巴西地球科学研究所Bruno S. Angonese的团队，在研究西南冈瓦纳上侏罗统Guará组的沙漠硅质碎屑叠层石中取得新进展。这一研究成果于2024年8月28日发表在国际顶尖学术期刊《地质学》上。

据研究人员介绍，硅质碎屑叠层石在地质记录中是罕见的，文献记录中它们的出现仅限于海洋和沿海环境。来自巴西南部Paraná盆地的上侏罗统Guará组，发育有独特的非海相硅质碎屑叠层石，该实例为研究大陆环境下微生物垫的捕获和粘结机制提供了难得的机会。

研究人员称，这些微生物岩的出现与风成相和河流相互层发育。叠层石穹窿的结构分层是由砂质夹层作用形成的，砂质夹层是由微生物垫对硅质碎屑颗粒的捕获和粘结，以及无定形硅到隐晶硅的原位沉淀形成的，后者直接取代了微生物菌落。二氧化硅层含有部分保存的球形至卵形体，被解释为球状微生物菌落。这些硅质碎屑叠层石是由于水化学和沉积物供应等特定环境因素的平衡形成的，这增强了捕获和粘结以及原位沉淀的过程。

本研究记录了在非海洋、富含硅、河流-风成环境中微生物生命的存在，在此之前这种环境中没有过关于凝集叠层石的报道。这些标本记录了大陆环境中微生物生命的宏观可识别证据，这些证据可能会在寻找地球和火星上的古代生命中得到解释。

附：英文原文

Title: Desertic siliciclastic stromatolites in the Upper Jurassic Guará Formation from southwestern Gondwana: Trapping and binding in a non-marine setting

Author: Bruno S. Angonese, Claiton M.S. Scherer, Luiz F. De Ros, Rossano D.L. Michel, Gabriel S. Sipp, Joao P.F. Ferronato

Issue&Volume: 2024-08-28

Abstract: Siliciclastic stromatolites are rare in the geologic record, and their occurrence recorded in the literature is restricted to marine and coastal environments. The Upper Jurassic Guará Formation, from the Paraná Basin in southern Brazil, hosts unique non-marine siliciclastic stromatolites, providing a rare opportunity to study trapping and binding mechanisms by microbial mats in a continental setting. These microbialites occur interbedded with eolian and fluvial facies. The structural layering of the stromatolite domes is formed by the intercalation of sandy layers, resulting from trapping and binding of siliciclastic grains by microbial mats and in situ precipitation of amorphous to cryptocrystalline silica, which directly replaced the microbial colonies. The silica layers contain partially preserved spherical to ovoid bodies interpreted as colonies of coccoid microorganisms. These siliciclastic stromatolites were formed due to a specific balance of environmental factors, namely water chemistry and sediment supply, which enhanced the processes of trapping and binding and in situ precipitation. They record the presence of microbial life in a non-marine, silica-rich, fluvial-eolian environment in which there were no previous published occurrences of agglutinated stromatolites. These specimens record macroscopically identifiable evidence of microbial life in a continental environment that must be accounted for in the search for ancient life on Earth and Mars.

DOI: 10.1130/G52662.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article-abstract/doi/10.1130/G52662.1/647456/Desertic-siliciclastic-stromatolites-in-the-UpperredirectedFrom=fulltext