The Balfour Formation has a pronounced lithological variation that is characterized by alternating sandstone- and mudstone-dominated members. The sandstone-dominated Oudeberg and Barberskrans Members are composed of l...The Balfour Formation has a pronounced lithological variation that is characterized by alternating sandstone- and mudstone-dominated members. The sandstone-dominated Oudeberg and Barberskrans Members are composed of lithofacies that range from intraformationai conglomerates to fine-grained sediments, whereas the mudstone-dominated members (Daggaboersnek, Elandsberg, and Palingkloof) are dominated by the facies Fm and FI. Petrography, geochemistry, and a paleocurrent analysis indicated that the source rock of the Balfour Formation was to south east and the rocks had a transitional/dissected magmatic arc signature. The sandstones-rich members were deposited by seasonal and ephemeral high-energy, low-sinuous streams, and the fine-grained-rich members were formed by ephemeral meandering streams. The paleoclimates have been equated to present temperate climates; they were semiarid becoming arid towards the top of the Balfour Formation. This has been determined by reconstructing the paleolatitude of the Karoo Basin, geochemistry, paleontology, sedimentary structures, and other rock properties, like color.展开更多
The Balfour Formation was subdivided into five members based on lithological variation that is characterized by alternating sandstone-and mudstone -dominated members.The sandstone dominated Oudeberg and Barberskrans m...The Balfour Formation was subdivided into five members based on lithological variation that is characterized by alternating sandstone-and mudstone -dominated members.The sandstone dominated Oudeberg and Barberskrans members are composed of lithofacies that range from intraformational conglomerates to fine-grained sediments,whereas the mudstone dominated members(Daggaboersnek, Elandsberg and Palingkloof) are dominated by the fine-grained facies(Fm and F1).Petrography,geochemistry and palaeocurrent analysis indicated that the source rock of the Balfour Formation was to展开更多
This study was carried out to investigate the impact of drainage basin’s lithostratigraphy on the quality and type of stored water in the Mujib dam reservoir. The water samples were collected on a monthly basis from ...This study was carried out to investigate the impact of drainage basin’s lithostratigraphy on the quality and type of stored water in the Mujib dam reservoir. The water samples were collected on a monthly basis from surface water from January 2012 to December 2015. The classifications of collecting water samples for domestic and irrigation purposes were based on different physico- chemical parameters such as pH, EC, TDS, TSS, Na+, K+, Ca2+, Mg2+, Cl-, SO42-, HCO3- , NH4+, NO3- , NO2- , SAR, RSC, SSP, RSBC, PI, MAR, KR, and TH. All analyzed water samples were satisfied the Jordanian permissible limit and graded as “fresh water”. The hydrochemical indices (Mg/Ca and Cl/HCO3) and Cation Exchange values (CEV), indicating that the surface water chemistry is due to the rock weathering minerals with respect to their inland origin. The water samples have complied within the respective limits in respect of pH, EC, SAR, RSC, RSBC, MAR, KR, SSP and PI, and hard in respect of TH which may be due to the dissolution of the weathered rocks. Abundance of cations and anions is in the following order: Ca > Na > Mg > K and HCO3 > SO4 > Cl > NO3 during the period 2013-2015 and SO4 > HCO3 > Cl > NO3 through 2012. Thus, calcium and bicarbonate–sulfate are the dominant ions present in the surface water of this study. Piper diagram suggested that carbonate and gypsum weathering is the dominant process controlling reservoir water chemistry in the basin area. The quality and type of surface water can be modified by the lithology of the catchment area. The hydrogeochemical study of Mujib reservoir water indicated that the water quality is safe for drinking and agricultural purposes.展开更多
The Khao Ya Puk Formation (>400 m thick) is well exposed in the Nakhon Thai Region, and is subdivided into three members. The Khao Ya Puk Formation overlies conformably on top of the anhydrite layer of the upper ro...The Khao Ya Puk Formation (>400 m thick) is well exposed in the Nakhon Thai Region, and is subdivided into three members. The Khao Ya Puk Formation overlies conformably on top of the anhydrite layer of the upper rock salt Maha Sarakham Formation. In turn, it is overlain unconformably by the Phu Khat Formation. The Khao Ya Puk Formation is interpreted to have been deposited by freshwater lake area in arid climate inland subkha in the Late Cretaceous. Lithostatigraphically, Khao Ya Puk Formation can be correlated with the Phu Tok Formation that has been deposited in the Khorat-Ubon basin and Udon-Sakon basin of the Khorat Plateau.展开更多
The lithostratigraphy and biostratigraphy specifications of the Sarvak Formation are considered to study in wells No. 2, 16 and 66 of Rag-e-Safid oilfield. They are located at the southeast of Ahwaz (the southwest of ...The lithostratigraphy and biostratigraphy specifications of the Sarvak Formation are considered to study in wells No. 2, 16 and 66 of Rag-e-Safid oilfield. They are located at the southeast of Ahwaz (the southwest of Iran). The lithology of the Sarvak Formation in all the wells mostly consists of limestone. The depth of the Sarvak Formation in well No. 2 is 720 m;in this well, the Sarvak Formation overlies the Kazhdumi Formation and underlies the Papdeh Formation. Vertical distribution of recognized foraminifera, macrofossils and calcareous Algae identifies two biozones: 1) Favusellawashitensis Range zone;2) Praealveolinacretacea-Ovalveolina ovum & Rudistfragment Ass. zone. The thicknesses of the Sarvak Formation in wells No. 16 and 66 are about 100 m and 108 m, respectively;in a part of the Sarvak Formation, drilling was completed, while its upper boundary is covered with the Papdeh Formation, in both wells. In terms of biostratigraphy studies in wells No. 16 and 66, one assemblage biozone is recognized as Praealveolinacretacea-Ovalveolina ovum & Rudistfragment Ass. Zone, similarly. Finally, the age of the Sarvak Formation is determined as the Cenomanian in three considered wells.展开更多
Non-marine Cretaceous rocks are widespread in northeastern Thailand and is well known as “the red bed” Khorat Group. The Sao Khua Formation is in the upper half of the Khorat Group which is comprised of six formatio...Non-marine Cretaceous rocks are widespread in northeastern Thailand and is well known as “the red bed” Khorat Group. The Sao Khua Formation is in the upper half of the Khorat Group which is comprised of six formations. This formation was named and defined at the type section for the rocks between the restricted PhraWihan Formation and the Phu Phan Formation in the drainage area of the Huai Sao Khua, an intermittent stream that flows westward parallel to the highway between Nong Bua Lamphu and UdonThani Provinces. It contains richest and most diverse vertebrate and invertebrate Mesozoic fossils in Thailand. The Sao Khua Formation is characterized by the sequence of the fining-upward successions of at least 4-5 megacycles throughout the formation with the total thickness ranging between 400-700 meters. Each cycle starts with a channel lag conglomerate which the clasts consist totally of re-worked calcrete nodules. The conglomerates were overlain by fine-to medium-grained sandstones of point bar deposit. Finally, the top part of each cycle was covered by a succession of fine-grained floodplain deposit that makes up 60%-70% of the formation. Paleosols are commonly found in the Sao Khua Formation within the floodplain sequence and their geochemistry indicates a semi-arid paleoclimate. Based on lithostratigraphy, the Sao Khua Formation is interpreted to have been deposited by a meandering river system under a semi-arid climate condition. The age of the formation is assigned as the Hauterivian-Late Barremian based on vertebrate and bivalves fossils.展开更多
The Mamfe Basin has been the subject of many studies,but some debates persist,especially concerning the stratigraphic nomenclature,corundum origin,and marine transgression.The aims of this work are(1)to propose a new ...The Mamfe Basin has been the subject of many studies,but some debates persist,especially concerning the stratigraphic nomenclature,corundum origin,and marine transgression.The aims of this work are(1)to propose a new lithostratigraphic nomenclature of the Mamfe Basin formation based on new field observations,(2)to determine the source rock distribution and the origin of gem deposits and(3)to correlate the Cameroon section of the Mamfe Basin with the Nigerian deposits.The main results show that the name Manyu River Group is more appropriate as the Manyu River crosses all the facies in the Mamfe sedimentary Basin belonging to the Manyu Division.According to the facies analysis,the age of deposition,the mineralogic and geochemical data such as the V vs.Al2O3andΣREE vs.Al_(2)O_(3),TiO_(2)MgO,Na_(2)O,P_(2)O_(5),and CaO diagrams,this Group is composed of at least five Formations,including four Cretaceous Formations,from bottom to top:the Etoko Formation(alluvial and fluvial channel to fluvio-lacustrine deposits),the Nfaitok Formation(lagoonal deposits),the Bachuo Ntai Formation(fluvial braided channels or fluvio-deltaic environment)and the Eyumojock/NsanaragatiFormation(fluvio-lacustrine deposits)and the new Cenozoic Formation named Bakebe Formation(fluvio-lacustrine deposits).The gem minerals such as corundum,rutile,or tourmaline in the Cretaceous deposits of the Mamfe Basin are mainly detrital as indicated by the presence of worn shapes and fragments of these minerals.The presence of sapphire in the AlboCenomanian deposits indicates a Precambrian age of the felsic source rock,likely the plutonic rocks such as granite or pegmatite as indicated by the abundance of tourmaline and high LREE/HREE ratios(14.81–34.29)and slightly negative and positive Eu anomalies(0.85–1.15).This marine incursion in the Mamfe Basin was probably from West Nigeria,according to the geographic location of the Mamfe Basin and the general palaeogeographic evolution of the Benue Trough.展开更多
This paper compiles lithostratigraphic and geochronological data obtained for the Palaeoproterozoic glacial diamictite-bearing successions,and thereby provides insights into understanding the geological processes caus...This paper compiles lithostratigraphic and geochronological data obtained for the Palaeoproterozoic glacial diamictite-bearing successions,and thereby provides insights into understanding the geological processes causing the Huronian Glaciation Event.The majority of evidence for appearances of this glaciation event can be related to the Kenorland supercontinent breakup,allied to significant atmospheric change,as well as blooms of biogeochemical oxygenic photosynthesis.In this paper,the Huronian Glaciation Event is constrained to have occurred synchronously during 2.29-2.25 Ga,accompanied by dramatic environmental changes characteristic of the Great Oxidation Event which includes the pre- 2.3 Ga hydrosphere oxidation and the post-2.3 Ga atmosphere oxygenation.展开更多
The growth strata was investigated in the Early Cretaceous deposits including Fahliyan, Gadvan and Dariyan formations in the Well 3 that is located between Qatar-Fars height and Hormuz Strait in Persian Gulf. This stu...The growth strata was investigated in the Early Cretaceous deposits including Fahliyan, Gadvan and Dariyan formations in the Well 3 that is located between Qatar-Fars height and Hormuz Strait in Persian Gulf. This study is based on the lithostratigraphic analysis and microfossils distribution. Lithostratigraphically, the Well 3 is divided into three rock units including Fahliyan, Gadvan and Dariyan. Based on the microfossils content, the age of studied successions is Berriasian to Aptian. The comparison of seismic studies, lithostratigraphic analysis and microfossils distribution show that growth and generation of anticlines construct in the Early Cretaceous. As a result, the Fahliyan, Gadvan and Dariyan rock units have potential reservoir and oil trap.展开更多
The Albertine Graben is one of the most petroliferous onshore rifts in Africa. It forms the northemmost termination of the western arm of the East African Rift System. Its surface exposures were first studied by Wayla...The Albertine Graben is one of the most petroliferous onshore rifts in Africa. It forms the northemmost termination of the western arm of the East African Rift System. Its surface exposures were first studied by Wayland [1] and Pickford et al. [2] among others. Pickford et al. [2] especially developed the basic stratigraphic framework of the graben which was later modified by the government geoscientists and international oil companies using subsurface data. However, the stratigraphic units were not fully and formally described, and have been used informally in different and often confusing ways. The current study therefore aims to solve this challenge by establishing a coherent stratigraphic scheme for the entire graben through an integral study of surface and subsurface data. The study involves precise description of the type and reference sections for various formations both in exposure and wells; and has therefore led to the development of lithostratigraphic columns of different basins in the graben. The approach reveals that the Semliki area, south of Lake Albert, has the most complete sedimentary succession in the graben, spanning the period from middle Miocene (ca 15 Ma) to Recent. It also reveals that platform deposits, which form a small fraction of the thickness of the basinal succession, represent a highly condensed sequence which only saw deposition at times of Lake highstand.展开更多
This paper concerns deals with the Mongolian regional stratigraphic classification of sedimentary, sedimentary-volcanogenic sediments, and metamorphic complex spread over the territory of Mongolia according to the new...This paper concerns deals with the Mongolian regional stratigraphic classification of sedimentary, sedimentary-volcanogenic sediments, and metamorphic complex spread over the territory of Mongolia according to the new International Chronostratigraphic Chart [1]. The regional stratigraphy of Precambrian-Cenozoic rocks of the Mongolian territory was studied by Dorjnamjaa et al. [2]. So, this paper provides for the stratigraphy and correlation of key sections through the Archean-Proterozoic-Mesozoic-Cenozoic of various areas of Mongolia. In this paper, the author introduces the most important results indicating the key reference sections for the first time and put into a broad regional context. The characterization and geologic mapping of lithological units provided an essential basis for the lithostratigraphy, biostratigraphy and chemostratigraphy. Especially key biostratigraphic aspects are the phenomenon of faunal succession. The basic lithostratigraphic unit is the formations and groups which have been successful mapped. At present in Mongolia for Precambrian period (systems and series) 30 formations and groups, for Paleozoic—about 250 formations and groups, for Mesozoic—102 formations and groups, for Cenozoic—27 formations, members, and beds are distinguished. The auxiliary stratigraphic units are members, beds which should be mapped depending on great extent of detailed study. In the regional stratigraphical classification, there are two primary kinds of stratotypes [3]: a) unit stratotypes, which serve as the standard of definition for a stratigraphic unit, and b) boundary stratotypes, which serve as the standard of definition for a stratigraphic boundary. These aspects, in particular gradational boundaryas far as possible were examined for example for Archean-Paleoproterozoic (by geochronologic data), Ediacaran-Early Cambrian (by soft-bodied fossils, trace fossils and small shelly fossils), Ordovician-Silurian (by beyrichiidostracodes), Devonian-Carboniferous (by conodonds), Paleocene-Eocene (by mammals), Oligocene-Miocene (by small rodents) systems and series.展开更多
Fahliyan Formation is importance in terms of Zagros stratigraphy since it is one of the oil reservoir rocks at the Jurassic-Cretaceous boundary. This rock unit consists of two types of deep and shallow facies in Zagro...Fahliyan Formation is importance in terms of Zagros stratigraphy since it is one of the oil reservoir rocks at the Jurassic-Cretaceous boundary. This rock unit consists of two types of deep and shallow facies in Zagros area. Recognition of bio-zones as well as discontinuity or continuity between the studied formation and the encompassed stratais taken into consideration. In order to study biostratigraphy on Fahliyan Formation, the stratigraphic section of Kuh-e-siah in the north-east of Fars Province was selected. In this section, Fahliyan Formation is measured 345 m consisting of thin to medium-bedded of limestone with the interbeds of sandy and dolomitic limestones. Fahliyan Formation conformably overlies Surmeh formation and underlies the marls of Gadvan formation. Vertical distribution of the identified foraminifers and calcareous algae confirms presence of 3 biozones in the sediments of Fahliyan Formation, as follows: 1) Calpionella alpina zone;2) Pseudochrysalidina conica zone;3) Pseudocyclammina lituus-Trocholina sp. assemblage zone. Based on Established biozones, the age of Fahliyan Formation in Kuh-e-Siah section was determined from Berriasian to Late Hauterivian.展开更多
During the Carboniferous Period,the Qinghai-Tibetan Plateau and its surrounding areas were located in quite different paleogeographic positions with various sedimentary and biological types.It is important to systemat...During the Carboniferous Period,the Qinghai-Tibetan Plateau and its surrounding areas were located in quite different paleogeographic positions with various sedimentary and biological types.It is important to systematically compile and summarize the Carboniferous strata and biotas of the Qinghai-Tibetan Plateau and its surrounding areas,to establish an integrated stratigraphic framework for correlation,and to reconstruct the paleogeography for correctly understanding the breakup of the Gondwana Continent and the evolution of the Paleo-Tethys Ocean in the Late Paleozoic.The Carboniferous of the Qinghai-Tibetan Plateau and its surrounding areas can be subdivided into the Gondwanan,Cimmerian,and Tethyan types.The Gondwanan-type Carboniferous are distributed in the North Himalayan,Kangmar-Lhunze,and Zanda-Zumba regions of the South Tibet Subprovince and northern India-Pakistan Area,where only the Mississippian is developed and the biota is of Gondwanan affinity.The Cimmerian-type Carboniferous,which are found in the Baoshan,Tengchong,Coqen-Xainza,LhasaZayu,Nagqu-Biru,and South Qiangtang regions,as well as Shan-Thai and South Afghanistan-Pamir areas,also represent only the Mississippian strata,but their biota is characterized by mixed characters of European,South China,Australian,and North American types.The Tethyan-type Carboniferous are distributed in the Tanggula Mountains,Hoh Xil-Bayanhar,ChamdoHengduanshan,Tiekelike,West Kunlun,Karakorum,East Kunlun-Central Qinling,and Qilian regions,where the Carboniferous succession is well developed,and the biota is of warm-water Tethyan affinity.The biostratigraphical correlation of the Gondwanan-type and Cimmerian-type Carboniferous is based mainly on conodonts and additionally on brachiopods and rugose corals.The Mississippian of the Tethyan-type Carboniferous is correlated mainly by using rugose corals and brachiopods,whereas in the Pennsylvanian foraminifera(fusuline)and conodonts are regarded as primary fossil groups,subordinated by rugose corals and brachiopods.Adhering to the International standard chronostratigraphy of the Carboniferous,we have reconstructed a framework of the litho-and biostratigraphic subdivision and correlation of the Qinghai-Tibetan Plateau and its surrounding areas.Further studies should focus on isotope geochronology,geochemistry,paleoclimates,and paleoenvironments of the Carboniferous in the Qinghai-Tibetan Plateau and its surrounding areas.展开更多
Rocks of the Qinghai-Tibetan Plateau(QTP)host abundant Triassic fossils.So far,the well established marine fossil sequences based on ammonoids,conodonts,bivalves,brachiopods,radiolarians,and terrestrial spora-pollen s...Rocks of the Qinghai-Tibetan Plateau(QTP)host abundant Triassic fossils.So far,the well established marine fossil sequences based on ammonoids,conodonts,bivalves,brachiopods,radiolarians,and terrestrial spora-pollen sequence have become standard for biostratigraphic correlation of the QTP.For much of Triassic time,the QTP occupied a marine setting as suggested by the dominance of marine deposits.The main sedimentary types represented in the Triassic successions include littoral to shallow marine clastic rocks,shallow marine carbonate platform carbonates,bathyal to abyssal slope carbonates intercalated with clastic and siliceous deposits,coal-bearing clastic strata contained within paralic facies deposits,and littoral and terrestrial volcaniclastic rocks.These deposits are organized into four stages in ascending order:(1)Early Triassic deposits that record marine transgression,including extensive shallow marine carbonate platform strata.(2)Middle Triassic Ladinian to Late Triassic Carnian deposits,including thin-bedded limestone,fine clastics,and siliceous rocks,that accumulated at greater depths than underlying Early Triassic strata and reflect the peak of the transgression.Magmatic activity appears to have occurred in some areas during this stage.(3)Late Triassic Norian deposits that record the onset of marine regression as suggested by the widespread occurrence of platform carbonates.It is noteworthy that stage 3 deposits of the Qin-Qi-Kun area in the northernmost region of the QPT is dominated by terrestrial strata and displays evidence of local erosion.(4)Late Triassic Rhaetian littoral and shallow marine clastic and coal-bearing deposits that preserve the record of continued marine regression continued.The Indus-Yarlungzangbo Suture Zone(IYSZ)appears to have been the rifting axis during Triassic time as suggested by sedimentary facies trends that reflect deepening to south and north.Thus,the Himalaya Block to the south of the IYSZ was part of the passive margin of Gondwana whereas the north side of the IYSZ,including the Gangdis(or Lhasa)and South Qiangtang blocks,belonged to the passive margin of Eurasia.The similarity of rocks of the Bangongco-Nujiang Suture Zone(BNSZ)to the north of the IYSZ with those of the Gangdis Block to the south and the South Qiangtang Block to the north does not support the contention that the BNSZ was a rift axis during Triassic time.Results of palaeobiological research also suggest that the IYSZ rather than BNSZ was a biogeographic boundary during the Triassic.Early and Middle Triassic break-up of Pangea was accompanied on the QTP by rifting along the IYSZ.The expression of crustal shortening induced by the Indosinian Orogeny on the QTP is largely a change of sedimentary facies induced by Late Triassic uplift.Deposits of the Gangdis to South Qiangtang regions of the QTP record a transition from shallow marine carbonate platform deposits to littoral and paralic coal-bearing strata.Moreover,the stratigraphic succession of the Qin-Qi-Kun area preserves a transition from littoral clastic deposits to terrestrial facies and local erosion.展开更多
The Silurian palaeontology and stratigraphy of the Qinghai-Tibetan Plateau have been studied for more than100 years.With the launch of the Second Tibetan Plateau Scientific Expedition and Research,it is necessary to u...The Silurian palaeontology and stratigraphy of the Qinghai-Tibetan Plateau have been studied for more than100 years.With the launch of the Second Tibetan Plateau Scientific Expedition and Research,it is necessary to update the summaries of the Silurian stratigraphy and fossil assemblages of the Qinghai-Tibetan Plateau and their correlation with its surrounding areas.In this study,we have selected 33 sections from the Qinghai-Tibetan Plateau and its surroundings areas,summarised the available data in terms of stratigraphic regionalisation,lithostratigraphy,chronostratigraphy,and biostratigraphy,and divided the study area into four stratigraphic provinces:the Xizang-Western Yunnan-Western Sichuan Province,the KunlunQilian Province,the South China Province,and the Tarim Province.In general,the Silurian strata in the Qinghai-Tibetan Plateau is more complete than those in other areas of China.Palaeobiogeographical studies of the vertebrate faunas,sporomorph assemblages,and brachiopod faunas of the study area indicate a closer geographical relationship between the South China,Tarim,and Indochina palaeoplates,than previously considered.Compared with the surrounding areas where Silurian strata have been extensively studied,the study of Silurian strata in the main part of the Qinghai-Tibetan Plateau is still in the preliminary stage.In the future,it is necessary to conduct research on the age,distribution,and resource potential of basal Silurian black shales to provide new directions for shale gas exploration and development in China.The shallow marine strata of the middle to upper Silurian require further subdivision.Considering that the Silurian System in the Qinghai-Tibetan Plateau is more complete,it has the potential to supplement and improve the study of the carbon isotope stratigraphy of the Silurian in China.展开更多
The Ordovician rocks on the Qinghai-Tibetan Plateau represent the oldest non-metamorphic strata,and are critical to understanding the history of regional geology and biotic evolution of the entire plateau.Strata of Fl...The Ordovician rocks on the Qinghai-Tibetan Plateau represent the oldest non-metamorphic strata,and are critical to understanding the history of regional geology and biotic evolution of the entire plateau.Strata of Floian,Darriwilian,Sandbian,Katian and Hirnantian are represented in the plateau with a hiatus of variable duration occurring underneath the basal Ordovician across the area.Five stratigraphical regions,including the Himalaya,Gangdise-Zayu,Qiangtang-Qamdo,Songpan-Garze,and Karakoram-Kunlun-Altun,are differentiated for the Ordovician strata,which are correlated with their equivalents in the Sibumasu,Indochina,Qaidam-Qilian,Tarim-Tianshan,and the Yangtze(western margin)stratigraphical regions.On the QinghaiTibetan Plateau,graptolites,conodonts,and cephalopods are the most common and useful fossils for the Ordovician biostratigraphy.The Ordovician biotas of the Qinghai-Tibetan Plateau bear some distinguishable palaeobiogeographical signatures,among which the cephalopods are characterized by the flourishing actinocerids of North China affinity in the Early-Middle Ordovician,and by the thriving lituitids and orthocerids of South China affinity in the Middle-Late Ordovician.Fossil occurrences and their palaeobiogeographical evolution provide critical evidence bearing on the reconstruction of the geological history of the Qinghai-Tibetan Plateau and surrounding terranes in northeastern peri-Gondwana.The stratigraphical successions of the Cambrian-Ordovician transition in the Himalaya and Lhasa and nearby Sibumasu terranes were significantly affected by the Kurgiakh Orogeny,which resulted in the extensive unconformity between the Ordovician and the underlying rocks in most areas of the Qinghai-Tibetan Plateau.In southern Xizang,a warm-water biota of Middle Ordovician age was recovered from oolitic limestones,suggesting a likely palaeogeographical location in low-latitudes near the equator.In the Himalaya and Sibumasu regions,the Upper Ordovician was typified by the occurrence of red carbonates with distinctive reticulate structures,which are correlative to their equivalents in the Yangtze region of South China,and might be deposited under similar geological conditions.The global end-Ordovician glaciation and sea-level drop likely caused the wide absence of late Katian strata in western Yunnan of China and the Shan State of Myanma,and may have also affected deposition in the Xainza and Nyalam areas of the QinghaiTibetan Plateau during this time interval.展开更多
The Triassic rocks are widespread in China, and both marine and terrestrial strata are well developed. The Triassic stratigraphic architecture of China is very complex in both spatial variation of the so-called "...The Triassic rocks are widespread in China, and both marine and terrestrial strata are well developed. The Triassic stratigraphic architecture of China is very complex in both spatial variation of the so-called "South Marine and North Continental", i.e. the southern areas of China occupied mostly by marine facies while the northern China by terrestrial facies during the Triassic Period, and temporal transition of the "Lower Marine and Upper Continental", i.e. the lower part of the Triassic System composed mainly of marine facies and the upper part of terrestrial strata especially in South China. Although the Global Stratotype Section and Point(GSSP) of the Permian-Triassic boundary is located in South China, the Triassic of China except for some marine Lower-Middle Triassic depositions shows significantly local characteristics and is hardly correlated with the global chronostratigraphic chart. Consequently, the Triassic of China contains not only the international research hotspots but also difficult points in stratigraphic study. This paper aims to present a brief review of the Triassic in China, including chronostratigraphy, biostratigraphy, magnetostratigraphy and chemostratigraphy, and summarize an integrated Triassic stratigraphic framework of China. Accordingly, a stratigraphic correlation is proposed for the lithostratigraphic sequences among the three tectono-paleogeographic stratigraphic regions. The comprehensive study indicates that ammonoids are the classic index fossils in Triassic biostratigraphy but conodonts are more advantageous in the study and definition of the Triassic chronostratigraphic boundaries. China still has the potential to optimize the GSSPs of the Induan-Olenekian boundary and Olenekian-Anisian boundary. The correlation of the Permian-Triassic boundary between marine and terrestrial facies might be achieved with the help of the Permian-Triassic "transitional bed" and its related biotic and environmental events in association with the biostratigraphic study of conchostracan, vertebrate and plant fossils. In addition, the carbon isotopes have been proved to be one of the powerful methods in marine Triassic stratigraphic study, whereas the oxygen and strontium isotopes may be additional important bridges to establish the correlation between the marine and terrestrial strata, but as yet lacking of relevant studies in terrestrial strata. Considering the most stratigraphic intervals of the Triassic and the terrestrial Triassic in China are difficult to be correlated to the global chart, the proposed Chinese(regional) Triassic chronostratigraphic chart of marine and terrestrial stages would be of importance to the study of Chinese Triassic stratigraphy and related aspects, but the stages must be conceptually in line with international standards and studied as soon as possible in order to finalize the definition.展开更多
The strata of the Late Cretaceous and the Early Paleocene of the Shanyang Basin,ShaanxiProvince are basically continuous.The lithostratigraphic boundary between them is hard to determine.Thepaleomagnetic measurement s...The strata of the Late Cretaceous and the Early Paleocene of the Shanyang Basin,ShaanxiProvince are basically continuous.The lithostratigraphic boundary between them is hard to determine.Thepaleomagnetic measurement shows that the Upper Cretaceous Shanyang Formation in the basin was formedfrom 70 Ma to 65 Ms.Its polarity chron corresponds to 32,31R,31,30R,and 30.The Paleocene JuanlingFormation accumulated between 65 Ma and 61 Ma and corresponds to 29R,29,28R,28,27R,27.Theboundary between the Maastrichtian and the Paleocene is located in the lower part of 29R in the paleomagnet-ic time scale.Fossil dinosaurian eggs were found in a layer less than 20 m below the Paleocene and Creta-ceous magnetic boundary,and Paleocene mammalian fossils were found in a layer about 30 m above theboundary.The magnetostratigraphie and biostratigraphic boundaries between the Cretaceous and the Ter-tiary(K/T)are basically in conformity.展开更多
基金supported by the Govan Mbeki Research Centre(GMRC) at the University of Fort Hare and by the Council for Geoscience
文摘The Balfour Formation has a pronounced lithological variation that is characterized by alternating sandstone- and mudstone-dominated members. The sandstone-dominated Oudeberg and Barberskrans Members are composed of lithofacies that range from intraformationai conglomerates to fine-grained sediments, whereas the mudstone-dominated members (Daggaboersnek, Elandsberg, and Palingkloof) are dominated by the facies Fm and FI. Petrography, geochemistry, and a paleocurrent analysis indicated that the source rock of the Balfour Formation was to south east and the rocks had a transitional/dissected magmatic arc signature. The sandstones-rich members were deposited by seasonal and ephemeral high-energy, low-sinuous streams, and the fine-grained-rich members were formed by ephemeral meandering streams. The paleoclimates have been equated to present temperate climates; they were semiarid becoming arid towards the top of the Balfour Formation. This has been determined by reconstructing the paleolatitude of the Karoo Basin, geochemistry, paleontology, sedimentary structures, and other rock properties, like color.
文摘The Balfour Formation was subdivided into five members based on lithological variation that is characterized by alternating sandstone-and mudstone -dominated members.The sandstone dominated Oudeberg and Barberskrans members are composed of lithofacies that range from intraformational conglomerates to fine-grained sediments,whereas the mudstone dominated members(Daggaboersnek, Elandsberg and Palingkloof) are dominated by the fine-grained facies(Fm and F1).Petrography,geochemistry and palaeocurrent analysis indicated that the source rock of the Balfour Formation was to
文摘This study was carried out to investigate the impact of drainage basin’s lithostratigraphy on the quality and type of stored water in the Mujib dam reservoir. The water samples were collected on a monthly basis from surface water from January 2012 to December 2015. The classifications of collecting water samples for domestic and irrigation purposes were based on different physico- chemical parameters such as pH, EC, TDS, TSS, Na+, K+, Ca2+, Mg2+, Cl-, SO42-, HCO3- , NH4+, NO3- , NO2- , SAR, RSC, SSP, RSBC, PI, MAR, KR, and TH. All analyzed water samples were satisfied the Jordanian permissible limit and graded as “fresh water”. The hydrochemical indices (Mg/Ca and Cl/HCO3) and Cation Exchange values (CEV), indicating that the surface water chemistry is due to the rock weathering minerals with respect to their inland origin. The water samples have complied within the respective limits in respect of pH, EC, SAR, RSC, RSBC, MAR, KR, SSP and PI, and hard in respect of TH which may be due to the dissolution of the weathered rocks. Abundance of cations and anions is in the following order: Ca > Na > Mg > K and HCO3 > SO4 > Cl > NO3 during the period 2013-2015 and SO4 > HCO3 > Cl > NO3 through 2012. Thus, calcium and bicarbonate–sulfate are the dominant ions present in the surface water of this study. Piper diagram suggested that carbonate and gypsum weathering is the dominant process controlling reservoir water chemistry in the basin area. The quality and type of surface water can be modified by the lithology of the catchment area. The hydrogeochemical study of Mujib reservoir water indicated that the water quality is safe for drinking and agricultural purposes.
文摘The Khao Ya Puk Formation (>400 m thick) is well exposed in the Nakhon Thai Region, and is subdivided into three members. The Khao Ya Puk Formation overlies conformably on top of the anhydrite layer of the upper rock salt Maha Sarakham Formation. In turn, it is overlain unconformably by the Phu Khat Formation. The Khao Ya Puk Formation is interpreted to have been deposited by freshwater lake area in arid climate inland subkha in the Late Cretaceous. Lithostatigraphically, Khao Ya Puk Formation can be correlated with the Phu Tok Formation that has been deposited in the Khorat-Ubon basin and Udon-Sakon basin of the Khorat Plateau.
文摘The lithostratigraphy and biostratigraphy specifications of the Sarvak Formation are considered to study in wells No. 2, 16 and 66 of Rag-e-Safid oilfield. They are located at the southeast of Ahwaz (the southwest of Iran). The lithology of the Sarvak Formation in all the wells mostly consists of limestone. The depth of the Sarvak Formation in well No. 2 is 720 m;in this well, the Sarvak Formation overlies the Kazhdumi Formation and underlies the Papdeh Formation. Vertical distribution of recognized foraminifera, macrofossils and calcareous Algae identifies two biozones: 1) Favusellawashitensis Range zone;2) Praealveolinacretacea-Ovalveolina ovum & Rudistfragment Ass. zone. The thicknesses of the Sarvak Formation in wells No. 16 and 66 are about 100 m and 108 m, respectively;in a part of the Sarvak Formation, drilling was completed, while its upper boundary is covered with the Papdeh Formation, in both wells. In terms of biostratigraphy studies in wells No. 16 and 66, one assemblage biozone is recognized as Praealveolinacretacea-Ovalveolina ovum & Rudistfragment Ass. Zone, similarly. Finally, the age of the Sarvak Formation is determined as the Cenomanian in three considered wells.
文摘Non-marine Cretaceous rocks are widespread in northeastern Thailand and is well known as “the red bed” Khorat Group. The Sao Khua Formation is in the upper half of the Khorat Group which is comprised of six formations. This formation was named and defined at the type section for the rocks between the restricted PhraWihan Formation and the Phu Phan Formation in the drainage area of the Huai Sao Khua, an intermittent stream that flows westward parallel to the highway between Nong Bua Lamphu and UdonThani Provinces. It contains richest and most diverse vertebrate and invertebrate Mesozoic fossils in Thailand. The Sao Khua Formation is characterized by the sequence of the fining-upward successions of at least 4-5 megacycles throughout the formation with the total thickness ranging between 400-700 meters. Each cycle starts with a channel lag conglomerate which the clasts consist totally of re-worked calcrete nodules. The conglomerates were overlain by fine-to medium-grained sandstones of point bar deposit. Finally, the top part of each cycle was covered by a succession of fine-grained floodplain deposit that makes up 60%-70% of the formation. Paleosols are commonly found in the Sao Khua Formation within the floodplain sequence and their geochemistry indicates a semi-arid paleoclimate. Based on lithostratigraphy, the Sao Khua Formation is interpreted to have been deposited by a meandering river system under a semi-arid climate condition. The age of the formation is assigned as the Hauterivian-Late Barremian based on vertebrate and bivalves fossils.
文摘The Mamfe Basin has been the subject of many studies,but some debates persist,especially concerning the stratigraphic nomenclature,corundum origin,and marine transgression.The aims of this work are(1)to propose a new lithostratigraphic nomenclature of the Mamfe Basin formation based on new field observations,(2)to determine the source rock distribution and the origin of gem deposits and(3)to correlate the Cameroon section of the Mamfe Basin with the Nigerian deposits.The main results show that the name Manyu River Group is more appropriate as the Manyu River crosses all the facies in the Mamfe sedimentary Basin belonging to the Manyu Division.According to the facies analysis,the age of deposition,the mineralogic and geochemical data such as the V vs.Al2O3andΣREE vs.Al_(2)O_(3),TiO_(2)MgO,Na_(2)O,P_(2)O_(5),and CaO diagrams,this Group is composed of at least five Formations,including four Cretaceous Formations,from bottom to top:the Etoko Formation(alluvial and fluvial channel to fluvio-lacustrine deposits),the Nfaitok Formation(lagoonal deposits),the Bachuo Ntai Formation(fluvial braided channels or fluvio-deltaic environment)and the Eyumojock/NsanaragatiFormation(fluvio-lacustrine deposits)and the new Cenozoic Formation named Bakebe Formation(fluvio-lacustrine deposits).The gem minerals such as corundum,rutile,or tourmaline in the Cretaceous deposits of the Mamfe Basin are mainly detrital as indicated by the presence of worn shapes and fragments of these minerals.The presence of sapphire in the AlboCenomanian deposits indicates a Precambrian age of the felsic source rock,likely the plutonic rocks such as granite or pegmatite as indicated by the abundance of tourmaline and high LREE/HREE ratios(14.81–34.29)and slightly negative and positive Eu anomalies(0.85–1.15).This marine incursion in the Mamfe Basin was probably from West Nigeria,according to the geographic location of the Mamfe Basin and the general palaeogeographic evolution of the Benue Trough.
基金funded by the National 973-Program(Project Nos.2012CB416602,2006CB403508)National Natural Science Foundation of China(Nos.40352003,40425006,40373007)Frontier Field Project of the State Key Laboratory of Ore Deposit Geochemistry,Institute of Geochemistry,Chinese Academy of Sciences
文摘This paper compiles lithostratigraphic and geochronological data obtained for the Palaeoproterozoic glacial diamictite-bearing successions,and thereby provides insights into understanding the geological processes causing the Huronian Glaciation Event.The majority of evidence for appearances of this glaciation event can be related to the Kenorland supercontinent breakup,allied to significant atmospheric change,as well as blooms of biogeochemical oxygenic photosynthesis.In this paper,the Huronian Glaciation Event is constrained to have occurred synchronously during 2.29-2.25 Ga,accompanied by dramatic environmental changes characteristic of the Great Oxidation Event which includes the pre- 2.3 Ga hydrosphere oxidation and the post-2.3 Ga atmosphere oxygenation.
文摘The growth strata was investigated in the Early Cretaceous deposits including Fahliyan, Gadvan and Dariyan formations in the Well 3 that is located between Qatar-Fars height and Hormuz Strait in Persian Gulf. This study is based on the lithostratigraphic analysis and microfossils distribution. Lithostratigraphically, the Well 3 is divided into three rock units including Fahliyan, Gadvan and Dariyan. Based on the microfossils content, the age of studied successions is Berriasian to Aptian. The comparison of seismic studies, lithostratigraphic analysis and microfossils distribution show that growth and generation of anticlines construct in the Early Cretaceous. As a result, the Fahliyan, Gadvan and Dariyan rock units have potential reservoir and oil trap.
文摘The Albertine Graben is one of the most petroliferous onshore rifts in Africa. It forms the northemmost termination of the western arm of the East African Rift System. Its surface exposures were first studied by Wayland [1] and Pickford et al. [2] among others. Pickford et al. [2] especially developed the basic stratigraphic framework of the graben which was later modified by the government geoscientists and international oil companies using subsurface data. However, the stratigraphic units were not fully and formally described, and have been used informally in different and often confusing ways. The current study therefore aims to solve this challenge by establishing a coherent stratigraphic scheme for the entire graben through an integral study of surface and subsurface data. The study involves precise description of the type and reference sections for various formations both in exposure and wells; and has therefore led to the development of lithostratigraphic columns of different basins in the graben. The approach reveals that the Semliki area, south of Lake Albert, has the most complete sedimentary succession in the graben, spanning the period from middle Miocene (ca 15 Ma) to Recent. It also reveals that platform deposits, which form a small fraction of the thickness of the basinal succession, represent a highly condensed sequence which only saw deposition at times of Lake highstand.
文摘This paper concerns deals with the Mongolian regional stratigraphic classification of sedimentary, sedimentary-volcanogenic sediments, and metamorphic complex spread over the territory of Mongolia according to the new International Chronostratigraphic Chart [1]. The regional stratigraphy of Precambrian-Cenozoic rocks of the Mongolian territory was studied by Dorjnamjaa et al. [2]. So, this paper provides for the stratigraphy and correlation of key sections through the Archean-Proterozoic-Mesozoic-Cenozoic of various areas of Mongolia. In this paper, the author introduces the most important results indicating the key reference sections for the first time and put into a broad regional context. The characterization and geologic mapping of lithological units provided an essential basis for the lithostratigraphy, biostratigraphy and chemostratigraphy. Especially key biostratigraphic aspects are the phenomenon of faunal succession. The basic lithostratigraphic unit is the formations and groups which have been successful mapped. At present in Mongolia for Precambrian period (systems and series) 30 formations and groups, for Paleozoic—about 250 formations and groups, for Mesozoic—102 formations and groups, for Cenozoic—27 formations, members, and beds are distinguished. The auxiliary stratigraphic units are members, beds which should be mapped depending on great extent of detailed study. In the regional stratigraphical classification, there are two primary kinds of stratotypes [3]: a) unit stratotypes, which serve as the standard of definition for a stratigraphic unit, and b) boundary stratotypes, which serve as the standard of definition for a stratigraphic boundary. These aspects, in particular gradational boundaryas far as possible were examined for example for Archean-Paleoproterozoic (by geochronologic data), Ediacaran-Early Cambrian (by soft-bodied fossils, trace fossils and small shelly fossils), Ordovician-Silurian (by beyrichiidostracodes), Devonian-Carboniferous (by conodonds), Paleocene-Eocene (by mammals), Oligocene-Miocene (by small rodents) systems and series.
文摘Fahliyan Formation is importance in terms of Zagros stratigraphy since it is one of the oil reservoir rocks at the Jurassic-Cretaceous boundary. This rock unit consists of two types of deep and shallow facies in Zagros area. Recognition of bio-zones as well as discontinuity or continuity between the studied formation and the encompassed stratais taken into consideration. In order to study biostratigraphy on Fahliyan Formation, the stratigraphic section of Kuh-e-siah in the north-east of Fars Province was selected. In this section, Fahliyan Formation is measured 345 m consisting of thin to medium-bedded of limestone with the interbeds of sandy and dolomitic limestones. Fahliyan Formation conformably overlies Surmeh formation and underlies the marls of Gadvan formation. Vertical distribution of the identified foraminifers and calcareous algae confirms presence of 3 biozones in the sediments of Fahliyan Formation, as follows: 1) Calpionella alpina zone;2) Pseudochrysalidina conica zone;3) Pseudocyclammina lituus-Trocholina sp. assemblage zone. Based on Established biozones, the age of Fahliyan Formation in Kuh-e-Siah section was determined from Berriasian to Late Hauterivian.
基金supported by the Second Tibetan Plateau Scientific Expedition and Research Program(Grant No.2019QZKK0706)the National Natural Science Foundation of China(Grant Nos.91955201,42172002)。
文摘During the Carboniferous Period,the Qinghai-Tibetan Plateau and its surrounding areas were located in quite different paleogeographic positions with various sedimentary and biological types.It is important to systematically compile and summarize the Carboniferous strata and biotas of the Qinghai-Tibetan Plateau and its surrounding areas,to establish an integrated stratigraphic framework for correlation,and to reconstruct the paleogeography for correctly understanding the breakup of the Gondwana Continent and the evolution of the Paleo-Tethys Ocean in the Late Paleozoic.The Carboniferous of the Qinghai-Tibetan Plateau and its surrounding areas can be subdivided into the Gondwanan,Cimmerian,and Tethyan types.The Gondwanan-type Carboniferous are distributed in the North Himalayan,Kangmar-Lhunze,and Zanda-Zumba regions of the South Tibet Subprovince and northern India-Pakistan Area,where only the Mississippian is developed and the biota is of Gondwanan affinity.The Cimmerian-type Carboniferous,which are found in the Baoshan,Tengchong,Coqen-Xainza,LhasaZayu,Nagqu-Biru,and South Qiangtang regions,as well as Shan-Thai and South Afghanistan-Pamir areas,also represent only the Mississippian strata,but their biota is characterized by mixed characters of European,South China,Australian,and North American types.The Tethyan-type Carboniferous are distributed in the Tanggula Mountains,Hoh Xil-Bayanhar,ChamdoHengduanshan,Tiekelike,West Kunlun,Karakorum,East Kunlun-Central Qinling,and Qilian regions,where the Carboniferous succession is well developed,and the biota is of warm-water Tethyan affinity.The biostratigraphical correlation of the Gondwanan-type and Cimmerian-type Carboniferous is based mainly on conodonts and additionally on brachiopods and rugose corals.The Mississippian of the Tethyan-type Carboniferous is correlated mainly by using rugose corals and brachiopods,whereas in the Pennsylvanian foraminifera(fusuline)and conodonts are regarded as primary fossil groups,subordinated by rugose corals and brachiopods.Adhering to the International standard chronostratigraphy of the Carboniferous,we have reconstructed a framework of the litho-and biostratigraphic subdivision and correlation of the Qinghai-Tibetan Plateau and its surrounding areas.Further studies should focus on isotope geochronology,geochemistry,paleoclimates,and paleoenvironments of the Carboniferous in the Qinghai-Tibetan Plateau and its surrounding areas.
基金supported by the National Natural Science Foundation of China(Grant Nos.42372043,41972034,42072043)。
文摘Rocks of the Qinghai-Tibetan Plateau(QTP)host abundant Triassic fossils.So far,the well established marine fossil sequences based on ammonoids,conodonts,bivalves,brachiopods,radiolarians,and terrestrial spora-pollen sequence have become standard for biostratigraphic correlation of the QTP.For much of Triassic time,the QTP occupied a marine setting as suggested by the dominance of marine deposits.The main sedimentary types represented in the Triassic successions include littoral to shallow marine clastic rocks,shallow marine carbonate platform carbonates,bathyal to abyssal slope carbonates intercalated with clastic and siliceous deposits,coal-bearing clastic strata contained within paralic facies deposits,and littoral and terrestrial volcaniclastic rocks.These deposits are organized into four stages in ascending order:(1)Early Triassic deposits that record marine transgression,including extensive shallow marine carbonate platform strata.(2)Middle Triassic Ladinian to Late Triassic Carnian deposits,including thin-bedded limestone,fine clastics,and siliceous rocks,that accumulated at greater depths than underlying Early Triassic strata and reflect the peak of the transgression.Magmatic activity appears to have occurred in some areas during this stage.(3)Late Triassic Norian deposits that record the onset of marine regression as suggested by the widespread occurrence of platform carbonates.It is noteworthy that stage 3 deposits of the Qin-Qi-Kun area in the northernmost region of the QPT is dominated by terrestrial strata and displays evidence of local erosion.(4)Late Triassic Rhaetian littoral and shallow marine clastic and coal-bearing deposits that preserve the record of continued marine regression continued.The Indus-Yarlungzangbo Suture Zone(IYSZ)appears to have been the rifting axis during Triassic time as suggested by sedimentary facies trends that reflect deepening to south and north.Thus,the Himalaya Block to the south of the IYSZ was part of the passive margin of Gondwana whereas the north side of the IYSZ,including the Gangdis(or Lhasa)and South Qiangtang blocks,belonged to the passive margin of Eurasia.The similarity of rocks of the Bangongco-Nujiang Suture Zone(BNSZ)to the north of the IYSZ with those of the Gangdis Block to the south and the South Qiangtang Block to the north does not support the contention that the BNSZ was a rift axis during Triassic time.Results of palaeobiological research also suggest that the IYSZ rather than BNSZ was a biogeographic boundary during the Triassic.Early and Middle Triassic break-up of Pangea was accompanied on the QTP by rifting along the IYSZ.The expression of crustal shortening induced by the Indosinian Orogeny on the QTP is largely a change of sedimentary facies induced by Late Triassic uplift.Deposits of the Gangdis to South Qiangtang regions of the QTP record a transition from shallow marine carbonate platform deposits to littoral and paralic coal-bearing strata.Moreover,the stratigraphic succession of the Qin-Qi-Kun area preserves a transition from littoral clastic deposits to terrestrial facies and local erosion.
基金supported by the Second Tibetan Plateau Scientific Expedition and Research(Grant No.2019QZKK0706)the National Natural Science Foundation of China(Grant Nos.41972162,42102013,42272007,and 42302029)the Natural Science Foundation of Jiangsu Province(Grant No.BK20210992)。
文摘The Silurian palaeontology and stratigraphy of the Qinghai-Tibetan Plateau have been studied for more than100 years.With the launch of the Second Tibetan Plateau Scientific Expedition and Research,it is necessary to update the summaries of the Silurian stratigraphy and fossil assemblages of the Qinghai-Tibetan Plateau and their correlation with its surrounding areas.In this study,we have selected 33 sections from the Qinghai-Tibetan Plateau and its surroundings areas,summarised the available data in terms of stratigraphic regionalisation,lithostratigraphy,chronostratigraphy,and biostratigraphy,and divided the study area into four stratigraphic provinces:the Xizang-Western Yunnan-Western Sichuan Province,the KunlunQilian Province,the South China Province,and the Tarim Province.In general,the Silurian strata in the Qinghai-Tibetan Plateau is more complete than those in other areas of China.Palaeobiogeographical studies of the vertebrate faunas,sporomorph assemblages,and brachiopod faunas of the study area indicate a closer geographical relationship between the South China,Tarim,and Indochina palaeoplates,than previously considered.Compared with the surrounding areas where Silurian strata have been extensively studied,the study of Silurian strata in the main part of the Qinghai-Tibetan Plateau is still in the preliminary stage.In the future,it is necessary to conduct research on the age,distribution,and resource potential of basal Silurian black shales to provide new directions for shale gas exploration and development in China.The shallow marine strata of the middle to upper Silurian require further subdivision.Considering that the Silurian System in the Qinghai-Tibetan Plateau is more complete,it has the potential to supplement and improve the study of the carbon isotope stratigraphy of the Silurian in China.
基金supported by the Second Tibetan Plateau Scientific Expedition and Research(Grant No.2019QZKK0706)the National Natural Science Foundation of China(Grant Nos.42030510,42002009,42102013)+2 种基金the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB26000000)the State Key Laboratory of Palaeobiology and Stratigraphy(Grant Nos.20201104,20221103)the Chinese Academy of Geological Sciences(Grant No.DD20221829)。
文摘The Ordovician rocks on the Qinghai-Tibetan Plateau represent the oldest non-metamorphic strata,and are critical to understanding the history of regional geology and biotic evolution of the entire plateau.Strata of Floian,Darriwilian,Sandbian,Katian and Hirnantian are represented in the plateau with a hiatus of variable duration occurring underneath the basal Ordovician across the area.Five stratigraphical regions,including the Himalaya,Gangdise-Zayu,Qiangtang-Qamdo,Songpan-Garze,and Karakoram-Kunlun-Altun,are differentiated for the Ordovician strata,which are correlated with their equivalents in the Sibumasu,Indochina,Qaidam-Qilian,Tarim-Tianshan,and the Yangtze(western margin)stratigraphical regions.On the QinghaiTibetan Plateau,graptolites,conodonts,and cephalopods are the most common and useful fossils for the Ordovician biostratigraphy.The Ordovician biotas of the Qinghai-Tibetan Plateau bear some distinguishable palaeobiogeographical signatures,among which the cephalopods are characterized by the flourishing actinocerids of North China affinity in the Early-Middle Ordovician,and by the thriving lituitids and orthocerids of South China affinity in the Middle-Late Ordovician.Fossil occurrences and their palaeobiogeographical evolution provide critical evidence bearing on the reconstruction of the geological history of the Qinghai-Tibetan Plateau and surrounding terranes in northeastern peri-Gondwana.The stratigraphical successions of the Cambrian-Ordovician transition in the Himalaya and Lhasa and nearby Sibumasu terranes were significantly affected by the Kurgiakh Orogeny,which resulted in the extensive unconformity between the Ordovician and the underlying rocks in most areas of the Qinghai-Tibetan Plateau.In southern Xizang,a warm-water biota of Middle Ordovician age was recovered from oolitic limestones,suggesting a likely palaeogeographical location in low-latitudes near the equator.In the Himalaya and Sibumasu regions,the Upper Ordovician was typified by the occurrence of red carbonates with distinctive reticulate structures,which are correlative to their equivalents in the Yangtze region of South China,and might be deposited under similar geological conditions.The global end-Ordovician glaciation and sea-level drop likely caused the wide absence of late Katian strata in western Yunnan of China and the Shan State of Myanma,and may have also affected deposition in the Xainza and Nyalam areas of the QinghaiTibetan Plateau during this time interval.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41530104 & 41661134047)
文摘The Triassic rocks are widespread in China, and both marine and terrestrial strata are well developed. The Triassic stratigraphic architecture of China is very complex in both spatial variation of the so-called "South Marine and North Continental", i.e. the southern areas of China occupied mostly by marine facies while the northern China by terrestrial facies during the Triassic Period, and temporal transition of the "Lower Marine and Upper Continental", i.e. the lower part of the Triassic System composed mainly of marine facies and the upper part of terrestrial strata especially in South China. Although the Global Stratotype Section and Point(GSSP) of the Permian-Triassic boundary is located in South China, the Triassic of China except for some marine Lower-Middle Triassic depositions shows significantly local characteristics and is hardly correlated with the global chronostratigraphic chart. Consequently, the Triassic of China contains not only the international research hotspots but also difficult points in stratigraphic study. This paper aims to present a brief review of the Triassic in China, including chronostratigraphy, biostratigraphy, magnetostratigraphy and chemostratigraphy, and summarize an integrated Triassic stratigraphic framework of China. Accordingly, a stratigraphic correlation is proposed for the lithostratigraphic sequences among the three tectono-paleogeographic stratigraphic regions. The comprehensive study indicates that ammonoids are the classic index fossils in Triassic biostratigraphy but conodonts are more advantageous in the study and definition of the Triassic chronostratigraphic boundaries. China still has the potential to optimize the GSSPs of the Induan-Olenekian boundary and Olenekian-Anisian boundary. The correlation of the Permian-Triassic boundary between marine and terrestrial facies might be achieved with the help of the Permian-Triassic "transitional bed" and its related biotic and environmental events in association with the biostratigraphic study of conchostracan, vertebrate and plant fossils. In addition, the carbon isotopes have been proved to be one of the powerful methods in marine Triassic stratigraphic study, whereas the oxygen and strontium isotopes may be additional important bridges to establish the correlation between the marine and terrestrial strata, but as yet lacking of relevant studies in terrestrial strata. Considering the most stratigraphic intervals of the Triassic and the terrestrial Triassic in China are difficult to be correlated to the global chart, the proposed Chinese(regional) Triassic chronostratigraphic chart of marine and terrestrial stages would be of importance to the study of Chinese Triassic stratigraphy and related aspects, but the stages must be conceptually in line with international standards and studied as soon as possible in order to finalize the definition.
基金the National Natural Science Foundation of China.
文摘The strata of the Late Cretaceous and the Early Paleocene of the Shanyang Basin,ShaanxiProvince are basically continuous.The lithostratigraphic boundary between them is hard to determine.Thepaleomagnetic measurement shows that the Upper Cretaceous Shanyang Formation in the basin was formedfrom 70 Ma to 65 Ms.Its polarity chron corresponds to 32,31R,31,30R,and 30.The Paleocene JuanlingFormation accumulated between 65 Ma and 61 Ma and corresponds to 29R,29,28R,28,27R,27.Theboundary between the Maastrichtian and the Paleocene is located in the lower part of 29R in the paleomagnet-ic time scale.Fossil dinosaurian eggs were found in a layer less than 20 m below the Paleocene and Creta-ceous magnetic boundary,and Paleocene mammalian fossils were found in a layer about 30 m above theboundary.The magnetostratigraphie and biostratigraphic boundaries between the Cretaceous and the Ter-tiary(K/T)are basically in conformity.