Formation of Kinneyia via shear-induced instabilities in microbial mats

Thomas, K, Herminghaus, S, Porada, H and Goehring, L ORCID: 0000-0002-3858-7295, 2013. Formation of Kinneyia via shear-induced instabilities in microbial mats. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 371 (2004), p. 20120362. ISSN 1364-503X

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Abstract

Kinneyia are a class of microbially mediated sedimentary fossils. Characterized by clearly defined ripple structures, Kinneyia are generally found in areas that were formally littoral habitats and covered by microbial mats. To date, there has been no conclusive explanation of the processes involved in the formation of these fossils. Microbial mats behave like viscoelastic fluids. We propose that the key mechanism involved in the formation of Kinneyia is a Kelvin–Helmholtz-type instability induced in a viscoelastic film under flowing water. A ripple corrugation is spontaneously induced in the film and grows in amplitude over time. Theoretical predictions show that the ripple instability has a wavelength proportional to the thickness of the film. Experiments carried out using viscoelastic films confirm this prediction. The ripple pattern that forms has a wavelength roughly three times the thickness of the film. This behaviour is independent of the viscosity of the film and the flow conditions. Laboratory-analogue Kinneyia were formed via the sedimentation of glass beads, which preferentially deposit in the troughs of the ripples. Well-ordered patterns form, with both honeycomb-like and parallel ridges being observed, depending on the flow speed. These patterns correspond well with those found in Kinneyia, with similar morphologies, wavelengths and amplitudes being observed.

Item Type: Journal article
Publication Title: Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
Creators: Thomas, K., Herminghaus, S., Porada, H. and Goehring, L.
Publisher: The Royal Society Publishing
Date: 4 November 2013
Volume: 371
Number: 2004
ISSN: 1364-503X
Identifiers:
NumberType
10.1098/rsta.2012.0362DOI
24191114PubMed ID
Divisions: Schools > School of Science and Technology
Depositing User: Jonathan Gallacher
Date Added: 05 Sep 2016 09:51
Last Modified: 09 Jun 2017 14:05
URI: http://irep.ntu.ac.uk/id/eprint/28374

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