The Elements of economic geology

Bibliographic data

Monograph

Identifikator:: 1773832379

URN:: urn:nbn:de:zbw-retromon-172798

Document type:: Monograph

Author:: Gregory, John W. http://d-nb.info/gnd/11683014X

Title:: The Elements of economic geology

Place of publication:: London

Publisher:: Methuen

Year of publication:: 1928

Scope:: XIV, 312 S.; graph. Darst.

Digitisation:: 2021

Collection:: Economics Books

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Chapter

Document type:: Monograph

Structure type:: Chapter

Title:: Part V. Mineral fuels

Collection:: Economics Books

270 ECONOMIC GEOLOGY are of poor quality, such as the Virtuewell Seam in Lanark- shire; while the adjacent high quality coals show no evi- dence of growth in place. Coal seams moreover may pass laterally into shale or sandstone, or may subdivide above and below a layer of sand or clay-like beds deposited by water. The thickness of many coal seams is inconceivable for forest growths. On the estimate that 20 feet of vege- table residue are required to form 1 foot of coal, the 30-foot seam at Dudley would have required 600 feet of forest debris ; some seams in India are 100 feet in thickness, and would have required a thickness of 2000 feet. The Fushun seam in Manchuria is more than 200 feet thick. Such thick de- posits present no difficulty as accumulations of vegetation carried by streams from forest-clad hills into a deep lake. The theories of the formation of coal in situ and by drift both appear true for different fields. In Yorkshire, and in Silesia, where twenty-seven seams are superimposed and each has its underclay, and in the South Joggins section in Nova Scotia, where repeated seams with vertical tree-trunks occur over clay with roots, the coal has been clearly formed as a forest growth ; but in some fields, as in Scotland, India, and France, some seams were formed by accumulations of drifted vegetation. CarBon EnricuMeENT IN CoaL Seams—That the main chemical change in coal formation is carbon enrichment by gradual elimination of hydrogen and oxygen is shown by the proportions of these constituents in the sequence from wood to anthracite. This process is at first bio-chemical, being controlled by living ferments in the wood and bacteria. Bertrand and Renault considered that the bio-chemical influence lasts much longer than the first stage. Coal for- mation has been regarded as mainly dependent on bacteria ; but the particles so identified appear to be specks of inor- ganic matter. The biochemical processes stop at an early ! The view that all coal is deposited under water has been recently readvanced by Dr. Murray Stewart. He regards coal as due to bacterial action in swamps and lagoons which converts vegetable matter into particles of coal; they are washed into lakes or the sea and there deposited as a coal mud, mixed with tree-stems which he regards as also floated to their present positions, their erect position being due to the roots being weighted and therefore sinking first (Geology of Oil Shale and Coal, 1926, pp. 19-21).

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