Geology . The prevalence of this rock origi-nally gave origin to the name Oolitic for all that part of the systemabove the Lias. The oolitic structure affects not only much of thelimestone, but also lenses and beds of iron ore, in various parts of thecentral province. In England, parts of the Middle Jurassic containestuarine and fresh-water beds, and sometimes (as in Yorkshire) coalseams and beds of iron ore. Marine LTpper Jurassic beds overlie thenon-marine parts of the Middle Jurassic. In southern Europe, the Middle Jura has but little representation,or has not been thoroughly differentiated
Geology . The prevalence of this rock origi-nally gave origin to the name Oolitic for all that part of the systemabove the Lias. The oolitic structure affects not only much of thelimestone, but also lenses and beds of iron ore, in various parts of thecentral province. In England, parts of the Middle Jurassic containestuarine and fresh-water beds, and sometimes (as in Yorkshire) coalseams and beds of iron ore. Marine LTpper Jurassic beds overlie thenon-marine parts of the Middle Jurassic. In southern Europe, the Middle Jura has but little representation,or has not been thoroughly differentiated. In the eastern province, 1 Geikie, op. cit., p. 1132. 2 Idem., p. 1154. 71 GEOLOGY. the larger pari of the Middle Jura is wanting, though the upper horizonsmay be present. Middle Jurassic beds in Lat. 71° have yielded speciesof sub-tropical ferns, cycads, and The Upper Jura.—The encroachment of the sea which was in progressduring the Middle Jurassic time reached its maximum a little later. Fig. 355.—Sketch-map of Europe in the Middle Jurassic period. The shaded areas:are areas of deposition, chiefly marine. (After De Lapparent.) as shown by the wide distribution of the Upper Jurassic formations;but before the end of the epoch the sea began to withdraw, for someparts of the area which had been submerged became land, while otherparts were occupied by lakes and bodies of brackish water. The formations of the Upper Jurassic in central Europe containmuch more limestone than those of the lower divisions of the systemin the same province. Corals and sponges were especially abundantin central Europe, and contributed much to the making of the light-colored limestone which, on the continent, has given this member 1 De Lapparent, Trait e de Geologie, p. 1142. THE JURASSIC PERIOD. 75 of the system the name of the White Jura. Some of the sandstonesalso are white. One of the notable phases of the Upper Jurassic in central Europeis the Solenhofen limestone of southern German
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