Stromatolite reef crusts, Early Cretaceous, Spain: bacterial origin of in situ-precipitated peloid microspar?
Article first published online: 20 DEC 2005
Volume 53, Issue 1, pages 23–34, February 2006
How to Cite
RIDING, R. and TOMÁS, S. (2006), Stromatolite reef crusts, Early Cretaceous, Spain: bacterial origin of in situ-precipitated peloid microspar?. Sedimentology, 53: 23–34. doi: 10.1111/j.1365-3091.2005.00751.x
- Issue published online: 20 DEC 2005
- Article first published online: 20 DEC 2005
- Manuscript received 6 October 2004; revision accepted 8 February 2005
Peloidal crusts are significant components of Early Cretaceous (Aptian) reef carbonates in eastern Spain. The crusts form steep-sided laminated deposits on coral and other skeletal surfaces. Their microfabric consists almost entirely of silt-sized peloids in fenestral microspar matrix. This microfabric contrasts with more poorly sorted and generally finer grained detrital wackestone–packstone fabrics of the adjacent reef matrix. Scarcity of incorporated grains indicates that the crusts did not trap many particles. It is proposed that the crusts are stromatolites and that peloids and inter-peloid space were created concurrently by bacterial degradation of organic matter. As they developed, inter-peloid voids were protected from infiltration of extraneous sediment by the organic-rich exterior surface of the stromatolite. Even spacing of the peloids within microspar may reflect self-organization of bacterial colonies in the decaying organic matrix. Compressed and partly amalgamated peloids marginal to burrows in the stromatolites suggest that the peloid fabrics were initially only partially lithified. The grainstone-like peloid fabric is therefore interpreted as having formed in situ by very early diagenetic processes driven by heterotrophic bacteria.