TERTIARY COAL MEASURES OF GUNNISON COUNTY, COL. 691 



ing in contact with the organic matter in the then sea-bottom, was precipitated, 

 and also by the gradual cooling of the waters. 



Here this section for a time was stationary, and the sands gradually filled 

 these watery depths until another shallow sea was repeated, and a subsidence 

 followed which washed all of the loose moveable soil of the adjoining lands and 

 islands into the deep sea. This material made the mud deposit — shales now — 

 which follows the sandstone. On these muds in shallow water the growth of the 

 coal plants again commenced, to be followed in repetition by what has already 

 been shown; and this was repeated six different times, for eighteen different sub- 

 sidences and periods of rest are now shown to have occurred here locally ; per- 

 haps more, if we could get at the deepest part of any one of these basins. The 

 strata built up, as near as I could ascertain, aggregate 1500 feet in thickness. 



Then followed a greater subsidence at once than at any single time previous ; 

 a wider area of territory was acted upon by deeper waters; and instead of sand- 

 stones, resulting from precipitation, we have 1000 feet of conglomerate, which 

 covered all of the named mountains of granite porphyry. 



This Tertiary age was closed by the eruption of the lava showing on the di- 

 viding ridge between Ohio Creek and East River near Howville or Jack's Cabin. 

 Subsequent erosion shows this lava on top of the Tertiary sandstones, and sub- 

 sequent erosion has worn down these sedimentary rocks deposited in the old 

 mountain gorges between peaks and ranges of granite porphyry, laying clear the 

 structure from the latest strata to where it began, and all to be seen and reasoned 

 out as I have shown. 



Now for the anthracite. I spent two days on Anthracite range, camping out 

 to get at the following : Standing on the top of this range, it could be seen that, 

 at the time of the recent or lava eruption, a deep gorge or crevice had opened 

 frorh the eruptive point through between Wheatstone group and Mount Carbon. 

 This opening came against the end of the Anthracite range, with the effect of 

 setting or splitting off a single mountain mass by itself. This crevice, evidently, 

 was also filled with eruptive matter, not coming to the surface, but exerting 

 force and pressure sufficiently to slowly crowd this single mountain northward, 

 which in its turn pressed against the coal measure strata built up at its feet and 

 against its sides with such force that these originally horizontal sedimentary rocks 

 were raised to an angle of twenty-one degrees. The heat and pressure generated 

 by this rock movement metamorphosed a coal-bed under 2000 acres from a bitu- 

 minous coal to a four-foot vein of the finest anthracite that is now known. Here 

 geology and chemistry agree, and at this point, I think, Mr. Charles Henry 

 Baker, M. E., is answered that it is anthracite. 



The eruption of this lava raised the Tertiary beds so that all of the strata dip 

 away from the lava outcrop, eight and one half feet in each 100 feet; although in 

 the Ohio Creek basin, I think, from what I saw, that the dip gradually increases 

 as the lava mesa is approached. The sedimentary rocks broke in short cross- 

 sections ; along these breaks, lines of erosion now exist, wearing the surface into 



