Mesozoic neo-tethyan pre-orogenic deep marine sediments along the Indus–Yarlung Suture,Himalaya

Shelf, forereef and basin margin (slope) olistoliths (Exotic blocks of limestone) of Permian–Jurassic age are tectonically juxtaposed within the Triassic to Eocene age pre-orogenic, deep abyssal plain turbidites of the Lamayuru. The pre-collision tectonic setting and depositional environment of the limestone olistoliths can be reconstructed from within the neighbouring Zanskar range. The disorganized Ophiolitic Melange Zone, an association of different tectonic rock slivers of Jurassic–Eocene age, is tectonically underlain by the overthrusted Lamayuru Formation and tectonically overlain by the Nindam Formation. Tectonic slivers of Late Jurassic–Early Cretaceous age red radiolarian cherts represent a characteristic lithotectonic unit of the Ophiolitic Melange Zone, those occurring near the contact zone with the Lamayuru Formation, were deposited within the neo-Tethyan deep-ocean floor of the Indian passive margin below the carbonate compensation depth. These tectonic slivers accumulated along the northern margin of the Indus–Yarlung Suture Zone of the Ladakh Indian Himalaya during subduction accretion associated with the initial convergence of the Indian plate beneath the Eurasian plate.     

Mesozoic marine reptiles from Spitsbergen and their ecosystems

In the Mesozoic seas, the apex predators were reptiles. From the Arctic archipelago of Svalbard, the Spitsbergen Mesozoic Research Group has excavated numerous well preserved marine reptile skeletons in order to understand the biology of these animals and the environment they lived in. The work of eleven field seasons has made this one of the largest and most productive palaeontological research projects in the high Arctic world‐wide. The initial eight seasons focused on one of the richest occurrences of Late Jurassic—earliest Cretaceous (c. 150–139 Ma) marine reptiles in the world, and nearly sixty specimens have been collected, together with a diverse assemblage of invertebrates, some of which are associated with methane seeps. The last three seasons were spent investigating events further back in time, as Spitsbergen preserves the remains from some of the first marine reptile radiations in the wake of the most devastating extinction in the history of the Earth, at the Permian–Triassic boundary (c. 252 Ma).     

Palynological assemblages of non-marine rocks at the Permian–Triassic boundary, western Guizhou and eastern Yunnan, South China

Marine and non-marine facies of the Permian–Triassic boundary stratigraphic set (PTBST) are well developed in South China. Palynological assemblages enable subdivision and correlation of the Permian–Triassic boundary (PTB) rocks. Three palynological assemblages are recognized across the PTBST in two terrestrial PTB sections in western Guizhou and eastern Yunnan, South China. Assemblage 1 (Xuanwei Formation) is a Late Permian palynological assemblage dominated by ferns and pteridosperms, with minor gymnosperms. Most taxa are typical long-ranging Paleozoic forms, but the appearance of Lueckisporites confirms a Late Permian age for this assemblage. Assemblage 2 (PTBST) is marked by an abrupt decrease in palynomorph abundance and diversity, and thriving fungal/algal(?) spores. Assemblage 2 is still dominated by ferns and pteridosperms, with a few gymnosperms, but is characterized by a mixed palynoflora containing both Late Permian and Early Triassic elements. Most taxa are typical Late Permian ones also found in Assemblage 1, however, some taxa of Early Triassic aspect, e.g. Lundbladispora and Taeniaesporites, appeared for the first time. In Assemblage 3 (top Xuanwei Formation and Kayitou Formation), the proportion of gymnosperm pollen increases rapidly, exceeding that of ferns and pteridosperms, but the abundance of palynomorphs is still low. Typical Early Triassic taxa (such as Lundbladispora, Aratrisporites and Taeniaesporites) are present in greater abundance and confirms an Early Triassic age for this assemblage.     

Stratigraphy, biostratigraphy and C-isotopes of the Permian–Triassic non-marine sequence at Dalongkou and Lucaogou, Xinjiang Province, China

Measured lithostratigraphic sections of the classic Permian–Triassic non-marine transitional sequences covering the upper Quanzijie, Wutonggou, Guodikeng and lower Jiucaiyuan Formations at Dalongkou and Lucaogou, Xinjiang Province, China are presented. These measured sections form the framework and reference sections for a range of multi-disciplinary studies of the P–T transition in this large ancient lake basin, including palynostratigraphy, vertebrate biostratigraphy, chemostratigraphy and magnetostratigraphy. The 121 m thick Wutonggou Formation at Dalongkou includes 12 sandstone units ranging in thickness from 0.5 to 10.5 m that represent cyclical coarse terrigenous input to the lake basin during the Late Permian. The rhythmically-bedded, mudstone-dominated Guodikeng Formation is 197 m and 209 m thick on the north and south limbs of the Dalongkou anticline, respectively, and 129 m thick at Lucaogou. Based on limited palynological data, the Permian–Triassic boundary was previously placed approximately 50 m below the top of this formation at Dalongkou. This boundary does not coincide with any mappable lithologic unit, such as the basal sandstones of the overlying Jiucaiyuan Formation, assigned to the Early Triassic. The presence of multiple organic δ¹³C-isotope excursions, mutant pollen, and multiple algal and conchostracan blooms in this formation, together with Late Permian palynomorphs, suggests that the Guodikeng Formation records multiple climatic perturbation signals representing environmental stress during the late Permian mass extinction interval. The overlap between the vertebrates Dicynodon and Lystrosaurus in the upper part of this formation, and the occurrence of late Permian spores and the latest Permian to earliest Triassic megaspore Otynisporites eotriassicus is consistent with a latest Permian age for at least part of the Guodikeng Formation. Palynostratigrahic placement of the Permian–Triassic boundary in the Junggar Basin remains problematic because key miospore taxa, such as Aratrisporites spp. are not present. Palynomorphs from the Guodikeng are assigned to two assemblages; the youngest, from the upper 100 m of the formation (and the overlying Jiucaiyuan Formation), contains both typical Permian elements and distinctive taxa that elsewhere are known from the Early Triassic of Canada, Greenland, Norway, and Russia. The latter include spores assigned to Pechorosporites disertus, Lundbladispora foveota, Naumovaspora striata, Decussatisporites mulstrigatus and Leptolepidites jonkerii. While the presence of Devonian and Carboniferous spores and Early Permian pollen demonstrate reworking is occurring in the Guodikeng assemblages, the sometimes common occurrence of Scutasporites sp. cf. Scutasporites unicus, and other pollen, suggests that the Late Permian elements are in place, and that the upper assemblage derives from a genuine transitional flora of Early Triassic aspect. In the Junggar Basin, biostratigraphic data and magnetostratigraphic data indicate that the Permian–Triassic boundary (GSSP Level) is in the middle to upper Guodikeng Formation and perhaps as high as the formational contact with the overlying Jiucaiyuan Formation.     

Discovery of Gondwana plant fossils and palynomorphs of Late Asselian (Early Permian) age in the Karakoram Block

We report the discovery of Early Permian (late Asselian, ∼280–275 Ma) plant fossils and associated palynomorphs from a marine sedimentary sequence of the eastern Karakoram plate, in northern India. These specimens show affinities with those found in marine Lower Gondwana sediments of the Indian subcontinent. This supports the contention that during the Early Permian Period, the Karakoram plate was Peri-Gondwanan. It is suggested to have had an intermediate position between the Indian plate and the Qiangtang–Lhasa microcontinents, at a latitude of about 35° south.     

Permian megaspores from Kuraloi Area,Ib-River coalfield,Mahanadi Basin,Orissa

Heterogenous megaspores recovered from the Upper Permian sediments of Kuraloi Area, Ib-River coalfield, have been systematically described. The megaspore assemblage includes seven genera with seventeen species viz. Bokarosporites rotundus, Banksisporites indicus, B. utkalensis, Biharisporites spinosus, Biharisporites sp.A, Biharisporites sp.B, Jhariatriletes baculosus, J. srivastavae, J. damudicus, Manumisporites distinctus, Singhisporites baculatus, S. radialis, S. surangei, Ramispinatispora indica, R. nautiyalii and Ramispinatispora sp. Additionally, a new species of Ramispinatispora viz. R.mahanadiensis has been identified. Associated spore pollen assemblages are suggestive of a Late Permian age corresponding to Raniganj/Kamthi Formation. Raniganj megaspores are known from Damodar and Godavari Basins. The newly recorded megaspore assemblage from the Ib-River coalfield is comparable to that of Raniganj/Kamthi Formation of Godavari Graben. The diversity in exosporium ornamentations indicates structural diversity. Moreover, their prolific presence ultimately points towards occurrence of heterosporous source vegetation in the area.     

A Preliminary Study on Exhalative Mineralization in Permian Basins, the Southern Segment of the Da Hinggan Mountains, China – Case Studies of the Huanggang and Dajing Deposits–

Abstract: The southern segment of the Da Hinggan Mountains is a well‐known tin–polymetallic metallogenic belt of North China with Jurassic‐Cretaceous volcanic–plutonic rocks widespread. Principally because of this, most of the deposits are regarded as epigenetic hydrothermal deposits in genetic connection with the Mesozoic magmatism. But nearly 90 % of the deposits occur in Permian strata, and show concordant stratiform mineralization with a spatial distribution constrained by sedimentary facies of the Permian strata. A close association between mineralization and Permian strata is recognizable. The Huanggang Fe‐Sn deposit was regarded as a standard skarn‐type deposit formed by magmatic hydrothermal solutions in connection with Mesozoic granites. But there are abundant fabrics indicating submarine hydrothermal exhalation both in magnetite ores and in skarns, including bedding/lamination, soft–deformation, synsedimentary brecciation, and collo‐form fabrics. The magnetite orebodies and skarn‐bodies are predominantly concordant stratiform, and extend nearly 20 km along certain stratigraphic horizon, that is, the upper section of the Lower‐Permian submarine volcanic rocks. The Mesozoic granitic rocks crosscut the magnetite and skarn zone. Instead of skarnization, they show strong greisenization associated with cassiterite‐quartz veins, distinct from the magnetite skarn‐ore with disseminated tin in the Permian rocks. The Dajing Sn‐polymetallic deposit is generally regarded as subvolcanic‐hydrothermal origin, principally because of the close spatial association between ores and some of the Mesozoic subvolcanic dikes (called rhyolitic porphyry). Detailed geological, fabric, petrographical and mineralogical study demonstrates that this very kind of subvolcanic rocks is actually a new type of exhalites (called ‘siderite‐sericite chert’ according to its mineral assemblage), formed by hydrothermal sedimentation during the evolution of the Later‐Permian lacustrine basin. There are, however, indeed some rhyolitic porphyry dikes that crosscut orebod–ies. The orebodies and their associated exhalite predate, and thus have no genetic relation, to the Mesozoic magmatic process. We thus conclude that subaqueous exhalative mineralization did occur during the basin evolution at the Permian time in the southern segment of the Da Hinggan Mountains, which is ignored and poorly understood, but might be as important as the hydrothermal mineralization connected with the Mesozoic magmatism.     

Stratigraphy,biostratigraphy and C-isotopes of the Permian–Triassic non-marine sequence at Dalongkou and Lucaogou,Xinjiang Province,China

Measured lithostratigraphic sections of the classic Permian–Triassic non-marine transitional sequences covering the upper Quanzijie, Wutonggou, Guodikeng and lower Jiucaiyuan Formations at Dalongkou and Lucaogou, Xinjiang Province, China are presented. These measured sections form the framework and reference sections for a range of multi-disciplinary studies of the P–T transition in this large ancient lake basin, including palynostratigraphy, vertebrate biostratigraphy, chemostratigraphy and magnetostratigraphy. The 121 m thick Wutonggou Formation at Dalongkou includes 12 sandstone units ranging in thickness from 0.5 to 10.5 m that represent cyclical coarse terrigenous input to the lake basin during the Late Permian. The rhythmically-bedded, mudstone-dominated Guodikeng Formation is 197 m and 209 m thick on the north and south limbs of the Dalongkou anticline, respectively, and 129 m thick at Lucaogou. Based on limited palynological data, the Permian–Triassic boundary was previously placed approximately 50 m below the top of this formation at Dalongkou. This boundary does not coincide with any mappable lithologic unit, such as the basal sandstones of the overlying Jiucaiyuan Formation, assigned to the Early Triassic. The presence of multiple organic δ¹³C-isotope excursions, mutant pollen, and multiple algal and conchostracan blooms in this formation, together with Late Permian palynomorphs, suggests that the Guodikeng Formation records multiple climatic perturbation signals representing environmental stress during the late Permian mass extinction interval. The overlap between the vertebrates Dicynodon and Lystrosaurus in the upper part of this formation, and the occurrence of late Permian spores and the latest Permian to earliest Triassic megaspore Otynisporites eotriassicus is consistent with a latest Permian age for at least part of the Guodikeng Formation. Palynostratigrahic placement of the Permian–Triassic boundary in the Junggar Basin remains problematic because key miospore taxa, such as Aratrisporites spp. are not present. Palynomorphs from the Guodikeng are assigned to two assemblages; the youngest, from the upper 100 m of the formation (and the overlying Jiucaiyuan Formation), contains both typical Permian elements and distinctive taxa that elsewhere are known from the Early Triassic of Canada, Greenland, Norway, and Russia. The latter include spores assigned to Pechorosporites disertus, Lundbladispora foveota, Naumovaspora striata, Decussatisporites mulstrigatus and Leptolepidites jonkerii. While the presence of Devonian and Carboniferous spores and Early Permian pollen demonstrate reworking is occurring in the Guodikeng assemblages, the sometimes common occurrence of Scutasporites sp. cf. Scutasporites unicus, and other pollen, suggests that the Late Permian elements are in place, and that the upper assemblage derives from a genuine transitional flora of Early Triassic aspect. In the Junggar Basin, biostratigraphic data and magnetostratigraphic data indicate that the Permian–Triassic boundary (GSSP Level) is in the middle to upper Guodikeng Formation and perhaps as high as the formational contact with the overlying Jiucaiyuan Formation.     

New Evidence for a Cretaceous Age for a Mesozoic Nonmarine Bivalve Assemblage from Paekto-dong, Sinuiju City, The Democratic People’s Republic of Korea

The Sinuiju Formation in Paekto-dong, Sinuiju City in the Democratic People's Republic of Korea has yielded Mesozoic nonmarine bivalve fossils, which is the first occurrence of such in the DPRK. Based on these fossil specimens, a new Cretaceous bivalve assemblage, the Arguniella yanshanensis-Sphaerium anderssoni Assemblage is erected. This assemblage includes Arguniella yanshanensis, A. lingyuanensis and Sphaerium anderssoni and can be compared with the Jehol Biota. The age of the Sinuiju Formation is also clarified and on the basis of the bivalves and the presence of a Eosestheria–Ephemeropsis–Lycoptera(E–E–L) assemblage, the formation is not Upper Jurassic, but Lower Cretaceous in age.     

Occurrence of Cordaitales from lower Gondwana sediments of Ib-River Coalfield, Orissa, India: An Indian scenario

The Ib-River Coalfield in Orissa State is a part of Mahanadi Master Basin. Recent extensive investigations were conducted in this Coalfield to locate fossiliferous beds in the Lower Gondwana deposits and as a result a large cache of plant fossils were recovered from Lower Permian sediments (Barakar Formation) exposed in Jurabaga and Lajkura Collieries. The complete flora includes 23 genera representing nine orders viz., Lycopodiales, Equisetales, Sphenophyllales, Filicales, Cordaitales, Coniferales, Ginkgoales, Cycadales and Glossopteridales. Only the Cordaitales, represented by four genera i.e., Noeggerathiopsis, Cordaites, Euryphyllum and Kawizophyllum are discussed in this paper. Cordaitalean leaves are described for the first time from this coalfield; the remaining plant groups will be considered in a subsequent publication. Cordaitalean leaves attributable to Noeggerathiopsis hislopii, Noeggerathiopsis minor, Euryphyllum whittianum, Euryphyllum maithyi, Kawizophyllum dunpathriensis and Cordaites sp. constitute about 13.90% (111 specimens) of the total plant assemblage collected from this Coalfield. Of the cordaitaleans, N. hislopii is most abundant (47.75%; 53 specimens) followed by E. whittianum (40.54%; 45 specimens). A summary of the distribution of Cordaitales throughout the Indian Gondwana is also presented. Floristic composition varies stratigraphically at the two Barakar exposures (Lajkura and Jurabaga Collieries). Cordaitales are preserved only in the lowermost (4th) horizon (lower floral zone). Strata in these collieries have been assigned to the lower and upper Barakar Formation based on floristic content and an Early Permian (Artinskian) age is assigned.     

Palynology of seafloor samples collected by the 1911–14 Australasian Antarctic expedition: Implications for the geology of coastal East Antarctica

Fifty‐three sea‐floor samples close to Antarctica collected by Douglas Mawson during the Australasian Antarctic Expedition of 1911–1914 have beeen analysed for recycled palynomorphs. The distribution of the recycled microfossils provides a broad guide to the position of hidden sedimentary sequences on the Antarctic continental margin.

The samples were dredged off the East Antarctic coast between 91°E and 146°E. In three distinct ‐areas, concentrations of recycled palynomorphs suggest the presence nearby of eroding sedimentary sequences. Near the western edge of the Shackleton Ice Shelf the recycled suite suggests Early to Late Permian, Late Jurassic to mid‐Cretaceous, and Late Cretaceous to Early Tertiary sediments, with evidence for marine influence only in the Tertiary. Samples from the outer edge of the continental shelf and slope east of Cape Carr indicate Early Cretaceous and Late Cretaceous to Early Tertiary sequences, and the same age span is suggested by samples from the western side of the Mertz Glacier Tongue; in this area radio echosounding has suggested that inland sedimentary basins intersect the coast.

The sedimentary sequence predicted for the Shackleton Ice Shelf area probably faced the open Indian Ocean, at least since the Mesozoic. Cretaceous sequences predicted for the other localities occur at points on the Antarctic coast where they would be expected on the basis of most reconstructions. The area east of Cape Carr has as its conjugate’ coast part of the Great Australian Bight Basin; that off the Mertz Glacier, the area west of the Otway Basin. At both these areas on the southern Australian margin thick Cretaceous rift‐valley sequences occur.     

Radiolarian-bearing conglomerate from the Hayang Group, the Kyongsang Supergroup, southeastern Korea

The non-marine Cretaceous Kyongsang Supergroup, which is divided into the Sindong, the Hayang and the Yuchon groups, is widely distributed in southeastern Korea. Radiolarian-bearing pebbles are collected from the conglomerates of the Kumidong and the Kisadong formations of the Hayang Group. The age of radiolarian fossils range from Late Permian to Middle Jurassic. In Korea, Permian to Middle Jurassic marine chert beds are not exposed. The directions of paleocurrents of the Kumidong and the Kisadong formations are mainly from the northeast to southwest. During Cretaceous time, the Mino-Tamba Belt, within which Permian to Middle Jurassic chert beds are exposed, is suggested to have been located northeast of the Kyongsang Basin. The radiolarian faunas of the Hayang Group are similar to those of the Mino-Tamba Belt and other associated Mesozoic accretionary belts in Japan (e.g. the Ashio Belt). The provenance of the radiolarian-bearing pebbles collected from the Kumidong and the Kisadong formations is interpreted to be the Mino-Tamba Belt and other associated Mesozoic accretionary belts in Japan.     

Gondwana and Cathaysian blocks,palaeotethys sutures and cenozoic tectonics in South-east Asia

The Triassic Indosinian Orogeny followed extinction of the Palaeotethys Ocean resulting in suturing of Gondwana affinity and Cathaysian blocks.The Gondwana affinity Sinoburmalaya block of Peninsular Malaysia, characterized by Carboniferous—Permian mudstones containing glacial dropstones and sparse fauna and flora, is traced extensively into Sumatra. This mudstone facies is flanked on the east by a sandstone-dominated facies and by carbonate localized in the Kinta Valley. The muddy and sandy facies both begin with a basal Carboniferous condensed red bed sequence, which unconformably overlies the older formations of Sinoburmalaya. Both facies also demonstrate a Late Permian conformable transition into overlying limestone. The Cathaysian block of East Malaya is characterized by Late Permian Gigantopteris flora and fusulinid limestones associated with andesitic volcanism. It is similar but not identical to the West Sumatra Carboniferous—Permian block, characterized by Early Permian volcanism, fusulinid limestones and early Cathaysian Jambi flora.The South to SSE trending central Peninsular Malaysian Triassic orogenic belt swings south-east from Singapore to Bangka, then east to Billiton. The Palaeotethys suture (Bentong—Raub Line) forms the western margin of this belt and is therefore unlikely to continue south along the Palaeogene Bengkalis Graben, which transects the north-west—south-east orogenic fabric of Sumatra.The oroclinal bending of the Indosinian Orogen, from a north-west—south-east grain in Sumatra to a northerly grain through Peninsular Malaysia, is attributed to the Palaeocene collision of India and its subsequent indentation into Eurasia. The bending was accomplished by clockwise rotation and right-lateral shear parallel to the orogenic grain. The Mesozoic Palaeotethyan sutures were transformed into Palaeocene and younger shear zones. The outer zones of the orocline experienced pull apart tectonics (Andaman Sea and Sumatra basins) while the inner part (East Malaya to Billiton), being compressional, lacks Cenozoic basins.     

Palynological evidence for late Holocene environmental change on the Gimhae fluvial plain,Southern Korean peninsula: Reconstructing the rise and fall of Golden Crown Gaya State

This paper presents the results of detailed studies of palynomorphs recovered from two cores collected near the Yeanri burial mound on the Gimhae fluvial plain. Two local pollen zones were recognized on the basis of variations in the palynofloral assemblage: a lower Pollen Zone I, dominated by a Pinus‐Quercus assemblage, and an upper Pollen Zone II, dominated by a Pinus‐Quercus‐Gramineae assemblage. The palynological and molluscan analyses indicate that the depositional environments changed from a lower intertidal flat of a shallow bay environment to an upper intertidal flat in a shallow bay (before 1280 ± 110 ¹⁴C yr B.P.), and finally to a fluvial plain similar to that of today. This environmental change may have resulted from uplift along the Yangsan Fault. Afterward, the exposed area was modified by human activities, as indicated by a sudden increase in grassland herbaceous pollen grains. The loss of this bay likely had a dramatic effect on the Golden Crown Gaya State (3rd–7th centuries A.D.), which used it as a major port for regional trade, and may explain why it eventually merged with the Shilla State. © 2003 Wiley Periodicals, Inc.     

Meso–Cenozoic cooling and exhumation history of the Orlica‐Śnieżnik Dome (Sudetes,NE Bohemian Massif,Central Europe): Insights from apatite fission‐track thermochronometry

This study presents the first suite of apatite fission‐track (AFT) ages from the SE part of the Western Sudetes. AFT cooling ages from the Orlica‐?nie?nik Dome and the Upper Nysa K?odzka Graben range from Late Cretaceous (84 Ma) to Early Palaeocene–Middle Eocene (64–45 Ma). The first stage of basin evolution (~100–90 Ma) was marked by the formation of a local extensional depocentre and disruption of the Mesozoic planation surface. Subsequent far‐field convergence of European microplates resulted in Coniacian–Santonian (~89–83 Ma) thrust faulting. AFT data from both metamorphic basement and Mesozoic sedimentary cover indicate homogenous Late Cretaceous burial of the entire Western Sudetes. Thermal history modeling suggests that the onset of cooling could be constrained between 89 and 63 Ma with a climax during the Palaeocene–Middle Eocene basin inversion phase.     

Sedimentary response to the paleogeographic and tectonic evolution of the southern North China Craton during the late Paleozoic and Mesozoic

With the aim of constraining the influence of the surrounding plates on the Late Paleozoic–Mesozoic paleogeographic and tectonic evolution of the southern North China Craton (NCC), we undertook new U–Pb and Hf isotope data for detrital zircons obtained from ten samples of upper Paleozoic to Mesozoic sediments in the Luoyang Basin and Dengfeng area. Samples of upper Paleozoic to Mesozoic strata were obtained from the Taiyuan, Xiashihezi, Shangshihezi, Shiqianfeng, Ermaying, Shangyoufangzhuang, Upper Jurassic unnamed, and Lower Cretaceous unnamed formations (from oldest to youngest). On the basis of the youngest zircon ages, combined with the age-diagnostic fossils, and volcanic interlayer, we propose that the Taiyuan Formation (youngest zircon age of 439 Ma) formed during the Late Carboniferous and Early Permian, the Xiashihezi Formation (276 Ma) during the Early Permian, the Shangshihezi (376 Ma) and Shiqianfeng (279 Ma) formations during the Middle–Late Permian, the Ermaying Group (232 Ma) and Shangyoufangzhuang Formation (230 and 210 Ma) during the Late Triassic, the Jurassic unnamed formation (154 Ma) during the Late Jurassic, and the Cretaceous unnamed formation (158 Ma) during the Early Cretaceous. These results, together with previously published data, indicate that: (1) Upper Carboniferous–Lower Permian sandstones were sourced from the Northern Qinling Orogen (NQO); (2) Lower Permian sandstones were formed mainly from material derived from the Yinshan–Yanshan Orogenic Belt (YYOB) on the northern margin of the NCC with only minor material from the NQO; (3) Middle–Upper Permian sandstones were derived primarily from the NQO, with only a small contribution from the YYOB; (4) Upper Triassic sandstones were sourced mainly from the YYOB and contain only minor amounts of material from the NQO; (5) Upper Jurassic sandstones were derived from material sourced from the NQO; and (6) Lower Cretaceous conglomerate was formed mainly from recycled earlier detritus.The provenance shift in the Upper Carboniferous–Mesozoic sediments within the study area indicates that the YYOB was strongly uplifted twice, first in relation to subduction of the Paleo-Asian Ocean Plate beneath the northern margin of the NCC during the Early Permian, and subsequently in relation to collision between the southern Mongolian Plate and the northern margin of the NCC during the Late Triassic. The three episodes of tectonic uplift of the NQO were probably related to collision between the North and South Qinling terranes, northward subduction of the Mianlue Ocean Plate, and collision between the Yangtze Craton and the southern margin of the NCC during the Late Carboniferous–Early Permian, Middle–Late Permian, and Late Jurassic, respectively. The southern margin of the central NCC was rapidly uplifted and eroded during the Early Cretaceous.     

Palynoassemblages associated with a theropod dinosaur from the Snow Hill Island Formation (lower Maastrichtian) at the Naze,James Ross Island,Antarctica

The Cape Lamb Member of the Snow Hill Island Formation at The Naze on the northern margin of James Ross Island, east of the Antarctic Peninsula, yielded a theropod dinosaur recovered near the middle of a 90 m thick section that begins at sea level, ends below a basalt sill, and is composed of interbedded green–gray massive and laminated fine-grained sandstones and mudstones. Sixteen palynoassemblages were recovered from this section, which yielded moderately diverse assemblages with a total of 100 relatively well-preserved species. The principal terrestrial groups (32%) are represented by lycophytes (8 species), pteridophytes (15 species), gymnosperms (13 species), angiosperms (21 species) and freshwater chlorococcaleans (3 species). Marine palynomorphs (68%) belong to dinoflagellates (61 species), chlorococcaleans (6 species), and one acritarch. The vertical distribution of selected species allows the distinction of two informal assemblages, the lower Odontochitina porifera assemblage from the base to its disappearance in the lower part of the section, and the remaining section characterized by the Batiacasphaera grandis assemblage. The global stratigraphic ranges of selected palynomorphs suggest an early Maastrichtian age for this section and the entombed dinosaur that is also supported by the presence of the ammonoid Kitchinites darwinii. These assemblages share many species with latest Campanian–early Maastrichtian palynofloras from Vega and Humps Islands, New Zealand, and elsewhere in the Southern Ocean, establishing a good correlation among them. The dominance or frequent presence of dinoflagellates throughout the section supports the general interpretation of a shelf marine depocenter. The consistent presence of terrestrial palynomorphs suggests contributions from littoral/inland environments.     

柴达木盆地东部扎布萨尕秀组的时代归属讨论

柴达木盆地石炭系是中国北方新区新层系油气勘探调查研究的热点,盆地东部地区石炭系出露较全,但多数学者认为柴东地区不存在二叠系。针对扎布萨尕秀组归属于石炭纪还是二叠纪的争议,采集扎布萨尕秀组的砂岩碎屑锆石开展了U-Pb LA-ICP-MS同位素测年,获得40个和谐年龄分布在2488±34 Ma至288±3 Ma之间,最年轻的一组碎屑锆石的加权平均年龄288.0±2.0 Ma（MSWD=0.112,n=21）。这意味着该扎布萨尕秀组中的砂岩沉积于288 Ma之后,晚于国际石炭—二叠纪界限（299 Ma）。依据野外调查和已有研究成果,扎布萨尕秀组中赋存丰富的虫筳科化石,其中膨胀型虫筳属Pseudoschwagerina或Sphaeroschwagerina的出现是进入二叠纪的重要标志。结合碎屑锆石年代学和虫筳属化石特征,扎布萨尕秀组应归属早二叠世,说明柴达木东部地区存在二叠纪沉积记录。该认识为深化柴达木盆地晚古生代—中生代沉积建造和构造演化提供了重要的地层学证据。      

Small shelly fossils from the early Cambrian Yanjiahe Formation,Yichang, Hubei,China

Abundant data have been acquired on the lower Cambrian small shelly fossils (SSFs) of the Yangtze platform during the last three decades, demonstrating that these fossils are an important piece of evidence for the Cambrian radiation and are useful biostratigraphic tools for correlating the lower Cambrian. Here we report SSF associations from the Yanjiahe Formation in the Three Gorges area, South China. The Yanjiahe Formation is well exposed near the Yanjiahe village, and its 40-m-thick sequence can be subdivided on the basis of lithology into five stratigraphic intervals (beds). Small shelly fossils occur mainly in Beds 2 and 5, but abundant SSFs were discovered in thin sections of siliceous–phosphatic nodules from Bed 3 for the first time. No skeletal fossils were discovered in the basal siliceous rock interval (Bed 1), but the negative δ¹³C_carb excursion and the occurrence of the acritarch Micrhystridium regulare indicate that it belongs to the basal Cambrian. The SSF associations are somewhat similar to those of East Yunnan, and can be differentiated into three biozones (in ascending order): the Anabarites trisulcatus–Protohertzina anabarica assemblage zone (Bed 2), the Purella antiqua assemblage zone (Bed 3), and the Aldanella yanjiaheensis assemblage zone (Bed 5). The occurrence of A. yanjiaheensis in Bed 5 probably indicates that Bed 5 belongs to Cambrian Stage 2, but the Stage 2/Stage 1 boundary is uncertain since Bed 4 lacks fossils. SSF biostratigraphy indicates that the Yanjiahe Formation is pretrilobitic Meishucunian in age (equivalent to the Nemakit–Daldynian to Tommotian of Siberia, Terreneuvian). Five SSF genera occur in Bed 2, more than six genera in Bed 3, and twenty-three genera in Bed 5. The stepwise increase in generic diversity through the Yanjiahe Formation is comparable with the global diversity increase through the Nemakit–Daldynian to early Tommotian interval.     

西秦岭甘加地区OIB型钾质拉斑玄武岩的发现:对西秦岭晚中生代大陆裂谷作用的启示

西秦岭晚中生代火山岩出露于青海省泽库县多福屯地区、甘肃省夏河县红墙和甘加地区。初步研究表明,甘加火山岩属于一套钾质拉斑玄武岩。该玄武岩富集REE、LILE及HFSE,但轻、重稀土元素分馏程度及不相容元素含量均略低于典型OIB和西秦岭晚中生代钠质碱性玄武岩。岩浆起源于软流圈释放的小体积富挥发份硅酸盐熔体交代形成的富集岩石圈地幔,并在上升中经历了较大程度的镁铁质矿物的分离结晶作用。岩石具有典型的陆内OIB成因特点,既不同于前人提出的甘加海山玄武岩,也不属于“二叠纪隆务峡-甘加蛇绿岩”组成部分,而与西秦岭晚中生代钠质碱性玄武岩均为大陆裂谷系OIB型岩浆作用的产物。甘加玄武岩可能具有比较复杂的岩石组合,跨越了晚古生代到晚中生代的一个较长时间范围。西秦岭晚中生代的大陆裂谷作用夭折于岩石圈拉张的早期阶段,它的出现及研究区广泛发育的近SN向或NW向断裂,可能是贺兰-川滇南北构造带与大型走滑断裂系复杂叠加并相互影响与改造的表现。