GEOLOGY. 
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inclined slightly toward the ocean or the line of drainage, and ranging 
in size from tens of square miles to only a few feet square. The more 
extended terraces fringe the coast line and the larger valleys and 
cover areas of low hills. The smaller ones are scattered over ridges 
and hilltops and along the smaller valleys. These terraces are cov¬ 
ered with a thin coating of sand and gravel, and here and there with 
clayey material. The distribution of the deposits is well shown on 
the map, with two general exceptions. In the first place, many of 
the strips of land along valleys mapped as covered with terrace 
deposits may not represent true terraces, as it is almost impossible 
to draw definite distinctions between such horizontally bedded val¬ 
ley fillings, true terrace cappings, and recent alluvium. All post- 
Fernando deposits in small valleys are therefore mapped with the 
terrace formation, and alluvium is shown only in the extended valley 
bottoms, where dividing lines between it and the terrace deposits are 
drawn arbitrarily. In the second place, owing to the lithologic simi¬ 
larity of the Fernando and the terrace-deposit sand and the similar 
surface appearance of these two formations, the attempt has been 
made to represent on the map only a few areas of the terrace sand 
overlying the Fernando. The Fernando is doubtless capped by ter¬ 
race deposits in many places, but it is usually impossible to tell 
whether this is true or not. The lines of contact between these for¬ 
mations are of necessity arbitrarily shown. 
This similarity causes much difficulty in places in determining 
whether the deposits belong to the Fernando or to the later epoch, 
and whether it is necessary to go through a great thickness of Fer¬ 
nando beds or only a few feet to reach the Monterey below. Where 
fossils, distinct lines of bedding, or tilted strata are present they are 
indications that the sand belongs to the Fernando. 
The terraces are found commonly at all altitudes up to 1,200 reet, 
and a few even as high as 1,400 feet. None have been definitely rec¬ 
ognized at a higher elevation. 
LITHOLOGIC CHARACTER. 
The material of the terrace deposits is usually sand and conglomer¬ 
ate, for the most part the former. The sand is medium grained and 
contains scattering waterworn pebbles. It is normally soft and 
grayish, but in many places compact, being stained a reddish yellow 
and hardened by iron oxide or filled with iron-stained concretions. 
In this surficially compacted state it forms hard cappings on hilltops 
and slopes. Round, bullet-like, iron-hardened concretions are char¬ 
acteristic of the derived soil. Over much of the surface of Burton 
Mesa and in other places this deposit occurs as loose, grayish sand, 
hardened locally by the action of rain water and various salts or 
oxide of iron. The conglomerate—or gravel, as it might equally well 
1784—Bull. 322—07-5 
