Geology . filling of shallow basins with sediment, is unknown. At the beginning of the Oligocene period, the sea transgressed con-siderable areas of Germany which had been land in the Eocene period. 1 Dall, op. cat., and Diller, 17th Ann. Rept. U. S. Geol. Surv. 2 Dawson, Science, March 15, 1901. 3 Schrader, Bull. G. S. A., Vol. 13, p. 248, and Brooks, p. 261. 4 Dall, Trans. Wagner Free Inst., Vol. VI, 1903, p. 1548. See also Dall, 18thAnn. Rept. U. S. Geol. Surv., Pt. II, and Spurr, Pt. III. The Kenai formation wasformerly classed as Eocene. 5 See references to the writings of Hill under Eoce
Geology . filling of shallow basins with sediment, is unknown. At the beginning of the Oligocene period, the sea transgressed con-siderable areas of Germany which had been land in the Eocene period. 1 Dall, op. cat., and Diller, 17th Ann. Rept. U. S. Geol. Surv. 2 Dawson, Science, March 15, 1901. 3 Schrader, Bull. G. S. A., Vol. 13, p. 248, and Brooks, p. 261. 4 Dall, Trans. Wagner Free Inst., Vol. VI, 1903, p. 1548. See also Dall, 18thAnn. Rept. U. S. Geol. Surv., Pt. II, and Spurr, Pt. III. The Kenai formation wasformerly classed as Eocene. 5 See references to the writings of Hill under Eocene. THE EOCENE PERIOD. 249 At the time of its maximum extension (Middle Oligocene, Fig. 438), theepicontinental sea of the period covered much of north Germany, andthe North Sea was connected with the Mediterranean, and extended tosoutheastern Russia, and even to the Aral The oldest Oligocene deposits of central and western Europe arelargely of terrestrial, fresh- and brackish-water origin. Local de-. Fig. 438.—Sketch-map of Europe in the Middle Oligocene. The shaded part showsarea of deposition. (After De Lapparent.) posits of salt and gypsum show that there were local bodies of water ofexcessive salinity. In Britain, the Oligocene has but slight representation, being foundin one small area (Hampshire basin and Isle of Wight) only. As inmost other parts of Europe, the beds are partly marine and partly non-marine. Some of the igneous rocks of the islands about north Scotlandmay have dated from this period. The Oligocene is represented in theParis basin, partly by marine beds, partly by beds deposited in brack- 1 Kayser, Geologische Formationskunde, p. 479. 250 QEOLOQY iafa water, and partly by beds of fresh-water origin. They lie uncon-formably on older formations. They include4 sands, marls, arkoses, andlimestones, some of which are of fresh-water origin (snail-shells, caddisworms, chara, etc.). Coal is also present, and the conifers and cypresseswhich entered largely
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