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Letters to Nature

Nature 407, 626-629 (5 October 2000) | doi:10.1038/35036579; Received 25 April 2000; Accepted 10 August 2000

Modern freshwater microbialite analogues for ancient dendritic reef structures

Bernard Laval1,2, Sherry L. Cady3, John C. Pollack4, Christopher P. McKay5, John S. Bird1, John P. Grotzinger6, Derek C. Ford7 & Harry R. Bohm1

  1. School of Engineering Science, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada
  2. Department of Geology, Portland State University, Portland, Oregon 97201, USA
  3. Forest Sciences, Nelson Forest Region , British Columbia, V1L 4C6, Canada
  4. NASA Ames Research Centre, Moffett Field, California 94035, USA
  5. Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, USA
  6. McMaster University, Hamilton , Ontario, L8S 4KL, Canada
  7. Present address: Centre for Water Research, University of Western Australia, Nedlands, Western Australia 6907, Australia

Correspondence to: Sherry L. Cady3 Correspondence and requests for materials should be addressed to S.L.C. (e-mail: Email: cadys@pdx.edu).

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Microbialites are organosedimentary structures that can be constructed by a variety of metabolically distinct taxa1. Consequently, microbialite structures abound in the fossil record, although the exact nature of the biogeochemical processes that produced them is often unknown2. One such class of ancient calcareous structures3, 4, 5, Epiphyton and Girvanella, appear in great abundance during the Early Cambrian. Together with Archeocyathids, stromatolites and thrombolites, they formed major Cambrian reef belts. To a large extent, Middle to Late Cambrian reefs are similar to Precambrian reefs6, with the exception that the latter, including terminal Proterozoic reefs7, do not contain Epiphyton or Girvanella. Here we report the discovery in Pavilion Lake, British Columbia, Canada, of a distinctive assemblage of freshwater calcite microbialites, some of which display microstructures similar to the fabrics displayed by Epiphyton and Girvanella. The morphologies of the modern microbialites vary with depth, and dendritic microstructures of the deep water (>30 m) mounds indicate that they may be modern analogues for the ancient calcareous structures. These microbialites thus provide an opportunity to study the biogeochemical interactions that produce fabrics similar to those of some enigmatic Early Cambrian reef structures.