Microbes and Black Shales

Abstract

lllack shales, in general, form under low oxic to anoxic conditions, where microbes have evolved a variety of metabolic pathways. Modern oxygen-depleted environments typically con-tain anaerobic heterotrophic bacteria, aerobic chemolithoautotro-phic bacteria (which partly live in mutualistic relationship with certain metazoa) and anaerobic photoautotrophic bacteria. These bacteria mainly degrade but partly also form organic matter. Their metabolic pathways and their preservational potential in the fossil record are discussed here. In many cases only metabolic waste products, e.g. pyrite, and certain bacterial derived biomarkers are preserved. Relicts of microbials mats occur as rare exceptions.