292 ECONOMIC GEOLOGY 
Oligocene, 5000 feet; and Zorritos, Miocene, 5000 feet). 
These beds have been disturbed by a great fault parallel to the 
coast, and from it branches run inland and break the country 
into large fault blocks. The oil is found in evenly dipping 
beds, and not in anticlines, and the beds are mostly waterless. 
The oil seems to have been distilled from organic matter by 
the heat due to the earth movements; but the connection 
is not obvious.as the oil is not found in direct relation to 
the faults. 
In the Argentine some promising anticlinal lines proved 
disappointing ; but bores for water in the basin of the Lower 
Chuput River near Comodoro Rivadavia reached heavy fuel 
oil in Cretaceous shales. This field as a whole is a great 
syncline, with oil pools in secondary anticlines on its floor. 
Eurore—In Europe and Asia the chief oilfields occur 
along the Alpine-Himalayan mountain system. Most of 
the oil comes from Kainozoic marine shales containing 
abundant foraminifera or marine diatoms or alge, or from 
bituminous limestones. The oil has been derived by the 
distillation of the organic matter by the heat and pressure 
of earth movements. The geological structure of some fields 
is very complex. 
The westernmost field is in the rift-valley of the Upper 
Rhine, where Oligocene sands have been dropped between 
the faults and crumpled (Fig. 63, d). The oil from Pechel- 
bronn was known in the fifteenth century, and has been 
obtained since 1735 by dug wells; deeper beds with lighter 
oils were found by boring, and are now being mined, as 
70 per cent. of the oil can be recovered fron the sands by 
drainage into galleries, whereas only 16 per cent. was obtained 
by wells (de Chambrier, 1921). 
In Poland the oil industry dates fron 1853; drilling 
began in 1870, and the field reached its maximum yield of 
15 million barrels in 1899. The productive rocks range from 
the Cretaceous to Miocene, the Eocene being the richest; 
the beds have been elaborately overthrusted and over- 
folded (cf. Fig. 63, f), leading to local accumulations of oil. 
In Roumania the rocks are also intensely folded and faulted 
by the Alpine movements; the oil beds range from the Cre- 
taceous to the Pliocene and they contain much gypsum and 
salt ; the oil has collected into some rich pools: thus 130