The Upper Proterozoic glacigenous rocks in the southeastern margin of the Yangtze platform were accumulated in a glacially influenced marine environment with extension set- ting. Two type I depositional sequences have...The Upper Proterozoic glacigenous rocks in the southeastern margin of the Yangtze platform were accumulated in a glacially influenced marine environment with extension set- ting. Two type I depositional sequences have been identified in the glacioclastic sediments the their boundaries enhanced by both tectonism and the incision of glaciation. The lower sequence (SQ1), comprising Changan and Fulu formations (Guangxi Province), Jiangkou and Xiangmen formations(Hunan Province) and their equivalents, is bounded by erosional unconformities both at the base and on the top. The upper sequence (SQ2), composed mainly of Nantuo Formation and its equivalents, is confined by an erosional unconformity at the base and covered by an exposure surface of karstification on the top. The depositional systems tracts are difficult to be distinguished directly and mainly characterized by the variation in glacioclastic supplies. Two types of episodic parasequeuces can be identified in the glacigenous rocks and are related to the evolution of depositional systems tracts. Both the sequences and parasequences are caused by autocyclic mechanism. The present research shows that the Upper Proterozoic glacigenous deposits are of significance for the analysis of the tectonic evolution of the Late Precambrian basin in South China.展开更多
This study presents the first detrital zircon U-Pb analysis alongside new petrographic data from the Jejenes Formation(Serpukhovian-Bashkirian),located on the southern margin of the Paganzo Basin,Argentina in Southwes...This study presents the first detrital zircon U-Pb analysis alongside new petrographic data from the Jejenes Formation(Serpukhovian-Bashkirian),located on the southern margin of the Paganzo Basin,Argentina in Southwest Gondwana.The results were compared with previously published data from other synchronously deposited units to the north(Guandacol Formation) and northeast(Malanzán Formation).Notably,glacigenic deposits are present in both the Guandacol and Jejenes formations but absent in the Malanzán Formation.A sedimentary provenance analysis was conducted for the three units,highlighting similarities and differences among the depocenters,allowing for the reconstruction of the paleogeographic and topographic landscape of the Paganzo Basin during the Serpukhovian-Bashkirian time.The comparative analysis supports the idea of disconnection and isolation among the three depocenters with each unit recording predominantly proximal sources and the recycling of pre-Carboniferous substrate.Although certain similarities exist in the age distribution of the detrital zircon grains recorded for the Malanzán and Guandacol formations,this does not imply that the depocenters were connected or fed by the same source area.Instead,these successions were likely sourced from rocks with a similar geological history,resulting in comparable age distributions due to sediment recycling.Thus,the results support a conservative approach when estimating sedimentary provenance in ancient glacigenic deposits,emphasizing the need to evaluate local sediment sources.The absence of glacigenic deposits in the Malanzán Formation could be linked to a lower topography,linked to distinct tectonic histories in the Pie de Palo,Valle Fértil,and Chepes-Malanzán ranges,underscoring the role of tectonic inheritance in the distribution of glacial centers during the Late Paleozoic Ice Age.展开更多
文摘The Upper Proterozoic glacigenous rocks in the southeastern margin of the Yangtze platform were accumulated in a glacially influenced marine environment with extension set- ting. Two type I depositional sequences have been identified in the glacioclastic sediments the their boundaries enhanced by both tectonism and the incision of glaciation. The lower sequence (SQ1), comprising Changan and Fulu formations (Guangxi Province), Jiangkou and Xiangmen formations(Hunan Province) and their equivalents, is bounded by erosional unconformities both at the base and on the top. The upper sequence (SQ2), composed mainly of Nantuo Formation and its equivalents, is confined by an erosional unconformity at the base and covered by an exposure surface of karstification on the top. The depositional systems tracts are difficult to be distinguished directly and mainly characterized by the variation in glacioclastic supplies. Two types of episodic parasequeuces can be identified in the glacigenous rocks and are related to the evolution of depositional systems tracts. Both the sequences and parasequences are caused by autocyclic mechanism. The present research shows that the Upper Proterozoic glacigenous deposits are of significance for the analysis of the tectonic evolution of the Late Precambrian basin in South China.
基金funding from the project PPID N044,“Characterization,provenance and extent of the Chanic Orogen in western Argentina.Its influence on post-orogenic deposits.Correlation and interpretation of the geodynamic and paleogeographic evolution”granted by the National University of La Plata(UNLP)
文摘This study presents the first detrital zircon U-Pb analysis alongside new petrographic data from the Jejenes Formation(Serpukhovian-Bashkirian),located on the southern margin of the Paganzo Basin,Argentina in Southwest Gondwana.The results were compared with previously published data from other synchronously deposited units to the north(Guandacol Formation) and northeast(Malanzán Formation).Notably,glacigenic deposits are present in both the Guandacol and Jejenes formations but absent in the Malanzán Formation.A sedimentary provenance analysis was conducted for the three units,highlighting similarities and differences among the depocenters,allowing for the reconstruction of the paleogeographic and topographic landscape of the Paganzo Basin during the Serpukhovian-Bashkirian time.The comparative analysis supports the idea of disconnection and isolation among the three depocenters with each unit recording predominantly proximal sources and the recycling of pre-Carboniferous substrate.Although certain similarities exist in the age distribution of the detrital zircon grains recorded for the Malanzán and Guandacol formations,this does not imply that the depocenters were connected or fed by the same source area.Instead,these successions were likely sourced from rocks with a similar geological history,resulting in comparable age distributions due to sediment recycling.Thus,the results support a conservative approach when estimating sedimentary provenance in ancient glacigenic deposits,emphasizing the need to evaluate local sediment sources.The absence of glacigenic deposits in the Malanzán Formation could be linked to a lower topography,linked to distinct tectonic histories in the Pie de Palo,Valle Fértil,and Chepes-Malanzán ranges,underscoring the role of tectonic inheritance in the distribution of glacial centers during the Late Paleozoic Ice Age.
