Microbial Structures in Neoproterozoic Cap Carbonates

“该奖项是根据2009年美国复苏与再投资法案(公法111-5)资助的。”新元古代盖状碳酸盐岩中的微生物结构Tanja BosakMIT，EAR-0843358ABSTRACT地球上的生命在过去10亿年中至少经历了两次极端冰川条件，从~710年到~6.4亿年前开始。这一提议旨在限制微生物生命的生存及其在随后的全球融化期间与环境的相互作用，这一点从全球石灰石矿床中不同寻常的微生物产生的结构中得到了记录，这些结构在这两次“雪球地球”事件之后立即形成。在第一次冰川作用后，一种未知的机制将微生物结合的深水石灰岩沉积物折叠成厘米大小的卷曲结构。晚些时候的全球冰川作用后，在覆盖冰川沉积物的浅水石灰岩中形成了直径1-3厘米的细长、近垂直的管状结构。管结石被归因于甲烷或二氧化碳的释放，或者是石灰石在微生物存在下的快速生长，但它们的形成机制仍然存在争议。将通过在纳米比亚北部地质学和地层学受限的地段绘制地图，并通过分析这些构造的岩石学和碳、氧同位素组成，来研究卷曲和管石的形成。这项拟议的工作还将检验一个新的假设：是否可以通过在实验室中培养与新元古代后期冰川后相关的条件下的现代微生物，以充氧微生物垫中形成的富氧水泡为模板来形成管石。这项拟议的工作解决了物理、化学和微生物过程如何在岩石记录上留下印记，以及它们如何在地球历史上一些最极端的时期留下印记的问题。更好地理解形成卷曲或管状结石的机制将涉及微生物群落的组成、碳循环、氧合和沉积速率以及雪球后冰川消融期间的环境化学。该项目将为一名研究生和至少两名女本科生提供跨学科培训。三个不同机构(麻省理工学院、史密斯大学和哈佛大学)的研究人员共同努力的结果。将在年度研讨会上传播。

"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)."Microbial structures in Neoproterozoic cap carbonatesTanja BosakMIT, EAR-0843358ABSTRACTLife on our planet endured extreme glacial conditions at least twice in the past billion years starting at ~ 710 and at ~640 million years ago. This proposal seeks to constrain the survival of microbial life and its interactions with the environment during the subsequent times of global melting, as recorded by unusual microbially-produced structures within global limestone deposits that formed immediately after these two 'Snowball Earth' events. After the first glaciation, an unknown mechanism folded microbially-bound deep water limestone sediments to produce cm-sized roll-up structures. After the later global glaciation, tubestones, 1-3 cm diameter elongated, sub-vertical tubular structures formed in shallow-water limestone capping the glacial deposits. The tubestones have been attributed either to the release of methane or carbon dioxide or to the fast accretion of limestone in the presence of microbes, but the mechanisms of their formation remain controversial. The formation of roll-ups and tubestones will be investigated by mapping in geochemically and stratigraphically well-constrained sections in northern Namibia and by analyzing the petrography and carbon and oxygen isotopic composition of these structures. The proposed work will also test a new hypothesis: whether tubestones can be templated by oxygen-rich blisters formed in oxygenic microbial mats, by growing modern microbes in the laboratory under conditions relevant for the later Neoproterozoic post-glacial. The proposed work addresses the questions of how physical, chemical and microbial processes leave a mark in the rock record and how they did it during some of the most extreme times in Earth history. A better understanding of mechanisms that form roll-ups or tubestones will address the composition of microbial communities, carbon cycling, oxygenation and sedimentation rates and the environmental chemistry during post-Snowball deglaciations. This project will provide interdisciplinary training to a graduate student and at least two female undergraduates. The results of collaborative efforts between researchers at three different institutions (MIT, Smith C. and Harvard U.) will be disseminated at an annual symposium.