General Facts
Newhall sits atop many hundreds of feet of alluvium that was deposited by the tributaries of the Santa Clara River during the last few thousand years. The low hills surrounding the area are composed of rocks from the 1.7 to 2 million years old Plio-Pliestocene Saugus Formation. Those hills were uplifted during the latter part of the Coast Ranges Orogeny about 1.5 million years ago. This uplift has also helped to create the stream terraces which parts of Newhall are built on, such as the area east of Kansas St at Lyons Ave. They are remnants of the former valley floor that the streams have eroded.
To the south of the Newhall area, the mountains are composed of mostly marine Pliocene Pico Formation. This formation is heavily fossiliferous with many different types of sea shells and other fossils. Some of these fossils can easily be found along The Old Road near Weldon Summit as well as near the intersection of Calgrove Blvd and The Old Road. This formation was formed during a period when this region was a part of a shallow sea. It is also an oil rich rock formation producing oil since it was first discovered in the late 1800’s.
Rivers and Drainage
Newhall Creek is a tributary to the South Fork Santa Clara River which in turn is a tributary to the Santa Clara River. Newhall Creek enters the South Fork near the Wiley Canyon Road bridge. This photo shows the creek as it runs under the railroad tracks and San Fernando Road north of Lyons Avenue.
The creek is considered an intermittent stream because it doesn’t run the entire year along its entire course. There are two major drainage basins in this end of the valley. One is to the southwest (Wiley, Rice, East, Gavin, Towsley, Pico Canyons) and another to the southeast (Newhall, Whitney, Elsmere Canyons). Only the upper reaches of Newhall, Elsmere, and Towsley Canyons have water running within them most of the year.
Faults and Folds
There are numerous faults that run in the area. One in particular, the San Gabriel Fault, is an fairly inactive branch of the San Andreas Fault. The fault runs within two miles north of Newhall. There are also numerous folds in the area. The Pico Anticline is famous for its many oil wells, one, CSO #4, was the longest continuously operating oil well in the world. It ran for over 100 years!
The rock in that area, mostly Saugus Formation, is partly composed of volcanic clasts. There was some volcanic activity during the Oligocene epoch (approximately 24 mya) in the Acton area, the Vasquez Formation, which is the source of these volcanics.
I hiked Wildwood Canyon in Newhall recently. I found 3 agates. Does that mean there was volcanic activity in that general area?
Possibly many millions of years ago, it was probably deposited after a landslide or flood many years ago and had overtime been uncovered. I’ve found several agates as well!