14 CAKHONIKKROUS KOKMATIONS AND FAUNAS OK COLORADO. 



nil abstract nl' tlic work of the Ilaydcn surxcy, in which nian_y of the errors coniinit- 

 Icd liy Kiiillich arc n»pcatc(l. 'rims the early l*ahH)zoics are described as having 

 furnished the material out of which the " metamorphic series" was formed, while ail 

 the Upper Carhouiferous beds, which were later called the Hermosa formation, are 

 referred to the Lower Carlioniferous.- Probably, however, this term is here 

 euqiloycHl in tlie oiiji'ctional)le sense in which it was used ]>y the Haj'den survey — to 

 indicate the lower portion of the Carl)oniferous section of any particular I'egion. 

 Broadhead's paper on the .Juratrias, published this year, concerns us in that some of 

 the strata called Juratrias in Colortido are probably Carboniferous. On the other 

 hand, his paper is a summary or digest of the literature, practicall}' without discus- 

 sion, conclusion, or new matter of any sort. Of a similar bibliographic nature is T. S. 

 Hunt's description of the progress of geology for 1882. It is of subsidiarj^ intei'est 

 to this resume as containing an abstract of the results of Emmons's Leadville work. 

 A paper by Hallowell, entitled "Supposed Juratrias of the Front Range," seems to 

 be an effort to prove that no Juratrias exists along the Front Range of Colorado 

 and that the rocks called such actuallj^ overlie the Cretaceous. 



In 1884 little or nothing beai'ing upon the matter in hand was published, and in 

 1885 only papers of a less important kind. In the latter year Emmons, in his report 

 upon the Rocky Mountain division, calls attention to two unconformities, one pre- 

 Jurassic, the other intra-Carboniferous, which had not previously been detected. 

 These were observed in the Elk Mountains, and were later discussed and represented 

 in the Anthracite-Crested Butte folio. 



The important event of the year 1886, so far as it concerns this subject, was the 

 publication of Emmons's Leadville monograph. This work will of course receive 

 attention in the resume. The other publications of the year are of minor importance. 

 Stevens briefl}- describes the geology of the San Juan region in a report which adds 

 little or nothing to the Hayden survey. Emmons somewhat casually describes the 

 section at Red Cliff in which the Sa watch, Yule, and Leadville formations are said to 

 occur. 



In 1887 appeared a number of papers of the less important sort. Comstock 

 described the geology and vein sti-ucture of a large area in southwestern Colorado in 

 a paper which will be discussed later on in the resume. Olcutt described the Battle 

 Mountain mining district of Eagle County, giving the geologic section observed 

 there. To one familiar with the sequence in central Colorado the Paleozoic charac- 

 ter of these beds is clear, but the author makes no attempt to correlate them with 

 other sections or to fix their geologic age. Lakes described the geolog}^ of the Aspen 

 district in a paper which will be referred to later. A map of the United States by 

 Hitchcock appeared this year, and to this I have already made general reference. 

 Areas of Carboniferous (called Permo-Carboniferous) are shown in Colorado some- 



