This map consists of four different Dibblee Geological Foundation maps with Placerita Canyon pasted together. They are Geologic Map of the Newhall Quadrangle #DF-56 (1996), Geologic Map of the Mint Canyon Quadrangle #DF-57 (1996), Geologic Map of the Oat Mountain and North 1/2 Canoga Park quadrangles #DF-36 (1992), and the Geologic Map of the San Fernando and Van Nuys (North 1/2) Quadrangles #DF-33 (1991).

According to this map, the roadcuts on the drive up Placerta Canyon Road to the Nature Center and up to about Los Pinetos Canyon consist almost entirely of Saugus Formation, so I will include more information on them below.

Dibblee geologic maps can be purchased online here.

Legend (quoted from maps):

Qa, Qg, Qoa, Qos, Qog: Surficial sediments - unconsolidated alluvial deposits, Quaternary

Qls: Landslide debris, Quaternary

QTs, Ts, Tsr: Saugus Formation - mostly terrestrial, weakly consolidated, Pleistocene and Pliocene age
QTs: light gray to light reddish brown pebble-cobble conglomerate, sandstone and minor siltstone; conglomerate composed of granitic, gneissic, metavolcanic, quartzitic, gabbroic and anothositic detritus in friable sandy matrix, bedded; deposited by westward flowing streams; probably mostly of Pleistocente age.

Ts (south of San Gabriel fault): same as QTs, but contains much fine grained, light reddish-gray sandy siltstone; probably of Pliocene age.

Tsr: Sunshine Ranch Member; light reddish to greenish claystone and sandstone and interbedded pebble-cobble conglomerate similar to that of QTs.
Ttoc, Ttos, Ttog: Towsley Formation - shallow marine regressive, lastest Miocene and/or early Pliocene age

Tc, Tcal: Castaic Formation (north of San Gabriel fault) - marine clastic and biogenic, late Miocene

Tmc, Tmcl, Tmg: Mint Canyon Formation (north of San Gabriel fault) - nonmarine clastic, middle to late Miocene

gr: Granitic rocks, late Mesozoic (Cretaceous) age

qd: Quartz diorite, late Mesozoic (early Cretaceous?)

gn: Gneissic rocks, Cretaceous age or older