Quantitative compaction trends of Miocene to Holocene carbonates off the west coast of Australia

Eun Young Lee (Corresponding author), Michelle Kominz, Lars Reuning, Stephen Gallagher, Hideko Takayanagi, Takeshige Ishiwa, Wolfgang Knierzinger, Michael Wagreich

Publications: Contribution to journalArticlePeer Reviewed

Abstract

In this paper, we describe porosity variations in Miocene to Holocene carbonates off the west coast of Australia and assess their compaction trends. The porosity values were measured using discrete samples of Sites U1459–U1464 obtained by the International Ocean Discovery Program Expedition 356. The carbonate deposits have been influenced by a range of textures and diagenetic conditions throughout a nearly continuous sequence of geological ages from the Miocene to Holocene and at core depths from 0 to 1100 m below the seafloor. The collected samples were mostly grainstone, packstone, wackestone and mudstone textures. Dolostones and dolomitic carbonates were described at the Miocene intervals. Compaction trends were estimated exponentially and linearly based on cored sites, carbonate textures and dominant mineralogies (dolomite, calcite/aragonite). At all six sites, porosity distribution and reduction were generally depth-dependent. The porosity converged to about 30% between 750 and 1100 m, which suggests that the carbonates were close to the densest packing by mechanical compaction at a burial depth of ∼750 m. The porosity deviations are associated with textures and dominant mineralogies. Increasing mud content from grainstone to mudstone is a controlling factor for initial porosity and porosity reduction rate. Dolomitisation, dolomitic cementation, aragonite needle-rich mud and non-skeletal grains cause deviations from the depth-dependent compaction trends. Reflux-related cementation generally decreases porosity in Miocene dolomitic intervals. Higher porosity values of the Quaternary wackestone and mudstone at Site U1461 resulted from the presence of aragonite needle-rich mud hosting abundant micropores and from a high sedimentation rate. The occurrence of non-skeletal grains, such as ooids and peloids, as well as occasional meteoric exposure led to porosity inversion, occluding interparticle permeability and the creation of moldic pores. • KEY POINTS • Porosity variations of Miocene–Holocene carbonates off the west Australian coast are primarily depth-dependent. • Mechanical compaction affected porosity reduction down to a value of ∼30% at a burial depth of ∼750 m. • Differences in texture-based compaction trends were affected by increasing mud content. • Major porosity deviations are associated with dolomitisation, dolomitic cementation, aragonite needle-rich mud and non-skeletal grains.
Original languageEnglish
Pages (from-to)1149-1161
Number of pages13
JournalAustralian Journal of Earth Sciences
Volume68
Issue number8
Early online date20 May 2021
DOIs
Publication statusPublished - 2021

Austrian Fields of Science 2012

  • 105125 Petrophysics
  • 105116 Mineralogy
  • 105121 Sedimentology

Keywords

  • carbonate
  • porosity
  • compaction
  • Australia
  • dolomite
  • aragonite
  • POROSITY
  • PERMEABILITY
  • IODP Sites U1459-U1464
  • compaction trend
  • Roebuck Basin
  • Perth Basin
  • carbonates
  • offshore Western Australia
  • RESERVOIRS
  • OLIGOCENE
  • CONTINENTAL-MARGIN
  • EVOLUTION
  • BASIN
  • CRETACEOUS SUBSIDENCE
  • DIAGENESIS
  • Northern Carnarvon Basin
  • DEPTH
  • IODP Sites U1459–U1464

Cite this