LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON

CRETACEOUS SEDIMENTARY DIVISIONS
deposits found in the Sierra de Parras, including estimates of thickness
made by Iinky, in which the Lower Cretaceous sequence attains a maximum
of 5782 and 5020 feet. At Bisbee, Arizona, the sequence is said to
have a thickness of 4700 feet, including conglomerates, sandstones, and
shales. Estimates of the thickness of the Lower Cretaceous in Texas,
made by Adkins, shows a maximum of 4647 feet. In all these areas, and
in many others, limestones predominate, often forming nearly the entire
series. Lithologically the columns of the Lower Cretaceous in Mexico
and Texas contrast greatly with contemporary deposits in the detrital
Shasta series in the Sacramento Valley which attain a thickness of 13,000
to 27,000 feet. In Oregon corresponding beds have a thickness in some
areas of nearly 6000 feet, and in others apparently more.
The faunas of the Comanche series in Mexico and Texas show equally
great contrasts with those of the Shasta series, except that each series
contains a few genera of wide geographical range. The Lower Cretaceous
faunas in Mexico and Texas, and contemporary deposits in the northern
Andes (Colombia and Peru), pertain to the Tethyan-Mcditcrranean province,
whereas the faunas of the Shasta series are for the most part of Indo-
Pacific affinities, having closer relations with those of Australia and southwest
Asia (Cutch and Caucasus mountains). The lithological and faunal
contrasts in the Shasta and Comanche series have been noted by Stanton
(1897) and by others, but, in view of their bearing upon paleogeographical
problems, they should be further emphasized^ Only a generic resemblance
can be shown in the faunas of the older portions of the two series. Both
contain species of Okostephanus (Aslieria), Polyptyehites, Spiticeras,
Putehellia, Berriasella, Neocomites, Thvrmarmia., Bochianites, and perhaps
others. But such analogues do not reach specific resemblances and do
not often show close relationships.
In Barremian horizons there is a single species of Pulchellia known in
the Shasta; in Aptian strata there are species of ParahoplUes in both series;
and in Albian horizoriB there are forms of DmmUeiceras, Oxytropidaceraa,
and others, but the species are never identical and do not indicate direct
connections between Atlantic and Pacific waters during any epoch of
early Cretaceous time. The absence from the Shasta series of many
genera and families of cephalopoda characteristic of the Comanche&n
faunas has been noted by Stanton. No examples of Leopoldia or of
Acanihodiscus have been recorded from the older beds of the Shasta series,
nor have hoplitids of the lineage of Dufrenoya been found in the Barrcmiaii
of the Shasta. Echinoida are rare in the Shasta series, and there
are few forms of Ostreidae, caprinids, or monopleurids, all of which are
abundant in the Mexican and north Andean Lower Cretaceous. On the
other hand, the Tethyan Lower Cretaceous contains none of the heavyshelled
forms of Aucella or of the large species of Inoceramus common in
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