GEOLOGICAL SURVEY OF THE TERRITORIES. 89 



same mysterious carvings. These soft sandstones, or chalky limestones, 

 are well adapted for recording their hieroglyphical history. 



But these rocks bear upon them far plainer characters than those de- 

 scribed above, and characters which carry the history of events infi- 

 nitely farther back into the past than any ever carved upon stone by hu- 

 man hands. Near the Blackbird Mission, and in other localities above 

 and below this place, has been found a remarkable series of fossil plants 

 embedded in the sandstones and quartzites, which has thrown much 

 light upon the ancient tlora of this region. These sandstones all belong- 

 to the lower cretaceous or chalk period, and it is now well ascertained 

 that with the beginning of that era, began upon our continent the dawn 

 of existing deciduous fruit and forest trees, as did also the present race 

 of edible fishes, as the herrring, perch, &c. We find impressions 

 of leaves in rocks, remarkably well preserved, representing the genera 

 Platanus, Populus, Fagus, Liriodendron, Sassafras, Magnolia, Fieus, and 

 others. Some of these plants indicate a warmer climate at one time in 

 this region than at present, though hardly tropical, or, as Dr. Newberry 

 has shown, not even sub-tropical, although on the Pacific coast species 

 of the palm and cinnamon, indicative of a tropical climate, are found. 

 It may be that when these rocks are more thoroughly studied, plants 

 of a tropical or sub-tropical character will be found. I take pleasure 

 in transcribing the following paragraph from Dr. Newberry's able report 

 on these plants: 



At the base of the cretaceous series in New Jersey, occur a coarse, soft sandstone 

 and beds of sandy clay which contain a large number of fossil leaves, many of which, 

 collected by Professor George H. Cook, of New Brunswick, by Messrs. Meek, Haydeu, 

 and others, have been submitted to me for examination. Unfortunately most of these 

 leaves are inclosed in a material so coarse and friable that they have been much broken 

 and are scarcely susceptible of accurate study. They form, however, quite a rich flora, 

 which includes a number of species not yet obtained from the cretaceous beds of the 

 West, with others that are apparently identical with some obtained by myself on the 

 banks of the Whetstone Creek in Western Kansas. Among these plants is a beautiful 

 conifer, generically new, as indicated by its cones, which are in a good state of preser- 

 vation. The plants from this district have not as yet been carefully studied, and they 

 form an attractive subject for future investigation. In the circumstances of their fos- 

 silization they resemble the plants of the West, and apparently indicate an invasion 

 of the ocean, occasioned by a subsidence by which the limits of the continent were con- 

 tracted, but to what extent on its eastern margin, we have no means of determining 

 accurately. 



By referring to the list of plants on a preceding page it will be seen that the cre- 

 taceous strata of the west eoast include some forms not yet discovered in the Kansas 

 and Nebraska beds. Among these, Salisburia, Sabal, Cinnamomum, &c, are indicative 

 of a warm climate. Possibly these genera may hereafter be detected in the plant beds 

 of Kansas, Nebraska and New Mexico, but as yet we have no intimation of their exist- 

 ence, and there is nothing now known in the cretaceous flora of that region which 

 gives it a tropical or even sub-tropical character. 



It will be remembered that this vegetation grew upon a broad continental surface 

 of which the central portion was considerably elevated. This would give us a physical 

 condition not unlike that of the continent at the present day, and it would seem to be 

 inevitable that the isothermal lines should be curved over the surface somewhat as 

 they are at present. It may very well happen, therefore, that we shall find the palms 

 and cinnamons restricted to the western margin of the cretaceous continent. It will 

 be seen by the notes now given of the tertiary flora of our continent that at a later 

 date palms grew in the same region where these cretaceous plants are found, but cin- 

 namon and other tropical plants seem to be entirely wanting in the tertiary flora of the 

 central parts of the continent, while on the west coast both palms and cinnamons 

 lived during the tertiary period as far north as the British line. We have, therefore, 

 negative evidence from these facts — though it may be reversed at an early day by 

 further observations — that the climate of the interior of our continent during the 

 tertiary age was somewhat warmer than during the cretaceous period, and that during 

 both the same relative differences of climate prevailed between the central and western 

 portions that exist at the present day. 



Near the entrance of the Big Sioux River into the Missouri the 



