Pub Date : 2025-01-01DOI: 10.1016/j.eve.2025.100066
Igor M. Venancio , João M. Ballalai , Douglas V.O. Lessa , Thiago S. Figueiredo , Raissa Tayt-Sohn , Marianna C. Motta , Aurélio F. Silva , Nathalia O. de Lima , Beatriz C.O.D.S.S. da Silva , Rut Díaz , Manuel Moreira , Anderson G. de Almeida , Ana Luiza S. Albuquerque
Oceanic circulation changes play a fundamental role in shaping past climate variability in northeastern Brazil, influencing precipitation patterns and sediment transport on glacial-interglacial and millennial timescales. However, the extent to which these processes vary across different water depths and their geochemical imprints in marine sediments remain poorly constrained. Here, we present multiproxy geochemical records from three sediment cores in the Sergipe Basin, located off northeastern Brazil, spanning the last 45,000 years. Variations in Fe/Ca, Zr/Rb, TOC, CaCO3, and sulfur content reveal distinct glacial-interglacial shifts, with enhanced terrigenous input and reduced carbonate deposition during glacials, likely linked to lower sea level and changes in ocean circulation. Millennial-scale fluctuations in sulfur and Zr/Rb suggest variations in deep-water ventilation and bottom-current speed. These results provide new insights into the regional paleoceanographic evolution of the western South Atlantic and reinforce mechanisms driving sedimentary responses to past climate variability.
{"title":"Glacial-interglacial and millennial-scale changes in terrigenous supply and ocean circulation in the western South Atlantic","authors":"Igor M. Venancio , João M. Ballalai , Douglas V.O. Lessa , Thiago S. Figueiredo , Raissa Tayt-Sohn , Marianna C. Motta , Aurélio F. Silva , Nathalia O. de Lima , Beatriz C.O.D.S.S. da Silva , Rut Díaz , Manuel Moreira , Anderson G. de Almeida , Ana Luiza S. Albuquerque","doi":"10.1016/j.eve.2025.100066","DOIUrl":"10.1016/j.eve.2025.100066","url":null,"abstract":"<div><div>Oceanic circulation changes play a fundamental role in shaping past climate variability in northeastern Brazil, influencing precipitation patterns and sediment transport on glacial-interglacial and millennial timescales. However, the extent to which these processes vary across different water depths and their geochemical imprints in marine sediments remain poorly constrained. Here, we present multiproxy geochemical records from three sediment cores in the Sergipe Basin, located off northeastern Brazil, spanning the last 45,000 years. Variations in Fe/Ca, Zr/Rb, TOC, CaCO<sub>3</sub>, and sulfur content reveal distinct glacial-interglacial shifts, with enhanced terrigenous input and reduced carbonate deposition during glacials, likely linked to lower sea level and changes in ocean circulation. Millennial-scale fluctuations in sulfur and Zr/Rb suggest variations in deep-water ventilation and bottom-current speed. These results provide new insights into the regional paleoceanographic evolution of the western South Atlantic and reinforce mechanisms driving sedimentary responses to past climate variability.</div></div>","PeriodicalId":100516,"journal":{"name":"Evolving Earth","volume":"3 ","pages":"Article 100066"},"PeriodicalIF":0.0,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143808342","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Reconstructing the sedimentary environment and comprehension of the process of mineral enrichment rely significantly on lithofacies, which can be considered a proxy for the paleoenvironment. This study investigates the lithostratigraphic characteristics of the Late Cretaceous to Early Paleocene period, spanning the pivotal Cretaceous-Paleogene (K-Pg) boundary, in the Mannar Basin. Utilizing 25 drill cutting samples from the Dorado exploration well at intervals of 10 m, ranging from 2800 m to 3040 m in depth, various lithofacies were identified using Scanning Electron Microscope (SEM), polarizing microscope, and X-ray diffraction (XRD) analysis. Petrographic examinations revealed a diverse mineral arrangement, ranging from very fine to coarse-grained textures. Dominant minerals identified through XRD analysis include Quartz, Feldspar, Carbonate, and various clay minerals, facilitating shale classification. Five distinct lithofacies were delineated, encompassing calcareous, clayey, calcareous siliceous mixed, calcareous clayey mixed shales, and siliceous rocks. Noteworthy mineralogical compositions include abundant kaolinite, chlorite, and hematite minerals in the Maastrichtian succession, transitioning to montmorillonite, illite, and pyrite dominance in the Early Maastrichtian succession. Through clay mineralogy, this study discerns significant shifts in paleoenvironmental conditions, ranging from anoxic, arid to semi-arid climates during the Campanian to warm/wet, oxidizing environments during Maastrichtian, and finally to arid/semi-arid conditions during the early Paleocene. Additionally, evidence of early burial diagenesis and Late Maastrichtian sea-level regression is identified, contributing to a comprehensive understanding of environmental dynamics during this critical geological period in the Mannar Basin in the Equatorial Margin of the Northern Indian Ocean.
{"title":"Unravelling paleoenvironmental dynamics across the cretaceous-paleogene (K-Pg) boundary in the offshore Mannar Basin of the Northern Indian Ocean","authors":"S.S. Nawarathna , P.L. Dharmapriya , A.U. Wijenayake , E.K.C.W. Kularathna","doi":"10.1016/j.eve.2025.100062","DOIUrl":"10.1016/j.eve.2025.100062","url":null,"abstract":"<div><div>Reconstructing the sedimentary environment and comprehension of the process of mineral enrichment rely significantly on lithofacies, which can be considered a proxy for the paleoenvironment. This study investigates the lithostratigraphic characteristics of the Late Cretaceous to Early Paleocene period, spanning the pivotal Cretaceous-Paleogene (K-Pg) boundary, in the Mannar Basin. Utilizing 25 drill cutting samples from the Dorado exploration well at intervals of 10 m, ranging from 2800 m to 3040 m in depth, various lithofacies were identified using Scanning Electron Microscope (SEM), polarizing microscope, and X-ray diffraction (XRD) analysis. Petrographic examinations revealed a diverse mineral arrangement, ranging from very fine to coarse-grained textures. Dominant minerals identified through XRD analysis include Quartz, Feldspar, Carbonate, and various clay minerals, facilitating shale classification. Five distinct lithofacies were delineated, encompassing calcareous, clayey, calcareous siliceous mixed, calcareous clayey mixed shales, and siliceous rocks. Noteworthy mineralogical compositions include abundant kaolinite, chlorite, and hematite minerals in the Maastrichtian succession, transitioning to montmorillonite, illite, and pyrite dominance in the Early Maastrichtian succession. Through clay mineralogy, this study discerns significant shifts in paleoenvironmental conditions, ranging from anoxic, arid to semi-arid climates during the Campanian to warm/wet, oxidizing environments during Maastrichtian, and finally to arid/semi-arid conditions during the early Paleocene. Additionally, evidence of early burial diagenesis and Late Maastrichtian sea-level regression is identified, contributing to a comprehensive understanding of environmental dynamics during this critical geological period in the Mannar Basin in the Equatorial Margin of the Northern Indian Ocean.</div></div>","PeriodicalId":100516,"journal":{"name":"Evolving Earth","volume":"3 ","pages":"Article 100062"},"PeriodicalIF":0.0,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143427852","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-01DOI: 10.1016/j.eve.2025.100061
Sarvendra Pratap Singh , Mohammad Arif , Arvind Kumar Singh , Shreya Mishra , Vivesh Vir Kapur , Vandana Prasad , Mamilla Venkateshwarlu , Amiya Shankar Naik
The present study examines a composite section representing four basaltic and three intertrappean successions at Gujri locality, Malwa subprovince, Central India. An integrated palaeomagnetic, sedimentological, mineralogical, and palaeontological approach has been utilized to understand the palaeoenvironmental changes in a stratigraphic context. The palaeomagnetic results reveal the presence of C30n/C29r and C29r/C29n magnetic reversals providing the C30n-C29r-C29n magnetostratigraphy for the region that spans almost the entire eruption history of the Deccan volcanism. As the Malwa lava flows contain C30n magnetochron, it represents the earliest basalt flows of Deccan volcanism compared to the Western Ghats sequences. Additionally, the record of the younger C29n magnetochron suggests that the Malwa and Mandla lava flows are magnetostratigraphically correlatable and experienced synchronous volcanic activity with the Western Ghats sequences during the main (C29r) and late (C29n) phases of Deccan volcanic eruption. Sedimentological and palaeontological data support that the intertrappean sediments at the Gujri locality were deposited in a dominantly low to moderate-energy freshwater palustrine-lacustrine environment under tropical to sub-tropical humid conditions with seasonal precipitation. However, data from the topmost intertrappean unit at Gujri possibly hints at ‘Mock’ aridity across the C29r/C29n transition.
{"title":"Magnetostratigraphic perspectives and palaeoenvironmental implications of Deccan volcano-sedimentary succession within the Malwa subprovince, Central India","authors":"Sarvendra Pratap Singh , Mohammad Arif , Arvind Kumar Singh , Shreya Mishra , Vivesh Vir Kapur , Vandana Prasad , Mamilla Venkateshwarlu , Amiya Shankar Naik","doi":"10.1016/j.eve.2025.100061","DOIUrl":"10.1016/j.eve.2025.100061","url":null,"abstract":"<div><div>The present study examines a composite section representing four basaltic and three intertrappean successions at Gujri locality, Malwa subprovince, Central India. An integrated palaeomagnetic, sedimentological, mineralogical, and palaeontological approach has been utilized to understand the palaeoenvironmental changes in a stratigraphic context. The palaeomagnetic results reveal the presence of C30n/C29r and C29r/C29n magnetic reversals providing the C30n-C29r-C29n magnetostratigraphy for the region that spans almost the entire eruption history of the Deccan volcanism. As the Malwa lava flows contain C30n magnetochron, it represents the earliest basalt flows of Deccan volcanism compared to the Western Ghats sequences. Additionally, the record of the younger C29n magnetochron suggests that the Malwa and Mandla lava flows are magnetostratigraphically correlatable and experienced synchronous volcanic activity with the Western Ghats sequences during the main (C29r) and late (C29n) phases of Deccan volcanic eruption. Sedimentological and palaeontological data support that the intertrappean sediments at the Gujri locality were deposited in a dominantly low to moderate-energy freshwater palustrine-lacustrine environment under tropical to sub-tropical humid conditions with seasonal precipitation. However, data from the topmost intertrappean unit at Gujri possibly hints at ‘Mock’ aridity across the C29r/C29n transition.</div></div>","PeriodicalId":100516,"journal":{"name":"Evolving Earth","volume":"3 ","pages":"Article 100061"},"PeriodicalIF":0.0,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143437555","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The geochemical investigation of shales from Mundeck Formation of the Kribi-Campo sub-basin was conducted to determine the origin, tectonic setting evolution, paleo-weathering conditions, sediment maturity and cycling. The research included a comprehensive field survey, sample collections, and analysis of a variety of major, trace, and rare-earth elements using inductive couple plasma-atomic emission spectrum (ICP-AES) and inductive couple plasma-mass spectrum (ICP-MS). Provenance plots of La/Sc, Th/Co, Cr/Th, Th/Sc ratios and Zr vs TiO2, Al2O3vs TiO2 disclosed a felsic to mixed rock composition as the source rock of the studied shales. The felsic to mixed source rock compositions are also supported by an enrichment of LREE/HREE and a negative europium anomaly on chondrite calculation and chondrite normalized diagram. Discriminant diagrams of DF(A-P)M, and DF(A-P)MT used, designate an active marginal source rock for the studied shales. The active margin signature in this work shows the source rocks of the study shales was affected by the tectono thermal events of the Pan African Orogeny also known as the Brasiliano orogeny in South America. The chemical index of alteration (CIA and CIX) and the plagioclase index of alteration (PIA and PIX) suggest weak to extreme intensity. These variations are cause by potassium enrichment and depletion during weathering. The old and new ICV calculated values suggest that the shales are immature to mature. The plots of Zr and (La/Yb)N, Th/Sc and (Gd/Yb)N ratios show the studied shales are positive correlated and fall away from the zircon addition domain, thus confirming that they are immature to mature first cycle sediments.
{"title":"Provenance, paleoweathering and maturity study of shales in the Mundeck Formation of Kribi-Campo sub-basin in the western African margin (A geochemical approach)","authors":"Ashukem Ethel Nkongho , Bokanda Ekoko Eric , Bisse Salomon Betrant , Kwankam Florence Njinto , Philip Fralick , Ikose Franklin , Nzesseu Valentino , Belinga Belinga Cedric , Ekomane Emile","doi":"10.1016/j.eve.2025.100084","DOIUrl":"10.1016/j.eve.2025.100084","url":null,"abstract":"<div><div>The geochemical investigation of shales from Mundeck Formation of the Kribi-Campo sub-basin was conducted to determine the origin, tectonic setting evolution, paleo-weathering conditions, sediment maturity and cycling. The research included a comprehensive field survey, sample collections, and analysis of a variety of major, trace, and rare-earth elements using inductive couple plasma-atomic emission spectrum (ICP-AES) and inductive couple plasma-mass spectrum (ICP-MS). Provenance plots of La/Sc, Th/Co, Cr/Th, Th/Sc ratios and Zr vs TiO<sub>2</sub>, Al<sub>2</sub>O<sub>3</sub>vs TiO<sub>2</sub> disclosed a felsic to mixed rock composition as the source rock of the studied shales. The felsic to mixed source rock compositions are also supported by an enrichment of LREE/HREE and a negative europium anomaly on chondrite calculation and chondrite normalized diagram. Discriminant diagrams of DF(A-P)M, and DF(A-P)MT used, designate an active marginal source rock for the studied shales. The active margin signature in this work shows the source rocks of the study shales was affected by the tectono thermal events of the Pan African Orogeny also known as the Brasiliano orogeny in South America. The chemical index of alteration (CIA and CIX) and the plagioclase index of alteration (PIA and PIX) suggest weak to extreme intensity. These variations are cause by potassium enrichment and depletion during weathering. The old and new ICV calculated values suggest that the shales are immature to mature. The plots of Zr and (La/Yb)<sub>N</sub>, Th/Sc and (Gd/Yb)<sub>N</sub> ratios show the studied shales are positive correlated and fall away from the zircon addition domain, thus confirming that they are immature to mature first cycle sediments.</div></div>","PeriodicalId":100516,"journal":{"name":"Evolving Earth","volume":"3 ","pages":"Article 100084"},"PeriodicalIF":0.0,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145424561","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-01DOI: 10.1016/j.eve.2024.100055
Alan Cannell , Federico J. Degrange
Four genera of distantly phylogenetically very large volant birds existed for most of the Pliocene: Pelagornithidae seabirds; the large North American Teratornithidae, the stork Leptoptilos falconeri in Africa and Asia, and the gigantic vulture Dryornis pampeanus in Argentina. All became extinct around 2 to 3 Ma. The reasons for their demise are puzzling, as the Pelagornithidae had a world-wide evolutionary history of more than 50 Ma, smaller teratorns were still extant in the Holocene, and smaller stork and vulture species continue to be successful today. Extant large birds have a common critical takeoff airspeed suggesting biomechanical constraints in terms of power, risk and launch speed. Atmospheric mass is not constant over time and estimates for Late Pliocene atmospheric density, based on the difference between marine and terrestrial derived pCO2 and isotopes in amber, suggest a value equivalent to about 1.2 bar that dropped to the present level over the period from ∼3.3 to 2.0 Ma. Simulations of the flight of these extinct species suggest that in the present atmosphere at sea level (∼1) bar their takeoff airspeeds would have exceeded critical values; however, at 1.2 bar all the extinct species present takeoff airspeeds similar to those of large extant volant birds and which are within their muscle power and kinetic energy limits. A loss in atmospheric density may therefore have caused biomechanical and ecological stress contributing to their extinction and/or evolution of smaller forms.
{"title":"Into thin air: The loss of the pliocene giant volant birds","authors":"Alan Cannell , Federico J. Degrange","doi":"10.1016/j.eve.2024.100055","DOIUrl":"10.1016/j.eve.2024.100055","url":null,"abstract":"<div><div>Four genera of distantly phylogenetically very large volant birds existed for most of the Pliocene: Pelagornithidae seabirds; the large North American Teratornithidae, the stork <em>Leptoptilos falconeri</em> in Africa and Asia, and the gigantic vulture <em>Dryornis pampeanus</em> in Argentina. All became extinct around 2 to 3 Ma. The reasons for their demise are puzzling, as the Pelagornithidae had a world-wide evolutionary history of more than 50 Ma, smaller teratorns were still extant in the Holocene, and smaller stork and vulture species continue to be successful today. Extant large birds have a common critical takeoff airspeed suggesting biomechanical constraints in terms of power, risk and launch speed. Atmospheric mass is not constant over time and estimates for Late Pliocene atmospheric density, based on the difference between marine and terrestrial derived pCO<sub>2</sub> and isotopes in amber, suggest a value equivalent to about 1.2 bar that dropped to the present level over the period from ∼3.3 to 2.0 Ma. Simulations of the flight of these extinct species suggest that in the present atmosphere at sea level (∼1) bar their takeoff airspeeds would have exceeded critical values; however, at 1.2 bar all the extinct species present takeoff airspeeds similar to those of large extant volant birds and which are within their muscle power and kinetic energy limits. A loss in atmospheric density may therefore have caused biomechanical and ecological stress contributing to their extinction and/or evolution of smaller forms.</div></div>","PeriodicalId":100516,"journal":{"name":"Evolving Earth","volume":"3 ","pages":"Article 100055"},"PeriodicalIF":0.0,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143097472","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-01DOI: 10.1016/j.eve.2025.100058
Tammo Reichgelt , Christopher K. West
Leaf megafloras represent a snapshot of local environmental conditions in Earth's history. As such, they are an important way to understand terrestrial climate analogues for future warmer climate scenarios. Here, we present paleoclimate, productivity, and biome reconstructions of 108 globally distributed Miocene leaf megafloras using a standardized method based on leaf physiognomy. Our results show that the Miocene had higher than modern zonal temperature, precipitation and net primary productivity (NPP) averages, especially for precipitation at latitudes >30°N/°S, suggesting enhanced poleward moisture transport in both hemispheres and a greener biosphere. There is a dearth of Miocene data in the tropics and notably an absence of data points in equatorial localities that have high modern NPP (rainforests), which makes a direct comparison complicated. 89% of investigated sites underwent a precipitation decrease from the Miocene to modern, whereas 66% underwent a temperature decrease, and 60% underwent both a precipitation and a temperature decrease. 67% of sites had more productive biomes during the Miocene than today. Most notably, forested biomes were replaced by more open woodland/shrubland or grassland biomes. Correspondingly, the average NPP decrease from the Miocene to today of our investigated localities was conservatively ∼250 gC m−2 yr−1 or ∼450 gC m−2 yr−1 by comparison of zonal averages. Considered collectively, leaf megafloras reveal an overall greener Miocene world that appears to be largely driven by greater moisture availability.
{"title":"Insights into greener Miocene biomes and globally enhanced terrestrial productivity from fossil leaves","authors":"Tammo Reichgelt , Christopher K. West","doi":"10.1016/j.eve.2025.100058","DOIUrl":"10.1016/j.eve.2025.100058","url":null,"abstract":"<div><div>Leaf megafloras represent a snapshot of local environmental conditions in Earth's history. As such, they are an important way to understand terrestrial climate analogues for future warmer climate scenarios. Here, we present paleoclimate, productivity, and biome reconstructions of 108 globally distributed Miocene leaf megafloras using a standardized method based on leaf physiognomy. Our results show that the Miocene had higher than modern zonal temperature, precipitation and net primary productivity (NPP) averages, especially for precipitation at latitudes >30°N/°S, suggesting enhanced poleward moisture transport in both hemispheres and a greener biosphere. There is a dearth of Miocene data in the tropics and notably an absence of data points in equatorial localities that have high modern NPP (rainforests), which makes a direct comparison complicated. 89% of investigated sites underwent a precipitation decrease from the Miocene to modern, whereas 66% underwent a temperature decrease, and 60% underwent both a precipitation and a temperature decrease. 67% of sites had more productive biomes during the Miocene than today. Most notably, forested biomes were replaced by more open woodland/shrubland or grassland biomes. Correspondingly, the average NPP decrease from the Miocene to today of our investigated localities was conservatively ∼250 gC m<sup>−2</sup> yr<sup>−1</sup> or ∼450 gC m<sup>−2</sup> yr<sup>−1</sup> by comparison of zonal averages. Considered collectively, leaf megafloras reveal an overall greener Miocene world that appears to be largely driven by greater moisture availability.</div></div>","PeriodicalId":100516,"journal":{"name":"Evolving Earth","volume":"3 ","pages":"Article 100058"},"PeriodicalIF":0.0,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143097917","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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