Primary Source Areas Research Articles

Provenance of Lower Jurassic sediments in the South China continental margin: Evidence from U-Pb ages of detrital zircons

In the Early Jurassic, a large-scale transgression occurred on the South China continental margin (SCCM), affected by the initiation of Paleo-Pacific subduction. This transgression significantly influenced the source areas and transport mode of Lower Jurassic sediments in the SCCM. This study discussed the differences in the major source areas among the western, central, and eastern SCCM and constructed a brief Lower Jurassic sediments transport process in the SCCM. To avoid the bias of detrital-zircon ages caused by variations in zircon fertility, we gathered 1802 whole-rock zirconium content values (ppm) from representative granites with different ages in the South China Craton. Based on mean Zr contents and statistical analyses, we divided these granitic rocks into three groups: Group A consists of Jurassic (200–145 Ma) and Neoproterozoic (900–700 Ma), Group B consists of Paleozoic (490–390 Ma) and Permian–Triassic (280–210 Ma), and Group C comprised Paleoproterozoic (2000–1700 Ma) and Neoarchean (2900–2500 Ma). This research assigned these groups zircon fertility factors (ZFF) of 1.0, 1.4, and 2.5, respectively. Subsequently, by studying corrected detrital zircon ages from Lower Jurassic sediments by ZFF, we found that the Yunkai Terrane and Hainan Island were primary source areas for the western SCCM. The Wuyi Terrane and Nanling Tectonic Belt provided abundant detrital materials for the eastern SCCM. It should be noted that the central SCCM was a vast shallow sea in the Early Jurassic due to the large-scale transgression. Thus, the coastal currents and drowned pre-Jurassic river valleys controlled sediment delivery to the central SCCM. Overall, the Lower Jurassic sediments distribution system in the SCCM was significantly affected by Paleo-Pacific subduction.

Modes of occurrence and multiple sources of minerals in the Late Permian coals from the Shugentian Mine, eastern Yunnan, China: implication for the microenvironmental evolution of coal formation

The Kangdian Upland, mainly covered by the Emeishan basalt and a small amount of intermediate-felsic rocks (e.g., trachyte and rhyolite), is the primary sediment source area of the coal-bearing basin in southwestern China. Different from the formation of authigenic quartz in other Late Permian coals reported by previous studies, the authigenic quartz identified in the No. 7 coal of Shugentian mine was derived not only from the siliceous solution weathered from the Emeishan basalt in the Kangdian Upland, but also from the silicon-rich hydrothermal fluids that migrated along the fault zones due to multi-phase tectonic movement. Chamosite in this study was mainly considered as the interaction product between kaolinite and Fe-Mg-rich hydrothermal fluids, according to the modes of occurrence of chamosite and its close relationship with kaolinite and quartz. Anatase occurred as either coarse-crystalline or reticular forms filled with authigenic quartz, implying the intrusion of multi-stage hydrothermal fluids. The parting sample, characterized by sharp-edged quartz and angular zircon crystals with eroded holes and cracks, was identified as a layer of pyroclastic tonstein, the high Al2O3/TiO2 ratio of which supported that the parent volcanic ash was felsic in composition. The influence of seawater made not only a contribution to the higher content of total sulfur and pyrite, but also a comfortably alkaline environment for the formation of cell-filling calcite and ankerite. The differences of content and modes of occurrence of calcite and ankerite between the 7L and 7U coal seam in the Shugentian mine indicated that the coal-forming microenvironment has evolved from alkaline to acidic dominant.

Jurassic evolution of the Qaidam Basin in western China: Constrained by stratigraphic succession, detrital zircon U-Pb geochronology and Hf isotope analysis

The formation and evolution of an intracontinental basin triggered via the subduction or collision of plates at continental margins can record intracontinental tectonic processes. As a typical intracontinental basin during the Jurassic, the Qaidam Basin in western China records how this extensional basin formed and evolved in response to distant subduction or collisional processes and tectonism caused by stresses transmitted from distant convergent plate margins. The Jurassic evolution of the Qaidam Basin, in terms of basin-filling architecture, sediment dispersal pattern and basin properties, remains speculative; hence, these uncertainties need to be revisited. An integrated study of the stratigraphic succession, conglomerates, U-Pb geochronology, and Hf isotopes of detrital zircons was adopted to elucidate the Jurassic evolutionary process of the Qaidam Basin. The results show that a discrete Jurassic terrestrial succession characterized by alluvial fan, braided stream, braided river delta, and lacustrine deposits developed on the western and northern margins of the Qaidam Basin. The stratigraphic succession, U-Pb age dating, and Hf isotope analysis, along with the reconstructed provenance results, suggest small-scale distribution of Lower Jurassic sediments deposited via autochthonous sedimentation on the western margin of the basin, with material mainly originating from the Altyn Tagh Range. Lower Jurassic sediments in the western segment of the northern basin were shed from the Qilian Range (especially the South Qilian) and Eastern Kunlun Range. And coeval sediments in the eastern segment of the northern basin were originated from the Quanji massif. During the Middle-Late Jurassic, the primary source areas were the Qilian Range and Eastern Kunlun Range, which fed material to the whole basin. The Jurassic sedimentary environment in the Qaidam Basin evolved from a series of small-scale, scattered, and rift-related depressions distributed on the western and northern margins during the Early Jurassic to a larger, extensive, and unified depression occupying the whole basin in the Middle Jurassic. The Altyn Tagh Range rose to a certain extent during the Early Jurassic but lacked large-scale strike-slip tectonism throughout the Jurassic. At that time, the North Qaidam tectonic belt had not yet been uplifted and did not shed material into the basin during the Jurassic. The Qaidam Basin experienced intracontinental extensional tectonism with a northeast-southwest trend throughout the Jurassic in response to far-field effects driven by the sequential northward or northeastward amalgamation of blocks to the southern margin of the Qaidam Block and successive accretion of the Qiangtang Block and Lhasa Block onto the southern Eurasian margin during the Late Triassic−Early Jurassic and Late Jurassic−Early Cretaceous, respectively.

Sedimentary records of the late Early Cretaceous compressional setting in the South China block: A case study of the Xingning Basin, Guangdong Province

AbstractRecently, some scholars have proposed that the South China Block (SCB) was controlled by a compressive tectonic regime in the middle–late Early Cretaceous, challenging the belief that the SCB was under an extensional setting during the Cretaceous. The Early Cretaceous tectonic setting constraint in the SCB can offer vital insight to clarify the Mesozoic subduction history of the Paleo‐Pacific. Therefore, to determine the SCB tectonic regime during the Early Cretaceous, this study investigated sedimentary rocks from the Lower Cretaceous Heshui Formation in the Xingning Basin, a foreland basin located in the southeastern SCB. Provenance analysis was performed using sandstone modal analysis, sandstone geochemical characteristics, and detrital zircon geochronology. Based on the results, we discussed basin sediment sources and the SCB tectonic regime during the Early Cretaceous. The results showed that the maximum Heshui Formation depositional age was 103 Ma ± 1.6 Ma in the Early Cretaceous Albian. Detrital framework modes and geochemical characteristics of sandstone indicated that Heshui Formation's source rocks were granites and sedimentary rocks. The detrital zircon U–Pb ages could be classified into two major and four subordinate age populations. The Wuyi Terrane to the north and southeast coastal regions to the east were the primary potential Heshui Formation source areas. However, the lower and upper sandstones are different in the peak ages, ~437 and ~146 to 104 Ma, respectively, indicating that the major source area shifted from the Wuyi Terrane to the southeastern coastal regions during the late Early Cretaceous. The sandstone modal analysis results indicated that the source area comprised mainly collisional–orogenic material. The SCB was under a compressive tectonic regime during the late Early Cretaceous and this compression action continued until at least 103 Ma ± 1.6 Ma.

Construction and demolition wastes in Beijing: Where they come from and where they go?

Urbanization and related construction activities generate massive construction and demolition (C&D) waste, which poses considerable risks to the environment and human health. However, it is difficult to assess the significance of these issues without a quantitative understanding of spatial patterns of C&D waste generation (source), transportation (flow), and treatment (sink). This paper maps source, sinks, and flows of C&D waste by coupling a geographic information system and material flow analysis. The methodology is new in the field of C&D waste quantification at the city level, especially downscaling to 5 km × 5 km grids. The results showed that a total of 37.72 million metric tonnes (Mt) of C&D wastes were generated in Beijing, 2019, and ~72% of them were reused and recycled. In space, C&D waste generation in suburban and rural districts (28.73 Mt) was over three times more than that in the downtown area (8.99 Mt). However, the downtown area was the net source region and transported massive amounts of C&D waste to suburban and rural districts. In comparison, several suburban and rural districts had self-sufficient treatment capacity. Our study highlights that a series of C&D waste maps on multiple spatial scales are of great help to design effective policies for waste management by providing spatial details of magnitude and components, and explicitly recognizing primary source and sink areas in cities.

Variability in chert raw material procurement and use during the Upper Paleolithic and Early Neolithic of the southern Levant: A regional perspective from the Greater Petra area

In SW Asia, chert procurement studies have received increasing attention in the last two decades. However, studies on chert availability and procurement are often focused on single sites or inventories and characterize different groups of cherts for each site, complicating cross-site comparisons. Our paper aims to show the potential of lithic studies if similar standards in raw material description and analysis of availability are applied in a cross-project and diachronic study. We analyzed more than 25,000 lithic artefacts from nine Upper Paleolithic to Early Neolithic sites in the southern Levantine Greater Petra Region. Parameters of study include the identification of flint raw material groups (FRMG), the analysis of cortex or remains of natural surfaces, the geological availability of FRMGs within the Greater Petra Region, and a minimal distance analysis (MDA) of chert raw materials for the sites based on least-cost-models.Two chert raw material surveys, conducted in 2012 and 2015, show that primary source areas of most FRMG in the Greater Petra Region are restricted to two geological formations and are a suitable tool for predictive source modelling.The spectrum of used FRMG among the sites and periods is very variable, with the tendency of a wider spectrum in early Neolithic, and a more restricted one in Upper Paleolithic sites. Upper Paleolithic inventories show either a very targeted and direct procurement of lithic material, or an embedded one - resulting in greater raw material diversity. Pre-Pottery Neolithic B (PPNB) lithic economies are characterized by increasing complexity and craft specialization. Specialized (surplus) production of standardized bidirectional blades co-exist with a generalized household production (non-standardized and assumed to be primarily self-sufficient). While the generalized household production shows very opportunistic modes of chert procurement (often gathered from nearby wadi fills), the raw material procurement for specialized production is characterized by a clear preference for high-quality cherts from primary sources. Generally, only one or two chert types are processed per workshop.We suggest that different socio-economic settings contribute to the variabilities observed and use a multivariate statistical method (Canonical Correspondence Analysis) to test selected binary covariables (chronological and cultural affiliation and PPNB blade technology) for significance. All tested covariables show significant differences in raw material procurement behavior. A general trend is observable towards increasing complexity in procurement processes mirroring the more complex ways of life in the Early Neolithic Period. In general, lithic economy in the Greater Petra Region shows a diachronic consistency of high investment if high quality cherts are needed, and a low investment if no special demands are placed on the material.

Using SWAT to Evaluate Streamflow and Lake Sediment Loading in the Xinjiang River Basin with Limited Data

Soil erosion and lake sediment loading are primary concerns of watershed managers around the world. In the Xinjiang River Basin of China, severe soil erosion occurs primarily during monsoon periods, resulting in sediment flow into Poyang Lake and subsequently causing lake water quality deterioration. Here, we identified high-risk soil erosion areas and conditions that drive sediment yield in a watershed system with limited available data to guide localized soil erosion control measures intended to support reduced sediment load into Poyang Lake. We used the Soil and Water Assessment Tool (SWAT) model to simulate monthly and annual sediment yield based on a calibrated SWAT streamflow model, identified where sediment originated, and determined what geographic factors drove the loading within the watershed. We applied monthly and daily streamflow discharge (1985–2009) and monthly suspended sediment load data (1985–2001) to Meigang station to conduct parameter sensitivity analysis, calibration, validation, and uncertainty analysis of the model. The coefficient of determination (R2), Nash–Sutcliffe efficiency (NSE), percent bias (PBIAS), and RMSE -observation’s standard deviation ratio (RSR) values of the monthly sediment load were 0.63, 0.62, 3.8%, and 0.61 during calibration, respectively. Spatially, the annual sediment yield rate ranged from 3 ton ha−1year−1 on riparian lowlands of the Xinjiang main channel to 33 ton ha−1year−1 on mountain highlands, with a basin-wide mean of 19 ton ha−1year−1. The study showed that 99.9% of the total land area suffered soil loss (greater than 5 ton ha−1year−1). More sediment originated from the southern mountain highlands than from the northern mountain highlands of the Xinjiang river channel. These results suggest that specific land use types and geographic conditions can be identified as hotspots of sediment source with relatively scarce data; in this case, orchards, barren lands, and mountain highlands with slopes greater than 25° were the primary sediment source areas. This study developed a reliable, physically-based streamflow model and illustrates critical source areas and conditions that influence sediment yield.

Intensifying swells and their impacts on the south coast of Java, Indonesia

ABSTRACTA post-event survey of an extreme swell was conducted along the south coast of Java, Indonesia, where swells in the high wave season are likely to intensify in the long term. The measured runup heights varied from 4 to 6 m along the long straight coastline, which were comparable to those observed during the 2006 Pangandaran earthquake tsunami. The damage to the coastal communities was, however, found to be of a minor to moderate level as coastal inundation was confined to a narrow strip on the shore due to the steep subaerial topography of the coastal areas. The characteristics of the extreme swell event were analyzed using the long-term wave reanalysis dataset created by the European Centre for Medium-Range Weather Forecasts (ECMWF). The results suggested that the extreme event was the highest one over the past 40 years, whose return period is approximately 100 years even though the long-term increasing trend was taken into account. Through a cross-correlation analysis of the wave data, the primary swell source area was identified in the extra-tropical region of the southern Indian Ocean, where strong westerlies developed energetic swells.

The metamorphic rocks of the Nunatak Viedma in the Southern Patagonian Andes: Provenance sources and implications for the early Mesozoic Patagonia-Antarctic Peninsula connection

The Nunatak Viedma within the Southern Patagonian Icefield has been considered as a volcanic center based on its geomorphologic features, despite the fact that field explorations by Eric Shipton determined its metamorphic nature 70 years ago. We carried out fieldwork to characterize this isolated outcrop and performed the first U-Pb dating in detrital zircons from the basement rocks located inside the Southern Patagonian Icefield. We recognized very-low grade metamorphic rocks, corresponding principally to metapelites and metapsammites, and scarce metabasites. Detrital zircons in three metapsammitic samples (composite group of 240 grains) yielded prominent age population peaks at ∼1090, ∼960, ∼630, ∼520, ∼480–460, ∼380, ∼290–260, ∼235-225 Ma that are typical of Gondwanide affinity, and youngest grains at ∼208 Ma. Maximum depositional ages of 225, 223 and 212 Ma were calculated for each sample from the youngest cluster of ages. This distinctive and novelty Late Triassic age justifies differentiate the Nunatak Viedma Unit from the Devonian-early Carboniferous and Permian-Early Triassic (?) belts of the Eastern Andean Metamorphic Complex. Possible primary source areas for the detrital zircons are outcropping in southern Patagonia, the Antarctic Peninsula, and the Malvinas Islands. Additionally, secondary sources could be part of the erosion and recycling of metasediments from the Eastern Andean Metamorphic Complex. We propose that the cluster of Triassic ages is related to the volcanic arc emplaced along the Antarctic Peninsula and active at that time when was still attached to southern Patagonia during the Triassic. The dynamics of the early Mesozoic orogen is also discussed.

Detrital zircon U–Pb geochronology of early Cretaceous sedimentary rocks in Dingzi Bay and Taolin area from the Sulu Orogen: Provenances and tectonic implications

Early Cretaceous sedimentary rocks in the Sulu Orogen (SO) have been a popular topic in recent years. The provenances of sedimentary rocks can help elucidate the tectonic history of the SO, China. The Dingzi Bay and Taolin areas in the SO have always been poorly known. Thus, we date detrital zircons from four sedimentary rock samples including sandstone, siltstone, and greywacke collected in both areas. Age distributions from Dingzi Bay exhibit three major age populations including Palaeoproterozoic (1900–1800 Ma), Neoproterozoic (800–700 Ma), and Early Cretaceous (136–106 Ma) ages and small age populations including early Mesozoic, Palaeozoic, and Palaeoproterozoic–Archean ages, while age distributions in the Taolin area show the largest age population of Early Cretaceous (132–102 Ma) with minor early Mesozoic, Palaeozoic, and Neoproterozoic populations. The youngest detrital zircon populations yield weighted mean ages of ca. 116 Ma in Dingzi Bay and ca. 120 Ma in the Taolin area as the maximum depositional ages, which correspond to the Early Cretaceous Lower Qingshan Group. Age distributions in both areas indicate that the local SO served as the primary source area, whereas the Yangtze Block might have been a lesser source of detrital zircons. The comparison of geochronological, geochemical, and sedimentary data among Dingzi Bay, Taolin, Laoshan, and Lingshan Island suggests an Early Cretaceous marine basin formed over the SO. Further, considering previous regional tectonic history, we propose a two‐stage (Laiyang and Qingshan stages) evolutionary model for this marine basin. We suggest that transpression between the Laiyang and Qingshan stages due to subduction of the Pacific Plate might have caused rapid uplift of the south‐eastern SO and closing of the marine basin. Correspondingly, this process influenced the input of the source material from the Yangtze Block to the marine basin during the Qingshan stage.

Origin of exotic clasts in the Central-Southern Apennines: clues to the Cenozoic fold-and-thrust collisional belt in the Central Mediterranean area

AbstractThe Central-Southern Apennines are the result of the collision between Europe and Africa. Despite the volume of existing literature, many problems remain unsolved such as the presence of Tertiary conglomerates containing exotic basement clasts. The lack of basement rocks in the Central-Southern Apennines implies that the origin of these clasts has to be sought in areas where the basement is extensively exposed. These include the Calabro–Peloritani arc and the Sardinia–Corsica block, which in Cenozoic time were connected to the Central-Southern Apennines. In this work we present the results of sedimentary, geochemical and petrographic analyses performed on the exotic basement-derived clasts. These analyses include lithological, major- and minor-element and rare Earth element compositions which are compared to analogous rocks from Calabria and Sardinia basements. Results indicate Eastern Sardinia as the primary source area for the studied conglomeratic units, linking the Central-Southern Apennines sedimentary cover to the Mesozoic carbonates of Eastern Sardinia prior to the opening of Tyrrhenian Sea. The Cilento unit (Campania) was directly fed by an uplifting Cenozoic orogen, and the Filettino, Gavignano (Latium) and Ariano Irpino (Campania) units were produced by the successive reworking of ‘Cilento-like’ sedimentary units. These results may imply that part of the Central-Southern Apennines represented a portion of the European margin of the Tethys.

Mobilization of Mercury and Arsenic from a Carbonate-hosted Ore Deposit, Central Idaho, U.S.A.

The Cinnabar and Fern mine sites in central Idaho are primary source areas for elevated mercury and arsenic entering the South Fork of the Salmon River, which provides critical spawning habitat for bull trout and Chinook salmon. Mercury mineralization is hosted by carbonate rocks, which generate waters dominated by Ca2+ and HCO3− at pH 7 to 9. A synoptic sampling was conducted on headwater tributaries to determine geologic background concentrations and quantify trace metal concentrations in stream water associated with historical mining. Geologic background concentrations in unfiltered Cinnabar Creek water were 8 - 14 ng Hg L-1 and 4.8 - 9.5μg As L-1. Immediately downstream from the mine site, concentrations increased to 257 ng Hg L-1 and 20.6μg As L-1. Groundwater inflow diluted these concentrations by approximately half before the confluence of Cinnabar Creek with Sugar Creek. As expected, mercury and arsenic concentrations increased downstream in Sugar Creek below the confluence with Cinnabar Creek. However, the final downstream reach on Sugar Creek showed an increase in unfiltered mercury, methylmercury, and iron concentrations relative to the upstream reach. This increase is associated with historical mining activity in a mineralized area of carbonate rock that intersects the reach.

Out‐of‐Tibet: the spatio‐temporal evolution of Gentiana (Gentianaceae)

AbstractAimWe investigated the historical biogeography and diversification of Gentiana L. (Gentianaceae). Our study depicts the origin and dispersal routes of this alpine genus, and the role of the uplift of the Qinghai–Tibet Plateau (QTP) and past climate changes as triggers for its diversification.LocationTibeto‐Himalayan region and world‐wide mountain habitats.MethodsOur sampling represents more than 50% of the extant Gentiana species, including all sections across their entire geographical ranges. We investigated the evolutionary history of Gentiana using phylogenetic reconstructions (maximum likelihood and Bayesian inference) of ITS, atpB–rbcL and trnL–trnF sequences, as well as molecular dating with beast. We tested two approaches of ancestral area reconstructions (DEC, DIVA) in BioGeoBEARS and investigated diversification rates using BAMM.ResultsThe common ancestor of Gentiana and subtribe Gentianinae lived in the QTP region at around 34 (25–45) million years ago (Ma), and 40 (29–52) Ma respectively. From the surroundings of the QTP, Gentiana lineages dispersed to eastern China, Taiwan, Europe, North and South America, Australia and New Guinea, from mid‐Miocene onward (c. 15 Ma–present), with only one older dispersal event to Europe (c. 37–21 Ma). Diversification rates gradually increased over time, and two switches of diversification rates were identified in Gentianinae (c. 7 Ma, simultaneously in the Pneumonanthe/Cruciata lineage and in Tripterospermum).Main conclusionsGentiana existed in the QTP region throughout most of its uplift history following the India‐Asia collision. This region acted as the primary source area for dispersals to many areas of the world. Because steady increase in diversification rates coincides with the extension of the QTP, we argue that the museum theory rather than the explosive radiation theory prevails for gentians in this region, although rare shifts of diversification rates are associated with niche shifts across the alpine/subalpine ecotone.

Predicting precipitation on nonpoint source pollutant exports in the source area of the Liao River, China.

The source area of the Liao River is an important grain growing area in China which experiences serious problems with agricultural nonpoint source pollution (NPS) which is impacting the regional economy and society. In order to address the water quality issues it is necessary to understand the spatial distribution of NPS in the Liao River source area. This issue has been investigated by coupling a wavelet artificial neural network (WA-ANN) precipitation model with a soil and water assessment tool (SWAT) model to assess the export of nonpoint source pollutants from the Liao River source area. The calibration and validation of these models are outlined. The WA-ANN models and the SWAT model were run to generate the spatial distribution of nonpoint source nutrient (nitrogen and phosphorus) exports in the source area of the Liao River. It was found that the SWAT model identified the sub-catchments which not only receive high rainfall but are also densely populated with high agricultural production from dry fields and paddy fields, which are large users of pesticides and chemical fertilizer, as the primary source areas for nutrient exports. It is also concluded that the coupled WA-ANN models and the SWAT model provide a tool which will inform the identification of NPS issues and will facilitate the identification of management practices to improve the water environments in the source area of the Liao River.

Geochemical Sourcing of Flint Artifacts from Western Belgium and the German Rhineland: Testing Hypotheses on Gravettian Period Mobility and Raw Material Economy

Identifying the geological and geographical origin of lithic raw materials is critical to effectively address prehistoric forager raw material economies and mobility strategies. Currently, Paleolithic archaeology in Belgium lacks a systematic sourcing strategy to effectively substantiate detailed interpretations of prehistoric hunter‐gatherer behavioral change across time and space. This pilot study evaluates the potential to “fingerprint” flint from the Mons Basin, western Belgium, using the laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) technique and a multivariate statistical analysis of 87 geological samples and 39 Gravettian period chipped stone artifacts. We reappraise two hypotheses raised by previous scholars based on visual raw material identification: (1) the Gravettian occupants of Maisières‐Canal supplied themselves with “black flint” from one single source; (2) the sites Rhens and Koblenz‐Metternich yielded artifacts indicative of long‐distance transfer of western Belgian flint into the German Rhineland, ca. 260 km from the primary source area. Our results demonstrate the validity of LA‐ICP‐MS data with flint and compositional data analysis for fingerprinting discrete geological formations from the Mons Basin. We suggest multiple source provisioning for Maisières‐Canal. Geochemical characterization of other potential flint sources is required to validate the long‐distance transfer hypothesis of western Belgian “black flint” into the German Rhineland.

Detrital zircon provenance of the Wangshi and Laiyang groups of the Jiaolai basin: evidence for Early Cretaceous uplift of the Sulu orogen, Eastern China

ABSTRACTThe Late Mesozoic Jiaolai basin preserves sediment source information that can help elucidate the tectonic history of East Shandong, China. The terrestrial Wangshi and Laiyang Groups are major components of the basin succession, but are not well studied in terms of their provenance and role in basin evolution. The Early Cretaceous Laiyang Group consists primarily of fluvial and lacustrine facies siltstones and sandstones, whereas the Late Cretaceous Wangshi Group consists of reddish fluvial siltstones and sandstones with interbedded conglomerates. This study reports detrital zircon age distributions from eight sandstones collected from the two groups. Age distributions exhibited four major populations of Palaeoproterozoic (2.5–2.4 Ga), Palaeoproterozoic (1.9–1.8 Ga), Neoproterozoic (850–700 Ma), and Jurassic to Early Cretaceous (171–107 Ma) ages. We interpret a maximum depositional age of 107 Ma for the Wangshi Group and a depositional age of 121–120 Ma for the upper Laiyang Group. Age distributions indicate that the Sulu orogenic belt of the East Shandong complex served as the primary source area. Detrital zircon age data also indicate major changes in the types of source material contributed to the Laiyang and Wangshi groups. Based on these shifts, we propose a four-stage model for Early Cretaceous evolution of the Jiaolai basin. In this model, subduction of the Pacific plate and associated transform motion on the Tan-Lu fault influenced the transition from a transpressional to an extensional tectonic setting.

Sediment grain-size characteristics and its source implication in the Ningxia–Inner Mongolia sections on the upper reaches of the Yellow River

The Ningxia–Inner Mongolia (NIM) reaches of the Yellow River are characterized by a high sediment load, severe siltation, large channel migration, and frequent dike breaching, resulting in substantial social, economic, and environmental problems for residents along the river. Therefore, studies on the grain-size characteristics of sediments in the NIM reaches of the Yellow River and locating the primary sediment source areas are important for the prevention and mitigation of silt accumulation and the construction of water conservation facilities. In this study, 361 samples from the Yellow River and 178 samples from potential source areas were analyzed. Large grain sizes in the riverbed and floodplain materials were found in the desert sections and in sections containing 10 tributaries, respectively. The size of the riverbed and floodplain materials fluctuates relatively frequently in the tributary sections and is coarser at confluences of the tributaries with the Yellow River. The floodplain material is better sorted than the riverbed material, and the sorting coefficients (especially the former) fluctuate most widely in the tributaries sections. Two main fractions of the floodplain and most of the riverbed materials in the major river reaches are observed: 3.9–63μm and 63–250μm. The first fraction component of the riverbed material, 63–250μm, is found in the desert sections and part of the tributary sections, whereas the second fraction component (250–500μm) is found in some parts of the desert sections. The variations in the size characteristics of the riverbed and floodplain materials demonstrate that both materials are derived from lateral sources. The main sources of the riverbed materials are the Ulan Buh Desert and the Kubuqi Desert in the Wuhai-Zhonghexi reaches, and the main sources of the riverbed and floodplain materials are the 10 tributaries in the Zhonghexi-Lama Bay reaches. The riverbed and floodplain materials in the desert sections are deposited near the source and far from the source, respectively. Both types of sediments in the tributary sections are mainly deposited near their sources. Through wind and hydraulic sorting, the size of the riverbed material in the tributaries sections becomes finer in contrast to that in the desert sections, which suggests that coarse sediments have not been effectively carried downstream.

Paleoarchean record of the detrital pyrite-bearing, Jacobina Au–U deposits, Bahia, Brazil

U–Pb and Lu–Hf isotope analyses were performed on detrital zircon grains from eight samples distributed along a 1000-m-thick section of the Au–U pyrite deposits of Jacobina to identify the primary source areas and define the maximum age for the basin sedimentation. These deposits contain detrital pyrite similar to that observed in the Witwatersrand gold province. Although the sequence was deformed by Paleoproterozoic orogeny, all of the detrital zircon grains (n=785) yielded Paleoarchean ages between 3.2 and 3.5Ga with primary peaks of approximately 3.3–3.4Ga. Most of the grains have nearly chondritic compositions with ɛHf(t) values between −5.6 and −0.1 and Hf model ages between 3.5 and 3.8Ga. The presence of detrital Au–U pyrite in the SiO2-rich metasedimentary rocks provide unequivocal evidence that the basin formed in an O2-poor atmosphere. The U–Pb data set and lithogeochemistry suggest that its infill material was derived from an exclusively Paleoarchean source, specifically sediments derived from the TTG-greenstone assembly of the Gavião Block (3.2–3.5Ga). These source rocks were strongly hydrothermally altered and weathered before deposition. The geochemical composition of the sedimentary rocks and the isotopic signature of Hf indicate that the sediments were derived from a juvenile source with minor crustal contamination and a short duration of crustal residence (between 150 and 350myr).

Post-Acadian sediment recycling in the Devonian Old Red Sandstone of Southern Ireland

The Upper Devonian Munster Basin of southern Ireland has traditionally been viewed as a post-orogenic molasse deposit that was sourced from the Caledonides of central Ireland and subsequently deformed by the end Carboniferous Variscan orogenic event. The basin fill is composed of super-mature quartz arenite sandstone that clearly represents a second cycle of deposition. The source of this detritus is now recognized as Lower Devonian Dingle Basin red bed sequences to the north. This genetic link is based on the degree of similarity in the detrital mica chemistry in both of these units; micas plot in identical fields and define the same trends. In addition, the two sequences show increased textural and chemical maturity up-sequence and define indistinguishable 40Ar/39Ar age ranges for the detrital mica grains. Partial resetting of the Ar ages can be attributed to elevated heat flow in the region caused by Munster Basin extension and subsequent Variscan deformation. The combined evidence from southwest Ireland therefore points to a Caledonian or possibly Taconian primary source area that initially shed detritus into the Lower Devonian Dingle Basin which was subsequently recycled into the Upper Devonian Munster Basin following mid-Devonian Acadian basin inversion.

Petrography and geochemistry of lower carboniferous greywacke and mudstones in Northeast Junggar, China: Implications for provenance, source weathering, and tectonic setting

Northeast Junggar occupies an important position that links East Junggar and Chinese Altai. Numerous magmatic and sedimentary rocks of the Paleozoic in this area recorded the final amalgamation processes of East Junggar and Chinese Altai. This study analyzes the petrological and geochemical characteristics of sandstones and mudstones from the Early Carboniferous Nanmingshui formation in Northeast Junggar. The provenance and tectonic setting of these clastic rocks are discussed. Petrography indicates that the composition and texture maturity of the sandstones are low. The components of the sandstones are mainly volcanic fragments (61–87%), feldspars (9–30%), and monocrystalline quartz (2–18%), with a few polycrystalline quartz and other minerals. Slice observation indicates that the majority of the volcanic fragments of sandstones are basic-intermediate volcanic rocks with a few dacite and felsic plutonic fragments. The detrital modes of the sandstones reflect that these sandstones are derived from undissected arcs. A low to moderate chemical index of alteration and the Al2O3–CaO*+Na2O–K2O diagram reflect a low to moderate weathering degree in the source area. Trace and rare earth element (e.g., La, Th, Hf, Sc, Cr, Co, and Eu) contents and their ratios suggest that the source rocks of the clastic rocks are intermediate-basic rocks with some felsic rocks. Compared with sandstones, the source rocks for mudstones are more felsic. The petrography and geochemistry characteristics of the clastic rocks suggest that the proximal Dulate arc should be the primary source area. Mixing calculations based on REE data suggest that approximately two-thirds of the sandstone fragments are intermediate-basic volcanic rocks. The contents of the major and trace elements, as well as the stratum features, of the clastic rocks manifest that these clastic rocks resemble sedimentary rocks in a back-arc basin. The formation of this back-arc basin is caused by the southward subduction of the Zaysan–Erqis Ocean.