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VI.—The Use of a Geological Datum

Published online by Cambridge University Press:  01 May 2009

Beeby Thompson
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Extract

A proper interpretation of some geological phenomena requires that allowance shall be made for differential earth-movements that have taken place since the period of occurrence of the events or conditions under consideration.

Present differences of level in rocks of the same age may be partly due to actual differences in depth of the sea-floor on which they were deposited, but they may also be the results of subsequent differential earth-movements either of a regional or of a local character, the latter including ‘fauhs.’

In order to estimate the amount of displacement or differential movement, it is necessary to select a particular rock as a datum. The rock selected should combine, as far as possible, the following characteristics:—

1. It should be comparatively thin.

2. It should have a considerable horizontal extension.

3. It should combine similarity in physical characters and palæontological contents over a large area, so that uniformity of depth of deposit may be postulated.

Type
Original Articles
Information
Geological Magazine , Volume 10 , Issue 5 , May 1903 , pp. 216 - 225
Copyright
Copyright © Cambridge University Press 1903

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References

page 217 note 1 For convenience we will speak of all as borings.

page 217 note 2 Henry John Eunson F.G.S., “The Range of the Palæozoic Rocks beneath Northampton”: Quart. Journ. Geol. Soc., vol. xl, pt. 3, No. 159, pp. 482–496.

page 219 note 1 Rev. C. II. Hartshorne: “A Report on the Drainage of the Nene Valley”; Northampton, 1848.

page 220 note 1 Henry John Eunson F.G.S., “The Range of the Palæozoic Rocks beneath Northampton”: Quart. Journ. Geol. Soc., vol. xl, pt. 3, Xo. 159, p. 486.

page 221 note 1 See also “The Victoria History of the Counties of England: Northampton-shire,” Geology, vol. i, p. 8.

page 221 note 2 “Note on a futile search for Coal near Northampton”: GEOL. MAG., Vol. VIII, p. 505.

page 222 note 1 “The Oolites of Northamptonshire,” part i: Quart. Journ. Geol. Soc., March, 1870.

page 222 note 2 “Note on a futile search for Coal near Northampton”: GEOL. MAG., Vol. VIII (1871), p. 605.