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Contributions to the Petrology of British East Africa: Comparison of volcanic rocks from the Great Rift Valley with rocks from Pantelleris, the Canary Islands, Ascension, St. Helena, Aden, and Abyssinia. (With plate V)

  • G. T. Prior (a1)

Extract

The following notes on the petrology of British East Africa are the result of an examination of rock-specimens collected by Professor J. W. Gregory on his well-known expedition from Mombasa to Mt. Kenya and Lake Baringo in 1892-3, and of rock-collections from the Uganda Protectorate which have been recently presented to the British Museum by Sir Harry Johnston.

The collections include examples of the Archaean gneisses, schists, and granites which constitute the prevailing basement rocks of Central Africa; of ferruginotls schists, coarse sandstones, and quartzites belonging to the Palaeozoic Karagwe series ; and of an interesting series of Tertiary volcanic rocks comprising phonolites, phonolltic traehytes, riebeckite-rhyolites, kenytes, and basalts from the volcanoes of the Great Rift Valley, as well as of nephelinites and basaltic rocks containing melilite and perofskite from Mr. Elgon.

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Page 228 note 1 The Great Rift Valley. London, 1896, p. 227

Page 229 note 1 Beitr. z. geol. Kennt. d. östlichen Africa. Vienna, 1891

Page 229 note 2 Neues Jahrb. Min., 1886, Beil.-Bd. iv, p. 516.

Page 229 note 3 Baumann, Dutch Massailand zur Nilquelle. Berlin, 1894, p. 268.

Page 229 note 4 The specimen is from the Scott Elliot collection in the British Museum.

Page 230 note 1 Mem. Geol. Survey lndia, 1900, vol. xxviil, part 2, pp. 119-249.

Page 230 note 2 Quart. Journ. Geol. Soc., 1900, vol. lvi, p. 601

Page 230 note 3 Records Geol. Surv. India, 1896, vol. xxix, p. 20.

Page 231 note 1 Quart. Journ. Geol. Soc., 1895, vol. li, pp. 677-9.

Page 232 note 1 Quart. Journ. Geol. Soc., 1898, vol. liv, pp. 73-99.

Page 232 note 2 Geol. Mag., 1899, vol. vi, p. 105 ; the particular rocks arc marked T. B. in the sections.

Page 232 note 3 This Magazine, 1900, vol. xii, p. 255.

Page 232 note 4 Deugsch-Ost-Afrika. Band vii, Geologie, Berlin, 1900.

Page 233 note 1 Loc. cit., p. 461.

Page 233 note 2 Geogr. Journ., 1902, vol. xix, p. 14.

Page 234 note 1 Neues Jahrb. Min., 1886, Beil.-Band iv, p. 595.

Page 234 note 2 Lenk, Ueber Gesteine aus Deutsch-Cstafrika; in Baumann, Durch Massailand zur Nilquelle, Berliu, 1894, p. 289.

Page 235 note 1 Tschermak's Min. Mitth., 1896, vol. xv, p. 394.

Page 235 note 2 Loc. cit., p. 229.

Page 235 note 3 This Magazine, 1900, vol. xii, p. 255.

Page 238 note 1 The numbers in parentheses refer to the specimens in Professor Gregory's collection. Most of the localities of these specimens are given in the maps, illustrating Professor Gregory's journey, in ‘The Great Rift Valley.‘ London, 1896.

Page 239 note 1 Quart. Journ. Geol. Soc., 1900, vol. lvi, p. 210, pl. XI, fig. 5, and pl. XII, fig. 1.

Page 240 note 1 Neues Jahrb. Min., 1886, Beil.-Band iv, p. 590.

Page 240 note 2 This Magazine, 1900, vol. xii, p. 269.

Page 242 note 1 Neues Jahrb. Min., 1886, Beil.-Band iv, p. 596.

Page 244 note 1 This Magazine, 1900, vol. xii, p. 263, fig. 3, pl. 3.

Page 244 note 2 Quart. Journ. Geol. Soc., 1900, vol. lvi, p. 212.

Page 245 note 1 Rosenbusch, Elemente d. Gesteinslehre, 1898, p. 257.

Page 246 note 1 Quart. Journ. Geol. Soc., 1900, vol. lvi, p. 221.

Page 246 note 2 Ueber die Gesteine des Kenya und des Kilimandjaro. Centralblatt Min., 1902, pp. 204-5.

Page 253 note 1 Geol. Mag., 1901, vol. viii, p. 368.

Page 254 note 1 Many of the needles consist of calcite, and possibly represent altered melilite.

Page 254 note 2 Mikr. Phys. Ges., 3rd ed., 1896, vol. ii, p. 812.

Page 255 note 1 Förstner, Nota preliminare sulla geologia dell' Isola Pantelleria. Boll. Com. Geol. d'Italia, 1881, vol. xii, pp. 523-56.

Page 255 note 2 This Magazine, 1901, vol. xiii, p. 89.

Page 256 note 1 Quart. Journ. Geol. Soc., 1900, vol. lvi, p. 208.

Page 256 note 2 The specimens here described belong to a collection presented by Mr. R. L. Antrobus in 1891.

Page 257 note 1 This Magazine, 1900, vol. xii, p. 265, and fig. 4, pl. 3.

Page 257 note 2 This Magazine, 1900, vol. xii, pp. 317-23.

Page 257 note 3 Challenger Reports, Physics and Chemistry, vol. ii, pt. 4, pp. 39-74.

Page 258 note 1 Loc. cit., p. 53.

Page 258 note 2 This Magazine, 1900, vol. xii, p. 94.

Page 258 note 3 Loc. cit., p. 47.

Page 259 note 1 The collection was made by Dr. W. T. Blanford when acting as geologist to the Abyssinian Expedition of 1868 under Sir Robert Napier.

Page 260 note 1 See Lacroix, Les roches alcalines caractérisant la province pétrographique d'Ampasindava. Nouv. Archives du Muséum d'Histoire Naturelle. Paris, 1902, sér. 4, tom. iv, fasc. 1, 152 pp., 10 pls. ; and this Magazine, 1900, vol. xii, p. 272.

Page 260 note 2 Esch, E., Sitz.-Ber. Akad. Wiss. Berlin, 1901, pp. 277, 400.

Page 261 note 1 With the exception of the Hungarian andesites.

Page 261 note 2 The ‘bread-crust’ bombs of Lipari (the ‘volcanite’ of Hobbs, Zeits. Deutsch. geol. Gesellschaft, 1893, vol. xlv, p. 578) are, by their mineral contents at least, more closely connected with the kenyte-series (pantellerites) than with the dacites.

Page 261 note 3 The lavas of the West Indies, however, as we have recently seen, still rather conform to the Pacific than to the Atlantic type.

Page 262 note 1 See Prior, Report on the Rock-specimens, p. 328, in Report on the Collections of Natural History made in the Antarctic Regions during the voyage of the ‘Southern Cross.’ London, 1902

Page 262 note 2 A list, with localities, of the specimens in Sir Harry Johnston's collections from Uganda, is given in his book ‘The Uganda Protectorate.’ London, 1902.

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