Is the Shuram Event Still Younger Than the 580 Million Years agoEdiacaran NeoProteorozoic Gaskiers Glaciation Though?

Silicified glendonites in the Ediacaran Doushantuo Formation (South China) and their potential paleoclimatic implications

Authors:

Wang et al

Abstract:

The Ediacaran Period is punctuated by the ca. 580 Ma Gaskiers glaciation in Newfoundland. However, paleoclimatic data are scarce in Ediacaran successions in South China, where abundant geochemical and paleobiological data are shaping current understanding of Ediacaran evolutionary and environmental history. Here, we report the occurrence of silicified glendonites in the Ediacaran Doushantuo Formation deposited in an inner-shelf environment on the South China block. Petrographic evidence suggests that these silicified glendonites are pseudomorphs after syndepositional or early authigenic ikaites formed at near-freezing temperatures. The glendonite-bearing stratigraphic interval is characterized by positive δ13C values. It predates both the negative δ13C excursion EN3 (widely believed to be an equivalent of the Shuram negative excursion) and excursion EN2. Although alternative interpretations may be possible, these glendonites may be related to and correlated with the Gaskiers glaciation. If confirmed, this correlation suggests that the Shuram event postdates the Gaskiers glaciation, thus having important implications for Ediacaran climate changes, carbon cycles, and biological evolution.

Five new Species of Ediacaran Biota Described From NeoProterozoic Lantian Formation of South China

Systematic description of putative animal fossils from the early Ediacaran Lantian Formation of South China

Authors:

Wan et al

Abstract:

The early Ediacaran Lantian Formation in South China contains some of the oldest known representatives of morphologically complex macroorganisms, including various macroalgae and putative animals. The macroalgal fossils have been described previously in several publications, but no taxonomic treatment has been published for the putative animal fossils. This hampers our ability to fully evaluate and communicate the significance of these potentially important Ediacaran macrofossils. To address this deficiency, here we provide a systematic description of these putative animal fossils from the Lantian Formation, including four new genera and five new species: Lantianella laevis gen. et sp. nov., L. annularis gen. et sp. nov., Piyuania cyathiformis gen. et sp. nov., Qianchuania fusiformis gen. et sp. nov. and Xiuningella rara gen. et sp. nov. Morphological comparisons of these fossils and potential modern analogues are provided and critically assessed.

Distribution and Evolution of Reef Builders in Carboniferous South China

Distribution and evolution of Carboniferous reefs in South China

Authors:

Yao et al

Abstract:

Reefs are sensitive proxies for palaeontological, palaeoenvironmental, and palaeogeographical changes during geological history. In South China, after the collapse of the reef ecosystem during the Frasnian-Famennian and Hangenberg mass extinction events, Carboniferous reefs underwent evolutionary episodes of recovery, decline, and turnover, which were controlled by changes of reef-builders abundance, sedimentary facies, relative sea level, and even global climate. In Tournaisian times, only a few Waulsortian-like banks have been found in Liuzhou, Guangxi without metazoan reefs, which were caused by the lack of reef-builders, such as colonial rugose corals and bryozoans, and the dominant non-carbonate facies (shale, mud stone and sandstone) driven by low relative sea level. The absence of mud mounds in the early Viséan was attributed to the regression event during the Tournaisian-Viséan boundary. During Viséan times, bryozoan-coral reefs in Huishui, Guizhou and Tianlin, Guangxi occurred during a time of increasing biodiversity and carbonate facies resulting from relative sea-level rise. The number of potential reef-builders as colonial rugose coral and bryozoan genera significantly increased in Viséan times in South China. The reef abundance declined during Serpukhovian times in South China and the controlling factors were decreasing abundance of potential reef-builders and developing non-carbonate facies due to a relative sea-level fall. The sedimentary facies were characterized by shale, mud stone, sandstone, and dolostone during this time. A distinct change in reef types occurred after the Mississippian-Pennsylvanian boundary, when phylloid algae and red algae reefs (distributed in Ziyun, Guizhou and Beibuwan, Guangxi) replaced metazoan reefs and became the dominant role in reef ecosystem. This reef turnover event may be triggered by the dramatic relative sea-level fall during the mid-Carboniferous, and continued low relative sea level in South China and global flourish of phylloid and red algae during Pennsylvanian times. Grainstone and dolomitic limestone were the main composition of the platform sedimentary facies in South China during Pennsylvanian times. In addition, global climate cooling and warming, resulted from the waxing and waning of Gondwana glaciation, may also influence the reef evolution in South China, as evidenced from the consistent transgression and regression events and reef evolutionary pattern between South China and globe during the Carboniferous.

Evidence of Anoxic Oceans at in the Lopingian Permian South China

Lopingian (Upper Permian) trace fossils from the northern Penglaitan Section, Laibin, Guangxi, South China and their environmental implications

Authors:

Ding et al

Abstract:

The end-Permian mass extinction has been widely documented to be accompanied with oceanic anoxia, which was considered as one of the most plausible killing mechanisms. However, it is still unclear when anoxia began to occur and how widely affected during the pre-extinction interval. In this study, Lopingian bottom-water oxygen level changes around the Wuchiapingian–Changhsingian boundary (WCB) at the northern Penglaitan section in Guangxi are analysed based on trace fossil assemblages and ichnofabric indices. Detailed bed-by-bed ichnological analyses confirm the presence of trace fossils Chondrites intricatus, C. isp., Palaeophycus isp., Planolites isp. A, P. isp. B, Thalassinoides isp. A, T. isp. B, Trichichnus linearis, Zoophycos isp., and other bioturbational structures. The ichnofabric indices around the WCB are mostly 1-2, but rapidly increase to 4-5 in some short intervals. The distinct fluctuations of ichnofabric indices suggest that the oxygen level of sediments was generally deficient, but the dysoxic or anoxic periods were punctuated by several short oxic intervals. Thus, it can be inferred that the benthic organisms were under secularly environmental stresses around the WCB at the northern Penglaitan section. The anoxic conditions unfavourable for aerobiosis in the deep basin may start in the late Wuchiapingian. However, more sections need to be studied to determine whether this is a local or regional phenomenon.

Norian/Rhaetian Triassic Sichuan Basin, China had two Warm, Humid and two Cooler, Drier PaleoClimate Events

Late Triassic palynofloras in the Sichuan Basin, South China: Synthesis and perspective

Authors:

Li et al

Abstract:

Mesozoic strata are well developed and exposed continuously across the Sichuan Basin, South China. In particular, the Upper Triassic strata yield diverse and abundant spore-pollen fossils, providing a significant reference for the study of palaeoenvironmental variations across the Triassic–Jurassic transition where mass extinctions were occurring. In this paper, we summarize the major progress on Late Triassic palynological studies in this basin. To date, 151 genera (454 species) of sporomorph fossils have been reported from the Late Triassic strata in the Sichuan Basin. Three palynological assemblages are distinguished for the Late Triassic in the Sichuan Basin. Late Triassic vegetation in the Sichuan Basin shows a remarkable predominance of ferns, followed by conifers and cycads/ginkgophytes, and conifers show a distinct increase in abundance in the latest Triassic. In general, the Late Triassic palaeoclimate in the Sichuan Basin was tropical-subtropical, humid and warm. A synthesis of the data shows that the Late Triassic did not have a constant paleoclimate in the Sichuan Basin, several climatic events are recognized: two warm and humid climate events in Norian-Rhaetian time, coupled with a cooler and drier condition in the latest Late Triassic. Further investigations in higher resolution at more continuous sections in the Sichuan Basin are needed to better understand the Late Triassic vegetation response, climate changes, as well as palaeoecosystem variations across the Triassic–Jurassic boundary.

This Base is FULLY OPERTIONAL! Chinese Complete Airfield on Reclaimed Fiery Cross Reef

China has completed a 10,000 foot runway on a reclaimed island in the South China Sea, according to a new round of satellite photos released Friday.

The completed runway on Fiery Cross Reef could soon be operational and accelerate additional construction on the reclaimed island, according to a Friday report in Jane’s Defence Weekly.

The island in the Spratly chain is in a central location in the South China Sea about 400 miles from Vietnam, Malaysia and the Philippines and a likely key component of the China’s South China Sea strategy.

link.

Sea Water Chemistry Changes in the Shallow Water Ediacaran NeoProterozoic Ocean

Secular changes of water chemistry in shallow-water Ediacaran ocean: Evidence from carbonates at Xiaofenghe, Three Gorges area, Yangtze Platform, South China

Authors:

Hohl et al

Abstract:

Ediacaran carbonates from the shallow-water section near Xiaofenghe (Three Gorges area, Hubei Province) on the Yangtze Platform, South China have been studied to understand post Marinoan changes in seawater chemistry. Major and trace element abundances and Sr-Nd isotopic compositions were obtained on acetic acid leachates of carbonate sediments from both the Doushantuo Formation (Members D1-D4) and the overlying Dengying Formation. C and O isotopic compositions of these samples were analysed using the phosphoric acid method. With the exception of the D1 cap carbonates (87Sr/86Sr = 0.7088 to 0.713), most samples show low Mn/Sr and 87Sr/86Sr (0.7078 in D2-D4 and 0.709 in the Dengying Formation) similar to seawater values inferred from Ediacaran carbonates elsewhere. These data, together with the absence of a correlation between 87Sr/86Sr and δ18Ocarb, indicate minor diagenetic fluid overprinting. The initial ɛNd values of the carbonate leachates show a limited variation range from -4.3 to -7.5 with the highest values in D1. These data overlap with published data for Doushantuo sediments in South China, and possibly indicate an isotopically homogenous Nd source in the source area during most of the Ediacaran. D1 samples of cap carbonates display negative δ13Ccarb values of -2.0 to -3.6 (VPDB) and δ18Ocarb values ranging from -6.5 to -7.3 (VPDB), whereas the overlying D2 strata show positive δ13Ccarb values around 6. Carbonate rocks from D3 and D4 show a large variation of δ13Ccarb from -1.4 to 9.4, with some samples having unusually high δ13Ccarb values coupled to low TOC contents. Most carbonate leachates at the base of the Doushantuo display superchondritic Y/Ho and variable HREE enrichment (Pr/Yb less than 1), similar to modern seawater. This suggests a similar seawater chemistry as under modern open ocean conditions at the beginning of the Ediacaran, whereas lower Y/Ho in D3 correlate with flat REE + Y patterns, indicating a change to variable freshwater-seawater mixing and suppression of HREE/LREE fractionation as in modern estuaries. Carbonate rock samples from D4 are rich in clay minerals (up to 15%), of possible authigenic origin, such as nontronite and saponite. Formation of these clay minerals may only be possibly under extreme alkaline and saline conditions. The D4 carbonate leachates show the highest Y/Ho and lowest Ce/Ce* values and have unusually high δ 13Ccarb values, which may also support the conditions of extreme shallowing and perhaps temporarily restricted basins that led to a rise in salinity due to high evaporation rates. Ce anomalies in carbonate leachates show strong variation throughout the profile. A secular increase of seawater oxygenation through the Ediacaran is not obvious. However the most pronounced Ce anomalies can be found in the upper Doushantuo (Ce/Ce* as low as 0.64).

Trace Fossils From Smithian/Spathian Triassic South China Suggest Gradual Biotic Recovery From PT Extinction

Early Triassic trace fossils from the Three Gorges area of South China: Implications for the recovery of benthic ecosystems following the Permian–Triassic extinction

Authors:

Zhao et al

Abstract:

The Lower Triassic Daye and Jialingjiang formations of the Three Gorges area (South China) record the recovery interval of benthic tracemaking invertebrates following the P–Tr mass extinction. A total of 17 ichnospecies in 14 ichnogenera are documented from Smithian and Spathian strata. Our trace fossil data, in combination with previously published studies, show that ichnodiversity in the Middle Yangtze region increased markedly in the early Spathian. Trace fossils in the Smithian are dominated by simple, small, horizontal burrows, including Didymaulichnus and Planolites, whereas Spathian trace fossils are diverse and abundant with moderate–high bioturbation levels and complex burrow networks, such as Thalassinoides. Both burrow sizes and penetration depths increased gradually from the early Spathian to the middle–late Spathian, implying a gradual recovery pattern for benthic ecosystems. Early Triassic ichnofossils are characterised by aspects of opportunistic behaviour (e.g., low-to-moderate ichnodiversity, low-to-moderate bioturbation, small burrow widths, and shallow tiering), suggesting stressed environmental conditions. The recovery tempo and pattern of ichnocoenoses in South China is likely structured by temporal and spatial changes of the refuge zone in the Early Triassic.

Evidence of the Smithian/Spathian Triassic Extinction From South China

High amplitude redox changes in the late Early Triassic of South China and the Smithian–Spathian extinction

Authors:

Sun et al

Abstract:

The Early Triassic was a time of remarkably high temperatures, large carbon cycle perturbations and episodes of widespread ocean anoxia. The sediments in the Nanpanjiang Basin of South China provide superb opportunities to examine the sedimentary response to these extreme conditions especially during the crisis interval at the Smithian–Spathian (S-S) boundary. We have investigated a deep water section at Jiarong and a shallower water section at Mingtang. These contain a range of facies including black shales, micritic limestone units and rudaceous carbonate event beds that include flat pebble conglomerates and breccia debrites that bear similarities to the hybrid event beds seen in clastic turbidite successions.

Redox proxies (pyrite framboids and trace metals) reveal that widespread anoxia in the late Smithian persisted into the Novispathodus pingdingshanensis Zone of the early Spathian before a sharp transition to highly oxygenated “griotte facies” (red marine strata) in the Icriospathodus collinsoni Zone that records an “oxic rebound”. Benthic faunas are locally common but of low diversity and dominated by thin-shelled bivalves and ostracodes with small foraminifers and exceptionally rare fish remains. Bioturbation was intense only in the early–middle Spathian (I. collinsoni conodont zone) Griotte facies. Anoxia and extremely high temperatures probably played a role in severely restricting the abundance of fish and the small sizes of marine invertebrates at this time. The presence of ooids and seafloor fan cements in our study sections indicates highly saturated conditions rather than acidification at the end of the Smithian.

Vetulicola: a Road not Taken From the Cambrian Explosion

New observations on morphological variation of genus Vetulicola with quadrate carapace from the Cambrian Chengjiang and Guanshan biotas, South China

Authors:

Li et al

Abstract:

Vetulicolians are enigmatic fossils with a debated phylogenetic position; they first appeared during the Cambrian evolutionary explosion. The early Cambrian Chengjiang and Guanshan biotas from South China exhibit the highest taxonomic diversity of vetulicolians, with ten species described to date. Here we conduct a comparative study on the most common members of Genus Vetulicola that bear a quadrate carapace from these two biotas. Two morphotypes are recognized both within Vetulicola rectangulata from the Chengjiang Biota and within a new undetermined species, Vetulicola sp. from the Guanshan Biota. In both localities morphotypes differ from each other in the presence/absence of a posteroventral projection in the anterior body, and this is interpreted to possibly represent sexual dimorphism. These two Vetulicola species from the Chengjiang and Guanshan biotas also exhibit other morphological differences. Most notable is the position of the junction between the anterior and posterior parts of the body which is further towards the anterior in the specimens from the Guanshan Biota than those from the Chengjiang Biota. In addition, the expansion of the distal portion of the posterior body occurs from the third segment in the Chengjiang specimens but from the fourth segment in the Guanshan specimens. The most likely interpretation of these differences is that they reflect evolutionary adaption of the swimming ability of Vetulicola with a quadrate carapace from the Chengjiang to the Guanshan Biota.

Evidence of the Local Carbon Cycle From Devonian-Carboniferous Boundary in South China

Local overprints on the global carbonate δ13C signal in Devonian–Carboniferous boundary successions of South China

Authors:

Qie et al

Abstract:

An integrated study of the litho-, bio-, and chemostratigraphy of the Devonian–Carboniferous boundary at four sections (Qilinzhai, Malanbian, Gedongguan and Long'an) in South China was undertaken in order to better understand paleoenvironmental changes and controls on δ13Ccarb variation during the Hangenberg Crisis. Sedimentological data record a major regression in the Middle Siphonodella praesulcata Zone, which coincided with the Hangenberg Extinction (HE) in South China. Our new δ13Ccarb data document a negative δ13Ccarb shift near the base of the Middle S. praesulcata Zone, which may have been related to the HE. Prior to and during the HE, respiration of organic matter contributed abundant 12C-enriched dissolved inorganic carbon (DIC) to the restricted Nanning carbonate platform, resulting in a negative vertical δ13CDIC gradient in the study area. In the Upper S. praesulcata Zone, all four sections exhibit a positive δ13Ccarb shift, suggesting that a vigorous biological pump existed in the aftermath of the latest Devonian glaciation. However, peak δ13Ccarb values differ markedly among the study sections, suggesting that local carbon cycling processes played an important role during the initial post-glacial transgression.

Ediacaran–Silurian Nanhua Foreland Basin From South China

Detrital provenance evolution of the Ediacaran–Silurian Nanhua foreland basin, South China

Authors:

Yao et al

Abstract:

We report here in-situ U–Pb and Hf isotopic results of detrital zircons from sixteen Cambrian–Silurian siliciclastic samples across the Nanhua foreland basin, South China. Together with published data from Ediacaran–Silurian sandstones in the region, we establish the temporal and spatial provenance evolution across the basin. Except for samples from northeast Yangtze, all other Ediacaran–Silurian samples exhibit a prominent population of 1100–900 Ma, moderate populations of 850–700 Ma and 650–490 Ma, and minor populations of 2500 Ma and 2000–1300 Ma, grossly matching that of crystalline and sedimentary rocks in northern India. Zircon Hf isotopes further reveal four episodes of juvenile crustal growth at 2.5 Ga, 1.8 Ga, 1.4 Ga and 1.0 Ga in the source regions. Utilizing the basin history and late Neoproterozoic to early Paleozoic paleogeography of South China, we conclude that the Ediacaran–Cambrian sediments in the Nanhua foreland basin were mainly sourced from northern India and adjacent orogens, and the Ordovician–Silurian sediments were derived from both locally recycled Ediacaran–Cambrian rocks and eroded Cathaysian basement. The Wuyi–Yunkai late-orogenic magmatic rocks also contributed to the Silurian sediments in the basin. The upper-Ordovician to Silurian samples in northeast Yangtze received higher proportions of local Cryogenian (850–700 Ma) magmatic rocks which were uplifted during late-Ordovician to Silurian time. We speculate that there was an Ediacaran–Cambrian collisional orogen between South China and northern India, shedding sediments to the early Nanhua foreland basin. Far-field stress during the late stage of this collisional orogeny triggered the Ordovician–Silurian intraplate Wuyi–Yunkai orogeny in South China, and erosion of the local Wuyi–Yunkai orogen further provided detritus to the late Nanhua foreland basin.

The PaleoEnvironment and Palaeoecosystem of the Ediacaran NeoProterozoic Sibanatan Member

Geobiology of a palaeoecosystem with Ediacara-type fossils: The Shibantan Member (Dengying Formation, South China)

Authors:

Duda et al

Abstract:

Despite the importance of palaeoecosystems with Ediacara-type fossils for the early evolution of metazoans, only little is known about the interplay of geological and biological processes in these environments. The reason is that sedimentary structures, biogenic structures and (bio-) geochemical signatures (e.g. hydrocarbon biomarkers) are commonly not well preserved due to the predominance of volcanic and siliciclastic lithologies. The Shibantan Member (Dengying Formation, South China) is one of only few carbonate settings with Ediacara-type organisms worldwide and its lithology promises an excellent preservation of sedimentary facies and (bio-) geochemical signatures. Here we provide the first comprehensive geobiological characterisation of the Shibantan Member in order to reconstruct the interplay between sedimentary and (bio-) geochemical processes and to assess the microbial activities in the palaeoecosystem with Ediacara-type fossils. Facies analyses revealed that carbonate and organic matter were autochthonously formed by (bio-) geochemical processes linked to microbial mats. However, the material was frequently reworked and re-deposited within the same setting (i.e. para-autochthonous) as evidenced by small-scale (hummocky-) cross stratification, erosional contacts, lenticular bedding and load casts. Negative Ce anomalies (Ce/Ce*) and low V/Cr ratios demonstrate that molecular O2 was present in the water column, whereas characteristic Ni/Co-, V/(V + Ni), and V/Sc ratios suggest the contemporaneous presence of sub- to anoxic water. Taken together, these observations imply a temporarily stratified water body frequently mixed and ventilated by storms. 13C-enrichments in the Shibantan carbonates (δ13C = +3.29 to +3.98‰, VPDB) together with 13C-depletions of syngenetic n-alkanes cleaved from the extraction residue using catalytic hydropyrolysis (HyPy; δ13C = −31.7 to −36.3‰, VPDB) could indicate a significant withdrawal of 12C by primary producers that thrived within the mats. At the same time, sulphurised biomarkers in the bitumen and HyPy-pyrolysate hint at organic matter decomposition and concomitant sulphide production by sulphate reducing bacteria. When oxygen was available at the sediment–water interface due to mixing by storms, sulphide oxidising bacteria were possibly temporarily favoured. The results demonstrated that palaeoenvironmental conditions dynamically changed through a complex interplay of biogenic and abiogenic processes.

Evidence of Ediacaran NeoProterozoic Sponges From China?

Potential Ediacaran Sponge Gemmules from the Yangtze Gorges area in South China

Authors:

Du et al

Abstract:

Sponges are widely viewed as the most primitive metazoans. Sponge gemmule-like structures have been recovered from the lower part of the Doushantuo Formation in the Yangtze Gorges area (South China), that was deposited between 635 to 580 Ma. Gemmoscleres-like structures are embedded in the outer coat of the sponge structures. Electron probe microanalyses EPMA) of the gemmoscleres-indicate that they have siliceous composition. The naked subspheroidal sponge structures are composed of three layers, consistent with the preservation of a tri-layered theca embedded with the gemmosclere-like structures. The potential fossils of the Ediacaran sponge gemmules in the Doushantuo Formation may provide one of the earliest records of sponges.

Cosmosperma polyloba: the First Seed Plant From Famennian Devonian South China

Cosmosperma polyloba gen. et sp. nov., a seed plant from the Upper Devonian of South China

Authors:

Wang et al

Abstract:

Seed plants with ovules were abundant in the Late Devonian of Euramerica and they contribute significantly to our understanding of their early history. However, coeval ovules have been scarce in other regions of the world. Specimens of the seed plant Cosmosperma polyloba gen. et sp. nov. Wang et al. were recently obtained from the Upper Devonian (Famennian) Wutong Formation, at Fanwan Village, Changxing County, Zhejiang Province, China. This new seed plant has cupulate ovules, the uniovulate cupules with up to 16 distal segments and with minute spines on the outer surface, synangiate pollen organs bearing six to eight microsporangia fused only at the base, and planate and highly dissected pinnules in alternate arrangement. It differs from other Devonian seed plants mainly in the organization and position of the uniovulate and ornamented cupule, and in the highly dissected pinnules. Cosmosperma Wang et al. represents the first Devonian ovules recovered from China or eastern Asia and further illustrates the diversity of early spermatophytes. As for the Late Devonian seed plants, it is suggested that the pollen organs are synangiate and simple in organization, and the branches and leaves are generally planate.

Paleoproterozoic Granites Found in Cathaysia Geological Block, Suggests Archean Basement

Origin and geological significance of Paleoproterozoic granites in the northeastern Cathaysia Block, South China

Authors:

Liu et al

Abstract:

New whole-rock major- and trace-element analyses, zircon U–Pb dating and Hf-isotope analyses on five granite bodies in southwestern Zhejiang Province define a significant Paleoproterozoic magmatic episode in the eastern Cathaysia Block.

Based on geochemical data from twenty-seven Paleoproterozoic granite samples, S-, I- and A-type granites have been recognized. A-type granites have low SiO2 (62.5–70.5%), and high contents of Fe2O3t (3.82–9.95%), CaO, P2O5, Ba, Ga, Zn, Y, high-field-strength elements (HFSE, e.g. Zr, Hf, Nb and Ta) and rare-earth elements (REE), with high FeOt/(MgO + FeOt) (0.78–0.89) and Ga/Al (>3.1) ratios. In contrast, the S-type granites share slightly high SiO2 (65.9–74.1%) contents and low Fe2O3t, HFSE and REE contents with high A/CNK (1.04–1.37) and low Al2O3/TiO2 ratios. I-type granites were recognized for the first time in this study area. They are characterized by low A/CNK (0.94–1.07, a mean of 1.01), Rb/Ba (0.17–0.33) and Rb/Sr (0.48–1.14, a mean of 0.87) ratios, low contents of TiO2, Ga, Zn, HFSE, high Na/K ratios and high CaO contents.

LA-ICPMS U–Pb dating of zircons shows a progression from I-type granites (Chimushan and Xiaocu plutons) formed at ∼1912 Ma and ∼1887 Ma, to S-type granites (Chimushan, Xiaocu and Wengkeng plutons) at ∼1884 Ma, ∼1882 Ma and ∼1876 Ma, and then to A-type granites (Huaqiao, Xiaocu and Chimushan plutons) at ∼1878 Ma, ∼1869 Ma and ∼1859 Ma. These Paleoproterozoic granites suffered at least two episodes of metamorphism in early Mesozoic (250–230 Ma) and late Mesozoic (110–90 Ma) time. The integration of previously available ages and geochemical data with this study indicates that Paleoproterozoic I-type and S-type granites (1912–1875 Ma) were generated before the A-type granites (1878–1832 Ma). The S- and I-type granites have low formation temperatures of 725–840 °C and were probably formed in an early post-collisional tectonic setting, whereas the A-type granites have high crystallization temperatures (840–920 °C) and formed in the later post-collisional extensional setting. Since 1782–1766 Ma mafic rocks also occur in the area, it is suggested that a complete late Paleoproterozoic orogeny from syn-collisional to post-collisional and final anorogenic tectonic settings occurred in the northeastern Cathaysia Block from >1912 Ma to 1766 Ma, lasting about 150 Myr. This in turn suggests that the Cathaysia Block was once a part of the Paleoproterozoic Columbia supercontinent.

The S- and A-type granites share similar zircon Hf-isotope compositions with an average ɛ Hf(t ) value of ca. −4.19 and two-stage Hf-isotope model ages (View the MathML sourceTDMC) of 2.78 Ga, suggesting sources similar to those of the Badu Complex. Geochemical and isotopic compositions suggest that the Xiaocu I-type granites originated from meta-felsic igneous rocks, whereas the Chimushan I-type granites crystallized from mixed magmas derived from both old meta-sedimentary and juvenile meta-mafic rocks. The complex types and compositions of the Paleoproterozoic granites in the study area suggest that the lower crust in the northeastern Cathaysia Block was quite heterogeneous. The discovery of Paleoproterozoic I-type granites, coupled with the ∼2.8 Ga model ages and inherited zircons in these granites, demonstrates the existence of Archean basement rocks in the Cathaysia Block.

Evolution of the South China Craton in the NeoProterozoic

Neoproterozoic arc-trench system and breakup of the South China Craton: Constraints from N-MORB type and arc-related mafic rocks, and anorogenic granite in the Jiangnan orogenic belt

Authors:

Yao et al

Abstract:

The early Neoproterozoic Jiangnan orogenic belt, located in the southeastern margin of the Yangtze Block, is considered to mark the suture zone between the Yangtze and Cathaysia Blocks. The eastern part of this belt consists of the Huaiyu and Jiuling terranes, separated by the NE Jiangxi fault zone which represents the back-arc marginal sea. The western part of the Jiangnan orogenic belt is characterized by the Jiangnan arc and back-arc sea. Neoproterozoic mafic–ultramafic rock suites are exposed along both the Jiangshan-Shaoxing-Pingxiang-Shuangpai and the NE Jiangxi suture zones, whereas I-, S- and A-type granites occur widely in the Jiangnan region. Here, we present new LA–ICP–MS zircon U–Pb data, Hf isotopes and whole rock geochemistry for the mafic rocks and granite from the Jiangnan orogenic belt. The N-MORB (normal mid-ocean ridge basalts) type basalts from the Nanqiao of Liuyang area in the west Jiangnan orogenic belt show low K2O contents (0.74–0.16 wt.%), belonging to tholeiitic series, and display LREE (light rare earth element) depleted REE (rare earth element) patterns, with positive Pb, Sr anomaly and minor negative Ti anomalies. The other mafic suites in the Daolinshan, Yiyang and Liuyang areas exposed in the eastern and western segments of the Jiangnan orogenic belt show distinctive geochemical signatures of volcanic arc, with zircon U–Pb ages of 863 ± 6 Ma. Most of these rocks show negative Nb, Ta, Zr, Hf and Sr anomalies and have LREE enriched REE patterns, with minor negative Eu anomaly. These features coincide with those of the arc and fore-arc rock assemblages in the eastern Huaiyu Terrane and adjacent areas. Anorogenic granites of 790 ± 5 Ma are also found in the Daolinshang area. Our Hf isotopic data further reveal that the zircons from both the dolerite and A-type granite in the Daolinshan area possess positive ɛHf(t) values, yielding latest Mesoproterozoic to early Neoproterozoic model ages. Combined with previous studies, our data confirm the existence of an arc-trench system in the Jiangnan orogenic belt at ca. 863 Ma. Therefore, we infer that the amalgamation of the Yangtze and Cathaysia Blocks in the eastern part occurred at some time after ca. 863 Ma. This was followed by breakup at ca. 790 Ma which was triggered by mantle upwelling, as evidenced by the Daolinshan A-type granite with positive ɛHf(t) values

Qianzhousaurus: a Long Snouted Tyrannosaur From Maastrichtian (?) Cretaceous China

Scientists have discovered a new species of long-snouted tyrannosaur, nicknamed Pinocchio rex, which stalked the Earth more than 66 million years ago.

Researchers say the animal, which belonged to the same dinosaur family as Tyrannosaurus rex, was a fearsome carnivore that lived in Asia during the late Cretaceous period.

The newly found ancient predator looked very different from most other tyrannosaurs. It had an elongated skull and long, narrow teeth compared with the deeper, more powerful jaws and thick teeth of a conventional T. rex.

Palaeontologists were uncertain of the existence of long-snouted tyrannosaurs until the remains of the dinosaur – named Qianzhousaurus sinensis – were unearthed in southern China.

Until now, only two fossilised tyrannosaurs with elongated heads had been found, both of which were juveniles. It was unclear whether these were a new class of dinosaur or if they were at an early growth stage, and might have gone on to develop deeper, more robust skulls.

The new specimen, described by scientists from the Chinese Academy of Geological Sciences and the University of Edinburgh, is of an animal nearing adulthood. It was found largely intact and remarkably well preserved, thereby confirming the existence of tyrannosaur species with long snouts.

Experts say Qianzhousaurus sinensis lived alongside deep-snouted tyrannosaurs but would not have been in direct competition with them, as they were larger and probably hunted different prey.

Following the find, researchers have created a new branch of the tyrannosaur family for specimens with very long snouts, and they expect more dinosaurs to be added to the group as excavations in Asia continue to identify new species.

Qianzhousaurus sinensis lived until around 66 million years ago when all of the dinosaurs became extinct, likely as the result of a deadly asteroid impact.

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An Ediacaran-like Disc Shaped Fossil From Cambrian China

Affinities and Taphonomy of a Cambrian Discoid from Guizhou, South China

Authors:

Yang et al

Abstract:

Disc-like fossils from siltstones of the Taozichong Formation (Cambrian) in the Qingzhen area, Guizhou, South China are reported here. They are similar to some Ediacaran and Phanerozoic discoidal fossils, and assigned to Tirasiana? disciformis? Palij, 1976. Based on the study of 43 specimens, dewatering or fluid escape structures, soft-sediment loading, scratch circles or other inorganic origins are ruled out, and the fossil is interpreted as a discoidal body fossil of unknown affinities rather than trace fossils. Energy-dispersive X-ray spectroscopy and elemental mapping analyses reveal that the discoid fossils contain higher concentrations of C, Fe, and P than the surrounding matrix, indicating the possible presence of pyrite, apatite, and organic carbon as a result of authigenic mineralization in association with decay and early diagenetic processes. The possible presence of extracellular polymeric substance suggests that the discs were surrounded by thin microbial mats composed primarily of extracellular polymeric substances, which facilitated their fossilization by promoting conditions that are favorable to secondary mineral precipitation. The new specimens provide useful information about the phylogenetic affinities of these early discoidal fossils and help us to better understand the taphonomic modes of non-biomineralizing organisms in Ediacara-type and Burgess Shale-type biotas.

Possible Animal Embryos From Lower Cambrian China

Possible Animal Embryos from the Lower Cambrian (Stage 3) Shuijingtuo Formation, Hubei Province, South China

Authors:

Broce et al

Abstract:

Fossilized animal embryos from lower Cambrian rocks provide a rare opportunity to study the ontogeny and developmental biology of early animals during the Cambrian explosion. This paper reports possible animal embryos, along with sponge spicules, hyolithelminths, and linguliformean brachiopods, from the upper Shuijingtuo Formation limestone (Cambrian Stage 3) at Changyang, Hubei Province, South China. This limestone unit has carbonate carbon and oxygen isotopic compositions similar to the upper Shuijingtuo limestone in the Yangtze Gorges area. The Shuijingtuo embryo fossils were exposed by physical fracturing, extracted with acetic acid maceration, and observed in thin sections. They were examined using light microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopic elemental mapping, and micro-focus X-ray computed tomography. Most of them are poorly preserved, with a phosphatic envelope (interpreted as a chorion or fertilization envelope) surrounding sparitic calcite. In some specimens, a polygonal pattern is present on the surface, and these are interpreted as multicelled blastula embryos. In others, sets of grooves are present on the surface of a calcitic spheroidal structure, presumably representing the calcitic interior within the chorion; these grooves are superficially similar to annulations of Markuelia embryos, but their biological significance is unknown. Although their phylogenetic and taxonomic placement is largely unconstrained, the Shuijingtuo animal embryos indicate that chorions are taphonomically more robust and are selectively phosphatized. Embryos within the chorions, on the other hand, can be completely lost or entirely replaced by calcite, with only poorly preserved surficial structures. This style of preservation can be explained by a taphonomic switch from early phosphatization to later calcitization. This study illustrates the importance of combining physical fracturing with widely used acid digestion methods in the study of calcitized animal embryos, and it alludes to the possibility that many empty phosphatic vesicles recovered by acid digestion from Cambrian carbonates may be fossilized chorions.