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Tube structures of probable microbial origin in the Neoarchean Carawine Dolomite, Hamersley Basin, Western Australia

Tube structures of probable microbial origin in the Neoarchean Carawine Dolomite, Hamersley... ABSTRACT The ~2.63 Ga Carawine Dolomite, Hamersley Basin, Western Australia, preserves tube structures of probable microbial origin that formed in a low energy environment. The tubes are 0.4–1.8 cm in diameter and at least 10–16 cm long in outcrop. The tubes are defined by dark, 45‐µm‐thick dolomicritic walls, whereas the tube fill and host rock are composed of 30 µm, cloudy dolomite crystals and rare 170‐ to 425‐µm‐wide, dark well‐sorted clasts. Closely spaced, rarely discontinuous laminae coat the insides of tubes; less closely spaced, peaked, discontinuous laminae coat the outsides of tubes. The laminae on the outsides of tubes are often intercalated with mammilate structures. The presence of probable microbial coatings on both the insides and the outsides of the tube walls requires that the tubes formed above the sediment–water interface. These tube structures probably formed during gas‐charged fluid escape, similar to tubes observed in ancient and modern hydrocarbon seeps and cylindrical water transfer structures in sandstones. The laminae that coat the tubes have very similar geometries to modern biofilms that form in both turbulent and laminar flow, and their geometries probably reflect flow conditions during the fluid escape. The identification of these structures suggests that the preserved interaction between fluid escape and microbial growth in carbonates may be more common than previously thought. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Geobiology Wiley

Tube structures of probable microbial origin in the Neoarchean Carawine Dolomite, Hamersley Basin, Western Australia

Geobiology , Volume 6 (1) – Jan 1, 2008

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References (53)

Publisher
Wiley
Copyright
Copyright © 2008 Wiley Subscription Services, Inc., A Wiley Company
ISSN
1472-4677
eISSN
1472-4669
DOI
10.1111/j.1472-4669.2007.00114.x
pmid
18380888
Publisher site
See Article on Publisher Site

Abstract

ABSTRACT The ~2.63 Ga Carawine Dolomite, Hamersley Basin, Western Australia, preserves tube structures of probable microbial origin that formed in a low energy environment. The tubes are 0.4–1.8 cm in diameter and at least 10–16 cm long in outcrop. The tubes are defined by dark, 45‐µm‐thick dolomicritic walls, whereas the tube fill and host rock are composed of 30 µm, cloudy dolomite crystals and rare 170‐ to 425‐µm‐wide, dark well‐sorted clasts. Closely spaced, rarely discontinuous laminae coat the insides of tubes; less closely spaced, peaked, discontinuous laminae coat the outsides of tubes. The laminae on the outsides of tubes are often intercalated with mammilate structures. The presence of probable microbial coatings on both the insides and the outsides of the tube walls requires that the tubes formed above the sediment–water interface. These tube structures probably formed during gas‐charged fluid escape, similar to tubes observed in ancient and modern hydrocarbon seeps and cylindrical water transfer structures in sandstones. The laminae that coat the tubes have very similar geometries to modern biofilms that form in both turbulent and laminar flow, and their geometries probably reflect flow conditions during the fluid escape. The identification of these structures suggests that the preserved interaction between fluid escape and microbial growth in carbonates may be more common than previously thought.

Journal

GeobiologyWiley

Published: Jan 1, 2008

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