|Brian Whalley and Darrel Swift walking down a possible meltwater channel on the moor above Shatton. In the foreground another channel runs parallel to the one they are walking down.|
Glacial sands and gravels on the top of Abney Moor?After a bumpy ride in the back of one of Chris Clark's Legendary Land Rovers we reached our second site, at the top of Abney Moor, where sands and gravels associated with the last ice age had been previously reported in a geological memoir. We were particularly excited about this as glacial sands and gravels so high up (400 m) would mean a similar ice-surface elevation, and we could also date the sands to get an age on their formation. We spent a good deal of time trying to find these sands and gravels using a hand auger (tool used to bore a hole into the ground and collect a sample of the underlying sediment), but could only find a thick clay/silt unit overlain by peat. The significance of the site is explained by Dr Stephen Livingstone and the augering process demonstrated by Calvin Shackleton (with help from Jeremy Ely) in the video below.
On the walk back to Chris's farm for lunch we stopped to look at a couple of channel-forms identified from the airborne imagery. We were able to rule these out as candidates for meltwater channels, because their dimensions and surroundings were too similar to that produced by human activity (see previous section on meltwater channels).
Moraines at Glossop?
After admiring the animals and eating our sandwiches at Chris Clark's farm we headed off over the Snake Pass to look for evidence of moraines (ridges of sediment deposited by glaciers, often at their snout or along their sides). On the walk out Dr Darrel Swift spotted some erratics in a dry-stone wall (explained in the video below) that were likely to have been brought over by the main British-Ice Sheet, which infringed upon the western side of the Peak district around Glossop.
We were able to discount a number of ridges northeast of Glossop that seemed to be geologically controlled (i.e. due to differences in rock type). This was confirmed by the existence of old pits on the surface of one of the ridges, which would have been used to quarry bedrock (rather than glacial sediments). And similarly, some of the ridges that looked like moraines on the airborne imagery actually turned out to be landslide deposits upon closer inspection. With our spirits dampened somewhat by the lack of glacial features we headed back to the cars. But when we looked back at where we had just been, we identified what looked like a large moraine. We'd been standing on it!
The day ended with a lengthy discussion in the pub where we evaluated all the sites again, given the day's discoveries. We decided that there are tantalizing clues which seem to point towards a former glaciation, although the picture is muddied by post-glacial processes, and we still don't know how old the features are. A further recce of other possible sites is required; along with more detailed field measurements and collection of dateable material, to try to constrain the timing of formation of the features we've observed today.
Written by Calvin Shackleton and Stephen Livingstone