142 GUIDEBOOK OF THE WESTERN UNITED STATES 
Montoya, and Fusselman limestones, Percha shale, Lake Valley, and 
Gym limestones, limestone of the Magdalena group, Lobo formation, 
Sarten sandstone, and Colorado shale. The southern slope consists 
of agglomerate, Sarten sandstone, and Colorado shale. Some rela- 
tions to the central and southern parts of the range are shown in 
Figure 3 
Cooks Peak consists of a large laccolithic mass of granodiorite 
porphyry which was intruded in a molten condition into the Lake 
Gooks Peak 
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FIGURE 33.—Sections across Cooks Range, N. Mex. Upper section, through 
Cooks Peak; lower, about 3 miles south of Cooks Peak. Base of sections, 
yry; Tag, agglomerate; Qbd, valley 
Gym limestone and Magdalena formation; Clv, Lake Valley limestone; Dp, 
Fusselman and El Paso limestone 
Valley limestone and adjoining strata. Several other large porphyry 
intrusions occur southwest and south of the high central area. 
On the west slope of the range northwest of Cooks Peak and in the 
slopes south of that peak the Sarten sandstone is exposed, overlain by 
shale of Colorado age (Upper Cretaceous). It contains fossils of 
Comanche age (Lower Cretaceous). This sandstone constitutes the 
prominent dip slope 2 miles south of Cooks Peak, which becomes 
Sarten Ridge to the south, where the Sarten sendaenad is underlain 
by the Lobo formation, the Gym and Lake Valley limestones,’ and a 
small amount of Perchs shale. 
* The Lake Valley limestone (e: early | formation of New Mexico. In this 
sedaseeaee which crops out in | region it is overlain by the Lobo forma- 
ces in t i isti 
= formation, and this in turn by also exposed on Goat Ridge and in the 
ym only 20 to 30/ deep hollow near the th end of 
feot thick, which is believed to be a Sarten Ridge, Rae 
