Note on the interbasaltic horizon in Northern Ireland
V. Eyles
Feb 1, 1950
Citations
4
Citations
Journal
Quarterly Journal of the Geological Society of London
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Semantic Scholar
Key Takeaway Key Takeaway: In North Antrim, the interbasaltic horizons are separated by a Middle Lava Series consisting of tholeiitic basalts, and the presence of laterite indicates a major time-break in the volcanic sequence.
Abstract
In Mr. E. M. Patterson's “Preliminary Note on the Tertiary Lava Succession in North Antrim” (Abs. Proc. Geol. Soc. No. 1461, 28 March, 1950, p. 91) he claims that there are, in North Antrim, two interbasaltic horizons, characterized by the presence of laterite and separated by a Middle Lava Series consisting of tholeiitic basalts. The writer of the present note spent much time during the war in examining the Antrim laterites, and has prepared an account of them which is about to go to press. This new conception of Mr. Patterson's is therefore a matter of particular interest to him. The development of a laterite horizon, as distinct from the frequent but less-prolonged minor interbasaltic periods whose existence is well known, implies a major time-break in the volcanic sequence. For this and other reasons stated below the writer considered that Mr. Patterson's claim required careful examination. The Antrim lava plateau is built up of a succession of sub-aerial flows. Weathering of individual flows, marking, in most cases, minor interbasaltic periods, may be indicated by the presence of thin layers of red “bole”, by kaolinization of basalt, forming lithomarge, or by kaolinization followed by lateritization, i.e. by the formation of aluminous and ferruginous laterite (bauxite and iron ore). The existence of one major interbasaltic horizon, with deposits subsequently recognized to be lateritic in origin, has been known for at least 150 years. It was mapped during the primary geological survey of Ireland. The bauxite and iron ore were mined for many