Paleogeography
When geologists began to perceive the vast significance of Hutton’s doctrine that “the ruins of an earlier world lie beneath the secondary strata,” and that great masses of bedded rocks are separated from one another by periods of mountain making and by erosion intervals, it was natural for them to look for the lands that had furnished the debris of the accumulated sediments. In this way paleogeography had its origin, but it was at first of a descriptive and not of a cartographic nature.
The word paleogeography was proposed by T. Sterry Hunt in 1872 in a paper entitled “The Paleogeography of the North American Continent,” and published in the Journal of the American Geographical Society for that year. It has to do, he says, with the “geographical history of these ancient geological periods.” It was again prominently used by Robert Etheridge in his presidential address before the Geological Society of London in 1881. Since Canu’s use of the term in 1896, it has been frequently seen in print, and now is generally adopted to signify the geography of geologic time.
The French were the first to make paleogeographic maps, and Jules Marcou relates in 1866 that Elie de Beaumont, as early as March, 1831, in his course in the College of France and at the Paris School of Mines, used to outline the relation of the lands and the seas in the center of Europe at the different great geologic periods. His first printed paleogeographic map appeared in 1833, and was of early Tertiary time. Other maps by Beaumont were published by Beudant in 1841–1842. The Sicilian geologist Gemmellaro published six maps of his country in 1834, and the Englishman De La Beche had one in the same year. In America the first to show such maps was Arnold Guyot in his Lowell lectures of 1848. James D. Dana published three in the 1863 edition of his Manual of Geology. Of world paleogeographic maps, Jules Marcou produced the first of Jurassic time, publishing it in France in 1866, but the most celebrated of these early attempts was the one by Neumayr published in 1883 in connection with his Ueber klimatische Zonen während der Jura-und Kreidezeit.
The first geologist to produce a series of maps showing the progressive geologic geography of a given area was Jukes-Brown, who in the volume entitled “The Building of the British Isles,” 1888, included fifteen such maps. Karpinsky published fourteen maps of Russia, and in 1896 Canu in his Essai de paléogéographie has fifty-seven of France and Belgium. Lapparent’s Traité of 1906 is famous for paleogeographic maps, for he has twenty-three of the world, thirty-four of Europe, twenty-five of France, and ten taken from other authors. Schuchert in 1910 published fifty-two to illustrate the paleogeography of North America, and also gave an extended list of such published maps. Another article on the subject is by Th. Arldt, “Zur Geschichte der Paläogeographischen Rekonstructionen,” published in 1914. Edgar Dacqué in 1913 also produced a list in his Paläogeographischen Karten, and two years later appeared his book of 500 pages, Grundlagen und Methoden der Paläogeographie, where the entire subject is taken up in detail.
Conclusions.—Since 1833 there have been published not less than 500 different paleogeographic maps, and of this number about 210 relate to North America. Nevertheless paleogeography is still in its infancy, and most maps embrace too much geologic time, all of them tens of thousands, and some of them millions of years. The geographic maps of the present show the conditions of the strand-lines of to-day, and those made fifty years ago have to be revised again and again if they are to be of value to the mariner and merchant. Therefore in our future paleogeographic maps the tendency must ever be toward smaller amounts of geologic time, if we are to show the actual relation of water to land and the movements of the periodic floodings. Moreover, the ancient shore lines are all more or less hypothetic and are drawn in straight or sweeping curves, unlike modern strands with their bays, deltas, and headlands, and the ancient lands are featureless plains. We must also pay more attention to the distribution of brackish- and fresh-water deposits. The periodically rising mountains will be the first topographic features to be shown upon the ancient lands, and then more and more of the drainage and the general climatic conditions must be portrayed. In the seas, depth, temperature, and currents are yet to be deciphered. Finally, other base maps than those of the geography of to-day will have to be made, allowing for the compression of the mountainous areas, if we are to show the true geographic configurations of the lands and seas of any given geologic time.