“China” in this paper refers to the mainland and land areas of Hainan Island and Taiwan. The paper is composed of two lithofacies paleogeography maps of China of the early and late ages of the Early Cambrian and corresponding explanation text. The most important characteristics of these two maps are "two troughs alternating with three platforms". The two troughs are the Tianshan–Beishan–Mongolia–Liaoning–Jilin Trough and the Kunlun–Qinling Trough. The three platforms are the Junggar–Mengolia–Xinganling Platform,Tarim–Qaidam–North China Platform, and Tibet–South China Platform. The boundaries of these two troughs and three platforms are defined on the basis of tectonics, strata, rocks, lithofacies and other data. Most of the boundaries are accurate, and only in some places they are inferred. The Tianshan–Beishan Trough can be further divided into secondary lithofacies paleogeography units, but other troughs are difficult to be subdivided. Among the three platforms, South China, North China and Northwest China are well studied, their secondary lithofacies paleogeography units are defined on the basis of accurate quantitative data and quantitative maps, and the lithofacies paleogeography of the early age of the Early Cambrian can be differentiated from that of the late age. Other areas are less well-studied, and secondary lithofacies paleogeography units are difficult to be delineated out. The lithofacies paleogeography maps of these areas are qualitative. Therefor, these two lithofacies paleogeography maps of the Early Cambrian of China are different in study depth for different areas, and are quantitative in some areas and qualitative in other. These maps reflect both the research achievements of the present writers and the present geological study depth of our country. In these maps, merits coexist with flaws, and facts coexist with inference. Welcome criticism from the readers.
The Upper Devonian and Carboniferous can be divided into Donghetang Formation, Ganmulike Formation, Bachu Formation , Kalashayi Formation and Xiaohaizi Formation. The geologic time of Donghetang Formation and Ganmulike Formation belong to Late Devonian, the geologic time of Bachu Formation is Early-Middle Tournaisian of Early Carboniferous, the geologic time of Kalashayi Formation is from Late Tournaisian to Bashkirian, the geologic time of Xiaohaizi Formation is from Late Bashkirian to Moscovian. There are terrigenous clastic rocks and carbonate rocks. There are 5 facies, i.e. fluvial facies, delta facies, littoral facies, neritic facies,carbonate platform facies , platform edge facies, and 12 subfacies and 33 microfacies.There were 4 trangressions from Late Devonian to Carboniferous, and the trangression was from east to west, and increased gradually. Because of a lot of terrigenous supply, the sedimentary facies were mainly littoral facies and nertic facies during Donghetang Age. From Bachu Age to Xiaohaizi Age, the trangression area increased, and the sedimentary facies were mainly carbonate platforms.
This paper has discussed the Carboniferous lithological and palaeogeograpgical characteristics inthenorthwest ofChina, by the analysis of outcrop sedimentary facies , clastic composition , trace element andREE ,particlesize ,claymineral ,paleocurrent,etal.,inthecombinationwithregionalstratigraphic,palaeotologicandlithologicdata.IntheEarly Carboniferous , there were 5 oldlands,i.e. Aletai oldland, South Junggar oldland,DunhuangZoulangoldland, Alxaoldland,Longxioldland,and10facies,i.e.Kumasulittoralneriticfacies,BuerjinFuyunlittoralneriticfacies ,Bogedalittoral-neritic facies ,North Junggar bathyal-abyssal facies, NorthTianshanbathyalabyssalfacies ,Kelameilialluvial fan–lacustrinefacies,Kelamayialluvialfanlacutrinefacies,SouthTianshanNorthQilianlittoralneriticfacies,Qaidam carbonateplatformfaciesandmiddleQilianlittoralneriticfacies.ThecharacteristicsoflithofaciespalaeogeographyoftheLateCarboniferousaredifferentfromthoseoftheEarlyCarboniferous,andtheareaoftheoldlanddecreases.IntheLateCarboniferous ,therewere5oldlands,i.e.Aletaioldland,NorthJunggaroldland,Mazongshanoldland,DunhuangAlaxaoldland,middleTianshanoldland,and9facies,i.e.Kumasufluvialandlacutrinefacies,BuerjinFuyunfluvialandlacustrinefacies, Kelameili-Balikun littoral-neriticfacies ,BuleKuerleHongliuyuanlittoralneriticfacies,KelamayiHamibathyal–abyssal facies, Wulumuqi organic moundshoalfacies,Qaidam carbonateplatformfacies ,Zongwulongshanneritic-abyssalfaciesand Qilianlittoralneriticfacies.The bathyalabyssalfacies,littoralfacies,neriticfaciesanddeltafaciesarebeneficial to the exploration of oil and gas.
Based on the detailed research on outcrop the s ections of the Devonia in Zen'an Basin, South Qinling, the Devonian can be divided into four depositional systems, i.e coast system, carbanate system, self system and slope—basin system, with the characteristics that depositional systems and litofacies aemblages are different from on the belt to another through north to south while extending west to east in spatial. In terms of the strata overlaping froms out to north and the trend of facies type scanging from distal facies in the south to proximal facies in the north and terrigenous sediments transported from north to south, there souldbea disappeared ancient land in the north. According to the evolution of depositional systems and litofacies aemblages, the history of the Devonian depositional basin can be divided into three main evolutionary stages, with careinitial depretion period, depressional period and strong rift faulting period, their paleogeographic pattern was varying with in different stages. From north to south it displayed the pattern so fancient land coast self in Givetian stage in Mid Devonian, ancient land carbonate flat self in Frasnian stage, and upliftcoastselfslopebasinflat in Famennian stage in Late Devonian.
Kuruketage region belongs to Kuruketage stratigraphic subregion of Tarim stratigraphic region in northwest stratigraphic region classification. Its sedimentary feature was influenced by Tarim Basin, but it’s not the same as Tarim Basin’s. This area was rarely studied before. According to field outcrop data, there are obviously different between the sedimentary feature of Ordovician of north and south area of Kuruketage region. In the north area, it’s mainly of carbonate rock formation in lithology and of shallow-sea facies fossil such as Trilobita Cepohacopoda, Brachiopoda and Anthozoa in fossil feature. While in south area, it’s mainly of flysch formation in lithology and of deep-sea facies fossil such as Graptolithina in fossil feature. So it is obviously that the north area of Kuruketage region was higher than that of the south area in Ordovician period which was reflected by sedimentary feature such as lithology, ancient fossil, sedimentary structure and sedimentary sequence. In the study area, tableland sea , wide continental shelf , shelf margin slop , deep sea basin and shallow sea sedimentary facies are developed. Four sedimentary facies patterns can be deduced from sedimentary facies and its extending feature. They are tableland sea—wide continental shelf sedimentary facies pattern, basin margin slope—deep sea basin sedimentary facies pattern, sea-land transitional facies—shallow sea sedimentary facies pattern and alluvial fan—delta sedimentary facies pattern. A theory foundation is laid for further studying and oil exploration.
Deep-water sediment waves are wavy depositional bodies of large-scale, which are well developed on the seafloor. They have been universally interpreted as contour-current deposits or turbidity–current deposits. Incorporated with the new development of the theory of internal waves, the generation mechanism of deep-water sediment waves by internal waves has been studied on the basis of the hydrodynamics of internal-wave deposition. Several conditions have been generalized as follows: 1）Using submarine flows only to interpret the origin of sediment waves can’t meet the require of velocity and thickness of flow sediments to form large sediment waves. 2) Internal waves can induce bottom currents and form depositional bedforms of larger scale than those formed by surface waves. 3) Internal waves can build sediment waves of large scale. The origin of sinusoidal, asymmetric and climbing wavy units of sediment waves can be reasonably interpreted by internal waves alone. The sediment waves of sinusoidal wavy shape can be formed either by the progressive internal waves propagating along the interface which is relatively high above the seafloor or by standing internal waves. Sediment waves of asymmetric wavy shape can be formed either by the progressive internal waves propagating along the interfaces near the seafloor or internal solitary waves. When the internal wave-induced bottom currents increase further, the sediment waves of climbing wavy shape should be formed. 4) The progressive internal waves can build large sediment waves that migrate in the opposite direction of the propagating direction of the internal waves. The progressive internal waves propagating toward the deep-sea basins can build large sediment waves with the up-slope migrating direction. This is the reason why sediment waves well developed on the seafloor migrate mainly up-slope.
The palaeovegetation during Late Pliocene in the Zanda Basin, southwestern Xizang was mainly built up of dwarf halfshrub desert, steppe, sub-alpine needle-leaf forest and montane evergreen needle-leaf forest, possibly mixed with some deciduous broad-leaf forest and evergreen broad-leaf forest during that time. By comparison with the living environments of modern vegetation types, the climate was inferred as cold, arid or semi-arid to semihumid, which might be a kind of subtropical subalpine one. It also shows that during Late Pliocene the lowest elevation in the basin might be a little lower than 2 500 m and the topographic form was probably similar to that of today in Zanda, which is lower in the south and higher in the north. The western plateau might be uplifted around 1 000 m from then on. Compared with that of the central Himalayan area, which is around 4 000 m suggested, this value is much smaller.
In west Qaidm Basin, 17 oil fields with Tertiary source rocks have been found; the main source rocks are Lower Ganchaigou Formation of terrestrial facies of Eocene. Some people thought that the Low Ganchaigou Formation be formed by marine transgression and named it Lower Ganchaigou Transgression. Recently, in a paper, the Lower Ganchaigou Formation was considered as lagoon facies instead of deep lake facies. In addition, it was regarded as relict lagoon broken from southwest bay lagoon of Tarim Basin in Eocene by Altun shift fault, or as east part broken from Tarim Basin prototype. Based on such opinion the authors of that paper thought that the direction of exploration in west Qaidm Basin should be reconsidered. Maps of Paleocene and Eocene sedimentary facies and typical marine biologic groups of Tuilok, Altax, Qimgon, Gejitar and Karatar Formations in bay of West Tarim Basin provided inThis paper differs completely from that of Lulehe and lower Ganchaigou Formations in Qaidam Basin. Evidence can not support that the west Qaidm Basin and southwest bay of Tarim Basin belong to one same basin or sedimentation unit in Paleogene. The theory of source—controlling (the distribution of oil and gas fields are controlled by source sags) is still the principle which is efficient in directing petroleum exploration in continental sedimentation in west Qaidm Basin.It is misunderstanding to regard source rocks of oil fields founded in southwest Tarim Basin as Paleogene marine sediments and it is also misleading to use the exploration method of Paleogene marine sediments into exploration of Paleogene continental sediment in west Qaidm Basin. Scientific palaeogeography view will do more help for explorationist in explorative deployment.
Jurassic reservoir in Northwest edge of Junggar Basin exists apparent difference in reservoir rock type. The controlling effects of reservoir rock type upon reservoir property are also apparent. There are a few pore types in reservoir rock, but different pore types have apparent difference from each other in several aspects such as pore scale, abundance and effectiveness, in which secondary solution pore, initial intergranular pore and residual intergranular pore are the most important effective pore types. Good linear relation exists between log permeability and porosity, based on the relation a series of certain limits are defined to evaluate reservoir property. The 5 grades are subdivided correspond to the prevalent sorting grades of sand reservoir to some extent. By cluster analysis on a large number of mercury injection parameter samples, pore structure is subdivided into 4 types. Through contrast of the statistical parameters and typical curve shape, effectiveness of each pore structure type is evaluated quantitatively and qualitatively. Finally, porosity and permeability grade, pore type, pore structure type and reservoir rock type are combined to give a synthetic evaluation on Jurassic reservoir of Northwest edge in Junggar Basin.
