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The AAPG/Datapages Combined Publications Database

Journal of Sedimentary Research (SEPM)

Abstract


Journal of Sedimentary Research
Vol. 87 (2017), No. 3. (March), Pages 312-323
Current Ripples
DOI: 10.2110/jsr.2017.21

Deep-Marine Pseudo Dune Cross-Stratification—Similar, But Completely Different

R.W.C. Arnott, O. Al-Mufti

Abstract

High-angle cross-stratification related to the downflow migration of subaqueous dunes is common in the continental sedimentary record but is puzzlingly uncommon in deep-marine strata. In deep-marine rocks of the Windermere turbidite system, however, several centimeters to decimeters-thick, high-angle cross-stratified sets that resemble dune cross-stratification are commonly observed, but in an upflow direction characteristically transition abruptly at the brinkpoint into planar stratification. Typically, the transition coincides with an abrupt deepening of a basal scour, and into and onto which a progressively lengthening and commonly thickening wedge of high-angle cross-strata downlap. Moreover, the several-meters to several-decameters-long sets are longitudinally discontinuous, even though they typically sharply overlie an areally expansive sandy substrate and evidence of scour by a younger event is generally absent. Instead these strata are interpreted to represent the flat-topped, steep-fronted, prograding fills of isolated scours, and therefore in spite of resembling the cross-stratification formed by the migration of subaqueous dunes, dunes were not involved in deposition of these strata.


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