SUEVEY OF COLORADO AND NEW MEXICO. 67 



Oerillos is a high wall-like dike, and dipping southward from this, from 

 the Placiere Mountain, is a great thickness of the cretaceous shales ISlo. 

 2, passing up into laminated arenaceous shales, with fossils, then the 

 dark shales of JSTo. 4, ai^parently. The cretaceous beds incline thirty 

 degrees to fifty degrees. Inclining at a less angle, a series of coal strata 

 reveal their upturned edges, conforming perfectly to the cretaceous beds. 

 Passing up the Gallisteo, eastward, we observed the variegated sands 

 and sandstones, rising above the coal strata, and concealing them on the 

 northeast and east flanks of the Placiere Mountain, inclining at all angles 

 from five degrees to fifty degrees. These sandstones are of varied text- 

 ure, from a fine aggregate of quartz particles to a rather coarse pudding- 

 stone. In some of the beds there are irregular layers, of a dull, rusty 

 brown, concretionary arenaceous limestone, in which I searched in vain 

 for fossils. One of the most peculiar features of these beds, and one 

 which I have never seen in any group before, is the great variety of 

 colors, from a light reddish tint to a deep brick red, sometimes dull pur- 

 plish light, and very deep yellow, white, brown, drab, &c. The only 

 fossils I could find were enormous silicified trunks of trees. One of them 

 was so perfect that it looked much like a recent one, with a cavity run- 

 ning through it ten inches in diameter. I have named these beds the 

 Gallisteo sand group, as they are confined, so far as I know at 

 present, to the valley of the Gallisteo, although they pass under the 

 Santa Fe marls, and the northern limit is concealed from view. Kear 

 the road is a small dike, apparently thrust up between beds of sand- 

 stone, and inclining with them. East of the Oerillos, up the Gallisteo, 

 among the upper beds of that group, are several larger dikes, and theJ 

 basaltic rocks are poured over the recent tertiary beds. One of the 

 dikes can be seen a long distance, looking like a ridge of upheaval, ex- 

 tending a little north of east, far across the plain towards the south end 

 of the Santa Fe Mountains. The Oerillos are merely a dike, or a series 

 of dikes, forming a small independent range of mountains composed 

 entirely of eruptive rocks. On the south and west side, the cretaceous 

 beds flank them closely, while on the east and northeast side the Santa 

 Fe marls jut up against them. Occasionally, on the east side, a little 

 stream will cut through the marls, revealing the sandstones of the Gal- 

 listeo group. 



The outcroppings of coal on the northwest side of the Placiere Moun- 

 tains are of great interest. They were firot exposed in the center of the 

 little branches that run into the Gallisteo. The first one is about five 

 miles south of the Gallisteo. The coal is in the natural condition. The 

 following section of the strata was taken ascending : 



1. Laminated clay, with thin seams of sand passing up into carbona- 

 ceous clay, as a floor for coal. 



2. Coal very compact. The cleavage lines are, in a few instances, 

 filled with clay — 5 to 6 feet. 



3. Drab clay, indnrated, 15 to 29 feet. 



4. Ferruginous sandstone, passing up into a light grayish sand- 

 stone — 30 to 50 feet. 



The lower part of this bed is full of deciduous leaves. The debris is 

 so great that the real character of the beds is somewhat obscured. The 

 impressions of leaves, appear to belong to the genera Magnolia, Pla- 

 tanus, Salix, and others, some of which appear to be identical with 

 those found at the Eaton Mountains. Imperfect si)ecimens of a palm 

 were found. The mine is opened on each side of the dry creek, and the 

 dip is the same — about ten degrees. As in all the rocks of the country, 

 there are in the coal two sets of cleavage lines, at right angles to the 



