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XVI.—Note on an Algal Limestone from Angola

Published online by Cambridge University Press:  06 July 2012

M. F. Romanes
Affiliation:
Harkness Scholar, Newnham College, Cambridge.

Extract

The specimens here described were collected by Professor J. W. Gregory in Angola, and belong to the series described in the paper by him on the geology of that country.

The horizon of the beds from which the limestone was obtained is Albian.

The specimens are of a yellowish pisolitic limestone. In hand specimens the weathered surface has a warty appearance—the diameter of each knob being about 1 cm. A fractured surface shows circular forms varying in size and having decided concentric markings. These concentric markings are, however, less evident in microscopic sections, and this is probably due to the effects of preservation. A similar case has been described by Mr H. Yabe, where the genus Metasolenopora is affected in this way. These circular forms make up the greater part of the rock, and are cemented together by a fine calcareous paste in which are fragments of shell and quartz grains, with occasional grains of other minerals, such as felspar and muscovite. The specimens of limestone examined varied to some extent in texture, some being more compact, and even slightly siliceous, but the contained organisms are present in similar amounts regardless of the texture of the rock.

Type
Research Article
Copyright
Copyright © Royal Society of Edinburgh 1917

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References

page 581 note * Yabe, H., Sci. Rep. Imp. Toholm Univ. Sendai. Japan, vol. i, No. 1, 1912, p. 2Google Scholar.

page 581 note † Wethered, E., Geol. Mag., dec. 3, vol. vi, 1889, pp. 196200CrossRefGoogle Scholar.

page 581 note ‡ Garwood, E. J., Q.J.G.S., vol. lxviii, 1912, p. 580Google Scholar, pl. xlvii, “Carboniferous Succession in N.W. England.”

page 581 note § M'Lean, R. C., Proc. Camb. Phil. Soc., vol. xvi, pl. vi, 1912, p. 512Google Scholar, “Group of Rhizopods from Carboniferous Period.”

page 581 note ∥ Nicholson, A. and Etheridge, R., A Monograph of the Silurian Fossils of the Girvan District, Edin., 1878, p. 23, pl. ix, fig. 24Google Scholar.

page 582 note * Wethered, E., Q.J.G.S., vol. xlvi, 1890, p. 270CrossRefGoogle Scholar, On the Occurrence of Genus Girvanella in Oolitic Rocks”; also Geol. Mag., dec. 3, vol. vi, 1889, p. 196Google Scholar, “On the Microscopic Structure of Jurassic Pisolite.”

page 582 note † H. Yabe, op. cit.

page 582 note ‡ Chapman, F., Rep. Aust. Ass. Adv. Sci., vol. xi, 1907, p. 377Google Scholar.

page 582 note § Rothpletz, A., Zeit. deutsch. Geol. Ges., vol. xliii, 1891, p. 302Google Scholar, “Calcareous Algæ.”

page 583 note * A. Rothpletz, op. cit.

page 583 note † H. Foslie, Kongl. Norske Vidensk. Selsk. Skr., 1900, No. 5, p. 12.