Pub Date : 2025-06-02DOI: 10.1016/j.pgeola.2025.101125
John K. Wright
A critical investigation is made of the unconformities reportedly present in Oxford Clay Formation and Corallian Group (Jurassic, Oxfordian) strata in central and southern England. A revised cross-section through strata belonging to the coeval Coralline Oolite Group and Upper Calcareous Grit and Ampthill Clay formations of the Tabular Hills, North Yorkshire is used to show the lateral extent of unconformities within these strata. There is definite correlation of only two of these unconformities present in Yorkshire with similar erosive episodes in the equivalent strata in southern England. The extent to which the sequences of strata delimited by these unconformities can be correlated with sequences defined in the North Sea Basin is discussed. The tectonic nature of the unconformities is evident, as there was not a simple drop in relative sea-level causing erosion. Erosion occurred down to deeper levels in certain areas, this being caused by differential uplift. The reasons for this phenomenon are still to be determined.
{"title":"Review of Oxfordian (Upper Jurassic) sequence stratigraphy of England (Yorkshire to Dorset) and a comparison with the North Sea Basin","authors":"John K. Wright","doi":"10.1016/j.pgeola.2025.101125","DOIUrl":"10.1016/j.pgeola.2025.101125","url":null,"abstract":"<div><div>A critical investigation is made of the unconformities reportedly present in Oxford Clay Formation and Corallian Group (Jurassic, Oxfordian) strata in central and southern England. A revised cross-section through strata belonging to the coeval Coralline Oolite Group and Upper Calcareous Grit and Ampthill Clay formations of the Tabular Hills, North Yorkshire is used to show the lateral extent of unconformities within these strata. There is definite correlation of only two of these unconformities present in Yorkshire with similar erosive episodes in the equivalent strata in southern England. The extent to which the sequences of strata delimited by these unconformities can be correlated with sequences defined in the North Sea Basin is discussed. The tectonic nature of the unconformities is evident, as there was not a simple drop in relative sea-level causing erosion. Erosion occurred down to deeper levels in certain areas, this being caused by differential uplift. The reasons for this phenomenon are still to be determined.</div></div>","PeriodicalId":49672,"journal":{"name":"Proceedings of the Geologists Association","volume":"136 5","pages":"Article 101125"},"PeriodicalIF":1.3,"publicationDate":"2025-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145128505","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}
Pub Date : 2025-04-25DOI: 10.1016/j.pgeola.2025.101117
Robert Chandler , Stefano Cresta
The rare ammonite genus Bajocia is reported, as Bajocia *farcyi Brasil, for the first time from the Middle Jurassic, Lower Bajocian Humphriesianum Zone, Romani Subzone of Dorset, UK. Bajocia paiardinii Chandler and Cresta sp. nov. is erected from the Humphriesianum Zone, uppermost Romani or lowest Humphriesianum Subzone of Monte Nerone, Apennines, Italy. The taxonomic and stratigraphical position of the genus is considered and possible evolutionary routes are suggested. The genus is likely to have evolved in the Tethys–Panthalassa Realm or southern Mediterranean–Caucasian Subrealm. Leptosphinctids, the earliest Perisphinctidae probably originated from Western Tethyan Stephanoceratidae.
{"title":"New records of ammonites from the Lower Bajocian (Middle Jurassic) of England and Italy","authors":"Robert Chandler , Stefano Cresta","doi":"10.1016/j.pgeola.2025.101117","DOIUrl":"10.1016/j.pgeola.2025.101117","url":null,"abstract":"<div><div><span>The rare ammonite genus </span><em>Bajocia</em> is reported, as <em>Bajocia *farcyi</em><span> Brasil, for the first time from the Middle Jurassic<span>, Lower Bajocian Humphriesianum Zone, Romani Subzone of Dorset, UK. </span></span><em>Bajocia paiardinii</em> Chandler and Cresta sp. nov. is erected from the Humphriesianum Zone, uppermost Romani or lowest Humphriesianum Subzone of Monte Nerone, Apennines, Italy. The taxonomic and stratigraphical position of the genus is considered and possible evolutionary routes are suggested. The genus is likely to have evolved in the Tethys–Panthalassa Realm or southern Mediterranean–Caucasian Subrealm. Leptosphinctids, the earliest Perisphinctidae probably originated from Western Tethyan Stephanoceratidae.</div></div>","PeriodicalId":49672,"journal":{"name":"Proceedings of the Geologists Association","volume":"136 5","pages":"Article 101117"},"PeriodicalIF":1.3,"publicationDate":"2025-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145128504","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}
Pub Date : 2025-04-15DOI: 10.1016/j.pgeola.2025.101115
Paul G. Davis, Chris Paul, Heather Salmon
A specimen of the nautiloid, Cenoceras pertextum (Dumortier), from the Lower Pliensbachian, Belemnite Stone (bed 121), Charmouth Mudstone Formation, bears four small round or oval pits with a 4.0–7.5 mm maximum dimension that resemble similar structures on Cretaceous ammonites interpreted as limpet home scars. The pits are clustered near the periphery of the nautiloid shell, on the left side. This was the highest point on the nautiloid shell if orientated in the life position of modern Nautilus macromphalus. Long axes of the pits align with the growth direction of the nautiloid shell. Both features suggest that the nautiloid was alive when the limpet scars formed. To maintain aperture orientation during growth nautiloid shells rotate. Thus, forming deep limpet scars at the highest point can only be achieved on mature nautiloid shells. An ammonite, Liparoceras pseudostriatum Trueman, occurs in the body chamber, confirming the source rock, and sediment fill indicates that the shell lay on its right side post-mortem forming a benthic island. Attachment of the limpets after the death of the nautiloid does not explain the position and orientation of the scars and seems less likely. Fossil limpet shells have been recorded from the Upper Sinemurian, Black Ven Mudstone Member (beds 91 and 92), lower in the Charmouth Mudstone Formation.
{"title":"Possible limpet home scars on a nautiloid from the Belemnite Stone (Lower Jurassic) near Lyme Regis, Dorset, UK","authors":"Paul G. Davis, Chris Paul, Heather Salmon","doi":"10.1016/j.pgeola.2025.101115","DOIUrl":"10.1016/j.pgeola.2025.101115","url":null,"abstract":"<div><div>A specimen of the nautiloid, <em>Cenoceras pertextum</em><span><span> (Dumortier), from the Lower Pliensbachian, </span>Belemnite<span> Stone (bed 121), Charmouth Mudstone<span> Formation, bears four small round or oval pits with a 4.0–7.5 mm maximum dimension that resemble similar structures on Cretaceous ammonites interpreted as limpet home scars. The pits are clustered near the periphery of the nautiloid shell, on the left side. This was the highest point on the nautiloid shell if orientated in the life position of modern </span></span></span><em>Nautilus macromphalus</em>. Long axes of the pits align with the growth direction of the nautiloid shell. Both features suggest that the nautiloid was alive when the limpet scars formed. To maintain aperture orientation during growth nautiloid shells rotate. Thus, forming deep limpet scars at the highest point can only be achieved on mature nautiloid shells. An ammonite, <em>Liparoceras pseudostriatum</em><span> Trueman, occurs in the body chamber, confirming the source rock, and sediment fill indicates that the shell lay on its right side post-mortem forming a benthic island. Attachment of the limpets after the death of the nautiloid does not explain the position and orientation of the scars and seems less likely. Fossil<span><span> limpet shells have been recorded from the Upper Sinemurian, Black Ven </span>Mudstone Member (beds 91 and 92), lower in the Charmouth Mudstone Formation.</span></span></div></div>","PeriodicalId":49672,"journal":{"name":"Proceedings of the Geologists Association","volume":"136 5","pages":"Article 101115"},"PeriodicalIF":1.3,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145128502","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}
Pub Date : 2025-04-14DOI: 10.1016/j.pgeola.2025.101114
Ian Jarvis , Elizabeth Atar , Darren R. Gröcke , João P. Trabucho-Alexandre
The Pliensbachian–Toarcian of the Cleveland Basin provides a global reference for the interval incorporating the Toarcian Oceanic Anoxic Event (T-OAE ~ 183 Ma). Palaeoredox proxies show a progressive shift from oxic bottom waters in the late Pliensbachian through dysoxic–anoxic conditions in the earliest Toarcian to euxinia during the T-OAE. Anoxia–dysoxia persisted into the middle Toarcian. Laminated black shales with TOC contents > 2.5 % characterise the anoxic–euxinic intervals. The rare-earth element (REE) geochemistry of the succession sampled in the Dove's Nest core is described and compared to data from nearby Yorkshire coastal outcrops. Interpretation is based on a review of REE behaviour in modern marine water columns, pore waters and sediments. Mud(stone) REE patterns are insensitive to bottom-water redox conditions. The REEs are principally located in the siliciclastic clay fraction of modern marine muds and ancient mudstones. Bulk mud(stone)s generally exhibit relatively flat REE patterns when normalised to average shale. Cerium anomalies are largely absent. Stratigraphical trends in the Yorkshire succession are related principally to sediment grain size. Authigenic and biogenic phosphates, principally carbonate fluorapatite, when present, dominate the whole-rock REE inventory leading to convex-upward patterns and large positive middle REE (MREE/MREE*) anomalies. These occur sporadically throughout the oxic–euxinic intervals, showing no correlation to bottom-water redox. The REE geochemistry of marine mudstones presents a combination of primary mineralogical and grain-size controls related to sediment provenance combined with the impact of authigenic mineral formation. Bulk mudstone REE patterns do not provide a viable bottom-water redox proxy.
{"title":"Do REEs in mudstones record bottom-water redox?: The Pliensbachian–Toarcian record (Lower Jurassic) and T-OAE in the Cleveland Basin, England","authors":"Ian Jarvis , Elizabeth Atar , Darren R. Gröcke , João P. Trabucho-Alexandre","doi":"10.1016/j.pgeola.2025.101114","DOIUrl":"10.1016/j.pgeola.2025.101114","url":null,"abstract":"<div><div>The Pliensbachian–Toarcian of the Cleveland Basin provides a global reference for the interval incorporating the Toarcian Oceanic Anoxic Event (T-OAE ~<!--> <!-->183 Ma). Palaeoredox proxies show a progressive shift from oxic bottom waters in the late Pliensbachian through dysoxic–anoxic conditions in the earliest Toarcian to euxinia during the T-OAE. Anoxia–dysoxia persisted into the middle Toarcian. Laminated black shales with TOC contents ><!--> <!-->2.5 % characterise the anoxic–euxinic intervals. The rare-earth element (REE) geochemistry of the succession sampled in the Dove's Nest core is described and compared to data from nearby Yorkshire coastal outcrops. Interpretation is based on a review of REE behaviour in modern marine water columns, pore waters and sediments. Mud(stone) REE patterns are insensitive to bottom-water redox conditions. The REEs are principally located in the siliciclastic clay fraction of modern marine muds and ancient mudstones. Bulk mud(stone)s generally exhibit relatively flat REE patterns when normalised to average shale. Cerium anomalies are largely absent. Stratigraphical trends in the Yorkshire succession are related principally to sediment grain size. Authigenic and biogenic phosphates, principally carbonate fluorapatite, when present, dominate the whole-rock REE inventory leading to convex-upward patterns and large positive middle REE (MREE/MREE*) anomalies. These occur sporadically throughout the oxic–euxinic intervals, showing no correlation to bottom-water redox. The REE geochemistry of marine mudstones presents a combination of primary mineralogical and grain-size controls related to sediment provenance combined with the impact of authigenic mineral formation. Bulk mudstone REE patterns do not provide a viable bottom-water redox proxy.</div></div>","PeriodicalId":49672,"journal":{"name":"Proceedings of the Geologists Association","volume":"136 4","pages":"Article 101114"},"PeriodicalIF":1.2,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144322891","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}
Pub Date : 2025-04-10DOI: 10.1016/j.pgeola.2025.101116
Carlos A. Góis-Marques , Pedro Correia , Miguel Menezes de Sequeira
Due to the unusual presence of coal seams within a volcanic island, the São Jorge lignite, located in the north side of Madeira Island, was since the early 19th century a magnet for naturalists. In 1854 the site was visited by Sir Charles Lyell and Georg Hartung, where both discovered a leaf-bed associated with the lignite. This finding provided key proofs to Lyell's uniformitarian theory of the formation of volcanic islands and the long-term existence of laurel forests in Macaronesia. Despite its historical importance, lignite specimens from São Jorge remain unknown to date. Recently, the study of Funchal Natural History Museum (MMF, Madeira Island, Portugal) collections revealed a coal specimen associated with the classical site of São Jorge. Here we provide a critical analysis of this specimen using historical and palaeobotanical approaches. We show that this coal is not a lignite from São Jorge and that it was not collected in ca. 1905. Historically, the São Jorge site was covered by a landslide until 1917, making it inaccessible. Furthermore, the coal is either a bituminous coal or anthracite and contains typical rhizomorph fossils of extinct Lycophytes known as Stigmaria ficoides (Sternb.) Brongn., as already indicated in the old MMF record books. The coal is most likely a late Carboniferous (Pennsylvanian, 323.4–298.9 Ma) specimen from the early 20th century British coaling industry on Madeira Island, imported from the UK, which, at some point, was erroneously labelled as originating from the 7–1.8 Ma São Jorge outcrop in Madeira.
由于火山岛上不寻常的煤层存在，位于马德拉岛北侧的s o Jorge褐煤自19世纪初以来一直吸引着博物学家。1854年，查尔斯·莱尔爵士和乔治·哈通参观了这个地方，在那里他们都发现了一个与褐煤有关的叶床。这一发现为莱尔关于火山岛形成和马卡罗尼西亚月桂林长期存在的均变说理论提供了关键证据。尽管它具有重要的历史意义，但迄今为止，奥豪尔赫褐煤标本仍不为人所知。最近，对丰哈尔自然历史博物馆（MMF， Madeira岛，葡萄牙）藏品的研究发现了一个与古典遗址 o Jorge有关的煤炭标本。在这里，我们使用历史和古植物学方法对该标本进行了批判性分析。我们证明，这种煤不是来自奥若热褐煤，它不是在大约1905年收集的。从历史上看，奥豪尔赫遗址一直被山体滑坡覆盖，直到1917年才进入。此外，煤要么是烟煤，要么是无烟煤，并含有已灭绝的石松类植物的典型根状化石，称为stistimaria ficoides （Sternb.）。Brongn。，正如旧的MMF记录簿中已经指出的那样。这些煤很可能是20世纪初英国在马德拉岛的煤炭工业中从英国进口的晚石炭世（宾夕法尼亚，323.4-298.9 Ma）标本，在某种程度上，这些煤被错误地标记为来自马德拉岛7-1.8 Ma ss o Jorge露头。
{"title":"On a coal specimen possibly associated with the classical Mio-Pleistocene São Jorge leaf bed site, Madeira Island, Portugal","authors":"Carlos A. Góis-Marques , Pedro Correia , Miguel Menezes de Sequeira","doi":"10.1016/j.pgeola.2025.101116","DOIUrl":"10.1016/j.pgeola.2025.101116","url":null,"abstract":"<div><div>Due to the unusual presence of coal seams within a volcanic island, the São Jorge lignite, located in the north side of Madeira Island, was since the early 19th century a magnet for naturalists. In 1854 the site was visited by Sir Charles Lyell and Georg Hartung, where both discovered a leaf-bed associated with the lignite. This finding provided key proofs to Lyell's uniformitarian theory of the formation of volcanic islands and the long-term existence of laurel forests in Macaronesia. Despite its historical importance, lignite specimens from São Jorge remain unknown to date. Recently, the study of Funchal Natural History Museum (MMF, Madeira Island, Portugal) collections revealed a coal specimen associated with the classical site of São Jorge. Here we provide a critical analysis of this specimen using historical and palaeobotanical approaches. We show that this coal is not a lignite from São Jorge and that it was not collected in <em>ca.</em> 1905. Historically, the São Jorge site was covered by a landslide until 1917, making it inaccessible. Furthermore, the coal is either a bituminous coal or anthracite and contains typical rhizomorph fossils of extinct Lycophytes known as <em>Stigmaria ficoides</em> (Sternb.) Brongn., as already indicated in the old MMF record books. The coal is most likely a late Carboniferous (Pennsylvanian, 323.4–298.9 Ma) specimen from the early 20th century British coaling industry on Madeira Island, imported from the UK, which, at some point, was erroneously labelled as originating from the 7–1.8 Ma São Jorge outcrop in Madeira.</div></div>","PeriodicalId":49672,"journal":{"name":"Proceedings of the Geologists Association","volume":"136 5","pages":"Article 101116"},"PeriodicalIF":1.3,"publicationDate":"2025-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145128503","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}
Pub Date : 2025-03-29DOI: 10.1016/j.pgeola.2025.101112
Oliver J. Weeks , Rebecca B. Cooper , David I. Whiteside , Christopher J. Duffin , Charles Copp , Claudia Hildebrandt , Deborah Hutchinson , Michael J. Benton
Dating the Mesozoic-aged fissure deposits around Bristol and South Wales has been problematic, with ages of the older examples disputed as either Carnian or Rhaetian, a 30-million-year difference. The deposits filling fissures at Holwell, Somerset offer a chance to establish a date for at least one system of fissures because they are on the coast of the Mendip Palaeoisland, close to bedded Rhaetian marine deposits. The Holwell fissures have been known since the 1850s when they yielded some of the first ever reported Mesozoic mammals, and they are the type locality for several fossil shark species, Duffinselache holwellensis, Pseudocetorhinus pickfordi and Palaeobates reticulatus. Bone-rich fissure fills from a neptunian dyke at Holwell yielded over 3000 identifiable specimens, comprising mainly marine fishes but also coastal-dwelling placodonts and terrestrially derived lepidosaurs that lived on the palaeoisland. Over 95 % of the fauna comprises four fish taxa that are typical of the bedded Westbury Formation. The less common Rhomphaiodon minor associated with abundant Synechodus rhaeticus indicates that the deposits are likely not basal but are within the upper half of the Westbury Formation. We hereby confirm that these Holwell fissure fill faunas, including the mammals, are of Rhaetian age.
{"title":"Microvertebrates from a Rhaetian neptunian dyke at Holwell, Somerset: Dating the fissures","authors":"Oliver J. Weeks , Rebecca B. Cooper , David I. Whiteside , Christopher J. Duffin , Charles Copp , Claudia Hildebrandt , Deborah Hutchinson , Michael J. Benton","doi":"10.1016/j.pgeola.2025.101112","DOIUrl":"10.1016/j.pgeola.2025.101112","url":null,"abstract":"<div><div>Dating the Mesozoic-aged fissure deposits around Bristol and South Wales has been problematic, with ages of the older examples disputed as either Carnian or Rhaetian, a 30-million-year difference. The deposits filling fissures at Holwell, Somerset offer a chance to establish a date for at least one system of fissures because they are on the coast of the Mendip Palaeoisland, close to bedded Rhaetian marine deposits. The Holwell fissures have been known since the 1850s when they yielded some of the first ever reported Mesozoic mammals, and they are the type locality for several fossil shark species, <em>Duffinselache holwellensis</em>, <em>Pseudocetorhinus pickfordi</em> and <em>Palaeobates reticulatus</em>. Bone-rich fissure fills from a neptunian dyke at Holwell yielded over 3000 identifiable specimens, comprising mainly marine fishes but also coastal-dwelling placodonts and terrestrially derived lepidosaurs that lived on the palaeoisland. Over 95 % of the fauna comprises four fish taxa that are typical of the bedded Westbury Formation. The less common <em>Rhomphaiodon minor</em> associated with abundant <em>Synechodus rhaeticus</em> indicates that the deposits are likely not basal but are within the upper half of the Westbury Formation. We hereby confirm that these Holwell fissure fill faunas, including the mammals, are of Rhaetian age.</div></div>","PeriodicalId":49672,"journal":{"name":"Proceedings of the Geologists Association","volume":"136 4","pages":"Article 101112"},"PeriodicalIF":1.2,"publicationDate":"2025-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144322890","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}
Pub Date : 2025-03-11DOI: 10.1016/j.pgeola.2025.101100
Roy E. Smith, David M. Martill
A new specimen of pterosaurian mandible from the Late Jurassic (Tithonian) Portland Limestone Group of southern England is described. Morphological considerations permit assignment to Pterodactyloidea. The elongate slender mandible and numerous closely spaced alveoli suggest it is a member of the Ctenochasmatidae. A faint median ridge on the occlusal surface between two grooves, converging into a median groove anteriorly, and the lack of a distinct premaxilla suggest the specimen is part of the symphysis of the mandible. This is the first documented record of a pterodactyloid from the Portland Group of England.
{"title":"A ctenochasmatid pterosaur from the Portland Limestone Formation (Late Jurassic, Tithonian) of southern England","authors":"Roy E. Smith, David M. Martill","doi":"10.1016/j.pgeola.2025.101100","DOIUrl":"10.1016/j.pgeola.2025.101100","url":null,"abstract":"<div><div>A new specimen of pterosaurian mandible from the Late Jurassic (Tithonian) Portland Limestone Group of southern England is described. Morphological considerations permit assignment to Pterodactyloidea. The elongate slender mandible and numerous closely spaced alveoli suggest it is a member of the Ctenochasmatidae. A faint median ridge on the occlusal surface between two grooves, converging into a median groove anteriorly, and the lack of a distinct premaxilla suggest the specimen is part of the symphysis of the mandible. This is the first documented record of a pterodactyloid from the Portland Group of England.</div></div>","PeriodicalId":49672,"journal":{"name":"Proceedings of the Geologists Association","volume":"136 4","pages":"Article 101100"},"PeriodicalIF":1.2,"publicationDate":"2025-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144322889","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}
Pub Date : 2025-03-06DOI: 10.1016/j.pgeola.2025.101099
Sofien Alyahyaoui, Hedi Zouari
The main objective of this study is to analyse the structure of the Neogene to Recent rocks in the surface and subsurface of northeastern Tunisia, in order to identify unconformities in outcrops and detect these tectonic and sedimentary events in the subsurface data.
An integrated study of multi-data supported by the compilation of new outcrop data, seismic reflection profiles, and data from petroleum wells has been carried out in order to determine the structural evolution in the study area. This study has resulted in an improved understanding of the geological evolution of NE Tunisia during the Neogene to Pleistocene. Four major unconformities have been identified in this area, the Tortonian unconformity, the Messinian unconformity, the Pliocene unconformity and the mid-Pleistocene unconformity.
The mapping of unconformities indicates their association with a major inversion event that occurred from the Late Miocene to the present, resulting in the development of stratigraphy controlled by structural factors. The analysis of nineteen seismic sections has confirmed the existence of several features associated with compressive and transpressive tectonic events.
These include reverse faults, folds, and unconformities. The structural mapping of these unconformities reveals the presence of a dominant fault system bounding a large number of moderate sized basins.
{"title":"New insights into Neogene to Pleistocene tectono-sedimentary major events in northeastern Tunisia from surface and subsurface data","authors":"Sofien Alyahyaoui, Hedi Zouari","doi":"10.1016/j.pgeola.2025.101099","DOIUrl":"10.1016/j.pgeola.2025.101099","url":null,"abstract":"<div><div>The main objective of this study is to analyse the structure of the Neogene to Recent rocks in the surface and subsurface of northeastern Tunisia, in order to identify unconformities in outcrops and detect these tectonic and sedimentary events in the subsurface data.</div><div>An integrated study of multi-data supported by the compilation of new outcrop data, seismic reflection profiles, and data from petroleum wells has been carried out in order to determine the structural evolution in the study area. This study has resulted in an improved understanding of the geological evolution of NE Tunisia during the Neogene to Pleistocene. Four major unconformities have been identified in this area, the Tortonian unconformity, the Messinian unconformity, the Pliocene unconformity and the mid-Pleistocene unconformity.</div><div>The mapping of unconformities indicates their association with a major inversion event that occurred from the Late Miocene to the present, resulting in the development of stratigraphy controlled by structural factors. The analysis of nineteen seismic sections has confirmed the existence of several features associated with compressive and transpressive tectonic events.</div><div>These include reverse faults, folds, and unconformities. The structural mapping of these unconformities reveals the presence of a dominant fault system bounding a large number of moderate sized basins.</div></div>","PeriodicalId":49672,"journal":{"name":"Proceedings of the Geologists Association","volume":"136 4","pages":"Article 101099"},"PeriodicalIF":1.2,"publicationDate":"2025-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144322888","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}
Pub Date : 2025-03-04DOI: 10.1016/j.pgeola.2025.101098
Nigel Banks
The Culham Brickworks was active from before 1850 for about 100 years and during its existence provided the only good exposure of the Early Cretaceous sub-Gault Formation unconformity in the Oxfordshire area of England. Six descriptions date from 1852 to 1926 detailing different sections as they were exposed in the ca. 350 m length of the excavations which moved gradually eastwards along the Thames riverbank. Over most of the excavated length the Gault Formation lies unconformably on the Late Jurassic Kimmeridge Clay Formation, but to the west the Aptian Lower Greensand Group intervenes and thickens to at least 4 m. A section described by John Phillips in 1860 has proved controversial, particularly for the claimed presence of 9 ft (2.7 m) of Kimmeridge Clay sands that were not seen by others. The earliest description is an unpublished manuscript from ca. 1852 by Daniel Sharpe containing previously unmentioned information, including a cross-section. This defines the Lower Greensand geometry more precisely and also throws additional doubt on Phillips' description. Using Sharpe's sections rather than Phillips', a cross-section has been drawn covering the entire length of the excavations. This illustrates significant relief at both the top of the Kimmeridge Clay Formation and the base of the Gault Formation. This reconstruction provides an essential starting point for any wider study of the Lower Greensand sandbody geometry and the nature of the sub-Gault Formation unconformity. The zonation of the Gault at the Brickworks continues to be reinterpreted, but the results are ambiguous.
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Pub Date : 2025-03-03DOI: 10.1016/j.pgeola.2025.101097
Iliass Naouadir , Samira Adil , El Hassane Chellai , Abdallah Elaaraj , Abdennabi Alitane , Mohammed Ettaki , Márton Veress , Ismail Naouadir
This article examines the caves of the Moroccan Middle Atlas using a multi-scale approach, both at the regional and outcrop levels. Our study employs a dual approach, combining numerical analysis and field observation, to investigate the formation of karst features. The results reveal a notable diversity in cave morphology, shaped by regional geological structures, tectonic activity, karstifiable carbonate substrate, pluvial climatic phases, and fluvial dynamics. Over 80 cave entrances have been identified and analysed in the El Menzel Causse, showing a correlation between their development and the main tectonic features of the region, including the North Middle Atlas Fault, the Median Middle Atlas Fault, and the fluvial network of the Sebou River. We suggest that the presence of these tectonic structures, along with allochthonous units linked to the uplift of the Middle Atlas, combined with Quaternary fluvial dynamics, played a central role in the karstogenesis of the El Menzel Causse caves. For the first time, a comparative study has been conducted between the karst processes of the Moroccan Atlas Mountains and those of the Dinaric Alps. This comparison highlights similarities between the karst phenomena of these two mountain ranges. Our comparative study deepens the understanding of karst processes in this specific region of Morocco, whilst providing valuable insights in comparison with other global karst systems, thereby contributing to the advancement of knowledge in karstology on an international scale.
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