Pub Date : 2024-05-05DOI: 10.1007/s00531-024-02408-8
Wolfgang Ruebsam, Lorenz Schwark
The Toarcian Oceanic Anoxic Event (T-OAE, Early Jurassic) is marked by widespread marine deoxygenation and deposition of organic carbon (OC)-rich strata. The genesis of the T-OAE is thought to be associated with environmental changes caused by the emission of 12C-enriched greenhouse gasses (CO2, CH4), manifested in a negative Toarcian carbon isotope excursion (nT-CIE). The nT-CIE is commonly used to stratigraphically define the T-OAE, and despite the complex interrelationship of the different environmental phenomena, both terms (nT-CIE and T-OAE) are commonly used interchangeable. We here demonstrate that occurrence of OC-rich strata is diachronous and not restricted to the nT-CIE, reflecting the interaction of global- and regional-scale processes. Thus, the interchangeable use of T-OAE and nT-CIE should be discarded. The nT-CIE, however, hosts the T-OAE climax, marked by the widest extent of OC-rich strata. Early Toarcian environmental changes, particularly sea level rise and rising temperatures, may have made marine areas more susceptible to develop oxygen deficient conditions, favoring OC-accumulation.
{"title":"Disparity between Toarcian Oceanic Anoxic Event and Toarcian carbon isotope excursion","authors":"Wolfgang Ruebsam, Lorenz Schwark","doi":"10.1007/s00531-024-02408-8","DOIUrl":"https://doi.org/10.1007/s00531-024-02408-8","url":null,"abstract":"<p>The Toarcian Oceanic Anoxic Event (T-OAE, Early Jurassic) is marked by widespread marine deoxygenation and deposition of organic carbon (OC)-rich strata. The genesis of the T-OAE is thought to be associated with environmental changes caused by the emission of <sup>12</sup>C-enriched greenhouse gasses (CO<sub>2</sub>, CH<sub>4</sub>), manifested in a negative Toarcian carbon isotope excursion (nT-CIE). The nT-CIE is commonly used to stratigraphically define the T-OAE, and despite the complex interrelationship of the different environmental phenomena, both terms (nT-CIE and T-OAE) are commonly used interchangeable. We here demonstrate that occurrence of OC-rich strata is diachronous and not restricted to the nT-CIE, reflecting the interaction of global- and regional-scale processes. Thus, the interchangeable use of T-OAE and nT-CIE should be discarded. The nT-CIE, however, hosts the T-OAE climax, marked by the widest extent of OC-rich strata. Early Toarcian environmental changes, particularly sea level rise and rising temperatures, may have made marine areas more susceptible to develop oxygen deficient conditions, favoring OC-accumulation.</p><h3 data-test=\"abstract-sub-heading\">Graphical abstract</h3>","PeriodicalId":13845,"journal":{"name":"International Journal of Earth Sciences","volume":"19 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140888534","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}
Pub Date : 2024-05-05DOI: 10.1007/s00531-024-02411-z
Jasemin Ayse Ölmez, Benjamin Busch, Christoph Hilgers
The Upper Cretaceous limestones unconformably overlie Upper Carboniferous coal-bearing lithologies and are studied to assess their effect on rising mine-water levels in the Ruhr mining district. Upper Cretaceous sedimentary rocks from the Münsterland Cretaceous Basin have previously been studied regarding their sedimentary structures and fossil content. However, understanding the petrophysical and petrographic heterogeneity in regard to sedimentary properties and their effect on fluid migration pathways is yet missing. Utilizing He-pycnometry, Klinkenberg-corrected air permeabilities, p-wave velocities, transmitted and reflected light analyses, point-counting and cathodoluminescence, we assess the petrophysical, geomechanical and mineralogical properties. Porosity ranges from 1.0 to 18.7% and permeability ranges from < 0.0001 to 0.2 mD, while p-wave velocity ranges between 2089 and 5843 m/s. Mechanical compaction leads to grain rearrangement, deformation of calcispheres, foraminifera and ductile clay mineral laminae. Above and below clay laminae, compaction bands of deformed calcispheres develop. Early diagenetic mineral precipitation of ferroan calcite in inter- and intragranular pores reduces porosity and permeability and influences geomechanical properties. An underestimated aspect of limestone petrography is the relationship of the original primary compactable depositional volume and the influence of compaction, deformation and cementation during early and late diagenesis on reservoir properties. The detrital dominated limestones show an originally high compactable depositional volume (CDV). Overall, reservoir qualities are poor and indicate the sealing potential of the studied lithologies. The Upper Cretaceous (Campanian) limestones thus may act as a barrier for increasing mine-water levels from dismantled, post-mining subsurface hard coal mines in the region.
{"title":"Reservoir quality of Upper Cretaceous limestones (Ahlen-Fm., Beckum Member, Münsterland Cretaceous Basin): effects of cementation and compaction on the compactable depositional volume","authors":"Jasemin Ayse Ölmez, Benjamin Busch, Christoph Hilgers","doi":"10.1007/s00531-024-02411-z","DOIUrl":"https://doi.org/10.1007/s00531-024-02411-z","url":null,"abstract":"<p>The Upper Cretaceous limestones unconformably overlie Upper Carboniferous coal-bearing lithologies and are studied to assess their effect on rising mine-water levels in the Ruhr mining district. Upper Cretaceous sedimentary rocks from the Münsterland Cretaceous Basin have previously been studied regarding their sedimentary structures and fossil content. However, understanding the petrophysical and petrographic heterogeneity in regard to sedimentary properties and their effect on fluid migration pathways is yet missing. Utilizing He-pycnometry, Klinkenberg-corrected air permeabilities, p-wave velocities, transmitted and reflected light analyses, point-counting and cathodoluminescence, we assess the petrophysical, geomechanical and mineralogical properties. Porosity ranges from 1.0 to 18.7% and permeability ranges from < 0.0001 to 0.2 mD, while p-wave velocity ranges between 2089 and 5843 m/s. Mechanical compaction leads to grain rearrangement, deformation of calcispheres, foraminifera and ductile clay mineral laminae. Above and below clay laminae, compaction bands of deformed calcispheres develop. Early diagenetic mineral precipitation of ferroan calcite in inter- and intragranular pores reduces porosity and permeability and influences geomechanical properties. An underestimated aspect of limestone petrography is the relationship of the original primary compactable depositional volume and the influence of compaction, deformation and cementation during early and late diagenesis on reservoir properties. The detrital dominated limestones show an originally high compactable depositional volume (CDV). Overall, reservoir qualities are poor and indicate the sealing potential of the studied lithologies. The Upper Cretaceous (Campanian) limestones thus may act as a barrier for increasing mine-water levels from dismantled, post-mining subsurface hard coal mines in the region.</p><h3 data-test=\"abstract-sub-heading\">Graphical abstract</h3>\u0000","PeriodicalId":13845,"journal":{"name":"International Journal of Earth Sciences","volume":"238 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140888744","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}
This paper summarizes the most important results and conclusions derived from organic geochemical investigations performed on the Miocene Aleksinac oil shale (Serbia) during the last 60 years. The Aleksinac oil shale is one of the richest and most studied European oil shale deposits. This paper is divided into four sections. The first section includes data from Rock-Eval pyrolysis, organic petrography, and biomarkers of outcrop samples, as well as samples taken from two layers (upper and lower), drilled from the well BD-4. The results consistently indicated that the Aleksinac oil shale contains immature, mostly algal-derived organic matter (kerogen types I and II), deposited in reducing brackish to freshwater environment. However, certain differences were observed between the upper and lower oil shale sequences in the well BD-4, which resulted in two times higher source potential index in the upper layer. The Aleksinac oil shale has been used as a model substance in numerous organic geochemical studies. The second section of the review paper describes how a standard procedure for determination of kerogen chemical structure (controlled gradual degradation of kerogen by an alkaline permanganate solution) is established, which was developed using the Aleksinac oil shale as a substrate. This oil shale was also used as a model substance to investigate the influences of native minerals on the thermal changes of bitumen and kerogen in sediments, and this process is described in the third section of the paper. In the final section, studies (performed on the Aleksinac oil shale) related to the influence of the pyrolysis type and variations of kerogen type on the yield and composition of liquid pyrolysis products are presented.
{"title":"Organic geochemical study of Aleksinac oil shale","authors":"Branimir Jovančićević, Ksenija Stojanović, Dragana Životić","doi":"10.1007/s00531-024-02413-x","DOIUrl":"https://doi.org/10.1007/s00531-024-02413-x","url":null,"abstract":"<p>This paper summarizes the most important results and conclusions derived from organic geochemical investigations performed on the Miocene Aleksinac oil shale (Serbia) during the last 60 years. The Aleksinac oil shale is one of the richest and most studied European oil shale deposits. This paper is divided into four sections. The first section includes data from Rock-Eval pyrolysis, organic petrography, and biomarkers of outcrop samples, as well as samples taken from two layers (upper and lower), drilled from the well BD-4. The results consistently indicated that the Aleksinac oil shale contains immature, mostly algal-derived organic matter (kerogen types I and II), deposited in reducing brackish to freshwater environment. However, certain differences were observed between the upper and lower oil shale sequences in the well BD-4, which resulted in two times higher source potential index in the upper layer. The Aleksinac oil shale has been used as a model substance in numerous organic geochemical studies. The second section of the review paper describes how a standard procedure for determination of kerogen chemical structure (controlled gradual degradation of kerogen by an alkaline permanganate solution) is established, which was developed using the Aleksinac oil shale as a substrate. This oil shale was also used as a model substance to investigate the influences of native minerals on the thermal changes of bitumen and kerogen in sediments, and this process is described in the third section of the paper. In the final section, studies (performed on the Aleksinac oil shale) related to the influence of the pyrolysis type and variations of kerogen type on the yield and composition of liquid pyrolysis products are presented.</p><h3 data-test=\"abstract-sub-heading\">Graphical abstract</h3>","PeriodicalId":13845,"journal":{"name":"International Journal of Earth Sciences","volume":"55 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140889921","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}
Pub Date : 2024-04-30DOI: 10.1007/s00531-024-02410-0
A. Petroccia, R. Carosi, C. Montomoli, S. Iaccarino, J. B. Forshaw, M. Petrelli
This work presents an integrated structural, kinematic, and petrochronological study of the Monte Grighini dome within the Variscan hinterland–foreland transition zone of Sardinia (Italy). The area is characterised by dextral transpressive deformation partitioned into low- and high-strain zones (Monte Grighini shear zone, MGSZ). Geothermobarometry of one sample of sillimanite-bearing mylonitic metapelite indicates that the Monte Grighini shear zone developed under high-temperature (~ 625 °C) and low-pressure (~ 0.4–0.6 GPa) conditions. In situ U–(Th)–Pb monazite geochronology reveals that the deformation in the shear zone initiated at ca. 315 Ma. Although previous studies have interpreted the Monte Grighini shear zone to have formed in a transtensional regime, our structural and kinematic results integrated with constraints on the relative timing of deformation indicate that it shows similarities with other dextral ductile transpressive shear zones in the Southern European Variscan belt (i.e., the East Variscan Shear Zone, EVSZ). However, dextral transpression in the Monte Grighini shear zone started later than in other portions of the EVSZ within the framework of the Southern European Variscan Belt due to the progressive migration and rejuvenation of deformation from the core to the external sectors of the belt.
{"title":"Transtension or transpression? Tectono-metamorphic constraints on the formation of the Monte Grighini dome (Sardinia, Italy) and implications for the Southern European Variscan belt","authors":"A. Petroccia, R. Carosi, C. Montomoli, S. Iaccarino, J. B. Forshaw, M. Petrelli","doi":"10.1007/s00531-024-02410-0","DOIUrl":"https://doi.org/10.1007/s00531-024-02410-0","url":null,"abstract":"<p>This work presents an integrated structural, kinematic, and petrochronological study of the Monte Grighini dome within the Variscan hinterland–foreland transition zone of Sardinia (Italy). The area is characterised by dextral transpressive deformation partitioned into low- and high-strain zones (Monte Grighini shear zone, MGSZ). Geothermobarometry of one sample of sillimanite-bearing mylonitic metapelite indicates that the Monte Grighini shear zone developed under high-temperature (~ 625 °C) and low-pressure (~ 0.4–0.6 GPa) conditions. In situ U–(Th)–Pb monazite geochronology reveals that the deformation in the shear zone initiated at ca. 315 Ma. Although previous studies have interpreted the Monte Grighini shear zone to have formed in a transtensional regime, our structural and kinematic results integrated with constraints on the relative timing of deformation indicate that it shows similarities with other dextral ductile transpressive shear zones in the Southern European Variscan belt (i.e., the East Variscan Shear Zone, EVSZ). However, dextral transpression in the Monte Grighini shear zone started later than in other portions of the EVSZ within the framework of the Southern European Variscan Belt due to the progressive migration and rejuvenation of deformation from the core to the external sectors of the belt.</p><h3 data-test=\"abstract-sub-heading\">Graphical abstract</h3>","PeriodicalId":13845,"journal":{"name":"International Journal of Earth Sciences","volume":"49 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140841261","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}
Pub Date : 2024-04-27DOI: 10.1007/s00531-024-02409-7
Attila J. Trájer
The Pannonian mega-yardang system is the northernmost mega-yardang field in Europe, exerting a profound influence on the relief and surface hydrographic structure of Western Hungary. Despite its significance, the precise timing and climatic conditions under which this mega-yardang system formed remain elusive. The geological setting was studied, the former humidity and biome patterns were modelled, the climatically analogous regions of the past climates of the region were identified, and the Köppen Aridity Indices of the region were compared to the aridity values of other yardang fields from five continents in the last 3.3 mys. The geological structure of the yardangs suggests an origin post-dating the Tortonian period but preceding the mid-Pleistocene era. In the Zanclean and in the warmer periods of the Piacenzian, the studied region had humid subtropical climatic conditions that were not suitable for the formation of large-scale aeolian landforms. Similarly, in the Quaternary period, the climate varied between boreal and humid continental, which was not conducive to the formation of mega-yardang fields. Cold semi-arid climatic conditions only existed in the mid-Pliocene cold period and perhaps at the transition of the Pliocene to the Pleistocene. This paleoclimatic hypothesis is in accordance with the Pliocene fossil record of the region, which contains the remains of such arid habitat-dwelling fauna elements as camelids and struthionids. The comparison of the development of Köppen Aridity Indices among yardangs in other territories also suggests that the Pannonian mega-yardang system may have formed around the transition of the Neogene to the Quaternary epochs.
{"title":"Age and environmental conditions for the formation of the Pannonian mega-yardang system","authors":"Attila J. Trájer","doi":"10.1007/s00531-024-02409-7","DOIUrl":"https://doi.org/10.1007/s00531-024-02409-7","url":null,"abstract":"<p>The Pannonian mega-yardang system is the northernmost mega-yardang field in Europe, exerting a profound influence on the relief and surface hydrographic structure of Western Hungary. Despite its significance, the precise timing and climatic conditions under which this mega-yardang system formed remain elusive. The geological setting was studied, the former humidity and biome patterns were modelled, the climatically analogous regions of the past climates of the region were identified, and the Köppen Aridity Indices of the region were compared to the aridity values of other yardang fields from five continents in the last 3.3 mys. The geological structure of the yardangs suggests an origin post-dating the Tortonian period but preceding the mid-Pleistocene era. In the Zanclean and in the warmer periods of the Piacenzian, the studied region had humid subtropical climatic conditions that were not suitable for the formation of large-scale aeolian landforms. Similarly, in the Quaternary period, the climate varied between boreal and humid continental, which was not conducive to the formation of mega-yardang fields. Cold semi-arid climatic conditions only existed in the mid-Pliocene cold period and perhaps at the transition of the Pliocene to the Pleistocene. This paleoclimatic hypothesis is in accordance with the Pliocene fossil record of the region, which contains the remains of such arid habitat-dwelling fauna elements as camelids and struthionids. The comparison of the development of Köppen Aridity Indices among yardangs in other territories also suggests that the Pannonian mega-yardang system may have formed around the transition of the Neogene to the Quaternary epochs.</p><h3 data-test=\"abstract-sub-heading\">Graphical abstract</h3>","PeriodicalId":13845,"journal":{"name":"International Journal of Earth Sciences","volume":"33 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140812741","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}
Pub Date : 2024-04-26DOI: 10.1007/s00531-024-02412-y
Matheus Ariel Battisti, Jiří Konopásek, Maria de Fátima Bitencourt, Jiří Sláma, Jack James Percival, Giuseppe Betino De Toni, Stephanie Carvalho da Silva, Elisa Oliveira da Costa, Jakub Trubač
The Dom Feliciano Belt is the South American part of an extensive Neoproterozoic orogenic system that developed during the late Cryogenian–early Cambrian close to the margin of southwest Gondwana. The link of its evolution with the tectonic processes in its African counterpart is still not well understood. P–T estimates, Lu–Hf garnet–whole-rock ages, U–Pb monazite SIMS ages and REE garnet and monazite data from samples of the Porongos and Passo Feio complexes indicate diachronous tectonic evolution of the central Dom Feliciano Belt foreland. Metasedimentary rocks of the eastern Porongos Complex reached previously estimated metamorphic peak conditions of ~ 560–580 °C and 5.8–6.3 kbar at 654 ± 2 Ma, based on Lu–Hf isochron garnet–whole-rock age data. This episode represents an early orogenic thickening in the foreland as a response to the beginning of the transpressive convergent evolution of the belt. The monazite age of 614 ± 6 Ma (U–Pb SIMS) is interpreted as associated with post-exhumation magmatic activity in the foreland and suggests that the eastern Porongos Complex was exhumed sometime between ca. 660 and 615 Ma. The main metamorphic and deformation event in the Porongos Complex’s western region occurred at ~ 545–565 °C and 4.3–5.3 kbar at 563 ± 1 Ma (garnet–whole-rock Lu–Hf isochron age). The exhumation of this part of the foreland is dated using monazite crystallising during garnet breakdown and suggests retrograde metamorphism at 541 ± 7 Ma (U–Pb SIMS). The main metamorphic fabric in the Passo Feio Complex further to the west developed at 571 ± 2 Ma (garnet–whole-rock Lu–Hf isochron age) at 560–580 °C and 4.7–6.4 kbar. The western part of the Porongos Complex and the Passo Feio Complex have deformed at similar P–T conditions and apparent geothermal gradients at ca. 570–565 Ma. These regions record a second crustal thickening event in the Dom Feliciano Belt foreland and the orogenic front migration towards the west as a response to the onset of crustal thickening on the African side of this long-lived transpressive orogenic system.
{"title":"Petrochronology of the Dom Feliciano Belt foreland in southernmost Brazil reveals two distinct tectonometamorphic events in the western central Kaoko–Dom Feliciano–Gariep orogen","authors":"Matheus Ariel Battisti, Jiří Konopásek, Maria de Fátima Bitencourt, Jiří Sláma, Jack James Percival, Giuseppe Betino De Toni, Stephanie Carvalho da Silva, Elisa Oliveira da Costa, Jakub Trubač","doi":"10.1007/s00531-024-02412-y","DOIUrl":"https://doi.org/10.1007/s00531-024-02412-y","url":null,"abstract":"<p>The Dom Feliciano Belt is the South American part of an extensive Neoproterozoic orogenic system that developed during the late Cryogenian–early Cambrian close to the margin of southwest Gondwana. The link of its evolution with the tectonic processes in its African counterpart is still not well understood. <i>P–T</i> estimates, Lu–Hf garnet–whole-rock ages, U–Pb monazite SIMS ages and REE garnet and monazite data from samples of the Porongos and Passo Feio complexes indicate diachronous tectonic evolution of the central Dom Feliciano Belt foreland. Metasedimentary rocks of the eastern Porongos Complex reached previously estimated metamorphic peak conditions of ~ 560–580 °C and 5.8–6.3 kbar at 654 ± 2 Ma, based on Lu–Hf isochron garnet–whole-rock age data. This episode represents an early orogenic thickening in the foreland as a response to the beginning of the transpressive convergent evolution of the belt. The monazite age of 614 ± 6 Ma (U–Pb SIMS) is interpreted as associated with post-exhumation magmatic activity in the foreland and suggests that the eastern Porongos Complex was exhumed sometime between ca. 660 and 615 Ma. The main metamorphic and deformation event in the Porongos Complex’s western region occurred at ~ 545–565 °C and 4.3–5.3 kbar at 563 ± 1 Ma (garnet–whole-rock Lu–Hf isochron age). The exhumation of this part of the foreland is dated using monazite crystallising during garnet breakdown and suggests retrograde metamorphism at 541 ± 7 Ma (U–Pb SIMS). The main metamorphic fabric in the Passo Feio Complex further to the west developed at 571 ± 2 Ma (garnet–whole-rock Lu–Hf isochron age) at 560–580 °C and 4.7–6.4 kbar. The western part of the Porongos Complex and the Passo Feio Complex have deformed at similar <i>P–T</i> conditions and apparent geothermal gradients at ca. 570–565 Ma. These regions record a second crustal thickening event in the Dom Feliciano Belt foreland and the orogenic front migration towards the west as a response to the onset of crustal thickening on the African side of this long-lived transpressive orogenic system.</p><h3 data-test=\"abstract-sub-heading\">Graphical abstract</h3>\u0000","PeriodicalId":13845,"journal":{"name":"International Journal of Earth Sciences","volume":"50 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140798970","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}
The Precambrian terranes of the Eastern Indian Shield (EIS) comprise the Bundelkhand, Singhbhum, and Bastar cratons with intervening Proterozoic mobile belts such as Central Indian Tectonic Zone, Eastern Ghats Mobile Belt, Singhbhum Mobile Belt and Chotanagpur Granite Gneissic Complex; and the Proterozoic Mahanadi Rift, Chhattisgarh and Vindhyan Basins, with significant coverage of Indo-Gangetic Plain sediments in the northern part. This study presents the results of a seismically well-constrained 2-D multi-scale potential field modelling to delineate the lithosphere structure across different Precambrian terranes of the EIS. The joint interpretation of the potential field data reveals that (i) the mobile belts are bounded by the deep crustal faults with denser crust, (ii) presence of thick underplated crust below Singhbhum Craton, Singhbhum Mobile Belt, Chotanagpur Granite Gneissic Complex and the surrounding rift basin, (iii) localised Moho upwarp at a depth of ~ 36–37 km below the Proterozoic basins, and (iv) the Lithosphere-Asthenosphere Boundary (LAB) varying between 90 and 200 km below the EIS region. The distinct crustal structure and deeper LAB (130–200 km) below the mobile belts suggest the Proterozoic amalgamation and lithosphere reworking. Below the Singhbhum Craton, the LAB is observed at a depth of ~ 145–155 km, which is comparatively thinner than other cratonic areas elsewhere. The observed crustal underplating and the thinner LAB below the Singhbhum Craton indicate that the lithospheric erosion and magmatic upwelling was caused by the major Paleo-Mesoproterozoic and Early-Cretaceous large igneous province events.
Graphical abstract
东印度地盾（EIS）的前寒武纪地形包括邦德尔坎德邦、辛布姆和巴斯塔火山口，其间有新生代移动带，如中印度构造带、东高地移动带、辛布姆移动带和乔塔纳布尔花岗片麻岩群；以及新生代的马哈纳迪裂谷、恰蒂斯加尔和温迪亚盆地，北部有大量印度-甘肃平原沉积物。本研究介绍了地震约束良好的二维多尺度势场建模结果，以划分 EIS 不同前寒武纪地层的岩石圈结构。对势场数据的联合解释显示：(i) 移动带以地壳密度较高的深部地壳断层为界；(ii) 辛格布姆克拉通、辛格布姆移动带下方存在厚的下伏地壳、(iii)新生代盆地下方约 36-37 公里处的局部莫霍上升带，以及(iv)岩石圈-热成层边界（LAB）在 EIS 地区下方 90 至 200 公里处。移动带下方明显的地壳结构和更深的岩石圈-大气圈边界（130-200 公里）表明，新生代曾发生过混杂和岩石圈再加工。在辛格布姆克拉通以下，观察到的岩石圈深度约为 145-155 千米，比其他地方的克拉通地区要薄。在辛格布姆克拉通以下观察到的地壳下伏和较薄的岩石圈表明，岩石圈侵蚀和岩浆上涌是由古中生代和早白垩世大型火成岩带事件引起的。
{"title":"Evidence of lithosphere erosion in the Eastern Indian shield from multi-scale potential field modelling: geodynamic implications","authors":"Sumanta Kumar Sathapathy, Yellalacheruvu Giri, Munukutla Radhakrishna","doi":"10.1007/s00531-024-02416-8","DOIUrl":"https://doi.org/10.1007/s00531-024-02416-8","url":null,"abstract":"<p>The Precambrian terranes of the Eastern Indian Shield (EIS) comprise the Bundelkhand, Singhbhum, and Bastar cratons with intervening Proterozoic mobile belts such as Central Indian Tectonic Zone, Eastern Ghats Mobile Belt, Singhbhum Mobile Belt and Chotanagpur Granite Gneissic Complex; and the Proterozoic Mahanadi Rift, Chhattisgarh and Vindhyan Basins, with significant coverage of Indo-Gangetic Plain sediments in the northern part. This study presents the results of a seismically well-constrained 2-D multi-scale potential field modelling to delineate the lithosphere structure across different Precambrian terranes of the EIS. The joint interpretation of the potential field data reveals that (i) the mobile belts are bounded by the deep crustal faults with denser crust, (ii) presence of thick underplated crust below Singhbhum Craton, Singhbhum Mobile Belt, Chotanagpur Granite Gneissic Complex and the surrounding rift basin, (iii) localised Moho upwarp at a depth of ~ 36–37 km below the Proterozoic basins, and (iv) the Lithosphere-Asthenosphere Boundary (LAB) varying between 90 and 200 km below the EIS region. The distinct crustal structure and deeper LAB (130–200 km) below the mobile belts suggest the Proterozoic amalgamation and lithosphere reworking. Below the Singhbhum Craton, the LAB is observed at a depth of ~ 145–155 km, which is comparatively thinner than other cratonic areas elsewhere. The observed crustal underplating and the thinner LAB below the Singhbhum Craton indicate that the lithospheric erosion and magmatic upwelling was caused by the major Paleo-Mesoproterozoic and Early-Cretaceous large igneous province events.</p><h3 data-test=\"abstract-sub-heading\">Graphical abstract</h3>","PeriodicalId":13845,"journal":{"name":"International Journal of Earth Sciences","volume":"5 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140636826","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}
Pub Date : 2024-04-20DOI: 10.1007/s00531-024-02395-w
Fatma A. Mousa, Mohamed M. Abu El-Hassan, Emad S. Sallam
{"title":"Terminal Holocene palaeolake mud pans (playas) of Farafra Oasis, Western Desert, Egypt: palaeoenvironmental and palaeoclimatic implications","authors":"Fatma A. Mousa, Mohamed M. Abu El-Hassan, Emad S. Sallam","doi":"10.1007/s00531-024-02395-w","DOIUrl":"https://doi.org/10.1007/s00531-024-02395-w","url":null,"abstract":"","PeriodicalId":13845,"journal":{"name":"International Journal of Earth Sciences","volume":"63 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140623988","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}
Pub Date : 2024-04-19DOI: 10.1007/s00531-024-02403-z
Fabian Dellefant, Lina Seybold, Claudia A. Trepmann, Stuart A. Gilder, Iuliia V. Sleptsova, Stefan Hölzl, Melanie Kaliwoda
In the Aumühle quarry of the Ries impact structure, moderately shocked clasts from the Variscan basement occur sandwiched between overlying suevite and components derived from the Mesozoic sedimentary cover of the underlying Bunte Breccia without distinct shock effects. We analyzed the clasts by optical microscopy, scanning electron microscopy (SEM/EDS/EBSD), and Raman spectroscopy to unravel their emplacement relation to the overlying suevite and the sediment-rock clasts of the Bunte Breccia. Clasts sizes range up to few decimeters and are embedded in a fine-grained lithic matrix; no impact-melt fragments are observed. Amphibolite clasts contain maskelynite with few lamellar remnants of feldspar, indicating shock pressures of 28–34 GPa. Amphiboles have cleavage fractures and ((overline{1})01) mechanical twins suggesting differential stresses > 400 MPa. Felsic gneiss components have optically isotropic SiO2 indicative of shock pressures ≈35 GPa. Metagranite cataclasite clasts contain shocked calcite aggregates and quartz with a high density of fine rhombohedral planar deformation features indicating shock pressures ≈20 GPa. The moderately shocked basement clasts originate from deeper levels of the transient cavity and lower radial distance to the center of the structure compared to the sediment-rock clasts. Both were ballistically ejected during crater excavation. In accordance with palaeo- and rock magnetic data, they were mixed during turbulent deposition at the top of the Bunte Breccia before the emplacement of suevite. The high amount of basement clasts below suevite and on top of the underlying Bunte Breccia is consistent with the commonly reported inverse stratigraphy in the Ries impact structure.
{"title":"Emplacement of shocked basement clasts during crater excavation in the Ries impact structure","authors":"Fabian Dellefant, Lina Seybold, Claudia A. Trepmann, Stuart A. Gilder, Iuliia V. Sleptsova, Stefan Hölzl, Melanie Kaliwoda","doi":"10.1007/s00531-024-02403-z","DOIUrl":"https://doi.org/10.1007/s00531-024-02403-z","url":null,"abstract":"<p>In the Aumühle quarry of the Ries impact structure, moderately shocked clasts from the Variscan basement occur sandwiched between overlying suevite and components derived from the Mesozoic sedimentary cover of the underlying Bunte Breccia without distinct shock effects. We analyzed the clasts by optical microscopy, scanning electron microscopy (SEM/EDS/EBSD), and Raman spectroscopy to unravel their emplacement relation to the overlying suevite and the sediment-rock clasts of the Bunte Breccia. Clasts sizes range up to few decimeters and are embedded in a fine-grained lithic matrix; no impact-melt fragments are observed. Amphibolite clasts contain maskelynite with few lamellar remnants of feldspar, indicating shock pressures of 28–34 GPa. Amphiboles have cleavage fractures and (<span>(overline{1})</span>01) mechanical twins suggesting differential stresses > 400 MPa. Felsic gneiss components have optically isotropic SiO<sub>2</sub> indicative of shock pressures ≈35 GPa. Metagranite cataclasite clasts contain shocked calcite aggregates and quartz with a high density of fine rhombohedral planar deformation features indicating shock pressures ≈20 GPa. The moderately shocked basement clasts originate from deeper levels of the transient cavity and lower radial distance to the center of the structure compared to the sediment-rock clasts. Both were ballistically ejected during crater excavation. In accordance with palaeo- and rock magnetic data, they were mixed during turbulent deposition at the top of the Bunte Breccia before the emplacement of suevite. The high amount of basement clasts below suevite and on top of the underlying Bunte Breccia is consistent with the commonly reported inverse stratigraphy in the Ries impact structure.</p><h3 data-test=\"abstract-sub-heading\">Graphical Abstract</h3>\u0000","PeriodicalId":13845,"journal":{"name":"International Journal of Earth Sciences","volume":"1 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140623874","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}
Pub Date : 2024-04-18DOI: 10.1007/s00531-024-02405-x
Ashraf M. Al-Nashar, Nabil A. Abdel Hafez, Mohamed W. Abd El-Moghny, Ahmed Awad, Sherif Farouk, Haitham M. Ayyad
The depositional ages and provenance of the Paleozoic Araba and Naqus Formations along the northern Gondwanan margin in Egypt have remained uncertain due to a lack of index fossils. Resolving this issue is crucial for understanding regional geology during deposition and subsequent tectonic development. We integrate detailed facies analysis, anisotropy of magnetic susceptibility (AMS), paleomagnetism, and mineralogical data to elucidate the genesis and depositional ages of the Araba and Naqus Formations. Petrographic analyses identified seven distinct facies types, providing insights into sedimentary textures, maturity, and sources, with contributions from igneous and metamorphic sources indicated by heavy minerals. X-ray diffraction (XRD) analysis identified accessory minerals such as quartz, goethite, kaolinite, hematite, and anatase. Paleomagnetism isolated two magnetic components (CA and CN) providing the first robust paleo pole positions at Lat. = 70.8° N, Long. = 308.2° E and Lat. = 37.8° N, Long. = 233.1° E, indicating Cambrian and Carboniferous ages for the Araba and Naqus formations, respectively. Thermal demagnetization constrained these dates using established polarity timescales. Mineralogical data indicated that the Araba Formation originated from an igneous source, while the Naqus Formation had a mixed metamorphic-igneous provenance. The integrated AMS and paleomagnetic data reveal evidence of post-depositional deformation. Specifically, the clustering of maximum AMS axes in the NW–SE direction for both formations, suggests the initial presence of a primary depositional fabric. However, prevalent tectonic activity during the Cenozoic appears to have overprinted and modified this fabric through deformation related to rifting of the Gulf of Suez region. Through this novel multi-proxy approach, we have resolved long-standing uncertainties regarding the formations' depositional ages. Our study thereby provides the first chronostratigraphic framework for these strategically important sedimentary units, significantly advancing understanding of regional Paleozoic geology.
{"title":"Integrating facies, mineralogy, and paleomagnetism to constrain the age and provenance of Paleozoic siliciclastic sedimentary rocks along the northern Gondwana margin: insights from the Araba and Naqus formations in western Gulf of Suez, Egypt","authors":"Ashraf M. Al-Nashar, Nabil A. Abdel Hafez, Mohamed W. Abd El-Moghny, Ahmed Awad, Sherif Farouk, Haitham M. Ayyad","doi":"10.1007/s00531-024-02405-x","DOIUrl":"https://doi.org/10.1007/s00531-024-02405-x","url":null,"abstract":"<p>The depositional ages and provenance of the Paleozoic Araba and Naqus Formations along the northern Gondwanan margin in Egypt have remained uncertain due to a lack of index fossils. Resolving this issue is crucial for understanding regional geology during deposition and subsequent tectonic development. We integrate detailed facies analysis, anisotropy of magnetic susceptibility (AMS), paleomagnetism, and mineralogical data to elucidate the genesis and depositional ages of the Araba and Naqus Formations. Petrographic analyses identified seven distinct facies types, providing insights into sedimentary textures, maturity, and sources, with contributions from igneous and metamorphic sources indicated by heavy minerals. X-ray diffraction (XRD) analysis identified accessory minerals such as quartz, goethite, kaolinite, hematite, and anatase. Paleomagnetism isolated two magnetic components (<i>C</i><sub>A</sub> and <i>C</i><sub>N</sub>) providing the first robust paleo pole positions at Lat. = 70.8° N, Long. = 308.2° E and Lat. = 37.8° N, Long. = 233.1° E, indicating Cambrian and Carboniferous ages for the Araba and Naqus formations, respectively. Thermal demagnetization constrained these dates using established polarity timescales. Mineralogical data indicated that the Araba Formation originated from an igneous source, while the Naqus Formation had a mixed metamorphic-igneous provenance. The integrated AMS and paleomagnetic data reveal evidence of post-depositional deformation. Specifically, the clustering of maximum AMS axes in the NW–SE direction for both formations, suggests the initial presence of a primary depositional fabric. However, prevalent tectonic activity during the Cenozoic appears to have overprinted and modified this fabric through deformation related to rifting of the Gulf of Suez region. Through this novel multi-proxy approach, we have resolved long-standing uncertainties regarding the formations' depositional ages. Our study thereby provides the first chronostratigraphic framework for these strategically important sedimentary units, significantly advancing understanding of regional Paleozoic geology.</p><h3 data-test=\"abstract-sub-heading\">Graphical abstract</h3>","PeriodicalId":13845,"journal":{"name":"International Journal of Earth Sciences","volume":"38 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140612382","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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