92 : GUIDEBOOK OF THE WESTERN UNITED STATES. 
Near milepost 39 is the termination of a narrow flow of lava, which 
appears to extend continuously from a source far up the valley. It 
widens in some places and narrows in others, and at intervals is covered 
in whole or in part by the alluvium or wash laid down by the stream. 
Suwanee station is on this lava sheet. A short distance to the 
southeast is a small mesa in which an older lava sheet 
caps buff sandstone (Dakota), shales (Morrison ?), and 
underlying gray and red massive sandstones (Zuni). 
Farther south is the precipitous edge of the lava sheet 
capping the high north end of the Mesa Lucera.' 
A fault of considerable magnitude is crossed a short distance west 
of Suwanee station and extends far north along the eastern mar- 
gin of the high plateau known as Mesa Gigante (he-gahn’tay, 
Spanish for gigantic). This fault is a vertical break in the earth’s 
crust along which the region to the west has been uplifted several 
Ww. E. 
Suwanee, 
Elevation 5,455 feet. 
Kansas City 968 miles 
Mesa Gigante = 
oO 
ad 
f- 
g ie 
FIGURE 17. Pica north of Suwanee, N. Mex., looking north, ce Apewak of faults. a¢, Dakota 
and over ——— and shales; b, shale probably equivalent nm formation; c, buff 
St ce: d, ne; e, gypsum 
massiv on hagas Tukey ri massive pink sand- 
stone teFegscones g; red ile and sandstones 
hundred feet, bringing into = a thick mass of red beds. The 
relations are as shown in 
Where crossed by the railway ae fault is ‘covered by lava because 
the lava occupies a valley that was excavated long after the earth 
movement had taken place. North of the railway and west of the 
fault rises the Mesa Gigante, which is capped by massive gray to buff 
sandstones (Dakota and overlying Cretaceous). Below the sand- 
stone cliffs are banks of shale or clay, in greater part of pale-greenish 
tint eee equivalent to the Morrison formation), descending to 
long s extensive cliffs of red sandstones and shales. These 
red cliffs are very conspicuous, notably from points near Armijo 
(ar-me’ho) siding and for some distance westward. 
1A mile north of Suwanee on the north 
side of the valley is a long ridge of mod- 
erate height cap sandstones 
Paes) ‘surmounting slo of light 
opes 
clays probably equivalent 
: i Wik Meatins fonnn tion. These cla 
are in turn underlain by a thick layer of 
massive buff sandstone, and in the bottom 
of the valley, not in view from the train, 
the top of a 50-foot bed of the underlying 
gypsum is exposed inasmallarea. Small 
faults which extend northward into the 
the east and 
ys | ridge at this place cut off the gypsum on 
