Journal of the Geological Society最新文献

{"title":"Structural styles of the Tierra del Fuego fold-thrust belt foothills, Argentina","authors":"F. Fuentes","doi":"10.1144/jgs2022-182","DOIUrl":"https://doi.org/10.1144/jgs2022-182","url":null,"abstract":"Regional structural cross-sections based on seismic, borehole and surface data portray the foothills geometry of the Tierra del Fuego fold-thrust belt. Andean contraction was accommodated by two main deformation mechanisms: 1) A lower duplex thrust system that involves mainly Cretaceous deposits, with floor and roof thrusts at the base of the Cretaceous and close to the base of the Cenozoic, respectively; and 2) A series of detachment and faulted detachment anticlines in the Cenozoic, detached in mudstones above the roof thrust of the underlying duplex thrust system. Less common structures include fault bend and fault propagation folds. Basement fault reactivation is only locally important, with most Jurassic grabens and half-grabens preserved without inversion. Shortening along the foothills is modest, with values ranging from ∼8 to 4.6 kilometers. This region of the fold-thrust belt has hydrocarbon exploration interest; however, it is largely underexplored. Several large anticlines preserving Cenozoic clastic rocks have not been tested to date. The key risk for these structures is the charge, as the thick mudstone package forming their detachment isolates potential Cenozoic reservoirs from the Lower Cretaceous source rocks. Duplex thrust systems at depth may constitute a potential exploration play, provided brittle intervals were naturally fractured.","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47844137","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}

{"title":"Biostratigraphy versus geophysics; correlation of Middle Turonian chalks in the Anglo-Paris Basin","authors":"Andy Gale","doi":"10.1144/jgs2023-010","DOIUrl":"https://doi.org/10.1144/jgs2023-010","url":null,"abstract":"High resolution correlations between boreholes are commonly based on a combination of geophysical well log data and biostratigraphy and, when these conflict, resolution can be contentious and difficult. Such a situation exists in the Middle Turonian chalks of the Anglo-Paris Basin, where electrical resistivity logs, registering thin but seemingly laterally continuous beds of clay-rich chalk (marls) in mostly uncored boreholes, provide apparently straightforward correlations across broad regions. In contrast, detailed biostratigraphical analysis using microcrinoids provides very different results, showing the presence of a major hiatus associated with a hardground and differing significantly from the geophysical correlations. Detailed re-examination of this contentious problem, utilising exposures adjacent to boreholes, demonstrates the supremacy of detailed biostratigraphical analysis, independently supported by regional thickness patterns, cyclostratigraphy and geochemistry. Although closely spaced geophysical well logs can afford convincing correlations, their use in correlation over broader geographical regions leads to erroneous and misleading conclusions.","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46235439","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}

{"title":"Stratigraphic and geographic distribution of dinosaur tracks in the UK","authors":"K. Edgar, Lewis Haller, Daniel D. Cashmore, E. Dunne, R. Butler","doi":"10.1144/jgs2023-003","DOIUrl":"https://doi.org/10.1144/jgs2023-003","url":null,"abstract":"Dinosaur tracks are a key means of determining the palaeoecology and distribution of dinosaurs through time. They provide a highly complementary information source to the body (skeletal) fossil record but differ in preserving direct evidence of animals’ interactions with their environment. The UK has a rich history of ∼200 yrs of dinosaur track discovery but no recent synthesis exists. Here, we present a new dataset of dinosaur tracks in the UK. This dataset shows a close correlation between the distribution of terrestrial sediments and the preservation of dinosaur tracks through the Mesozoic, providing discrete snapshots into dinosaur communities in the Upper Triassic, Middle Jurassic and Lower Cretaceous. The dinosaur track record shows similar broad patterns of diversity and relative abundance of the major dinosaur groups (Theropoda, Sauropodomorpha, Ornithopoda, and Thyreophora) through time to the body fossil record, although differs in that body fossils are found (albeit infrequently) in marine sediments. There is a broad trend towards higher numbers of track occurrences through time and a notable increase in the relative abundance of ornithopod tracks following the Jurassic-Cretaceous boundary. The track record remains an underutilised resource with the potential to provide a much fuller view of Mesozoic dinosaur ecosystems.\u0000 \u0000 Supplementary material:\u0000 https://doi.org/10.6084/m9.figshare.c.6606634\u0000","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49315341","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}

{"title":"Unsupervised classification applications in enhancing lithological mapping and geological understanding – A case study from Northern Ireland","authors":"Z. Smillie, V. Demyanov, J. McKinley, M. Cooper","doi":"10.1144/jgs2022-136","DOIUrl":"https://doi.org/10.1144/jgs2022-136","url":null,"abstract":"Using pattern classification algorithms can help recognise and predict patterns in large and complex multivariate datasets. Utilising competitive learning, self-organising maps (SOMs) are known unsupervised classification tools that are considered very useful in pattern classification and recognition. This technique is based on the principles of vector quantification of similarities and clustering in a high-dimensional space, where the method can handle the analysis and visualization of high-dimensional data. The tool is ideal for analysing a complex combination of categorical and continuous spatial variables, with particular applications to geological features.\u0000 In this paper, we employ the tool to predict geological features based on airborne geophysical data acquired through the Tellus project in Northern Ireland. SOMs are applied through 8 experiments (iterations), incorporating the radiometric data in combination with geological features, including elevation, slope angle, terrain ruggedness (TRI), and geochronology. The SOMs proved successful in differentiating contrasting bedrock geology, such as acidic versus mafic igneous rocks, while data clustering over intermediate rocks was not as apparent. The presence of a thick cover of glacial deposits in most of the study area presented a challenge in the data clustering, particularly over the intermediate igneous and sedimentary bedrock types.\u0000 \u0000 Supplementary material:\u0000 https://doi.org/10.6084/m9.figshare.c.6603098\u0000","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44780356","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}

{"title":"Magnetostratigraphy of the Mercia Mudstone Group (Devon, UK): implications for regional relationships and chronostratigraphy in the Middle to Late Triassic of western Europe","authors":"M. Hounslow, R. Gallois","doi":"10.1144/jgs2022-173","DOIUrl":"https://doi.org/10.1144/jgs2022-173","url":null,"abstract":"Global synchronisation of environmental change in terrestrial successions in deep-time is challenging due to the paucity of dating methods, a case also applicable to the Middle to Upper Triassic Mercia Mudstone Group in Britain. Using coastal cliff sections, magnetostratigraphy was evaluated at 263 horizons, defining 53 magnetozones. Magnetozones from the lower 140 m of the group demonstrate correspondence to those from the mid Ladinian to early Carnian polarity timescale, dating which is compatible with magnetostratigraphy from the underlying Sherwood Sandstone Group. Magnetostratigraphy of the Dunscombe Mudstone Formation, and associated palynological data, suggest a late Carnian to earliest Norian age, and a dramatically lower accumulation rate than adjacent formations. The polarity record demonstrates coeval flooding events, evaporite deposits and intervals of sand supply between the Wessex Basin and the Central European Basin in the Carnian. This is the result of linked climatic and eustatic changes between these separate basins, related to aeolian dust supply and the shrinkage of hyper-arid source regions for the fines. Magnetostratigraphy from the Branscombe Mudstone and Blue Anchor formations demonstrates their Norian and early Rhaetian age. These and other data suggest an alternative synchronization of marine and non-marine polarity records for the Norian polarity timescale. 198 words\u0000 \u0000 Supplementary material:\u0000 Section details and detailed logs of the sampled sections and inferred sequence boundaries, magnetic mineralogy data, demagnetisation behaviour and mean directions, summary of virtual geomagnetic pole data and a comparison to other European poles, construction of other composite reference sections and revised polarity scales. Excel sheet of magnetic data statistically evaluated correlation models, and age models.\u0000 \u0000 \u0000 https://doi.org/10.6084/m9.figshare.c.6613788\u0000","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49256591","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}

{"title":"Structural configuration and tectonics of the Flemish Cap, offshore Newfoundland, from newly acquired seismic reflection data","authors":"P. Yang, J. Welford","doi":"10.1144/jgs2022-115","DOIUrl":"https://doi.org/10.1144/jgs2022-115","url":null,"abstract":"While the Flemish Cap played a pivotal role in the opening of the North Atlantic, the tectonic history of this continental ribbon has been poorly constrained due to insufficient seismic coverage. In this study, we present thirteen newly acquired seismic reflection profiles over the Flemish Cap, on which seismic reflectors show highly variable seismic facies both on and beneath the top acoustic basement, with exceptional imaging of layered crustal structure. The upper crust is primarily characterized by transparent, chaotic amplitude reflectivity. The lower crust, particularly on the flanks of the cap, exhibits relatively bright and coherent reflection packages interpreted as Appalachian orogenic fabrics based on onshore-offshore correlations from pre-rift plate reconstructions. Extensional systems within the continental crust of the Flemish Cap record a transitional stage between Paleozoic orogenic collapse and pre-Jurassic rifting. The crustal architecture associated with Mesozoic rifting of the Flemish Cap is also mapped and the interpreted distinct rift domains display along-strike variations. Overall, the complex tectonic history of the Flemish Cap involved dominantly ductile deformation during the Paleozoic orogenic stage, multiple deformation styles (primarily ductile and brittle-ductile) during the orogen-to-rift transitional stage, and brittle deformation during the major Jurassic-Cretaceous rifting stage.","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":"321 ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41274427","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}

{"title":"40\u0000 Ar/\u0000 39\u0000 Ar eruption ages of Turkana Basin tuffs: millennial scale resolution constrains paleoclimate proxy tuning models and hominin fossil ages","authors":"D. Phillips, E. Matchan, A. Gleadow, F. Brown, I. Mcdougall, T. Cerling, M. Leakey, J. Hergt, Louise N. Leakey","doi":"10.1144/jgs2022-171","DOIUrl":"https://doi.org/10.1144/jgs2022-171","url":null,"abstract":"\u0000 The Turkana Basin in Kenya/Ethiopia hosts remarkable fossil-rich sediments that are central to our understanding of early hominin evolution, with interbedded volcanic tuffs providing critical time markers. However, the resolution of existing Early Pleistocene/Pliocene ages is limited to ∼20-60 kyr, inhibiting evaluation of climatic/environmental drivers of evolution. Here, we present high precision, single-feldspar\u0000 40\u0000 Ar/\u0000 39\u0000 Ar age and elemental data for four stratigraphically significant tuffs. These samples exhibit variably dispersed age distributions correlated with feldspar compositional trends, interpreted to indicate partial retention of inherited argon, related to crustal ‘cold storage’ and rapid melt infiltration preceding eruption. We evaluated various statistical methods and calculate astronomically calibrated, Bayesian age estimates of 1879.1 ± 0.6 ka (± 2.4 ka including external errors) for the KBS/H2 Tuff, 1837.4 ± 0.9 ka (± 2.4 ka) for the Malbe/H4 Tuff, 1357.5 ± 1.8 ka (± 2.5 ka) for the Chari/L Tuff and 1315.4 ± 1.9 ka (± 2.5 ka) for the Gele Tuff. Our results permit refined age constraints for important early\u0000 Homo\u0000 fossils, including the cranium KNM-ER1813 (\u0000 Homo habilis\u0000 ) and various\u0000 Homo erectus\u0000 fossils. The KBS Tuff age also provides an important calibration locus for orbital tuning of paleoclimate proxy records, revealing complex interplay between paleoclimate and geological drivers of sedimentation.\u0000 \u0000 \u0000 Supplementary material:\u0000 https://doi.org/10.6084/m9.figshare.c.6602994\u0000","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45014060","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}

{"title":"Long silence on the East Anatolian Fault Zone (Southern Turkey) ends with devastating double earthquakes (6 February 2023) over a seismic gap: Implications for the seismic potential in the Eastern Mediterranean region","authors":"H. Karabulut, S. E. Güvercin, J. Hollingsworth, A. Konca","doi":"10.1144/jgs2023-021","DOIUrl":"https://doi.org/10.1144/jgs2023-021","url":null,"abstract":"On the 06th February 2023, an earthquake with magnitude ∼Mw7.0 on the Narlı Fault, a fault subparallel to the East Anatolian Fault Zone (EAFZ), initiated a chain of large earthquakes on the EAFZ. The earthquakes occurred in a seismic gap with low geodetic strain rates, low background seismicity, where deformation is distributed across a wide fault zone and long recurrence time of historical earthquakes. The ∼50 km long rupture of the Narlı Fault towards Pazarcık, led to Mw7.8 left-lateral strike-slip earthquake breaking ∼300 km section of the ∼600 km long EAFZ bilaterally with a total duration of more than 80 s. Toward the southwest, the rupture propagated on ∼100 km long Amanos segment with a peak surface offset of 5 m, before diminishing toward the Hatay graben. In the northeast direction, the rupture reached a peak surface offset of 7 m before sharply declining at the termination of the 2020, Mw6.8 Sivrice earthquake rupture. A second large earthquake with Mw7.6 occurred 9 hours later on the Çardak Fault, located at the western margin of (and sub-parallel to) the EAFZ breaking the surface with almost 9 m left-lateral slip (average of ∼4 m). Following these large earthquakes, the increase in the regional stress led to a rapid seismic activation in a broad region from central to eastern Anatolia loading the faults at various scales and increasing seismic hazard. Two weeks after the initiation of the seismic crisis, a third earthquake with Mw6.4 occurred at the southern boundary of the Hatay graben, near the southwestern termination of the Amanos rupture. The earthquakes caused significant loss of human life, devastating 12 cities. We evaluate the observations prior to the ruptures, present preliminary seismological results with surface displacements from sub-pixel correlation of optical satellite images and the stress perturbations computed on the nearby faults based on preliminary slip models. The reevaluation of the seismic potential in light of the recent and historical earthquakes provides some new insight on seismic hazard assessment. The recent series of events on the EAFZ is an important reminder that large faults can generate very large earthquakes of multiple segments. The seismic potential of large earthquakes on these fault zones can only be estimated by considering multiple seismic cycles, and moment deficits from very large earthquakes.\u0000 \u0000 Supplementary material:\u0000 https://doi.org/10.6084/m9.figshare.c.6567094\u0000","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45921256","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}

{"title":"Discussion on Koglin et al. (2022): The Lerner Deformation Zone as part of a Scandian core complex","authors":"H. Maher, A. Braathen, M. Ganerød, P. Myhre, P. Osmundsen, T. Redfield","doi":"10.1144/jgs2022-179","DOIUrl":"https://doi.org/10.1144/jgs2022-179","url":null,"abstract":"Koglin et al. (2022) present valuable new isotopic and field data regarding northwest Spitsbergen's tectonic history, and propose the existence of the Germaniahalvøya terrane with Scandian (Late Caledonian) igneous activity and deformation. Within this terrane, the Lerner Deformation zone (LDZ), is cast as an east-directed thrust, with the Liefdefjorden Migmatite Complex in the footwall and Lenerøyane Group meta-sediments above. The LDZ occurs on the west limb of the major, shallowly north plunging, Bockfjorden anticline. We suggest their data supports the unmentioned and discussed idea (Dallmann & Piepjohn 2018, Braathen et al. 2018) that a Scandian metamorphic core complex exists here and that the LDZ is part of the Keisarhjelmen extensional detachment (Braathen et al. 2017, Maher et. al. 2022). The detachment consists of ductile to brittle, retrogressive, fault rocks up to several hundred meters thick along the contact between metamorphic basement and overlying Devonian basin strata. In addition, we note that Koglin et al's (2022) evidence for Scandian activity is consistent with core complex dynamics.","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41762940","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}

{"title":"A detective duo of apatite and zircon geochronology for East Avalonia, Johnston Complex, Wales","authors":"Anthony J.I. Clarke, C. Kirkland, S. Glorie","doi":"10.1144/jgs2022-178","DOIUrl":"https://doi.org/10.1144/jgs2022-178","url":null,"abstract":"\u0000 The Johnston Complex represents a rare inlier of the Neoproterozoic basement of southern Britain and offers a window into the tectonomagmatic regime of East Avalonia during the assembly of Gondwana. This work presents\u0000 in-situ\u0000 zircon (U-Pb, Lu-Hf), apatite (U-Pb), and trace element chemistry for both minerals from the Complex. Zircon and apatite yield a coeval crystallisation age of 570 ± 3 Ma, and a minor antecrystic zircon core component is identified at 615 ± 11 Ma. Zircon Lu-Hf data imply a broadly chondritic source, comparable to Nd data from East Avalonia, and T\u0000 DM\u0000 2\u0000 model ages of ca. 1.5 Ga indicate source extraction during the Mesoproterozoic. Zircon trace element chemistry is consistent with an ensialic calc-alkaline continental arc setting and demonstrates that magmatism was ongoing prior to terrane dispersal at 570 Ma. Apatite trace element chemistry implies a sedimentary component within the melt consistent with voluminous S-type granite production during the formation of Gondwana. The similarity of ɛHf and geochemistry between both zircon age populations suggest derivation from a uniform source that did not undergo significant modification between 615 – 570 Ma. Time-constrained apatite-zircon chemistry addresses complexities in dating S-type granitoids (zircon inheritance) and permits inferences on post-magmatic thermal histories.\u0000 \u0000 \u0000 Supplementary material:\u0000 https://doi.org/10.6084/m9.figshare.c.6484464\u0000","PeriodicalId":17320,"journal":{"name":"Journal of the Geological Society","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2023-03-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42842314","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}