638 W. T. LEE STRATIGRAPHY OF COAL FIELDS OF NEW MEXICO 



inches or more in length. The shells are fragile and crumble so easily 

 that none were collected. They appear to be the same species that the 

 writer has observed in many places near the center of the Mancos shale 

 west of the Eocky Mountains and near the middle of the Pierre shale 

 east of these mountains. 



The upper part of the Mancos shale formation consists of sandy shale 

 about 700 feet thick which may be the time equivalent of the relatively 

 thin sandy transitional beds at the top of the Mancos in other places. 

 The fossils contained in it (number 7177) do not differ from those of 

 the overlying Mesaverde formation. 



The line of separation between the Mancos shale and the Mesaverde 

 formation is here drawn at the base of the massive yellow sandstone above 

 which the coal beds occur. The lower part of this formation is not con- 

 tinuously exposed at Hagan. It consists of sandstones that form promi- 

 nent ridges and these ridges are separated by depressions in which softer 

 rocks, presumably shale, are poorly exposed. The sandstones are more or 

 less lenticular and no one of them has been traced for any considerable 

 distance. They weather to a rusty yellow color and contain irregular 

 masses of earthy limestone in which great numbers of fossil shells were 

 found. These are named in the accompanying section. They do not 

 differ materially from those found in the shale below. In other words, 

 the rocks here referred, principally on lithologic characters, to the top of 

 the Mancos, and those referred to the base of the Mesaverde are faunally 

 not distinguishable. 



The upper part of the coal-bearing rocks of the Mesaverde are well 

 exposed near Hagan mine and contain several beds of coal, two of which 

 have been opened at the mine. Alternating with these beds are layers of 

 carbonaceous shale and chocolate-colored sandstone, in which are fossil- 

 iferous concretions of yellow calcareous sandstone similar in general ap- 

 pearance to the concretions at which contain the marine shells at lower 

 horizons. The concretions lying just above the principal opening of the 

 Hagan mine yielded the fossil plants of Mesaverde age (number 6023) 

 named in the section. Leaves and large petrified tree trunks occur at 

 somewhat lower horizons. 



The shale between the coal beds contains large crystals of selenite, and 

 this shale, as well as the sandstone associated with it, does not differ in 

 general aspect from the beds of marine origin immediately below the 

 coal. The shaly rocks, about 600 feet thick above the main coal beds, axe 

 more variable in constitution than those at lower horizons. The lower 

 part of this shale contains great numbers of concretions of earthy lime- 

 stone ; near the top it is more carbonaceous and in some places contains 



