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Annual Report of the Geological Commission
Annual Report of the Geological Commission Author:Geological Survey General Books publication date: 2009 Original publication date: 1897 Original Publisher: s.n. Subjects: Geology Science / Earth Sciences / General Science / Earth Sciences / Geology Notes: This is a black and white OCR reprint of the original. It has no illustrations and there may be typos or missing text. When you buy the General Boo... more »ks edition of this book you get free trial access to Million-Books.com where you can select from more than a million books for free. Excerpt: Beer Vlei Volcanic Series. Between Beer Vlei and Strydenburg there are three inliers of felsitic rocks rising from below the Glacial Conglomerate. They are of peculiar interest in that they show marked fluidal structure, which, together with the amygdaloidal characters of the rock and the presence of large masses of breccia composed of bits of the igneous rock, points to the volcanic origin cf the series. They are of great interest in another way; they have furnished many of the pebbles and boulders found in the Glacial Conglomerate of the immediate neighbourhood, and also in the Dwyka Conglomerate south of the Karroo. There is no evidence obtainable in this district as to the relations of the felsitic lavas and breccias to the ancient rocks of Prieska. All that can be said is that they are older than the Glacial Conglomerate, which contains such large quantities of boulders derived from them. These boulders were evidently broken from the parent rock after the steam-holes of the lavas were filled with chalcedony and other minerals. The lavas appear as a whole to be horizontally banded; at Bidouw's Kuil, however, at one spot the bands dip at an angle of 4O-so, but this deflection may be due to the original flow rather than to subsequent earth-movement. Owing to their massive character and their low rounded outcrops it is often impossible to ascertain whether the bands have any dip. At Vilet's Kuil both lavas and breccias are present, but at Brak Pan only breccias were seen. A very small...« less