Toggle Main Menu Toggle Search

Open Access padlockePrints

Sedimentary architecture of large-scale, jökulhlaup-generated, ice-block obstacle marks: Examples from Skeiðarársandur, SE Iceland

Lookup NU author(s): Dr Matthew Burke, Professor Andrew RussellORCiD


Full text for this publication is not currently held within this repository. Alternative links are provided below where available.


During glacial outburst floods (jokulhlaups) large ice-blocks are often released from the glacier margin. Ice-blocks ground at points of flow deceleration, generating distinctive patterns of scour and deposition scaled to the obstacle size. The large-scale ice-block obstacle marks produced within the proglacial zone are diagnostic of jokulhlaups. We use ground-penetrating radar (CPR) to investigate the sedimentary architecture of ice-block obstacle marks generated by the November 1996 jokulhlaup at Skeidararjokull, Iceland. The CPR data reveal a varied sedimentary architecture, interpreted to suggest that ice-block obstacle mark sedimentology is controlled by flow conditions, sediment supply, and whether ice blocks are deposited in isolation or as a cluster. Following ice-block grounding, deflection of flow down and away from the obstacle develops horseshoe vortices that maintain a non-depositional hollow around the obstacle, whilst continued outwash deposition away from the obstacle raises the level of the surrounding sandur. Where ice-blocks ground early during the jokulhlaup, hollows are infilled with foreset beds at the up-flow end and backset beds (antidune) distally. However, where ice-blocks ground on the waning stage when sediment flux is reduced, antidunes are not preserved and the hollow is infilled with low-angle foreset beds. In both cases the lee-side shadow ridge is composed of pseudo-anticlinal beds proximal to the obstacle (where shed vortices are strong) and plane beds distally (where flows converge and the shed vortices weaken). Where flow parallel ice-block clusters develop, the grounding of smaller ice-blocks in the lee of the initial obstacle results in only limited shadow ridge aggradation. These data provide improved insight into the controls on ice-block obstacle mark sedimentary architecture and allow identification of high-magnitude jokulhlaups in the sedimentary record. (C) 2010 Elsevier B.V. All rights reserved.

Publication metadata

Author(s): Burke MJ, Woodward J, Russell AJ

Publication type: Article

Publication status: Published

Journal: Sedimentary Geology

Year: 2010

Volume: 227

Issue: 1-4

Pages: 1-10

Print publication date: 18/03/2010

ISSN (print): 0037-0738

ISSN (electronic):

Publisher: Elsevier


DOI: 10.1016/j.sedgeo.2010.03.001


Altmetrics provided by Altmetric