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II.—Volcanic Neck Emplacement and Subsidence Structures at Dunbar, South-East Scotland

Published online by Cambridge University Press:  06 July 2012

E. Howel Francis
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Synopsis

Structures in and around volcanic necks at Dunbar are interpreted as belonging to two different stages in volcanism. Some, which are related to an early neck emplacement stage, include small ring structures—probably incipient (crypto-volcanic) necks—filled with marginally flow-banded breccias, dykes of similarly margined unbedded tuff, and tuff-penetrated wall rocks. Among the last are sandstones veined along planes of minor fracture by very fine sand.

Other structures belong to a later stage during which bedded tuffs, that had originally accumulated sub-ærially, subsided into the necks in a process here likened to caldera formation. In one large neck the bedding is relatively undisturbed, but in smaller necks there are high inward dips from the margins and collapse structures, sometimes accompanied by reconstitution of the clastics, at the centres. Diagnostic features of subsidence margins are anastomozing veins of carbonate, locally accompanied by hæmatite, and these appear to be related to dykes of flow-banded sandstone and sandy tuff intruded along fractures initiated inside the necks during subsidence. Other structures described are ring-fracture, with or without gouge, and down-drag of wall-rocks: these suggest a solution to the space problem posed by caldera mechanism.

Type
Research Article
Information
Earth and Environmental Science Transactions of The Royal Society of Edinburgh , Volume 65 , Issue 2 , 1962 , pp. 41 - 58
Copyright
Copyright © Royal Society of Edinburgh 1962

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References

References to Literature

Anderson, E. M., 1936. “The Dynamics of the Formation of Cone-sheets, Ring-dykes and Cauldron Subsidences”, Proc. Roy. Soc. Edin., 56, 128–157.CrossRefGoogle Scholar
Bailey, E. B., 1960. “Dunbar” in Edinburgh Geology: an Excursion Guide, Edinburgh.Google Scholar
Cloos, H., 1941. “Bau und Tätigkeit von Tuffschloten. Untersuchungen an dem Schwäbischen Vulkan”, Geol. Rdsch., 32, 705–800.Google Scholar
Clough, C. T. et al. , 1910. “The Geology of East Lothian (2nd Ed.)”, Mem. Geol. Surv. U.K.Google Scholar
Cumming, G. A., 1936. “The Structural and Volcanic Geology of the Elie-St. Monance District, Fife”, Trans. Edin. Geol. Soc., 13, 340–365.CrossRefGoogle Scholar
Fisher, R. V., 1960. “Classification of Volcanic Breccias”, Bull. Geol. Soc. Amer., 71, 973–981.CrossRefGoogle Scholar
Foshag, W. F., and Gonzáles, R. J., 1956. “Birth and Development of Parícutin Volcano, Mexico”, Bull. U.S. Geol. Sun., 965–D, 355–489.Google Scholar
Francis, E. H., 1957. “New Evidence of Volcanicity in West Fife”, Trans. Edin. Geol. Soc., 17, 71–80.CrossRefGoogle Scholar
Francis, E. H., 1959. “A Volcanic Vent in the Bogside Mines, Fife”, Geol. Mag., 96, 457–469.CrossRefGoogle Scholar
Francis, E. H., 1960. “Intrusive Tuffs Related to Firth of Forth Volcanoes”, Trans. Edin. Geol. Soc., 18, 32–50.CrossRefGoogle Scholar
Francis, E. H., 1961. “Sedimentation in Relation to Volcanism in the Limestone Coal Group of the Saline District, Fife”, Bull. Geol. Surv. U.K., 17, 116–144.Google Scholar
Geikie, A., 1902. “The Geology of East Fife”, Mem. Geol. Surv. U.K.Google Scholar
Howell, H. H. et al. , 1866. “The Geology of East Lothian”, Mem. Geol. Surv. U.K.Google Scholar
Reynolds, Doris L., 1956. “Calderas and Ring-complexes”, Verh. Geol.-Mijnb. Genoot. Ned. Kolon., 16, 355–379.Google Scholar
Wentworth, C. K., and Williams, H., 1932. “The Classification and Terminology of the Pyroclastic Rocks”, Bull. Nat. Res. Coun. Wash., 89, 19–53.Google Scholar
Williams, H., 1941. “Calderas and their Origin”, Bull. Deft. Geol. Univ. Calif., 25, 239–346.Google Scholar
Wilshire, H. G., 1961. “Layered Diatremes near Sydney, New South Wales”, J. Geol., 69, 473–484.CrossRefGoogle Scholar