Australia: The Land Where Time Began

A biography of the Australian continent 

Submarine End Moraines on the Continental Shelf Off NE Greenland - Implications for Lateglacial Dynamics

During the RV Polarstern ARC-XXIV/3 leg in 2009 an acoustic survey was carried out offshore of NE Greenland. Ridges of sediment are clearly shown by the data set acquired by this survey in an area of about 18 x 9 km, at depths of between 270-350 m. In profile, steep slopes towards the northwest and gentle slopes towards the southeast characterise most of these ridges which are 2.5-9 km long, 50-250 m wide and 5-25 m high. As imaged by parametric echo-sounding data, the internal structure of the ridges is shown to be positive sedimentation features rather than remnant structures of erosion. The authors¹ consider these ridges to be end moraines of the Westwind ice stream that has been reported (Evans et al., 2009) as they are of an arcuate shape, have a joint orientation and are positioned within the Westwind Trough on a basal till which extends further to the east, marine geophysical evidence of expansion and flow in the past of the Greenland Ice Sheet across the northeast Greenland continental shelf. (Journal of Quaternary Science (2008), doi: 10.1002/jqs.1231.). The authors¹ have interpreted these end moraines to have been formed by short-lived advances of the ice front during an overall contraction of the ice margin, based on their hydro-acoustic data.  They could have also been deposited at times when the grounding line halted, comparable to De Geer moraines, though their morphological characteristics differ slightly from those of most De Geer moraines that have been published. A thin sedimentary drape that indicates timing between Lateglacial and Early Holocene can infer the ages of moraine deposition. The authors¹ suggest this set of end moraines is direct evidence of a dynamic behaviour of the marine-based ice stream at the time of the last deglaciation on the NE Greenland shelf.

Sources & Further reading

1. Winkelmann, Daniel, Wilfried Jokat, Laura Jensen, and Hans-Werner Schenke. "Submarine End Moraines on the Continental Shelf Off Ne Greenland – Implications for Lateglacial Dynamics." Quaternary Science Reviews 29, no. 9–10 (5// 2010): 1069-77.