Climate and Time in Their Geological Relations / A Theory of Secular Changes of the Earth's Climate

by James Croll

OOLITIC PERIOD.

North of Scotland.—There is not wanting evidence of something like the action of ice during the Oolitic period.[179]

In the North of Scotland Mr. James Geikie says there is a coarse boulder conglomerate associated with the Jurassic strata in the east of Sutherland, the possibly glacial origin of which long ago suggested itself to Professor Ramsay and other observers. Mr. Judd believes the boulders to have been floated down by ice from the Highland mountains at the time the Jurassic strata were being accumulated.

North Greenland.—During the Oolitic period a warm condition of climate extended to North Greenland. For example, in Prince Patrick’s Island, at Wilkie Point, in lat. 76° 20′ N., and long. 117° 20′ W., Oolitic rocks containing an ammonite (Ammonites McClintocki, Haughton), like A. concavus and other shells of Oolitic species, were found by Captain McClintock.[180] In Katmai Bay, near Behring’s Straits, the following Oolitic fossils were discovered—Ammonites Wasnessenskii, A. biplex, Belemnites paxillosus, and Unio liassinus.[181] Captain McClintock found at Point Wilkie, in Prince Patrick’s Island, lat. 76° 20′, a bone of Ichthyosaurus, and Sir E. Belcher found in Exmouth Island, lat. 76° 16′ N., and long. 96° W., at an elevation of 570 feet above the level of the sea, bones which were examined by Professor Owen, and pronounced to be those of the same animal.[182] Mr. Salter remarks that at the time that these fossils were deposited, “a condition of climate something like that of our own shores was prevailing in latitudes not far short of 80° N.”[183] And Mr. Jukes says that during the Oolitic period, “in latitudes where now sea and land are bound in ice and snow throughout the year, there formerly flourished animals and plants similar to those living in our own province at that time. The questions thus raised,” continues Mr. Jukes, “as to the climate of the globe when cephalopods and reptiles such as we should expect to find only in warm or temperate seas, could live in such high latitudes, are not easy to answer.”[184] And Professor Haughton remarks, that he thinks it highly improbable that any change in the position of land and water could ever have produced a temperature in the sea at 76° north latitude which would allow of the existence of ammonites, especially species so like those that lived at the same time in the tropical warm seas of the South of England and France at the close of the Liassic, and commencement of the Lower Oolitic period.[185]

The great abundance of the limestone and coal of the Oolitic system shows also the warm and equable condition of the climate which must have then prevailed.