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1.
The Ordovician intra-oceanic Macquarie Arc of eastern Australia collided with the eastern Gondwanan margin at ~440 Ma. However, the deep crustal architecture resulting from this assembly is poorly known. This is addressed here by a zircon U-Pb-Hf study of the post-assembly Silurian Browns Creek Intrusive Complex and Davies Creek Granite dykes that intrude into the arc, and not adjacent Gondwanan sedimentary sequences. Zircon UPb dating integrated with CL imagery indicate two igneous phases at 430–437 Ma and 420–426 Ma and a zircon recrystallisation phase at 395–396 Ma attributed to a late thermal event. The magmatic zircon initial ɛHf values vary from −5.1 to +4.7. This signature indicates the source of these granitic rocks is strongly influenced by typical pre-Silurian Gondwanan material. Granitic rock and zircon compositions demonstrate that at the likely temperature of the Silurian granitic magma, especially the Davies Creek Granite dykes, inherited source zircons were mostly dissolved, explaining the absence of pre-Ordovician xenocrysts within the zircon population. The unradiogenic Hf isotopic signatures preserved in the Silurian magmatic zircons demonstrate the contribution of Gondwanan crustal material to the magma source region. These results support the interpretation of the Macquarie Arc as an intra-Panthalassa ocean allochthon, emplaced and resting over the edge of Gondwanan crystalline basement, possibly including the continent-derived sedimentary rocks of the Adaminaby Group.  相似文献   

2.
Megaraptoridae comprises a clade of enigmatic Gondwanan theropods with characteristic hypertrophied claws on the first and second manual digits. The majority of megaraptorids are known from South America, although a single genus (Australovenator) plus additional indeterminate material is also known from Australia. This clade has a controversial placement among theropods, and recently has been interpreted alternatively as a carcharodontosaurian or a tyrannosauroid lineage. We describe new fragmentary but associated postcranial remains from the opal fields of Lightning Ridge (middle-Albian, Griman Creek Formation) in north-central New South Wales. The new unnamed taxon exhibits a number of unusual features that suggest the presence of a hitherto unrecognised Australian megaraptorid. From an Australian perspective, the Lightning Ridge taxon predates Australovenator by ca. 10 Ma and is minimally coeval with megaraptoran material reported from the Eumeralla Formation of Victoria (but potentially 6.1–9.5 Ma younger). It is also notable as the largest predatory dinosaur yet identified from Australia and is only the second theropod known from more than a single element. A Bayesian phylogenetic approach integrating morphological, stratigraphic and palaeogeographic information tested both the carcharodontosaurian and tyrannosauroid placements for Megaraptora. Regardless of the preferred placement among Tetanurae, rigorous palaeobiogeographic analyses support an Asian origin of Megaraptora in the latest Jurassic (about 150–135 Ma), an Early Cretaceous (about 130–121 Ma) divergence of the Gondwanan lineage leading to Megaraptoridae, and an Australian root for megaraptorid radiation. These results indicate that Australia's Cretaceous dinosaur fauna did not comprise simply of immigrant taxa but was a source for complex two-way interchange between Australia–Antarctica–South America leading to the evolution of at least one group of apex predatory dinosaurs in Gondwana.  相似文献   

3.
The biogeography of Cretaceous Australian dinosaur fauna has been characterized variously as endemic, cosmopolitan or closely related to other Gondwanan faunas. Over the past decade, a large number of new Australian dinosaur taxa have been described and included in phylogenetic analyses, allowing for new insights into their biogeographical affinities to be obtained. Here, I combine the latest phylogenies of Australian dinosaurs into a supertree that includes as many Australian taxa as possible and apply it to the construction of biogeographical networks of Cretaceous dinosaurs. The results show that the Cretaceous dinosaurs of Australia have a strong connection with South American dinosaurs and to those of other Gondwanan continents via South America. Community detection algorithms indicate that the Gondwanan continents form a community within Cretaceous dinosaur biogeographical networks. The biogeographical affinities between Australia and Laurasia detected in previous studies were largely due to the scarce dinosaur fossil record of Gondwana at that time and to the unstable phylogenetic position of Australian dinosaurs because of the fragmentary nature of their fossils. Continuing discoveries of new Australian taxa and refinement of resulting phylogenetic analyses can further deepen our understanding of the biogeographical history of Australia.  相似文献   

4.
研究了美国绿河盆地的23个未成熟的露头油页岩样品,其中 13个样品取自Laney组,为半温湿半干燥气候下沉积于较浅的封闭水体的盐湖中心,含有丰富的有机质;另外 10个样品取自LumanTongue组,为潮湿气候下沉积于近岸的水体开放的淡水环境,其有机质含量较低。所有样品均富含从C11至C20 的同分异构体丰富的饱和类异戊二烯醇类化合物。此外还检出了一整套直链一元仲醇同系物,其碳数从 10至 33,而羟基可在任何理论上可能的碳位上。伯醇含量较低。研究结果表明,绿河油页岩中的有机质分别在沉积过程中和被抬升之后遭受了两次微生物降解。除伯醇的分布有生物来源特征外,其余的开链醇化合物是在绿河层系抬升至地表后微生物对其中烃类化合物降解的产物。文中将绿河油页岩有机质中异常高的氧指数归因于微生物降解,并探讨了其开链醇化合物的分布与物源、沉积环境及微生物降解程度的相关性。盐湖相Laney组的直链醇以低碳数组分为主,反映其有机质以菌藻为主的物源,与干燥的古气候相一致;淡水相LumanTongue组则以高碳数组分为主,有着明显优势的高等植物来源,与其潮湿的古气候相吻合。在沉积过程中,淡水相的LumanTongue组中的有机质遭受了比盐湖相的Laney组中的有机质更强的微生物降解,这意味着盐湖环境。  相似文献   

5.
A newly identified tephra in stratified deposits in southwestern Utah, dated 14,000 14C yr B.P., may aid in correlating late Pleistocene deposits across parts of the southern Great Basin and west-central Colorado Plateau. Geochemical analyses of the ash suggest the tephra originated from Mono Craters, California, and most probably correlates with Wilson Creek ash #3. Because the ash is 2 mm thick 550 km from its source, the event may have been larger than others correlated to Mono Craters eruptions.  相似文献   

6.
The Hirnantian and Llandovery sedimentary succession of the Barrandian area has been assigned to middle and outer clastic‐shelf depositional settings, respectively. Deposition was influenced by the remote Gondwanan glaciation and subsequent, long‐persisting, post‐glacial anoxia triggered by a current‐driven upwelling system. High‐resolution graptolite stratigraphy, based upon 19 formally defined biozones—largely interval zones—and five subzones, enabled a detailed correlation between 42 surface sections and boreholes, and enabled linking of the sedimentary record, graptoloid fauna dynamics, organic‐content fluctuations and spectral gamma‐ray curves. The Hirnantian and Llandovery succession has been subdivided into four biostratigraphically dated third‐order sequences (units 1–4). Time–spatial facies distribution recorded early and late Hirnantian glacio‐eustatic sea‐level lowstands separated by a remarkable mid‐Hirnantian rise in sea‐level. A major part of the post‐glacial sea‐level rise took place within the late Hirnantian. The highstand of Unit 2 is apparently at the base of the Silurian succession. Short‐term relative sea‐level drawdown and a third‐order sequence boundary followed in the early Rhuddanian upper acuminatus Zone. Early Aeronian and late Telychian sea‐level highstands and late Aeronian drawdown of likely eustatic origin belong to units 3 and 4. Sea‐level rise culminated in the late Telychian, which may also be considered as a highstand episode of a second‐order Hirnantian–early Silurian cycle. Facies and sequence‐stratigraphic analysis supports recent interpretations on nappe structures in the core part of the Ordovician–Middle Devonian Prague Synform of the Barrandian. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

7.
An updated, annotated list of all tetrapods from the Adamantina, Uberaba and Marília formations (Bauru Group), which constitute some of the best studied Upper Cretaceous units in Brazil, is presented. Tetrapod diversity in the Bauru Group is remarkable, including an admixture of typically austral Gondwanan taxa (e.g., abelisaurids, notosuchians) and boreal Gondwanan forms (e.g., carcharodontosaurids). Of note is the absence of Laurasian taxa in the upper portion of the Bauru Group. With the exception of some turtles, an anuran, mesoeucrocodylians and one titanosaur, most taxa from the Bauru Group are based on fragmentary and isolated bones, and as such many specimens can be identified only to a higher taxonomic level. Fishes, turtles, anurans, mesoeucrocodylians, dinosaurs, birds and mammals from the Adamantina and Marília formations resemble the latest Late Cretaceous vertebrate faunas from southern South America, except for the absence of ornithischian dinosaurs.  相似文献   

8.
This paper reconstructs the use of space and defines activity areas within a single hut (Hut 8) at the Early Bronze Age village of Afragola (southern Italy). The village, consisting of a number of huts and other structures, was covered by approximately 1m of volcanic ash during the eruption of Vesuvius in 3550 ± 20BP. Thirteen samples were collected from inside the hut to analyze the spatial variability in sedimentary characteristics among three areas of Hut 8—the apsidal, central, and entrance areas. The micromorphological analysis revealed details about the occupation surface and its relationship to features and material remains in the hut not apparent in the field. The apsidal area was probably used for storage but not of solids, as no significant quantities of organic material were found. The central area contains a small oven, calcareous ash from fires, and organic material composed of charred remains and bone fragments and was likely used for small‐scale household tasks. A possible connection exists between the lithics and the microstratigraphic sequencing in the area west of the oven, suggesting that people congregated there to perform specific tasks. The entrance area contains highly compacted and heterogeneous sediments that were brought in from outside. Notable is the paucity of anthropogenic materials found inside the hut, especially given the remarkable preservation offered by the thick cover of volcanic ash. We hypothesize that Hut 8 was not occupied long enough to produce a large amount of debris or that it had limited indoor activities and was thoroughly cleaned. © 2010 Wiley Periodicals, Inc.  相似文献   

9.
Shales and phyllites from the turbidite sequences of the 2.9 Ga Mosquito Creek Formation of the East Pilbara, Western Australia contain varying amounts of paragonite and mixed Na–K micas (MNKMs), the 0 0 l X-ray diffraction reflections of which are unresolved from the 10-Å reflections, and only partly resolved from the 5-Å reflections of white K-mica (WKM). The Kübler index (‘crystallinity’), the full width at half maximum (FWHM) of the WKM, obtained from these composite reflections by applying a three-peak deconvolution procedure, reveals a metamorphic zoning of the Mosquito Creek Formation. The highest, “epimetamorphic”, grade occurs in the — largely Na-mica free — southern part, with lower, medium- to high-anchimetamorphic, grades in the central part, notably in a WSW-ENE anticlinal zone extending from Nullagine to the Blue Spec Mine. The Na-mica free metasediments of the Glen Herring Shale of the Fortescue Group, overlying the Mosquito Creek Formation to the W, show only a slightly lower metamorphic grade. The low b0 lattice parameter of the WKMs indicates a very low metamorphic P/T gradient. The Na-mica bearing metasediments of the Mosquito Creek Formation correspond to a kaolinite-bearing protolith, strongly Al-enriched and K-depleted with respect to the presumably granitic-tonalitic source rock.  相似文献   

10.
The Mesozoic sediments of Thakkhola (central Nepal) were deposited on a broad eastern north Gondwanan passive margin at mid-latitudes (28–41 °S) facing the Southern Tethys ocean to the north. The facies is strikingly similar over a distance of several thousand kilometres from Ladakh in the west to Tibet and to the paleogeographically adjacent north-west Australian margin (Exmouth Plateau, ODP Legs 122/123) and Timor in the east. Late Paleozoic rifting led to the opening of the Neo-Tethys ocean in Early Triassic times. An almost uninterrupted about 2 km thick sequence of syn-rift sediments was deposited on a slowly subsiding shelf and slope from Early Triassic to late Valanginian times when break-up between Gondwana (north-west Australia) and Greater India formed the proto-Indian Ocean. The sedimentation is controlled by (1) global events (eustasy; climatic/oceanographic changes due to latitudinal drift; plate reorganization leading to rift-type block-faulting) and (2) local factors, such as varying fluvio-deltaic sediment input, especially during Permian and late Norian times. Sea level was extremely low in Permian, high in Carnian and low again during Rhaeto-Liassic times. Third-order sea-level cycles may have occurred in the Early Triassic and late Norian to Rhaeto-Liassic. During the Permian pure quartz sand and gravel were deposited as shallowing upward series of submarine channel or barrier island sands. The high compositional maturity is typical of a stable craton-type hinterland, uplifted during a major rifting episode. During the early Triassic a 20–30 m thick condensed sequence of nodular ‘ammonitico rosso’-type marlstone with a ‘pelagic’ fauna was deposited (Tamba Kurkur Formation). This indicates tectonic subsidence and sediment starvation during the transgression of the Neo-Tethys ocean. During Carnian times a 400 m thick sequence of fining upward, filament-rich wackestone/shale cycles was deposited in a bathyal environment (Mukut Formation). This is overlain by about 300 m of sandy shale and siltstone intercalated with quartz-rich bioclastic grain- to rudstone (Tarap Shale Formation, late Carnian-Norian). The upper Norian to (?lower) Rhaetian Quartzite Formation consists of (sub)arkosic sandstones and pure quartz arenites, indicating different sediment sources. The fluvio-deltaic sandstones are intercalated with silty shale, coal and bioclastic limestone, as well as mixed siliciclastic-bioclastic rocks. The depositional environment was marginal marine to shallow subtidal. The fluvio-deltaic influence decreased towards the overlying carbonates of Rhaeto-Liassic (?) age (Jomosom Formation correlative with the Kioto Limestone), when the region entered tropical paleolatitudes resulting in platform carbonates.  相似文献   

11.
Nonconnah Creek, located in the loess-mantled Blufflands along the eastern wall of the Lower Mississippi Alluvial Valley in Tennessee displays a sedimentary sequence representing the Altonian Substage through the Woodfordian Substage of the Wisconsinan Stage. The site has a biostratigraphic record for the Altonian and Farmdalian Substages that documents warm-temperate upland oak-pine forest, prairie, and bottomland forest. At 23,000 yr B.P., white spruce and larch migrated into the Nonconnah Creek watershed and along braided-stream surfaces in the Mississippi Valley as far as southeastern Louisiana. The pollen and plant-macrofossil record from Nonconnah Creek provides the first documentation of a full-glacial locality in eastern North America for beech, yellow poplar, oak, history, black walnut, and other mesic deciduous forest taxa. During the full and late glacial, the Mississippi Valley was a barrier to the migration of pine species, while the adjacent Blufflands provided a refuge for mesic deciduous forest taxa. Regional climatic amelioration, beginning about 16,500 yr B.P., is reflected by increases in pollen percentages of cooltemperate deciduous trees at Nonconnah Creek. The demise of spruce and jack pine occurred 12,500 yr B.P. between 34° and 37° N in eastern North America in response to postglacial warming.  相似文献   

12.
The Tropic Shale and correlative Tununk Shale Member of the Mancos Shale accumulated during Cenomanian-Turonian time, within prodeltaic environments near the western margin of the Western Interior Seaway of North America. Stratigraphical and sedimentological analysis has revealed a detailed history of relative sea level change in the thick, fine grained succession. The Tropic and Tununk shales were deposited during the Greenhorn second-order sea level cycle, over a time span of about 2–5 million years. In southern Utah, six depositional sequences are superposed upon the record of this long term sea level change. The sequences developed during third-order relative sea level cycles of hundreds of thousands of years duration and are composed of at least 37 parasequences, arranged in retrogradational, aggradational and progradational parasequence sets. The Tropic Shale and Tununk Shale Member accumulated just basinward of the axis of maximum subsidence of a foreland basin. Stratal geometries and facies distribution patterns in the succession indicate that in southern Utah the Greenhorn cycle was tectonically controlled. During the Greenhorn transgression and highstand, rapid rates of tectonic subsidence trapped terrigenous sediment to the west of the study area, in the more proximal foreland. At this time, hemipelagic facies accumulated at relatively slow rates in southern Utah and type 2 sequences developed during third-order sea level cycles. In contrast, during the Greenhorn regression rates of thrust-induced subsidence in the proximal foreland basin evidently slowed, and deltaic clinoforms prograded across the study area. At least one forced regression occurred in southern Utah at this time, and type 1 sequences developed. The formation of type 1 sequence boundaries in the upper part of the Tropic Shale and Tununk Shale Member points to episodes of base level fall and indicates that the six third-order sea level cycles recorded in the succession were not the result of changes in sediment supply alone. The third-order cycles may have been a consequence of episodic tectonism. The timing of these cycles, however, suggests that development of sequences and parasequences in the Tropic Shale and Tununk Shale Member may have been related to orbital forcing in the Milankovitch band. Glacioeustasy or climatically related fluctuations in the amount of groundwater stored on continents may explain these high frequency sea level changes.  相似文献   

13.
The southwestern Pacific region consists of segmented and translated continental fragments of the Gondwanan margin. Tectonic reconstructions of this region are challenged by the fact that many fragmented continental blocks are submerged and/or concealed under younger sedimentary cover. The Queensland Plateau (offshore northeastern Australia) is one such submerged continental block. We present detrital zircon geochronological and morphological data, complemented by petrographic observations, from samples obtained from the only two drill cores that penetrated the Paleozoic metasedimentary strata of the Queensland Plateau (Ocean Drilling Program leg 133, sites 824 and 825). Results provide maximum age constraints of 319.4 ± 3.5 and 298.9 ± 2.5 Ma for the time of deposition, which in conjunction with evidence for deformation, indicate that the metasedimentary successions are most likely upper Carboniferous to lower Permian. A comparison of our results with a larger dataset of detrital zircon ages from the Tasmanides suggests that the Paleozoic successions of the Queensland Plateau formed in a backarc basin that was part of the northern continuation of the New England Orogen and/or the East Australian Rift System. However, unlike most of the New England Orogen, a distinctive component of the detrital zircon age spectra of the Mossman Orogen is also recognised, suggesting the existence of a late Paleozoic drainage system that crossed the northern Tasmanides en route from the North Australian Craton. A distinctive shift from abraded zircon grains to grains with well-preserved morphology at ca 305 Ma reflects a direct drainage of first-cycle sediments, most likely from an outboard arc and/or backarc magmatism.  相似文献   

14.
The Australian continent has one of the best-preserved impact-cratering records on Earth, closely rivalling that of North America and parts of northern Europe, and the rate of new discoveries remains high. In this review 26 impact sites are described, including five small meteorite craters or crater fields associated with actual meteorite fragments (Boxhole, Dalgaranga, Henbury, Veevers, Wolfe Creek) and 21 variably eroded or buried impact structures (Acraman, Amelia Creek, Connolly Basin, Foelsche, Glikson, Goat Paddock, Gosses Bluff, Goyder, Kelly West, Lawn Hill, Liverpool, Matt Wilson, Mt Toondina, Piccaninny, Shoemaker, Spider, Strangways, Tookoonooka, Woodleigh, Yallalie, Yarrabubba). In addition a number of possible impact structures have been proposed and a short list of 22 is detailed herein. The Australian cratering record is anomalously biased towards old structures, and includes the Earth's best record of Proterozoic impact sites. This is likely to be a direct result of aspects of the continent's unique geological evolution. The Australian impact record also includes distal ejecta in the form of two tektite strewn fields (Australasian strewn field, ‘high-soda’ tektites), a single report of 12.1?–?4.6 Ma microtektites, ejecta from the ca 580 Ma Acraman impact structure, and a number of Archaean to Early Palaeoproterozoic impact spherule layers. Possible impact related layers near the Eocene?–?Oligocene and the Permian?–?Triassic boundaries have been described in the literature, but remain unconfirmed. The global K?–?T boundary impact horizon has not been recognised onshore in Australia but is present in nearby deep-sea cores.  相似文献   

15.
This study presents the first chemical abrasion-isotope dilution thermal ionisation mass spectrometry (CA-IDTIMS) U–Pb zircon ages from tuffs in Lopingian (upper Permian) strata of the Galilee Basin, Queensland and reassigns the B coal-seam to the ‘Burngrove Formation equivalent.’ Five Lopingian tuffs were dated: four from the CRD Montani-1 drill hole including three from the ‘Fair Hill Formation equivalent’ (255.13 ± 0.09, 254.41 ± 0.07 and 254.32 ± 0.10 Ma) and one from the ‘Burngrove Formation equivalent’ (252.81 ± 0.07 Ma, approximately the age of the Yarrabee Tuff in the adjacent Bowen Basin); and a single tuff from the Black Alley Shale in the GSQ Tambo-1-1A drill hole (254.09 ± 0.06 Ma). In the Galilee Basin, all three units are constituents of the Betts Creek Group, here formally elevated in nomenclatural status from the Betts Creek beds. On the western margin of the basin, the group thins, and the ‘J and K’ seams (formerly known as the Crossmore and Glenaras sequences, respectively) in the GSQ Muttaburra-1 drill hole have been interpreted through palynology as Cisuralian–early Guadalupian (spore-pollen assemblage APP3.2). This corroborates the exclusion of the ‘J and K’ seams from the overlying Lopingian Betts Creek Group (spore-pollen assemblage APP5), and the underlying lower to mid-Cisuralian Aramac Coal Measures (spore-pollen assemblage APP2.2), which represent the uppermost unit of the Joe Joe Group. It is proposed that the ‘J and K’ seams are restricted to a depocentre in the Hulton–Rand structure. The recognition of these strata containing APP3.2 spore-pollen assemblages suggests that the mid-Permian hiatus is locally reduced to 12–13 My from 30 Ma (where the ‘J and K’ seams are absent). The results of the radiometric dating and palynological analysis in the Galilee Basin support the proposed, albeit informal stratigraphy, that is given in terms of equivalents of formational units in the Bowen Basin and on the intervening Springsure Shelf.  相似文献   

16.
Benthic foraminiferal populations through 1991–94 were investigated by taking cores and in situ observations from the submersible Shinkai 2000 in Sagami Bay, Japan (1450 m water depth). At this location, a strong spring bloom causes seasonal deposition of phytodetrital material to the sea floor. The population size of benthic foraminifera is mainly controlled by this seasonal flux of organic matter, which triggers rapid, opportunistic reproduction of the shallow infaunal taxa Bolivia pacifica and Textularia kattegatensis . We propose that these species have a one-year life cycle. The deep infaunal taxa Globobulimina affinis and Chilostomella ovoidea show less pronounced seasonal fluctuations in population size, and seem to have a life cycle longer than two years. The foraminifera migrate vertically through the sediment, down to the maximum depth to which the sediment is oxygenated. The seasonal flux of organic matter thus is the most important determinant of population size, microhabitats, and reproduction in Sagami Bay. Such foraminifera are extremely relevant in the functioning of the global carbon cycle, especially at the interface of the hydrosphere and lithosphere.  相似文献   

17.
The identification and correlation of the Carboniferous-Permian (Gzhelian-Asselian) boundary within the sedimentary sequences of Gondwana has always been a topic of debate. Type latest Carboniferous and earliest Permian marine sequences are characterised by warm tropical faunas and come from the Uralian Region of Russia and Kazakhstan. Faunas include conodonts and fusulinid foraminiferids which are prime tools for correlation. Such faunal groups are absent from most Gondwanan sequences where reliance for correlations must be placed primarily on brachiopods, bivalve molluscs and palynology. The Western Australian marine sequences, with their contained ammonoids, provide a pivotal link for the dating and correlating of Early Permian Gondwanan sequences with those of the type regions and their palynostratigraphical record is essential for trans-Australian correlations and correlations elsewhere throughout Gondwanaland.New data from the fully cored DM Tangorin DDHl bore hole, drilled in the Cranky Corner Basin, New South Wales, Australia, reveals a sequence of descending faunal zones. The stratigraphically highest zone with Eurydesrna cordaturn, encompasses the Late Sakmarian (Sterlitamakian). The middle zone with Torniopsis elongata, Sulciplica c r a m and Trigonotreta tangorini straddles the Sterlitamakian-Tastubian boundary, with the palynomorphs Pseudoreticulatispora pseudoreticulata high in the zone and Granulatisporites confluens low in the zone. An impoverished fauna with Trigonotreta nov., low in the Granulatisporites confluens Zone, is probably of latest Asselian or Tastubian age.Significant new data from Argentina has revealed marine faunas from below the occurrence of Granulatisporites confluens. These are considered to be of Asselian age. Outcrops of the Tupe Formation, with a marine fauna, at La Herradura Creek in the western Paganzo Basin, San Juan Province, are best regarded as being of mid to late Asselian age. The Tupe Fauna has been recognised as the Tivertonia jachalensis-Streptorhynchus inaequiornatus Zone. Previously, this fauna was considered to be of Late Carboniferous or Stephanian age. Three faunal associations are known from the Rio del Peii6n Formation, Rio Blanco Basin, La Rioja Province. The middle assemblage with Tivertonia, Costaturnulus, Kochiproductus and Trigonotreta, appears to correlate well with the Tupe Formation fauna. The lower assemblage, with Streptorhynchus, Etherilosia, Costaturnulus, Trigonotreta and a punctate spiriferid, as well as indeterminate productids, probably of Early Asselian age. The youngest assemblage includes a species ofRhynchopora that is close to Rhynchopora australasica from the latest Asselian-early Tastubian of Western Australia. The marine biostratigraphical data from Argentina has enabled a much greater understanding of the earliest Permian marine faunas to be achieved - a story that is apparently absent from the other cold and cool temperate regions of Gondwana.  相似文献   

18.
从史料记载看中国历史时期海面波动   总被引：5，自引：0，他引：5  
广泛采用文字类海面变化“代用资料”是历史时期小尺度海面波动研究的重要手段，将史籍中有关海面波动的记载与考古学和沉积地层学证据相结合进行综合分析，可以初步认定：我国历史时期2ka年来，西汉至两晋为相对高海面时期（西汉晚期为显著高海面时期）；晋末至隋末为相对低海面时期，唐至南宋为相对高海面时期，尤其是8世纪，11世纪后期至13世纪初期出现显著高海面，而其间的唐末至五代，南宋后期至元初曾出现过海面下降；元明清时期总体为相对低海面时期，但在元中后期至明初，16世纪上半叶，17世纪末至18世纪初分别出现几次相对高海面。  相似文献   

19.
The well-refined Permian palynozonation of Western and eastern Australia is the current standard biostratigraphic scheme for the Southern Hemisphere, but intra-Gondwanan floristic provincialism means that several stratigraphically useful palynomorph taxa are rare or absent elsewhere in Gondwana. Radio-isotopic ages for both Australia and the main Karoo Basin of South Africa demonstrate that key marker taxa appear diachronously in the two countries, or they are absent in one of the countries. The establishment of new plant taxa in the Gondwanan Permian realm was strongly tied to palaeolatitude, with floral distributions primarily affected by temperature, precipitation, and seasonality. This spatio-temporal variation of floras hinders global biostratigraphic correlations. Both South Africa and Australia have excellent long-ranging Permo-Triassic terrestrial sedimentary successions, and although vertebrate biostratigraphy has been the focus of much research endeavour in the South African Karoo, palynological studies have lagged. Accordingly, a new South African palynozonation should be established that is based on the first appearances of key index taxa in the main Karoo Basin, rather than elsewhere in Gondwana. In the interim, the diachronous ranges of palynomorphs must be considered when correlating South African rocks to other global sections by means of the Australian spore‐pollen zonation.  相似文献   

20.
Patagonia has yielded the most comprehensive fossil record of Cretaceous theropods from Gondwana, consisting of 31 nominal species belonging to singleton taxa and six families: Abelisauridae, Noasauridae, Carcharodontosauridae, Megaraptoridae nov. fam., Alvarezsauridae, and Unenlagiidae. They provide anatomical information that allows improved interpretation of theropods discovered in other regions of Gondwana. Abelisauroids are the best represented theropods in Patagonia. They underwent an evolutionary radiation documented from the Early Cretaceous through to the latest Cretaceous, and are represented by the clades Abelisauridae and Noasauridae. Patagonian carcharodontosaurids are known from three taxa (Tyrannotitan, Giganotosaurus and Mapusaurus), as well as from isolated teeth, collected from Aptian to Cenomanian beds. These allosauroids constituted the top predators during the mid-Cretaceous, during which gigantic titanosaur sauropods were the largest herbivores. Megaraptorans have become better documented in recent years with the discovery of more complete remains. Megaraptor, Aerosteon and Orkoraptor have been described from Cretaceous beds from Argentina, and these taxa exhibit close relationships with the Aptian genera Australovenator, from Australia, and Fukuiraptor, from Japan. The Gondwanan megaraptorans are gathered into the new family Megaraptoridae, and the Asiatic Fukuiraptor is recovered as the immediate sister taxon of this clade. Although megaraptorans have been recently interpreted as members of Allosauroidea, we present evidence that they are deeply nested within Coelurosauria. Moreover, anatomical information supports Megaraptora as more closely related to the Asiamerican Tyrannosauridae than thought. Megaraptorans improve our knowledge about the scarcely documented basal radiation of Gondwanan coelurosaurs and tyrannosauroids as a whole. Information at hand indicates that South America was a cradle for the evolutionary radiation for different coelurosaurian lineages, including some basal forms (e.g., Bicentenaria, Aniksosaurus), megaraptorans, alvarezsaurids less derived than those of Laurasia, and unenlagiids, revealing that Gondwanan coelurosaurs played sharply differing ecological roles, and that they were taxonomically as diverse as in the northern continents. The unenlagiids represent an endemic South American clade that has been recently found to be more closely related to birds than to dromaeosaurid theropods. Analysis of the theropod fossil record from Gondwana shows the highest peak of origination index occurred during the Aptian–Albian and a less intense one in the Campanian time spans. Additionally, peaks of extinction index are recognized for the Cenomanian and Turonian–Coniacian time spans. In comparison, the Laurasian pattern differs from that of Gondwana in the presence of an older extinction event during the Aptian–Albian time-span and a high origination rate during the Cenomanian time-bin. Both Laurasian and Gondwanan theropod records show a peak of origination rates during the Campanian.  相似文献   

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