Core logs from Bristol, Cadiz, and Danby Dry Lakes, San Bernardino County, California

Detailed core logs of four holes drilled in Bristol, Cadiz, and Danby Dry Lakes in southeastern San Bernardirio County, Calif., are given in the present report. These 3 dry lakes lie in a chain of basins having a drainage area of 4,000 square miles which is made up of alluvial slopes and of mountains composed of granitic, metamorphic, and volcanic rocks. Rainfall in the basins averages less than 3 inches annually.

In Bristol Dry Lake, 1 hole was drilled to a depth of 1,007 feet, and penetrated layers of dense clay alternating with salt. About 40 percent of the recovered core is halite, ranging from scattered crystals in clay to massive beds more than 8 feet thick. In Cadiz Dry Lake, 1 hole was drilled to a depth of 500 feet. The core is composed of clay, silt, and sand, with scattered gypsum crystals in small quantities, and a single salt layer, 1 foot thick, lying about 9 feet below the surface. Bedding in this core is horizontal down to a fracture at a depth of about 256 feet; from there to the bottom, the dip increases gradually to a maximum of 35°. In Danby Dry Lake, 2 holes were drilled: the first and more northerly one to a depth of 880 feet and the southerly one to a depth of 460 feet. 'Both cores are composed of clastic sediments ranging from clay to coarse sand with fine sand the most abundant. Crystalline gypsum in silt occurs between 310 and 520 feet in the northern hole and between 278 arid 334 feet in the southern hole. The northern hole was drilled in gravel for the last 20 feet. No salt beds were cut in either of the Danby holes despite the occurrence of commercial salt deposits elsewhere on the surface of the playa. Correlation of sediments between any of these cores, even between those from the same basin, is difficult and seldom convincing.

Fossils were found in the Cadiz core and in both Danby cores. The most abundant fossils are Chara, the calcified seeds of the Charophyta algae. Foraminifers, ostracodes, gastropods, pelecypods, and barnacles, in order of decreasing abundance, occur at rare intervals in these three cores.