Davi F. Carvalho, A. Nogueira, M. Macambira, C. Lana, R. F. Santos, Julia Guélard, P. Sansjofre
{"title":"巴西亚马逊克拉通南部海底结晶扇的U–Pb原位测年限制Puga盖层碳酸盐岩的成岩作用","authors":"Davi F. Carvalho, A. Nogueira, M. Macambira, C. Lana, R. F. Santos, Julia Guélard, P. Sansjofre","doi":"10.1111/ter.12652","DOIUrl":null,"url":null,"abstract":"Cap carbonates overlying Marinoan (635 Ma) glacial deposits worldwide record extreme paleoceanographic changes that may have triggered the rise of macroscopic life. However, the lack of geochronological constraints on these successions hinders reconciling climate and environmental change. Their upper part is marked by anomalous aragonite precipitation associated with large transgression and oxygenation of the post‐glacial ocean. Neomorphism of these deposits to low‐Mg calcite often includes centimetre‐scale seafloor crystal fans. We used in‐situ U–Pb dating and C and Sr isotopic analyses in the Puga cap carbonate to estimate the nature and timing of the neomorphism process. An age of 623 ± 3 [9] Ma (δ13C ~ −6‰ and 87Sr/87Sr ~ 0.7071–0.7075) for a blocky calcite cement is consistent with solution‐reprecipitation within the fans during final filling and diagenetic stabilization of the cap carbonate fabric. This result improves previous cap carbonate direct dating, providing a rare Lower Ediacaran chronostratigraphic reference.","PeriodicalId":22260,"journal":{"name":"Terra Nova","volume":null,"pages":null},"PeriodicalIF":2.2000,"publicationDate":"2023-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"1","resultStr":"{\"title\":\"Constraining the diagenesis of the Puga cap carbonate from U–Pb in‐situ dating of seafloor crystal fans, southern Amazonian craton, Brazil\",\"authors\":\"Davi F. Carvalho, A. Nogueira, M. Macambira, C. Lana, R. F. Santos, Julia Guélard, P. Sansjofre\",\"doi\":\"10.1111/ter.12652\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"Cap carbonates overlying Marinoan (635 Ma) glacial deposits worldwide record extreme paleoceanographic changes that may have triggered the rise of macroscopic life. However, the lack of geochronological constraints on these successions hinders reconciling climate and environmental change. Their upper part is marked by anomalous aragonite precipitation associated with large transgression and oxygenation of the post‐glacial ocean. Neomorphism of these deposits to low‐Mg calcite often includes centimetre‐scale seafloor crystal fans. We used in‐situ U–Pb dating and C and Sr isotopic analyses in the Puga cap carbonate to estimate the nature and timing of the neomorphism process. An age of 623 ± 3 [9] Ma (δ13C ~ −6‰ and 87Sr/87Sr ~ 0.7071–0.7075) for a blocky calcite cement is consistent with solution‐reprecipitation within the fans during final filling and diagenetic stabilization of the cap carbonate fabric. This result improves previous cap carbonate direct dating, providing a rare Lower Ediacaran chronostratigraphic reference.\",\"PeriodicalId\":22260,\"journal\":{\"name\":\"Terra Nova\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":2.2000,\"publicationDate\":\"2023-03-24\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"1\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Terra Nova\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://doi.org/10.1111/ter.12652\",\"RegionNum\":3,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"GEOSCIENCES, MULTIDISCIPLINARY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Terra Nova","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.1111/ter.12652","RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"GEOSCIENCES, MULTIDISCIPLINARY","Score":null,"Total":0}
Constraining the diagenesis of the Puga cap carbonate from U–Pb in‐situ dating of seafloor crystal fans, southern Amazonian craton, Brazil
Cap carbonates overlying Marinoan (635 Ma) glacial deposits worldwide record extreme paleoceanographic changes that may have triggered the rise of macroscopic life. However, the lack of geochronological constraints on these successions hinders reconciling climate and environmental change. Their upper part is marked by anomalous aragonite precipitation associated with large transgression and oxygenation of the post‐glacial ocean. Neomorphism of these deposits to low‐Mg calcite often includes centimetre‐scale seafloor crystal fans. We used in‐situ U–Pb dating and C and Sr isotopic analyses in the Puga cap carbonate to estimate the nature and timing of the neomorphism process. An age of 623 ± 3 [9] Ma (δ13C ~ −6‰ and 87Sr/87Sr ~ 0.7071–0.7075) for a blocky calcite cement is consistent with solution‐reprecipitation within the fans during final filling and diagenetic stabilization of the cap carbonate fabric. This result improves previous cap carbonate direct dating, providing a rare Lower Ediacaran chronostratigraphic reference.
期刊介绍:
Terra Nova publishes short, innovative and provocative papers of interest to a wide readership and covering the broadest spectrum of the Solid Earth and Planetary Sciences. Terra Nova encompasses geology, geophysics and geochemistry, and extends to the fluid envelopes (atmosphere, ocean, environment) whenever coupling with the Solid Earth is involved.