Microbially Induced Sedimentary Structures from the 2.9 Ga old Pongola and Witwatersrand Supergroups, South Africa

沙质海洋环境中地球最早的细菌：来自南AFRICAPI：诺拉·诺夫克；海洋、地球和大气科学系；埃尔克霍恩大道4600号；弗吉尼亚州诺福克23529；nnoffke@odu.edu.细菌和蓝藻形成了覆盖大片沿海沉积物的地毯状有机层。这样的层被称为“微生物垫”。在砂质海洋沉积物中，微生物席形成了非常独特的沉积结构。这些构造被称为“微生物诱导的沉积构造-遗漏”，它们不仅从现代海洋环境中被发现，而且从所有地球时代的沙质沉积物中被发现。遗漏化石包括关于古老的席状微生物的重要信息，因此它们也是破译最早的地球-太古宙奇怪世界的重要工具。尽管许多关于太古宙海相沉积的研究集中在碳酸盐岩或硅质岩上，但PI采用了一种新的方法，通过调查砂岩序列来检测遗漏。因此，这项拟议的研究为理解地球最早的生命和环境打开了一扇新的窗口。由南非蓬格拉超级群的PI进行的一项初步研究发现了微生物诱导的沉积结构，这些结构为29亿年前的陆架环境中存在形成微生物垫的丝状细菌提供了证据--这是已知的硅屑(砂质)岩石中最古老的微生物垫(Noffke，Hazen&Amp；Nhleko，2003)。这些结构包括类似于现代蓝藻、氯杆菌或硫氧化细菌细胞的身体化石。身体化石确实可能暗示了最古老的蓝藻。矿物学、地球化学和同位素分析与构造的生物成因相一致。后续调查将阐明在太古宙发育微生物席的古环境条件。对遗漏岩层的详细调查将记录古代微生物垫的分布和变化。它将展示不同的微生物垫类型如何反映太古宙地球极端生命条件的特征。此外，研究将建立一个遗漏目录，以便将这些结构与更年轻的地球时代的结构进行比较。国际地球科学协会将在老多米尼恩大学组织一个遗漏评估参考库，为国家和国际地球科学界的研究和教学提供服务。

EARTH'S EARLIEST BACTERIA IN A SANDY MARINE ENVIRONMENT: FOSSIL MICROORGANISMS FROM THE 2.9 BILLION YEARS OLD PONGOLA AND WITWATERSRAND SUPERGROUPS, SOUTH AFRICAPI: Nora Noffke; Department of Ocean, Earth & Atmospheric Sciences; 4600 Elkhorn Avenue; Norfolk, VA 23529; nnoffke@odu.edu.Bacteria and cyanobacteria form organic, carpet-like layers that cover large areas of coastal sediments. Such layers have been termed "microbial mats". In sandy marine sediments, microbial mats cause very characteristic sedimentary structures. These structures have been termed "microbially induced sedimentary structures - MISS", and they are known not only from modern marine environments, but from sandy sediments of all Earth ages. The fossil MISS include significant information about the ancient, mat-forming microorganisms, and therefore they also constitute a significant tool in deciphering the strange world of the earliest Earth, the Archean.Whereas many studies on Archean marine deposits focus on carbonate rocks or cherts, the PI follows a new approach by investigating sandstone successions in order to detect MISS. Therefore, the proposed study opens a new window in understanding Earth's earliest life and environments.A pilot study conducted by the PI in the Pongola Supergroup, South Africa, detected microbially induced sedimentary structures that provide evidence for the existence of filamentous bacteria forming microbial mats in 2.9 billion year old shelf environments - the oldest-known occurrence of microbial mats in siliciclastic (sandy) rocks (Noffke, Hazen & Nhleko, 2003). The structures include body fossils that resemble the cells of modern cyanobacteria, chloroflexi, or sulfur-oxidizing bacteria. The body fossils could indeed hint on the oldest cyanobacteria. Mineralogical, geochemical, and isotopic analyses are consistent with a biological origin of the structures. The follow-up investigations will elucidate the paleoenvironmental conditions that permit the development of microbial mats in the Archean. A detailed survey of MISS-bearing rock strata will document the distribution and variation of the ancient microbial mats. It will show, how different microbial mat types reflect the extreme life conditions characteristic for the Archean Earth.In addition, the study will set up a catalogue of MISS in order to compare the structures with those of younger Earth ages. The PI will organize a reference repository of MISS at Old Dominion University, which would serve the national and international geoscientific community for research and teaching.