The Evolution of Life and its Impact on Sedimentation

  1. Wladyslaw Altermann1 and
  2. Patricia L. Corcoran2
  1. W. Altermann

Published Online: 12 MAR 2009

DOI: 10.1002/9781444304312.ch2

Precambrian Sedimentary Environments: A Modern Approach to Ancient Depositional Systems

Precambrian Sedimentary Environments: A Modern Approach to Ancient Depositional Systems

How to Cite

Altermann, W. (2002) The Evolution of Life and its Impact on Sedimentation, in Precambrian Sedimentary Environments: A Modern Approach to Ancient Depositional Systems (eds W. Altermann and P. L. Corcoran), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304312.ch2

Editor Information

  1. 1

    Institut für Allgemeine und Angewandte Geologie, Ludwig-Maximilians-Universität München, Luisenstrasse 37, D-80333 Munich, Germany

  2. 2

    Department of Earth Sciences, Dalhousie University, Halifax, Nova Scotia, B3H 3J5, Canada

Author Information

  1. Institut für Allgemeine und Angewandte Geologie, Ludwig-Maximilians-Universität München, Luisenstrasse 37, D-80333 Munich, Germany

Publication History

  1. Published Online: 12 MAR 2009
  2. Published Print: 18 FEB 2002

ISBN Information

Print ISBN: 9780632064151

Online ISBN: 9781444304312

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Keywords:

  • evolution of life and impact on sedimentation;
  • precambrian Earth environments - discussed together with pathways of abiotic synthesis of life and its early evolution;
  • environmental distribution of precambrian stromatolites;
  • microbial life and problems in its identification;
  • precambrian fossil record;
  • classification of precambrian microfossils;
  • first evidence of biosedimentation;
  • nature of precambrian biosedimentation;
  • stromatolites and precambrian stratigraphy

Summary

In this overview, Precambrian Earth environments are discussed together with the pathways of the abiotic synthesis of life and its early evolution. Consideration of the possible steps in the assembly of amino acids, protein polymers, RNA strings or DNA helixes provides contradictory inferences about environmental conditions at the time of their formation, varying between cold and hot aqueous settings. Problems in identification of microbial life in Precambrian sedimentary rocks are grounded in insufficient preservation, metamorphic alteration and lack of criteria other than isotopic and morphological similarity to extant microbes. The earliest microfossiliferous rocks hint at extreme hypersaline and thermophilic conditions of microbial life, although at 3.5 Ga, life was already widespread in aquatic environments, and was sufficiently advanced, being capable of photosynthesis. As life has arisen on Earth, it has gradually gained an increasing influence on sedimentary environments. This influence was initially mediated through weathering and depositional processes, governed by the chemistry of the atmosphere and oceans and by the direct biochemical precipitation of sediments. Stabilization of siliciclastic sediments by microbial mats appears to have been an important process in the Proterozoic, but is difficult to prove because of organic degradation. Only at the terminal Neoproterozoic did the direct influence on sediments by grazing and burrowing organisms become apparent in the rock record. Stromatolitic carbonates of the Archaean and early Proterozoic are recognized as bona fide biogenic sediments, although microbial mediation in their formation can rarely be proven. Stromatolites and bacterial microfossils are considered unsuitable for stratigraphic subdivison of the Precambrian because of the primarily environmental significance of stromatolite morphology, and the evolutionary conservatism in bacterial morphology. Calcification of stromatolites might have been induced directly by the bacterial communities or by chemical precipitation from Ca-oversaturated water. The chemistry of ocean water in the Precambrian is equally controversial, as the oxygen levels in the Precambrian atmosphere, and their influence on chemical sediments, are difficult to ascertain. Examples of the influence of the atmosphere and hydrosphere on the evolution of life demonstrate the interrelated dependence of the Precambrian biosphere, hydrosphere, atmosphere and lithosphere.