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Outcrops of limestone and(or) dolomite marble are present throughout the San Bernardino National Forest, California. Where possible, these Precambrian to Late Paleozoic carbonate rocks are divided into the Bonanza King Formation, the Nopah Formation, the Sultan Limestone, the Monte Cristo Limestone, and the Bird Spring Formation. Other carbonate rocks are mapped as the Furnace Limestone or as members of the Desert Divide Group and the Palm Canyon Complex where existing geologic data does not differentiate between the various limestone and dolomite units. Past mining in the national forest, combined with new geologic and geochemical data, indicate that all of the carbonate rocks within the San Bernardino National Forest have high resource potential for construction-grade carbonate rocks. These rocks have been quarried for roofing materials, construction stone, and industrial uses for more than 100 years; demand for these materials is expected to increase at an annual growth rate of 2-4 percent to the year 2000. White marble in the Bonanza King and the Nopah formations, the lower and middle members of the Bird Springs Formation, and marble in the Desert Divide Group have high resource potential for cement-grade carbonate rocks. The Crystal Pass Member of the Sultan Limestone and the middle member of the Monte Cristo Limestone have high resource potential for chemical-grade carbonate rocks. These high grade (high CaO, high brightness) marbles are used as fillers and extenders in the paper, paint, and plastics industries and yield the greatest per unit value of any of the carbonate rocks in the San Bernardino National Forest. INTRODUCTION Carbonate rocks, consisting of limestone (CaCOa) or dolomite (CaMg{CO3}2) marble, are present in the eastern San Gabriel, San Bernardino, and San Jacinto Mountains of the San Bernardino National Forest, California (fig. 1). These rocks have been quarried from the 1880s to the present day and produce several million tons of limestone-based products per year for the construction, cement, chemical, and pharmaceutical industries. Part of this national forest is adjacent to the Lucerne Valley Limestone Mining District, one of the largest limestone producing districts in the United States (fig. 1); gross sales from this district alone are $180-220 million per year (Fife, 1988). This report describes the geology and geochemistry of the carbonate rocks as well as carbonate-rock quarries, mines, and prospects in the San Bernardino National Forest; these data are used to assess the resource potential of carbonate rocks in the national forest. GEOLOGY AND GEOCHEMISTRY EASTERN SAN GABRIEL MOUNTAINS

Geology, geochemistry, and resource potential of carbonate rocks in the San Bernardino National Forest, California