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The Geology
of Oman
5th World Petroleum Congress, May 30 - June 5, 1959 , New York,
USA
Mike Morton’s 1959 paper1 touched on one of the most intriguing aspects of
the geology of Oman: how oceanic crust, known as Semail ophiolite, came to occur all around the Hajar mountains. The theory
supported by Morton and others - Tschopp (1967)2 and Wilson (1969)3
- was that these igneous rocks had essentially flowed into position. G.M. Lees (1928)4 had
earlier proposed a huge thrust sheet, the Semail Nappe, based on his observations in the Oman Mountains, and on his knowledge
of the Alps and of the Zagros. As evidence of plate tectonics grew, a development of Lees' theory (Glennie (1974)5 emerged. This postulated that, as the continents moved together, a slab of ocean crust from the
ancient Tethys Ocean had been pushed over the continental margin for hundreds of kilometres about 87-76 million years ago.
However, a leading proponent of the ‘in-situ’ theory, Hugh Wilson, observed that the major displacement surfaces
were not prominent in the field and that he had seen more evidence of extension than compression in the Oman Mountains. Glennie
(2001)6 remains a spirited critique of most of Wilson’s arguments. Almost all later
authors interpret the Semail ophiolite as thrust, or obducted, probably due to a short period of subduction close to the margin
of the Arabian plate.7
References
1. Morton,
D.M."The Geology of Oman", Proceedings of the
5th World Petroleum Congress,
5th World Petroleum Congress, New York, Section I, Paper 14, p. 277-294.
2. Tschopp, R.H., 1967, “The General Geology of Oman”, Seventh
World Petroleum Congress Proceedings, Mexico, 2, 231-242.
3. Wilson, H., “Late Cretaceous Eugeosynclinal Sedimentation,
Gravity Tectonics and Ophiolite Emplacement in Oman Mountains, Southeast Arabia”, ''AAPG Bulletin'',
1969, 53, 626-671; “Late Cretaceous Nappes in the Oman Mountains and their Geologic Evolution: Discussion”. ''AAPG
Bulletin'', 1973, 57, 2282-2298; “The Age of the Hawasina and Other Problems of Oman Mountain Geology”,
''Journal of Petroleum Geology'', 2000, 23, 345-362.
4. Lees, G.M.,"The Geology and tectonics of
Oman and of parts of south-eastern Arabia", ''The Quarterly Journal of the Geographical Society'', 1928,
336, pp. 585-670.
5. Glennie, K.W., Boeuf, M.G.A., Hughes Clarke, M.W., Moody-Stuart, M., Pilaar, W.F.H. and Reinhardt,
B.M., ''Geology of the Oman Mountains'', Verhandelingen van het Koninklijk Nederlands Geologisch Minjbouwkundig
Genootschap (1974) ISBN 0 901360 35 X.
6. ”The Age of the Hawasina and Other Problems of Oman Mountain Geology,
''Journal of Petroleum Geology'', 2001, discussion by Glennie, 24, 477-484.
7. Searle, M. and Cox, J.,
"Tectonic Setting, Origin, and Obduction of the Oman Ophiolite", ''GSA Bulletin'', 1999, 111, 104-122.
Other Sources
Obituary: H. Hugh Wilson, “Still Challenging
Myths?”, Dr. A. Heward, Al Hajar (journal of the Geological Society of Oman), March 2009, pp. 4-7. <http://www.geologyoman.com/gso/Haj(Mar09).pdf>
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