of petroleum resources in the Chinese marine basins, which will be the potential exploration regions of petroleum in the 21st century. The formation and evolution of the Chinese marine basins have mainly undergone two major tectonic epochs and five tectonic evolution stages. The first major tectonic epoch is the early Paleozoic plate divergence and drifting epoch during which the marine basins were formed, and the second one is the late Paleozoic plate convergence and collision epoch during which the pre-existent marine basins were superimposed and modified. The five tectonic evolution stages include: the drifting of micro ① -continental plates in Oceans and the formation of marine basins mainly filled with carbonate rocks during Proterozoic-Middle Carboniferous; the ② northward collage and convergence of continental plates and the development of the paralic sedimentary basins during Late Carboniferous-Middle Triassic; the tectonically stabilized stage after the plate ③ collage and the superimposition of lacustrine basins controlled by the inland subsidence during Late Triassic-Early Cretaceous; the stage of the inland deformation and successive deep burial, uplifting, ④ erosion or breakage of marine basins influenced by the plate tectonic activities of Neo-Tethys Ocean and the West Pacific developed in Late Cretaceous-Paleocene; the stage of the foreland compre ⑤ ssion and basin-range coupling in the margin of the marine basins caused by the collision between India and Eurasia Plates and its long-distance effect since Neocene. The process of the tectonic evolution has controlled the petroleum geologic characteristics of Chinese marine basins, and a material foundation for the formation of oil and gas reservoirs has been built up via the formation of Paleozoic marine basins, and the Mesozoic-Cenozoic tectonic superimposition and modification have controlled the key conditions of hydrocarbon accumulation and preservation. From the Late Proterozoic to the Early Paleozoic, the stratigraphic sequences of the deep-water shale and continental margin marine carbonate rocks in the ancient plate floating in the oceans have developed high-quality marine source rocks and reef-shoal reservoirs. In Late Paleozoic, the crustal plates converged and uplifted into continent and the paleouplifts in the intra-cratonic basins have become good reservoirs of hydrocarbon migration and accumulation, and paralic coal beds have formed regional cap rocks. The Mesozoic-Cenozoic tectonic stability has determined the preservation condition of the Paleozoic marine basins. The marine basins have Precambrian crystal basement, the tectonic activities are relatively stable and the basin modification is relatively faint, and the ancient reservoirs are fit for preservation, such as the Tarim Basin, Sichuan Basin and Ordos Basin. They are all potential regions for marine oil and gas to be explored. marine basin, plate tectonics, tectonics evolution, petroleum explorationThe total area of the Chinese marine basins is 455×10 4 km 2 , a...

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The genetic analysis of the deep‐buried reservoirs of the Lower Paleozoic carbonate rocks in the Tarim basin is a difficult task involving many factors. Firstly, the object of study is carbonate rocks, which have undergone a long term of modification. Secondly, the rocks are deeply buried with depths of 3800–7000 m in the Tarim basin. The primary reservoir properties formed in the deposition have been strongly modified during the deep burial process. Concurrently, the different burial depths in different areas result in diversities of burial temperature, pressure, underground water, hydrochemistry and various physicochemical changes, which further lead to differences in the diagenetic type, diagenetic property, diagenetic degree and their impacts on the reservoir properties. The Lower Paleozoic Cambrian and Ordovician carbonate reservoirs in the Tarim basin can be grouped into four types, i.e., paleo‐weathered‐crust reservoirs, reef reservoirs, buried karst reservoirs and dolomite reservoirs. This paper presents a detailed discussion on the vertical and horizontal distribution characteristics, morphological division, reservoir properties and the efficiency in accumulating hydrocarbons of the paleo‐weathered‐crust type. Furthermore, its genesis is also analyzed. We proposed that the composition of the carbonate rocks, the tectonic movement with associated fractures and fissures, the paleomorphology and paleoclimate, the sea level fluctuation, and the protection of the pores and fissures by the deep burial diagenesis and burial dissolution are the main factors controlling the formation of the paleo‐weathered‐crust reservoirs. We also consider that the petroleum exploration of the Lower Paleozoic carbonate rocks should be focused on the paleo‐weathered‐crust reservoirs.

Marine source rocks are considered to be mainly composed of the Cambrian-Ordovician deposit in Tarim Basin. Based on the previous studies made by other researchers, the authors calculated the thickness and distribution scale of these Cambrian-Ordovician source rocks by integrating sequence stratigraphy with investigations on sedimentary environments, well-shooting demarcating and calibrating the thickness of unknown source rocks with the thickness of the known ones according to characteristics of the source rocks that have "double track" seismic lineup reflectance. The results showed that the distribution area of the Lower-Cambrian Yuertusi Fm. source rock in platform inner depressions, slopes and deep basins is much bigger than that of the Middle Cambrian evaporite-lagoon source rock. Moreover, the former is superior to the latter in terms of the source rock quality. Likewise, the Middle-Ordovician Heituao Fm. source rock in the slopes and deep basins has a much wider distribution and better quality than the Upper Ordovician, and its quality is also better than those of the Shaergan and Yinggan Fms. source rock within platforms as well as the lime-mud-mound source rock along the fringe of the Upper-Ordovician platform. Most good Lower-Cambrian source rocks of the Kalpin outcrop lie on the initial ingression surface or in the condensed member of the Type I sequence. In this section, the source rock in Type II is inferior to that in Type I, even being far from an effective one (TOC: <0.5%). Likewise, the good Middle-Ordovician Heituao source rock also lies on the initial ingression surface or in the condensed member of the Type I sequence, while the poor Yinggan source rock and the lime-mud-mound along the fringe of the platform develop all in the Type II sequence. Under the condition of the same sea-level rising altitude and time, the ingression displacement (S 1 ) at the base border in Type I is larger than S 2 in Type II. Thus, the distribution of the source rock developed above the base border in Type I is wider than that in Type II. The maximal ingression range dominates the ultimate distribution of source rocks. Because S 1 is greater than S 2 , the relative rate of ingression on the base border of Type I is obviously bigger than that of Type II. The difference in ingression rate is one of the factors that lead to the superiority of the source rock at the base border in Type I to that Type II . Therefore, it is of great significance to study the spatial distribution, developing era and quality determination of source rocks by means of sequence stratigrahpy.Tarim Basin, Cambrian-Ordovician system, source rock, sequence type, ingression rate.The dominant factors for the development of marine source rocks have been studied in detail [1] . The development depends generally on the living environment of organisms that later turn into hydrocarbon-generative matrixes as well as on preservation conditions of organic matter. A good match of various factors, such as paleo-