Geology . hich have been most closely studied are those of someof the numerous lakes which existed at various points west of theRockies. Those of the Great Basin are best known (Fig. 536.) Lacustrine Deposits, Lake — The most considerableof the western Pleistocene lakes was Lake Bonneville, the body ofwater of which Great Salt Lake is the diminutive descendant. Itsbasin is believed to have been due to crustal deformation, and to haveantedated the lake itself by some considerable period. Previous tothe formation of the lake, the basin is thought to have been arid, aconclusion based
Geology . hich have been most closely studied are those of someof the numerous lakes which existed at various points west of theRockies. Those of the Great Basin are best known (Fig. 536.) Lacustrine Deposits, Lake — The most considerableof the western Pleistocene lakes was Lake Bonneville, the body ofwater of which Great Salt Lake is the diminutive descendant. Itsbasin is believed to have been due to crustal deformation, and to haveantedated the lake itself by some considerable period. Previous tothe formation of the lake, the basin is thought to have been arid, aconclusion based on the great alluvial cones and fans subsequentlycovered by the lake. During the pre-lacustrine period of aridity,such quantities of debris from the surrounding mountains were broughtinto the basin as to bury the bases of the mountains to depths of per-haps 2000 feet, at a maximum. 1 See the Pratt, Syracuse, Larned, and Kinsley sheets, U. S. Geol. Surv. 2 Gilbert, Mono. I, U. S. Geol. Surv. )() r j-u_ /~v. r ~ r~i_„«* THE PLEISTOCENE OR GLACIAL PERIOD. 457 Following this period of aridity, the climatic conditions were suchthat a large lake was brought into existence; but after enduring for a
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