Controles do desenvolvimento e diversidade dos estromatólitos do arqueano superior

Controls on development and diversity of Early Archean stromatolites

Abigail C. Allwooda,b,1, John P. Grotzingerc,1, Andrew H. Knolld, Ian W. Burchb, Mark S. Andersona, Max L. Colemana and Isik Kanika

+ Author Affiliations

aNational Aeronautics and Space Administration Astrobiology Institute at the Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109;

bAustralian Centre for Astrobiology, University of New South Wales, Sydney 2052, Australia;

cDepartment of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125; and

dDepartment of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138

Contributed by John P. Grotzinger, April 14, 2009 (received for review February 6, 2009)

Abstract

The ≈3,450-million-year-old Strelley Pool Formation in Western Australia contains a reef-like assembly of laminated sedimentary accretion structures (stromatolites) that have macroscale characteristics suggestive of biological influence. However, direct microscale evidence of biology—namely, organic microbial remains or biosedimentary fabrics—has to date eluded discovery in the extensively-recrystallized rocks. Recently-identified outcrops with relatively good textural preservation record microscale evidence of primary sedimentary processes, including some that indicate probable microbial mat formation. Furthermore, we find relict fabrics and organic layers that covary with stromatolite morphology, linking morphologic diversity to changes in sedimentation, seafloor mineral precipitation, and inferred microbial mat development. Thus, the most direct and compelling signatures of life in the Strelley Pool Formation are those observed at the microscopic scale. By examining spatiotemporal changes in microscale characteristics it is possible not only to recognize the presence of probable microbial mats during stromatolite development, but also to infer aspects of the biological inputs to stromatolite morphogenesis. The persistence of an inferred biological signal through changing environmental circumstances and stromatolite types indicates that benthic microbial populations adapted to shifting environmental conditions in early oceans.

microbe paleontology biosignature carbonate reef

Footnotes

1To whom correspondence may be addressed. E-mail: abigail.c.allwood@jpl.nasa.gov or grotz@gps.caltech.edu

This contribution is part of the special series of Inaugural Articles by members of the National Academy of Sciences elected in 2002.

Author contributions: A.C.A., J.P.G., M.L.C., and I.K. designed research; A.C.A., J.P.G., A.H.K., I.W.B., and M.S.A. performed research; A.C.A., J.P.G., A.H.K., I.W.B., and M.S.A. analyzed data; and A.C.A., J.P.G., and A.H.K. wrote the paper.

The authors declare no conflict of interest.

This article contains supporting information online at www.pnas.org/cgi/content/full/0903323106/DCSupplemental.

↵* Salant NL, Hassan MA, Fall meeting of the American Geophysical Union 10–14 Dec, 2007, San Francisco, CA, abstract H13D-1534.

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