GSA Bulletin最新文献

{"title":"Provenance of eolian deposits in the Xorkol Basin: Implications for Eocene dust-transport pattern in western China","authors":"F. Pan, Jianxing Li, J. Nie, Yong Xu, L. Yue","doi":"10.1130/b36274.1","DOIUrl":"https://doi.org/10.1130/b36274.1","url":null,"abstract":"Atmospheric circulation in western China significantly affects the inland climate of Asia. Constraining the provenance of eolian sequences can provide robust evidence for dust-transport pathways, and thus the evolution of paleo-atmospheric circulation. Western China has been dominated by the westerly wind regime since the late Oligocene, as demonstrated by provenance studies of eolian deposits. However, the wind regime responsible for the accumulation of eolian deposits during the Eocene is unclear due to a lack of corresponding provenance studies. Here, we present the first provenance analysis for an Eocene (ca. 51−40 Ma) eolian Red Clay sequence in the Xishuigou Formation of the Xorkol Basin in western China, based on multiproxy geochemical and geochronological data. Comparison of zircon U−Pb ages from the Xishuigou sequence with ages from potential source regions reveals that the northern piedmont of the West Kunlun Range was a persistent source, although sediments from the nearby Altun-Xorkol region were an important dust source for the lower part of the Xishuigou sequence which were deposited between ca. 51 Ma and 46.5 Ma. These results reveal that the westerly dust-transport pattern has been dominant in western China since at least ca. 51 Ma. The similarity of provenance between the Eocene Red Clay of the Xishuigou Formation and the Neogene eolian sequence of the overlying Caihonggou Formation in the same area implies that this dust-transport pattern was stable from the Eocene to the Neogene, despite dramatic changes in paleogeography, paleotopography, and global climate.","PeriodicalId":242264,"journal":{"name":"GSA Bulletin","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114195531","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":"Porphyry copper mineralization triggered by sulfate reduction and alkali metasomatism: Constraints from an experimental investigation","authors":"Jianping Li, Weihua Liu, Long Su, Dengfeng Li, Shitao Zhang, Huayong Chen","doi":"10.1130/b36435.1","DOIUrl":"https://doi.org/10.1130/b36435.1","url":null,"abstract":"The potassium silicate (K-silicate) alteration zone is the main ore contributor in porphyry copper deposits worldwide. Knowledge of element behaviors in the alteration and mineralization processes is essential for an improved understanding of porphyry copper mineralization, but they are still not well understood. In this study, we reacted synthetic Cl-rich fluids, containing K, Na, Cu, Mo, Zn, etc., with andesite in a complex experimental system to simulate the shallow porphyry copper mineralization process. We aimed to bridge the gap between simple experimental studies and complex natural systems and to evaluate the contribution of sulfate reduction to porphyry ore formation and its relationship with early alkali metasomatism. The results show that increasing temperature (from 300 to 500 °C) enhances the K-silicate alteration by promoting ion-exchange reactions, and the K-feldspar is mainly formed by the transformation of plagioclase via a dissolution-reprecipitation processes. The low-salinity vapor phase has a stronger capacity for K-silicate alteration than the liquid phase at similar temperatures. In addition, increasing temperature from 300 to 500 °C favors sulfate reduction to further enhance metal sulfide precipitation. The limited availability of reduced sulfur in the fluid causes preferential precipitation of Cu-(Mo) sulfides, while most of the Zn is soluble in the fluid, and Cu precipitation as sulfides in the vapor is much more efficient than in the coexisting liquid. The overlap between the K-silicate alteration zone and the mineralization triggered by sulfate reduction in porphyry copper deposits is controlled by several concomitant factors, e.g., relatively high temperature (e.g., at 400−500 °C), vapor formation, and decompression. Moreover, K-silicate alteration would further promote mineralization by changing fluid compositions, e.g., removing K from the fluid.","PeriodicalId":242264,"journal":{"name":"GSA Bulletin","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131106140","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":"A possible sea-level fall trigger for the youngest rejuvenated volcanism in Hawaiʻi","authors":"B. Jicha, Michael O. Garcia, C. Lormand","doi":"10.1130/b36615.1","DOIUrl":"https://doi.org/10.1130/b36615.1","url":null,"abstract":"Many intraplate oceanic islands undergo “rejuvenated” volcanism following the main edifice-building stage. Honolulu features Hawaiʻi’s most recent rejuvenated volcanism. K-Ar dating of Honolulu volcanism suggests that it started at ca. 750 ka and ended at <100 ka. Here, we present new 40Ar/39Ar ages and olivine diffusion modeling from Koko Rift lavas to resolve when the most recent Honolulu eruptions occurred and to evaluate possible mechanisms of rejuvenated volcanism and volcanic hazards. Diffusion modeling of olivine zoning profiles in Koko Rift basalts suggests that magmas were stored in the crust for many months prior to eruption. Six new 40Ar/39Ar ages cluster at 67 ± 2 ka (2σ), which demonstrates that Koko Rift is Hawaiʻi’s youngest known area of rejuvenated volcanism. The timing of Koko Rift eruptions coincides with the pronounced drop in global sea level (∼100 m) during Marine Isotope Stage 4. This major sea-level fall may have triggered the eruptions of Koko Rift magmas that were stored in the crust for months to years at < 15 km depth. The proposed mechanism is similar to that at other volcanic islands, which suggests that changes in global sea level may have significant control on the magnitude and frequency of eruptions at ocean island volcanoes.","PeriodicalId":242264,"journal":{"name":"GSA Bulletin","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126847917","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":"Origin of Late Cretaceous, enclave-bearing granitoids in southern Tibet: Implications for magma recharge and crustal thickening","authors":"Ding-Jun Wen, Xiumian Hu, Jinbiao Yu, Xiaolei Wang, T. Chapman, Rui-Qiang Wang","doi":"10.1130/b36530.1","DOIUrl":"https://doi.org/10.1130/b36530.1","url":null,"abstract":"Exposures of enclave-bearing granitoids can provide rare opportunities to directly evaluate the connection between compositional variability and the depth of origin of arc magmatic rocks. The ∼1000 km long Gangdese batholith is a composite batholith with composition from mafic to felsic; SiO2 ranges from 51 wt% to 70 wt%. New zircon U−Pb dating of the Nyemo plutons, Renbu plutons, and Xigaze plutons in the Gangdese batholith is consistent with their emplacement and crystallization in the Late Cretaceous (ca. 90−85 Ma). Mafic magmatic enclaves (MMEs) in the plutons are characterized by low SiO2 (50.9−56.0 wt%) and Nb/U, Ce/Pb, and Nb/La ratios coupled with enrichment in light rare earth elements and large ion lithophile elements and depletion in high field strength elements. These geochemical features, combined with depleted whole-rock εNd(t) (+4.2 to +4.7) and zircon εHf(t) (+9.0 to +13.8), suggest that they were derived by partial melting of a depleted mantle source associated with subduction-related fluids. The granitoids with high SiO2 (55.6−66.9 wt%) display adakitic geochemical characteristics, such as low Y and Yb contents, and high Sr/Y and La/Yb ratios. Their positive whole-rock εNd(t) (+4.0 to +5.5) and zircon εHf(t) (+6.9 to +14.3) values, as well as enrichment of incompatible elements, indicate that the granitoids were derived from partial melting of the juvenile lower crust. Geochemical modeling suggests that the compositional diversities of MMEs and adakitic granitoids were inherited from heterogeneous sources. This genetic relationship indicates that the underplated basaltic magmas could have supplied sufficient heat to trigger the melting of the thickened crust and thus formation of the enclave-bearing granitoid. In this regard, the origin of arc rocks can mirror the evolution of crustal thickness. Our results reveal that the crust was thickened to ∼50 km during the Late Cretaceous (90−85 Ma) and provide a magmatic record of crustal thickening prior to the Cenozoic Indo-Asia collision.","PeriodicalId":242264,"journal":{"name":"GSA Bulletin","volume":"52 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127445058","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":"Late Holocene volcanic stratigraphy and eruption chronology of the dacitic Young Doña Juana volcano, Colombia","authors":"N. Pardo, R. Sulpizio, F. Lucchi, G. Giordano, S. Cronin, B. Pulgarín, M. Roverato, Ana María Correa-Tamayo, R. Camacho, M. Cabrera","doi":"10.1130/b36557.1","DOIUrl":"https://doi.org/10.1130/b36557.1","url":null,"abstract":"We present the late Holocene eruption history of the poorly known Doña Juana volcanic complex, in SW Colombia, which last erupted in the twentieth century. This represents a case study for potentially active volcanism in the rural Northern Andes, where tropical climate conditions and a fragmented social memory blur the record of dormant volcanoes. We reconstructed the volcanic stratigraphy of the central-summit vent area by integrating new mapping at 1:5000 scale with radiocarbon ages, sedimentology analysis, and historical chronicles. Our results revealed cyclic transitions from lava-dome growth phases and collapse to explosive Vulcanian and possibly subplinian phases. Pyroclastic density currents were generated by dome collapse producing block-and-ash flows or by pyroclastic fountain/column collapse and were rapidly channelized into the deeply incised fluvial valleys around the volcano summit. The pyroclastic density currents were ∼4−10 × 106 m3 in volume and deposited under granular flow− or fluid escape−dominated depositional regimes at high clast concentrations. In places, more dilute upper portions reached a wider areal distribution that affected the inhabited areas on high depositional terraces. The coefficient of friction (ΔH/L) is higher for block-and-ash flows and dense lava−bearing fountain/low-column-collapse pyroclastic density currents compared to pumice-bearing, column-collapse pyroclastic density currents. Associated mass-wasting processes included syneruptive and intereruptive debris flows, with the last one documented in 1936 CE.","PeriodicalId":242264,"journal":{"name":"GSA Bulletin","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114802795","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":"Geology of the Liuyuan Complex, NW China: A Permian back-arc basin ophiolite at the southern edge of the Central Asian orogenic belt","authors":"G. Santos, J. Bédard, C. V. van Staal, Shoufa Lin, Tong Hong, Kai Wang","doi":"10.1130/b36736.1","DOIUrl":"https://doi.org/10.1130/b36736.1","url":null,"abstract":"Located in the southern margin of the Central Asian orogenic belt, the stratigraphy and tectonic setting of the mafic 290−280 Ma Liuyuan Complex have been controversial for decades, with workers arguing for a forearc ophiolite or a continental rift setting. Here, we present the results of a detailed field study, where the Liuyuan Complex was subdivided into troctolite, melatroctolite, layered gabbro, varitextured olivine gabbro, hornblende gabbro, plagiogranite, sheeted dike, and mafic tectonite, in addition to previously identified and studied basalt and chert. All contacts between the igneous facies are intrusive, with gabbroic rocks separated from the overlying basalt by a well-developed and laterally continuous sheeted dike complex. Based on their geochemical affinities, two groups of basalt were identified: group I (low-TiO2) and group II (high-TiO2). A modeled liquid line of descent, assuming perfect mineral fractionation, with a liquidus temperature of 1212 °C, pressure of 1 kbar, fO2 at the quartz-fayalite-magnetite (QFM) buffer, and initial melt H2O of 0.5 wt%, provides an excellent fit to group I lavas, with group II basalts interpreted as having formed from a distinct arc source. The stratigraphy, extended trace-element patterns, and tectonic fingerprinting of the lavas suggest the Liuyuan Complex formed as an ophiolite in a fast-spreading back-arc basin, a setting inconsistent with previously proposed tectonic models for the southern Central Asian orogenic belt. We expand on a tectonic model that proposes the Liuyuan Complex formed as a back-arc to the recently identified Ganquan arc. The back-arc basin was then consumed in a north-dipping subduction zone beneath the active margin of composite Siberia. The magmatic center of this arc migrated southward, likely caused by slab roll-back, with the Liuyuan Complex becoming the basement of an arc. Exhumation of the Liuyuan Complex took place by 267 Ma, as constrained by the age of a subaerial dacite that unconformably overlies the basalts of the Liuyuan Complex.","PeriodicalId":242264,"journal":{"name":"GSA Bulletin","volume":"145 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116366847","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":"INFLUENCE OF LAKE BASIN MORPHOLOGY ON CLIMATE-SEDIMENT TRANSFER FUNCTIONS: EARLY EOCENE WILKINS PEAK MEMBER, GREEN RIVER FORMATION, WYOMING","authors":"Andrew P Walters, A. Carroll, S. Meyers, T. Lowenstein, M. Smith","doi":"10.1130/abs/2020am-357012","DOIUrl":"https://doi.org/10.1130/abs/2020am-357012","url":null,"abstract":"Lacustrine strata are often among the highest-resolution terrestrial paleoclimate archives available. The manner in which climate signals are registered into lacustrine deposits varies, however, as a function of complex sedimentologic and diagenetic processes. The retrieval of reliable records of climatic forcing therefore requires a means of evaluating the potential influence of changing sedimentary transfer functions. Here, we use high-resolution X-ray fluorescence core scanning of the Wilkins Peak Member of the Green River Formation to characterize the long-term evolution of transfer functions in an ancient lacustrine record.\u0000 Our analysis identifies a shift in the frequency distribution of Milankovitch-band variance between the lower and middle Wilkins Peak Member across a range of temporally calibrated elemental intensity records. Spectral analysis of the lower Wilkins Peak Member shows strong short eccentricity, obliquity, precession, and sub-Milankovitch−scale variability, while the middle Wilkins Peak Member shows strong eccentricity variability and reduced power at higher frequencies. This transition coincides with a dramatic decline in the number and volume of evaporite beds.\u0000 We attribute this shift to a change in the Wilkins Peak Member depositional transfer function caused by evolving basin morphology, which directly influenced the preservation of bedded evaporite as the paleolake developed from a deeper, meromictic lake to a shallower, holomictic lake. The loss of bedded evaporite, combined with secondary evaporite growth, results in reduced obliquity- and precession-band power and enhanced eccentricity-band power in the stratigraphic record. These results underscore the need for careful integration of basin and depositional system history with cyclostratigraphic interpretation of the dominant astronomical signals preserved in the stratigraphic archive.","PeriodicalId":242264,"journal":{"name":"GSA Bulletin","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114837653","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":"Ages of the granitic basement of Long Valley Caldera, California, USA, and siting of the Quaternary granite-rhyolite pluton","authors":"W. Hildreth, J. Fierstein, J. Vazquez","doi":"10.1130/b36589.1","DOIUrl":"https://doi.org/10.1130/b36589.1","url":null,"abstract":"The leucogranitic crystal-mush pluton beneath the iconic Long Valley Caldera, California, USA, released >820 km3 of crystal-poor Pleistocene rhyolite, which was hosted by numerous Mesozoic granitic plutons, only a few of which had been dated until now. Reported here are U-Pb zircon ages, determined by sensitive high-resolution ion microprobe−reverse geometry (SHRIMP-RG), for 11 circumcaldera granitoids, all of them either Triassic or Cretaceous. Growth of the 35-km-wide Quaternary rhyolite-leucogranite plutonic reservoir was fostered by collocation of (1) a dense swath of late Pliocene basaltic vents, (2) a left-stepping extensional reentrant in the rangefront fault zone of the Sierra Nevada batholith, and (3) a sharp offset of the Proterozoic continental margin as represented by the Sr-isotope 0.706 line. We further consider whether the basement architecture of as many as 26 separate Triassic and Cretaceous plutons and intervening septa and pendants of Paleozoic metasedimentary rocks influenced siting of the Quaternary pluton and whether the ragged margin of Proterozoic lithosphere helped to focus asthenospheric edge upwelling that intensified crustal melting and intrusion in both the Triassic and the Quaternary.","PeriodicalId":242264,"journal":{"name":"GSA Bulletin","volume":"68 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121957715","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":"Frontal expansion of an accretionary wedge under highly oblique plate convergence: Southern Indo-Burman Ranges, Myanmar","authors":"Peng Zhang, Shaoyong Jiang, R. Donelick, Renyuan Li, C. Soares, L. Mei","doi":"10.1130/b36560.1","DOIUrl":"https://doi.org/10.1130/b36560.1","url":null,"abstract":"The formation of accretionary wedges with oversteepened slopes and uplifted axial zones has been demonstrated to be potentially associated with highly oblique plate convergence by numerical and analog studies. The direct role of this mechanism, or other factor(s) in producing the described structural and morphological features in nature, however, has yet to be confirmed. We used seismic reflection sections, detrital zircon U-Pb ages, and detrital apatite fission-track thermochronological data to examine the effects of highly oblique convergence and sediment reworking on accretionary wedge growth in the Indo-Burma Subduction Zone. A detailed subsurface structural analysis of a two-dimensional seismic survey from the outer wedge of the southern Indo-Burman Ranges, Myanmar, yielded three primary characteristics. These are (1) a narrow, steep deformation front (average width 15.6 km) and a vast, low-relief shelf terrace (average width 49 km); (2) a comparatively long-lived growth thrust fault (FT1) with a convex-up geometry at the rear of the deformation front that controlled the vertical stack of the progradational sequences in the shelf terrace; and (3) a group of NE-striking transtensional faults that cut through entire outer-wedge successions and displays as a series of negative flower-like structures. These characteristic features are roughly consistent with the results of laboratory analog modeling of highly oblique plate convergence but significantly differ from those of natural accretionary wedges that formed under highly oblique convergence conditions, such as those in the Sumatra, Hikurangi, Chile, and Cascadia. We further analyzed the sediment provenance of the southern Indo-Burman Ranges and discovered that the outer-wedge rocks are a product of sediment reworking of the hinterland wedge that began to be uplifted and exhumed in the early Miocene (22−12 Ma) due to transpressional motion between the Indian plate and West Burma Terrane. Our analyses indicate that active sedimentation behind the major growth thrust fault (FT1) provided additional basal shear stress that strengthened the coupling of the interface between the wedge base and décollement and promoted the vertical expansion of the outer wedge of the southern Indo-Burman Ranges from the Neogene to the present day. In contrast, the outer wedge of the central Indo-Burman Ranges has experienced stronger forward accretion since the late Miocene, which could be explained by a smaller degree of obliquity and weaker sediment reworking. Our findings demonstrate that both highly oblique plate convergence and sediment reworking were the primary driving forces that triggered vertical development of accretionary wedges. The results of this research have significant implications for understanding the structures and kinematic evolution of wedge systems at other convergent plate margins, in which seamount passage or subduction erosion is often interpreted as the cause of the steeply tapered wedge","PeriodicalId":242264,"journal":{"name":"GSA Bulletin","volume":"62 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131637107","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":"Reconstructing backwater hydrodynamics from fluvial-deltaic deposits using stratigraphic inversion: An example from the Tullig Sandstone, Western Irish Namurian Basin, County Clare, Ireland","authors":"Chenliang Wu, J. Nittrouer, E. Barefoot, Kurtis C. Burmeister","doi":"10.1130/b36475.1","DOIUrl":"https://doi.org/10.1130/b36475.1","url":null,"abstract":"Fluvial-deltaic systems are subject to non-uniform backwater flow where rivers approach receiving basins. This hydrodynamic condition results in sediment aggradation on the channel bed and enhanced downstream fining. In turn, this impacts river channel dynamics, including lateral migration rates and the propensity for avulsion. The imprint of non-uniform flow on stratigraphy has been reported from field, numerical modeling, and experimental studies. This work provides key observations for evaluating the impact of non-uniform flow spanning length scales from those of sediment grains to delta lobes. However, reconstructing paleohydraulic conditions of non-uniform flow from fluvial-deltaic settings remains a challenge. Non-uniform flow is a defining characteristic of fluvial-deltaic environments, but most existing relations linking hydrology and the depositional record rely on the assumption of steady and uniform flow. Herein, we present a novel stratigraphic inversion technique, combining it with morphodynamic modeling and statistical analyses, to evaluate how backwater conditions manifest in the stratigraphy of the Tullig Sandstone, an ancient fluvial-deltaic deposit of the Western Irish Namurian Basin. Our analyses refine estimates of channel properties, including flow depth and bed slope, and are validated by field measurements of sandstone-facies properties, including grain size and stratal architecture. For example, bed sediment fines down-dip, commensurate with increasing cross set and bed thicknesses. These patterns indicate bed aggradation and are consistent with reconstructed morphodynamic conditions. This study pinpoints the extent of non-uniform flow and its influence on fluvial-deltaic stratigraphy and provides a framework for improving reconstruction techniques used to interpret the paleohydrology of ancient fluvial-deltaic systems.","PeriodicalId":242264,"journal":{"name":"GSA Bulletin","volume":"124 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126908193","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}