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of the basin {pl. 1), has an average annual temperature of 61. 2° F. ,

the recorded temperatures ranging from 19° F. to 104° F. The average

monthly temperatures range from 44. 1° F. in January to 81. 4° F. in

July. These temperatures are believed to be typical of the Soledad basin.

The high summertime temperatures are alleviated somewhat by prevail-

ingly low humidity and a daily west wind.

Greasewood, buckthorn, manzanita, yucca, and sage are the

most abundant shrubs and are grouped under the term chaparral. Syca-

more, cottonwood, and oak are the principal trees, and are locally

abundant along the streams and near springs. Brush fires have burned

off large areas of the basin. The chaparral on the Sierra Pelona is, in

places, so dense that it is almost impossible to penetrate by a geologist.

II. BACKGROUND OF INVESTIGATIONS

Evolution of geological thought on the northern Soledad basin

The Ventura basin is a narrow, elongate trough, which

extends from Ventura on the Pacific Coast eastward for nearly 60 miles

to the vicinity of Palmdale, which lies along the western margin of the

Mojave Desert. Except for the north border, the westward continuation

of the basin is, at present, beneath the surface of the Pacific Ocean.

During much of Cenozoic time, an arm of the sea, named the Santa

Barbara embayment, extended for many miles eastward into the Ventura

basin.