My favourite map

This is my contribution to the Accretionary Wedge geoblog festival, number 43: My Favourite Geological Illustration. You can read all about it at In the Company of Plants and Rocks. 

I was struggling for inspiration on this latest Accretionary Wedge, but this was solved by Matt Hall’s post over at Agile Geoscience, where he talks about a map he produced as part of his degree. Geological maps have captured my imagination since a very early age. I’ve spend many an hour poring over the geological map of the British Isles (particularly the Northern sheet) but of course I had a modern copy, not the William Smith original.

I have hidden away somewhere a very similar undergraduate map to Matt’s but I won’t steal his idea outright. I have a bigger map produced as part of my PhD thesis somewhere as well, but instead I want to talk about someone else’s map.

My PhD field area was in Connemara in the west of Ireland, which is an extremely well-known piece of Geology. A fantastic detailed map was published in the 1990s but is based on decades of study by geologists from Glasgow University, Bernard Leake and Geoff Tanner. It is of course in copyright and for sale, but I include an impressionistic photo. I’m sure the Royal Irish Academy will not disapprove.

I’m tempted to rhapsodise at length at the Geology shown by this map, but I’ll be brief. It is a small area (top to bottom about 20km) but it contains such a lot! Such as: evidence of Precambrian glaciations; two overlapping phases of metamorphism, from greenschist to granulite; three major phases of folding; three suites of igneous intrusions, one syntectonic, two post; three tectonic terranes; two terrane boundaries, one a thrust the other an extensional detachment complete with syn-deformational sediments; some world famous marble.  Oh, and some sediments around the edge.

One of the greatest pleasures of my PhD research was meeting and disputing with Geoff Tanner and Bernard Leake, standing on the rocks themselves and referring to their fabulous map.


Categories: Accretionary Wedge

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