Burial Processes Research Articles

Deconvolving the Fate of Carbon in Coastal Sediments

AbstractCoastal oceans play a crucial role in the global carbon cycle, and are increasingly affected by anthropogenic forcing. Understanding carbon cycling in coastal environments is hindered by convoluted sources and myriad processes that vary over a range of spatial and temporal scales. In this study, we deconvolve the complex mosaic of organic carbon manifested in Chinese Marginal Sea (CMS) sediments using a novel numerical clustering algorithm based on 14C and total OC content. Results reveal five regions that encompass geographically distinct depositional settings. Complementary statistical analyses reveal contrasting region‐dependent controls on carbon dynamics and composition. Overall, clustering is shown to be highly effective in demarcating areas of distinct organic facies by disentangling intertwined organic geochemical patterns resulting from superimposed effects of OC provenance, reworking and deposition on a shelf region exhibiting pronounced spatial heterogeneity. This information will aid in constraining region‐specific budgets of carbon burial and carbon cycle processes.

Burial process and features of Yangsan Bubuchong : A Review

Burial process and features of Yangsan Bubuchong : A Review

Portable NIR Raman microspectroscopy investigation on Early Bronze IV pottery (2500–1950 BCE) from Khirbat Iskandar, Jordan

Portable Near Infrared Micro-Raman (NIR μ-Raman) spectroscopy was used, as a preliminary and non-destructive technique, in order to investigate the mineralogical composition of a group of pottery sherds from Khirbat Iskandar, Jordan. Preliminary results show that the ceramic body is composed mainly of quartz, calcite, and minor amounts of feldspars and hematite. In addition, the presence of Olivine and anatase, important markers to identify the provenance of raw materials, was detected. Furthermore, the occurrence of Portlandite was related to both rehydration of calcite and burial alteration processes. Finally, a study of Raman spectrum of Amorphous Carbon, identified as temper in the clay, was performed to estimate the manufacturing parameters (maximum temperature and permanence time).

An Ediacaran opportunist? Characteristics of a juvenile Dickinsonia costata population from Crisp Gorge, South Australia

AbstractDespite 70 years of study, Dickinsonia remains one of the Ediacara biota’s most enigmatic taxa with both morphological characters and phylogenetic affinities still debated. A large population of relatively small Dickinsonia costata present on a semi-contiguous surface from the Crisp Gorge fossil locality in the Flinders Ranges (South Australia) provides an opportunity to investigate this taxon in its juvenile form. This population supports earlier findings that suggest D. costata’s early growth was isometric, based on the relationship between measured variables of length and width. The number of body units increases with length, but at a decreasing rate. A correlation between a previously described physical feature, present as a shrinkage rim partially surrounding some specimens and a novel, raised lip in some specimens, suggests that both features may have been the result of a physical contraction in response to the burial process, rather than due to a gradual loss of mass during early diagenesis. A marked protuberance in 15% of the population is also noted in limited specimens within the South Australian Museum collections and appears to be present only in juvenile D. costata. Both the abundance and narrow size range of this population support the notion that Dickinsonia was a hardy opportunist, capable of rapid establishment and growth on relatively immature textured organic-mat substrates.

Ternary analytic porosity-reduction model of sandstone compaction trend and its significance in petroleum geology: A case study of tight sandstones in Permian Lower Shihezi Formation of Shilijiahan area, Ordos Basin, China

The tight sandstones in the Permian Lower Shihezi Formation of Shilijiahan area in the Ordos Basin was taken as study object in this research to quantitatively determine the effects of burial depth, burial time and compaction strength on porosity during densification of reservoir. Firstly, sandstone compaction profiles were analyzed in detail. Secondly, the theoretical study was performed based on visco-elasto-plastic stress–strain model. Thirdly, multiple regression and iterative algorithm were used respectively to ascertain the variation trends of Young's modulus and equivalent viscosity coefficient with burial depth and burial time. Accordingly, the ternary analytic porosity-reduction model of sandstone compaction trend was established. Eventually, the reasonability of improved model was tested by comparing with thin-section statistics under microscope and the models in common use. The study shows that the new model can divide the porosity reduction into three parts, namely, elastic porosity loss, visco-plastic porosity loss and porosity loss from cementation. And the results calculated by the new model of litharenite in He 2 Member are close to the average value from the thin-section statistics on Houseknecht chart, which approximately reveals the relative magnitudes of compaction and cementation in the normal evolution trend of sandstone porosity. Furthermore, the model can more exactly depict the compaction trend of sandstone affected little by dissolution than previous compaction models, and evaluate sandstone compaction degree and its contribution to reservoir densification during different burial and uplift processes.

Initial porosity and compaction of consolidated sandstone in Hangjin Qi, North Ordos Basin

Compaction is an important part of diagenesis affecting porosity in conjunction with burial depth and time. However, the relation between initial porosity and sandstone compaction remains unclear. This paper aims to clarify the effect of initial porosity on the compaction of consolidated sandstone in the microdeformation stage via experiments, mathematical modeling, and statistical analyses. According to the physical experiments in the Ordos Basin, sandstone porosity decreases with increasing overburden load, and the porosity-decrease trends of two similar samples with different initial porosities converge gradually. Based on the Bingham visco-elasto-plastic stress–strain model, a theoretical model for the vertical uniaxial compaction of consolidated porous rocks was constructed. The equivalent viscosity coefficient (EVC) of consolidated sandstones was approximately estimated by a contrastive analysis and an iterative computation on the basis of the geologic statistical model proposed in this study. The results in Hangjin Qi show that the Young’s modulus and the EVC of low-porosity compaction trend (LPCT) are exponential and power-law functions of the corresponding porosity, respectively. The derivation of theoretical model indicates that the compressibility and the initial porosity of porous sandstone during microdeformation are positively correlated, in accordance with simulation experiments. The initial porosity affects the elastic modulus and the viscosity coefficient and consequently, the sandstone compaction during microdeformation stage. Such an effect can contribute to the improvements of both the compaction degree analyses of different burial processes in sandstone porosity evolution and reservoir quality evaluation.

Sources, distributions, and burial efficiency of terrigenous organic matter in surface sediments from the Yellow River mouth, northeast China

Organic geochemical studies of surface sediments from Laizhou Bay, the Yellow River mouth, northeast China, were conducted to reveal the sources, distributions, and burial efficiency of terrigenous OC exported by the Yellow River. Bulk OC contents and δ13Corg values from 204 samples show that terrigenous OC mainly accumulates in two muddy patches, basically controlled by hydrodynamic conditions. Distributions and stable carbon isotopic compositions of individual n-alkanes from 45 samples suggest that short-chain n-alkanes, with even carbon-number predominance, are most likely microbial products from degradation of riverine fossil OC, whereas long-chain odd-numbered n-alkanes (n-C27, n-C29 and n-C31) and long-chain even-numbered n-alkanes (n-C26,n-C28 and n-C30) are representative of riverine soil OC and fossil OC, respectively. Integrated with previous reports of ∼100% burial efficiency of soil OC in the Yellow River mouth, concentration ratios of n-C27+29+31 to OC and n-C26+28+30 to n-C27+29+31 from the riverine particles to surface sediments in Laizhou Bay were constructed to indicate relative terrigenous OC contributions and fossil OC burial efficiency, respectively. The results suggest that the terrigenous OC contribution ranges from 14% to 57% in Laizhou Bay, with the highest values in the two muddy patches as well as in areas near the river mouth. The fossil OC burial efficiency ranges from 36% to 76%, with an TOC-weighted mean value of 42%. The 58% fossil OC lost during the transport and burial processes in the Yellow River mouth may provide a significant CO2 source.

Aves de caza. Estudio tafonómico y zooarqueológico de los restos avianos de los niveles musterienses de Pié Lombard (Alpes-Maritimes, Francia)

espanolEl yacimiento musteriense de Pie Lombard (Alpes-Maritimes, Francia) esta localizado en un entorno montanoso de medio rango y posee un conjunto oseo rico y diversificado en el cual los restos de aves son abundantes. Su estudio tafonomico y zooarqueologico brinda cuestiones importantes sobre la explotacion de aves por parte de rapaces, carnivoros y neandertales, y anade otro yacimiento en el cual se lleva a cabo la explotacion de pequenas presas en Europa Occidental. EnglishTraditionally small fast game exploitation is characteristic of the end of Upper Palaeolithic or modern humans. Nevertheless, several authors demonstrated recently small fast game exploitation by fossil hominins able to capture, process and consume small animals for different purposes, despite numerous methodological and technical problems. In this work, we provide results of a taphonomical and zooarchaeological study on all bird bones from the Middle Palaeolithic levels of Pie Lombard using various analytical tools. The Mousterian site of Pie Lombard is a narrow rock shelter located in a middle-range mountainous environment near Tourrettes-sur-Loup (Alpes-Maritimes, France). The Middle Palaeolithic bird bone assemblage retained 18 taxa, all adults. The most represented taxa are choughs and pigeons that represent rocky species, characteristic of mild-temperate climate. The third most common specie is the partridge, although to a lesser extent. Long bones are predominant and anatomical representations are different between the frequent species. Various taphonomical alterations are visible on bird remains, including human modifications (cut marks -incisions and scraping marks- and burnt bones), other non-human predator activities (usually tooth marks and digestion processes) and some diagenetic alterations (especially concretion, corrosion and root marks). The majority of the bones are characterized by curved outline, mixed angles and jagged textures. The bird remains exhibit significant breakages due to various consumption processes (humans, raptors and small carnivores) completed by natural burial process. The birds of prey (probably nocturnal raptors) transported their prey (usually choughs) to the rock shelter where they were consumed and regurgitated. Secondly, small and medium-sized carnivores (small felids like lynx or wild cat had a relevant role) predate occasionally on birds. Neanderthals occupations were occasional, where they exploited herbivores but are also in to some extent at the source of bird accumulation. The humans captured almost exclusively pigeons and partridges, and some choughs. Without excluding a possible use of feathers, the Neanderthal groups of Pie Lombard acquired birds for their meat. Thus, Pie Lombard is a new Middle Paleolithic site where small game exploitation was a real part of the diet. The site can be is added to our recent knowledge, as another sites in Western Europe, demonstrating the ability of Neanderthal to hunt and consume birds as a continuous economic activity in space and time. euskaraPie Lombard-eko (Itsas Alpeak, Frantzia) aztarnategi mousteriarra maila ertaineko ingurune menditsuan dago, eta hezur-multzo aberatsa eta dibertsifikatua du. Oso ugariak dira hegaztien hondakinak. Azterketa tafonomikoak eta zooarkeologikoak harrapariek, karniboroek eta neandertalek hegaztiekin lotuta egindako ustiapenari buruzko gai esanguratsuak azaleratu ditu. Gainera, mendebaldeko Europan harrapakin txikien ustiapena egin deneko beste aztarnategi bat azaldu da.

The aliphatic hydrocarbon distributions of terrestrial plants around an alpine lake: a pilot study from Lake Ximencuo, Eastern Qinghai-Tibet Plateau

As part of an investigation of the sources of aliphatic hydrocarbons to the sediments of alpine Lake Ximencuo, leaves of the eight dominant vascular plants were collected and their hydrocarbon contents were analyzed. A series of unsaturated aliphatic hydrocarbons were identified in the plant leaves; in particular, Festuca sp. contain a series of n-alkadienes that have rarely been reported in previous studies. The comparison of n-alkane proxies (ACL27–33, ACLT, Paq, and CPI) and δ13Corg among plant leaves, surface soils, and lake sediments suggests that organic proxies have been altered to varying degrees during the transport and burial process of organic materials. It is believed that microbial reworking and source changes have great impacts on organic proxies in the alpine lake system. In addition, the cluster analysis for plant leaves depending on n-alkane compositions and the ACLT proxy generates similar results. Accordingly, we postulate that the average chain length of plant waxes might be a potential indicator of plant classification in regions such as the Qinghai-Tibet Plateau.

Sedimentary composition and organic carbon sources in mangrove forests along the coast of northeast Vietnam

The objective of this research was to examine the patterns of sedimentation and sedimentary organic carbon content in mangrove forests along the coast of northeast Vietnam. Stable isotope ratios (δ13C), C/N ratios, and sediment texture (sediment grain size, sorting, skewness and sediment facies) were analyzed in three sediment cores from different mangrove forests. Results showed that sediments were mainly composed of fine sand, silt, and clay. Mud content decreased from estuarine islets through to the fringe, and to riverine mangrove forests. Total organic carbon (TOC) content, δ13C values, and C/N ratios ranged from 0.3 to 6.8%, –30.1 to −24.9‰, and 12 to 42, respectively. Results from bivariate analysis of sedimentary parameters clearly indicated that hydrological energy in the riverine mangrove forest was relatively lower than that observed from the fringe and estuarine islet mangrove forests. Co-variation between δ13C and C/N ratios showed that sedimentary organic carbon in riverine mangrove forests mainly originated from mangrove organic matter, while fringe and estuarine islet mangrove forests tended to accumulate higher proportions of marine phytoplankton. Results underscored the significance of mangrove stands and geomorphological settings in influencing sedimentation and organic carbon burial processes in mangrove sediments.

Anthropological Study of Burial Ceremony in African Development and Harnessing Traditional Knowledge Among the Abagusii

The Abagusii like other tribes in Africa, burial ceremony, was the last respect given to the dead body. Burial (Ogotindeka) was anthropologically done according to Abagusii customs and traditions. When a married man or husband to more than two wives (Omogaka bwo’omochie) died was buried in the first wife’s house in the homestead if he was a polygamist. The dead body was laid in the reception room at the left side of the room for the whole night. The dead body was removed from the house using the left door (Omorangwa o’gesaku,or bweri) when the grave was ready in the morning as the animals were off the manger for grazing. The problem nowadays, burial rituals and customs are not followed such as grave digger speaking or eating food inside the grave or drinking water while in the grave. This has been ascertaining to be an abomination and leading too many people losing lives and is seen as a sign of curses in the family. The objective of the study is to investigate the factors leading to erosion of burial rites and rituals among the Abagusii. Also to unearth the anthropological burial ceremony process for harsening traditional knowledge and sustainable African development in Kenya and Africa at large. The research adopts analytical method through the empirical primary data collected from the Abagusii elders. The results indicate that the modern Abagusii people do not value burial ritual and customs. The sons and daughters leave the homestead immediately after burial to go and attend the chorus of work in towns. There is no second day crying /respect (Eburu) for deceased. It is concluded that the un honored burial ceremonies lead to curses and as consequence more deaths.It is recommended for harssening the African traditional knowledge, the Abagusii should follow the burial rituals and customs to suppress more deaths to occur in families.

Re–Os Dating of Bitumen from Paleo–Oil Reservoir in the Qinglong Antimony Deposit, Guizhou Province, China and Its Geological Significance

AbstractAbundant organic inclusions are present in the Qinglong antimony deposit. However, the source rocks of these organic matters have not been reliably identified. Recently, a paleo‐oil reservoir was found in the Qinglong antimony deposit. In view of similar components of gaseous hydrocarbon, we propose that the organic matters observed in inclusions in Qinglong antimony deposit would come from this paleo‐oil reservoir. We used the Re‐Os dating method to determine the age of the bitumen from this paleo‐oil reservoir, and obtained an isochron age of 254.3±2.8 Ma. The age indicates that the oil‐generation from source rock occurred in the early Late Permian, earlier than the Sb mineralization age (∼148±8.5 Ma) in the Qinglong antimony deposit area. After oil generation from Devonian source rock, first and secondary migration, the crude oil have probably entered into the fractures and pores of volcanic rocks and limestone and formed a paleo‐oil reservoir in the western wing of Dachang anticline. As burial process deepened, the crude oil has turned into natural gas, migrates into the core of Dachang anticline and formed a paleo‐gas reservoir. The hydrocarbons (including CH4) in the reservoirs can serve as reducing agent to provide the sulfur required for Sb mineralization through thermal chemical reduction of sulfates. Therefore, the formation of oil‐gas in the area is a prerequisite for the Sb mineralization in the Qinglong antimony deposit.

GC–MS and HPLC-ESI-QToF characterization of organic lipid residues from ceramic vessels used by Basque whalers from 16th to 17th centuries

This work is focused on the chemical characterization of the organic residues preserved in ceramic fragments that are suspected to have been used by the Basque whalers in the period from 16th to 17th Century to store whale oil. The lipid profiling along with the identification of biomolecular markers, makes possible to obtain information on the contents of the vessels and on the transformations undergone by the organic substances during the burial process. To achieve this goal, two complementary analytical techniques, High-Performance Liquid Chromatography - Electrospray Ionization - Quadrupole Time-of-Flight Mass Spectrometry (HPLC-ESI-QToF) and Gas Chromatography-Mass Spectrometry (GC–MS), were used not only to study the archaeological materials but also fresh whale oil products used as reference materials with the aim to detect potential diagnostic biomarkers. HPLC-ESI-QToF was used to identify triacylglycerols (TAGs) and study their distribution in the various samples, whereas GC–MS after suitable derivatization provided the fatty acid (FA) profile together with the detection of degradation compounds (dicarboxylic and dihydroxy fatty acids) and biomarkers related to marine commodities (isoprenoid acids). Samples of blubber from 5 different whale species belonging to the genus Balaenoptera (fin, sei and minke whale), Megaptera (Humpback whale) and Phocoena (harbour porpoise) were used as reference materials together with a sample of whale oil of unknown origin. The chemical results confirm the archaeological data regarding the vessels use as containers to store whale oil and indicate the whales from Balaenoptera genus as the most probable source of the oil.

Distribution of heavy metals in seafloor sediments on the East China Sea inner shelf: Seasonal variations and typhoon impact

Based on concentrations and distributions of heavy metals, grain size and loss on ignition (LOI) in the seafloor sediments acquired during three surveys in winter and in summer (before and after typhoon Morakot) in the mud deposition center off the Fujian-Zhejiang coast, East China Sea, the seasonal and typhoon-induced variations of heavy metals in seafloor sediments are discussed. It is found that different concentrations of heavy metals occurred in seafloor sediments, but their distribution patterns were similar, gradually decreasing from near-shore to offshore. The distribution of heavy metals was correlated with grain size and LOI in seafloor sediments, which showed significant seasonal variations and typhoon's impact. Based on these results, a conceptual evolution model was built about the seasonal and typhoon's impact on the deposition environment of heavy metals, which has implications for understanding the migration, settling, and burial processes of heavy metals in the sea.

Early diagenesis driven by widespread meteoric infiltration of a Central European carbonate ramp: A reinterpretation of the Upper Muschelkalk

Meteoric diagenesis of carbonate ramps is often difficult to interpret and can commonly be confused with other coinciding diagenetic processes. The Middle Triassic Upper Muschelkalk of Switzerland provides an insightful case in which the effects of several overprinting diagenetic environments, including matrix dolomitization, can be clearly unravelled. Previous studies suggested that diagenesis took place in connate marine waters, with later meteoric waters being invoked to explain recrystallization of dolomite. In this study, diagenetic analyses (C–O stable isotope ratios, thin-section point counting, cathodoluminescence and UV-fluorescence microscopy) of calcitic bioclastic samples have revealed that early diagenesis (pre-stylolitization) and the accompanying porosity evolution did not occur exclusively in the presence of marine fluids. Five sequential stages of diagenesis have been identified: marine, shallow burial, mixing-zone, meteoric and dolomitization. Marine diagenesis induced precipitation of bladed and inclusion-rich syntaxial cements that fluoresce strongly under UV-light. Both cements account for a mean 7.5vol% reduction in the porosity of bioclastic beds. Shallow burial diagenesis likely induced mouldic porosity and associated fluorescent dog-tooth cementation. Based on light oxygen isotope and elevated strontium isotope ratios, matrix aragonite–calcite neomorphism is interpreted to have occurred in a mixture of marine and meteoric fluids. The combination of shallow burial and mixing-zone processes reduced porosity on average by 4.8vol%. Evidence for subsequent meteoric diagenesis is found in abundant dog-tooth and blocky calcite cements that have mean δ18OVPDB of −9.36‰ and no signs of recrystallization. These meteoric cements reduced porosity by a further 13.4vol%. Percolation of meteoric water through the ramp was driven by hydraulic gradients on an adjacent basement high, which was exposed by a cycle of early Ladinian regressions. Following meteoric diagenesis the Upper Muschelkalk was dolomitized by refluxing brines. This complex history of diagenesis resulted in moderate porosities in dolomitized rocks (up to 20%), and low porosities (<5%) in calcitic bioclastic beds. These results are used to show that the present-day reservoir properties of non-dolomitized carbonate rocks, particularly bioclastic beds, can be largely attributed to early diagenetic processes. Thus, knowledge of the early diagenetic history and its regional controls provides a means to predict reservoir properties over wide areas between and beyond well sites.

Crustal strength control on structures and metamorphism in collisional orogens

Although the upper crust is the most accessible among other crustal units, so far little attention was paid about its role on the continental collision style and on exhumation processes of metamorphic rocks. With this respect, several 2D thermo-mechanical numerical experiments of post-subduction continental collision were performed, which allowed investigating the interplay between surface processes, thermal history and rheology of the upper crust units. The viscous strength of upper and lower plate upper crust (U.U.C. and L.U.C.) was systematically changed, obtaining a reference set of experiments to which subsequently we applied enhanced erosion patterns and variable radiogenic heat productivity of the sediments.We obtained three classes of collisional style: 1) decoupled asymmetric; 2) coupled asymmetric; 3) coupled symmetric. In general, for high-rates of radiogenic heating, a strong U.U.C. leads to one-sided, asymmetric and coupled hot orogen, which shifts to two-sided symmetric for weaker U.U.C. Lower radiogenic heat productivities yield colder orogens, promoting more asymmetric orogens and eventually the decoupling between upper and lower plates. The enhanced erosion leads to narrower and colder orogens, affecting the collisional style only for a relatively strong L.U.C. rheology.Exhumation of high-grade metamorphic rocks mainly depends on the L.U.C. strength: a weak viscous rheology promotes pure shear thickening of the incoming crust in the orogenic front, which inhibits both burial and exhumation processes. Higher viscous strengths promote deeper subduction of the L.U.C., with subsequent heating, delamination, partial melting and exhumation of high-grade rocks via channel flow. Enhanced erosion, although not a necessary condition, favours the extrusion of the partially melted mid-crustal channel.Overall, the numerical experiments reproduce the first order structural and/or metamorphic patterns of several natural cases (Himalayas, Boehmian Massif, Eastern-Central Alps, Apennines) and further suggest that the upper crust rheology is one of the key parameters controlling the collisional style and exhumation processes.

A heavy metal module coupled with the SWAT model and its preliminary application in a mine-impacted watershed in China

Heavy metal behavior in soil and water requires modeling for a better understanding of the potential adverse impacts on the ecosystem as well as on humans. A heavy metal transport and transformation module is combined with the well-established SWAT (Soil and Water Assessment Tool) model for the purpose of simulating the fate and transport of metals at the watershed scale. The heavy metal module accounts for sorption, complexation and slow reactions among metal species; the heavy metals in the upland are allowed to transport vertically through percolation and evaporation-induced water rising as well as horizontally through soil erosion and surface/subsurface runoff; the heavy metals in the water body, in contrast, are modeled to undergo settling, resuspension, diffusion and burial processes. As a demonstration, the SWAT-laden heavy metal module (SWAT-HM) was calibrated to simulate zinc (Zn) and cadmium (Cd) dynamics in an upstream watershed of the Liuyang River in China, which has been impacted by mining activities for decades. The model simulations were found to agree reasonably well with the monitored results. In particular, the elevation of metal loads in channels with precipitation events was well represented, demonstrating that a considerable amount of Zn and Cd in the waste rock dumps and contaminated soil was released into rivers through rainfall. After a simulation of 6years (2009–2014), the simulated Zn and Cd concentrations were used as a surrogate for the Predicted Environmental Concentration (PEC), whereby an ecological risk assessment was conducted for the demonstrative mining area. This initiative toward developing a heavy metal module combined with SWAT has high potential for application in environmental risk analysis and pollution control.

Prolonged anatexis of Paleoproterozoic metasedimentary basement: First evidence from the Yinchuan Basin and new constraints on the evolution of the Khondalite Belt, North China Craton

Discerning the history of burial, residence at depth and exhumation of high grade metamorphic rocks from an orogen is essential to understanding crustal differentiation and orogenesis. Such high grade rocks are inferred to exist beneath the Yinchuan Basin, which is overlain by a thick covering of younger sediments, and is located at the inferred southwest boundary of the Paleoproterozoic Khondalite Belt in the northwestern North China Craton. The metamorphic basement sampled from a recently completed deep borehole in the Yinchuan Basin is migmatitic and contains an assemblage of garnet, biotite, sillimanite, plagioclase, quartz, minor K-feldspar and local occurrences of muscovite. Phase equilibrium modelling in the Na2O–CaO–K2O–FeO–MgO–Al2O3–SiO2–H2O–TiO2–O system constrains the peak P–T conditions of anatexis to 6–10kbar at 760–810°C, followed by final crystallization at 4.5–5.5kbar and 690–710°C. Ti-in-zircon thermometry for the narrow metamorphic zircon rims provides a temperature range of 687–753°C, demonstrating formation during retrogression to the solidus. NanoSIMS U–Pb analyses on the metamorphic overgrowths of zircon grains yields an upper intercept age of 1895±36Ma. Chronological and chemical analyses of monazite indicate irregular bright gray domains with relatively high Th and low Y and HREE contents developed during prograde metamorphism (1962±8Ma). Conversely, dark domains with low Th and high Y and HREE overgrew during retrograde cooling (1892±14Ma) that was synchronous with the development of metamorphic zircon rims. LA-ICP-MS U–Pb analyses of detrital zircons reveal that the metamorphic basement beneath the Yinchuan Basin has a sedimentary protolith of Paleoproterozoic age. The results directly confirm the existence of Paleoproterozoic basement beneath the Yinchuan Basin, and the well-constrained P–T–t path supports the involvement of the basement (as part of the western Khondalite Belt) in burial and exhumation processes during the 1.96–1.89Ga period, during which anatexis occurred for ∼70Ma.

Deep carbon storage potential of buried floodplain soils

Soils account for the largest terrestrial pool of carbon and have the potential for even greater quantities of carbon sequestration. Typical soil carbon (C) stocks used in global carbon models only account for the upper 1 meter of soil. Previously unaccounted for deep carbon pools (>1 m) were generally considered to provide a negligible input to total C contents and represent less dynamic C pools. Here we assess deep soil C pools associated with an alluvial floodplain ecosystem transitioning from agricultural production to restoration of native vegetation. We analyzed the soil organic carbon (SOC) concentrations of 87 surface soil samples (0–15 cm) and 23 subsurface boreholes (0–3 m). We evaluated the quantitative importance of the burial process in the sequestration of subsurface C and found our subsurface soils (0–3 m) contained considerably more C than typical C stocks of 0–1 m. This deep unaccounted soil C could have considerable implications for global C accounting. We compared differences in surface soil C related to vegetation and land use history and determined that flooding restoration could promote greater C accumulation in surface soils. We conclude deep floodplain soils may store substantial quantities of C and floodplain restoration should promote active C sequestration.

Geomorphology and sedimentary sequence evolution during the buried stage of paleo-uplift in the Lower Cretaceous Qingshuihe Formation, Junggar Basin, northwestern China: Implications for reservoir lithofacies and hydrocarbon distribution

The evolution of large-scale paleo-uplifts within sedimentary basins controls the sedimentary provenance, depositional systems and hydrocarbon distributions. This study aims to unravel changes in paleo-geomorphology, interpret sedimentary sequence evolution, and investigate favourable reservoir types and the hydrocarbon distribution during the buried stage of a long-term eroded paleo-uplift, taking the Lower Cretaceous Qingshuihe Formation (K1q) in the Junggar Basin as an example. These research topics have rarely been studied or are poorly understood. This study integrates current drilling production data with outcrop and core analyses, drilling well logs, 3D seismic data interpretations, grading data, physical property comparisons and identified hydrocarbon distributions.After more than 20 million years of differential river erosion and weathering in arid conditions, the large-scale Chemo paleo-uplift within the hinterland area of the basin formed a distinctive valley–monadnock paleo-geomorphology prior to the deposition of K1q. Since the Early Cretaceous, tectonic subsidence and humid conditions have caused the base level (lake level) to rise, leading to backfilling of valleys and burial processes. Two systems tracts in the target strata of K1q, consisting of distinctive depositional systems, can be identified: (1) a lowstand systems tract (LST), which is confined within incised valleys and is mainly composed of gravelly braided rivers and rarely occurring debris flows and (2) an extensive transgressive systems tract (TST), which developed into an almost flat landform and consists of braided river delta to lacustrine depositional systems. Overall, the physical properties of braided river reservoirs in the LST are better than those of the braided river delta reservoirs in the TST. However, the inhomogeneous distributions of carbonate cements cause differences in the physical properties of conglomerate reservoirs in the LST. However, for sandstones in both the LST and TST, coarser grain sizes and better sorting result in better physical properties. Altogether, four types of reservoir can be identified in the study area: Jurassic inner monadnock reservoirs, K1q LST stratigraphic onlap reservoirs, LST structural reservoirs and TST structural reservoirs.