skip to main content
Language:
Search Limited to: Search Limited to: Resource type Show Results with: Show Results with: Search type Index

Upslope-Migrating Bedforms In A Proglacial Sandur Delta: Cyclic Steps From River-Derived Underflows?

Journal of sedimentary research, 2016-02, Vol.86 (2), p.113-123 [Peer Reviewed Journal]

Distributed under a Creative Commons Attribution 4.0 International License ;ISSN: 1527-1404 ;EISSN: 1938-3681 ;DOI: 10.2110/jsr.2016.4

Digital Resources/Online E-Resources

Citations Cited by
  • Title:
    Upslope-Migrating Bedforms In A Proglacial Sandur Delta: Cyclic Steps From River-Derived Underflows?
  • Author: Dietrich, Pierre ; Ghienne, Jean-François ; Normandeau, Alexandre ; Lajeunesse, Patrick
  • Subjects: Earth Sciences ; Sciences of the Universe ; Stratigraphy
  • Is Part Of: Journal of sedimentary research, 2016-02, Vol.86 (2), p.113-123
  • Description: Backstepping cross-strata on steep foresets of a Gilbert-type proglacial fluviodeltaic system are ascribed to cyclic steps and other associated supercritical bedforms. They provide insight into how sandur river flows transition into the marine realm. These sedimentary structures are located on steep foresets (up to 176) with corresponding top-lying, flat-based topsets in an upper Pleistocene delta on the North Shore of the Gulf of St. Lawrence, Québec, Canada. Packages of backstepping cross strata of sand and gravel, lying in the lower part of the delta front outcrop, are organized in 10-20 m spaced pseudo-foresets with a mean slope of 11-126 seawards. Backstepping strata include frequent internal erosion surfaces that onlap upslope on pseudo-foresets and are interpreted as cyclic steps. Narrow, deep, and asymmetrical scours and upslope-climbing cross beds are interpreted as chutes-and-pools and antidunes respectively. Very shallow (, 15 m) depositional paleo-bathymetry is inferred from the preservation of the delta brink. The well-organized stratal pattern in cyclic step to antidune deposits indicates relatively steady and uniform flow patterns. There is insufficient distance for a headscarp large enough to transform to the volume of observed accreted sands or for a flow transformation from a gravitational collapse to net-depositional cyclic steps. These deposits are sandier than the topsets beds and are thus not derived from them, but rather correspond to topset erosional surfaces. The development of cyclic steps from hyperpycnal flows was likely enhanced by tidal drawdown processes. The resulting sediment-laden supercritical flows plunged inertially and evolved into an underflow that generated the cyclic steps on the upper foresets. The cyclic steps have a high aspect ratio and represent an end member of coarse-grained sediment deposited on steep slopes, in contrast to low-gradient, low-aspect-ratio muddy deposits.
  • Publisher: Society for Sedimentary Geology
  • Language: English
  • Identifier: ISSN: 1527-1404
    EISSN: 1938-3681
    DOI: 10.2110/jsr.2016.4
  • Source: Hyper Article en Ligne (HAL) (Open Access)
Back to results list
INSPIRE LIBRARY - TON DUC THANG UNIVERSITY (84-028) 37 755 057 Feedback
19 Nguyen Huu Tho St. Dist.7, HCM thuvien@tdtu.edu.vn

Copyright © 2017 INSPIRE LIBRARY - TON DUC THANG UNIVERSITY

Searching Remote Databases, Please Wait