State Key Laboratory of Marine Geology

Much of our understanding of Earth's past climate comes from the measurement of oxygen and carbon isotope variations in deep-sea benthic foraminifera. Yet, long intervals in existing records lack the temporal resolution and age control needed to thoroughly categorize climate states of the Cenozoic era and to study their dynamics. Here, we present a new, highly resolved, astronomically dated, continuous composite of benthic foraminifer isotope records developed in our laboratories. Four climate states-Hothouse, Warmhouse, Coolhouse, Icehouse-are identified on the basis of their distinctive response to astronomical forcing depending on greenhouse gas concentrations and polar ice sheet volume. Statistical analysis of the nonlinear behavior encoded in our record reveals the key role that polar ice volume plays in the predictability of Cenozoic climate dynamics.

The surface uplift history of the Tibetan Plateau (TP) offers a key testing ground for evaluating models of collisional tectonics and holds important implications for processes ranging from global cooling to the onset of the Asian monsoon. Various models have been proposed to reveal the surface uplift history of the TP, but controversies remain. We evaluate these models using data from sedimentology and stratigraphy, structural geology, magmatism, exhumation, and paleoaltimetry studies. Structural analyses indicate that thrust belts, which spread from the central TP outward toward its surrounding margins, accommodated most of the India–Asia convergence, and facilitated crustal shortening and thickening in the central TP. Eocene adakitic rocks located in the Qiangtang and the Lhasa blocks likely were generated by partial melting of an eclogitic source. Paleogene (50–30 Ma) potassic rocks only occur in the Qiangtang block, whereas Late Oligocene–Late Miocene (26–8 Ma) potassic rocks occur both in the Qiangtang and Lhasa blocks. Low-temperature thermochronologic ages in the central TP are older than 40–35 Ma, whereas those in the margins are younger than 20 Ma (mostly Late Miocene, and Pliocene/Pleistocene in age). Independent paleoaltimetry estimates suggest that the Lhasa and Qiangtang terranes attained their current elevations during the Eocene, most likely due to the initial collision between India and Lhasa, whereas the Hoh Xil basin area to the north and Himalayas to the south were still low, even below sea level in the latter case. We argue for an inside-out growth pattern for the Tibetan Plateau. The TP grew southward and northward from a nucleus of high topography and is likely to continue expanding along the Mazar Tagh fault to the northwest, the Kuantai Shan-Hei Shan-Longshou Shan to the northeast, the Longquan Shan to the east and the Shillong plateau to the south if the northward force of India would not diminished.

Abstract Combined analyses of deep tow magnetic anomalies and International Ocean Discovery Program Expedition 349 cores show that initial seafloor spreading started around 33 Ma in the northeastern South China Sea (SCS), but varied slightly by 1–2 Myr along the northern continent‐ocean boundary (COB). A southward ridge jump of ∼20 km occurred around 23.6 Ma in the East Subbasin; this timing also slightly varied along the ridge and was coeval to the onset of seafloor spreading in the Southwest Subbasin, which propagated for about 400 km southwestward from ∼23.6 to ∼21.5 Ma. The terminal age of seafloor spreading is ∼15 Ma in the East Subbasin and ∼16 Ma in the Southwest Subbasin. The full spreading rate in the East Subbasin varied largely from ∼20 to ∼80 km/Myr, but mostly decreased with time except for the period between ∼26.0 Ma and the ridge jump (∼23.6 Ma), within which the rate was the fastest at ∼70 km/Myr on average. The spreading rates are not correlated, in most cases, to magnetic anomaly amplitudes that reflect basement magnetization contrasts. Shipboard magnetic measurements reveal at least one magnetic reversal in the top 100 m of basaltic layers, in addition to large vertical intensity variations. These complexities are caused by late‐stage lava flows that are magnetized in a different polarity from the primary basaltic layer emplaced during the main phase of crustal accretion. Deep tow magnetic modeling also reveals this smearing in basement magnetizations by incorporating a contamination coefficient of 0.5, which partly alleviates the problem of assuming a magnetic blocking model of constant thickness and uniform magnetization. The primary contribution to magnetic anomalies of the SCS is not in the top 100 m of the igneous basement.

ABSTRACT Seismic data interpolation is a longstanding issue. Most current methods are only suitable for randomly missing cases. To deal with regularly missing cases, an antialiasing strategy should be included. However, seismic survey design using a random distribution of shots and receivers is always operationally challenging and impractical. We have used deep-learning-based approaches for seismic data antialiasing interpolation, which could extract deeper features of the training data in a nonlinear way by self-learning. It can also avoid linear events, sparsity, and low-rank assumptions of the traditional interpolation methods. Based on convolutional neural networks, eight-layers residual learning networks (ResNets) with a better back-propagation property for deep layers is designed for interpolation. Detailed training analysis is also performed. A set of simulated data is used to train the designed ResNets. The performance is assessed with several synthetic and field data. Numerical examples indicate that the trained ResNets can help to reconstruct regularly missing traces with high accuracy. The interpolated results in the time-space domain and the frequency-wavenumber (f-k) domain demonstrate the validity of the trained ResNets. Even though the accuracy decreases with the increase of the feature difference between the test and training data, the proposed method can still provide reasonable interpolation results. Finally, the trained ResNets is used to reconstruct dense data with halved trace intervals for synthetic and field data. The reconstructed dense data are more continuous along the spatial direction, and the spatial aliasing effects disappear in the f-k domain. The reconstructed dense data have the potential to improve the accuracy of subsequent seismic data processing and inversion.

The vast Indo-Gangetic Plain in South Asia has been home to some of the world's oldest civilizations, whose fortunes ebbed and flowed with time-plausibly driven in part by shifts in the spatiotemporal patterns of the Indian summer monsoon rainfall. We use speleothem oxygen isotope records from North India to reconstruct the monsoon's variability on socially relevant time scales, allowing us to examine the history of civilization changes in the context of varying hydroclimatic conditions over the past 5700 years. Our data suggest that significant shifts in monsoon rainfall have occurred in concert with changes in the Northern Hemisphere temperatures and the discharges of the Himalayan rivers. The close temporal relationship between these large-scale hydroclimatic changes and the intervals marking the significant sociopolitical developments of the Indus Valley and Vedic civilizations suggests a plausible role of climate change in shaping the important chapters of the history of human civilization in the Indian subcontinent.

Results of clay mineralogy, major element geochemistry, and Sr and Nd isotopes in 93 argillaceous samples collected from drainage basins of the Pearl, Red, and Mekong rivers reveal different degrees of chemical weathering in Southeast Asia despite similar climate conditions across these regions. The kaolinite/illite ratio, illite chemistry index, and illite crystallinity can be used as indicators of chemical weathering intensity. These mineralogical proxies combined with the K2O/(Na2O + CaO) molar ratio, chemical index of alteration (CIA), and weathering trends observed from major element results indicate intensive silicate weathering in the Pearl River basin, moderate to intensive in the Mekong River basin, and moderate in the Red River basin. Although a significant modification of ɛNd(0) values in our riverine sediments during chemical weathering and transport is unlikely,87Sr/86Sr ratios are controlled by various states of chemical weathering of high‐Sr minerals such as plagioclase (rich in Na and Ca) with a linear decrease trend from the Pearl, Mekong, to Red river basins. Our results suggest that it is not the warm climate with heavy monsoon precipitation but tectonics playing the most significant role in controlling weathering and erosion processes in south China and Indochina Peninsula. Strong physical erosion caused by tectonic activities and river incision along the eastern margin of the Tibetan Plateau and along the Red River fault system is responsible for high contents of primary minerals in the lowlands of Red and Mekong river basins.

The Indian summer monsoon (ISM) monsoon is critical to billions of people living in the region. Yet, significant debates remain on primary ISM drivers on millennial-orbital timescales. Here, we use speleothem oxygen isotope (δ(18)O) data from Bittoo cave, Northern India to reconstruct ISM variability over the past 280,000 years. We find strong coherence between North Indian and Chinese speleothem δ(18)O records from the East Asian monsoon domain, suggesting that both Asian monsoon subsystems exhibit a coupled response to changes in Northern Hemisphere summer insolation (NHSI) without significant temporal lags, supporting the view that the tropical-subtropical monsoon variability is driven directly by precession-induced changes in NHSI. Comparisons of the North Indian record with both Antarctic ice core and sea-surface temperature records from the southern Indian Ocean over the last glacial period do not suggest a dominant role of Southern Hemisphere climate processes in regulating the ISM variability on millennial-orbital timescales.

The chemical index of alteration (CIA) and elemental ratios that are sensitive to chemical weathering, such as Ca/Ti, Na/Ti, Al/Ti, Al/Na, Al/K, and La/Sm, were analyzed for detrital sediments at Ocean Drilling Program Site 1148 from the northern South China Sea to reveal information of chemical weathering in the source regions during the early Miocene. High CIA values of ∼80, coupled with high Al/Ti and Al/Na and low Na/Ti and Ca/Ti, are observed for the sediments at ∼23 Ma, indicating a high chemical weathering intensity in the north source region, i.e., south China. This was followed by gradual decreases in Al/Ti, Al/Na, La/Sm, and Al/K ratios, as well as the CIA values, and increases in Ca/Ti and Na/Ti ratios. These records together with other paleoclimate proxies, such as black carbon δ13C and benthic foraminifer δ18O, give reliable information on the climate changes in south China. Our results show that the climate in south China was warm and humid in the early Miocene (∼23 Ma) according to the chemical weathering records. The humidity in south China decreased from the early Miocene to Present with several fluctuations centering at approximately 15.7 Ma, 8.4 Ma, and 2.5 Ma, coincident with the global cooling since the middle Miocene. These climate changes implied that the summer east Asian monsoon has dramatically affected south China in the early Miocene, whereas the influence of the summer monsoon on this region has decreased continuously since that time, probably because of the intensification of the winter monsoon. Such an evolution for the east Asian monsoon is different from that for the Indian monsoon.

The Rehai and Ruidian geothermal fields, located in Tengchong County, Yunnan Province, China, host a variety of geochemically distinct hot springs. In this study, we report a comprehensive, cultivation-independent census of microbial communities in 37 samples collected from these geothermal fields, encompassing sites ranging in temperature from 55.1 to 93.6°C, in pH from 2.5 to 9.4, and in mineralogy from silicates in Rehai to carbonates in Ruidian. Richness was low in all samples, with 21-123 species-level OTUs detected. The bacterial phylum Aquificae or archaeal phylum Crenarchaeota were dominant in Rehai samples, yet the dominant taxa within those phyla depended on temperature, pH, and geochemistry. Rehai springs with low pH (2.5-2.6), high temperature (85.1-89.1°C), and high sulfur contents favored the crenarchaeal order Sulfolobales, whereas those with low pH (2.6-4.8) and cooler temperature (55.1-64.5°C) favored the Aquificae genus Hydrogenobaculum. Rehai springs with neutral-alkaline pH (7.2-9.4) and high temperature (>80°C) with high concentrations of silica and salt ions (Na, K, and Cl) favored the Aquificae genus Hydrogenobacter and crenarchaeal orders Desulfurococcales and Thermoproteales. Desulfurococcales and Thermoproteales became predominant in springs with pH much higher than the optimum and even the maximum pH known for these orders. Ruidian water samples harbored a single Aquificae genus Hydrogenobacter, whereas microbial communities in Ruidian sediment samples were more diverse at the phylum level and distinctly different from those in Rehai and Ruidian water samples, with a higher abundance of uncultivated lineages, close relatives of the ammonia-oxidizing archaeon "Candidatus Nitrosocaldus yellowstonii", and candidate division O1aA90 and OP1. These differences between Ruidian sediments and Rehai samples were likely caused by temperature, pH, and sediment mineralogy. The results of this study significantly expand the current understanding of the microbiology in Tengchong hot springs and provide a basis for comparison with other geothermal systems around the world.

Abstract Coring/logging data and physical property measurements from International Ocean Discovery Program Expedition 349 are integrated with, and correlated to, reflection seismic data to map seismic sequence boundaries and facies of the central basin and neighboring regions of the South China Sea. First‐order sequence boundaries are interpreted, which are Oligocene/Miocene, middle Miocene/late Miocene, Miocene/Pliocene, and Pliocene/Pleistocene boundaries. A characteristic early Pleistocene strong reflector is also identified, which marks the top of extensive carbonate‐rich deposition in the southern East and Southwest Subbasins. The fossil spreading ridge and the boundary between the East and Southwest Subbasins acted as major sedimentary barriers, across which seismic facies changes sharply and cannot be easily correlated. The sharp seismic facies change along the Miocene‐Pliocene boundary indicates that a dramatic regional tectonostratigraphic event occurred at about 5 Ma, coeval with the onsets of uplift of Taiwan and accelerated subsidence and transgression in the northern margin. The depocenter or the area of the highest sedimentation rate switched from the northern East Subbasin during the Miocene to the Southwest Subbasin and the area close to the fossil ridge in the southern East Subbasin in the Pleistocene. The most active faulting and vertical uplifting now occur in the southern East Subbasin, caused most likely by the active and fastest subduction/obduction in the southern segment of the Manila Trench and the collision between the northeast Palawan and the Luzon arc. Timing of magmatic intrusions and seamounts constrained by seismic stratigraphy in the central basin varies and does not show temporal pulsing in their activities.

Summary Wound area changes over multiple weeks are highly predictive of the wound healing process. A big data eHealth system would be very helpful in evaluating these changes. We usually analyze images of the wound bed for diagnosing injury. Unfortunately, accurate measurements of wound region changes from images are difficult. Many factors affect the quality of images, such as intensity inhomogeneity and color distortion. To this end, we propose a fast level set model‐based method for intensity inhomogeneity correction and a spectral properties‐based color correction method to overcome these obstacles. State‐of‐the‐art level set methods can segment objects well. However, such methods are time‐consuming and inefficient. In contrast to conventional approaches, the proposed model integrates a new signed energy force function that can detect contours at weak or blurred edges efficiently. It ensures the smoothness of the level set function and reduces the computational complexity of re‐initialization. To increase the speed of the algorithm further, we also include an additive operator‐splitting algorithm in our fast level set model. In addition, we consider using a camera, lighting, and spectral properties to recover the actual color. Numerical synthetic and real‐world images demonstrate the advantages of the proposed method over state‐of‐the‐art methods. Experimental results also show that the proposed model is at least twice as fast as methods used widely. Copyright © 2016 John Wiley & Sons, Ltd.

First-order relationships between organic matter content and mineral surface area have been widely reported and are implicated in stabilization and long-term preservation of organic matter. However, the nature and stability of organomineral interactions and their connection with mineralogical composition have remained uncertain. In this study, we find that continentally derived organic matter of pedogenic origin is stripped from smectite mineral surfaces upon discharge, dispersal, and sedimentation in distal ocean settings. In contrast, organic matter sourced from ancient rocks that is tightly associated with mica and chlorite endures in the marine realm. These results imply that the persistence of continentally derived organic matter in ocean sediments is controlled to a first order by phyllosilicate mineralogy.

Silicate weathering as an important negative feedback can regulate the Earth's climate over time, but much debate concerns its response strength to each climatic factor and its evolution with land surface reorganisation. Such discrepancy arises from lacking weathering proxy validation and scarce quantitative paleo-constraints on individual forcing factors. Here we examine the catchment-scale link of silicate weathering intensity with various environmental parameters using a global compilation of modern sediment dataset (n = 3828). We show the primary control of temperature on silicate weathering given the monotonic increase of feldspar dissolution with it (0-30 °C), while controls of precipitation or topographic-lithological factors are regional and subordinate. We interpret the non-linear forcing of temperature on feldspar dissolution as depletion of more reactive plagioclase (relative to orthoclase) at higher temperature. Our results hint at stronger temperature-weathering feedback at lower surface temperature and support the hypothesis of increased land surface reactivity during the late Cenozoic cooling.

The Tibetan Plateau in Northwest China hosts a number of hot springs that represent a biodiversity hotspot for thermophiles, yet their diversity and relationship to environmental conditions are poorly explored in these habitats. In this study we investigated microbial diversity and community composition in 13 Tibetan hot springs with a wide range of temperatures (22.1-75°C) and other geochemical conditions by using the 16S rRNA gene pyrosequencing approach. Bacteria (10(8)-10(11) copy/g; 42 bacterial phyla) in Tibetan hot springs were more abundant and far more diverse than Archaea (10(7)-10(10) copy/g; 5 archaeal phyla). The dominant bacterial phyla systematically varied with temperature. Moderate temperatures (75-66°C) favored Aquificae, GAL35, and novel Bacteria, whereas low temperatures (60-22.1°C) selected for Deinococcus-Thermus, Cyanobacteria, and Chloroflexi. The relative abundance of Aquificae was correlated positively with temperature, but the abundances of Deinococcus-Thermus, Cyanobacteria, and Chloroflexi were negatively correlated with temperature. Cyanobacteria and Chloroflexi were abundant in Tibetan hot springs and their abundances were positively correlated at low temperatures (55-43°C) but negatively correlated at moderate temperatures (75-55°C). These correlation patterns suggest a complex physiological relationship between these two phyla. Most archaeal sequences were related to Crenarchaeota with only a few related to Euryarchaeota and Thaumarchaeota. Despite the fact that microbial composition in Tibetan hot springs was strongly shaped by temperature, microbial diversity (richness, evenness and Shannon diversity) was not significantly correlated with temperature change. The results of this study expand our current understanding of microbial ecology in Tibetan hot springs and provide a basis for a global comparison.

• No significant directional changes of annual streamflow downward TGD over century. • River discharge hydrographs change by reduced peak and slightly increased low discharges. • The TGD accelerates the sediment load reduction trend dating back to 1980s. • Altered river–lake interplay leads to seasonal low water in the lakes. Streamflow and sediment loads undergo remarkable changes in worldwide rivers in response to climatic changes and human interferences. Understanding their variability and the causes is of vital importance regarding river management. With respect to the Changjiang River (CJR), one of the largest river systems on earth, we provide a comprehensive overview of its hydrological regime changes by analyzing long time series of river discharges and sediment loads data at multiple gauge stations in the basin downstream of Three Gorges Dam (TGD). We find profound river discharge reduction during flood peaks and in the wet-to-dry transition period, and slightly increased discharges in the dry season. Sediment loads have reduced progressively since 1980s owing to sediment yield reduction and dams in the upper basin, with notably accelerated reduction since the start of TGD operation in 2003. Channel degradation occurs in downstream river, leading to considerable river stage drop. Lowered river stages have caused a ‘draining effect’ on lakes by fostering lake outflows following TGD impoundments. The altered river–lake interplay hastens low water occurrence inside the lakes which can worsen the drought given shrinking lake sizes in long-term. Moreover, lake sedimentation has decreased since 2002 with less sediment trapped in and more sediment flushed out of the lakes. These hydrological changes have broad impacts on river flood and drought occurrences, water security, fluvial ecosystem, and delta safety.

Harmful algal blooms (HABs) are severe ecological disasters threatening aquatic systems throughout the World, which necessitate scientific efforts in detecting and monitoring them. Compared with traditional in situ point observations, satellite remote sensing is considered as a promising technique for studying HABs due to its advantages of large-scale, real-time, and long-term monitoring. The present review summarizes the suitability of current satellite data sources and different algorithms for detecting HABs. It also discusses the spatial scale issue of HABs. Based on the major problems identified from previous literature, including the unsystematic understanding of HABs, the insufficient incorporation of satellite remote sensing, and a lack of multiple oceanographic explanations of the mechanisms causing HABs, this review also attempts to provide a comprehensive understanding of the complicated mechanism of HABs impacted by multiple oceanographic factors. A potential synthesized framework can be established by combining multiple accessible satellite remote sensing approaches including visual interpretation, spectra analysis, parameters retrieval and spatial-temporal pattern analysis. This framework aims to lead to a systematic and comprehensive monitoring of HABs based on satellite remote sensing from multiple oceanographic perspectives.

Marine Group (MG) I (currently known as Thaumarchaeota) and MG II Archaea were first reported over two decades ago. While significant progress has been made on MG I microbiology and ecology, the progress on MG II has been noticeably slower. The common understanding is that while MG I mainly function as chemolithoautotrophs and occur predominantly in the deep ocean, MG II reside mostly in the photic zone and live heterotrophically. Studies to date have shown that MG II are abundant in the marine aquatic environment and display great seasonal and spatial variation and phylogenetic diversity. They also show unique patterns of organic carbon degradation and their energy requirements may be augmented by light in the photic zone. However, no pure culture of MG II has been obtained and thus their precise ecological role remains elusive.

Using a culture-independent method that combines CARD-FISH, qPCR and 16S rDNA, we investigated the abundance, community structure and diversity of microbes along a steep thermal gradient (50-90 °C) in the Tengchong Geothermal Field. We found that Bacteria and Archaea abundance changed markedly with temperature changes and that the number of cells was lowest at high temperatures (90.8 °C). Under low-temperature conditions (52.3-74.6 °C), the microbial communities were dominated by Bacteria, which accounted for 60-80% of the total number of cells. At 74.6 °C, Archaea were dominant, and at 90.8 °C, they accounted for more than 90% of the total number of cells. Additionally, the microbial communities at high temperatures (74.6-90.8 °C) were substantially simpler than those at the low-temperature sites. Only a few genera (e.g., bacterial Caldisericum, Thermotoga and Thermoanaerobacter, archaeal Vulcanisaeta and Hyperthermus) often dominated in high-temperature environments. Additionally, a positive correlation between Ammonia-Oxidizing Archaea (AOA) activity and temperature was detected. AOA activity increased from 17 to 52 pmol of NO2(-) per cell d(-1) with a temperature change from 50 to 70 °C.

Drilling has revealed suites of magnesian granite and diorite emplaced in Early Jurassic time (198–195 Ma) and an arc-related low-temperature (678 to 696°C) magmatism in NE South China Sea. These rocks have 87Sr/86Sri (0.705494 to 0.706623) and εNdt (−0.9 to +2.2) as evidence of evolved mantle-derived magmas, coupled with enriched fluid-mobile elements Cs to K and Pb implying involvement of subduction-zone fluids. Another Early Jurassic granodiorite (zircon U-Pb 187 Ma) drilled from the SW East China Sea, a magnesian high-K calc alkaline, is comparably confined to a range of low-temperature (~675°C) arc-related granite, characterized by enrichment of fluid-mobile elements and Nb-Ta depletion. Its Sr-Nd isotopes (87Sr/86Sri = 0.705200, εNdt = 1.1) suggest a product of evolved mantle-derived melts. Together with detrital igneous zircons from Paleocene sequences, these observations reveal an Early Jurassic arc-related low-temperature (600 to 740°C) magmatism in the SW East China Sea. These arc-related granitoids, along with those from SE Taiwan, could define an Early Jurassic NE-SW trending Dongsha-Talun-Yandang magmatic arc zone along the East Asian continental margin paired with Jurassic accretionary complexes from SW Japan, East Taiwan to the West Philippines. This arc-subduction complex assembly was associated with oblique subduction of the paleo-Pacific slab beneath Eurasia, presumably responsible for Early Jurassic lithospheric extension in south China block.

Abstract Millennial-scale variations of the East Asian winter monsoon (EAWM) remain elusive due to sparse and controversial reconstructions. By compiling a variety of alkenone-based sea surface temperature (SST) estimates, we find that the west–east SST gradient in the southern South China Sea (SCS) well documents the temporal dynamics of the winter “cold tongue” off the southern Vietnam and by inference, variations in the EAWM intensity over the past 26 ka. Our results reveal that the winter “cold tongue” SSTs were significantly colder during Heinrich event 1 and the Younger Dryas event, resulting in an increased west–east SST gradient in the southern SCS due to a strengthened EAWM. Within dating uncertainties, an intensified EAWM during cold stadials was coeval with the shutdown or a reduction in strength of the Atlantic meridional overturning circulation (AMOC), exhibiting a strong linkage between the AMOC and the EAWM system. The west–east SST gradient also indicates an enhanced EAWM during the early Holocene, which may be induced by postglacial ice-sheet dynamics and a strong seasonal contrast in solar insolation. Our findings suggest that the EAWM was probably modulated by a complex interplay between the AMOC, solar insolation and ice-sheet dynamics on sub-orbital time scales.