I 



Mesozoic and Ccenozoic Geology and Palaiontology. 179 



A section at Navy Point, Benicia, exposes a tliickness of conform- 

 • able beds of sandstone conglomei"ate and shales a little more than 1,000 

 feet in thickness. The strata are uplifted, being inclined at an angle 

 of from 20 to 60 deg., and dipping toward the southwest. The trend 

 of the outcrops is 75 deg. west of north, and the strata underlie, or 

 rather form the hill upon which the government buildings are erected. 

 The ridge of conglomerate is the hardest and .most unyielding of all 

 the strata, and its resistance to abrasion and atmospheric influences 

 has determined the form of the hill and the shape of Navy Point. 

 It is prominent at several points, along the surface of the ground, 

 and is almost the onh'^ rock that appears above the soil in that 

 vicinity. The bed is about twenty-five feet thick, and is composed of 

 pebbles and gravel, very round, much water-worn, and chiefly derived . 

 from the wear of volcanic or eruptive rocks. Their colors are generally 

 dark; and porphyries, agates and carneliaus are abundant. Their 

 average diameter does not exceed an inch, and many are about the 

 size of beans and peas. They are closely united by a small portion of 

 finer materials. The strata on both sides of the conglomerate consist 

 of alternate beds of soft and friable ai'gillaceous shales, with an occa- 

 sional la3'er of gravel and pebbles. 



The wide development of the formation, and the great thickness 

 which it attains — pi'obably 2,000 or 3,000 feet — and the even grain of 

 the thick beds of sandstone over large areas, together with the re- 

 markable uniformity of the strata, indicate that they were formed in a 

 wide spread ocean or sea, and the thick beds of shale attest the depth 

 and comparative quiescence of the water. 



He found the Miocene rocks extending in a continuous belt along 

 the base of the Sierra Nevada, from White creek to Ocoya creek and 

 be_yond it for many miles to the southward, forming high banks on 

 both sides of Posuncula or Kern river, and even extending in a narrow 

 strip to the Tejon. 



Although by far the greater portion of the materials composing the 

 formation are extremel}' light, fine and unconsolidated, there are, in 

 some places, layers of sandstone and conglomerate, which offer more 

 resistance to the action of the w^eather than the other strata, and that 

 slightly modify the rounded contour of the hillsides. The principal 

 constituent of the formation is a fine gray sand, mingled, in some of 

 the beds, W'ith a considerable portion of clay, and alternating with 

 layers in which clay predominates. Volcanic materials, or sands de- 

 rived from their abrasion, constitute a large part of the strata. Thick 

 beds are formed almost wholly of white pumice stone, in rounded 



