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John

Good examples to visit in South Africa are the Rooi Rand dykes in northern KwaZulu-Natal province. Easily accessible along the Pongola River (I describe these in my 1994 MSc thesis from the University of Natal-Durban (now University of KwaZulu-Natal) and in a 1995 JSG paper. These are part of a failed Gondwana breakup dike swarm (Jurassic, intruded into Permo-Triassic Karoo sedimentary rocks). My former advisor and co-author on the JSG paper, Mike Watkeys (University of KwaZulu-Natal), is the best person to contact about dyke exposures in South Africa in general.

If you want something more recent (as in ~750 to 10,000s of years old), try the Reykjanes Peninsula in SW Iceland. Where the mid-Atlantic ridge comes onshore, there are exposed dikes along sea cliffs, including one that fed the Reykjanes Fires eruption ending in 1241. There are also dikes exposed intruding into late Pleistocene hyaloclastites.

Regards,
Simon Kattenhorn


On Sep 12, 2011, at 7:56 AM, John F. Dewey wrote:

Dear David,

Many thanks. Do you think that the RAF would fy me down there? I would go like a shot.

I will be in South Africa next year and will make preparatory enquiries.

Best wishes,
John

Dear John
Off the beaten track, but the Jurassic dykes are very well-exposed in the Falkland Islands, intruding Devonian quartzites and (to a lesser extent) Permian glacial and deltaic sediments.  Good rock-cut platforms around the coasts.  I do not know about South Africa, but it is possible that there are equally well-exposed examples in the Cape.

With best wishes
David

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David Macdonald
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-----Original Message-----
From: Tectonics & structural geology discussion list [mailto:[log in to unmask]] On Behalf Of John F. Dewey
Sent: 12 September 2011 15:33
To: [log in to unmask]
Subject: Re: Mafic dykes

_Dear Colleagues,

I am seeking out 100% exposed marine rock platforms where mafic dykes
and their wall structures, and, ideally, relay/transform offsets, and
terminations can be studied. I am seeking places where dykes were
injected laterally away from volcanic centres and places where dykes
were injected vertically beneath volcanic centres. I have visited a
few spots in Arran, Mull, and Skye but I am looking for a lot more.
Any help and suggestions will be greatly appreciated.

Best wishes,
John

_____________________________________________________

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Please note that my email address has changed to: [log in to unmask]

Prof. John F. Dewey FRS, M.R.I.A., FAA, Mem. Acad. Eur., Mem.
US Nat. Acad. Sci., Distinguished Emeritus Professor University of California, Emeritus Professor and Supernumerary Fellow, University College Oxford.

Sherwood Lodge,
93 Bagley Wood Road,
Kennington,
Oxford OX1 5NA,
England, UK

University College,
High Street,
Oxford OX1 4BH

Telephone Nos:
011 44 (0)1865 735525 (home Oxford)
011 44 (0)1865 276792 (University College Oxford)



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Simon Kattenhorn
Professor of Geology

Dept. of Geological Sciences
University of Idaho
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Moscow, ID 83844-3022

Office: McClure 303B
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