Lyon Canyon Geology
The above geologic map (from the Geologic Map of the Oat Mountain and North 1/2 Canoga Park Quadrangles by Thomas Dibblee, DF-36, 1992) shows Lyon Canyon cutting through the Saugus Formation (in the upper right), the Pico Formation, the Towsley Formation, and the Modelo Formation (in the lower left). Towsley Canyon is on the south (below map) and Dewitt Canyon is on the west (left). Pico Canyon is just north of the map. Dibblee maps are great for getting a general idea of the geology of an area, but on this map I disagree with the Pico-Saugus contact location.
The Qa on the map designates recent river, valley, and floodplain deposits.
The Pleistocene/late Pliocene Saugus Formation (Tsr on map - tan color) are mostly terrestrial alluvial fan deposits containing claystone, mudstone, sandstone, and conglomerate. Land animal fossils have been found in the Saugus Formation, but not in Lyon Canyon.
The Pico Formation (Tp, Tps on map - yellow color) are shallow marine deposits containing sandstone, conglomerate, siltstone and claystone. Fossils are common and appear to be at the same level as those found in the Pico Formation around the mouth of Towsley Canyon (see Squires, Groves, Smith, 2006).
The marine Towsley Formation (Ttos, Ttoc on map - greenish color) is early Pliocene and also contains sandstone, conglomerate, siltstone, and mudstone. No fossils have been found in the Towsley Formation in Lyon Canyon.
The late Miocene marine Modelo Formation (tan color) follows the axis of the Pico Anticline and is found deep in the canyon. It consists of mostly of shale.
Lyon Canyon is mainly on the northern flank of the Pico Anticline. The colors of the map make it easy to see the anticline structure with the rocks getting older as the center, or axis, of the anticline is approached.
For a few miles Lyon Canyon parallels the north flank of the Pico Anticline. It's easy to see the anticline in this west view.
Another view to the west
Closer view looking east
Pico Formation fossil clam
Pico Formation fossil bivalve