One of the goals of sequence stratigraphy is to model the conditions that generate stratigraphic architecture at outcrop to basin scales. Accommodation and sedimentation are the principal variables included in sequence-stratigraphic models that describe facies architecture in marine successions. Similar models exist to describe wholly nonmarine architecture. Distinct models are commonly applied to basins containing predominantly lacustrine or predominantly fluvial facies, which can make it difficult to apply models to the entire history of a basin that may include both lacustrine-dominated or fluvial-dominated phases, depending on climatic and tectonic conditions. To account for these changing conditions over the history of nonmarine basins, we present a conceptual three-dimensional model that describes the potential architectural patterns under specific combinations of accommodation, sediment flux, and water balance. Sectors of the model delineate where basins are underfilled or overfilled with respect to accommodation and limited with respect to sediment and water, creating eight zones with different implications for the development of facies architecture. Different types of basins (e.g., foreland, extensional, pull-apart, intracratonic) show broadly different trends in architecture through time. Subtle changes in accommodation, sedimentation, and water balance in the model correspond to shifts in facies architecture between lithostratigraphic units, but architectural transitions within individual basins are more important indicators of evolving basin conditions than comparisons among all basins. This model may serve as a guide for comparing the influence of distinct drivers of architecture among different types of basins as well as identifying important intervals of change during the history of basin filling. The availability of commensurate data on the history of accommodation, sedimentation, and water balance is, however, an ongoing challenge to reconstructing complete basin histories. Future analyses will test how well predicted facies stacking patterns compare to observed nonmarine stratigraphic successions resulting from the combination of accommodation, sediment flux, and water balance during the history of basin filling.
{"title":"The eight architectural zones of nonmarine basins","authors":"Katharine M. Loughney, Steven M. Holland","doi":"10.1130/ges02566.1","DOIUrl":"https://doi.org/10.1130/ges02566.1","url":null,"abstract":"One of the goals of sequence stratigraphy is to model the conditions that generate stratigraphic architecture at outcrop to basin scales. Accommodation and sedimentation are the principal variables included in sequence-stratigraphic models that describe facies architecture in marine successions. Similar models exist to describe wholly nonmarine architecture. Distinct models are commonly applied to basins containing predominantly lacustrine or predominantly fluvial facies, which can make it difficult to apply models to the entire history of a basin that may include both lacustrine-dominated or fluvial-dominated phases, depending on climatic and tectonic conditions. To account for these changing conditions over the history of nonmarine basins, we present a conceptual three-dimensional model that describes the potential architectural patterns under specific combinations of accommodation, sediment flux, and water balance. Sectors of the model delineate where basins are underfilled or overfilled with respect to accommodation and limited with respect to sediment and water, creating eight zones with different implications for the development of facies architecture. Different types of basins (e.g., foreland, extensional, pull-apart, intracratonic) show broadly different trends in architecture through time. Subtle changes in accommodation, sedimentation, and water balance in the model correspond to shifts in facies architecture between lithostratigraphic units, but architectural transitions within individual basins are more important indicators of evolving basin conditions than comparisons among all basins. This model may serve as a guide for comparing the influence of distinct drivers of architecture among different types of basins as well as identifying important intervals of change during the history of basin filling. The availability of commensurate data on the history of accommodation, sedimentation, and water balance is, however, an ongoing challenge to reconstructing complete basin histories. Future analyses will test how well predicted facies stacking patterns compare to observed nonmarine stratigraphic successions resulting from the combination of accommodation, sediment flux, and water balance during the history of basin filling.","PeriodicalId":55100,"journal":{"name":"Geosphere","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136357777","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Bryce A. Neal, Andrew K. Laskowski, Jeffrey D. Lonn, William B. Burrell
The Eocene Anaconda metamorphic core complex is the most recently documented metamorphic core complex in the North American Cordillera. While much work has focused on constraining the nature and timing of core complex extension, earlier deformation preserved in its footwall is not as well understood. The Anaconda metamorphic core complex footwall contains an anomalously thin, lower- to uppermost-amphibolite-facies section of Mesoproterozoic Belt Supergroup and Paleozoic metasedimentary strata. While the tectonic nature of this thinning is generally accepted, the mechanisms behind it remain enigmatic. Previous workers have hypothesized that footwall strata were attenuated along the upper limb of the Late Cretaceous Fishtrap recumbent anticline, a kilometer-scale, NW-vergent, recumbent fold exposed throughout the west-central metamorphic core complex footwall. New geologic mapping in the west-central Anaconda Range better constrains the nature and timing of tectonic attenuation in this structurally complex area. Two generations of folds were recognized: (1) F1 recumbent isoclines associated with the Fishtrap recumbent anticline and (2) F2 W-vergent asymmetric folds associated with map-scale N-plunging folds. F1 folds, axial planar S1 transposition fabrics, and bedding-parallel faults and shear zones boudinage, transpose, and omit strata of the Belt Supergroup. We suggest that the Fishtrap recumbent anticline tectonically attenuated the Belt Supergroup through Paleozoic section of the west-central Anaconda metamorphic core complex footwall, and we propose that it is a kilometer-scale, regionally significant structure. We further propose that the fold may have developed in response to rotational shear and sinistral transpression along the Lewis and Clark Line, which was further driven by accretion of outboard terranes along the western margin of North America during Late Cretaceous time.
{"title":"Kilometer-scale recumbent folding, tectonic attenuation, and rotational shear in the western Anaconda Range, southwestern Montana, USA","authors":"Bryce A. Neal, Andrew K. Laskowski, Jeffrey D. Lonn, William B. Burrell","doi":"10.1130/ges02595.1","DOIUrl":"https://doi.org/10.1130/ges02595.1","url":null,"abstract":"The Eocene Anaconda metamorphic core complex is the most recently documented metamorphic core complex in the North American Cordillera. While much work has focused on constraining the nature and timing of core complex extension, earlier deformation preserved in its footwall is not as well understood. The Anaconda metamorphic core complex footwall contains an anomalously thin, lower- to uppermost-amphibolite-facies section of Mesoproterozoic Belt Supergroup and Paleozoic metasedimentary strata. While the tectonic nature of this thinning is generally accepted, the mechanisms behind it remain enigmatic. Previous workers have hypothesized that footwall strata were attenuated along the upper limb of the Late Cretaceous Fishtrap recumbent anticline, a kilometer-scale, NW-vergent, recumbent fold exposed throughout the west-central metamorphic core complex footwall. New geologic mapping in the west-central Anaconda Range better constrains the nature and timing of tectonic attenuation in this structurally complex area. Two generations of folds were recognized: (1) F1 recumbent isoclines associated with the Fishtrap recumbent anticline and (2) F2 W-vergent asymmetric folds associated with map-scale N-plunging folds. F1 folds, axial planar S1 transposition fabrics, and bedding-parallel faults and shear zones boudinage, transpose, and omit strata of the Belt Supergroup. We suggest that the Fishtrap recumbent anticline tectonically attenuated the Belt Supergroup through Paleozoic section of the west-central Anaconda metamorphic core complex footwall, and we propose that it is a kilometer-scale, regionally significant structure. We further propose that the fold may have developed in response to rotational shear and sinistral transpression along the Lewis and Clark Line, which was further driven by accretion of outboard terranes along the western margin of North America during Late Cretaceous time.","PeriodicalId":55100,"journal":{"name":"Geosphere","volume":"90 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136358877","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Psychological science can be used to inform climate science graph design, resulting in more meaningful and useful graphs for communication, especially with non-scientists. In this study, we redesigned graphs from the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5) and compared participant attention and perceptions between original and novel designs with pre-/post-surveys, eye-tracking, graph usability and ranking activities, and interviews. Participants were selected for lower content knowledge and risk perception of climate from a sample of undergraduate students in the southeastern U.S. Here, we demonstrate our robust graph redesign process and the associated impacts on participants’ perceptions of graph usability, graph and scientist credibility, and risk associated with climate change. These findings indicate that interacting with climate change graphs may impact perceptions that are relevant to individuals’ motivation to take action to address climate change across political audiences, and possibly even more so among self-identified Conservatives. Additionally, participants who viewed graphs designed to align with research-informed best practices had greater increases in perceptions of climate scientist credibility and climate change risk, though these contrasts were not statistically significant (p > 0.05). Participants rated redesigned graphs as being more trustworthy, which is critical to successful climate change communication, and our qualitative results provide a possible explanation and initial points of exploration for future research.
{"title":"Seeing is believing: Climate change graph design and user judgments of credibility, usability, and risk","authors":"Steph L. Courtney, Karen S. McNeal","doi":"10.1130/ges02517.1","DOIUrl":"https://doi.org/10.1130/ges02517.1","url":null,"abstract":"Psychological science can be used to inform climate science graph design, resulting in more meaningful and useful graphs for communication, especially with non-scientists. In this study, we redesigned graphs from the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5) and compared participant attention and perceptions between original and novel designs with pre-/post-surveys, eye-tracking, graph usability and ranking activities, and interviews. Participants were selected for lower content knowledge and risk perception of climate from a sample of undergraduate students in the southeastern U.S. Here, we demonstrate our robust graph redesign process and the associated impacts on participants’ perceptions of graph usability, graph and scientist credibility, and risk associated with climate change. These findings indicate that interacting with climate change graphs may impact perceptions that are relevant to individuals’ motivation to take action to address climate change across political audiences, and possibly even more so among self-identified Conservatives. Additionally, participants who viewed graphs designed to align with research-informed best practices had greater increases in perceptions of climate scientist credibility and climate change risk, though these contrasts were not statistically significant (p > 0.05). Participants rated redesigned graphs as being more trustworthy, which is critical to successful climate change communication, and our qualitative results provide a possible explanation and initial points of exploration for future research.","PeriodicalId":55100,"journal":{"name":"Geosphere","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135150384","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
P. Betlem, N. Rodés, T. Birchall, Anders Dahlin, A. Smyrak‐Sikora, Kim Senger
Digital outcrop models (DOMs) have revolutionized the way twenty-first century geoscientists work. DOMs are georeferenced three-dimensional (3-D) digital representations of outcrops that facilitate quantitative work on outcrops at various scales. Outcrop digitalization has been traditionally conducted using laser scanners, but in the past decade, it has seen an exponential growth because of efficient and consumer-friendly structure-from-motion (SfM) algorithms concurrent with the rapid development of cost-effective aerial drones with high-resolution onboard cameras. While DOMs are routinely used in geoscientific research, education, and industry, enhanced DOM usage is restricted because raw data (e.g., photographs) and metadata are often incomplete and/or unavailable. In this contribution, we present the Svalbox Digital Model Database (Svalbox DMDb), a database of metadata and openly available data packages for individual DOMs. The Svalbox DMDb is a regional DOM database geographically constrained to the Norwegian High Arctic archipelago of Svalbard at 74°N–81°N and 10°E–35°E. Svalbard offers exceptional-quality, vegetation-free outcrops with a wide range of lithologies and tectono-magmatic styles, including extension, compression, and magmatism. Data and metadata of the systematically digitalized outcrops across Svalbard are shared according to FAIR principles through the Svalbox DMDb. Fully open-access and downloadable DOMs include not just the DOMs themselves, but also the input data, processing reports and projects, and other data products such as footprints and orthomosaics. Rich metadata for each DOM include both the technical and geological parameters (metadata), enabling visualization and integration with regional geoscientific data available through the Norwegian Polar Institute and the Svalbox online portal. The current release of Svalbox DMDb, documented in this contribution, covers 135 DOMs cumulatively covering 114 km2 of Proterozoic to Cenozoic stratigraphy.
{"title":"Svalbox Digital Model Database: A geoscientific window into the High Arctic","authors":"P. Betlem, N. Rodés, T. Birchall, Anders Dahlin, A. Smyrak‐Sikora, Kim Senger","doi":"10.1130/ges02606.1","DOIUrl":"https://doi.org/10.1130/ges02606.1","url":null,"abstract":"Digital outcrop models (DOMs) have revolutionized the way twenty-first century geoscientists work. DOMs are georeferenced three-dimensional (3-D) digital representations of outcrops that facilitate quantitative work on outcrops at various scales. Outcrop digitalization has been traditionally conducted using laser scanners, but in the past decade, it has seen an exponential growth because of efficient and consumer-friendly structure-from-motion (SfM) algorithms concurrent with the rapid development of cost-effective aerial drones with high-resolution onboard cameras. While DOMs are routinely used in geoscientific research, education, and industry, enhanced DOM usage is restricted because raw data (e.g., photographs) and metadata are often incomplete and/or unavailable. In this contribution, we present the Svalbox Digital Model Database (Svalbox DMDb), a database of metadata and openly available data packages for individual DOMs. The Svalbox DMDb is a regional DOM database geographically constrained to the Norwegian High Arctic archipelago of Svalbard at 74°N–81°N and 10°E–35°E. Svalbard offers exceptional-quality, vegetation-free outcrops with a wide range of lithologies and tectono-magmatic styles, including extension, compression, and magmatism. Data and metadata of the systematically digitalized outcrops across Svalbard are shared according to FAIR principles through the Svalbox DMDb. Fully open-access and downloadable DOMs include not just the DOMs themselves, but also the input data, processing reports and projects, and other data products such as footprints and orthomosaics. Rich metadata for each DOM include both the technical and geological parameters (metadata), enabling visualization and integration with regional geoscientific data available through the Norwegian Polar Institute and the Svalbox online portal. The current release of Svalbox DMDb, documented in this contribution, covers 135 DOMs cumulatively covering 114 km2 of Proterozoic to Cenozoic stratigraphy.","PeriodicalId":55100,"journal":{"name":"Geosphere","volume":" ","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41975481","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Michael J. Vadman, Max M. Garvue, James A. Spotila, Sean P. Bemis, D. Sarah Stamps, Lewis A. Owen, Paula M. Figueiredo
Geomorphic mapping and paleoseismologic data reveal evidence for a late Holocene multifault surface rupture along the Calico-Hidalgo fault system of the southern Eastern California Shear Zone (ECSZ). We have identified ~18 km of continuous surface rupture along the combined Calico and Hidalgo faults in the vicinity of Hidalgo Mountain in the southern Mojave Desert. Based on the freshness of geomorphic fault features and continuity of surface expression, we interpret this feature to reflect a simultaneous paleorupture of both faults. Displacement along the paleorupture is defined by 39 field measurements to be generally pure right-slip with a mean offset of 2.3 m. Scaling relationships for this offset amount imply that the original surface rupture length may have been ~82 km (corresponding to a M7.4 earthquake) and that much of the rupture trace was erased by subsequent erosion of sandy and unconsolidated valley alluvium. Eight luminescence ages from a paleoseismic trench across the paleorupture on the Hidalgo fault bracket the timing of the most recent rupture to 0.9–1.7 ka and a possible penultimate event at 5.5–6.6 ka. This timing is generally consistent with the known earthquake clusters in the southern ECSZ based on previous paleoseismic investigations. The ages of these earthquakes also overlap with the age brackets of the most recent events on the Calico fault 42 km to the north and the Mesquite Lake fault 40 km to the south from earlier work. Based on these age constraints and the expected surface rupture length, we propose that the Calico fault system experienced a major, multifault rupture that spanned the entire length of the fault system between the historical Landers and Hector Mine ruptures but preceded these events by ~1–2 k.y. Coulomb stress change modeling shows that the Calico paleorupture may have delayed the occurrence of the Landers-Hector Mine cluster by placing their respective faults in stress shadows and may have also prevented a triggered event from occurring on the Calico fault following the historic events. This work implies that closely spaced ruptures in complex shear zones may repel each other and thereby stretch out the duration of major earthquake clusters. These results also suggest that complex multifault ruptures in the ECSZ may not follow simple, repeatable patterns.
{"title":"Evidence for a prehistoric multifault rupture along the southern Calico fault system, Eastern California Shear Zone, USA","authors":"Michael J. Vadman, Max M. Garvue, James A. Spotila, Sean P. Bemis, D. Sarah Stamps, Lewis A. Owen, Paula M. Figueiredo","doi":"10.1130/ges02653.1","DOIUrl":"https://doi.org/10.1130/ges02653.1","url":null,"abstract":"Geomorphic mapping and paleoseismologic data reveal evidence for a late Holocene multifault surface rupture along the Calico-Hidalgo fault system of the southern Eastern California Shear Zone (ECSZ). We have identified ~18 km of continuous surface rupture along the combined Calico and Hidalgo faults in the vicinity of Hidalgo Mountain in the southern Mojave Desert. Based on the freshness of geomorphic fault features and continuity of surface expression, we interpret this feature to reflect a simultaneous paleorupture of both faults. Displacement along the paleorupture is defined by 39 field measurements to be generally pure right-slip with a mean offset of 2.3 m. Scaling relationships for this offset amount imply that the original surface rupture length may have been ~82 km (corresponding to a M7.4 earthquake) and that much of the rupture trace was erased by subsequent erosion of sandy and unconsolidated valley alluvium. Eight luminescence ages from a paleoseismic trench across the paleorupture on the Hidalgo fault bracket the timing of the most recent rupture to 0.9–1.7 ka and a possible penultimate event at 5.5–6.6 ka. This timing is generally consistent with the known earthquake clusters in the southern ECSZ based on previous paleoseismic investigations. The ages of these earthquakes also overlap with the age brackets of the most recent events on the Calico fault 42 km to the north and the Mesquite Lake fault 40 km to the south from earlier work. Based on these age constraints and the expected surface rupture length, we propose that the Calico fault system experienced a major, multifault rupture that spanned the entire length of the fault system between the historical Landers and Hector Mine ruptures but preceded these events by ~1–2 k.y. Coulomb stress change modeling shows that the Calico paleorupture may have delayed the occurrence of the Landers-Hector Mine cluster by placing their respective faults in stress shadows and may have also prevented a triggered event from occurring on the Calico fault following the historic events. This work implies that closely spaced ruptures in complex shear zones may repel each other and thereby stretch out the duration of major earthquake clusters. These results also suggest that complex multifault ruptures in the ECSZ may not follow simple, repeatable patterns.","PeriodicalId":55100,"journal":{"name":"Geosphere","volume":"47 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136298219","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Chao Wang, L. Ding, Houqi Wang, F. Cai, Xiaodong Wang, Liyun Zhang, Y. Yue
The Indian passive margin has preserved several pulses of magmatism during and after the disassembly of Gondwana since the late Paleozoic, providing valuable insights into the long-term magmatic evolution of various passive margins, including the Indian passive margin. In the Yumai Complex, eastern Tethyan Himalaya, a pulse of Late Triassic alkaline volcanism (ca. 227–216 Ma) is evident. The Late Triassic volcanic rocks are mildly alkaline to tholeiitic basalts with minor ultrabasic rocks, similar in geochemistry to within-plate flood basalts. The TiO2 contents (1.46–3.38 wt%, mainly >2 wt%), (La/Yb)N values (4.05–7.50), εNd(t) values (+4.86 to +6.98), and results from partial-melt modeling suggest that the basalts likely originated from garnet peridotite. Elemental and Sr-Nd systematics of magmatic rocks emplaced during the Triassic indicate oceanic island basalt (OIB) components in the magma source, interpreted as enriched mantle components rather than crustal contamination products. Spatiotemporal and geochemical patterns of magmatism reveal that the bulk compositions of the basalts changed from enriched OIB-like to depleted mid-ocean-ridge basalt (MORB)–like compositions. This phenomenon likely resulted from the evolving nature of the rifting basin, changing from a nascent continental setting to a mature ocean basin. The Triassic magmatism in the Tethyan Himalaya can be attributed to remnant lithospheric instability arising from the prolonged rifting of eastern Gondwana, leading to the formation of a magmatically passive margin.
{"title":"Formation and evolution of a magmatic system in the Indian passive margin: Insights from the Triassic Yumai Complex from the eastern Tethyan Himalaya","authors":"Chao Wang, L. Ding, Houqi Wang, F. Cai, Xiaodong Wang, Liyun Zhang, Y. Yue","doi":"10.1130/ges02655.1","DOIUrl":"https://doi.org/10.1130/ges02655.1","url":null,"abstract":"The Indian passive margin has preserved several pulses of magmatism during and after the disassembly of Gondwana since the late Paleozoic, providing valuable insights into the long-term magmatic evolution of various passive margins, including the Indian passive margin. In the Yumai Complex, eastern Tethyan Himalaya, a pulse of Late Triassic alkaline volcanism (ca. 227–216 Ma) is evident. The Late Triassic volcanic rocks are mildly alkaline to tholeiitic basalts with minor ultrabasic rocks, similar in geochemistry to within-plate flood basalts. The TiO2 contents (1.46–3.38 wt%, mainly >2 wt%), (La/Yb)N values (4.05–7.50), εNd(t) values (+4.86 to +6.98), and results from partial-melt modeling suggest that the basalts likely originated from garnet peridotite. Elemental and Sr-Nd systematics of magmatic rocks emplaced during the Triassic indicate oceanic island basalt (OIB) components in the magma source, interpreted as enriched mantle components rather than crustal contamination products. Spatiotemporal and geochemical patterns of magmatism reveal that the bulk compositions of the basalts changed from enriched OIB-like to depleted mid-ocean-ridge basalt (MORB)–like compositions. This phenomenon likely resulted from the evolving nature of the rifting basin, changing from a nascent continental setting to a mature ocean basin. The Triassic magmatism in the Tethyan Himalaya can be attributed to remnant lithospheric instability arising from the prolonged rifting of eastern Gondwana, leading to the formation of a magmatically passive margin.","PeriodicalId":55100,"journal":{"name":"Geosphere","volume":"1 1","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"63751878","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An analysis of the academic hiring networks in geoscience reveals a severe imbalance that favors graduates from a small handful of institutions. In this study, social network analysis was conducted on a database consisting of every individual with a Ph.D. working in a geoscience degree-granting pro- gram in the United States (n = 6694) between 2015 and 2021. Individuals were mapped from the institution where they earned their Ph.D. to the institution where they currently work. Of the 895 geoscience degree-granting institutions included in the database, 10 alone produced nearly a quarter (24.6%) of the entire academic geoscience workforce. Network analysis also identified a small, closed network consisting of five of the top-10 institutions, which suggests that these networks hire more frequently from one another than from other institutions in the network. When academic rank was used to analyze the network for change over time, no significant shift in the hiring patterns was found. These imbalances in faculty production disadvantage scientists who are educated at programs other than the top-placing institutions and ultimately reinforces longstanding inequities in the field, such as the underrepresentation of people who are Black, Indigenous, People of Color (BIPOC), and first-generation college students in geoscience faculty. These patterns of inequity have also been shown to limit the spread of new scientific ideas throughout research communities.
{"title":"Geoscience academic hiring networks reinforce historic patterns of inequity","authors":"Robyn Mieko Dahl","doi":"10.1130/ges02661.1","DOIUrl":"https://doi.org/10.1130/ges02661.1","url":null,"abstract":"An analysis of the academic hiring networks in geoscience reveals a severe imbalance that favors graduates from a small handful of institutions. In this study, social network analysis was conducted on a database consisting of every individual with a Ph.D. working in a geoscience degree-granting pro- gram in the United States (n = 6694) between 2015 and 2021. Individuals were mapped from the institution where they earned their Ph.D. to the institution where they currently work. Of the 895 geoscience degree-granting institutions included in the database, 10 alone produced nearly a quarter (24.6%) of the entire academic geoscience workforce. Network analysis also identified a small, closed network consisting of five of the top-10 institutions, which suggests that these networks hire more frequently from one another than from other institutions in the network. When academic rank was used to analyze the network for change over time, no significant shift in the hiring patterns was found. These imbalances in faculty production disadvantage scientists who are educated at programs other than the top-placing institutions and ultimately reinforces longstanding inequities in the field, such as the underrepresentation of people who are Black, Indigenous, People of Color (BIPOC), and first-generation college students in geoscience faculty. These patterns of inequity have also been shown to limit the spread of new scientific ideas throughout research communities.","PeriodicalId":55100,"journal":{"name":"Geosphere","volume":" ","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45587297","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Balanced regional cross sections based on surface, seismic, and subsurface data show that the thin-skinned fold-and-thrust belt in the Rocky Mountain Foothills of the Kakwa area of the central Canadian Rockies consists of a lower buried thrust belt developed in Paleozoic and Triassic strata and an upper exposed faulted fold belt of Jurassic to Cretaceous strata. Changes in fold wavelength, amplitude, and geometry with stratigraphic level indicate that multiple detachments were utilized in the upper faulted fold belt. Exposed folds are chevron or box shaped. Most appear to be detachment or fault propagation folds formed by fault-to-fold displacement transfer. Geometric and kinematic relationships in the upper faulted fold belt vary from thrust faults congruently folded by underlying folds (early fault) to folds abruptly truncated by thrust faults (late fault). In contrast, folding of thrust sheets in the buried thrust belt is consistent with in-sequence deformation for all faults except one. A sequential restoration of the balanced regional cross section shows that the variable kinematic relationships observed in the upper faulted fold belt can be explained by changes in the detachment level utilized by successive faults as they climbed out of the buried thrust belt. Chevron-folded thrust faults indicate a younger fault with associated fault displacement transfer folds formed in the footwall of an older fault. These folded thrusts formed by in-sequence faulting and utilization of successively higher detachment levels. Late faults that truncate preexisting folds required out-of-sequence (hinterlandward) utilization of a higher detachment level, and they illustrate another mechanism by which critical taper is maintained in a fold-and-thrust belt.
{"title":"Structural geometry and kinematic evolution of the central Canadian Rocky Mountain Foothills fold-and-thrust belt: Complex kinematic relationships controlled by detachment utilization","authors":"M. McMechan","doi":"10.1130/ges02623.1","DOIUrl":"https://doi.org/10.1130/ges02623.1","url":null,"abstract":"Balanced regional cross sections based on surface, seismic, and subsurface data show that the thin-skinned fold-and-thrust belt in the Rocky Mountain Foothills of the Kakwa area of the central Canadian Rockies consists of a lower buried thrust belt developed in Paleozoic and Triassic strata and an upper exposed faulted fold belt of Jurassic to Cretaceous strata. Changes in fold wavelength, amplitude, and geometry with stratigraphic level indicate that multiple detachments were utilized in the upper faulted fold belt. Exposed folds are chevron or box shaped. Most appear to be detachment or fault propagation folds formed by fault-to-fold displacement transfer. Geometric and kinematic relationships in the upper faulted fold belt vary from thrust faults congruently folded by underlying folds (early fault) to folds abruptly truncated by thrust faults (late fault). In contrast, folding of thrust sheets in the buried thrust belt is consistent with in-sequence deformation for all faults except one. A sequential restoration of the balanced regional cross section shows that the variable kinematic relationships observed in the upper faulted fold belt can be explained by changes in the detachment level utilized by successive faults as they climbed out of the buried thrust belt. Chevron-folded thrust faults indicate a younger fault with associated fault displacement transfer folds formed in the footwall of an older fault. These folded thrusts formed by in-sequence faulting and utilization of successively higher detachment levels. Late faults that truncate preexisting folds required out-of-sequence (hinterlandward) utilization of a higher detachment level, and they illustrate another mechanism by which critical taper is maintained in a fold-and-thrust belt.","PeriodicalId":55100,"journal":{"name":"Geosphere","volume":" ","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43375483","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Mavor, S. Bennett, R. Crow, J. Singleton, V. Langenheim, D. Stockli, M. Stelten, Timothy Brickey, P. Umhoefer, L. Beard
The evolution of strain in nascent continental plate boundaries commonly involves distributed deformation and transitions between different styles of deformation as the plate boundary matures. Distributed NW-striking faults, many with km-scale right-lateral separation, are prevalent near Blythe, California, and have been variably interpreted to have accommodated either Middle Miocene NE-SW extension as normal faults or Late Miocene to Pliocene dextral shear as strike-slip faults. However, with poor timing and kinematic constraints, it is unclear how these faults relate to known domains of Neogene deformation and the evolution of the Pacific–North America plate boundary. We present kinematic data (n = 642 fault planes, n = 512 slickenlines) that demonstrate that these faults dominantly dip steeply northeast; ~96% of measured faults record normal, dextral, or oblique dextral-normal kinematics that likely reflect a gradational transition between normal and dextral oblique kinematic regimes. We constrain fault timing with 11.7 Ma and 7.0 Ma 40Ar/39Ar dates of rocks cut by faults, and laser ablation–inductively coupled plasma–mass spectrometry U-Pb dating of calcite mineralized during oblique dextral faulting that demonstrates fault slip at ca. 10–7 Ma and perhaps as late as ca. 4 Ma. This Late Miocene dextral oblique faulting is best compatible with a documented regional transition from Early to Middle Miocene NE-directed extension during detachment fault slip to subsequent NW-directed dextral shear. We estimate 11–38 km of cumulative dextral slip occurred across a 50-km-wide zone from the Palen to Riverside mountains, including up to 20 km of newly documented dextral shear that may partly alleviate the regional discrepancy of cumulative dextral shear along this part of the Late Miocene Pacific–North America plate boundary.
随着板块边界的成熟，新生大陆板块边界的应变演化通常包括分布变形和不同变形类型之间的转换。分布在加利福尼亚Blythe附近的北西走向的断层，许多具有千米规模的右侧分离，并且被不同地解释为适应中新世中期NE-SW伸展作为正断层或晚中新世至上新世右旋剪切作为走滑断层。然而，由于时间和运动的限制，这些断层与已知的新近纪变形域和太平洋-北美板块边界的演化之间的关系尚不清楚。我们提供的运动学数据(n = 642个断层面，n = 512条滑溜线)表明这些断层主要向东北倾斜;约96%的测量断层记录了正常、右向或斜向右向-正向运动学，这可能反映了正常和右向斜向运动学之间的渐变。我们用断层切割的岩石的11.7 Ma和7.0 Ma 40Ar/39Ar年代学来约束断层时间，并用激光烧蚀-电感耦合等离子体质谱法对斜向右断裂期间矿化的方解石进行U-Pb年代学，表明断层滑动约为10-7 Ma，可能晚至约4 Ma。晚中新世右旋斜断裂与有文献记载的从早至中中新世拆离断层滑移期间的北东向伸展到随后的北西向右旋剪切的区域过渡最为吻合。我们估计从Palen到Riverside山脉的50公里宽的区域内发生了11-38公里的累积右向滑动，其中包括新记录的高达20公里的右向剪切，这可能在一定程度上缓解了晚中新世太平洋-北美板块边界这部分地区累积右向剪切的区域差异。
{"title":"Evolution of Miocene normal and dextral faulting in the lower Colorado River region near Blythe, California, USA","authors":"S. Mavor, S. Bennett, R. Crow, J. Singleton, V. Langenheim, D. Stockli, M. Stelten, Timothy Brickey, P. Umhoefer, L. Beard","doi":"10.1130/ges02608.1","DOIUrl":"https://doi.org/10.1130/ges02608.1","url":null,"abstract":"The evolution of strain in nascent continental plate boundaries commonly involves distributed deformation and transitions between different styles of deformation as the plate boundary matures. Distributed NW-striking faults, many with km-scale right-lateral separation, are prevalent near Blythe, California, and have been variably interpreted to have accommodated either Middle Miocene NE-SW extension as normal faults or Late Miocene to Pliocene dextral shear as strike-slip faults. However, with poor timing and kinematic constraints, it is unclear how these faults relate to known domains of Neogene deformation and the evolution of the Pacific–North America plate boundary. We present kinematic data (n = 642 fault planes, n = 512 slickenlines) that demonstrate that these faults dominantly dip steeply northeast; ~96% of measured faults record normal, dextral, or oblique dextral-normal kinematics that likely reflect a gradational transition between normal and dextral oblique kinematic regimes. We constrain fault timing with 11.7 Ma and 7.0 Ma 40Ar/39Ar dates of rocks cut by faults, and laser ablation–inductively coupled plasma–mass spectrometry U-Pb dating of calcite mineralized during oblique dextral faulting that demonstrates fault slip at ca. 10–7 Ma and perhaps as late as ca. 4 Ma. This Late Miocene dextral oblique faulting is best compatible with a documented regional transition from Early to Middle Miocene NE-directed extension during detachment fault slip to subsequent NW-directed dextral shear. We estimate 11–38 km of cumulative dextral slip occurred across a 50-km-wide zone from the Palen to Riverside mountains, including up to 20 km of newly documented dextral shear that may partly alleviate the regional discrepancy of cumulative dextral shear along this part of the Late Miocene Pacific–North America plate boundary.","PeriodicalId":55100,"journal":{"name":"Geosphere","volume":" ","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42654532","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Cobbett, L. Beranek, S. Piercey, J. Crowley, M. Colpron
The breakup of the supercontinent Rodinia and development of the western Laurentian rifted margin are in part recorded by Neoproterozoic to mid-Paleozoic igneous and sedimentary rock successions in the Canadian Cordillera. New bedrock mapping and volcanic facies analysis of Early Ordovician mafic rocks assigned to the Menzie Creek Formation in central Yukon allow reconstruction of the depositional environment during the volcanic eruptions, whole-rock geochemical data constrain the melting depth and crust-mantle source regions of the igneous rocks within the study area, and zircon U-Pb age studies provide determination of the precise timing of sub- marine eruptions. Menzie Creek Formation volcanic rocks are interlayered with continental slope strata and show lithofacies consistent with those of modern seamount systems. Representative seamount facies contain several kilometers of hyaloclastite breccia and pillow basalt with rare sedimentary rocks. Menzie Creek Formation seamounts form a linear array parallel to the Twopete fault, an ancient extensional or strike-slip fault that localized magmatism along the nascent western Laurentian margin. Zircon grains from two volcanic successions yielded high-precision chemical abrasion–thermal ionization mass spectrometry (CA-TIMS) dates of ca. 484 Ma (Tremadocian), which are interpreted as the age of eruption. Menzie Creek Formation rocks are alkali basalt and have oceanic-island basalt–like geochemical compositions. The whole-rock trace element and Nd-Hf isotope compositions are consistent with the partial melting of subcontinental lithospheric mantle at ~75–100 km depth. Post-rift, Early Ordovician seamounts in central Yukon record punctuated eruptive activity along a rift-related fault, the separation of a continental fragment from western Laurentia, or the oblique post-breakup kinematics from the counterclockwise rotation of Laurentia that facilitate local extension in the passive margin.
{"title":"Early Ordovician seamounts preserved in the Canadian Cordillera: Implications for the rift history of western Laurentia","authors":"R. Cobbett, L. Beranek, S. Piercey, J. Crowley, M. Colpron","doi":"10.1130/ges02613.1","DOIUrl":"https://doi.org/10.1130/ges02613.1","url":null,"abstract":"The breakup of the supercontinent Rodinia and development of the western Laurentian rifted margin are in part recorded by Neoproterozoic to mid-Paleozoic igneous and sedimentary rock successions in the Canadian Cordillera. New bedrock mapping and volcanic facies analysis of Early Ordovician mafic rocks assigned to the Menzie Creek Formation in central Yukon allow reconstruction of the depositional environment during the volcanic eruptions, whole-rock geochemical data constrain the melting depth and crust-mantle source regions of the igneous rocks within the study area, and zircon U-Pb age studies provide determination of the precise timing of sub- marine eruptions. Menzie Creek Formation volcanic rocks are interlayered with continental slope strata and show lithofacies consistent with those of modern seamount systems. Representative seamount facies contain several kilometers of hyaloclastite breccia and pillow basalt with rare sedimentary rocks. Menzie Creek Formation seamounts form a linear array parallel to the Twopete fault, an ancient extensional or strike-slip fault that localized magmatism along the nascent western Laurentian margin. Zircon grains from two volcanic successions yielded high-precision chemical abrasion–thermal ionization mass spectrometry (CA-TIMS) dates of ca. 484 Ma (Tremadocian), which are interpreted as the age of eruption. Menzie Creek Formation rocks are alkali basalt and have oceanic-island basalt–like geochemical compositions. The whole-rock trace element and Nd-Hf isotope compositions are consistent with the partial melting of subcontinental lithospheric mantle at ~75–100 km depth. Post-rift, Early Ordovician seamounts in central Yukon record punctuated eruptive activity along a rift-related fault, the separation of a continental fragment from western Laurentia, or the oblique post-breakup kinematics from the counterclockwise rotation of Laurentia that facilitate local extension in the passive margin.","PeriodicalId":55100,"journal":{"name":"Geosphere","volume":" ","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43146999","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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