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.