Page:The Journal of geology (IA journalofgeology11893univers).pdf/319

tainly they are not unaltered glacial deposits; and to assume that they are derived from such is to imply that no agency but glaciers is competent to move boulders of several feet in diameter. Russell refers to the occurrence of large angular rock masses on the alluvial fans of the arid regions at a distance of two or three miles from their source, to show that the movement of large boulders may take place under subaërial conditions; he cites the absence of ice-borne boulders among the finer strata of the Newark deposits; and he argues a relatively warm, not a cold climate, from the prevailingly red color of the formation and from the character of the fossils. Emerson has detected large boulders in certain basal beds of the sandstones in Northern Massachusetts, demonstrably close to their source, and not in the least indicative of glacial transportation. Indeed, to conclude that glacial action occurred at sea level during the period of Newark deposition simply from the coarse nature of certain marginal conglomerates, is to adopt an open alternative instead of a closed demonstration as a guide to belief.

Another line of evidence may be introduced against Fountaine's argument that the Newark conglomerates of Virginia were derived from glaciers which descended from the Appalachian mountains of that time. Local glaciers could originate in that latitude only on lofty mountains, from which they might descend to sea level, much as those of New Zealand now do. But the evidence gathered from the outline of the under border of the Newark areas does not at all favor the idea that they closely adjoined lofty mountains. If such had been the form of the surface whose submergence allowed the accumulation of the Newark sediments, their under border must have been extremely irregular; the Newark waters must have rounded many a bold promontory and penetrated many a deep bay. The basal sediments accumulated along so sinnous a water margin should now show some indication of these promontories and bays. They should be distributed much in the way that the Permian breccias of Wales lie around their once buried and now resurrected mountains, and thus show their origin on an extremely irregular coast. But as far as the basal beds of the Newark system have been studied out, they do not indicate that the surface on which they lie possessed any great relief at the time of their deposition. Whatever deformation it had previously suffered, whatever mountainous heights this deformation produced, the action of erosion had in pre-Newark time carried away enough material to some unknown goal