GSA Bulletin最新文献

{"title":"Bifurcation of mantle plumes by interaction with stagnant slabs in the mantle transition zone: Evidence from late Cenozoic basalts within Southeast Asia","authors":"Fan Yang, Xiao-Long Huang, Yi‐Gang Xu, Pengli He","doi":"10.1130/b36558.1","DOIUrl":"https://doi.org/10.1130/b36558.1","url":null,"abstract":"Mantle plumes can encounter stagnant slabs in the mantle transition zone (MTZ) during their ascent from the lower mantle to Earth’s surface. However, the interactions between stagnant slabs and mantle plumes remain poorly understood. This study presents new data on the spatial thermal−lithological−chemical heterogeneity in the mantle over a vast area of Southeast Asia that reflects the variable influence of a late Cenozoic mantle plume. Site U1433 of International Ocean Discovery Program (IODP) Expedition 349 in the southwest sub-basin of the South China Sea (SCS) is located near the center of this seismically imaged mantle upwelling. This area also contains mid-ocean ridge basalt (MORB) derived from a peridotite-dominated and normal temperature mantle source with a depleted Nd-Hf and enriched 207Pb/206Pb isotopic composition. In contrast, MORB from Site U1431 of IODP Expedition 349 within the eastern sub-basin of the SCS and other intraplate basalts from the Hainan-Leizhou area, the eastern Indochina block, and elsewhere in the SCS are dominantly sourced from higher temperature pyroxenite-enriched mantle material that records mantle plume activity. These observations are in contrast with previous models involving a single plume rising from the lower mantle beneath the SCS that then tilted toward Hainan Island, China. Instead, it is likely that the observations from this region are indicative of plume-stagnant slab interaction. The shallow upper mantle beneath Site U1433 has not been influenced by a mantle plume as the presence of stagnant slabs within the MTZ prevented further upwelling of the plume. In contrast, a mantle plume passed through the weaker MTZ within the eastern sub-basin and circum-SCS areas, allowing plume-related magmatism to occur. The bifurcation of a deep-rooted mantle plume by stagnant slabs in the MTZ produced a cluster of small mantle upwellings that ascended to shallow depths, consistent with new multiscale global tomographic data for Southeast Asia.","PeriodicalId":242264,"journal":{"name":"GSA Bulletin","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114055695","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Genesis and source affinities of heterogeneous ultramafic rocks in the North Kongling Complex, Yangtze craton: Architecture of a Paleoproterozoic accretionary orogen","authors":"Hongtao Peng, H. Deng, Q. Han, S. Peng, A. Polat, T. Kusky","doi":"10.1130/b36649.1","DOIUrl":"https://doi.org/10.1130/b36649.1","url":null,"abstract":"Ultramafic massifs are minor but meaningful components of orogens because they record the mantle properties and the processes of plate generation, subduction, accretion, and collision, thus providing key information about crust-mantle interaction processes and the evolution of orogens. Here, we present an integrated study of field observations, whole-rock and mineral geochemistry, zircon U-Pb ages, and whole-rock Sm-Nd and Re-Os isotopes for serpentinized harzburgites and olivine pyroxenites from the Paleoproterozoic Shuiyuesi mélange belt, North Kongling Complex, to constrain the tectonic evolution of the Yangtze craton, South China. The serpentinized harzburgites are characterized by enrichment of light rare earth elements (LREEs) and negative εNd(t) (−4.3 to −3.9) values, but they have high olivine Mg# (91.7−93.1) and very low Re contents (<0.09 ppb) and negative γOs(t) (−5.1 to −4.0) values. The Archean Re-Os model ages (TRD = 2.82 Ga) of the harzburgites that have the most depleted Re-Os isotope composition represent estimates for the age of the initial melt extraction. Metasomatic zircons from the serpentinized harzburgites yield a weighted average age of ca. 2.04 Ga, which is interpreted to represent the age of metasomatism during a subduction event. These geochemical and isotopic features and geochronologic results suggest that the protolith of the serpentinized harzburgites in the North Kongling Complex originated as fragments of late Mesoarchean (ca. 2.82 Ga) subcontinental lithospheric mantle and experienced melt/fluid metasomatism in a subarc mantle wedge at 2.04 Ga. The olivine pyroxenites are cumulates, and they are characterized by high MgO, Ni, and Cr contents and depleted to slightly enriched LREEs but depletion in high field strength elements (HFSEs). They have positive εNd(t) (+2.0 to +6.6) values and Paleoproterozoic Nd model ages (2.41−2.05 Ga), suggesting that the olivine pyroxenites were derived from a Paleoproterozoic depleted mantle source. Metamorphic zircons from the olivine pyroxenites indicate subsequent metamorphism at 2.0 Ga, in response to a collision. The olivine pyroxenites together with the metabasites in the Shuiyuesi mélange belt represent the dismembered fragments of oceanic lithosphere that formed in a suprasubduction zone during the Paleoproterozoic. Combined with the Archean and Paleoproterozoic rocks in the North Kongling Complex, it appears that the Mesoarchean subcontinental lithospheric mantle peridotites and Paleoproterozoic ophiolitic rocks were simultaneously accreted during a Paleoproterozoic orogenic event. We further propose that a subduction channel may have played an important role in the architecture of the accretionary orogen, in which both oceanic lithospheric materials and subcontinental lithospheric mantle wedge materials would have been simultaneously scraped off and accreted during slab subduction-accretion.","PeriodicalId":242264,"journal":{"name":"GSA Bulletin","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116739698","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reservoir characterization and geologic modeling of the Lower Cretaceous Muddy Formation at Bell Creek Field, Montana, USA","authors":"Essam F. Sharaf, H. Sheikha","doi":"10.1130/b36536.1","DOIUrl":"https://doi.org/10.1130/b36536.1","url":null,"abstract":"The Lower Cretaceous Muddy Formation at the Bell Creek Field, Montana, USA, is characterized by a clastic sequence of mixed lithofacies. An integrated workflow was applied to define the reservoir compartments and distribution of petrophysical properties throughout the central and northern areas of the field. The workflow focused on the heterogeneity of the reservoir flow units, diagenetic complexities, and the associated compartments. The compartments play a considerable role in controlling the connectivity and fluid flow through the reservoir. Descriptions of the reservoir properties were used as inputs to a three-dimensional (3-D) geologic model for history matching and prediction of CO2 flooding. History matching of the primary production of the Muddy Formation helped to improve understanding of the distribution of the rock and fluid properties. The simulation model was then used to forecast future CO2 flooding in the study area. Following CO2 injection, the collected production data were utilized to verify the validity of the model by comparing the production forecast with the actual field results. The simulation model successfully predicted the CO2 flood response, pressure, and production data.","PeriodicalId":242264,"journal":{"name":"GSA Bulletin","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133005762","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Astronomically forced climate variability across the Eocene−Oligocene transition from a low latitude terrestrial record (Lühe Basin, South China)","authors":"Ke Xu, D. Kemp, Jianye Ren, W. Qian","doi":"10.1130/b36588.1","DOIUrl":"https://doi.org/10.1130/b36588.1","url":null,"abstract":"Across the late Eocene to early Oligocene, Earth’s climate underwent a dramatic shift from Greenhouse to Icehouse, known as the Eocene−Oligocene transition (EOT). This globally synchronous climatic event is well-documented in marine records. However, there is a relative paucity of terrestrial records, particularly at low latitudes. In this study, we present a continuous and high-resolution terrestrial record across the EOT from the low-latitude Lühe Basin, Yunnan Province, South China. Combined with published magnetostratigraphy and 40Ar/39Ar dating of volcanic ashes in the Lühe Basin, we have constrained this record with a robust astronomical timescale. Our results, combined with previously published data from the region, reveal that the Lühe Basin experienced significant environmental and climate changes, from humid/warm to semi-humid/cool conditions, across the EOT. Cyclostratigraphic analysis of high-resolution elemental data reveal a significant switch in orbital forcing, from dominant eccentricity before ca. 34 Ma to combined eccentricity-obliquity-precession cycles after ca. 34 Ma. Atmospheric CO2 decline and subsequent Antarctic glaciation may have been a contributing factor in driving this orbital transition.","PeriodicalId":242264,"journal":{"name":"GSA Bulletin","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129268082","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evidence of the evolution of the East Antarctic Ice Sheet on the continental slope and rise sedimentary record: Insights from the Sabrina Coast, East Antarctica","authors":"F. Donda, R. Romeo, G. Leitchenkov, D. Gei, Y. Rosenthal, A. Leventer, E. Lodolo, T. Noble, A. Post, P. O'Brien, B. Opdyke, Elisabetta Olivo","doi":"10.1130/b36674.1","DOIUrl":"https://doi.org/10.1130/b36674.1","url":null,"abstract":"Deciphering how the Antarctic Ice Sheet has responded to past climate warming is critical to understanding its sensitivity and role in current and future climate change. In this context, knowledge of the evolution of the Antarctic Ice Sheet in catchments with large potential sea-level contributions plays a key role. The Sabrina Coast of East Antarctica lies seaward of the second largest, but least known, subglacial basin on Earth, the Aurora Subglacial Basin. It is part of the East Antarctic Ice Sheet and drains to the Sabrina Coast via the Totten Glacier, the third largest drainage system in East Antarctica. Our refined, comprehensive seismic stratigraphic analysis of a large multichannel seismic data set collected in this sector of the Antarctic margin shows that sediments deposited on the continental slope and rise of the Sabrina Coast retain a well-preserved record of variations in glacial and oceanographic dynamics. Isobath and isopach maps evidence a complex, asymmetric evolution of the Sabrina slope and rise, with the western sector being the main sediment depocenter since the emplacement of the East Antarctic Ice Sheet, as indicated by the up to 4-km-thick glacial-related sequences and inferred sedimentation rates of up to 300 m/m.y. However, significant sediment accumulation also occurs in the eastern area, particularly in the western levees of the canyons. Our findings highlight the potential of this region for deep ocean drilling that will provide an unprecedented history of the dynamics of the marine-based ice sheet in the Aurora Subglacial Basin and its sensitivity to climate change under different background climate conditions.","PeriodicalId":242264,"journal":{"name":"GSA Bulletin","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126079728","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Constraints on the thermal evolution of metamorphic core complexes from the timing of high-pressure metamorphism on Naxos, Greece","authors":"Thomas N. Lamont, A. Smye, N. Roberts, M. Searle, D. Waters, R. White","doi":"10.1130/b36332.1","DOIUrl":"https://doi.org/10.1130/b36332.1","url":null,"abstract":"Metamorphic core complexes are classically interpreted to have formed during crustal extension, although many also occur in compressional environments. New U−(Th)−Pb allanite and xenotime geochronologic data from the structurally highest Zas Unit (Cycladic Blueschist Unit) of the Naxos metamorphic core complex, Greece, integrated with pressure−temperature−time (P−T−t) histories, are incorporated into a thermal model to test the role of crustal thickening and extension in forming metamorphic core complexes. Metamorphism on Naxos is diachronous, with peak metamorphic conditions propagating down structural section over a ∼30−35 m.y. period, from ca. 50 Ma to 15 Ma. At the highest structural level, the Zas Unit records blueschist-facies metamorphism (∼14.5−19 kbar, 470−570 °C) at ca. 50 Ma, during northeast-directed subduction of the Adriatic continental margin. The Zas Unit was subsequently extruded toward the SW and thrust over more proximal continental margin and basement rocks (Koronos and Core units). This contractional episode resulted in crustal thickening and Barrovian metamorphism from ca. 40 Ma and reached peak kyanite-sillimanite−grade conditions of ∼10−5 kbar and 600−730 °C at 20−15 Ma. Model P−T−t paths, assuming conductive relaxation of isotherms following overthrusting, are consistent with the clockwise P−T−t evolution. In contrast, extension results in exhumation and cooling of the crust, which is inconsistent with key components of the thermal evolution. Barrovian metamorphism on Naxos is therefore interpreted to have resulted from crustal thickening over a ∼30−35 m.y. time period prior to extension, normal faulting, and rapid exhumation after a thermal climax at ca. 15 Ma.","PeriodicalId":242264,"journal":{"name":"GSA Bulletin","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131330378","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Magmatic records of subduction and closure of the Meso-Tethys Ocean in the northern-central Tibetan Plateau","authors":"Wei Wang, Qing-guo Zhai, Pei‐yuan Hu, Yue Tang, Hai-tao Wang, Zhicai Zhu","doi":"10.1130/b36593.1","DOIUrl":"https://doi.org/10.1130/b36593.1","url":null,"abstract":"The evolution of the Tethys Ocean has received much research attention; however, the timing and subduction mechanisms involved in the closure of the Bangong-Nujiang Meso-Tethys Ocean remain poorly constrained. In this study, we present geological, geochronological, geochemical, and zircon isotopic data from Cretaceous magmatic rocks and combine these with previously published data within the central Bangong-Nujiang suture zone in the north-central Tibetan Plateau. The integrated data update the regional tectonic framework and enable a comprehensive geodynamic model to be developed for the subduction and ocean closure events. In detail, temporal and spatial variations in the Jurassic−Cretaceous magmatism reflect the influence of the northward subduction of the Dongqiao-Amdo oceanic basin and the bidirectional subduction of the Bangong-Nujiang Meso-Tethys oceanic crust. The evolution of the Bangong-Nujiang Meso-Tethys Ocean further involved initial intra-ocean subduction, slab rollback, and flat subduction, as evidenced by two phases of north-south migration of magmatism at ca. 190−160 and 160−130 Ma and a magmatic hiatus at 160−140 Ma. The ocean closed during a two-stage process, including the closure of the Dongqiao-Amdo oceanic basin to the north and the Bangong-Nujiang Meso-Tethys Ocean to the south. The Dongqiao-Amdo oceanic basin closed soon after ca. 180 Ma, accompanied by continent-continent collision between the Amdo microcontinent and the South Qiangtang terrane. The Bangong-Nujiang Meso-Tethys Ocean closed at 130−120 Ma, corresponding to a period of waning magmatism. This closure represented complete oceanic closure and caused an arc-continent collisional event involving the Baingoin magmatic arc, the Amdo microcontinent, and the Lhasa terrane. The Lower Cretaceous terrestrial strata and their basal unconformity mark the final closure of the ocean, and the Early Cretaceous ocean islands might have formed before ca. 130 Ma.","PeriodicalId":242264,"journal":{"name":"GSA Bulletin","volume":"52 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133494103","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Contemporaneous crust-derived I- and S-type granite magmatism and normal faulting on Tinos, Delos, and Naxos, Greece: Constraints on Aegean orogenic collapse","authors":"Thomas N. Lamont, N. Roberts, M. Searle, N. Gardiner, P. Gopon, Y. Hsieh, Philip Holdship, R. White","doi":"10.1130/b36489.1","DOIUrl":"https://doi.org/10.1130/b36489.1","url":null,"abstract":"Granitoids of varying mineralogy are exposed on the Cycladic islands of Greece; they include both hornblende-bearing I-type granites and garnet ± muscovite−bearing S-type granites, suggesting heterogeneous magma sources. In this contribution, we present new field observations, major- and trace-element geochemistry, Sr-Nd isotopes, and U-Pb geochronology of granitoids from Tinos, Delos, and Naxos that provide insight into these magma sources, along with the timing of adjacent extensional structures. I-type (biotite and hornblende-biotite) granites have initial 87Sr/86Sr = 0.70956−0.71065 and εNd(t) = −6.3 to −9.3, and S-type (garnet ± tourmaline-muscovite) leucogranites have overlapping initial εNd(t) = −7.5 to −10.1, with initial 87Sr/86Sr values overlapping as well as extending to higher values (0.70621−0.73180). These isotope signatures are comparable to those of the Variscan-age Cycladic basement, but not the Hellenic arc. We suggest that both I- and S-type granites were derived via crustal anatexis of variable sources, dominantly metaigneous and metasedimentary, respectively, during the climax of Barrovian metamorphism between ca. 17 and 12 Ma, and critically, they are not related to the Hellenic subduction zone. I-type granitoids were likely derived from dehydration melting of igneous Variscan- or Cadomian-aged basement protoliths, whereas S-type leucogranites formed by muscovite dehydration melting of sedimentary protoliths. Top-to-the-(N)NE shear zones on Naxos and Tinos were active from ca. 20 to 15 Ma and are folded and cut by later low- and high-angle normal faults. S-type leucogranites at Livada Bay, Tinos, dated at ca. 14 Ma, are cut by domino-style normal faults, placing a maximum age on the timing of extension. This is similar to ca. 15−14 Ma dates from NNE-SSW horizontally boudinaged S-type granites on Naxos. We propose that the concurrent intrusion of both I- and S-type granitoids with the onset of normal faulting marked the transition from an overall compressional to an extensional stress field associated with orogenic collapse at ca. 15 Ma.","PeriodicalId":242264,"journal":{"name":"GSA Bulletin","volume":"112 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123540837","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Magmatic-hydrothermal evolution of long-lived Nb-Ta-(Sn) mineralization in Lianyunshan, NE Hunan, South China","authors":"Nuerkanati Madayipu, Huan Li, Safiyanu Muhammad Elatikpo, M. Förster, Hou-Xiang Zhou, Han Zheng, Qian-hong Wu","doi":"10.1130/b36591.1","DOIUrl":"https://doi.org/10.1130/b36591.1","url":null,"abstract":"The Lianyunshan Complex (LYSC) is a Nb-Ta-Li-Be rare metals mining area in northeastern Hunan, South China. The deposit is composed of a granite-type rare-metal pegmatite mineralization that occurs as dikes around the LYSC. The present study examines the genetic relationship, fluid evolution, and metallogeny of the co-developed ore-free pegmatite (OFP) and ore-bearing pegmatite (OBP) in granite-related pegmatite-type Nb-Ta rare-metal deposits in the LYSC. Four minerals: columbite-tantalite (coltan), zircon, cassiterite, and monazite were investigated for their chemical and isotopic compositions. The coltan grains range from homogeneous crystals to zoned varieties with growth rims that result from equilibrium and disequilibrium reactions due to local changes in the physical and chemical conditions. These structures were altered by later metasomatic replacement processes related to the hydrothermal fluid activity and produced structures such as alteration rims, patches, irregular zonations, and complex zonations, with a corresponding increase in Ta. Coltan in OBP yielded two weighted mean 206Pb/238U ages of 135.9 ± 2.1 Ma and 120.5 ± 1.2 Ma, corresponding to magmatic (early-stage) and hydrothermal (late-stage) Nb-Ta mineralization ages, respectively. The cassiterite gives a weighted mean U-Pb mineralization age of 130.5 ± 3.9 Ma, which is interpreted as the magmatic-hydrothermal age (transitional stage). Zircon grains in OBP give a lower weighted mean U-Pb age of 121.5 ± 0.8 Ma, resulting from metamictization by the later fluid-assisted alteration and recrystallization in the late-stage hydrothermal event. Monazite grains from OFP yielded a weighted mean 206Pb/238U age of 137.1 ± 0.5 Ma, while zircon gives a mean U-Pb age of 130.3 ± 0.6 Ma. The ages of 137 and 130 Ma obtained for the OFP represent the magmatic (early-stage) and magmatic-hydrothermal stage (transitional) of OFP crystallization in the LYSC. Calculated zircon εHf (t) values and TDM2 ages from OFP (−7.6 to −5.4 and 1663−1532 Ma, respectively) and OBP (−8.7 to −8.2 and 1735−1704 Ma, respectively) are akin to those of the schist and metasandstone strata of the metasedimentary Lengjiaxi metasedimentary group—a melt source material to the LYSC composite batholith. We propose a long-lived ∼15 m.y. Nb-Ta-(Sn) mineralization model for the Lianyunshan complex.","PeriodicalId":242264,"journal":{"name":"GSA Bulletin","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131515421","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Climate and anthropogenic impacts on North American erosion and sediment transport since the Last Glacial Maximum: Evidence from the detrital zircon record of the Lower Mississippi Valley, USA","authors":"Nikki Neubeck, A. Carter, T. Rittenour, P. Clift","doi":"10.1130/b36565.1","DOIUrl":"https://doi.org/10.1130/b36565.1","url":null,"abstract":"The Mississippi River provides an opportunity to examine models of sediment transport in large alluviated floodplain systems. We test the idea that sources of sandy sediment in such settings are invariable on timescales <104 y because of storage and recycling in the floodplains. To reconstruct the development of the Mississippi sediment load over the past 2500 years we collected sediment from an abandoned point bar complex nearby at False River, Louisiana, USA. We also took annual samples from the lower reaches between 2015 and 2021 to assess changes on that timescale. Optically stimulated luminescence dating indicated that the point bar accreted between 2460 and 860 years ago. Detrital zircon U-Pb dating was used to assess sediment source and variability over time. We confirm a dominant sediment flux from the Rocky Mountain foreland but with higher relative erosion from the Superior Province during the Last Glacial Maximum (LGM) based on existing data from the Gulf of Mexico. There have been resolvable changes in the sources of sediment particularly since the LGM and after 860 years ago, but also over shorter, even sub-annual timescales in the recent past. These changes may reflect seasonal weather or storm events in the headwater regions and imply limited floodplain buffering of the sand load. In recent times this may reflect the installation of levees in the lower reaches, suppressing reworking. Changes over 102−103 y time periods may be related to changes in climate (e.g., the Medieval and Roman warm periods) and to the development of agriculture across North America after ∼2000 years ago. Detrital zircon dating is an effective provenance tool and does not appear to be strongly biased by the grain size of the sediment in this setting.","PeriodicalId":242264,"journal":{"name":"GSA Bulletin","volume":"37 1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123634575","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}