Lower Cretaceous smarl turbidites of the Argo Abyssal Plain, Indian Ocean

Proceedings of the Ocean Drilling Program: Scientific Results 123-5
Edited by: Sondra K. StewartDiana Kennett, and Elsa K. Mazzullo



Sediments recovered during Ocean Drilling Program (ODP) Leg 123 from the Argo Abyssal Plain (AAP) consist largely of turbidites derived from the adjacent Australian continental margin. The oldest abundant turbidites are Valanginian-Aptian in age and have a mixed (smarl) composition; they contain subequal amounts of calcareous and siliceous biogenic components, as well as clay and lesser quartz. Most are thin-bedded, fine sand to mud-sized, and best described by Stow and Piper's model (1984) for fine-grained biogenic turbidites. Thicker (to 3 m), coarser-grained (medium-to-coarse sand-sized) turbidites fit Bouma's model (1962) for sandy turbidites; these generally are base-cut-out (BCDE, BDE) sequences, with B-division parallel lamination as the dominant structure. Parallel laminae most commonly concentrate quartz and/or calcispheres vs. lithic clasts or clay, but distinctive millimeter to centimeter-thick, radiolarian-rich laminae occur in both fine and coarse-grained Valanginian-Hauterivian turbidites.

AAP turbidites were derived from relatively deep parts of the continental margin (outer shelf, slope, or rise) that lay below the photic zone, but above the calcite compensation depth (CCD). Biogenic components are largely pelagic (calcispheres, foraminifers, radiolarians, nannofossils); lesser benthic foraminifers are characteristic of deep-water (abyssal to bathyal) environments. Abundant nonbiogenic components are mostly clay and clay clasts; smectite is the dominant clay species, and indicates a volcanogenic provenance, most likely the Triassic-Jurassic volcanic suite exposed along the northern Exmouth Plateau.

Lower Cretaceous smarl turbidites were generated during eustatic lowstands and may have reached the abyssal plain via Swan Canyon, a submarine canyon thought to have formed during the Late Jurassic. In contrast to younger AAP turbidites, however, Lower Cretaceous turbidites are relatively fine-grained and do not contain notably older reworked fossils. Early in its history, the northwest Australian margin provided mainly contemporaneous slope sediment to the AAP; marginal basins adjacent to the continent trapped most terrigenous detritus, and pronounced canyon incisement did not occur until Late Cretaceous and, especially, Cenozoic time.

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Publication type Report
Publication Subtype Organization Series
Title Lower Cretaceous smarl turbidites of the Argo Abyssal Plain, Indian Ocean
Series title Proceedings of the Ocean Drilling Program: Scientific Results
Series number 123
Chapter 5
DOI 10.2973/odp.proc.sr.123.154.1992
Volume 123
Year Published 1992
Language English
Publisher Ocean Drilling Program, Texas A&M University
Publisher location College Station, TX
Contributing office(s) Alaska Science Center
Description 25 p.
First page 111
Last page 135
Public Comments Volume topic: Argo Abyssal Plain/Exmouth Plateau, covering Leg 123 of the cruises of the Drilling Vessel JOIDES Resolution, Singapore, Republic of Sing., to Singapore, Republic of Sing., Sites 765-766, 28 August 1988 - 1 November 1988
Other Geospatial Argo Abyssal Plain
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