Sediment Provenance Research Articles

Pollution sources and metallic elements mobility recorded by heavy minerals in soils affected by Cu-smelting (Legnica, SW Poland)

Abstract Heavy mineral particles are widely used in Earth science studies to show sediment provenance and weathering conditions. Such particles are particularly useful in polluted soils surrounding mining and smelting facilities because heavy minerals are common by-products of these activities and may accumulate in the soils. As such, the particles are suitable indicators of metallic element carriers and their stability in the soil environment. In this study, we analyze heavy mineral particles in two soils surrounding the active copper smelter (Legnica, SW, Poland). We show that particles associated with different smelting activities dominate the heavy mineral fraction. We note the general absence of sulfides in the fraction indicating that these minerals might have been entirely dissolved, but timing of this dissolution is uncertain (before or after deposition within soils). Currently, the carriers of potentially toxic elements are mainly secondary Fe oxides. Studies aiming at better estimation of the proportion of metallic elements contained in heavy mineral particles are needed to fully use the potential of these phases in polluted soil studies. We estimate that Pb contained in Pb-rich silicate glass constitutes <0.5% of the total Pb budget and Pb contained in secondary Fe oxides is over 1% of the total budget, but these are minimal estimates.

An exploratory study of “large‐n” detrital zircon geochronology of the Book Cliffs, UT via rapid (3 s/analysis) U–Pb dating

AbstractDetrital zircon (DZ) U–Pb geochronology has improved the way geologists approach questions of sediment provenance and stratigraphic age. However, there is debate about what constitutes an appropriate sample size (i.e., the number of dates in a DZ sample, n), which depends on project objectives, sample complexity, and, critically, analytical budget. Additionally, there is ongoing concern about bias introduced by zircon grain size. We tested a recently developed rapid (3 s/analysis) data acquisition method by multicollector laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) that incorporates an automated selection routine and calculates two‐dimensional grain geometry from polished sample surfaces. Eleven samples were analysed from below and above the Late Cretaceous (Campanian) basal Castlegate unconformity of the Book Cliffs, Utah, in a down‐depositional‐dip transect including Price, Horse, Tusher, and Thompson canyons. 12,448 new concordant dates were generated during two measurement sessions. Results are consistent with recent studies suggesting there is no major provenance change and little time (1–2 Myr) represented across the unconformity. Grain size and sample size both exert a strong control on sample dissimilarity. Age distributions constructed from subsamples of large grains are systematically less similar to whole samples; age distributions composed of small grains are overall more similar to whole samples. As such, North American sediment sources that produce large grains such as the Grenville and Yavapi‐Mazatzal belts can bias age distributions if only large grains are analysed. A sample size of n = 100 is inadequate for characterizing age distributions as complex as those of the Book Cliffs, whereas a sample size of n = 300 provides good characterization. Sample size of n ≈ 1000 or more is unnecessary unless project objectives include scanning for subordinate age groups, such as when identifying the youngest grains for calculating a maximum depositional age (MDA). Dates used in MDA calculations acquired with rapid acquisition are best re‐analysed with longer LA‐ICP‐MS acquisition methods or isotope dilution thermal ionization mass spectrometry for increased accuracy and precision. We include new MATLAB code and open‐source software programs, DZpick and DZmda, for automated spot picking and calculating MDAs.

Nd isotope and element composition of shales from the Parnaíba Basin, NE Brazil: Insights for provenance shifts in a cratonic basin

Sm-Nd and Sr isotope compositions of 24 samples of fine-grained clastic rocks from eastern Parnaíba basin, NE-Brazil, are presented along with major and trace element compositions of 19 of these samples. Samples were collected from outcrops of the Paleozoic Canindé (Pimenteiras, Longá and Poti) and Balsas (Piaui Formation) groups, and from the Jurassic Pastos Bons Formation. Discrimination diagrams based on Th, Sc, La and Zr indicate sedimentary provenance from felsic dominant sources and high degrees of crustal recycling. PAAS-normalized REE diagrams show that the Pimenteiras and Longá Formations display flat patterns with slight REE enrichment, and initial εNd and 87Sr/86Sr around the average composition of the upper continental crust, respectively between −8.9 and −14.6 and between 0.711 and 0.760, indicating provenance from old Precambrian basement. The Nd TDM model ages of the Pimenteiras between 1.32 Ga and 2.00 Ga indicate heterogeneity of source areas during the Devonian, and TDM ages around 1.6 Ga in the Longá Formation samples suggest intense recycling of older sediments. The Poti formation samples yield TDM ages of 2.30 Ga and 2.32 Ga, respectively, suggesting tectonic reactivation and new input from Archean-Paleoproterozoic basement complexes. The Pastos Bons Formation samples show lower Th-Sc ratios, light-REE depletion, and less negative initial εNd, indicating contribution from mafic rocks, probably from the underlying Mosquito Formation intraplate tholeiitic basalts and dolerites.

On depositional processes governing along‐strike facies variations of fine‐grained deposits: Unlocking the Little Ice Age subaqueous clinothems on the Adriatic shelf

ABSTRACTDepositional processes recorded by shelf deposits may vary widely along‐strike, depending largely on the mode of delivery and deposition of sediments to the basin. In fine‐grained systems in particular, depositional processes are difficult to reconstruct with standard facies analysis of sediment cores due to the ostensibly featureless and homogenous appearance of muds. In this study, sedimentological, palaeontological, geochemical, and oceanographic data were combined in a detailed characterization of depositional conditions via sedimentary structures, type of organic matter, trace‐metal geochemistry, and benthic fauna assemblages (foraminifera and ostracods) along the 600 km long shelf delta clinothems of the West Adriatic shelf (Italy). Processes inferred from sedimentary facies and micro‐structures were then considered in the context of the modern Adriatic oceanographic regime. Specific attention was given to the Little Ice Age stratigraphic unit (1500–1850 ce), which contains a continuum of genetically related fine‐grained strata. The Little Ice Age deposit offers the opportunity to examine a source‐to‐sink system with the high resolution typical of modern analogues, at a time interval when Apennine rivers were not yet hydraulically engineered with man‐made sediment traps along their trunks. Individual beds within the Little Ice Age muddy prodelta form hectometre to kilometre‐wide bedsets that reflect the interplay between energetic meteo‐ocean conditions (storm‐dominated beds), flood supply (river‐dominated beds or hyperpycnites) and along‐shelf bottom‐current dispersion (drift‐dominated beds). The multidisciplinary approach applied at different scales of observations helped in understanding sediment provenance and the relative timing of sediment transport before final burial that strongly promoted organic matter oxygen exposure and the loss of carbon by microbial degradation. Overall, the distinctive depositional processes that acted in concert along the prodelta slope produced a subtle lateral heterogeneity of preserved sedimentary structures, faunal associations, and organic matter composition in a laterally‐continuous lithostratigraphic unit deposited at centennial scale. These findings have implications on the forcing conditions that ultimately control the location and nature of fine‐grained beds in both modern and ancient, mud‐dominated depositional systems.

Microtextures on quartz grain surfaces in the Bay of Bengal shoreline sediments, Bangladesh: Implications for sediment transport process and depositional environment

SEM and SEM-EDS studies of quartz grains in the shoreline sediments of the Bay of Bengal, Bangladesh were carried out to evaluate the mode of origin, paleoclimate, and depositional environment. A total of 38 microtexture types were identified, which were grouped into mechanical (23 features), mechanical/chemical (6 features), and chemical (9 features) origins. The morphology of quartz grains in the shorelines was dominantly sub-angular to sub-rounded in shape, which represents robust energy conditions, short residence time, low weathering, and nearby sediment provenance. The microtextures of mechanical origin such as straight and curved scratches, pits, broken edges, and crescent-shaped features were relatively abundant in the eastern site samples (Section-I) indicating high-energy, fluvial, and beach environments. The abundance of V-shaped marks and smooth surfaces of quartz grains indicate high-velocity storm conditions and/or high-energy impact events. The well-rounded outline, low relief with dish-shaped depressions, mechanically upturned plates, and arcuate steps were also observed on quartz grain surfaces. These features suggest that they were developed during an aeolian process in the beach berm environment. Etching, solution/irregular pits, and differential relief on quartz grains were somewhat elevated in the western site samples (Section-III), reflecting that these microtextures were associated with a subaqueous collision and humid climates in the fluvial and nearshore environments. Quartz grains in all sections represented microtextures of high energetic subaqueous environment as well as wind events. However, the absence of corrosion channels and high density of voids in the quartz grains revealed low degree of weathering.

Provenance Evolution and Its Response to Sea Level Change in the South Yellow Sea since 1.0 Ma

The sediments provenance of the South Yellow Sea is controlled by many factors such as sea level change, ocean circulation, and neotectonic movement. The short time scale sediments provenance changes in this region since the Holocene have been revealed well, and a unified understanding has been formed that the central muddy area in the South Yellow Sea is a mixed area of the Yellow River sediments and the Yangtze River sediments. However, the contribution of different rivers to the sediments of the South Yellow Sea since late Quaternary is still ambiguous. Through comparative analysis of several boreholes with precise annual data constraints in the central mud area, the process of sediments provenance change at different periods since the late Early Pleistocene (1.0 Ma) was reconstructed, and the coupling mechanism of sediments provenance change and sea level change was established. It is found that during the period from 1.0 to 0.88 Ma, the seawater entered the South Yellow Sea along the Yellow Sea trough from the southeast to north as a channel, and there were different phenomena at the same time in different regions. Since 0.88 Ma, the sea water has been advancing from east to west. In addition, the sediments in the western of Jeju Island are mainly from China, and the sediments in the eastern are mainly from the Korean Peninsula, which roughly coincides with the boundary between the silty area and the sandy area on the eastern of the South Yellow Sea. In the surface sediments, the boundary line between the Yellow River sediments and the Yangtze River sediments is approximately 33.4° N.

The timing of the initial collision between the South and North China blocks constraining from the sediments in the eastern Sichuan Basin

In this study, detrital zircon U–Pb geochronology, trace element and Hf isotopic compositional data from the Early-Middle Triassic clastic rocks in the eastern Sichuan Basin were obtained to distinguish the sediment provenance and constrain the timing of the initial collision between the South China and North China blocks. Detrital zircons from the Early Triassic Feixianguan Formation clastic rocks yield one major age peak at 2476 Ma and three minor age peaks at 1886, 802 and 304 Ma. These detrital zircons may be derived from the South China Block. Detrital zircons from the Early Triassic Jialingjiang Formation clastic rocks yield multiple age peaks at 979, 856, 392 and 269 Ma, indicating a mixed sediment provenance from the South China Block and Qinling Orogenic Belt. This is the first appearance of the detritus with the Qinling Orogenic Belt affinity in the eastern Sichuan Basin. Detrital zircons from the Middle Triassic Leikoupo Formation clastic rocks yield two centralized age peaks at 447 and ca. 245 Ma. These zircons may mainly be derived from the Qinling Orogenic Belt. The results indicate an abrupt change in the detrital zircon U–Pb provenance from the South China Block to the Qinling Orogenic Belt during the Early-Middle Triassic. Integrating the provenance change and other geological characteristics, we suggest that the initial collision in the eastern Qinling Orogenic Belt occurred in the Early Triassic.

Quartz Grain Microtextures in the Paleogene Sosnov Formation: Implications for Sediment Provenance in the Eastern Russian Platform

The purpose of the research. The chief task of the research is to examine the microtextures of quartz grains in the Paleogene Sosnov Formation, which is a sedimentary unit located in the Ulyanovsk-Syzran Volga Region of the Russian Platform. By examining the microtextures, which include mechanical, chemical and mechanical/chemical features, it becomes possible to find out the mechanisms by which grains were transported and subsequently modified. The relevance of the research. The relevance of this research lies in the fact that the analysis of quartz grain microtextures provides valuable insights into sediment provenance of sedimentary deposits is crucial for reconstructing past geological environments and unraveling depositional histories. Research methodology. Twenty quartz grains were collected from sands of the Paleogene Sosnovka Formation, exposed by the Eastern-Tashlinsky and the Kuchurovsky quarries to a depth of 5 and 7.5 m, respectively. The research methodology involved scanning electron microscopy (SEM) to investigate the microtextures of quartz grains. Results and conclusions. The study reveals 19 microtextures types, which were categorized into mechanical, chemical, and combined mechanical/chemical microtextures. An analysis of SEM indicated that chemical microtextures are present in the Paleogene Sosnov Formation, which made it possible to suggest that the sands passed through a low-energy phase during their transition. The data obtained enables us to reconstruct the diverse depositional paleoenvironments, including eolian, subaqueous, mixed subaqueous-eolian, and pedological settings.

Provenance of the Lower Jurassic pyroclastic sediments in the Zigui Basin: Implication for crustal thickening in the eastern Qinling orogenic belt

Provenance of the Lower Jurassic pyroclastic sediments in the Zigui Basin: Implication for crustal thickening in the eastern Qinling orogenic belt

Tectonic significance of the late-Ediacaran syn-orogenic basin in the easternmost portion of the Paraguay Belt, Tocantins Province, central Brazil

Sedimentary provenance studies using detrital zircon U–Pb ages represent an important tool to investigate the evolution of orogenic basins and to suggest tectonic settings and paleogeography reconstructions when it comes to supercontinent modeling. Syn-orogenic basins worldwide are characterized by a large proportion of zircons with ages close to the maximum depositional period, reflecting the proximity of recently formed magmatic rocks. In this work, we combine field observations, detrital zircon U–Pb ages, whole-rock Sm–Nd and mica Ar–Ar isotopic analyses to constrain the final tectonic evolution of a restricted basin located in a poorly studied region at the easternmost limit of the Paraguay Belt in the Tocantins Province, central Brazil. The investigated area corresponds to the boundary sector of the Paraguay Belt and the Brasília Belt and is also transected by the strike-slip fault system associated with the Transbrasiliano Lineament. This sector was previously mapped as part of the Cuiaba Group, internal zone of the Paraguay Belt. We provide 465 new detrital zircon U–Pb data with ages distributed from the early Cambrian to the Archean, with approximately 60% of the analyzed grains derived from Ediacaran-Cryogenian sources. The maximum depositional age of the basin is defined at ca. 590 Ma, constrained by the youngest age peak and an evident provenance shift in detrital input in the Paraguay Belt was demonstrated. The syn-orogenic character of the basin is inferred based on the main peak of the detrital zircon population age distribution around 600 Ma, which is very close to the maximum depositional period and points to a short time between erosion, deposition, and burial processes. The muscovite 40Ar/39Ar age of ca. 536–546 Ma obtained for muscovite schist metamorphosed under greenschist facies conditions indicates that the regional thermal regime was maintained up to the early-Cambrian in the area. The minimum fast cooling rate of 25 °C/Myr defined in the investigated area is constrained by the 40Ar/39Ar analysis of biotite (549.16 ± 1.30 Ma) from a syn-to late-kinematic granodiorite intrusion. The very rapid magma emplacement occurred into relatively shallow crustal levels through the associated strike-slip faults. The Transbrasiliano Lineament would have facilitated the rapid unroofing of the study area and therefore the syn-orogenic deposition in a foreland domain at the final phase of West Gondwana amalgamation. The studied metasedimentary rocks represent a transition phase from the passive margin sedimentation (Cuiabá Group) to an orogenic phase, constraining an inversion event in the West Gondwana around ca. 590 Ma. The data provide evidence of a late orogenic basin that was formed contemporaneously with the evolution of an active margin between the Amazonian Craton and the eastern blocks/cratons (São Francisco-Congo and Rio de la Plata cratons and Paranapanema Block) close to Cambrian times. Our results support the existence of the younger Clymene Ocean and the subsequent final assembly of West Gondwana in the Cambrian.

Lead isotope compositions and modern sediments sources in the radial sand ridges from the Jiangsu coast, East China

The formation of the Jiangsu radial sand ridges (RSRs) in East China has received extensive attention. However, the provenance of the Jiangsu RSRs sediments is still controversial. In this study, the Pb isotopic compositions of residual fractions were used to elucidate the provenance of the Jiangsu RSRs sediments. The results showed that Pb isotopic compositions of sediments in onshore RSRs were not significantly different with those of the landward offshore RSRs, indicating the shoreward transport of sediments from the landward offshore RSRs. The combination of Pb–Nd isotopic compositions revealed that the seaward offshore sediments mainly originated from the Yangtze River Mouth, while the onshore and landward offshore sediments were dominantly supplied by the Old Yellow River Delta through the southward flow. This study provides a deep insight into the evolution of Jiangsu RSRs, and is of great value to the Jiangsu coastal protection.

Facies analysis, provenance and tectono-depositional evolution of the Ediacaran Hammamat molasse sediments, Umm Tawat area, North Eastern Desert, Egypt

The Ediacaran Hammamat Sediments in the Umm Tawat basin of the Egyptian North Eastern Desert are exposed with an ENE-trend, along with the Dokhan Volcanics and various phases of intrusive rocks. Different lithofacies of molasse-type deposits exist, with a debate about their tectono-depositional setting, provenance, and diagenesis versus metamorphism. In this study, we present a new insight into the facies and evolution of Umm Tawat sediments using an integrated structural, sedimentological, and mineralogical approach. Lithofacies analysis revealed their deposition in continental suites of alluvial fans, braided fluvial channels, and lacustrine environments. The sediments were derived from proximal heterogeneous sources of intermediate and acidic igneous rocks and a subordinate sedimentary provenance conveyed from uplifted basin margin hinterlands. Petrographic, SEM-EDX, and XRD data imply that the HS were affected by diagenesis to very low-grade metamorphism and local thermal metamorphism in contact with the intrusive younger granite. Carbon smears possibly derived from organic matter in shale were observed. Two reconstructed paleostress phases derived from fault slip data with the sedimentological analysis constrain the tectono-depositional evolution of the Umm Tawat molasse basin. We propose an early development of ENE-asymmetric sedimentary depocenter associated with the N–S-directed extensional strike-slip stress regime. Syn-tectonic deposition of the Hammamat Sediments occurred during this phase in three stages with variable sediment provenance and accommodation/sediment influx ratios. This phase was accompanied by the three phases of younger granites and the Dokhan volcanics. Positive inversion with N–S-directed compressional strike-slip stress regime caused ENE-to NE-folding and reverse reactivation for the pre-existing ENE-trending dextral faults. Up on the regional correlation, the Ediacaran Umm Tawat molasse basin differs somewhat from other molasse basins in the central Eastern Desert regarding their facies and tectono-depositional model. This basin probably formed as a continental intra-arc basin located in the northern region of the Nubian Shield.

Early development of the Patagonian fold and thrust belt and the onset of foreland sedimentation in the Austral-Magallanes basin

Retroarc basins register the onset of compressional exhumation during the Cretaceous in the Andes, evidenced by sequences showing sedimentary provenance from the orogen. We present U–Pb detrital zircon geochronology from the Austral-Magallanes basin in the Southern Patagonian Andes (∼47–48°SL), where the foreland stage began in the Early Cretaceous. The littoral sandstones from basal foreland sequences of the Río Belgrano Formation yield ∼123 Ma maximum depositional ages, confirming previous studies that the basin infill is early Aptian. The detrital zircon ages showed two main clusters of 129-115 Ma and 151 -140 Ma, that are derived from the coetaneously exhumed Andean arc and earlier Jurassic magmatic sources. The zircons which overlap with ages of Upper Jurassic Andean synrift volcanics, confirms orogenic exhumation coeval with sedimentation. A sequence of retroarc volcanism dated between 119 and 97 Ma overlies the basal foreland littoral-continental deposits, and it is followed by a Late Cretaceous-Paleocene hiatus. Further analysis of detrital zircons ages distribution and geological considerations, indicates that the studied northern depocenter was a source region of sedimentary supply after its Cenomanian exhumation.

Holocene provenance variations and palaeofloods response to ENSO-driven monsoon precipitation in the subalpine peatland in southern China

There have been few investigation of the provenance of sediments and hydrological response to past climatic change in the subalpine peatland in southern China. The source of sediments and regional climatic variations during the Holocene have been deduced from Rare Earth Elements (REEs), SrNd isotopic data and grain size end-member modeling analysis (EMMA) derived from peat sediments from the southwestern mountainous region of Hunan Province, China. From the distinctive SrNd isotopes patterns, LREEs enrichment, and the Eu anomaly observed in these sediments, it can be concluded that local weathering residues have been the primary sedimentary source throughout the Holocene. Based on the method of EMMA, four distinct end members were identified. EM2, signifying weathering products of moderate particle size, is sensitive to climate variations. This sensitivity makes it an effective marker to track the historical evolution of the East Asian summer monsoon (EASM) intensity. The results suggest that the prevalence of the relatively weak EASM during the interval 11,600–9000 cal yr BP, followed by an overall weakening trend during the past 9000 years. EM3 + EM4, the coarsest component in the peat sediments, indicate strong runoff typically caused by the extreme weather events. Notably, the occurrence of relatively high EM3 + EM4 component during the interval 5400–4500 cal yr BP and 3500–2600 cal yr BP is consistent with the previous reported palaeoflood events in the Yangtze River basin. We suggest that the regional flood patterns are predominantly controlled by the East Asian monsoon system, which in turn, is driven by ENSO activities. For a comprehensive understanding of regional flood patterns, it is imperative to extend research into high-altitude areas.

Paleoweathering and Detrital Provenance of Balangbaru Shale, in South Sulawesi

Sulawesi Island, known for its geological complexity, offers a unique opportunity for researchers to investigate further into sedimentary basins particularly in South Sulawesi area. The Cretaceous Balangbaru Shale is one of the rocks that has an extensive distribution in South Sulawesi especially in the western part. Due to limitation of geological information related to this formation we performed the paleodepositional investigation to elucidate the paleoweathering, geochemistry characterization, and detrital provenance of the Balangbaru Shale. Indeed, previous studies have demonstrated that fine-grained sedimentary rocks can serve as valuable archives of geochemical information, enabling the reconstruction of paleoclimate evolution during the deposition period. Employing XRF quantitative analysis, we examine the dispersion of major elements within eight distinct layers of the Shale. Additionally, comprehensive whole-rock analyses enable us to ascertain the abundance of major elements and subsequently deduce detrital SiO2 and biogenic SiO2 content, thereby comprehending the inorganic geochemical composition of the Balangbaru Shale.The present study seeks to address the limited understanding of the geochemical properties of the Balangbaru Shale, specifically pertaining to paleoweathering intensity and detrital provenance. Acknowledging the scarcity of recent data available on the subject matter, this research aims to bridge the limitation data gap by conducting an in-depth investigation into the geochemical characteristics of the Balangbaru Shale by employing major oxides concentrations (SiO2, Al2O3, Fe2O3, K2O, P2O5, MgO, CaO, Na2O, MnO, TiO2, Cr2O3) and trace elements (Sr, Cu, Ba, Th, Ni, V, Th, U) into the equations such as C-value, chemical index alteration (CIA), plagioclase index of alteration (PIA), weathering index of parker (WIP) and ratio of Rb/Sr, U/Th, Sr/Cu, Sr/Ba. Furthermore, the major oxides ratio of Al2O3/TiO2 and TiO2/Zr were performed to specify the sediment provenance and the source-area rock compositions of the Balangbaru Shale. The obtained data reveals a moderate to high degree of weathering intensity in the detrital source environment of the Balangbaru Shale, suggesting warm to humid climate conditions in the source region. Additionally, the analysis of the detrital fraction indicates the possible origin of the Balangbaru Shale from felsic rocks. Overall, these findings contribute significantly to the understanding of paleoenvironmental conditions associated with the Balangbaru Shale, shedding light on its geological history.

Geochronology, geochemistry, and tectonic setting of Ordovician metavolcanic rocks in the Liberty–Orrington belt, Maine: implications for the evolution of peri-Gondwanan arcs in the northern Appalachians

The Yarmouth Island Formation of the East Harpswell Group (EHG) is an assemblage of metamorphosed volcanic and sedimentary rocks exposed in Casco Bay, Maine. Although previously interpreted to have been deposited ca. 445 Ma, two new U–Pb zircon ages from metavolcanic rocks in the unit indicate prolonged magmatism between ca. 469–474 Ma and correlation with adjacent rocks of the more regionally extensive Casco Bay Group (CBG) in the Liberty–Orrington belt. New detrital zircon results from metasedimentary rocks in the EHG support this correlation; the age spectra indicate a peri-Gondwanan sedimentary source, consistent with earlier published results from the CBG. Detailed geochemical studies of the metavolcanic rocks in the Yarmouth Island Formation indicate a wide range of sub-alkaline compositions (SiO2 = 47.9–77.5 wt.%), flat chondrite-normalized rare earth element distributions, and a prominent negative Nb anomaly in normalized spider plots. Tectonic discrimination plots suggest eruption in a volcanic arc setting with continental crustal influence. This tectonic setting, when combined with the co-existence of marine sedimentary rocks, suggests a transitional setting between that of subduction and subsidence in a marine setting, perhaps due to the onset of back-arc rifting. Similarities in age, lithologic character, sediment provenance, and volcanic rock geochemistry indicate a strong correlation between these rocks in the Liberty–Orrington belt and those along strike in the southern portion of the Miramichi belt of eastern Maine and southern New Brunswick. These findings confirm the preservation of >500 km long, ca. 470 Ma, arc/back-arc terrane within the Ganderia superterrane in the northern Appalachians.

Geochemical Compositions of Size‐Fractioned Sediment Samples From the Yangtze and Yellow Rivers: Implications for Chemical Weathering, Fractionation Behavior of Provenance Tracers, and Sources of Radial Sand Ridges

AbstractRiver sediments are valuable archives of the environmental conditions within their catchments. The Yangtze and Yellow Rivers are the most active fluvial systems for sediment transport in East Asia, and they are regarded as potential sediment sources for the radial sand ridges (RSRs) in the southwestern Yellow Sea. We used the geochemical compositions of size‐fractioned sediment samples from the Yangtze and Yellow Rivers to characterize chemical weathering, the fractionation behavior of provenance tracers, and the sources of RSRs. For the Yangtze and Yellow River sediments, the (Rb + Sr)/Ti ratio is a reliable chemical weathering proxy that is grain‐size independent. The chemical indices of Chemical Index of Alteration, Rb/Sr, (Rb + Sr)/Ti, and acid‐leached elements from common grain‐size fractions together reveal that the Yangtze River basin undergoes stronger chemical weathering than the Yellow River basin, indicating that the chemical weathering is dominated by latitudinally‐dependent climatic variations. The dissolution and precipitation of amorphous Fe‐Mn oxides can result in the significant fractionation of La/Y, La/Sc, Nb/Co, La/Co, (La/Sm)N, (La/Yb)N, Ti/Sc, Zr/Y, Zr/Co, and Cr/Ta, whereas Zr/Ti and Zr/Nb are largely unaffected. Based on the robust provenance tracers of Zr/La, La/Hf, (La/Yb)N, Zr/Nb, Ti/Zr, and Hf/Ta, we conclude that the RSRs in the southwestern Yellow Sea are mainly derived from Yangtze River sediments, and that part of the clay fraction is from the Yellow River. In future research, we suggest that established geochemical indicators of chemical weathering and sediment provenance can be applied to the deposits of the Yangtze and Yellow River Deltas, the Yellow Sea, and the East China Sea.

From Outcrop to Spectrum—An Automated Approach to Modal Mineralogy of Silt‐Sized Sediment Applied to Central European Loess

AbstractProvenance information from recent and ancient sedimentary archives is obscured by several factors and for disentangling these intermingled signals, analysis by multiple methods is paramount. In sedimentary provenance analysis (SPA), single‐grain methods determining mineralogy, chemical composition, or radiometric ages are of key importance but are mostly applied to sand‐sized sediments or sedimentary rocks. Finer grained sediments or sedimentary rocks are usually analyzed by whole‐rock geochemical means and seldom by single‐grain methods. Considering the abundance of fine‐grained sedimentary archives, a strong need for single‐grain, multi‐method analyses of silt‐sized sediments is obvious. Thus, we propose a workflow that is optimized for sample throughput and correlative analysis of fine‐grained sediments based on machine learning methods. The feasibility of the workflow is demonstrated by differentiating three Central European loess‐paleosol‐sequences. The increased sample throughput enables access to sedimentary archives at high spatial and/or temporal resolution, which will open up new research pathways in SPA of silt‐sized sediments.

Changes of sediment provenance driven by the sea level and Indian summer monsoon in the northern Ninetyeast Ridge over the past 50 kyr

The Ninetyeast Ridge is situated within the world's largest sediment “source-sink” system, which extends from the Tibetan Plateau to the Bay of Bengal (BoB). Modest and stable sedimentation rate makes it a suitable region for studying long-term land-sea interaction. Recent research has primarily focused on the northern Bengal Fan, leaving limited knowledge about sedimentary processes on the distant Ninetyeast Ridge. This study aims to address this gap by investigating sediment transport pattern and its response to climatic and environmental changes since the last glacial period, using the gravity core (CJ04–50) selected from the northern Ninetyeast Ridge. The provenance discrimination based on δEu-(Gd/Yb)N revealed that the Irrawaddy (Irr) River, along with the Ganges-Brahmaputra (G-B) Rivers, represented the primary sources of the study area. Quantitative analysis equations indicated that the contribution of the G-B Rivers decreased from the last glacial period (22%) to the Holocene period (16%), while that of the Irr River increased (from 78% to 84%). Chemical index of alteration (CIA*) values, and terrigenous input proxy indicators (Ti/Ca, Rb/Sr) were used to indicate the changes of weathering and terrigenous input over the past 50 kyr. During the last glacial period, CIA*, Ti/Ca and Rb/Sr revealed significantly millennial-scale periodic changes, including the distinct declining trend during the Last Glacial Maximum (LGM) and Heinrich 2–4 (H2-H4) periods, followed by recovery trend during subsequent warm periods. During these cold periods of LGM and H2–H4, weakened Indian monsoon condition, reduced precipitation, cold climate, and expanding ice sheets, adversely affected physical erosion and chemical weathering in the source area, and the reduced river runoff impeded sediment transport. Conversely, these environmental factors reversed during relatively warm periods. Since the Holocene, CIA*, Ti/Ca and Rb/Sr declined, which was contrast to the climate change, and the sea level changes became the dominant factor. The rapidly rising sea level submerged the main terrigenous input channel (the Swatch of No Ground) of the G-B Rivers, made the depositional center shift from the Bengal Fan to the continental shelf, causing the decline of terrigenous input and lower CIA* values.

Geochronology, provenance, and tectonic setting of the meta-sedimentary rocks from the North Shahrekord metamorphic Complex, Iran

ABSTRACT The meta-sedimentary rocks from the North Shahrekord metamorphic Complex (NSMC) comprise micaschists, paragneisses, quartz-feldspathic schists, and marbles. Detrital zircons from the paragneisses yield ages of ca. 2811–507 Ma with most of the dated grains belonging to the Late Neoproterozoic to Cambrian, suggesting a maximum depositional age of the sedimentary protolith during the Late Ediacaran to the Early Cambrian times (543 ± 12 Ma). In contrast, detrital zircons from the quartz-feldspathic schists are mostly dominantly 692–577 Ma and a few at ca. 2369–703 Ma, suggesting that the maximum depositional age of 577 ± 9 Ma, Late Neoproterozoic. The age distribution of detrital zircons suggests that their main provenance was located within the Arabian-Nubian Shield and adjacent terranes. Rutiles from a paragneiss give a U-Pb lower-intercept age of 181 ± 3 Ma, indicating the occurrence of a high-pressure metamorphic event during the Early Jurassic. The trace element contents of the two rock units show enrichment in LREE relative to HREE and negative Eu anomalies, indicating upper continental crustal sources. The geochemical evidence (e.g. low to moderate Chemical Index of Alteration (CIA) and Plagioclase Index of Alteration, high Index of Compositional Variability (PIA), and low Th/U) suggests that the quartz-feldspathic schists and paragneisses originated from an immature, and immature to less mature, respectively, intermediate-felsic igneous source and their protolith experienced a simple sedimentary recycling history with relatively weak to moderate chemical weathering. Geochemical and petrographic data also suggest that the precursor to the quartz-feldspathic schists and paragneisses were deposited in a continental island arc and a back-arc basin setting, respectively. Our new data, including depositional age, provenance, and geochemical evidence, provide perspectives on palaeogeographic affinities (provenance of sediments with different weathering and recycling materials), and paleotectonic reconstructions (from arc to back-arc) of the Iranian basement, exposed in the Sanandaj-Sirjan Zone, during Ediacaran.