560 



CENOZOIC TIME. 



3. RECENT PERIOD. 



The Recent Period is divided into (1) the Reindeer, or Second 

 Glacial era ; and (2) the Modern era. 



I. Rocks: kinds and distribution. 



The formations are such as are found now in progress, either over 

 the land, along sea-borders, or in seas : — 



Op Mechanical Origin. — 1. Continental — Alluvial beds along 

 rivers and about lakes ; drift sands or dunes ; glacial drift, but from 

 local glaciers. 2. Marine. — Estuary and delta formations ; sea-beach 

 accumulations ; off-shore deposits of detritus carried into the ocean by 

 rivers, or made from the battering of cliffs by the waves. 



Of Chemical Origin. — Stalactitic and stalagmitic accumulations 

 in caverns (p. 70), the latter often covering the floors of caverns to 

 a considerable depth, and enveloping relics of their former inhabit- 

 ants ; travertine deposits (p. 707) ; siliceous deposits of hot springs, as 

 those of Yellowstone Park, and, with these, silicified wood, leaves, 

 insects, etc. ; deposits of bog iron ores in marshes, with often iron-ore 

 fossils of fruits, stems, etc. 



Of Organic Origin. — Peat beds (p. 616); deposits of shells 

 and shell-limestone in lakes, or on seashores ; coral-reef formations 

 (p. 620) ; deposits of Rhizopod shells, over the ocean's bed (p. 611) ; 

 siliceous deposits, consisting of Diatoms, or of these and the spicules 

 of Sponges, either in fresh water, or in the ocean ; deposits of guano, 

 or bird excrements. 



Of Igneous Origin. — Lavas, and other rocks of igneous ejec- 

 tions, either from volcanoes or through fissures, comprising both dole- 

 rytic and trachytic kinds, but chiefly the former. 



The formations here enumerated are not always distinguishable 

 from those of the Champlain period. The shells and corals afford no 

 means of distinction, except on certain coasts, where there has been a 

 change of oceanic temperature ; but remains of Mammals, and espe- 

 cially relics of Man, when these are present, sometimes afford assist- 

 ance ; and so, also, the peculiar structure of the sand accumulations 

 and their geographical distribution. 



II. Reindeer and Modern eras in North America. 



The Recent period is separated from the Champlain, by an elevation 

 of the land over the higher latitudes, — that is, of nearly the same area 

 that was depressed in the Champlain period. As the Champlain de- 

 pression was greatest to the north, so it was with the elevation follow- 

 ing it ; for the height at which the Champlain deposits now stand over 

 the continent, from the southern Drift-limit to the Arctic, is a con- 



