Glacier entrainment

This is a very intriguing image from Nick Cobbing of the ice sheet edge somewhere in West Greenland.  You don't often see ice edges as clearly defined and as clean as this -- with an accumulated litter of morainic boulders that have simply dropped out of the ice front.  The stratification (probably old summer ablation surfaces) is unusually regular and tidy, with hardly any glacitectonic deformation.  And scattered through these layers of ice there are stones and boulders -- if these were in seafloor varved deposits they would be called dropstones.  Where did they come from?  They appear not to have been entrained in the usual way, by plucking of bedrock outcrops on the glacier bed, since there are no shear-planes or other structures.

Or have I got this all wrong? Are we looking at basal accretion of one regelation ice layer after another, with boulders and stones picked up in that way by freezing-on at the bed?  In other words, is this part of the ice front made up of ice layers that have accumulated from below, thickening the glacier from the bottom up?  That does happen, but I have never seen evidence of it on this scale before.

For the last 60 years or more, glaciologists have described and theorized on regelation ice layers, but generally it has been assumed that such layers accumulate beneath warm-based glaciers, with melting episodes and freezing-on episodes alternating, presumably on a seasonal or annual basis.  Here on Bylot Island the glaciers have to be polar or cold-based, making the matter more intriguing.

Maybe a glaciologist will give us a comment.....

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PS. Just noticed that before today, I have published 2500 posts on this blog.  I hadn't realised that I have been working so hard or spent so much time thinking aloud.....

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Here are some more images from the Glaciers Online web site, all featuring basal ice features at the edge of Fountain Glacier on Bylot Island.  This is a cold-based "polar glacier":

https://www.swisseduc.ch/glaciers/bylot

These are all images of stratified or  layered basal ice with associated glacitectonic structures and enclosures of cobbles and boulders.  The exception is the lowest part of the bottom photo, which shows stratified basal ice overlying a bed of "meltout till".