TERTIARY AND* POST TERTIARY. 
83 
Sandstone of the Cajon Pass. —A description of the sandstone which outcrops at angles of 20 
to 45 degrees in the upper portions of this pass, has already been given. It is probably of Ter¬ 
tiary age. The Tertiary strata forming the slope from the mountains to the coast, have also 
been described. (See Chapter V.) The strata supposed to he Tertiary are thus seen to he prin¬ 
cipally developed over the western portion of the line—the portion west of the last exposure of 
the carboniferous limestone. This observation is made under the supposition that Tertiary 
strata are not found to surmount the Llano or the other table-lands on either side of the mount¬ 
ains. We have also seen that little knowledge of the lithological characters of the formation, 
its thickness and extent, has been obtained. The strata along the Colorado and its principal 
tributary, the Hawilliamook, appear to be very similar or constant in their character, being 
chiefly formed of red sandstone and conglomerate. It is very probable that these beds are the 
equivalents of the deposites I examined on the eastern side of the mountains at the head of the 
California gulf, where a thick bed containing Ostrea, Anomia and Pectens was found. 
POST TERTIARY. 
The formations included under this head are those of recent origin, the alluvial deposites of 
the rivers and the banks of detritus or wash which surround the mountains and fill the valleys 
of the Great Basin. These deposites are so local in their character, and differ so greatly accord¬ 
ing to their locality, that they cannot be included in one general description. It is not, there¬ 
fore, necessary to repeat the observations already made upon the alluvium of the Mississippi, 
nor many other notices of the recent deposites along the route. 
Mr. Marcou, in his notes, makes frequent mention of the alluvial and “ diluvial ” deposites 
he met in each day’s travel. These superficial accumulations appear, in some cases, to be 
abundant, and merit attention. A description of the deposites between Delaware mountain 
and the Antelope hills will be found in Chapter II ; but I present here notices of the most 
interesting deposites recorded between Antelope hills and the Sandia and Albuquerque mount¬ 
ains. Immediately after passing the Antelope hills, Mr. Marcou found several rolled masses of 
volcanic scoria of the size of the fist and head. Sand, with some alluvial pebbles, was found 
beyond, as far as Camp 36. This same deposite appears to have extended beyond Camp 36, for 
on the following day w r e find the presence of sand and alluvial pebbles of quartz noted. Be¬ 
tween Camps 31 and 38 “diluvium, from the size of a hazel-nut to that of the fist, with some 
masses as large as the head,” was seen. Those masses were, however, of white sandstone and 
limestone, which probably came from the strata in the vicinity. Between Camps 38 and 39 the 
diluvium is said to have been abundant, the pebbles being as “ large as a gourd.” Again, 
near Camp 40 the diluvium is said to have consisted of beds of sand and sandstone, containing 
the pebbles of the diluvium of the “ Rocky mountains.” Two or three miles before reaching 
Camp 41 a great number of hillocks of sandy diluvium were encountered. Between Camps 43 
and 44 we find it noted that the diluvium of the Rocky mountains is abundant and thick on all 
the plateaux. After reaching the bluffs of the Llano or their vicinity, the alluvium appears to 
have been much less abundant, and its absence is several times noted. It was not found again 
until the valley of the Galinas was reached, where a “ diluvium” of granite and trap rock was 
abundant, and it also forms hills between the Galinas river and the Pecos. 
At a point near Red river and nearly south from the Antelope hills, Dr. Shumard found large 
quantities of “ drift,” composed principally of quartz and mica-schist; on Red river, sandstone 
strata were overlaid by “ drift” forty feet thick. Again near the outcrop of the upraised sand¬ 
stones, near Suydam creek, the surface was thickly covered with drift. From this point drift 
is constantly noted along the trail westward towards the bluffs of the Llano. It will be ob¬ 
served, by consulting Captain Marcy’s map, that this region is directly south of and near the 
valley of the Canadian. At one place the drift contained agate, chalcedony, and fossil-wood. 
Dr. Shumard’s observations on the Llano differ greatly from those of Mr. Marcou, made at a 
