Microbial Facies Research Articles

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

AbstractThe 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.

The role of microbes in reef-building communities of the Cannindah limestone (Mississippian), Monto region, Queensland, Australia

Reefs in the Cannindah Limestone at Old Cannindah Homestead, Monto region, Queensland, are exceptional in Eastern Australian Mississippian (Carboniferous) build-ups because of their largest dimension and differentiated microbial fabrics. Calcimicrobes and microbial carbonates, which represent a marine reefal environment occupied by both corals and sponges, are particularly abundant in the reef framework fabrics compared to other Mississippian build-ups in the world. They contributed significantly to the rigidity of the reefs on a crinoidal bank setting. Metazoans and calcimicrobes coexisted and played different roles in reef construction. Reef-building and cavity-dwelling microbes include Renalcis, Palaeomicrocodium, Girvanella, problematic Aphralysia, Ortonella, Shamovella-like, Rothpletzella-like, Wetheredella-like, and some problematic calcimicrobes, which occur in inter-corallite infillings of fasciculate rugose corals, in thrombolitic textures, in or within deposits between microdigitate stromatolite and laminated microbialites, and in reef cavities. Some reef intervals are entirely formed by Renalcis, Palaeomicrocodium, problematic calcimicrobes, and cement. Girvanella, as an encrusting calcimicrobe, generally bound bioclasts and micrite, or together with cement, formed boundstone. Microbial carbonates, including thrombolites, microencrusters, microdigitate stromatolite, laminated and tabular microbialite, irregular layers of self-encrusting vesicles, and microbial micrite, occur commonly in reef framestone and boundstone. The role of microbes and relevant microbial carbonates in the Cannindah reef limestone highlighted a significant account of microbial facies complexes associated with the Mississippian reefs.

Micritic fabrics define sharp margins of Wenlock patch reefs (middle Silurian) in Gotland and England

Abstract Silurian reefs are well known to comprise frame-building corals, stromatoporoids and algae, but also a range of calcimicrobial components and micritic sediments of possible microbial origin. The margins of Wenlock patch reefs tend to have diffuse edges that grade into the surrounding bedded facies because of talus shed from the reefs. However, portions of patch reefs show sharp-bounded reef margins, with bedded limestones terminating abruptly against the reef edge. Examples of sharp boundaries where the reef comprises only carbonate mudstone-wackestone with poorly-defined gross fabric, and containing no metazoan framework, have been found in Wenlock patch reefs the UK and Gotland. Although in some cases the micrite may demonstrate a peloidal structure, in others there is no clear structure, broadly fitting the aphanitic (structureless) type of fabric found in leiolites (suspected microbial facies that show no structure). The fabrics are interpreted to have been formed by microbial mediation of micrite precipitation as part of reef construction, and are therefore automicrites. In all cases the sharp reef edges indicate coherence of the micritic fabric, interpreted as a lithified wall against which bedded limestones were deposited. This arrangement supports published interpretations of pronounced topography of Wenlock patch reefs, and shows the presence of steep, vertical and, possibly, overhanging reef margins, formed prior to bedded sediment accumulation. Thus, there is likely to have been a time interval between reef formation and deposition of bedded sediments, possibly caused by reef upward growth in transgressive settings, followed by catch-up of bedded limestone deposition.

Stratigraphic and geochemical framework of the Agouron drill cores, Transvaal Supergroup (Neoarchean-Paleoproterozoic, South Africa)

Two long drill cores through the Transvaal Supergroup (Neoarchean-Paleoproterozoic) record the vertical transition from a mixed siliciclastic-carbonate ramp (Schmidtsdrif Subgroup) through the Campbellrand-Malmani carbonate platform (Campbellrand Subgroup) to deeper-water banded iron formations (Asbestos Hills Subgroup). The cores were drilled in proximal (core GKF01) and distal (core GKP01) positions relative to the margin of the Campbellrand-Malmani carbonate platform. Correlation between cores is based on three types of marker horizons: sequence stratigraphic, volcanic/impact and lithologic markers. Several surfaces can be correlated to the platform succession. Gamma-ray data and bulk-rock XRF geochemistry of siliciclastic mudstones and tuff beds support the correlation. Following flooding of a shallow-water carbonate ramp (Boomplaas Formation of Schmidtsdrif Subgroup), deposition of slope carbonates with minor siliciclastic mudstones, chert and banded iron formation (BIF) occurred below storm wave base. Cycles of in situ microbialites and reworked slope carbonates are prominent in both cores. A final transgressive pulse near the top of the succession led to deposition of thick cherts and iron formations across the former platform, slope and basinal areas. Deposition on the slope was controlled by cementation potential in microbial facies and by sediment input, which in turn was linked to variations in platform margin geometry and changes in accommodation space. Results indicate preferred sediment accumulation in the proximal slope position, while chemical sediments were deposited preferentially beyond the reach of carbonate and siliciclastic detrital sediment. Similarly, sediment input and possibly early marine cementation influenced cycles of microbialites and reworked carbonates. Sequence stratigraphic analysis and siliciclastic mudstone geochemistry suggest a possible sea level fall and a change in provenance of the siliciclastic detritus at the transition from the Monteville Formation to the Nauga Formation (basal Campbellrand Subgroup). These changes were probably related to a major depositional hiatus on the platform.

Microbial primary dolomite from a Norian carbonate platform: northern Calabria, southern Italy

AbstractThe origin of fine‐grained dolomite in peritidal rocks has been the subject of much debate recently and evidence is presented here for a microbial origin of this dolomite type in the Norian Dolomia Principale of northern Calabria (southern Italy). Microbial carbonates there consist of stromatolites, thrombolites, and aphanitic dolomites. High‐relief thrombolites and stromatolites characterize sub‐tidal facies, and low‐relief and planar stromatolites, with local oncoids, typify the inter‐supratidal facies. Skeletal remains are very rare in the latter, whereas a relatively rich biota of skeletal cyanophycea, red algae and foraminifera is present in the sub‐tidal facies. Some 75% of the succession consists of fabric‐preserving dolomite, especially within the microbial facies, whereas the rest is composed of coarse dolomite with little fabric preservation. Three end‐members of dolomite replacement fabric are distinguished: type 1 and type 2, fabric retentive, with crystal size <5 and 5–60 μm, respectively; and type 3, fabric destructive, with larger crystals, from 60 to several hundred microns. In addition, there are dolomite cements, precipitated in the central parts of primary cavities during later diagenesis. Microbialite textures in stromatolites are generally composed of thin, dark micritic laminae of type 1 dolomite, alternating with thicker lighter‐coloured laminae of the coarser type 2 dolomite. Thrombolites are composed of dark, micritic clotted fabrics with peloids, composed of type 1 dolomite, surrounded by coarser type 2 dolomite. Marine fibrous cement crusts are also present, now composed of type 2 dolomite. Scanning electron microscope observations of the organic‐rich micritic laminae and clots of the inter‐supratidal microbialites reveal the presence of spherical structures which are interpreted as mineralized bacterial remains. These probably derived from the fossilization of micron‐sized coccoid bacteria and spheroidal–ovoidal nanometre‐scale dwarf‐type bacterial forms. Furthermore, there are traces of degraded organic matter, probably also of bacterial origin. The microbial dolomites were precipitated in a hypersaline environment, most likely through evaporative dolomitization, as suggested by the excess Ca in the dolomites, the small crystal size, and the positive δ18O values. The occurrence of fossilized bacteria and organic matter in the fabric‐preserving dolomite of the microbialites could indicate an involvement of bacteria and organic matter degradation in the precipitation of syn‐sedimentary dolomite.

Upper Dalan Member and Kangan Formation between the Zagros Mountains and offshore Fars, Iran: depositional system, biostratigraphy and stratigraphic architecture

Upper Dalan Member and Kangan Formation between the Zagros Mountains and offshore Fars, Iran: depositional system, biostratigraphy and stratigraphic architecture

Silurian carbonate platforms and extinction events—ecosystem changes exemplified from Gotland, Sweden

Recent and ancient carbonate platforms are major marine ecosystems, built by various carbonate-secreting organisms with different sensitivity for environmental change. For this reason, carbonate platforms are excellent sensors for changes in contemporaneous marine environments. A variety of ecosystem changes in carbonate platforms have previously been recognised in the aftermath of mass extinction events. This paper addresses how two Silurian extinction events among graptolites, conodonts, and pentamerid brachiopods can be related to changes in the style of carbonate production and general evolution of low latitude carbonate platforms in a similar way as previously reported from the major five mass extinctions of the Phanerozoic. Strata formed on Gotland during the Mulde and Lau events share remarkably many similarities but are strikingly different in composition compared to other strata on the island. The event-related strata is characterised by the sudden appearance of widespread oolites, deviating reef composition, flat-pebble conglomerates, abundant micro- and macro-oncoids, stromatolites, and other microbial facies suggesting decreased bioturbation levels in contemporaneous shelf seas. Importantly, these changes can be tied to high-resolution biostratigraphic frameworks and global stable isotope excursions. The anomalous intervals may therefore be searched for elsewhere in order to test their regional or global significance.

Permian-Triassic Boundary Sections from Shallow-Marine Carbonate Platforms of the Nanpanjiang Basin, South China: Implications for Oceanic Conditions Associated with the End-Permian Extinction and Its Aftermath

Other| April 01, 2003 Permian–Triassic Boundary Sections from Shallow-Marine Carbonate Platforms of the Nanpanjiang Basin, South China: Implications for Oceanic Conditions Associated with the End-Permian Extinction and Its Aftermath DANIEL J. LEHRMANN; DANIEL J. LEHRMANN 1Department of Geology, University of Wisconsin-Oshkosh, Oshkosh, WI 54901, lehrmann@uwosh.edu Search for other works by this author on: GSW Google Scholar JONATHAN L. PAYNE; JONATHAN L. PAYNE 2Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138 Search for other works by this author on: GSW Google Scholar SHARON V. FELIX; SHARON V. FELIX 3The RETEC Group, Inc. RETEC, 5000 E. Spring St., Ste 250, Long Beach, CA 90815 Search for other works by this author on: GSW Google Scholar PETER M. DILLETT; PETER M. DILLETT 4Department of Geology, University of Kansas, Lawrence, KS 66045 Search for other works by this author on: GSW Google Scholar HONGMEI WANG; HONGMEI WANG 5Guizhou Bureau of Geology and Mineral Resources, Guiyang, Guizhou, P.R.C Search for other works by this author on: GSW Google Scholar YOUYI YU; YOUYI YU 5Guizhou Bureau of Geology and Mineral Resources, Guiyang, Guizhou, P.R.C Search for other works by this author on: GSW Google Scholar JIAYONG WEI JIAYONG WEI 5Guizhou Bureau of Geology and Mineral Resources, Guiyang, Guizhou, P.R.C Search for other works by this author on: GSW Google Scholar PALAIOS (2003) 18 (2): 138–152. https://doi.org/10.1669/0883-1351(2003)18<138:PBSFSC>2.0.CO;2 Article history accepted: 22 Aug 2002 first online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation DANIEL J. LEHRMANN, JONATHAN L. PAYNE, SHARON V. FELIX, PETER M. DILLETT, HONGMEI WANG, YOUYI YU, JIAYONG WEI; Permian–Triassic Boundary Sections from Shallow-Marine Carbonate Platforms of the Nanpanjiang Basin, South China: Implications for Oceanic Conditions Associated with the End-Permian Extinction and Its Aftermath. PALAIOS 2003;; 18 (2): 138–152. doi: https://doi.org/10.1669/0883-1351(2003)18<138:PBSFSC>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyPALAIOS Search Advanced Search Abstract Permian-Triassic boundary (PTB) sections from isolated carbonate platforms in the Nanpanjiang Basin of south China contain Upper Permian skeletal packstones with diverse open-marine fossils overlain by a 7–15 m thick boundary horizon composed of calcimicrobial framestone constructed by globular to tufted, calcified cyanobacteria similar to Renalcis. The framestone contains interbeds of lime-grainstone with abundant thin-shelled bivalves and brachiopods. The overlying Lower Triassic strata contain microgastropod lime-packstones followed by a thick succession of thin-bedded lime-mudstones.The PTB event horizon is interpreted to occur at the top of the packstone containing diverse, open-marine fauna and Palaeofusulina and coincident with the abrupt change to calcimicrobial framestone lacking Permian macrofossils. The conformable biostratigraphic boundary occurs at the first appearance of Hindeodus parvus within the basal meter of the calcimicrobial framestone.Intensively studied PTB sections in south China, such as the GSSP at Meishan, primarily are condensed sections from deep-water, basin environments that contain a thin (< 30 cm) boundary horizon of claystone and lime-mudstone or marl. The sections reported herein are fundamentally different in that they consist of shallow-marine carbonate facies, contain a thick boundary horizon composed of calcimicrobial framestone, and lack evidence of an abrupt shift in depositional environment or water depth. The calcimicrobial framestone boundary horizon occurs in all of the isolated carbonate platforms in the Nanpanjiang Basin. A similar microbial facies has been found in the basal Triassic H. parvus zone in the Sichuan Basin and in Japan. Distribution of the calcimicrobial framestone suggests that it may represent an anomalous oceanic event that affected a vast area of the equatorial eastern Tethys and Panthalassa during and/or immediately following the end-Permian mass extinction. The persistence of similar calcimicrobial framestone horizons into the Upper Scythian suggests that detrimental environmental conditions associated with the extinction persisted until the end of the Scythian. Further study of these sections promises to provide constraints on causes of the extinction and the environments in the aftermath. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Lowermost Triassic (Griesbachian) microbial bindstone-cementstone facies, southwest Japan

On the basis of the lithostratigraphy and microscopic characters, the paper describes the facies interpretation of the upper Upper Permian (Changhsingian) and Lower Triassic (Griesbachian to Spathian) carbonates of southwest Japan, with a focus upon the lowermost Triassic (Griesbachian) microbial bindstone-cementstone. We emphasize the significant sediment-binding and stabilizing agencies of microbes chiefly of cyanobacteria along with the syndepositional cementation for the carbonate deposition on a Panthalassan buildup in a period of the Scythian reef gap. Cyanobacteria flourished as postmass extinction disaster forms in the beginning of the Triassic. The Griesbachian microbial bindstone-cementstone we describe comprises the oldest known Triassic microbial facies.

Bacteriological Survey on Ready-to-use Sliced Carrots

The aerobic colony counts (ACC) and total and faecal coliforms (TC and FC) were detected in retail packs of ready-to-use sliced carrots produced by four different manufacturers. High values of FC, found in 65% of the samples, demonstrated the marginal quality of these products. In order to identify the sites of major contamination, carrot samples were taken during various phases of the processing of ready-to-use sliced carrots from a semi-industrialized production plant. Washing with chlorinated water (free chlorine level of 20 mg/l) with a contact time of 20 min did not change the ACC and the microbial facies already present in the vegetables before processing, but lowered the quantity of coliforms. However, these organisms increased in the following cutting phase. The Enterobacteriaceae found in this study are common in soil and water and do not necessarily represent a public health concern.