Gurreholmsdal ice retreat stages and advances

Moraine ridges and other morainic features in Gurreholmsdal, identified by Kelly et al.

Moraines and sample locations

"A 10 Be chronology of lateglacial and Holocene mountain glaciation in the Scoresby Sund region, East Greenland: implications for seasonality during lateglacial time." 
Meredith A. Kelly et al, 2007.
Quaternary Science Reviews xxx (2008) 1–10

https://www.academia.edu/18196712/A_10Be_chronology_of_lateglacial_and_Holocene_mountain_glaciation_in_the_Scoresby_Sund_region_east_Greenland_implications_for_seasonality_during_lateglacial_time


Abstract

Thirty-eight new cosmogenic ( 10 Be) exposure ages from the Scoresby Sund region of east Greenland indicate that prominent moraine sets deposited by mountain glaciers date from 780 to 310 yr, approx- imately during the Little Ice Age, from 11660 to 10 630 yr, at the end of the Younger Dryas cold interval or during Preboreal time, and from 13010 to 11630 yr, during lateglacial time. Equilibrium line altitudes (ELAs) interpreted from lateglacial to Early Holocene moraines indicate summertime cooling between 3.9 and 6.6 deg C relative to today’s value, much less than the extreme Younger Dryas cooling registered by Greenland ice cores (mean-annual temperatures of w15 deg C colder than today’s value). This apparent discrepancy between paleotemperature records supports the contention that Younger Dryas cooling was primarily a wintertime phenomenon. 10 Be ages of lateglacial and Holocene moraines show that mountain glaciers during the Little Ice Age were more extensive than at any other time since the Early Holocene Epoch. In addition, 10 Be ages of lateglacial moraines show extensive reworking of boulders with cosmogenic nuclides inherited from prior periods of exposure, consistent with our geomorphic obser- vations and cosmogenic-exposure dating studies in other Arctic regions.

The moraine ridges on the flanks of the Gurreholm Valley, to the south of the Little Ice Age features, suggest three late glacial stages: one at around 12,000 BP, another around 11,500 BP, and a final one around 11,000 BP.  The last one might be referred to as Early Holocene, from the Preboreal phase -- but it might be more appropriate to think in terms of the Older Dryas and Younger Dryas cold episodes, given the spread of dates presented by the authors.  There are also some anomalous dates  from the oldest moraine ridges, suggesting "inherited ages" and some recycling of materials.

So how do these ridges relate to those of Schuchertdal and Kjove Land.?  It would be logical to relate the higher ridges on the south side of Pythagoras Bjerg to the two older phases in Gurreholmsdal -- when rsl might have been at or above 134 m -- implying in turn that the most recent moraine ridges were formed at the time of the 101m stillstand.

Our colleagues Jimmy Cruickshank and Eric Colhoun noticed in 1962 that the pingos in the middle section of the Schuchert Valley were formed on a substrate of shelly silt and clay beds of marine origin, and that these deposits extended at least as far inland as the Little Ice Age moraine of the Roslin Glacier.  The 100m contour crosses the Schuchert sandur between the Roslin Glacier moraine and the Storgletscher moraine, and  Jimmy and Eric suspected that marine beds run up-valley at least as far as that contour -- again suggesting an association between a 101m stillstand and a significant glacier snout position / retreat stage / advance limit.  The associated moraines are yet to be described.

No doubt further work in the area will confirm the full sequence of events.........