340 GEOLOGICAL SURVEY OF THE TERRITORIES. 



homogeneity in correlation with, the forces which have, at the same 

 time, modified the surface of our earth. The Upper Cretaceous, from 

 indications of the remains of a deep marine fauna, is positively char- 

 acterized as a deep marine formation. Immediately over it, the sand- 

 stone shows in its remains the result of the upheaval of a wide sur- 

 face, exposed to shallow marine action, as indicated by fucoidal life. 

 The upheaval continuing, this area is brought out of marine iniiuence 

 to be exposed to that of the atmosphere. It is a new land, cut in basins 

 of various size, where fresh water is by and by substituted to brine, 

 where vegetable life of another character appears, where swamps are 

 filling with clay by floating plants, where peat-bogs in their growth 

 form deposits of combustible matter, &c. To suppose that the marine 

 action is totally banished from such a land would demand the absurd 

 admission of an absolutely flat surface. Of course estuaries penetrate 

 into itat many x)laces 5 their waters feeding marine species, brackish 

 shells ; their bayous inhabited by Saurians, and their remains are 

 mixed with leaves of the trees growing on the borders and preserved 

 together in a fossil state, without impairing the true character of the 

 formation by what paleontology considers as types of different ages. 

 The surface of the Eoceue sandstone, before its separation from marine 

 influence, was of course uneven. This sandstone has therefore the gen- 

 eral characters of the Eocene, while in some troughs. Cretaceous species, 

 still living in deep water, may have left their remains in the sand. 

 Even if these remains were numerous, their presence does not change 

 the age of the formation. But on this subject, and in comparing our 

 Eocene sandstone to the other groups established by geology, we find, 

 in its abrupt and permanent separation from the Cretaceous, its litho- 

 logical compounds, its total barrenness from animal remains, at least 

 generally, and the homogeneity of its flora, reliable and constant char- 

 acters better defined than in any geological division admitted by science. 

 This sandstone formation is inexplicable. It can be compared to noth- 

 ing but to the millstone-grit of the Carboniferous epoch. How to 

 explain why, at once, animal life seems to disappear from the bottom 

 of the sea, to be superseded by marine vegetation ? May this change 

 have been caused, jierhaps, by a rapid increase of temperature of the 

 water brought up by the force acting to the upraising of the bottom 

 into laud, and afterward into chains of mountains ? 



Though it may be this change is evident and i)roves the geological 

 discrimination of the Eocene sandstone from the Cretaceous, a separation 

 the more remarkable that, from numerous observations, this sandstone is 

 reported constantly conformable to the Upper Cretaceous beds. As Dr. 

 Hayden remarks in his description of the Lignitic group of Nebraska,* 

 " When we bear in mind the fact that wherever this formation has been 

 seen in contact with the latest Cretaceous beds, the two have been 

 found to be conformable, however great the upheavals and distortions 

 may be, while at the junction there seems to be a comj^lete mingling of 

 sediments, one is strongly impressed with the probability that no im- 

 portant member of either system is wanting between them." 



This intimate connection of two sandstones of different ages appears 

 to be of frequent occurrence along the Pacific shores, and to have caused 

 some difference of opinion, and some confusion too, in reference to the 

 age of these strata. Professor Gab, in a very valuable x>aleontological 

 document, published in vol. 3 of the Proceedings of the California 



* Geological report on the explorations of the Yellowstone and Missouri Rivers, 1859 

 and 1860, p. 30. 



