14 



LARAMIE FLORA OF THE DENVER BASIN. 



Survey, who extended its application to west- 

 ern Colorado and adjacent areas. After the 

 death of Meek the mantle of invertebrate pale- 

 ontologic work fell largely upon the shoulders of 

 C. A. White, and he had a large part in extend- 

 ing the application of the Laramie. In the 

 ' seventh of his " Paleontological papers " 61 he 

 gave the following range for Laramie as he then 

 accepted it: 



The term Laramie group is here used to include all the 

 strata between the Fox Hills group of the Cretaceous 

 period beneath and the Wasatch group (= Vermillion 

 Creek group of King) of the Tertiary above. That is, it 

 includes, as either subordinate groups or regional divisions, 

 both the Judith River and Fort Union series of the upper 

 Missouri River; the Lignitic series east of the Rocky 

 Mountains in Colorado; the Bitter Creek series of southern 

 Wyoming and the adjacent parts of Colorado; and also 

 the "Bear River Estuary beds," together with the Evan- 

 ston coal series, of the valley of Bear River and adjacent 

 parts of Utah. Strata of this great Laramie group are 

 known to exist in other large and widely separated dis- 

 tricts of the western portion of the national domain. 



Later the Laramie was believed by White to 

 have been recognized as far south as the States 

 of Chihuahua, Coahuila, and Nuevo Leon, 

 in northern Mexico. It was also adopted by 

 the Canadian geologists and shown by them to 

 extend over a vast area in the British posses- 

 sions. In fact, as late as 1891, after a number 

 of important horizons had been rempved from 

 the confines of the Laramie, White 52 gave the 

 following as the recognized distribution of the 

 formation: 



The present geographical outlines of the area within 

 which strata of this formation occur are not yet well known, 

 but it apparently is as great as that within which any other 

 North American formation has been observed. Their 

 presence has been recognized at so many and such widely 

 separated localities that they safely may be assumed to 

 once have formed a continuous deposit from near the 

 twenty-sixth to near the fifty-fifth parallel of north latitude 

 and in certain districts from near the one hundred and 

 third to near the one hundred and fifteenth meridian. 

 That is, it is evident that this formation originally con- 

 sisted of a continuous deposit nearly or quite 2,000 miles 

 long from north to south, and more than 500 miles across 

 from east to west. 



The, structural and lithologic character of 

 the Laramie as it was then (1891) accepted was 

 well set forth by White, 53 who wrote as follows : 



u White, C. A., On the distribution of molluscan species in the Laramie 

 group: TJ. S. Geol. and Geog. Survey Terr. Bull., vol. 4, No. 3, p. 721, 

 July 29, 1878. 



61 White, C. A., Correlation papers — Cretaceous: TJ. S. Geol. Survey 

 Bull. 82, p. 145, 1891. 



« Idem, p. 146. 



In lithological character the Laramie formation is re- 

 markably uniform throughout both its geographical and 

 vertical extent, and it seems everywhere to have been the 

 result of continuous sedimentation from base to top. Its 

 strata within the whole of the great area which they occupy 

 are mostly composed of sandy material, but frequently 

 they are more or less argillaceous and rarely calcareous. 

 Sandstones of much firmness often occur among them, but 

 a large part of the sandy strata are soft and friable. Shaly 

 strata not infrequently occur, and these are often carbona- 

 ceous. The formation throughout its whole extent is coal- 

 bearing. 



The question concerning the Laramie which 

 gave rise to the most extensive discussion and 

 difference of opinion was, of course, that of its 

 age. It may be of interest to present a brief 

 recapitulation of the divergent views on this 

 point that had been promulgated up to about 

 1890, or approximately to the time when, if it 

 is permissible to use the expression, the reac- 

 tion set in, and the pendulum began its back- 

 ward swing as regards what should or should 

 not be included within the limits of this forma- 

 tion — the point that subsequent investigation 

 has shown is the cause of much of this differ- 

 ence of opinion. 



King and the other members of the Fortieth 

 Parallel Survey regarded the Laramie as of 

 Cretaceous age and the equivalent of the 

 Lignitic group of Hayden. The term was 

 immediately accepted by Hayden and the 

 members of the Survey under his direction, 

 though not wholly as a substitute for the 

 earlier "Lignitic," for they admitted un- 

 doubted Cretaceous coals. Hayden regarded 

 the Laramie as transitional between Cretaceous 

 and Tertiary. Endlich, from his studies in the 

 vicinity of Trinidad, Colo., referred the coal- 

 bearing rocks of the region (= Laramie) to 

 post-Cretaceous or pre-Tertiary.' White, End- 

 lich, and Peale, who investigated the Laramie, 

 especially in Utah, Wyoming, and Colorado, 

 called it post-Cretaceous, and White in partic- 

 ular stated his belief that it was transitional 

 between Cretaceous and Tertiary. Stevenson 

 and Newberry also were familiar with the areas 

 in southern Colorado and New Mexico and 

 were firm in their belief that it was Cretaceous. 

 The vertebrate paleontologists Cope, Marsh, 

 and many others after them referred the Lara- 

 mie unqualifiedly to the Cretaceous, largely on 

 the ground that it contained remains of dino- 

 saurian reptiles that were believed to be an 

 unfailing mark of Cretaceous age. On the 

 other hand, Lesquereux, from his extensive 



