Characteristics of modern carbonate contourite drifts

Gregor P Eberli, Christian Betzler

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

Carbonate environments inhabit the realm of the surface, intermediate and deep currents of the ocean circulation where they produce and continuously deliver material which is potentially deposited into contourite drifts. In the tropical realm, fine-grained particles produced in shallow water and transported off-bank by tidal, wind-driven, and cascading density currents are a major source for transport and deposition by currents. Sediment production is especially high during interglacial times when sea level is high and is greatly reduced during glacial times of sea-level lowstands. Reduced sedimentation on carbonate contourite drifts leads to early marine cementation and hardened surfaces, which are often reworked when current strength increases. As a result, reworked lithoclasts are a common component in carbonate drifts. In areas of temperate and cool water carbonates, currents are able to flow across carbonate producing areas and incorporate sediment directly to the current. The entrained skeletal carbonate particles have variable bulk density and shapes that lower the prediction of transport rates in energy-based transport models, as well as prediction of current velocity based on grain size. All types of contourite drifts known in clastic environments are found in carbonate environments, but three additional drift types occur in carbonates because of local sources and current flow diversion in the complicated topography inherent to carbonate systems. The periplatform drift is a carbonate-specific plastered drift that is nearly exclusively made of periplatform ooze. Its geometry is built by the interaction of along-slope currents and downslope currents, which deliver sediment from the adjacent shallow-water carbonate realm to the contour current via a line source. Because the periplatform drift is plastered on the slopes of the platforms it is also subject to mass gravity flow and large slope failures. At platform edges, a special type of patch drift develops. These hemiconal platform-edge drifts also contain exclusively periplatform ooze but their geometry is controlled by the current around the corner of the platform. At the north-western end of Little and Great Bahama Bank are platform-edge drifts that are over 100 km long and up to 600 m thick. A special type of channel-related drift forms when passages between carbonate buildups or channels within a platform open into deeper water. A current flowing in these channels will entrain material shed from the sediment producing areas. At the channel mouth, the sediment-charged current deposits its sediment load into the deeper basin. With continuous flow, a submarine delta drift is built that progrades into the deep water. The strongly focused current forming the delta drift, is able to rework coarse skeletal grains and clasts, making this type of carbonate drift the coarsest drift type.

Original languageEnglish (US)
Pages (from-to)1163-1191
Number of pages29
JournalSedimentology
Volume66
Issue number4
DOIs
StatePublished - Jun 1 2019

Fingerprint

contourite
carbonate
sediment
ooze
shallow water
deep water
sea level
geometry
carbonate system
cool water
gravity flow
lowstand
slope failure
prediction
cementation
density current
interglacial
clast
bulk density

Keywords

  • Bahamas
  • carbonate contourite drifts
  • delta drift
  • Maldives
  • Marion Drift
  • periplatform drift
  • platform-edge drift
  • Santaren Drift

ASJC Scopus subject areas

  • Geology
  • Stratigraphy

Cite this

Characteristics of modern carbonate contourite drifts. / Eberli, Gregor P; Betzler, Christian.

In: Sedimentology, Vol. 66, No. 4, 01.06.2019, p. 1163-1191.

Research output: Contribution to journalArticle

Eberli, Gregor P ; Betzler, Christian. / Characteristics of modern carbonate contourite drifts. In: Sedimentology. 2019 ; Vol. 66, No. 4. pp. 1163-1191.
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