Page:The Journal of geology (IA journalofgeology11893univers).pdf/233

This page has been proofread, but needs to be validated.
GEOLOGIC TIME.
659

Dr. Woodward says, on the opposite view, that in the earliest geological periods each bed of sand, clay, limestone, etc., had actually to be formed, and that later deposits had the older sedimentary ones to furnish material, and, therefore, the newer deposits were laid down more rapidly.[1] This does not impress me strongly; but from my experience among the Paleozoic rocks I agree with Sir A. Geikie, that "We can see no proof whatever, nor ever any evidence which suggests that on the whole the rate of waste and sedimentation was more rapid during Mesozoic and Paleozoic time than it is to-day.[2]

Professor Huxley, in his presidential address to the Geological Society of London in 1870, treats of the distribution of animals and says of his hypothesis that it "requires no supposition that the rate of change in organic life has been either greater or less in ancient times than it is now; nor any assumption, either physical or biological, which has not its justification in analogous phenomena of existing nature."[3]

In the Grand Cañon of the Colorado, Arizona, there are 11,950 feet of strata of Algonkian age extending unconformably beneath the Cambrian. There is nothing in this section to indicate that the conditions of deposition were unlike those of the strata of Paleozoic and Mesozoic time. The sandstones, shales, and limestones are identical in appearance and characteristics with those of the latter epoch. The deposition of sulphate of lime and gypsum occurred abundantly in the upper portions of the series, and salt is collected by the Indians from the deposits formed by the saline waters issuing from the sandstone 8,000 feet below the summit of the series. The sandstone and shales were deposited in thin, even laminæ and layers, and the sun cracks and ripple marks give evidence of slow, uniform deposition. In the upper part of Chuar terrane there are 235 feet of limestone. And in one of the layers of limestone, 2,700 feet below the summit of the Chuar terrane, I find abundant evidence of the pres-

  1. ↑ Geol. England and Wales, 2nd Ed., 1887, p. 23.
  2. ↑ Rept. Sixty-second Meeting Brit. Assoc. Adv. Sci., 1892, p. 19.
  3. ↑ Quart. Jour. Geol. Soc., Vol. 26, 1870, p. lxiii.
This article is issued from Wikisource. The text is available under Creative Commons Attribution-Share Alike 4.0 unless otherwise noted. Additional terms may apply for the media files.