Deposition and diagenesis of marine oncoids: Implications for development of carbonate porosity

Chelsea L. Pederson, Donald F. McNeill, James Klaus, Peter K Swart

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Microbially mediated carbonates form in numerous environments and produce a range of lithologic fabrics and textures. While the environmental and biological factors controlling microbial carbonate precipitation are becoming more established, the influence of precursor microbial textures on diagenetic processes is less understood. Here we describe microbial oncolites from Maré, New Caledonia, to assess their formation, textures, and subsequent diagenetic alteration. Calcified filaments and sheets are interpreted as microbial-mat constituents (bacterial sheaths and EPS sheets) within a constructive micritic cortex of uniform crystal size (5 10 mm) and shape formed around a nucleus grain. Thin-section analyses show trapped and bound grain inclusions and irregular laminations within the cortex, also consistent with a microbial origin. The combination of a dense micrite cortex, subrounded shape, and irregular laminations are consistent with oncoid formation under periodic wave agitation in a back-reef setting. The Maré oncolites also display an unexpected pseudomorphic stabilization of the nucleus grains and cortex, likely due to the original mineralogy and low permeability of the cortex micrite. To our knowledge, this is the first example of microbial coatings leading to pseudomorphic stabilization of aragonite and high-Mg calcite skeletal grains. This textural preservation lies in stark contrast to the extensive dissolution and moldic porosity found outside the oncolite beds and common to many tropical shallow-water carbonates. These findings have implications for development of meteoric porosity, the interpretation of λ13C values in marine carbonates, and potential controls on fluid flow.

Original languageEnglish (US)
Pages (from-to)1323-1333
Number of pages11
JournalJournal of Sedimentary Research
Volume85
Issue number11
DOIs
StatePublished - Nov 1 2015

Fingerprint

diagenesis
porosity
carbonate
micrite
texture
lamination
oncolite
stabilization
microbial mat
aragonite
thin section
fluid flow
coating
mineralogy
reef
shallow water
calcite
dissolution
permeability
crystal

ASJC Scopus subject areas

  • Geology

Cite this

Deposition and diagenesis of marine oncoids : Implications for development of carbonate porosity. / Pederson, Chelsea L.; McNeill, Donald F.; Klaus, James; Swart, Peter K.

In: Journal of Sedimentary Research, Vol. 85, No. 11, 01.11.2015, p. 1323-1333.

Research output: Contribution to journalArticle

@article{9710e1f609124df2a8707c0a696ae694,
title = "Deposition and diagenesis of marine oncoids: Implications for development of carbonate porosity",
abstract = "Microbially mediated carbonates form in numerous environments and produce a range of lithologic fabrics and textures. While the environmental and biological factors controlling microbial carbonate precipitation are becoming more established, the influence of precursor microbial textures on diagenetic processes is less understood. Here we describe microbial oncolites from Mar{\'e}, New Caledonia, to assess their formation, textures, and subsequent diagenetic alteration. Calcified filaments and sheets are interpreted as microbial-mat constituents (bacterial sheaths and EPS sheets) within a constructive micritic cortex of uniform crystal size (5 10 mm) and shape formed around a nucleus grain. Thin-section analyses show trapped and bound grain inclusions and irregular laminations within the cortex, also consistent with a microbial origin. The combination of a dense micrite cortex, subrounded shape, and irregular laminations are consistent with oncoid formation under periodic wave agitation in a back-reef setting. The Mar{\'e} oncolites also display an unexpected pseudomorphic stabilization of the nucleus grains and cortex, likely due to the original mineralogy and low permeability of the cortex micrite. To our knowledge, this is the first example of microbial coatings leading to pseudomorphic stabilization of aragonite and high-Mg calcite skeletal grains. This textural preservation lies in stark contrast to the extensive dissolution and moldic porosity found outside the oncolite beds and common to many tropical shallow-water carbonates. These findings have implications for development of meteoric porosity, the interpretation of λ13C values in marine carbonates, and potential controls on fluid flow.",
author = "Pederson, {Chelsea L.} and McNeill, {Donald F.} and James Klaus and Swart, {Peter K}",
year = "2015",
month = "11",
day = "1",
doi = "10.2110/jsr.2015.77",
language = "English (US)",
volume = "85",
pages = "1323--1333",
journal = "Journal of Sedimentary Research",
issn = "1527-1404",
publisher = "SEPM Society for Sedimentary Geology",
number = "11",

}

TY - JOUR

T1 - Deposition and diagenesis of marine oncoids

T2 - Implications for development of carbonate porosity

AU - Pederson, Chelsea L.

AU - McNeill, Donald F.

AU - Klaus, James

AU - Swart, Peter K

PY - 2015/11/1

Y1 - 2015/11/1

N2 - Microbially mediated carbonates form in numerous environments and produce a range of lithologic fabrics and textures. While the environmental and biological factors controlling microbial carbonate precipitation are becoming more established, the influence of precursor microbial textures on diagenetic processes is less understood. Here we describe microbial oncolites from Maré, New Caledonia, to assess their formation, textures, and subsequent diagenetic alteration. Calcified filaments and sheets are interpreted as microbial-mat constituents (bacterial sheaths and EPS sheets) within a constructive micritic cortex of uniform crystal size (5 10 mm) and shape formed around a nucleus grain. Thin-section analyses show trapped and bound grain inclusions and irregular laminations within the cortex, also consistent with a microbial origin. The combination of a dense micrite cortex, subrounded shape, and irregular laminations are consistent with oncoid formation under periodic wave agitation in a back-reef setting. The Maré oncolites also display an unexpected pseudomorphic stabilization of the nucleus grains and cortex, likely due to the original mineralogy and low permeability of the cortex micrite. To our knowledge, this is the first example of microbial coatings leading to pseudomorphic stabilization of aragonite and high-Mg calcite skeletal grains. This textural preservation lies in stark contrast to the extensive dissolution and moldic porosity found outside the oncolite beds and common to many tropical shallow-water carbonates. These findings have implications for development of meteoric porosity, the interpretation of λ13C values in marine carbonates, and potential controls on fluid flow.

AB - Microbially mediated carbonates form in numerous environments and produce a range of lithologic fabrics and textures. While the environmental and biological factors controlling microbial carbonate precipitation are becoming more established, the influence of precursor microbial textures on diagenetic processes is less understood. Here we describe microbial oncolites from Maré, New Caledonia, to assess their formation, textures, and subsequent diagenetic alteration. Calcified filaments and sheets are interpreted as microbial-mat constituents (bacterial sheaths and EPS sheets) within a constructive micritic cortex of uniform crystal size (5 10 mm) and shape formed around a nucleus grain. Thin-section analyses show trapped and bound grain inclusions and irregular laminations within the cortex, also consistent with a microbial origin. The combination of a dense micrite cortex, subrounded shape, and irregular laminations are consistent with oncoid formation under periodic wave agitation in a back-reef setting. The Maré oncolites also display an unexpected pseudomorphic stabilization of the nucleus grains and cortex, likely due to the original mineralogy and low permeability of the cortex micrite. To our knowledge, this is the first example of microbial coatings leading to pseudomorphic stabilization of aragonite and high-Mg calcite skeletal grains. This textural preservation lies in stark contrast to the extensive dissolution and moldic porosity found outside the oncolite beds and common to many tropical shallow-water carbonates. These findings have implications for development of meteoric porosity, the interpretation of λ13C values in marine carbonates, and potential controls on fluid flow.

UR - http://www.scopus.com/inward/record.url?scp=84948948631&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84948948631&partnerID=8YFLogxK

U2 - 10.2110/jsr.2015.77

DO - 10.2110/jsr.2015.77

M3 - Article

AN - SCOPUS:84948948631

VL - 85

SP - 1323

EP - 1333

JO - Journal of Sedimentary Research

JF - Journal of Sedimentary Research

SN - 1527-1404

IS - 11

ER -