Unit is named the Fisher Spring Sandstone Member of the Ridge Route Formation of the Ridge Basin Group. Exposed in the central Ridge basin, Los Angeles Co., CA. Is one of five major clastic tongues of the Ridge Route Formation that cross the basin. Consists of light-brown medium-grained, arkosic sandstone interbedded with mudstone and conglomerate and contains freshwater mollusk, ostracode, and vertebrate fossils suggestive of nonmarine lacustrine-fluvial conditions. Conformably overlies the Paradise Ranch Shale Member (new), and conformably underlies the Osito Canyon Shale Member (new), both of the Peach Valley Formation (revised). Interfingers with the Violin Breccia to the southwest and with the Ridge Route undivided to the northeast. Lateral extent is 4310 m. Thickness is 740 m at the type section and ranges from 100 m to 1300 m. Age is late Miocene based on stratigraphic position. (B1565)

Source: GNU records (USGS DDS-6; Menlo GNULEX).