THE CLASSIFICATION OF THE TERTIARY DEPOSITS* 131 
described by Dr. Yon Hantken. A deep well-boring near tbe 
city has fully confirmed the conclusions which had been arrived 
at as to the great thickness (more than 2000 feet) of the marine 
Oligocene strata in this area. Underlying the great masses of 
Miocene lava that cover so large a portion of Hungary there 
are found at many points marine strata, which by their fossils 
must be referred to the Oligocene. These beds, as developed 
near Yissegrad, have been well described by Dr. Koch. 
When we proceed westward, into the Yienna Basin, we find 
that the Middle and Lower Oligocene strata are altogether 
wanting in that area, and only the Upper Oligocene is 
represented by the ‘ Aquitanische Stufe/ In passing south- 
wards, into Styria, Croatia, and Sclavonia, these Upper Oligo- 
cene strata are found to consist of brackish- water and terrestrial 
deposits, just as is the case farther west in Transylvania. 
In Northern Germany, throughout the whole of the drift- 
covered districts, stretching from Warsaw to Hamburg, patches 
of Oligocene strata are here and there found rising above the 
superficial covering of the country, and the same deposits are 
constantly met with in wells and borings. These strata contain 
marine fossils, sometimes of littoral, at others of a deeper- water 
character. It is in these beds that the German geologists have 
discovered such a rich molluscan and coral fauna. The most 
abundant stores of fossils have been obtained during the sink- 
ing of pits to the brown-coal beds (which are of the age of 
the Barton Clay), the shafts often passing through richly fos- 
siliferous clays and sands before reaching the lignite beds. 
As is the case in Hungary with the Oligocene strata, so we 
find with the marine beds of that age in Northern Germany 
that when traced southwards they graduate into estuarine, fresh- 
water, and terrestrial formations. Opening into the great North 
' German Oligocene sea we find clear evidences of the existence 
of four or five great deltas at this period. The most easterly of 
these now forms the country of Lower Silesia ; next we have 
tbe delta of the Saxon district ; thirdly, we find the delta of the 
Lower Rhine, of which the Mayence Basin may be regarded as 
a part ; and fourthly, the estuarine deposits of Oligocene age in 
the Netherlands, and in the Paris, and the Hampshire Basins, 
which are all very closely connected with one another, and may 
have formed parts of several more or less united deltas. In the 
North German deltas we find beds of brown coal (distinct from 
and of younger date than the great Upper Eocene brown-coal 
; formation), which alternate with sands and clays containing 
fresh- water or brackish -water fossils. Farther westward, we 
have only thin lignite deposits, the strata consisting of fresh- 
water limestone, clays and sands, with occasional marine beds 
intercalated among them. 
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