Proceedings of the Geologists Association最新文献

{"title":"A time-transgressive model for microstructures in subglacial tills - Examples from beneath the Late Wisconsinan (MI 2) Laurentide Ice Sheet","authors":"John Menzies ,&nbsp;Roger C. Paulen ,&nbsp;Jessey M. Rice","doi":"10.1016/j.pgeola.2023.05.005","DOIUrl":"https://doi.org/10.1016/j.pgeola.2023.05.005","url":null,"abstract":"<div><p>The complexity of subglacial till sedimentology is discussed at the microscale to develop a revised model of microstructure evolution and development in subglacial tills. Mapped thin sections from the Northwest Territories and southern Ontario, Canada reveal a myriad of microstructures. Discussion of the relevance and meaning of these microstructures leads to a new revised model of subglacial soft sediment deformation to account for the development and evolution of these microstructures. The model is time-transgressive such that over time both pervasive and non-pervasive deformation conditions persist repetitively within the subglacial till environment under mixed rheologies. Microstructure types appear to be sequential in development and, during progression, are partially or wholly overprinted, destroyed, rotated, and suffer further subsequent deformation, or remain intact but intercalated with structures of other later or earlier deformation phases. This new revised model helps explain that the vagaries of till microsedimentology can be accounted for and, in most instances, predicted.</p></div>","PeriodicalId":49672,"journal":{"name":"Proceedings of the Geologists Association","volume":"134 5","pages":"Pages 533-546"},"PeriodicalIF":1.2,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71771402","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Facies, diagenesis, and palaeo-environment significances of the Plio-Quaternary fluvio-lacustrine deposits of Ain Cheggag region, Sais foreland basin, Morocco","authors":"Hicham El Asmi ,&nbsp;Lahcen Gourari ,&nbsp;Imad El Yakouti ,&nbsp;Khalil Azennoud ,&nbsp;Aziz Hayati ,&nbsp;Mohamed Benabbou ,&nbsp;Mohammed Lghamour ,&nbsp;Yassine Ait Bharhim ,&nbsp;El Hassane Chellai","doi":"10.1016/j.pgeola.2023.09.004","DOIUrl":"https://doi.org/10.1016/j.pgeola.2023.09.004","url":null,"abstract":"<div><p><span>Fluvio-lacustrine deposits are promising archives that afford to decipher climate and tectonic signatures, typically when evidence of changes in the depositional settings therein is remarkable. As such, the present work coveys a case study whose fluvio-lacustrine deposits may serve to provide insights into climate and tectonic controls on palaeoenvironmental settings. The study area lies in the northwestern portion of Ain Cheggag, southeastern the Sais foreland basin<span> (northern Morocco). The lithostratigraphical analysis of Plio-Quaternary fluvio-lacustrine deposits in the area has enabled the identification of nine facies. The depositional systems are organized into three deposit units, each of which reflects a typical depositional environment<span>. The first (lower) unit consists of detrital facies implying deposition in alluvial-dominated settings. The alternation of detrital and carbonate facies giving way to the second (middle) unit suggests sedimentation in a fluvio-lacustrine environment. Whilst being carbonate-rich, the third (upper) unit reflects a shift into lacustrine-dominated settings. Accordingly, the vertical succession of the sedimentary pile delivers remarkable insights into a general palaeo-environmental shift from alluvial settings, with enhanced pedogenesis processes, towards carbonate-dominated lacustrine conditions where early- and late-stage </span></span></span>diagenesis<span><span> processes would have prevailed. This broad shift in depositional systems is likely to be the response of palaeohydrological changes that are modulated both by the neotectonic<span> subsidence background and, specifically, the general </span></span>palaeoclimate<span><span> evolution towards more humid conditions. Bioturbation, desiccation, and void-filling with internal sediments are key features of early-stage diagenesis processes, whereas </span>cementation, micritization, recrystallization, dissolution, and iron and manganese oxidation are the main features of late-stage diagenesis altering the primary structures of the studied deposits. Finally, we highlight the significance of fluviolacustrine deposits in deciphering palaeoclimatic signatures and tectonic implications.</span></span></p></div>","PeriodicalId":49672,"journal":{"name":"Proceedings of the Geologists Association","volume":"134 5","pages":"Pages 641-653"},"PeriodicalIF":1.2,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71771462","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The first record of calcitarchs from the Takche Formation (Ordovician–Silurian), Himalaya (India)","authors":"Olev Vinn ,&nbsp;Ravi S. Chaubey ,&nbsp;Birendra P. Singh ,&nbsp;Om N. Bhargava ,&nbsp;Subhay K. Prasad","doi":"10.1016/j.pgeola.2023.07.008","DOIUrl":"https://doi.org/10.1016/j.pgeola.2023.07.008","url":null,"abstract":"<div><p><span><span>Limestones of the Takche Formation (Spiti, Himalaya) are characterized by normal marine fauna and flora typical for the </span>Late Ordovician<span><span>. The flora is represented by algae, mostly by receptaculitids and dasyclad green algae. Various calcareous </span>microorganisms such as calcitarchs, </span></span><em>Rothpletzella</em> and <em>Girvanella</em><span><span><span> are present. There are some differences in the microfossil content and abundance between different </span>lithofacies of the Takche Formation. Two main </span>biofacies<span> types could be recognized on the basis of the abundance of algae and calcitarchs, namely algal rich and algal poor biofacies. The abundance of dasyclad green algae in limestones of the Takche Formation is characteristic of the warm climate. The Himalaya (Gondwana) has calcitarchs in common with Baltica.</span></span></p></div>","PeriodicalId":49672,"journal":{"name":"Proceedings of the Geologists Association","volume":"134 5","pages":"Pages 590-598"},"PeriodicalIF":1.2,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71771464","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"","authors":"Dmitry A. Ruban","doi":"10.1016/j.pgeola.2023.07.004","DOIUrl":"https://doi.org/10.1016/j.pgeola.2023.07.004","url":null,"abstract":"","PeriodicalId":49672,"journal":{"name":"Proceedings of the Geologists Association","volume":"134 5","pages":"Pages 662-663"},"PeriodicalIF":1.2,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71772175","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Excavating the ‘Rutland Sea Dragon’: The largest ichthyosaur skeleton ever found in the UK (Whitby Mudstone Formation, Toarcian, Lower Jurassic)","authors":"Nigel R. Larkin ,&nbsp;Dean R. Lomax ,&nbsp;Mark Evans ,&nbsp;Emma Nicholls ,&nbsp;Steven Dey ,&nbsp;Ian Boomer ,&nbsp;Philip Copestake ,&nbsp;Paul Bown ,&nbsp;James B. Riding ,&nbsp;Darren Withers ,&nbsp;Joseph Davis","doi":"10.1016/j.pgeola.2023.09.003","DOIUrl":"https://doi.org/10.1016/j.pgeola.2023.09.003","url":null,"abstract":"<div><p>An almost complete ichthyosaur skeleton 10 m long was discovered in January 2021 at the Rutland Water Nature Reserve in the county of Rutland, UK. This was excavated by a small team of palaeontologists in the summer of the same year. Nicknamed ‘The Rutland Sea Dragon’, this almost fully articulated skeleton is an example of the large-bodied Early Jurassic ichthyosaur <em>Temnodontosaurus</em>. The specimen was analysed <em>in situ</em>, recorded (including a 3D scan using photogrammetry), excavated and removed from the site in a series of large plaster field jackets to preserve taphonomic information. Significantly, the specimen is the largest ichthyosaur skeleton to have been found in the UK and it may be the first recorded example of <em>Temnodontosaurus trigonodon</em> to be found in the country, extending its known geographic range significantly. It also represents the most complete skeleton of a large prehistoric reptile to have been found in the UK. We provide an account of the discovery and describe the methods used for excavating, recording and lifting the large skeleton which will aid palaeontologists facing similar challenges when collecting extensive remains of large and fragile fossil vertebrates. We also discuss the preliminary research findings and the global impact this discovery has had through public engagement.</p></div>","PeriodicalId":49672,"journal":{"name":"Proceedings of the Geologists Association","volume":"134 5","pages":"Pages 627-640"},"PeriodicalIF":1.2,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71771460","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The fossil record's oldest known calculus (an enterolith of the gastrointestinal tract), from the Kimmeridge Clay Formation (Upper Jurassic), UK","authors":"Nigel R. Larkin ,&nbsp;Thomas Henton ,&nbsp;Steve Etches ,&nbsp;Adrian J. Wright ,&nbsp;Tzu-Yu Chen ,&nbsp;Laura L. Driscoll ,&nbsp;Richard M. Shelton ,&nbsp;Ivan J. Sansom","doi":"10.1016/j.pgeola.2023.05.004","DOIUrl":"https://doi.org/10.1016/j.pgeola.2023.05.004","url":null,"abstract":"<div><p><span>A calculus is a solid mineral concretion such as a kidney stone, bladder stone, gall stone or stomach stone that forms naturally in a body under certain dietary or environmental conditions. Calculi that form in the gastrointestinal tract are enteroliths and these are often near-spherical objects, sometimes with a hollow centre, with a concentrically layered structure composed of radiating crystals oriented perpendicular to the surface. They are known in the archaeological record but are almost entirely absent from the fossil record, most likely due to them simply not being recognised for what they are. We describe a fossil calculus from the Upper Kimmeridge Clay (Upper Jurassic, </span><em>c.</em><span>, 150 million years old) marine deposit at Kimmeridge in Dorset, UK. This is the oldest calculus known from the fossil record with previous confirmed records from the terrestrial Oligocene<span> of Colorado and the marine Upper Cretaceous Chalk of Germany: it extends the temporal range of known calculi in the fossil record by at least 59 million years. Although there are a wide range of potential hosts, the Kimmeridge calculus may have been produced by a large marine reptile.</span></span></p></div>","PeriodicalId":49672,"journal":{"name":"Proceedings of the Geologists Association","volume":"134 5","pages":"Pages 526-532"},"PeriodicalIF":1.2,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71771404","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"New exposure of the Cretaceous–Paleogene unconformity and Paleocene–Eocene pebble bed in the Paleogene outlier at Collier's End, Hertfordshire, UK","authors":"Bryan Lovell ,&nbsp;Haydon Bailey ,&nbsp;Andrew R. Farrant ,&nbsp;Liam Gallagher ,&nbsp;Chris Green ,&nbsp;Jennifer Huggett ,&nbsp;Russell Parkins ,&nbsp;Jane Tubb","doi":"10.1016/j.pgeola.2023.05.002","DOIUrl":"https://doi.org/10.1016/j.pgeola.2023.05.002","url":null,"abstract":"<div><p><span>The Paleogene outlier at Collier's End, Hertfordshire lies on the northern rim of the </span>London<span> Basin. This small outlier has archaeological and geological significance. Silica-cemented concretions of Hertfordshire Puddingstone lie within a regionally mappable pebble bed. The first discovery of a Roman quarry to recover puddingstone for manufacture of querns was made in the outlier. A rare complete section from the Chalk Group up through the Paleogene was temporarily exposed in 2021 and is recorded here. The Paleogene shows features that may be associated with the Paleocene–Eocene Thermal Maximum (PETM). The chalk in the new exposure is Late Coniacian<span>. This age provides further evidence of relatively deep erosion of the chalk in this area, as erosion of chalk at the crest of a regional dome preceded advances and retreats of the western shore of the Paleogene North Sea. These events may be linked to the early development of the Icelandic mantle plume.</span></span></p></div>","PeriodicalId":49672,"journal":{"name":"Proceedings of the Geologists Association","volume":"134 5","pages":"Pages 503-516"},"PeriodicalIF":1.2,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71771406","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"","authors":"Stephen Tooth","doi":"10.1016/j.pgeola.2023.05.001","DOIUrl":"https://doi.org/10.1016/j.pgeola.2023.05.001","url":null,"abstract":"","PeriodicalId":49672,"journal":{"name":"Proceedings of the Geologists Association","volume":"134 5","pages":"Pages 657-658"},"PeriodicalIF":1.2,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71771458","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Simon Richard Appleton Kelly (1949–2023)","authors":"Simon Schneider,&nbsp;Michael A. Pointon","doi":"10.1016/j.pgeola.2023.09.002","DOIUrl":"https://doi.org/10.1016/j.pgeola.2023.09.002","url":null,"abstract":"","PeriodicalId":49672,"journal":{"name":"Proceedings of the Geologists Association","volume":"134 5","pages":"Pages 654-656"},"PeriodicalIF":1.2,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71771459","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cosmogenic (10Be) surface-exposure ages from the Burtness Comb rock avalanche, Lake District, northwest England","authors":"Peter Wilson ,&nbsp;David Jarman ,&nbsp;Maria Miguens-Rodriguez ,&nbsp;Derek Fabel","doi":"10.1016/j.pgeola.2023.09.001","DOIUrl":"https://doi.org/10.1016/j.pgeola.2023.09.001","url":null,"abstract":"<div><p><span>The age of the lower component of the Burtness Comb rock avalanche debris tongue, Lake District, northwest England, has been determined by </span><em>in situ</em> produced terrestrial cosmogenic (¹⁰<span><span>Be) surface-exposure dating of quartz veins from three boulders. Uncertainty-weighted mean ages of 17.37 ± 0.94 ka (determined using the Loch Lomond calibration dataset) and 16.08 ± 1.25 ka (determined using the CRONUS-Earth default calibration dataset) indicate that this component of the rock avalanche occurred during </span>deglaciation<span><span> following the local Last Glacial Maximum. The surface morphology displayed by the debris indicates it likely accumulated on glacier-free terrain, suggesting that the Burtness Comb </span>cirque glacier had decoupled from the Buttermere valley glacier at the time of debris emplacement. The debris may have travelled across the surface of a waning glacier in the upper part of the cirque. Although the upper component of the rock avalanche is as yet undated its position and configuration indicate it to be younger than the lower component and sourced from a different part of the comb headwall. The rock avalanche is only the third of 84 rock slope failures recognised in the Lake District and adjacent Howgill Fells to have been dated using </span></span>¹⁰<span>Be. Whilst the rock avalanche is regarded as a paraglacial landform, additional ages on other members of this population are required in order to establish their temporal pattern and to propose the most probable underlying cause(s) of failure.</span></p></div>","PeriodicalId":49672,"journal":{"name":"Proceedings of the Geologists Association","volume":"134 5","pages":"Pages 619-626"},"PeriodicalIF":1.2,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71771461","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}