Variations in Neoarchean microbialite morphologies: clues to controls on microbialite morphologies through time

Abstract

The Neoarchean Carawine Formation, Hamersley Group, Western Australia is a carbonate ramp that preserves diverse microbial structures which are characteristic of specific depositional environments. These distinctive structures are distributed in five shallow subtidal and two deeper‐water facies in the Oakover area of the Carawine Formation. The shallow subtidal facies are composed of biohermal and bedded stromatolites, centimetre‐scale ridge‐shaped microbialites and wavy‐laminated microbialites. The deeper‐water facies are composed of fenestrate microbialites, planar laminated dolostone and dolostone with rolled‐up microbial laminae. Microbialites in the Carawine Formation lie within a continuum of Archean to Proterozoic microbial facies. Some shallow‐water microbial facies in the Carawine Formation are similar to Proterozoic facies, such as large bioherms internally composed of a variety of stromatolite morphologies. In contrast, fenestrate microbialites grew in quiet subtidal environments and are common in Archean rocks but have not been documented in similar Proterozoic environments. The similarity of shallow‐water facies across the Archean–Proterozoic transition, before and after the oxidation of the atmosphere and surface oceans, indicates that stromatolite growth in shallow subtidal environments was not strongly affected by the chemical changes associated with oxidation of the oceans or by biological responses to those chemical changes. Rather, stromatolite morphology was controlled mostly by the physical environment and the corresponding biological responses to that environment. In contrast, the absence of fenestrate microbialites from Proterozoic deep subtidal environments suggests that the morphology of deep subtidal microbial structures was influenced by chemical or biological changes that occurred in association with oxidation of the surface oceans.

Deep‐water microbialites of the Mesoproterozoic Dismal Lakes Group: microbial growth, lithification, and implications for coniform stromatolites

“…Deep‐water microbialites consist of bioherms of laterally linked cuspate structures (Figs and ) and breccia deposits described as ‘algal plates’ (Kerans & Donaldson, ). Their gross morphology most closely resembles tented and platy microbialite end‐members of the Neoarchean Gamohaan (Sumner, ) and Carawine (Murphy & Sumner, ) formations. In this paper, we use a modification of the terminology developed by Sumner () to describe the components of the Sulky microbialites (Fig.…”

“…Whereas the majority of microbialites occur in well‐lit waters above wave base, both modern and ancient microbialites are also known from deeper‐water environments. Although water depths for these features are difficult to reconstruct in the geologic record, in many cases it is clear that they grew below wave base (typically 15–80 meters in shelf environments) or under otherwise quiet, low‐light or nutrient‐limiting conditions (Sumner, ; Batten et al ., ; Murphy & Sumner, ). These microbialites oftentimes have unusual, tufted to conical morphologies, but like their shallow‐water counterparts, appear to reflect the same interplay of microbial growth, decomposition, and mineral precipitation.…”

Environmental Controls on Photosynthetic Microbial Mat Distribution and Morphogenesis on a 3.42 Ga Clastic-Starved Platform

“…Both sets of structures characteristically grew and were preserved in relatively quiet-water environments, and both produced roll-up structures when eroded by rare higher-energy currents (Sumner, 1997;Murphy and Sumner, 2008;Schrö der et al, 2009). Lack of distinctive bedforms in associated facies or reported grains with known densities and diameters in Neoarchean mats makes a more quantitative comparison currently impossible.…”

“…Laminated and contorted mats that comprise components of fenestrate microbialites from Neoarchean carbonate platform and ramp facies (Sumner, 1997;Murphy and Sumner, 2008;Schrö der et al, 2009) may be the most similar known Archean structures to BRC mats in terms of current activity during mat growth and shear strength. Both sets of structures characteristically grew and were preserved in relatively quiet-water environments, and both produced roll-up structures when eroded by rare higher-energy currents (Sumner, 1997;Murphy and Sumner, 2008;Schrö der et al, 2009).…”

Carbonate fabrics in the modern microbialites of Pavilion Lake: two suites of microfabrics that reflect variation in microbial community morphology, growth habit, and lithification

“…Microbialites provide a record of microbial ecosystems and sediment-organism interactions through much of Earth history, from abundant microbialites in Archean carbonates (e.g., Sumner, 1997;Hofmann et al, 1999;Allwood et al, 2006;Schopf et al, 2007;Murphy & Sumner, 2008) to microbialites forming today in a wide range of environments (e.g., Logan, 1961;Reid et al, 1995;Ferris et al, 1997;Papineau et al, 2005;Myshrall et al, 2010;Andersen et al, 2011;Mata et al, 2012;Burne et al, 2014). Modern microbialites can provide insights into formation and preservation of ancient microbialites and, in particular, how biological processes influence microbial fabrics and microbialite growth.…”