Abstract The San Gabriel anorthosite-syenite-gabbro body is exposed in the western San Gabriel Mountains about 30 mi (48 km) north of Los Angeles (Fig. 1). The most abundant lithologies of this body, which constitute the anorthosite-leucogabbro unit, are easily accessible via Angeles Forest Highway (N3) along Mill Creek about 18 mi (28.8 km) south of Palmdale (Fig 11, 2A). However, many of the most interesting lithologies of this body can be seen only by driving several mi (km) on U.S. Forest Service roads into he central part of the body west of Angeles Forest Highway. These localities can be reached from Angeles Forest Highway by driving west from Mill Creek Summit, past Mt. Gleason, to North Fork Saddle, and on down Pacoima Canyon. Alternately, they can be reached by driving east either from Santa Clara Divide or from Dillon Divide on the Sand Canyon-Little Tujunga Road (Fig. 1). A second important group of lithologies constitutes the syenite unit and can be seen near “Sold” on the North Fork Saddle-Magic Mountain-Mount Gleason road (Figs. 1, 2B). This road is usually in good condition and is easily passable by conventional automobile except between December and February, when it is occasionally covered by snow at higher elevations. A third important group of lithologies constitutes the Jotunite unit and can be seen along Pacoima Canyon (Fig. 2C). The road through Pacoima Canyon, reached from either Dillon Divide or North Fork Saddle (Fig, 1), is rough and may require use of a four-wheel-drive vehicle during winter and spring.

Abstract The San Gabriel anorthosite-syenite-gabbro body is exposed in the western San Gabriel Mountains about 30 mi (48 km) north of Los Angeles (Fig. 1). The most abundant lithologies of this body, which constitute the anorthosite-leucogabbro unit, are easily accessible via Angeles Forest Highway (N3) along Mill Creek about 18 mi (28.8 km) south of Palmdale (Fig 11, 2A). However, many of the most interesting lithologies of this body can be seen only by driving several mi (km) on U.S. Forest Service roads into he central part of the body west of Angeles Forest Highway. These localities can be reached from Angeles Forest Highway by driving west from Mill Creek Summit, past Mt. Gleason, to North Fork Saddle, and on down Pacoima Canyon. Alternately, they can be reached by driving east either from Santa Clara Divide or from Dillon Divide on the Sand Canyon-Little Tujunga Road (Fig. 1). A second important group of lithologies constitutes the syenite unit and can be seen near “Sold” on the North Fork Saddle-Magic Mountain-Mount Gleason road (Figs. 1, 2B). This road is usually in good condition and is easily passable by conventional automobile except between December and February, when it is occasionally covered by snow at higher elevations. A third important group of lithologies constitutes the Jotunite unit and can be seen along Pacoima Canyon (Fig. 2C). The road through Pacoima Canyon, reached from either Dillon Divide or North Fork Saddle (Fig, 1), is rough and may require use of a four-wheel-drive vehicle during winter and spring.