J. J. Stevenson— Geology of Galisteo Creek. 473 
whole region south from Denver, except that Halymenites major, 
so common at the base of the Laramie group in the Trinidad 
coal field, is absent here. But impressions of dicotyledonous 
plants occur in the Galisteo region, which are closely allied to 
those found in the Trinidad coal field. The coal beds on the 
northeast slope of the Placer mountains are as clearly Laramie 
as are those of the Trinidad or the Cafion City coal field. 
But the geology of the upper Galisteo area is far from being 
so simple as that observed along the south side of the creek 
within the lower area. 
No reference has been made to the north side of the creek 
within the lower area; that can be considered more conven- 
iently in connection with the upperarea. A broad uneven park, 
designated on the Engineer map.as the Arroyo de Los Angeles, 
opens into the lower area at perhaps five miles below Galisteo, 
and the dike, previously referred to, forms its southeast bound- 
arv for several miles. 
If a section be carried across the area of the upper Galisteo 
near its southern edge, the conditions will be found such as are 
represented in the following diagram. 
5 
t 
Cross SECTION ON THE UPPER GALISTEO. 
1. Dakota. 2. Colorado. 3. Laramie. 4. Galisteo. 5. Alluvium, 
The Upper Dakota sandstone is in the bluff on the east side, 
where the dip is very rapid; behind it are the shales and lime- 
stones of the Middle Dakota, and the sandstones of the Lower 
low insignificant roll, separating the Arroyo de los Angeles 
from the Galisteo, is reached, the Laramie rocks are dipping 
But on the opposite side of this low divide, the Lower Da- 
kota sandstones are exposed and 
dip westward at 65°; at but a 
the Arroyo and the 
side of the Arroyo, — 
