THE JURASSIC PERIOD. 73 



the early part of the Jurassic, and the Lias frequently overlies the 

 Trias conformably, and with no very definite plane of demarkation. 

 The early Jurassic beds are mostly marine, and were deposited in waters 

 which were shallow, and the sediments were mostly clastic and fine. 

 Near its eastern border in central Europe, the Lias contains coal in 

 quantity, as many as 25 workable coal beds occurring at one point 

 in Hungary. In other places, too, as in England, there are indications 

 of non-marine conditions of sedimentation, both in the fossils and 

 in the thick beds of earthy iron carbonate of commercial value. 1 Some 

 of the Liassic shales of Germany afford oil. 2 



The Lias of southern Europe is more largely calcareous than that 

 of central Europe. Red marble, carrying abundant ammonites, is a 

 characteristic formation of the eastern Alps, the Carpathians, the 

 Apennines, and in Spain. 



In the eastern province of Europe, the Lower Jura is unknown. 

 It occurs in the southern part of Russia (the Caucasus Mountain 

 vicinity), but this is classed with the southern rather than with the 

 eastern province. 



Middle Jura. — The Middle Jura, and especially its upper part, 

 is somewhat more widespread than the Lower, in central Europe, indi- 

 cating progressive sea-encroachment. During the early part of the 

 epoch, the deposits, like those of the Lias, were imiform over consider- 

 able areas, but during the later part, they became more diverse so 

 far as their fossils were concerned, showing that conditions sufficiently 

 different to influence life, affected various parts of the province. 



Oolite is one of the characteristic formations of the Middle Jura 

 of central Europe as of England. The prevalence of this rock origi- 

 nally gave origin to the name Oolitic for all that part of the system 

 above the Lias. The oolitic structure affects not only much of the 

 limestone, but also lenses and beds of iron ore, in various parts of the 

 central province. In England, parts of the Middle Jurassic contain 

 estuarine and fresh-water beds, and sometimes (as in Yorkshire) coal 

 seams and beds of iron ore. Marine tapper Jurassic beds overlie the 

 non-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, 



a Geikie, op. cit., p. 1132. 

 2 Idem., p. 1154. 



