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Abstract: The Pennsylvanian and Early Permian were times of extreme sea-level changes of >100 to perhaps up to 200m. For example, glacio-eustatic sea-level changes are well documented from the US Midcontinent, Moscow Basin and Yangtze Platform, where more than 100 stacked subtidal to supratidal sequences have been described. In contrast, carbonates developed in the Ural Mountains and South Guizhou of the Yangtze Platform were deposited in ramp and slope settings. δ13C values of whole rock samples from the US Midcontinent and Moscow Basin were intensively affected by diagenesis. Only well-preserved brachiopod shells maintained their original carbon isotope ratios. In contrast, limestones deposited in the deeper water slope environments were not affected by meteoric diagenesis and are interpreted to have mainly retained their carbon isotope ratios. Mean δ13C values of slope carbonates of the Yangtze Platform increase from about 3‰ during the Viséan and Serpukhovian to 5‰ at the Carboniferous–Permian boundary and decrease to values around 2‰ in the early Kungurian. This positive δ13C excursion coincides with low δ13C values in the Yangtze Platform successions, which were reset by meteoric diagenesis. The highest δ13C values recorded in the slope succession coincide with the inferred maximum glaciation that caused pronounced sea-level lowstands. Short-lived, but significant negative δ13C excursions in the Chinese slope succession are interpreted to reflect changes in ocean circulation due to sea-level rises which caused enhanced production and/or preservation of organic matter which influenced the subsequent early diagenetic cementation. [Copyright &y& Elsevier]

Abstract: The Neoproterozoic Quanji Group in the Chaidam Basin, northwest China, consists of, in ascending order, the Mahuanggou, Kubaimu, Shiyingliang, Hongzaoshan, Heitupo, Hongtiegou, and Zhoujieshan formations. It is a siliciclastic-dominated sequence with only two carbonate units, the ∼300-m-thick Hongzaoshan dolostone and the ∼4-m-thick Zhoujieshan cap dolostone, the latter of which lies above the Hongtiegou glacial diamictite. In this study, we analyzed the δ13C and δ18O of the Hongzaoshan dolostone and Zhoujieshan cap dolostone, and the δ34SCAS, δ34Spy, and trace element compositions (Fe, Mn, Sr, and S) of the Zhoujieshan cap dolostone. δ13C profile of the Hongzaoshan dolostone shows a shift from −5‰ to 0‰. This shift could be correlated with a similar shift in the Shuiquan Formation (<615±6Ma) in the Quruqtagh area of the Tarim Block (NW China), and may be equivalent to negative δ13C excursions in the middle or uppermost Doushantuo Formation, the latter of which is widely believed to be correlative with the Shuram negative δ13C excursion. This correlation, together with available paleontological evidence (fragments of Redkinia from the Heitupo Formation, a genus that also occurs in ∼555Ma successions in the East European Platform), suggests that the Hongtiegou diamictite may represent an Ediacaran glaciation postdating the Gaskiers glaciation or occurring near the Precambrian–Cambrian boundary. The Zhoujieshan cap dolostone is characterized by positive δ13C values ranging from 0‰ to +1.7‰, in sharp contrast to cap carbonates overlying the Sturtian and Marinoan diamictites. δ34SCAS of the Zhoujieshan cap dolostone varies strongly between +13.9‰ and +24.1‰, probably due to relatively low-sulfate concentration in seawater. δ34Spy values, however, show a steady increase from +12.9‰ to +26.4‰. Thus, δ34SCAS and δ34Spy trends are decoupled in the Zhoujieshan cap dolostone, and the high δ34Spy values in the upper part of the cap dolostone indicate inverse sulfur isotope fractionations (δ34SCAS <δ34Spy). The decoupling of δ34SCAS and δ34Spy suggests that CAS and pyrite were derived from different sulfur pools (a possible scenario if the post-glacial Oulongbluq basin was restricted and stratified) and/or that aerobic oxidation of sulfide was intense in the post-glacial Oulongbluq basin. [Copyright &y& Elsevier]

Abstract: Glacial deposits are present at the head of the Ürümqi River valley, Tianshan, Central Asia. 10Be surface exposure ages of 15 boulders from three sites along a 12 km valley transect range from 9 to 21 ka suggesting emplacement by glacial retreat and advance commencing at the global last glacial maximum (LGM) and most likely abating in the early Holocene. Although the age spread for a given locality is not small, perhaps indicating post-depositional reworking, maximum ages per site are either coeval with or are post-LGM and inconsistent with previous pre-LGM electron spin resonance ages. [Copyright &y& Elsevier]

Abstract: The organic carbon isotope data through the unweathered Ordovician–Silurian boundary strata at the Wangjiawan Riverside section, which is c. 180 m southeast of the Wangjiawan North section, the GSSP for the base of the Hirnantian Stage (Upper Ordovician), show that a positive δ 13Corg excursion begins just below the base of the Hirnantian Stage and peaks in the lower part of the N. extraordinarius Biozone. This is followed by an interval of slightly reduced δ 13C values and a second peak of 2‰ above pre-Hirnantian values, which occurs in the lower part of the N. persculptus Biozone (upper Hirnantian). The peaks in δ 13Corg values can be correlated well with episodes of glacial expansion described from Africa and peri-Gondwanan Europe. Evidence from sedimentological, faunal, and geochemical data from South China, as well as the evidence of glacial sediments in North Africa, all suggests a short-lived glaciation of ~1 Ma in the Ordovician South Pole region, consisting of at least two major pulses. The first phase of gradual glacial expansion began just before the Hirnantian Epoch and the second phase ended with rapid melting in the late Hirnantian (early N. persculptus Biozone). [Copyright &y& Elsevier]

The Ordovician-Silurian (O/S) transition was a critical geological interval, during which significant biological events and dramatic environmental changes occurred. Extensive research has proven that changes in the ocean environment are one of the main causes of events that affect the biosphere. However, the redox structure and related geochemical evolution of the ocean during the O/S transition remain under debate. N isotopes are thought to have significant potential for further elucidating the oceanic redox structure and related geochemical evolution during the O/S transition, and are an effective supplement to the former environmental proxies of bottom sediments. This study presents high-resolution N isotope data from a well-sequenced drill core across the O/S transition from the Lower Yangtze Platform, South China, showing an interesting isotopic variation with high δ15N values (+1‰ to +4‰) during the Late Katian to Hirnantian ages of the Ordovician and much lower values (−1‰ to +1‰) during the Rhuddanian Age of the earliest Silurian. This δ15N variation is mostly controlled by ocean redox conditions and the corresponding changes in the nitrate reservoir. Combined with previously reported δ15N data, a redox-stratified ocean with a relatively deep redox transition zone was reconstructed according to the distribution of δ15N profiles across different palaeogeographic locations. The lower δ15N values and more reducing conditions in deep water sections demonstrate that glacio–eustatic fall, rather than increased upwelling, was likely the main driver of the global redox change during the Late Ordovician. Furthermore, a global δ15N decrease during the Late Katian may be associated with the debated Boda warm event, and the up to six positive δ15N excursions observed during the Hirnantian might suggest the cyclicity of the glaciation process. • δ15N can be correlated globally during the Ordovician-Silurian (O/S) transition. • Oceanic δ15N was controlled by water redox conditions during the O/S transition. • Positive δ15N excursions with a low δ15N baseline support a redox-stratified ocean. • δ15N records indicate Hirnantian redox evolution driven by eustatic sea-level fall. • Global δ15N variations correspond with a Boda warm event and multistage Hirnantian glaciation. [ABSTRACT FROM AUTHOR]

• Rapid sedimentation at a rate of ~0.55 m/ka occurred between ~39 and ~19 ka. • A sedimentary hiatus lasting from ~19 to ~3.6 ka was found at a depth of ~3 m. • Deposition resumed after ~3.6 ka and was dominated by sand rather than clay before. • Aggradation process since at least 74 ka was most likely driven by climate change. • High-As groundwater was possibly related to incised-valley or paleolake sediments. The Datong Basin in northern China is notorious for its geogenic arsenic (As)-polluted groundwater hosted by late Quaternary strata. Deciphering the mechanism of arsenic pollution requires an understanding of stratigraphic architecture and depositional processes, which, however, are hindered by weak chronological data. Here we utilized the optically stimulated luminescence (OSL) dating technique to obtain 15 sediment ages from the upper 20 m of core SY1 from the central basin. The dating results revealed a sedimentary hiatus covering the period of about 19–3.6 ka, which may arise from river downcutting induced by strengthened East Asian summer monsoon (EASM) and ameliorating vegetation. Ages of sediments below the hiatus demonstrated a high sedimentation rate of ~0.55 m/ka at ~39–19 ka, which might result from weakened EASM and suppressed vegetation. Above the hiatus, sedimentation resumed after 3.6 ka possibly as a result of declined strength of EASM and increasing human activities like deforestation. Overall, climate change is the most likely driving force of aggradational history recorded in core SY1 since at least 74 ka. The dating results indicate that high-As groundwater may be released from sediments accumulated within incised valleys that were sculpted at about 19–3.6 ka, or from paleolake (Nihewan)-related sediments deposited before the last glacial period. [ABSTRACT FROM AUTHOR]

The late Neoproterozoic (645–535 Ma) represents a key geological period, when a climate shift and revolutionary biological innovations occurred during the Precambrian–Cambrian transition. The Marinoan glaciation impacted the climate and chemical composition of the oceans, restraining the evolution of early life. To elucidate evolutionary processes during the Marinoan–Ediacaran transition, this study presents biomarker evidence (molecular fossils) from the Nantuo Formation and the lower part of the Doushantuo Formation at the Jiulongwan section, China. Our results reveal possible photosynthetic activity (n -C 17 + n -C 19 [algae] and pristane + phytane [photosynthesis]) during the Marinoan glaciation, followed by low productivity during the early period of cap dolostone precipitation, and recovery of photosynthetic organisms (n -C 17 + n -C 19 : from 0.00 to 0.96 μg/g TOC; pristane + phytane: from 0.00 to 3.6 μg/g TOC) or other bacteria (hopanes: from 0.00 to 0.07 ng/g TOC) during late cap carbonate deposition, with the expansion of eukaryotes (steranes/[hopanes + steranes]: from 0.0 to 0.6) after cap carbonate deposition in the early Ediacaran. [Display omitted] • Biomass related biomarkers from Snowball Earth to the aftermath were analyzed. • Photosynthetic activity occurred in the sea during the Marinoan Snowball Earth. • Barren of biota during a post-Marinoan cap carbonate precipitation period. • Recovery of bacteria started at the end of the cap carbonate precipitation period. • Recovery and dominance of eukaryotes followed the cap carbonate period. [ABSTRACT FROM AUTHOR]

C-isotope analysis of the carbonates in the Upper Neoproterozoic in Keping, Xinjiang indicates that the Qigebrak Formation and the Upper Sugaitbrak Formation mainly record positive C-isotope values, and a distinct positive excursion occurs in the lower part of the Qigebrak Formation. There are three negative excursions in the boundary between the Qigebrak Formation and the Cambrian, the uppermost and lowermost Upper Sugaitbrak Formation. These characters resemble those of the Upper Neoproterozoic in the Three-Gorge area, which suggests that the Upper Sugaitbrak Formation and Qigebrak Formation can be correlated with the middle and upper parts of the Doushantuo Formation and Dengying Formation, respectively. The negative excursion at the top of the Upper Sugaitbrak Formation corresponds to that at the top of the Doushantuo Formation, while the negative excursion at the bottom of the Sugaitbrak Formation can be correlated with that at the middle part of the Doushantuo Formation in the Three-Gorge area and that at the top of the Hangelchaok diamictites in the Quruqtagh area. [ABSTRACT FROM AUTHOR]

The most complete Neoproterozoic successions in south China contain three diamictite intervals in the Changan, Tiesiao, and Nantuo Formations. The youngest and most widespread Nantuo glacial deposit overlies the Datangpo Formation and underlies the fossilrich Donshantuo Formation. Previous authors have correlated the Nantuo diamictite to either Sturtian or Marinoan glacial deposits elsewhere. Here we report sedimentary and δ13C chemostratigraphic data of the Doushantuo cap dolostone, which overlies the Nantuo Formation. Facies-dependent variation in δ13C is interpreted as evidence for spatial heterogeneity in δ13C and/or temporal diachroneity in the initiation of cap carbonate sedimentation. Sedimentary and chemostratigraphic data are indicative of a Marinoan age for the Nantuo glaciation. This inference is supported by a new U-Pb zircon age of 663 ± 4 Ma from a tuffaceous bed in the Datangpo Formation. The new date and other isotopic ages from south China constrain the age of the Changan and Tiesiao glaciation(s) as between 761 ± 8 Ma and 663 ± 4 Ma, and the Nantuo glaciation as between 663 ± 4 Ma and 599 ± 4 Ma. [ABSTRACT FROM AUTHOR]

The Neoproterozoic Quruqtagh Group in eastern Chinese Tianshan consists of, in ascending order, the Bayisi, Zhaobishan, Altungol, Tereeken, Zhamoketi, Yukkengol, Shuiquan, and Hankalchough Formations. Diamictite units occur in the Bayisi–Altungol, Tereeken, and Hankalchough Formations. Our field observations confirm the glacial origin of the Tereeken and Hankalchough diamictites, but the glacial origin of diamictites in the Bayisi and Altungol Formations remain ambiguous. While siliciclastic strata dominate the succession, carbonate units are recognized between the diamictites and immediately atop the Tereeken and Hankalchough diamictites. Carbonates in the Altungol Formation are characterized by highly positive δ13C values (up to +10.4‰ versus PDB), comparable to those of pre-Marinoan but post-Sturtian carbonates. High-resolution sampling of the pinkish cap dolostone (ca. 10 m-thick) overlying the Tereeken diamictite shows a consistent δ13C chemostratigraphic pattern (ca. −5‰ at the base and slightly decreasing upsection) similar to that of Marinoan cap carbonates. This cap dolostone is also characterized by macropeloids similar to those in the Marinoan-age Raventhroat cap carbonate, Mackenzie Mountains. Chemostratigraphic and sedimentary features are suggestive of a Marinoan age for the Tereeken glaciation. Thus, the younger Hankalchough diamictite may represent a post-Marinoan glaciation. This interpretation is consistent with the occurrence of vendotaenid fossils in the Shuiquan Formation. The alternative interpretation—the Tereeken and Hankalchough diamictites are, respectively, Sturtian and Marinoan in age—is not consistent with the above evidence or the chemostratigraphic features of the Shuiquan Formation and the Hankalchough cap carbonate. A post-Marinoan age for the Hankalchough and other glaciogenic deposits indicates that the disappearance of Doushantuo-type acritarchs and the subsequent radiation of macroscopic animals are closely linked, in geochronological terms, with a Neoproterozoic glaciation. [Copyright &y& Elsevier]

Extensive ice cover on the Tibetan Plateau would significantly influence Earth’s climate in general and the Asian monsoon system in particular, but extent and timing of Quaternary glaciations in Tibet remain highly controversial. We dated erratics on top of moraines in the climatic key areas of Central and East Tibet using cosmogenic 10Be, 26Al, and 21Ne. Consistent exposure ages obtained by various nuclides indicate a continuous period of exposure since the deposition of the samples. Our data imply that glacial advances were restricted to a few 10 km during the last 170 kyr in Central Tibet and during the peak of the last glaciation (∼24–13 kyr ago) in Eastern Tibet. Advances of Tibetan glaciers were much less prominent than elsewhere in the northern hemisphere most likely due to very arid conditions and high sublimation rates. A proposed ice-dome covering the entire Plateau can be excluded. Thus, albedo increase of Tibet most likely did trigger neither northern hemisphere ice ages nor paleomonsoon changes during the last two glacial cycles. The glacial advance during Marine Isotope Stage 2 in East Tibet and the absence of significant glacial events during the Holocene suggest a relation of snowline lowering in East Tibet to North Atlantic cooling events rather than to periods of high precipitation by an intensified monsoon. [Copyright &y& Elsevier]

Knowledge of interspecific divergence and population expansions/contractions of dominant forest trees in response to geological events and climatic oscillations is of major importance to understand their evolution and demography. However, the interspecific patterns of genetic differentiation and spatiotemporal population dynamics of three deciduous Cerris oak species (Q. acutissima, Q. variabilis and Q. chenii) that are widely distributed in China remain poorly understood. In this study, we genotyped 16 nuclear loci in 759 individuals sampled from 44 natural populations of these three sibling species to evaluate the plausible demographical scenarios of the closely related species. We also tested the hypothesis that macro- and microevolutionary processes of the three species had been triggered and molded by Miocene–Pliocene geological events and Quaternary climatic change. The Bayesian cluster analysis showed that Q. acutissima and Q. chenii were clustered in the same group, whereas Q. variabilis formed a different genetic cluster. An approximate Bayesian computation (ABC) analyses suggested that Q. variabilis and Q. acutissima diverged from their most common ancestor around 19.84 Ma, and subsequently Q. chenii diverged from Q. acutissima at about 9.6 Ma, which was significantly associated with the episodes of the Qinghai–Tibetan Plateau (QTP). In addition, ecological niche modeling and population history analysis showed that these three Cerris oak species repeatedly underwent considerable 'expansion–contraction' during the interglacial and glacial periods of the Pleistocene, although they have varying degrees of tolerance for the climatic change. Overall, these findings indicated geological and climatic changes during the Miocene–Pliocene and Pleistocene as causes of species divergence and range shifts of dominant tree species in the subtropical and warm temperature areas in China. [ABSTRACT FROM AUTHOR]

• The 2.32 to 2.29 Ga high-K granites did occur along the southern margin of the NCC. • The rocks might be recycling of metapsammite-dominated sources in an extensional setting. • Low and homogeneous δ18O values indicate the protolith likely underwent high- T hydrothermal alteration by surface water. • The coeval magmatism indicates no confluence of the Paleoproterozoic glaciations and magmatic gap. The interval of 2.45 to 2.20 Ga has previously been interpreted to contain a plate tectonic shutdown, but newly discovered magmatism of this stage is filling in the early Paleoproterozoic magmatic gap. However, the crust evolutionary scenarios and geodynamic driving mechanisms during this stage are still lacking comprehensive understanding. The present study verifies that the igneous rocks formed during this interval did occur along the southern margin of the NCC. The high-K granites in the Xiong'ershan area are dated at 2.32 to 2.29 Ga. Their low-δ18O values of zircons (-0.92 to + 4.78‰, 3.26‰ on average) are reported for the first time, representing the primary record of low-δ18O magma in the early Paleoproterozoic. The high-K granites show transitional features between S-type and normal A- and I-type granites. Zircon ε Hf (t) (-7.6 to + 1.5) and whole-rock ε Nd (t) values (-3.8 to + 1.1) with much older T DM2 (Hf T DM2 = 3.36 to 2.77 Ga and Nd T DM2 = 3.08 to 2.63 Ga, respectively) than their formation ages, together with heterogeneous major-element composition point to recycling of continental crust older than ca. 2.77 Ga. Low CaO/(FeOt + MgO), low to moderate Al 2 O 3 /TiO 2 (36.7 to 292), Rb/Sr (0.51 to 5.67) and Rb/Ba (0.04 to 1.09), variable but mostly high CaO/Na 2 O (0.05 to 5.17) ratios commonly imply metapsammite-dominated (meta -greywacke) sources with minor pelite-derived and tonalites materials. Considering that zircons lack metamict features and have low but positive and homogeneous δ18O values, we prefer a high-temperature hydrothermally altered older crustal source by surface water before or during partial melting. The great diversity of rock assemblages and geochemical features require a thermal anomaly linked to an extensional setting to account for the crustal melting. The occurrence of potassic rocks, and spatially associated gabbros, diorites and TTGs likely indicate no confluence of the Paleoproterozoic magmatic gap and glaciations during the 2.35 to 2.29 Ga at least in the southern NCC. [ABSTRACT FROM AUTHOR]

The extensive range of sand deserts, gravel deserts, and recent human activities have shaped habitat fragmentation of relict and endangered plants in arid northwestern China. Prunus mongolica is a relict and endangered shrub that is mainly distributed in the study area. In the present study, population genomics was integrated with a species distribution model (SDM) to investigate the spatial genetic diversity and structure of P. mongolica populations in response to habitat fragmentation and create a proposal for the conservation of this endangered species. The results showed that the northern marginal populations were the first isolated from other populations. The SDM suggested that these marginal populations had low levels of habitat suitability during the glacial period. They could not obtain migration corridors, and thus possessed low levels of gene flow connection with other populations. Additionally, several populations underwent secondarily geographical isolation from other central populations, which preserved particular genetic lineages. Genetic diversity was higher in southern populations than in northern ones. It was concluded that long-term geographical isolation after historical habitat fragmentation promoted the divergence of marginal populations and refugial populations along mountains from other populations. The southern populations could have persisted in their distribution ranges and harbored higher levels of genetic diversity than the northern populations, whose distribution ranges fluctuated in response to paleoclimatic changes. We propose that the marginal populations of P. mongolica should be well considered in conservation management. [ABSTRACT FROM AUTHOR]

[Display omitted] • Diverse sedimentary environments capture the evolution of Marinoan glaciation. • These Marinoan deposits record two complete, symmetrical sedimentary cycles. • Patterns of cyclic environmental changes are consistent with global-scale controls. • Marinoan glaciation gradually transited into the Ediacaran greenhouse. Cryogenian low-latitude glaciations mark the 'Snowball Earth' events and were thought to be dynamic on the basis of sedimentary features, especially glacial cycles. Although the glaciation dynamics and associated environmental changes can be investigated through the sedimentary records, there are sparse sedimentary studies. Studies from the Marinoan deposits in South China provide the basis for establishing a sequence stratigraphic framework that includes two complete glacial cycles across a basin-to-platform transect. Both cycles are characterized by symmetrical facies patterns, with a lower ice-advance succession and an upper ice-retreat succession. Each ice-advance succession consists primarily of a massive diamictite lithofacies association, and is dominated by proximal glaciomarine deposits. The gravel abundance and size of the deposits increase upward gradually, suggesting a progradational sequence. Each ice-retreat succession is composed of both a massive diamictite lithofacies association and a fine-grained lithofacies association, representing a mix of distal glaciomarine, proximal glaciomarine, and non-glacial marine deposits. The gravel abundance and size of these varied deposits decrease upward gradually, interpreted to reflect a retrogradational sequence. This sequence stratigraphic framework, interpreted to reflect gradual alternation from ice advance to ice retreat, indicates dynamic co-evolution of the sedimentary environments, paleoclimate, and sea level during the Marinoan glaciation. The glaciation dynamics, as they are reflected globally, highlight a gradual transition from the Marinoan glaciation to the Ediacaran greenhouse, and indicate a time lag between the onset of the deglaciation and the formation of the cap carbonates. [ABSTRACT FROM AUTHOR]

The latest Katian (Late Ordovician) is marked by the third biodiversity climax of the Great Ordovician Biodiversification Event (GOBE) prior to the Late Ordovician mass extinction (LOME). In this study, the Chemical Index of Alteration (CIA) is used to determine the paleoenvironmental change recorded in the Arisu Member, the Siltstone Member, and the Sandstone Member of the Terekawat (= Tierekeawati) Formation (upper Katian) in the Tarim Basin, northwestern China. CIA values from these members are plotted in A–CN–K ternary diagrams respectively. Linear regression and 95% confidence interval estimation results indicate that these deposits were derived from the same parent rock, and the corrected CIA (CIA corr.) values reveal significant paleo-climate changes during Late Ordovician. Sea-surface temperatures (SSTs) have been estimated by comparing 31 modern estuary systems. These data show that the CIA corr. values dropped from 77.41 to 64.83, corresponding to an interpreted temperature drop from 20.5 to 10.2 °C in the Dicellograptus complexus graptolite Biozone of the upper Katian (Ka-4). CIA corr. values varied within a range of 67.63–70.16, implying temperature fluctuations between 12.5 and 14.6 °C in the lower to middle Paraorthograptus pacificus Biozone. CIA corr. values rose again from 69.09 to 76.05, corresponding to a temperature rise from 13.7 to 19.4 °C in the upper Paraorthograptus pacificus graptolite Biozone of the latest Katian. This is interpreted to be a cooling and warming cycle, corresponding to the mid-Boda cooling and the late-Boda warming events. This study suggests that the climate change during late Katian was more intense than previous thought, especially in subtropical zones of Paleo-Tethys. This cooling event enhanced the thermohaline ocean circulation and became one of the major factors causing the well-known late Katian faunal dispersal (i.e. the Boda event). Hirnantian glaciation would have further promoted global oceanic cooling, over-stressed the ecosystems, and triggered the LOME. • Chemical Index of Alteration and confidence interval estimation are used to reconstruct climate change. • A temperature drop from 20.5 to 10.2°C and a subsequent rise are estimated in the Tarim Basin during the Late Ordovician. • This cooling event enhanced the thermohaline ocean circulation and contributed to the faunal dispersal (i.e. Boda event). • Hirnantian glaciation event doubled the cooling effect on ecosystem compared with this cycle. [ABSTRACT FROM AUTHOR]

Oceanic upwelling is an important process in ocean cycling and has implications for climate change and ocean productivity. During the Late Ordovician to early Silurian (O/S) transition, many dramatic geologic events occurred, including the Hirnantian Glaciation, enhanced organic matter accumulation, and upwelling events. Upwelling is thought to be closely linked to contemporary geologic events; however, the internal relationships and mechanisms involved remain poorly understood due to a reliance on qualitative evidence and low-resolution data. To better determine the presence and development of upwelling, as well as its underlying mechanisms and potential implications for environmental changes during the O/S transition, we report new evidence and insights based on data for South China. Detailed petrographic and geochemical analyses of a well-sequenced drill core from the Lower Yangtze region are presented and compared with other extensively examined sections from the Upper Yangtze region. We show that the excessive biogenic silica content associated with certain geochemical fingerprints (i.e., Cd/Mo, Co × Mn, and Co EF × Mn EF) offer compelling evidence for widespread upwelling in the Yangtze region during the O/S transition. This upwelling was strong during the late Katian to Hirnantian, significantly weaker during the early Rhuddanian, and was generally more intense in the relatively deep waters of the Yangtze region. The glacially-influenced temperature difference between the poles and equator, as well as longshore trade winds, may have been the drivers of this widespread upwelling. The upwelling event may have increased surface productivity, driving the accumulation of organic matter in the Wufeng Formation in South China. Moreover, the upwelling event can be regarded as a broad indicator of Late Ordovician glaciation and may be the geochemical basis for the Boda warm Event that occurred prior to Hirnantian cooling. [ABSTRACT FROM AUTHOR]

• We identified little plastome variation between two sympatric ecotypes of Phragmites australis. • An original analysis process was explored to estimate divergence time of P. australis. • Plastome phylogeny can objectively reflect the P. australis divergence. • Phylogenetic relationship of plastome seems not related to phenotypic differences in P. australis. • P. australis divergent events all occurred at the time of drastic paleoclimate changes. Phragmites australis , a Poaceae species distributed worldwide, has strong environmental adaptability and easily forms ecotypes. To study the process of ecotypic evolution of P. australis , we used two sympatric ecotypes with obvious phenotypic differences—Swamp Reed (SR) and Desert-dune Reed (DR) from the Hexi corridor of China as materials, and estimated divergence times derived from chloroplast genome sequencing. Their plastomes were very similar, with a sizes of 137,660 bp (SR) and 137,647 bp (DR). The results of multiple comparison methods revealed only 13 differences between them, most of which were in non-coding regions. A Poaceae chronogram was reconstructed from Bayesian inference using five fossil records. We optimized this analysis by exploring the input datasets, the fossil records, and the test model to get an estimated ecotypic divergence time of 73 Kya. Two main branches in the evolution of P. australis were outstanding: the American lineage and the European lineage. SR/DR came from the late expansion of the European lineage and separated during the Last glacial period (11.5–80 kya). The intense environmental changes in Quaternary likely caused genetic diversity accumulation, which became the driving force for the DR formation. Our estimated divergence time approach for Phragmites ecotypes will help to explore the phylogenetic status and environmental adaption process of polyploid taxa within Poaceae. [ABSTRACT FROM AUTHOR]

• Distribution of spiny acritarchs from the lower Doushantuo Formation in the Yangtze Gorges area is reported. • Eukaryotes diversified within about 10 Myrs after the Marinoan deglaciation. • Fifteen new acanthomorphic forms are recognized and systematically described. As part of the most common eukaryotic fossils in early Ediacaran strata, acanthomorphic acritarchs are crucial for understanding the biostratigraphy and evolutionary dynamics of marine eukaryotes after the Marinoan global glaciation. Abundant and diverse acanthomorphic acritarchs have been reported from the Ediacaran Doushantuo Formation in the Yangtze Gorges area, South China, and different biozonation schemes have been proposed. However, these previously published biozones were based on biostratigraphic data compiled from different stratigraphic sections, with little effort to test whether these biozones can be consistently recognized at different sections, despite the fact that regional consistency is critical to a robust biostratigraphic framework. Also, the evolutionary pattern of the Doushantuo acritarchs has not been documented in detail, especially for acritarchs from the lowermost Doushantuo Formation, largely due to the perceived low taxonomic richness after the Marinoan global glaciation. In this study, we report silicified acanthomorphic acritarchs and other eukaryotic microfossils from chert nodules in the lower part (Member II) of the Doushantuo Formation at the Jiulongwan, Jinguadun, and Wuzhishan sections in the Yangtze Gorges area. From a total of 1547 acanthomorphic acritarch specimens found, 24 genera and 69 species have been identified, including two new genera (Annularidens gen. nov. and Crassimembrana gen. nov.), six new species (Annularidens inconditus gen. et sp. nov., Bispinosphaera vacua sp. nov., Crassimembrana crispans gen. et sp. nov., C. multitunica gen. et sp. nov., Distosphaera jinguadunensis sp. nov., and Mengeosphaera matryoshkaformis sp. nov.), five unnamed species (Annularidens sp., Mengeosphaera sp. 1, Mengeosphaera sp. 2, Sinosphaera sp., and Variomargosphaeridium sp.), and three possible new forms tentatively placed in open nomenclatures (Crassimembrana cf. C. crispans , Tanarium cf. T. conoideum , and Weissiella cf. W. grandistella). The high-resolution fossil occurrence and abundance data from the three sections reveal both spatial variations in acritarch composition, and stratigraphic similarities in acanthomorph range and abundance, indicating that acanthomorph taxa can be applied to biostratigraphic subdivision and correlation only if their stratigraphic records are thoroughly investigated at least at the regional scale. The FADs (first appearance data) of acanthomorph species such as Appendisphaera grandis , Appendisphaera heliaca n. comb., Ericiasphaera fibrilla , and Tianzhushania spinosa , as well as the relative abundance variations of certain taxa, are recognized as promising biostratigraphic markers in lower Doushantuo Formation. The new data also reveal a rapid diversification of marine eukaryotes, with taxonomic richness of acanthomorphs increasing to notable levels within probably ten million years after the termination of the Marinoan glaciation, followed by continuing increase in both taxonomic richness and evenness afterwards. [ABSTRACT FROM AUTHOR]

Greenland stadials and interstadials (GS and GIS) are prominent features in ice core records of the last glacial period and are characterized by millennial-scale climate oscillations with sub-decadal- to decadal-scale hydroclimatic shifts. Over the past two decades, studies of Chinese stalagmite records have revealed corresponding Chinese Stadials/Interstadials (CS/CIS). However, the CS/CIS shifts and their corresponding forcings across the Asian monsoon region are still not fully understood. In this study, we present a 230Th-based sub-decadally-resolved stalagmite δ18O record from Xianyun Cave in southeastern China covering the period 58.2–50.8 kyr BP (before 1950 AD) and including GIS (and CIS) 16–14. We used GIS (CIS) 15.1 (peak point) and 15.2 (first point) to chronologically link the high and low-latitude records. We found that the onset of GIS 14 in our record occurred earlier than in an ice core record from Greenland and stalagmite records from northern China. This finding implies that low-latitude tropical climate likely played a key role in triggering abrupt millennial-scale events. Moreover, the transition into GIS 14 lasted 1.49 kyr in our record, which is in contrast to the abrupt temperature rise observed in NGRIP (the North Greenland Ice Core Project, 0.02 kyr). Compared with previous stalagmite records, we identified two transitional patterns into GIS 14 in monsoonal China: 1) a rapid transition in northern China and 2) a gradual transition in southeastern China. The gradual transition in our Xianyun record is analogous to a sea surface temperature (SST) record in the western tropical Pacific, highlighting a possible inherent connection between the changes in western tropical Pacific SSTs and East Asian summer monsoon variability in southeastern China. Paleoclimate records in southeastern China are therefore critical for understanding the mechanisms of abrupt millennial-scale climate events, as they can act as a bridge between high- and low-latitude records. • A new 7-yr-resolved stalagmite record of the East Asian summer monsoon from 58.2 to 50.8 kyr BP. • A double peak in the stalagmite record during GIS 15 occurred from 56.02 to 55.12 kyr BP. • The transition into CIS 14 lasted 1.49 kyr (millennial duration) in southeastern China. • The gradual transition into CIS 14 was modulated by tropical hydroclimate. [ABSTRACT FROM AUTHOR]

The continuous existence of the Marinoan Ice Age, a late Cryogenian panglaciation (Snowball Earth), is challenged by the occurrences of widespread glacial marine and nonglacial deposits consisting of stratified diamictite, laminated siltstone and claystone, and even carbonates, which indicate an episode of partial deglaciation. Red beds that commonly accompany these glacial marine and nonglacial deposits have not received enough attention to date. The middle Nantuo Formation of the Cryogenian Marinoan epoch in the Sanshengtai section, Shennongjia area, is composed of 6 lithofacies, i.e., Green Massive Diamictite, Green Laminated Lithic Feldspar Wacke, Green Laminated Siltstone and Claystone, Red Laminated Lithic Feldspar Wacke, Red Crudely Stratified Diamictite, and Red Laminated Siltstone. Among them, the last three constitute the red beds and are interpreted as glacial lacustrine and nonglacial deposits, which can be found and roughly correlated across several continents. High Fe 2 O 3 and low Ce/Ce* values in the red beds suggest a probable association between the formation of red beds and the Neoproterozoic oxygenation events. Coincidences between the occurrences of red beds and high values of Al/Na, Ti/Na, and chemical index of alteration (CIA) indicate the favorability of warm intervals with high weathering intensities for the formation of red beds, whose presence indicates partial deglaciation during the Marinoan Ice Age and provides a new clue to contradict the worldwide Snowball Earth hypothesis. • Red beds exist in the middle Cryogenian Nantuo Formation in the Shennongjia area. • Red beds formed in glaciolacustrine and nonglacial environments. • Warm and oxidized climate with intense weathering favors the formation of red beds. • A partial deglaciation occurred during the Marinoan Snowball Earth. [ABSTRACT FROM AUTHOR]

• The Neoproterozoic-Cambrian hydrocarbon source rock occurred in South China and Tarim. • Interglacial source rocks with varied thickness in South China was caused by rifts. • Poor-quality Sinian source rocks in the Tarim Basin were due to strong weathering. • The Cambrian source rock with high TOC content was related to a global transgression. The Late Proterozoic–Early Cambrian, one of the most critical intervals in Earth's history, is characterized by dramatic tectonic, climatic, oceanic and biological changes. In China, thick black mudstones and shales formed in intracontinental rifts during this period, associated with interglacial and postglacial phases of the Neoproterozoic global-scale glaciations. Previous studies have shown these black mudstones and shales were potential hydrocarbon source rocks that contributed to the Proterzoic-Early Paleozoic oil and gas discoveries. However, less work has been done to systematically characterize these important source rocks. In the South China Block, these excellent source rocks (~30–200 m) were discovered in the Nanhua (Cryogenian), Sinian (Ediacaran), and Lower Cambrian Systems, with total organic carbon (TOC) contents of 2–10%. In contrast, black mudstones in the Nanhua and Sinian Systems in the Tarim Basin had low TOC contents (0.3–1.5%) perhaps affected by intense weathering, whereas excellent source rocks (TOC ~ 6–18%) existed in the Cambrian Yuertusi Formation (12–80 m). Our study indicates the formation and distribution of excellent source rocks were mainly controlled by the Late Proterozoic–Early Cambrian rifts, which was supported by a decrease in thickness towards marginal areas especially for the Nanhua and Sinian Systems. The Early Cambrian source rocks occurred pervasively due to a global marine transgression and those formed under deep-water anoxic conditions at slope areas were of the best quality with TOC up to 15%. These source rocks could be focuses for future exploration in the deep or ultra-deep depths in the studied blocks as well as their peripheral areas. [ABSTRACT FROM AUTHOR]

• CIA of the Doushantuo Formation decrease in the intervals of EP1, EN2, and EN3. • The decreasing CIA in EP1 is consistent with the occurrence of glendonites. • The decreasing CIA in the EN2 is possibly related to the Gaskiers glaciation. • At least three relative colder periods are identified in the Doushantuo Formation. The Ediacaran Period (635–541 Ma) witnessed rapid turnovers of marine organisms that eventually led to the early Cambrian radiation. The Ediacaran Doushantuo Formation (ca. 635–551 Ma) serves as one of the most important and intensively studied stratigraphic units for understanding the co-evolution of life and environment during this critical time interval. To better understand the early-middle Ediacaran climate change, we reconstruct a temporal variation curve of chemical index of alteration (CIA) from a drill core and an outcrop of the Doushantuo Formation, in combination with previously published CIA data from segments of time-equivalent strata. The results show three distinct decreases in CIA values that correlate well with the positive carbon isotope (δ13C) excursion at the low Doushantuo Formation (EP1) and the negative δ13C excursion at the middle (EN2) and upper (EN3) Doushantuo Formation. The decline of CIA in EP1 is consistent with occurrence of glendonites at the same stratigraphic interval that suggests a cooling event. The low CIA values in EN2 and EN3 also suggest relatively colder periods that are consistent with evidence from strontium isotope (87Sr/86Sr) and oxygen isotope (δ18O) data. With existing bio- and chemostratigraphic constraints, the cooling event associated with EN2 might be synchronous with the Gaskiers glaciation. The other two cold periods associated with EP1 and EN3, however, have not been documented from other successions globally, which needs to be tested in future studies. [ABSTRACT FROM AUTHOR]

• Pollen from sediments in the northwestern shelf of the SCS were mainly derived from the Yungui and Tibetan Plateaus. • Arboreal trees were dominated between MIS5a and MIS1, including the glacial period. • High contributions of Pinus and lowland trees indicate a warm, wet climate in MIS3. The northwestern continental shelf of the South China Sea (SCS) is in a geographic location that was sensitive to the global paleoenvironmental change during the last glacial period. Here we present a high resolution palynological record of Core ZBW (100.65 m in length) from the continental shelf of the SCS in the past 82 ka. In contrast to results for the northern SCS, the core's pollen assemblage was dominated by arboreal trees between MIS5a and MIS1, even during the glacial period. Pollen provenance analyses indicated it was mainly from the drainage basin of the Red River, the Yungui Plateau and Tibetan Plateau. Between 66 and 64 ka, the contribution of Pinus fell while that of Cyclobalanopsis and trilete spores increased, indicating a drier and cooler climate. Conversely, during MIS3, the contributions of Pinus and lowland trees were high, indicating a warm and wet climate. The sedimentary environment in core ZBW alternated between coastal marine and river alluvial or shore facies. A sedimentary hiatus between 42 and 13 ka coincided with a significant fall in sea levels. Seismic data indicate that the Hainan paleo-river Delta (HPRD) process occurred at the core site between 65 and 56 ka, with extremely high rates of sediment deposition. Pollen data indicate the HPRD process was coincided with a transition period from cooler and drier climate to warmer and wetter climate, and lower sea levels to higher sea levels. [ABSTRACT FROM AUTHOR]

Records of carbonate ion concentration ([CO 3 2−]) and benthic carbon isotope (δ13C) have profound implications for exploring deep water circulation and global carbon cycle. However, information on the glacial-interglacial deep ocean [CO 3 2−] changes is still limited, especially in the Pacific Ocean. Here, we present new deep water [CO 3 2−] records of the last glacial cycle, reconstructed by the B/Ca ratios of benthic foraminifera Cibicidoides wuellerstorfi from two cores in the South China Sea (SCS). The deep water [CO 3 2−] changes of the SCS display similar trends with that of the western Pacific as well as "Pacific-type" CaCO 3 (%), suggesting that the deep water carbonate chemistry of the SCS may reflect that of the Pacific. Our results support that carbonate dissolution is the primary driver for "Pacific-type" CaCO 3 preservation during the late Quaternary glacial cycles. At the marine isotope stage (MIS) 5a to MIS 4 transition, deep water [CO 3 2−] decreased with an amplitude of ∼7 μmol/kg in the SCS, roughly consistent with that from the Pacific cores at 2300–4300 m water depth. Considering a greater oceanic alkalinity and stronger carbonate dissolution at that time, this implies that deep Pacific carbon storage increased. The gradients of deep water [CO 3 2−] and δ13C between the Pacific and the SCS reduced during extreme glacials (e.g., MIS 2, 4 and 6) relative to interglacials (e.g., MIS 1 and 5e), indicating weakened deep ocean ventilation and more sluggish Pacific deep-water circulation. This change is also confirmed by meridional δ13C distributions in the western Pacific for the Holocene and the last glacial maximum (LGM), and further supported by climate simulations using a complex Earth System Model. Overall, our results suggest that the increased deep Pacific carbon storage correlated to increased oceanic alkalinity and more sluggish Pacific deep-water circulation would have contributed to the atmospheric CO 2 decrease during the last glacial period. • Benthic foraminifera B/Ca-derived deep water [CO 3 2−] records of the South China Sea over the last glacial cycle. • Pacific deep-water circulation was weakened during glacial periods, indicated by the Pacific-SCS gradients of [CO 3 2−] and δ13C. • The deep Pacific carbon storage increased during the MIS 5a-4 transition, contributing to the atmospheric CO 2 decrease. [ABSTRACT FROM AUTHOR]

Greenland Interstadial-21 (GIS 21), with a centennial-scale precursor event and a "rebound-type" event, was one of the longest warm millennial-scale events recorded in Greenland ice cores during the last glacial period. Precise determination of its timing and duration can improve our understanding of regional/global climate correlations over Marine Isotope Stages (MIS) 5b/5a and 5a/4. Here, a precisely 230Th-dated decadally-resolved stalagmite δ18O record from Xianyun Cave, Fujian Province, southeastern China, is utilized to reconstruct the sub-millennial-scale changes in East Asian summer monsoon (EASM) from 87.6 to 76.3 kyr BP (before 1950 CE), covering Chinese Interstadial 21 (CIS 21) event. A comparison of spatially-separated Chinese speleothem records during GIS 21 shows a decrease in speleothem δ18O values from southeastern China to northwestern China. These δ18O spatial gradients could be attributed to the "rainout effect" and the amplification mechanism of the seasonal variations of precipitation δ18O. Moreover, Xianyun δ18O record captures the precursor event centered at 85.3 ± 0.3 kyr BP concurrent with the corresponding event in ice cores, revealing an atmospheric teleconnection between high and low latitudes. Unlike gradual cooling at the Greenland and Antarctic ice core records during mid-GIS 21, the Xianyun record reveals a relatively strong monsoon phase. We speculate that the cooling of the Southern Hemisphere (SH) may influence EASM activity through the intensification of cross-equatorial flow and weaken the impact of Northern Hemisphere (NH) high latitude climate, thus pointing to the role of SH climate on EASM on millennial-scale. • The first precisely-dated stalagmite record in southeastern China covering CIS 21. • GIS 21 event is determined from 83.8 to 76.6 kyr BP. • A precursor event centered at 85.3 kyr BP is recorded in our stalagmite. [ABSTRACT FROM AUTHOR]

• The well-preserved micro-macro scale subglacial forms and erosional landscapes are widely presented on the surface of the residual Mesoproterozoic quartzite basement rocks in North China. • A continental ice sheet gradually advanced from highland in the north to shallow sea in the south during Luoquan glacial period in North China. • An icehouse environment of Proterozoic-Phanerozoic transition period in global greenhouse background is indicated. Diamictites of late Ediacaran to early Cambrian age (ca. 551–518 Ma) are widespread across Southeast–Central Asia, with the Luoquan Formation particularly well preserved along the southern margin of the North China craton. A basal unconformity, comprising striations and p-forms interpreted to have been produced subglacially, was cut into Mesoproterozoic basement. Integrating new observations on the basal unconformity with the stratigraphy and sedimentology of the Luoquan Formation, an unequivocal glacial origin is demonstrated. The succession evolves from massive or stratified diamictite at the base to laminated fine-siltstone with dropstones upward, and is capped by siltstone with or without dropstones on the top. These lithological combinations represent a glacial sedimentary succession deposited recording progressive retreat of the ice margin. Based on multiple palaeoflow measurements, data from 7 new measured sections, and facies analysis, a new paleogeographic model is proposed. This model envisages the expansion of a large continental ice sheet from north to south at the southern flank of the North China Craton (NCC). [ABSTRACT FROM AUTHOR]

The paleo-synoptic conditions that prevailed during the past ∼80 kyr in northeastern China are inferred from the elemental and Sr–Nd isotopic compositions of Lake Sihailongwan Maar sediments. The detrital fraction in the lake sediments is dominated by aeolian input of felsic-rock origin, with little contribution of local volcanic material. Based on the isotopic Sr–Nd composition of the lake core-sediments, we postulate that the deserts of northern China are the main source of allochthonous particles to the lake throughout the past ∼80 kyr. Northwesterly winds associated with the East Asian winter monsoon and high latitude westerlies are the main carriers of dust from these deserts to the lake. The deserts of central China are an additional minor dust source. The episodic dust input from these deserts results from anomalous dry southwesterly winds. These could be related to either El Niño conditions, or to delays in the onset of the East Asian summer monsoon rains. • Sihailongwan Maar sediments are dominated by dust from deserts of northern China. • The deserts of central China are a secondary dust source of dust the lake. • Central deserts dust reflect ENSO conditions or delays in onset of summer monsoon. • Synoptic conditions in Sihailongwan are stable throughout the last Glacial Period. [ABSTRACT FROM AUTHOR]

• Well-persevered Paleoproterozoic microfossils described and illustrated. • A new genus of Acritarch, Dongyesphaera , is established. • Morphological diversity of microfossils increased through the Paleoproterozoic. • Evidence for the earlier occurrence of metabolic activity in eukaryotic protists. The Paleoproterozoic Hutuo Group is well-developed and distributed in the Wutai Mountains in the Xinzhou area of Shanxi Province, North China. Its middle part - the Dongye Subgroup is more suitable for obtaining microfossils in deposited sediments characterized with sandstone or slate in the lower part, and upward into interbedded sandstone, carbonate with stromatolites and phyllite. Based on recent zircon dating, the Hutuo Group was deposited around 2150–1950 Ma. In this study, eight morphological genera of microfossils, including the spheroid and filamentous cyanobacteria Eoentophysalis , Sphaerophycus , Siphonophycus , Pseudodendron , and the acritarchs Dictyosphaera , Dongyesphaera gen. nov., Leiosphaeridia , Satka were identified from the Wenshan, Hebiancun and Tianpengnao Formations of the Dongye Subgroup. The identified microfossils reveal that eukaryotic protists exercised metabolic activities rarely observed to have occurred in what are thought to have been suitable environments. [ABSTRACT FROM AUTHOR]

• First report of Li isotope data in the Cryogenian clastic sedimentary strata. • Negative Li isotopic excursion in the basal Cryogenian interglacial interval. • Low Li isotope values suggested enhanced silicate weathering intensity. • Extensive seawater euxinia was triggered by intense silicate weathering. The Cryogenian Period comprised two episodes of global glaciation (Sturtian and Marinoan glaciations) separated by a non-glacial interval, which was characterized by early radiations of eukaryotic algae and putative metazoans. Geochemical data indicate that the non-glacial interval might be marked by a transient marine oxygenation, nevertheless oceanic redox conditions varied both in time and space. Further, the links between non-glacial climate and marine redox variations are not well constrained. Here we present high-resolution lithium isotope (δ 7 Li), Fe speciation and trace element (Mo and U) data for clastic sedimentary rocks from the Cryogenian interglacial Datangpo Formation, South China, in order to track the evolution of continental chemical silicate weathering and driving factors behind marine redox variability during the Cryogenian non-glacial interval. A significantly negative δ 7 Li excursion of ∼ − 5 ‰ is observed in the basal Datangpo Formation, suggesting a dramatic increase in chemical silicate weathering intensity in the aftermath of the Sturtian glaciation. Expansion and contraction of anoxic-sulfidic conditions, as demonstrated by Fe speciation and trace element (Mo and U) data, mirror changes in silicate weathering intensity. Our study provides evidence that greater nutrient and sulfate availability, due to high silicate weathering intensity associated with increased exposure of fresh rocks and a warm climate, facilitated the spread of euxinic waters over the continental margins of the otherwise ferruginous Cryogenian ocean. [ABSTRACT FROM AUTHOR]

• Great Unconformity investigated using glaciogenic strata. • Whole rock compositions are used as proxy for Ediacaran Upper Continental Crust. • Glacial abrasion created of accommodation space. The "Great Unconformity" across the Proterozoic-Phanerozoic boundary has long been recognised as critical for understandings of the Cambrian Explosion and changes in sediment preservation. However in many parts of the Earth no rock strata are preserved for hundreds of millions of years leading up to the Cambrian Period. This study reports detrital zircon age and whole rock geochemical data from 43 samples of glaciogenic rocks in the Ediacaran Luoquan and Dongpo Formations. Detrital zircon age populations show a distinct peak at ca. 2.5 Ga and minor peaks at 2.2–1.6 Ga, typical of Mesoproterozoic provenance. It has been established that glaciogenic strata are uniquely suited as a proxy for the average upper continental crust (UCC). Applying this principle, the samples presented herein are used to provide insights into the UCC present in the North China Craton (NCC) during the Great Unconformity. This reveals UCC older than the Neoproterozoic but younger than the Great Oxygenation Event. Based upon these findings a tectonic and climatic model is proposed, using a modern analogue from Antarctica, wherein accommodation space was created by glacial abrasion whilst uplift continued throughout the NCC. This overdeepening process provides an explanation for the preservation of these glaciogenic strata, despite the Great Unconformity that surrounds them on all sides and this study contribute towards understanding of processes in the NCC during a critical time when little has survived into the rock record. [ABSTRACT FROM AUTHOR]

A 67-yr-resolution δ18O profile of a230Th-dated stalagmite from Luoshui Cave, central China, is presented to refine the Asian summer monsoon (ASM) history from 336 to 290 kyr BP. The sub-stages of Marine Isotope Stage 9 (MIS 9) are clearly reflected in the Luoshui δ18O record, in line with changes in the Northern Hemisphere summer insolation (NHSI). The concurrency of eight weak monsoon intervals (WMIs) between 320 and 290 kyr BP and shifts in the Atlantic oceanic circulation suggest that monsoon weakening was forced by northern high-latitude climate oscillations with north-south shifts in the Intertropical Convergence Zone (ITCZ). Spectrum analyses show a cyclic change of 1–4 kyr between 320 and 290 kyr BP, similar to the Dansgaard-Oeschger cycles during the last glacial period. This suggests a relatively unstable monsoon state when the northern ice volume reached intermediate levels. The detrended δ18O agrees well with the δ13C record on the millennial to sub-millennial scales, suggesting a coupling of monsoon climate and cave environment. After removal of the summer insolation signal at 65°N, the residual Luoshui δ18O record is highly similar to orbital- and millennial-scale temperature changes in Antarctica in an anti-phased fashion, revealing the significant influence of Southern Hemispheric climates on ASM intensity. The absence of counterparts of the two WMIs between 315 and 310 kyr BP in Antarctica, however, indicates a complicated teleconnection. • A high resolution and precision dating stalagmite record covered MIS9 in China. • A potential chronologic benchmark for global millennial-scale events in MIS9. • Eight WMIs over MIS9 presented anti-phased relationship with Antarctic temperature. [ABSTRACT FROM AUTHOR]

• The increasing δ98Mo values of the marine sedimentary rocks reveal an oxygenation of seawater. • The TOC and Mo contents indicate that intense chemical weathering ceased when the cap carbonate precipitated. • A lagged response of Mo isotope system to the shallow-ocean oxygenation at the bottom of the interval III. • The ocean has been widely oxidized at the early Cambrian. In the geological time, atmosphere and ocean have experienced two important oxidation events which are the Paleoproterozoic Great Oxidation Event and the Neoproterozoic Oxidation Event. These events had a great influence on the origin and evolution of life and the system of atmosphere, ocean and earth surface. The record of early metazoan fossils and the radiation of marine algae occurred following the Marinoan glaciation in the Neoproterozoic. Hence, an ocean oxygenation event at the boundary of Cryogenian and Ediacaran is closely associated with the biological evolution. Here, we present new TOC contents, Mo concentrations, C-O-Mo isotopic data of sedimentary rocks collected across the boundary (~635 Ma) between the Nantuo and Doushantuo Formations in the Shennongjia area, South China. Based on the isotopic data, three intervals can be distinguished: Interval I, the Nantuo Formation beneath the cap carbonate of the Doushantuo Formation, has the highest TOC (0.03%) and Mo concentration (5.494 ppm) and similar tendency of the δ13C values and the δ98Mo values, which represent the enhanced chemical weathering, the raised nutrient input and the higher primary productivity. Interval II, the cap carbonate, possesses low TOC and Mo concentrations and the consistently diminished carbon composition and the fluctuating δ98Mo values. Interval III, the sediments above the cap carbonate of the Doushantuo Formation, is characterized by low TOC and Mo concentration, which is similar with the Interval II, but displays decreasing δ13C values and increasing δ98Mo values. These features of the Interval II and III were contributed by the end of high intensity chemical weathering, resulting in the atmosphere and shallow-ocean enriching oxygen. The δ98Mo values elevated until the interval III, indicating that the response of Mo isotope system lagged the shallow-ocean oxygenation. Our data, therefore, indicate an oxygenation from the Cryogenian to Ediacaran, which is in good agreement with the emergence of the Ediacaran biota. [ABSTRACT FROM AUTHOR]

Semiliquidambar cathayensis is a special and endangered plant in China, used for traditional Chinese medicine and in landscape applications. Predicting the impact of climate change on the distribution of S. cathayensis is crucial for its protection and the sustainable use of resources. We used the maximum entropy (MaxEnt) model optimized by the ENMeval data packet to analyze the potential geographic distribution changes of S. cathayensis in 12 provinces of Southern China for the different periods since the last interglacial period (LIG, 120–140 ka). Considering the potential geographic distribution changes in the province, and based on the two climate scenarios of Representative Concentration Pathways (RCP) 2.6 and RCP 8.5, the distribution range of S. cathayensis was analyzed and we predicted the range for the 2050s (average for 2041–2060) and 2070s (average for 2061–2080). The area under AUC (Area under the receiver operating characteristic (ROC) curve) is 0.9388 under these parameters, which indicates that the model is very accurate. We speculate that the glacial period refugia were the Nanling and Wuyi Mountains for S. cathayensis, and central and Western Fujian and Taiwan are likely to be the future climate refugia. In the mid-Holocene (MH, 6 ka), the growth habitat was 32.41% larger than the modern habitat; in the 2050s and 2070s (except RCP2.6–2070s), the growth habitat will shrink to varying degrees, so efforts to support its in situ and ex situ conservation are urgently needed. The jackknife test showed that the main factors affecting the geographical distribution of S. cathayensis were annual precipitation, precipitation of the wettest month, and precipitation of the driest month. The annual precipitation may be the key factor restricting the northward distribution of S. cathayensis. In general, the centroid of the distribution of S. cathayensis will move northward. The centroid of the adaptive habitats will move northward with the highest degree of climate abnormality. We think that Hainan Island is the most likely origin of S. cathayensis. These findings provide a theoretical basis for the establishment of genetic resources protection measures, the construction of core germplasm resources, and the study of the formation and evolution of Hamamelidaceae. [ABSTRACT FROM AUTHOR]

• Tuff zircon TIMS U-Pb age of 720.16 ± 1.40 Ma was reported from the upper Gongdong Formation; • Monte Carlo simulation suggests a 717.61 ± 1.65 Ma onset age for the Sturtian glaciation in South China; • New age is consistent with the geochronological records in Laurentia and the Arabian-Nubian Shield; • New age represents an important step forward for testing rapid and synchronous global Sturtian glaciation. Neoproterozoic glaciations have drawn worldwide attention in recent years because of their influence on atmosphere, hydrosphere, biosphere, lithosphere, and potential causal relationship to the subsequent Cambrian evolutionary explosion which represents the most important event in the history of life on Earth. The Snowball Earth hypothesis predicts a rapid and synchronous initiation of the Neoproterozoic glaciations, but convincing radiometric dates to constrain this hypothesis are yet to be established. Dating this event is often compromised by indistinct stratigraphic relationships and the presence of detrital zircon grains. In this study, we present a chemical abrasion–isotope dilution–isotope ratio mass spectrometry (CA-ID-IRMS) U-Pb zircon age from the upper Gongdong Formation of South China, ca. 25 m below the base of the Chang'an diamictite. This new data combined with Monte Carlo modelling suggests the onset of the Sturtian glaciation, in South China, occurred after <718.8 Ma, possibly 717.61 ± 1.65 Ma. This new age is consistent with the geochronological records in Laurentia and the Arabian-Nubian Shield, an important step forward for testing rapid and synchronous global Sturtian glaciation. [ABSTRACT FROM AUTHOR]

• Both massive diamictite and sandstone/mudstone deposits are observed in the Nantuo Formation. • Two ice advance-retreat sedimentary cycles were identified in the Nantuo Formation. • During the Nantuo glaciation, climate, sea level and sedimentary environment evolution may be closely related. • The Marinoan glaciation may be characterized by episodic evolution rather than monotonous ice-covered evolution. Detailed sedimentological investigations of the Cryogenian glacial deposits are critical for constraining the true nature of the Sturtian and Marinoan glaciations. The entire succession of the Nantuo Formation, which corresponds to the Marinoan glaciation, is well developed in South China. Here a detailed lithological and sedimentological analysis of two cores of the Nantuo Formation in Guizhou, South China, is presented in which two continuous ice advance–retreat cycles are identified. The base consists of a massive diamictite lithofacies that is representative of glacier-dominated subaqueous debris flow deposits. These proximal glaciomarine deposits are overlain by a gravel-free sandy mudstone lithofacies that is lacking in diamictites, which implies distal glaciomarine deposits. This ice advance–retreat sedimentary cycle is overlain by a weakly laminated diamictite lithofacies, which represents subaqueous debris flow deposits that formed during the second episode of ice advance. These proximal glaciomarine deposits are overlain by an interbedded sandstone–mudstone lithofacies, which is indicative of distal glaciomarine deposits that formed during another episode of ice retreat. These sedimentary cycles imply that the climate switched twice from relatively warm to extremely cold and back during the Marinoan glaciation. The global sea-level and sedimentary environments fluctuated in response to these climate changes. This co-evolution of the climate, sea-level, and sedimentary environments, which is represented by the lithofacies and sedimentary sequence of the Nantuo Formation, as well as the corresponding strata of other sections worldwide, suggests that the Marinoan glaciation is characterized by a progressive and dynamic course. [ABSTRACT FROM AUTHOR]

Driven by climate change, periods of dominating glacial and fluvial erosion have both sculpted mountain ranges during the Quaternary. To understand the evolution of mountain landforms, there is considerable interest in knowing which erosion agent leads to more incision, how glacial thermal regime impacts erosion and landscape development, and whether glacial erosion can result in increased relief. To investigate the relative efficiency of glacial and fluvial erosion, and the influence of glacial thermal regime on topography, we compare two different mountain ranges–the Qionglai Shan (monsoonal temperate glaciation) and Lenglongling (subcontinental glaciation) in western China. We use a 1-D model to construct presumptive fluvial longitudinal profiles if glaciation had not occurred, and compare these with the actual glacial profiles to obtain relative incision rates of fluvial and glacial erosion. Results demonstrate that glacial incision is smaller than fluvial incision in Lenglongling and larger than fluvial incision in the Qionglai Shan, which may be influenced by different tectonics and glacier types. Topographic analysis of glacial and fluvial valleys with similar drainage areas show that glacial erosion results in valley widening, local valley relief increase induced by isostatic uplift, and slope gradient increase in Lenglongling. However, there is no local valley relief and slope increase observed in the Qionglai Shan, which may reflect slope process responses to threshold hillslope limiting the height above valley bottoms. • Different relative efficiency of glacial and fluvial incision on the Tibetan Plateau. • Relief increase is influenced by isostatic uplift and threshold hillslope angles. • Tectonic uplift and glacier types control incision rate variations for rivers and glaciers. [ABSTRACT FROM AUTHOR]

The Cryogenian Period (~720–635 Ma) witnessed the most extensive and prolonged glaciation events in Earth history. Vast ice sheets of at least two global glaciations, the Sturtian (~720–660 Ma) and Marinoan (<654–635 Ma), advanced to sea level at low latitudes, a scenario that is at the heart of the general Snowball Earth hypothesis. This hypothesis is supported by results of recent work in geochronology and geochemistry, but certain parts of the glacial sedimentary records remained debated regarding ice sheet dynamics. Here we report findings from four sections of the Sturtian-age Tiesi'ao/Dongshanfeng Formation and related strata on the Yangtze Block in South China. Our work has documented the presence of four lithofacies: massive diamictite, crudely stratified diamictite, stratified to massive pebbly sandstone and dropstone-bearing laminated siltstone and our interpretation is that these rocks were deposited in proximal glacio-marine environments during five successive episodes of glacial advance and retreat. We have also identified an interval of deformation structures near the base of the Tiesi'ao/Dongshanfeng Formation that is characterized by upward increasing strain intensity, indicating that these structures were caused by overriding ice sheets. All the observations collectively suggest that the Sturtian ice sheets in South China were warm-based, rapidly moving, and sensitive to changes in climate. Further, our data suggest that the ice grounding line reached the slope area, implying a major drop in global sea level, enormous ice sheet thickness, or both during the Sturtian Glaciation. • Four lithofacies of Tiesi'ao/Dongshanfeng Formation (Cryogenian, South China) • The Tiesi'ao/Dongshanfeng Formation formed through five depositional stages. • The glacio-tectonic deformation near the base of the formation is observed for the first time. • A new glacio-tectonic deformation model is proposed. • Warm-based, productive and unstable ice sheets of Sturtian Snowball are inferred. [ABSTRACT FROM AUTHOR]

Conflicting published interpretations of marine redox conditions during the Ordovician-Silurian transition (OST) may have been linked to spatial redox heterogeneity during this interval. However, details of the pattern of redox heterogeneity and its underlying causes remain unclear. Here, we present a high-resolution geochemical study of a drillcore section (Pengye #1) from Pengshui County (Chongqing municipality, southwestern China) that was located in the semi-restricted inner Yangtze Sea during the OST. We analyzed Fe-speciation, redox-sensitive trace elements, major elements, and pyrite δ34S compositions (δ34S py) and then compared these data with published results from coeval sections at Datianba and Shuanghe in the same basin. The integrated dataset demonstrates pronounced spatiotemporal heterogeneity of redox conditions—especially the local development of euxinic conditions in the inner Yangtze Sea during the OST. Integrated data further suggest that high primary productivity and ample Fe fluxes in the inner Yangtze Sea may have depleted dissolved sulfate through microbial sulfate reduction (MSR) and subsequent pyrite formation, except in areas with enhanced sulfate supply from continental weathering or open-ocean exchange, which varied as a function of both tectonic (i.e., the regional Kwangsian Orogeny) and eustatic changes (i.e., the global Hirnantian glaciation). Limited sulfate availability thus likely prevented the development of euxinic conditions in some regions of the inner Yangtze Sea, as reflected in spatial variation of δ34S py. Our study highlights the potential role of sulfate availability on the development of watermass euxinia in semi-restricted marginal-marine basins during the OST. • Most detailed analysis to date of redox conditions in Late Ordovician inner Yangtze Sea of South China Craton • Multiproxy dataset (Fe species, trace metals, δ34S py) confirms spatiotemporal heterogeneity of redox conditions. • A redox shift from euxinic to suboxic/ferruginous conditions occurred during the mid-Hirnantian regression. • Development of euxinia within the inner Yangtze Sea was mainly controlled by local sulfate fluxes. • Local sulfate fluxes were strongly influenced by tectonic and glacio-eustatic changes. [ABSTRACT FROM AUTHOR]

The Yangtze Plain (floodplains in the middle and lower reaches of the Yangtze River) is a region with numerous lakes, including the three largest freshwater lakes in China, i.e. Poyang Lake (PYL), Dongting Lake (DTL), and Taihu Lake (THL). The formation mechanism of these lakes offers insights into the ongoing debate concerning the interaction between tectonic activity, climate, sea-level, human impact, and Earth-surface processes. Previous studies have usually focused on individual lakes, so there remains no over-arching and consistent framework for lake formation in the region as a whole. Here we review published sedimentary and chronological records on the above three lakes and propose that sea-level change has determined their formation. During the last glacial maximum (LGM; ca 30–20 ka), with a sea-level >120 m lower than present, a landscape of incised valleys and interfluves prevailed over the entire Yangtze Plain, including the DTL area, which is >1400 km upstream from the modern river mouth, and there was no large lake on the plain. The lakes emerged in the Holocene, although more precise ages await further investigations. The glacial sea-level lowstand, with concomitant headward incision, was responsible for the extensive deeply incised landscape of the LGM, whereas the Holocene high sea-level, with resultant infilling of the incised valleys, accounted for the formation of lakes. This sea-level forcing hypothesis suggests a more far-reaching influence of sea-level change on the Yangtze Plain, and a closer relationship between Earth-surface processes and glacial–interglacial cycles (global climate) than is commonly believed. According to our newly hypothesized climate-controlled geomorphological (CCG) model, it is very likely that similar lake-forming processes could have occurred multiple times during earlier glacial–interglacial cycles, and that this pattern might also have occurred in many other river systems in the eastern coastal areas of China, as well as in other similar river plains worldwide, thus having an important role in shaping modern coastal-plain landscapes. Further work is required to test this CCG model. • We propose a model that sea level controlled the land surface processes and lake formation in Yangtze Plain. • During glacial period deep-cut landscape prevailed in the plain due to sea level lowering and concomitant headward incision. • Sea level rise after LGM raised Yangtze water level which filled up the incised valleys and depressions to form lakes. • Influence of sea level change on land surface at orbital timescales could be felt >1400 km upstream from the coast. [ABSTRACT FROM AUTHOR]

Long-lived and extensive glaciation during the Carboniferous and early Permian has been the focus of many studies over the past decade revealing systematic changes in sea level and climatic conditions. The nature of the inception of Carboniferous glaciation, however, remains poorly resolved with uncertainty regarding the timing and dynamics of buildup of continental ice sheets. Here we present detailed sedimentary facies and depositional cycles from Upper Mississippian shallow-water platform and contemporaneous carbonate slope successions from the eastern Paleo-Tethys Ocean region (South China) to reveal systematic variations that provide insight into the sedimentary response to the onset of Carboniferous glaciation. Based on detailed sedimentological logging and facies analysis, four upper Visean cycles and four Serpukhovian cycles were identified from the carbonate platform Yashui section, bounded by either subaerial surfaces or zones, or transgressive surfaces. The cycle tops roughly correspond to intervals rich in normally graded bioclastic wacke- to packstones and with distinct rises (~1‰) in conodont δ18O PO4 in the carbonate slope Naqing section. In particular, the four Serpukhovian cycles correlate well to depositional cycles defined in the Lower Yangtze Platform succession of South China and in the cyclothemic successions in the Donets Basin, Ukraine, suggesting a glacio-eustatic control, most likely caused by repeated advance and retreat of Gondwana glaciation during the onset but prior to widespread glaciation across the mid-Carboniferous boundary. • Facies analysis revealing late Mississippian depositional cycles from South China • Karsted features supporting a middle Brigantian major glacio-eustatic fall • Well-correlated Serpukhovian 1–2 Myr cycles suggesting a glacio-eustatic control [ABSTRACT FROM AUTHOR]

• Abundant sheet cracks are discovered in the Doushantuo cap carbonates in South China. • Low Ge/Si ratios of silica-filling in sheet cracks indicate the predominate seawater origin of Si. • LREE-depleted REE patterns with positive Eu anomalies indicate contribution from hydrothermal fluids. • There were weak synglacial hydrothermal activities during the Marinoan snowball glaciation. The rapid diversification of eukaryotes within 3 million years after the Marinoan global glaciation suggests the potential linkage between the snowball Earth event and biological evolution. To understand how the global glaciation and the biological evolution were linked, it is necessary to reconstruct the sequence of events with high temporal resolution that occurred during the deglaciation. In this study, we focus on silica-filling within sheet cracks. Sheet cracks abundantly occur in the basal part of the Marinoan cap carbonate (635 Ma), and are characterized by the interconnected horizontal and vertical cracks that are sequentially cemented by dolospars, silica and calcite. As the second stage of crack filling, the origin of silica-filling remains controversial. If the seawater origin is confirmed, the silica-filling might archive the signal of ocean chemistry in the aftermath of snowball Earth event. In this study, we measured the Germanium/Silica ratios (Ge/Si) and Rare Earth Elements (REE) compositions of silica-filling from the Doushantuo cap carbonate in the Yangtze Platform, South China. The silica-filling has low Ge/Si ratios (~1 μmol/mol), and displays a light REE (LREE) depleted REE pattern (normalized to PAAS) with positive Eu anomalies (Eu/Eu*). These results indicate the predominant seawater origin of silica with some contribution from hydrothermal fluid, suggesting the penecontemporaneous precipitation of silica-filling with respect to sheet crack formation. In order to quantify the contribution from hydrothermal fluid, we developed a binary mixing model by using Ge/Si ratio and Eu/Eu* as two independent proxies. The modeling results indicate mixing of ~5 vol.% hydrothermal fluid with contemporaneous seawater, or ~20 wt.% of Si in silica-filling from hydrothermal fluid. The modeling results also show that the synglacial hydrothermal flux might be one order of magnitude lower than the modern level, suggesting extremely weak hydrothermal activities during the Marinoan snowball glaciation. [ABSTRACT FROM AUTHOR]

• Sedimentology, geomorphology, detrital zircon data from Cryogenian of NW Tarim Craton. • Marinoan subglacial striated surface overlain by subglacial and proglacial strata. • Temperate ice fed supraglacial debris to a dynamic, ice-marginal, open water setting. • Study area developed from basinal to uplifted subaerial topography through Cryogenian. • Uplift likely associated with an active margin setting. Ubiquitous glaciation was the hallmark of the Cryogenian Period (ca. 720–635 Ma), therefore understanding the character, behaviour, extent and configuration of Cryogenian ice bodies is a fundamental requirement in reconstructing climates and environments from the period. Unfortunately, despite abundant evidence for glaciation, there is a strong preservational bias towards basinal glaciogenic sedimentary strata and against subglacial strata. In particular subglacially striated surfaces, owing to their fragile millimetre-thickness, are very rare and represent only a tiny proportion of the global Cryogenian outcrop area. Thermal regime is one of the most important controls of glacial behaviour and subglacially striated surfaces are one of the very few means of determining an ancient temperate thermal regime. In this context we present sedimentological and detrital zircon detail of a fortuitously preserved Cryogenian (Marinoan) outcrop in the Aksu-Wushi area of the Tarim Craton, NW China. The Yuermeinak Formation preserves not only a subglacially striated surface and palaeotopography but also a thin, locally preserved, subglacial tillite. Together these indicate grounded ice. The remaining formation reveals glacial retreat and deposition of predominantly supraglacially-sourced debris within a dynamic, open-water, ice-proximal proglacial environment. A palaeogeographic reconstruction is proposed in which the Aksu-Wushi area developed from a deeper-water basinal environment, without clear evidence for glaciation, during the early Cryogenian, to an area of mountainous uplift with nearby grounded glacial ice, during the latter Cryogenian. Combining detrital zircon data of this study with published data it is further proposed that this development was linked to an active margin setting, either through expansion of an Andean-type mountain range to the north of the study area or flank-uplift of a back-arc basin. [ABSTRACT FROM AUTHOR]

• Neoproterozoic cap carbonates are discovered on the western margin of North China Craton. • The Zhengmuguan Formation in North China may provide evidence for mid-late Ediacaran glaciation. • High spatial resolution of major, trace and rare earth elements and carbon analysis are used for the interpretation of depositional environments. The late Neoproterozoic Era was characterized by dramatic transitions in climate, including Snowball Earth glaciation, and in the increasing oxygenation state of the atmosphere and oceans. However, late Neoproterozoic glacial deposits are poorly documented in North China. To better understand the Neoproterozoic glacial events in North China, we investigated five sections along a north-south transect across the Helan Mountains capturing a transition from shelf margin to intrashelf basin. This effort revealed an excellent exposure of Neoproterozoic diamictite and associated carbonate succession (Zhengmuguan Formation) on the western shelf margin of North China. Sedimentary features in the diamictite indicate that it might be a glacial sequence partially influenced by sediment gravity flows, with values for the Chemical Index of Alternation (CIA) consistent with cold, arid depositional environment. The overlying carbonate succession is sporadic, with exposures confined mostly to southern areas that disappear to the north. Identification of the Zhengmuguan sequence as a cap carbonate is based on the occurrence of distinctive attributes that are widely found in typical Neoproterozoic cap carbonates around the world. The ∼1.6-m-thick cap carbonate consists of a lower thinly laminated dolomite and an upper thick-bedded dolomite, directly overlying the top of the Zhengmuguan glacial diamictite. Based on field and petrographic observations and high-resolution geochemical analyses of major, trace, and rare earth elements; organic carbon isotopes (δ13C org); and total organic carbon (TOC), we are able to interpret the depositional environments and the possible origin of the cap carbonate. The occurrence of late Ediacaran fossils in the overlying Tuerkeng Formation imply that the Zhengmuguan Formation is mid-late Ediacaran and thus may represent a mid-late Ediacaran glaciation. Our petrographic and geochemical results suggest the Zhengmuguan cap carbonate was initially deposited via glacial meltwater with significant inputs from continental weathering subsequently overprinted by upwelling anoxic deep seawaters along a continental margin. In summary, our data from a poorly known mid-late Ediacaran cap carbonate capture a high-resolution record of shifting climatic and oceanographic conditions of at least regional importance. The uncertainties of these interpretations are high, but the potential importance of these findings justifies the need to publish the data and our conclusions—along with the unavoidable caveats that come with any poorly dated frontier section. [ABSTRACT FROM AUTHOR]

The Neoproterozoic Era witnessed two low-latitude glaciations, which exerted a fundamental influence on ocean–atmosphere redox conditions and biogeochemical cycling. Climate models and palaeobiological evidence support the belief that open waters provided oases for life that survived snowball Earth glaciations, yet independent geochemical evidence for marine redox conditions during the Marinoan glaciation remains scarce owing to the apparent lack of primary marine precipitates. In this study, we explore variability in rare earth elements (REEs) and trace metal concentrations in dolostone samples of the Cryogenian Nantuo Formation taken from a drill core in South China. Petrological evidence suggests that the dolostone in the Nantuo Formation was formed in near-shore waters. All the examined dolostone samples featured significant enrichment of manganese (345–10,890 ppm, average 3488 ppm) and middle rare earth elements (MREEs) (Bell Shape Index: 1.43–2.16, average 1.76) after being normalized to Post-Archean Australian Shale (PAAS). Most dolostone samples showed slight to no negative Ce anomalies (Ce*/Ce 0.53–1.30, average 0.95), as well as positive Eu anomalies (Eu*/Eu 1.77–3.28, average 1.95). This finding suggests that the dolostone samples were deposited from suboxic to iron-enriched and anoxic waters. Although total REE concentrations correlated positively with Th concentrations in dolostone samples, MREE-enriched PAAS-normalized patterns preclude the conclusion that REEs were largely introduced by terrestrial contamination. Rather, we interpret the correlation between REEs and Th as an indication that the former were transported by colloids and nanoparticles in meltwaters. Taken together, we propose that anoxic and ferruginous water columns dominated in South China during the Marinoan glaciation with a thin oxic/suboxic layer restricted to coastal waters. The extreme anoxic and ferruginous conditions prevailing in the Cryogenian would have provided a baseline for subsequent transient Ediacaran ocean oxygenation and life evolution. [ABSTRACT FROM AUTHOR]

The most striking aspect of the Cryogenian global geographic maps is the absence of polar continents. Most lands, either connected or isolated then, were located in the low-latitude area between 30°N and 60°S. Accumulating paleomagnetic data, however, indicate that the South China block and potentially its adjacent plates may have experienced multiple rapid latitudinal movements and was likely located in very high latitude area at the Cryogenian global colds' approach (~720 Ma). This presentation will address the high-latitude continental blocks during break-up of Rodinia. Existing sedimentary and paleomagnetic data show the possibility that, during ~830-720 Ma, there were two plaeolatitudinally different continent groups, even if both begat by Rodinia. The high-latitude continent group, represented by South China and India, and probably other small Asian blocks, was located in the northern hemisphere and has siliciclastic-dominated pre-Cryogenian strata. The low-latitude continent group, characterized by Laurentia and Australia, occupied the equatorial region and southern hemisphere and has carbonate-rich pre-Cryogenian strata. The polar continents were able to record a global greenhouse climatic condition pre- or during Cryogenian. They were also able to record the initial growth of the Snowball Earth ice sheets and thus have the great potential to test the synchroneity of the cryogenian glaciations. [ABSTRACT FROM AUTHOR]

Cooper et al. (Research Article, 7 August 2015, p. 602) combined the annual-layer-counted Greenland Ice Core Chronology 2005 with chronological information from the Hulu Cave and Cariaco Basin records to produce a "revised" time scale. We argue that their time scale is incompatible with the nature of annual-layer-counted time scales and may lead to seriously flawed conclusions if used elsewhere at face value. [ABSTRACT FROM AUTHOR]