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V.—On Concretionary Nodules with Plant-Remains found in the Old Bed of the Yarra at S. Melbourne; and their Resemblance to the Calcareous Nodules known as ‘Coal-Balls.’
Published online by Cambridge University Press: 01 May 2009
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Although many of the nodular bodies met with in sedimentary rocks which were formerly held to be concretions or simple aggregations of mineral matter have since been found to be due to the work of minute animals or plants, there is yet a more numerous class of true concretions which were undoubtedly formed by chemical reaction in the surrounding water and sediments; the resulting precipitation being often deposited upon nuclei of organic origin, as fish, woody fragments, or shells. Occasionally these nodules were of subsequent formation to the deposit in which they occur. In nodules which include organic remains, the segregation was accelerated by the partial decay of the included organic fragments.
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page 554 note 1 1 Mr. Spry has also shown me portions of branches of gum-trees, one of which has been charred by fire. These he found at the bottom of a sewer manhole at the corner of McGowan and Power Streets, at 14 feet from the surface and about 4 to 6 feet below the present low-water mark. Prehistoric bush-fires must have been of frequent occurrence, and may be ascribed to the action of lightning. At the time of writing this note there is a paragraph in the Argus, February 14th, 1906, reporting several bush-fires having been started by lightning at Chetwynd and Kadnook in Western Victoria. An interesting feature connected with the above occurrence of drifted wood was a bank of marine shells 7 inches thick, left behind the logs by the retreating tide. See also the reference to charred wood in coal-seam nodules by A. C. Seward (“Fossil Plants,” vol. i, p. 88).
page 555 note 1 See Cash, & Hick, : Proc. Yorkshire Geol. and Polytech. Soc., vol. vii (1878-1881), p. 73.CrossRefGoogle Scholar Also Seward, : “Fossil Plants,” vol. i (1898), p. 85.Google Scholar
page 555 note 2 Report, 1892, p. 13. See also Scott, D. H.: “Studies in Fossil Botany,” 1900, p. 11.Google Scholar
1 Whilst writing these notes I have received a valuable and suggestive paper by Douvillé, M. H., “Les ‘Coal-balls’ du Yorkshire,” from the Bull. Soc. Géol. France, sér. iv, vol. v, pp. 154–156Google Scholar, pl. vi, in which that author records the association of large numbers of Goniatites (Gastrioceras), Nautilus, Orthoceras, Aviculopecten, and other marine shells, with the coal-balls and their vegetable contents.
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