This is the map published by Danny McCarroll and others in 2010 to show the location of the sites used for cosmogenic dating of rock surfaces. Click to enlarge. Below is my map of the Pembrokeshire Devensian limit. According to this map ALL of the sampled sites in Pembrokeshire lie within the glacial limit and were thus subject to glacial erosion and/or glacial protection from cosmic radiation.
1 comment:
I got this comment from Lionel Jackson yesterday -- I'm sure he will not mind sharing it:
I am going into the GSC office tomorrow and will print out the QSR paper and read it and get back to you. At first glance, I believe that you have valid points. The coastal ages show significant inheritance and could have had a similar exposure history to the tors. Differential glacial erosion could have generated the age difference (thin ice over the tors vs. extensive erosion along the coast). A two isotope system could test this hypothesis (10Be/26Al) but these isotopes form in quartz and much quartz is required. These mafic rocks likely do not have much if any. It would be better to date erratics than the bedrock in the upland setting if they exist and are > m3 in volume. Cosmogenic dating requires good control on the exposure and erosional history of the surface investigated. There are simply too many unknown variables here. I will have to come to Wales to see this for myself someday!
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