9? CALIFORNIA ACADEMY OF SCIENCES [Proc. 4TH SER. 
are sometimes plentiful. Marine invertebrates, which are 
abundant south of Poso Creek, are much less abundant to the 
north. 
On Caliente Creek, and about the junction of this stream 
with Walker Basin Creek, sands, gravels, and conglomerates 
make up a much larger part of the series, but the conditions 
here are in several respects local, as will be shown later. 
Volcanic materials make up a considerable part of the entire 
Temblor group in this locality. 
To the north of the Kern River the concretionary beds of 
the basal member are usually more fossiliferous than other 
parts of the strata, and probably for that reason are harder 
and more resistent. In the weathering of the beds, however, 
the concretions usually disintegrate somewhat, often releasing 
the fossils in almost perfect condition. 
As far as can be determined from well-records, this member 
of the Neocene series is much thinner in the western part of 
the field than in the outcrops; and this is not surprising, since 
the westerly stations represent points that were farther off 
shore. 
Upper Member.—The upper member of the Temblor group, 
or the portion above the general level of 600 feet from the 
base, as shown in the outcrops and in the records of the deep 
wells, contains a smaller percentage of sand and other detrital 
matter, and a greater percentage of organic material than any 
other portion of the Neocene. And of the detritus present a 
greater portion is of clay and shaly matter. 
In this member clays and shales probably form in the out- 
crop about 50 per cent of its volume, and of this percentage 
about one-half is organic. Some layers are chiefly composed 
of diatomaceae and other minute organisms. In the deep 
wells the sands are replaced by clays, and the strata are 
correspondingly reduced in volume, but more strongly char- 
acterized. The reason for this is to be found in the relation 
to the Miocene shore line. The percentage of organic matter 
in the strata is of course not readily known from the well- 
records, but that organic matter is present has already been 
shown. 
Thick deposits of diatomaceous and other predominantly 
organic shales, such, for example, as the white siliceous shales 
