The Lower Permian reefs in the world are distributed in the northwestern Pangean shelf, west slope of the Ural Mountains or eastern margin of the Russian Platform, the Permian Basin of North America and other localities. They occurred mainly in the former two areas. During the earlier period of Early Permian, the reefs were predominated by Palaeoaplysina or Palaeoaplysina-Phylloid algae, but to the later time of Early Permian, the reefs were replaced by Shamovella (Tubiphytes) and bryozoans as their framebuilders. The Early Middle Permian (Qixian Stage) reefs are discovered only in the Glass Mountains of North America, Pamirs and Aerge Mountains in West China. The Late Middle Permian (Maokouan Stage) reefs are regarded as the most well-developed reefs in the world. The Permian reefs of the Guadalupe Mountains become the most classic reefs which exhibit well distinct differentiation of sedimentary facies. The Middle Permian Tunisian reefs have been studied in details. The Middle Permian reefs are characterized by the abundance of sponges, bryozoans and Shamovella (Tubiphytes) as their framebuilders, and Archaeolithoporella, Shamovella and fistuliporids as their binders. The Late Permian reefs in the world occur in the Zechstein Basin of West Europe, western marginal shelf and northern marginal shelf of the Tethys, and some terranes within the Panthalassen ocean. The Late Permian reefs are well developed in South China, which constitutes a bright spot in the distribution of the Permian reefs. These reefs are characterized by coralline sponges, including the sphinctozoans and inozoans as their framebuilders. Archaeolithoporella and Shamovella (Tubiphytes) are usually formed as encrusting and binding organisms.

The Galeaspid is one major group of Agnatha in the Middle Paleozoic, and is mainly distributed in China and North Vietnam. Up to now, the fossil galeaspid agnathans found and described in China can be attributed to 68 species in 48 genera. 19 species in 14 genera of them are referred to the Silurian galeaspid agnathans, and are mainly distributed in Sichuan, Shaanxi, Hubei, Hunan, Anhui, Zhejiang, Jiangxi and Xinjiang Provinces (autonomous region). 49 species in 35 genera of them are referred to the Devonian galeaspid agnathans, and are mainly distributed in Ningxia, Sichuan, Guizhou, Guangxi and Yunnan Provinces (autonomous regions). The author firstly studied in detail the Middle Paleozoic galeaspid agnathans in China and the related correlation of galaespids-bearing strata. According to the occurrence order of the Middle Paleozoic galeaspids, nine galeaspid agnathans assemblages and one galaespids-bearing stratum can be recognized from the Early Silurian to the Late Devonian in China. The succession of Chinese galeaspid agnathans assemblages is closely related to the changes of palaeoenvironment, palaeogeography and palaeoconformation. Secondly, according to the study on the morphology and palaeoecology of galeaspids, the author thinks that most of them dwelt in the seacoast close to the palaeocontinents, including the delta and estuary, and lived a benthic life as filter feeder. Both the continents and expansive oceans became the major obstacles for their migration and dispersal because of their limited locomotory and dispersal capabilities, and thus galeaspids are biogeographically useful. Last, based on the distribution of Chinese galeaspid agnathans, and some information of the plate tectonics and palaeogeomagnetism, the author substantiates that the palaeogeographical relationships among three major eastern Asian blocks (i.e. the South China, the North China and the Tarim blocks) are very close during the Middle Paleozoic. They linked or drew near each other, and shared a highly endemic vertebrate fauna, namely “the Pan-Cathaysian Galeaspids Fauna”.

Abstract  Tectonically located in the West Kunlun-Karakorum orogenic belt at the junction between the Indian plate and the Eurasian plate, the Daftar area, Taxkorgan County, Xinjiang Uygur Autonomous Region, is one of the most important regions for the research on geological evolution of the Karakorum-Kunlun Mountains. Located in the heavily cool annoxic area in abdomen of central Asia, natural conditions of the West Kunlun-Karakorum area are very bad, transportation is inconvenient and field geological survey and research are grearly difficult. Because the regional geology of the area is less studied, the Permian microfossil was never reported from the sedimentary strata there. After geological survey and research, the Permian sporopollen fossils: Endosporites punctatus Gao， Wilsonites delicatus (Kosanke) Kosanke，Cordaitina spongiosa (Luber) Samolovich， Alisporites mathalensis  Clarke， Sulcatisporites ovatus (Balme and Hennelly) Balme were found in the Daftar area recently. According to the analysis on their combination features, the sporopollen fossils mentioned above basically belong to types of the Cathaysia flora realm. Based on researches on evidences of the Permian sporopollen fossils and data of previously published biostratigraphy and isotopic geochronology, the authors consider that the strata of clastic sedimentation in Daftar area, which was put into the Permian previously, may be the mélange which is composed of the Silurian and the Permian as well as other age layers.

The Miaohe-type Biota that are found from the upper part of Doushantuo Formation of Sinian at Taoying Town, Jiangkou County, northeastern Guizhou Province, South China includes macroalgal, possible metazoan, ichnofossil, and other fossils, and it was further more proved that the macrobiota was distributed widely in seafloor in Yangtze area, South China, during the Late Doushantuo Age of Sinian. Comparing with the Miaohe Biota in western Hubei Province and Lantian Flora in southern Anhui Province, we consider that the macrobiota mainly lived in the transitional area from the open platform to the platform edge slope facies. Studies on the Miaohe-type Biota in northeastern Guizhou, suggest that the life styles of macrobiota in the Late Doushantuo Age were mainly fixing on and attaching to the surface of seafloor, that the macrobiota lived in relatively calm-water shallow sea with abundant light, poor-oxygen, and a measure of water-energy, and that the ground macrobiota living on was the unfirmed soup-soft ground with rich water. During the Late Doushantuo Age, most of the macro-organisms were erect and semi-floating on the seafloor. They formed primitive “submarine grassland”, and produced oxygen to provide animals that depended on oxygen for living and reproducing. After these organisms were dead, their corpses laid on the surface of sediments and could be kept well in the environment with poor oxygen and fast sedimentation rate. Then they were buried rapidly by sediments. With the sediments being increased, these corpses were closed perfectly in the sediments to stop the decaying and decomposing process, and the macrobiota are preserved very well. The fast sedimentation rate, poor oxygen and comparatively calm-water environment are important factors making the biota be preserved well.

The Upper Cretaceous in Songliao Basin contains abundant trace fossils. Based on the observation of cores of 20 wells, 6 types of trace fossils including 15 genera and 20 species are identified in the basin. According to the distribution of these trace fossils in Songliao Basin, 5 ichnoassemblages in the Upper Cretaceous are distinguished as: (1) Scoyenia ichnoassemblage, which mainly includes Scoyenia gracilis, Skolithos, Planolites and Cubichnia, represents shallow water sedimentary environments with periodical exposure; (2)Skolithos ichnoassemblage, which is characterized by the abundance of Skolithos and Cylindricum with low diversity, reflects high energy environments; (3)Arenicolites ichnoassemblage, which is composed of Arenicolites, Polykladichnus, Skolithos, Planolites, Thalassinoides and Fugichnia with high diversity, represents shallow low energy environments; (4)Planolites ichnoassemblage, which is dominated by rich Planolites and Chondrites with low diversity, indicates anoxic quiet water environments; (5)Fuersichnus ichnoassemblage, which contains Fuersichnus, Glockeria, Gordia, Megagrapton and Planolites, suggests deep and relatively quiet water environments.

 By analysis of sedimentary facies correlation of 5 sections of the Jurassic, Combining with seismic data and well data , the Jurassic basin boundary of south margin of Junggar Basin, sedimentary facies evolution and basin pattern are established. The sedimentary facies correlation and paleocurrent measure of Houxia section and Toutun River section suggest that the two sections were formed  in the same sedimentary system during the Early-Middle Jurassic. The sedimentary facies of south margin of Junggar Basin changed from braided river–braided river delta–lacustrine facies to fluvial–lacustrine facies during the Early-Middle Jurassic. During the sedimentary period of Sangonghe Formation of Middle Jurassic, the basin boundary migrated southward to Houxia area and the sedimentary area came to the biggest. Swampy facies was well developed during the sedimentary period of Xisanyao Formation, and the Chepaizi-Mosowan horseback came into being from then on. The Junggar Basin and Tarim Basin were not geographically separated throughout the Early-Middle Jurassic by an ancestral version of the Tianshan Mountains. From the Late Jurassic to the Early Cretaceous, the sedimentary facies was characterized by rapid evolution from braided river–offshore-shallow lacustrine facies to braided river–alluvial fan facies. The distribution of the Kalazha Group conglomerate of Upper Jurassic show that tectonically active background and obvious uplift of the Tianshan Mountains during the Late Jurassic to the early age of Early Cretaceous, led to the widely different sedimentary system of Tarim Basin and south margin of Junggar Basin. The south Junggar Basin shrank northward obviously during the Late Jurassic to the early age of Early Cretaceous and the Bogeda Mountains became another important provenance system of south Junggar Basin.

Institute of Exploration and Development, PetroChina Southwest Oil and Gasfield Company, Chengdu, 610051 Sichuan
Abstract  The sedimentary environment of the Early Feixianguan Stage of Early Triassic is mainly inherited the pattern of the Late Changxing Stage of Late Permian. The northeastern Sichuan area is evaporate carbonate platform. The Feixianguan Formation of evaporate carbonate platform is a set of sulfate-bearing evaporate tidal sediments with aboundance of dolomite. The lower part is micro-tidal difference evaporate tidal sequence constituted by thin-bedded gypsum-bearing crystal, muddy-limestone and dolomicrite. The middle part is a set of great-tidal difference tidal sequence including oolitic shoal facies which is made up of bedded-oolite dolomite, oolite limestone, gypsum-tidal facies in sabkha environment which is constituted by bedded gypsum and gypsum-bearing gypsum-dolomite tidal faecies. The upper part is a set of evaporite quasi-tidal sequence with clear cycles which is made up of middle-thin-bedded mud abounding, gypsum-bearing muddy limestone and dolomicrite. Vertical combination of these three squences can be well correlated in evaporite platform area even though thicknesses of each squence are obviously different. Strongly dolomized oolite dolomites are the main reservoir of middle-large scale gas reservoir of the Feixianguan Formation in Sichuan Basin. According to its facies squence features, the oolitic rocks is divided into platform marginal oolitic bar and inner-platform oolitic bank. Platform marginal oolitic bar along the west margin of the evaporite platform was during the Feixianguan Stage, while the platform marginal oolitic bar along the eastern margin greatly shifted towards the basin during the Middle-Late Feixianguan Stage.

Lixian Slope is a large wide-gentle slope in the western part of Raoyang Sag, Jizhong Depression, Bohai Bay Basin. It is characterized by low gradient in the tendency and relatively obvious palaeotopographic differences in the trend, and it is constituted of different terrain units such as platform and monocline areas from north to south. Based on observation of cores and analysis on individual well facies and logging facies, and combining with numerous test data such as granularity, petrology and mineral analyses, etc, two different sedimentary facies, including “shallow water” delta, sand bar and beach of shallow-shore lacustrine, are recognised, which constituted the main reservoir of the Member 2 and the Lower part of Member 1 of Shahejie Formation of Paleogene in the study area. According to the differences of basic elements including sedimentary facies types and palaeogeomorphology in the trend, two different types of sandbody concentrating areas are classified in the study area, respectively named as delta facies sandbody concentrating area of monocline slope terrain unit and sand bar and beach facies sandbody concentrating area of platform terrain unit from south to north of the Lixian Slope. However, the forming conditions of subtle petroleum reservoir are different. It is suggested that the concentrating areas of sand bar and beach facies sandbodies of platform terrain unit are the favorable areas for searching subtle petroleum reservoir. Whereas compared to the sand bar and beach facies sandbody concentrating area of platform terrain unit, the exploration potential of the delta facies sandbody concentrating area of monocline slope terrain unit is relatively poor. On the other hand, the models of subtle petroleum reservoir are different on the inner, middle and upper belts of Lixian Slope. In general, the middle belt of the slope distributes a variety types of subtle petroleum reservoir which consist of sandstone updip pinch-out, lenticle lithologic oil reservoir and structural-lithologic oil reservoir. Vertically and laterally, these types of subtle petroleum reservoir overlaped each other and their oil-bearing beds were widespread on the middle belt of the slope, so the middle belt of the slop is considered as a main target area for subtle petroleum reservoir exploration.

 In the exploration of subtle oil reservoirs, the study of the relationship between available source rocks and oil reservoirs can lead us into a new way. So it is essential to make clear the variation and distribution of source rocks. Lacustrine-delta system was mainly developed during the sedimentary period from Member 4 to the lower part of Member 2 of Shahejie Formation in Dongying Sag. By analyzing on geochemistry, sedimentology and palaeoecology of over 100 drilling holes data, The paleo-lacustrine basin evolution can be divided into five stages which include intermittent lake at the beginning of rift, permanent closed lake through the acceleration of subsidence, closed-open lake during the maximum subsidence, deep open lake after the slowdown of the subsidence and shallow open lake through the acceleration of the fall of the base level. In different lacustrine stage or different geographical location of Dongying Sag, there exist different favorable sedimentary facies belts for source rocks bearing which have different geochemical features shown by the richness and types of organic matter. There are 6 kinds of favorable sedimentary facies belts in the upper part of Member 4, 4 kinds in the lower part of Member 3 and 6 kinds from the middle part of Member 3 to the lower part of Member 2. The integrated analysis on depositional environments and geochemical features shows that favorable sedimentary facies for source rocks bearing are influenced mainly by the lacustrine palaeogeography feature, the water depth and the sedimentary supply.

From viewpoint of quantitative palaeoecology, the relationship between dominance diversity of ostracoda (Hs) and water depth of palaeo-lacustrine basin (D) is simulated and established using ecology and palaeoecology data. The relationship is proved creditable based on seismic and sedimentary data of the paleogene of Dongying Delta, thus the water depth can be accurately calculated using quantitatively calculated dominance diversity. Taking the sedimentary period of the Member 3 of Shahejie Formation of Paleogene in Dongying Sag as an example, paleo-water depths of the 3 submember sedimentary periods were recovered and the planar isoline map was made. Results show that palaeo-water depth of Dongying Sag are respectively middle submember sedimentary period, lower submember sedimenrary period and upper submember sedimentary period in ascending order. Quantitative recovery of water depth of palaeo-lacustrine basin has an important significance in study of souce-reservoir-caprock of oil and gas in pertroliferous basin.

Some considerations of orogen—paleogeography in basins’ palinspastic reconstruction is, essentially, a basin analysis in the light of tectonic outlook of mobilism. The paper emphasized to look at a basin with an eye on the course of its development and dynamic evolution. The present situation of a basin might be only a relict (or a residual) part of a large basin in geohistory; or a sedimentary collage, with the sedimentary records from originally separated and independent basins each other. The existing sub-order tectonic units in a basin might be created in younger orogenies; another possibility might be that the original sub-order units were blurred or concealed by later tectono-thermal events. It might be a common sight that the uplifts (including the sub-order uplifts) sometimes rised and sometimes fell in formational process of a basin; correspondingly, the basins sometimes separated and sometimes merged together. There was an organic relation between the pan-continental cycles and large basin evolution, namely, the large basin developing might be constrained by the neighboring oceanic evolution and orogenic process. So, an analysis on coupling between basin and orogeny should be a key to correctly understand basin’s dynamic evolution. To be reflected in palinspastic reconstruction, orogen-paleogeography suggested a combination of an autochthonous reconstruction and a non-autochthonous one, with stress on the latter. There were two ways for non-autochthonous paleogeographic reconstruction: quantitative (for example, based on paleomagnetic data) and qualitative ones. The paper discussed five key points in the qualitative reconstruction: 1) timely, to combine a study of “reversed succession”, 2) spatially, to synthesize a study of “inversion tectonics”, 3) to emphasize significance of structural restoration in paleogeographic reconstruction, 4) reformation events in the period of basin formation serving as a link between past and future,  and 5) a study on basin geodynamics matched the orogenic geodynamics.

Dow proposed a method by using the differential of vitrinite reflectance of the upper and lower strata to estimate the eroded strata thickness at an unconformity surface in 1977. This method is still widely used in China. But some Chinese scholars have already recognized the irrationality of the method and then have proposed some revising methods. Among them, the “method of the highest paleotemperature(MHP)” is representative due to its rational idea. In order to estimate the eroded strata thickness at an unconformity surface by using vitrinite reflectance data more reasonably and more conveniently, the author has improved the MHP in this paper and got a new method. The improved new method not only inherited the rational idea of MHP but also much simplified calculation process. There are some premises in estimating the eroded strata thickness of the top surface of a structural layer by using Ro data. If all the premises are established, we can directly project the linear regressive relationship between ln (Ro) and H of this structural layer upward to the value of ln (0.2) and get the approximate paleosurface’s position. The distance between paleosurface and unconformity surface is the expected erodedstrata thickness. Recalculating the Dow’s original data with MHP and the new method, we can get the results of 2735 m and 2537 m respectively. These two close results show the feasibility of the new method. And compared with MHP, the new method is more convenient. Both of the close results are far away from Dow’s result of 500 m. Then the author discusses the irrationality of Dow’s result and principle from several aspects. The new method will be widely applied in many branch disciplines of geology.