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The escalating evolution of aquaculture has wielded a profound and far-reaching impact on regional sustainable development, ecological equilibrium, and food security. Currently, most aquaculture mapping efforts mainly focus on coastal aquaculture ponds rather than diverse inland aquaculture areas. Recognizing all types of aquaculture areas and accurately classifying different types of aquaculture areas remains a challenge. Here, on the basis of the Google Earth Engine (GEE) and the time-series Sentinel-1 and -2 data, we developed a novel hierarchical framework extraction method for mapping fine inland aquaculture areas (aquaculture ponds + rice-crawfish fields) by employing distinct phenological disparities within two temporal windows (T1 and T2) in Qianjiang, so-called “Home of Chinese Crawfish”. Simultaneously, we evaluated the classification performance of four distinct machine learning classifiers, namely Random Forest (RF), Support Vector Machine (SVM), Classification and Regression Trees (CART), and Gradient Boosting (GTB), as well as 11 feature combinations. Following an exhaustive comparative analysis, we selected the optimal machine learning classifier (i.e., the RF classifier) and the optimal feature combination (i.e., feature combination after an automated feature selection method) to classify the aquaculture areas with high accuracy. The results underscore the robustness of the proposed methodology, achieving an outstanding overall accuracy of 93.8%, with an F1 score of 0.94 for aquaculture. The result indicates that an area of 214.6 ± 10.5 km2 of rice-crawfish fields, constituting approximately 83% of the entire aquaculture area in Qianjiang, followed by aquaculture ponds (44.3 ± 10.7 km2, 17%). The proposed hierarchical framework, based on significant phenological characteristics of varied aquaculture types, provides a new approach to monitoring inland freshwater aquaculture in China and other regions of the world.

Abstract The Jurassic sequences in the South Qiangtang Basin of Tibet are essential for understanding the paleogeography and tectonic evolution of this basin and the Bangong-Nujiang Meso-Tethys Ocean (BNMO). However, the partial absence of fossils hinders the study of the stratigraphic distribution and tectonic paleogeography of the basin. Late Triassic bivalves, including nine species in nine genera, were identified for the first time in olistostromes from the Sêwa Formation in the Riganpeicuo area. Based on detailed geological field surveys and sedimentary facies analysis, the lower-middle part of the Rigenco section is a deep-water turbidite fan deposit and the upper part is a shallow sea mixed shelf deposit, which differs distinctively from the carbonate platform facies of the Jiebuqu Formation. Therefore, the strata formerly assigned to the Jiebuqu Formation (Rigenco section) is formally reassigned to the Lower-Middle Jurassic Sêwa Formation and Middle Jurassic Shaqiaomu Formation. These results not only provide further understanding of the sedimentary infill history of the South Qiangtang Basin, but also further support that the BNMO was already open in the Late Triassic and formed a mature ocean in the Early-Middle Jurassic, with subsequent rapid subduction. Both the opening and subduction processes were completed in a relatively short time interval with a large number of attendant olistostromes.

Introduction: The Bangong-Nujiang Suture Zone (BNSZ) in central Tibet is a remnant of the Bangong-Nujiang Ocean that records its entire Wilson Cycle. The model of divergent double-sided subduction (DDS) is crucial for elucidating the evolution of tectonomagmatic activity on both sides of the BNSZ and for understanding why no high-pressure metamorphic rocks occur in the BNSZ. However, the DDS geodynamics remain poorly constrained. In particular, there is a lack of reports on magmatic rocks directly associated with slab sinking in the DDS terminal stage.Methods: This study presents new geochronological, geochemical, and isotopic data for the Early Cretaceous bimodal volcanic rocks around the Wuga Co area.Results: The bimodal volcanic rocks are divided into the Wuga Co rhyolites (SiO2 = 77.0–79.0 wt%) and the Wuga Co basaltic andesites (SiO2 = 53.9–55.5 wt%). The isotopic values of the Wuga Co basaltic andesites with low (87Sr/86Sr)i values (+0.7040 to +0.7044) and high εNd(t) values (+3.8 to +4.1) lie among three endmembers (the BNO sediments in accretionary wedge, depleted mantle and the BNO slab).Discussion: These values indicate the partial melting of a mantle peridotite that interacted with the subducted slab and sediment in the accretionary wedge, which was caused by the sinking of the Bangong-Nujiang oceanic slab. The Wuga Co rhyolites (108 Ma) have low (87Sr/86Sr)i values (+0.703 to +0.706), high εNd(t) values (+2.25 to +2.49), and high εHf(t) values (+5.6 to +10.0). These values indicate that the rhyolite formed by partial melting of juvenile basaltic crust. This study also collected Hf isotope data from both sides of the BNSZ to constrain its evolution. Our results show that the εHf(t) values of magma on both sides of the BNSZ were elevated simultaneously at 130 Ma, which may be caused by the Bangong-Nujiang oceanic slab rupture. Based on these new data, we propose that the Bangong-Nujiang oceanic slab ruptured from the two overlying terranes at approximately 130 Ma and subsequently sank into the mantle at approximately 108 Ma.

Investigation of intra-oceanic subduction can improve our understanding of plate tectonic processes and the history of continental growth. Evidence for intra-oceanic subduction in the Paleo-Asian Ocean has recently become an important focus of research, including the Diyanmiao ophiolite in central Inner Mongolia, North China. Here, we report a newly discovered occurrence of early Permian gabbro in the Diyanmiao ophiolite zone. The gabbro yields a weighted mean zircon U–Pb age of 294.4 ± 2.2 Ma. The gabbro samples are characterized by moderate SiO2 (47.32–50.51 wt%), low TiO2 (0.26–0.54 wt%) and K2O (0.04–0.75 wt%), and high Na2O (1.84–4.52 wt%) contents, high Na2O/K2O ratios (2.92–58.29), and depleted chondrite-normalized light rare Earth element patterns that are similar to N-MORB. The gabbros show slightly lower contents of high-field-strength elements (e.g., Nb, Ta, and Ti) and slightly higher contents of large-ion lithophile elements (e.g., K, Rb, Ba, and U) relative to N-MORB. In addition, the gabbros show high εNd (t) values (8.0–9.8) that are similar to those of forearc basalt in the Diyanmiao ophiolite and N-MORB. Integrating these new data with available results for ophiolite and arc-magmatic rocks of central Inner Mongolia, we propose that the studied gabbro was formed during the initial stage of intra-oceanic subduction and that the Paleo-Asian Ocean was still in a subduction setting during the early Permian.

The Cuonadong Dome is located at the eastern part of the North Himalayan gneiss domes. Structural and kinematic analysis in the middle unit of the Cuonadong Dome provide significant new insights into the structural deformation of the middle crust in the Northern Himalaya. Field observations, microscopic kinematic and EBSD analyses, and deformation temperature estimates from the mid-crustal rocks of the Cuonadong Dome show high-strain D2 (top-to-N) kinematic fabrics with a downward-to-north progression from dominantly top-to-north shear in the garnet zone, to solely top-to-north shear in the kyanite/sillimanite zone. A combination of mineral assemblages, microstructures, and quartz crystal preferred orientation patterns indicates deformation temperatures associated with D2 kinematic fabrics increase with structural depth from ∼450 °C in garnet zone to > 630 °C in the kyanite/sillimanite zone. These values broadly overlap temperature range deduced from metamorphic petrography (450–630 °C). Microtextural relations indicate that peak metamorphism occurred post-D1 and pre-D2 deformation. Combined with the ∼1000-m-thick ductile deformation zone, the interpreted deformation temperatures yielded an average thermal field gradient of ∼ 180 °C/km over 1.05 km of structural thickness. Based on the geochronologic data, midcrustal D2 extensional deformation in the Cuonadong Dome initiated as early as early Oligocene (32 Ma) and ended during the middle Miocene (∼14 Ma). Comparative studies of D2 ductile deformation in midcrustal rocks from other North Himalayan gneiss domes and the South Tibetan Detachment System indicate that D2 shear zone in the Cuonadong Dome represent the northern part of the South Tibetan Detachment System, and highlight temporal and spatial variation in midcrustal D2 deformation patterns over the southern Tibet during the Himalayan orogeny.

This study was conducted to explore the distribution and changes of groundwater resources in the research area, and to promote the application of geographic information system (GIS) technology and its deep learning methods in chemical type distribution and water quality prediction of groundwater. The Shiyang River Basin in Minqin County was selected as the research object for analyzing the natural components distribution and its preliminary forecast in partial areas. With the priority control of groundwater pollutants, the concentration changes of four indicators (including the permanganate index) in different spatial distributions were analyzed based on the GIS technology, so as to provide a basis for the groundwater quality prediction. Taking the permanganate as a benchmark, this study evaluated the prediction effects of the conventional back propagation (BP) neural network (BPNN) model and the optimized BPNN based on the golden section (GBPNN) and wavelet transform (WBPNN). The algorithm proposed in this study is compared with several classic prediction algorithms for analysis. Groundwater quality level and distribution rules in the research area are evaluated with the proposed algorithm and GIS technology. The results reveal that GIS technology can characterize the spatial concentration distribution of natural indicators and analyze the chemical distribution of groundwater quality based on it. In contrast, the WBPNN has the best prediction result. Its average error of the whole process is 3.66%, and the errors corresponding to the six predicated values are all below 10%, which is dramatically better than the values of the other two models. The maximal prediction accuracy of the proposed algorithm is 97.68%, with an average accuracy of 96.12%. The prediction results on the water quality level are consistent with the actual condition, and the spatial distribution rules of the groundwater water quality can be shown clearly with the GIS technology combined with the proposed algorithm. Therefore, it is of great significance to explore the distribution and changes of regional groundwater quality, and this studywill play a critical role in determining the groundwater quality.

Deciphering the exhumation mechanism of high-pressure--low-temperature (HP-LT) metamorphic rocks can provide important insights into the tectonic evolution of oceanic subduction zones at active continental margins. Here, we present a multidisciplinary study examining the exhumation tectonics of the Permo--Triassic eclogite-bearing HPLT terranes of the Central Qiangtang metamorphic belt (CQMB) in the central Tibetan Plateau. Field geological relations and microscopic observations show that the HP-LT rocks in the Lanling area are separated from the epimetamorphic late Paleozoic ophiolite mélange of the hanging wall by low-angle detachment faults and primarily exhibit five stages of deformation. The HP-LT terranes were exhumed as a metamorphic core complex and show pervasive synexhumation top-to-the-SW and -S shear structures. The results of the petrological and mineralogical analysis and pseudosection modeling of retrograde eclogites indicate that these rocks are characterized by synexhumation mineral growth pulses with hairpin-type decompressional pressure-temperature trajectories. A compilation of previous geochronological data and our 40Ar/39Ar dating results of synexhumation minerals and shear bands in HP-LT rocks indicates continuous exhumation at ca. 244-215 Ma prior to the continental collision between the North Qiangtang Block (NQB) and South Qiangtang Block. Moreover, the CQMB is likely an autochthonous accretionary wedge resulting from northward subduction of the Paleo-Tethys Ocean beneath the NQB. Combined with ca. 243-230 Ma mantle upwelling to the north of Lanling, we infer that the CQMB, namely, the accretionary wedge of the Paleo-Tethys Ocean, experienced Middle--Late Triassic lithospheric extension in the NW-SE direction. [ABSTRACT FROM AUTHOR]

The Upper Carboniferous Zhanjin Formation has attracted much attention from geoscientists for containing glacial-marine diamictite and cold-water fauna typified by the bivalve Eurydesma. The presence of this Formation has provided important evidence for determining the northern border of Gondwana. Previous researchers have classified those strata north of Niangrong Co in the Gêrzê region as part of the Zhanjin Formation based on the presence of glacial-marine diamictite, although the absence of biological fossil evidence has defied clear age determination. Our field investigations first discovered large quantities of corals, sponges and bryozoans. All coral fossils were identified as belonging to the Hexacorallia subclass including 13 genera and 25 species, primarily including Conophyllia guiyangensis Deng et Kong, Coryphyllia regularis Cuif, Cuifia columnaris Roniewicz, Distichophyllia norica Freeh, Distichophyllia gigas Vinassa de Regny, Pamiroseris rectilamellosa Winkler, Retiophyllia clathrata Emmrich, and Retiophyllia paraclathrata Roniewicz. Extensive biostratigraphic correlations show that the hexacorallia should belong to the Late Triassic, thereby negating the presence of the Zhanjin Formation in the study area. Based on analyses of sedimentary facies and detailed study of the glacial-marine diamictite as supposed by earlier researchers, the limestone blocks and gravels within the facies are slope facies olistostromes and waterway sediments from lime slurry debris flows in the submarine fan rather than primary sedimentary products. Among them, lenticular sandstone should be sequentially distributed waterway sand bodies, indicating that the strata have no glacial-marine diamictite. In addition, the rocks containing the mentioned fossils are just limestone blocks from olistostromes, and limestone gravels from waterways of submarine fans. Such a result further negates the presence of the Zhanjin Formation in the study area, and indicates that the age of the studied strata should be youner than the Late Triassic. Through regional stratigraphic comparisons and the study of tectonic settings of the strata, the sedimentary characteristics of the subject strata, including lithology, lithofacies and fossils, are confirmed to be similar to the widely distributed Sêwa Formation in this region. We thus infer that the strata belong to the Middle-Lower Jurassic Sêwa Formation. This finding is important for both studying paleogeography of Tibet and determining the northern boundary of Gondwana. [ABSTRACT FROM AUTHOR]

There have been divergent opinions on whether Conophyllia develops synapticulae and dissepiments since its erection in 1849, with different views existing on the morphology of columella in Conophyllia. This paper presents a comprehensive review of Conophyllia, and revises the diagnosis according to new material from the Renacuo area of Gêrzê, Tibet. The revised diagnosis emphasises the following features: solitary coral; abundant radial elements subequal in thickness, lateral faces with granules and synapticulae; parietal, papillar or incompact columella, a few species lacking in columella; developed dissepiments. Individuals of Conophyllia have laminar septa of Triadophyllum type in earlier ontogenetic stages, while their septa in later ontogenetic stages are more fenestrate. The geological and geographical distribution of this genus is discussed, with five species of Conophyllia from the Renacuo area of Gêrzê, Tibet being described and illustrated, including one new species and two in open nomenclatue. [ABSTRACT FROM AUTHOR]

The diversity of archaea and bacteria was investigated in ten hot springs (elevation >4600 m above sea level) in Central and Central-Eastern Tibet using 16S rRNA gene phylogenetic analysis. The temperature and pH of these hot springs were 26-81°C and close to neutral, respectively. A total of 959 (415 and 544 for bacteria and archaea, respectively) clone sequences were obtained. Phylogenetic analysis showed that bacteria were more diverse than archaea and that these clone sequences were classified into 82 bacterial and 41 archaeal operational taxonomic units (OTUs), respectively. The retrieved bacterial clones were mainly affiliated with four known groups (i.e., Firmicutes, Proteobacteria, Cyanobacteria, Chloroflexi), which were similar to those in other neutral-pH hot springs at low elevations. In contrast, most of the archaeal clones from the Tibetan hot springs were affiliated with Thaumarchaeota, a newly proposed archaeal phylum. The dominance of Thaumarchaeota in the archaeal community of the Tibetan hot springs appears to be unique, although the exact reasons are not yet known. Statistical analysis showed that diversity indices of both archaea and bacteria were not statistically correlated with temperature, which is consistent with previous studies. [ABSTRACT FROM AUTHOR]

The article compares the composition of polybrominated biphenyl ethers (PBDEs) found in Tibet with those in East China, and the methods by which PBDEs are transformed after being absorbed by the soil. It relates that PBDEs typically have 209 congers, with the number of bromine atoms varying from 1 to 10. It reveals that PBDEs in Tibet undergo photo-degradation by the catalysis of clay in soils while in China, PBDE high congers are catalyzed into light ones after absorption into the soil.

The article presents a comprehensive structural analysis of the Mesozoic-Cenozoic basement of the South Qiangtang Basin (SQTB) in Tibet. Based on large-scale mapping and the isotopic geochronology of the Gemuri, Nierong, Jitang and Jiayuqiao metamorphic complexes, it indicates that the SQTB basement is primarily composed of Paleozoic subduct-accretionary complex rock formed during the Indosinian epoch collisional orogenesis.