Geology of the Santa Clarita Valley – Saugus

Geology of Saugus

General Facts

Most of Saugus rest upon the 1.8 million year old Plio-Pliestocene Saugus Formation. The upper reaches of Saugus, in Bouquet Canyon, rest on 23 to 26 million year old Miocene Mint Canyon Formation. This boundary line between the Saugus and Mint Canyon formations is near the city limits in Bouquet Canyon and near Dry Canyon Reservoir in Seco Canyon. The Saugus Formation was deposited during a time of great uplift in the region. Later uplift after the deposition of the Saugus beds caused the strata to be tilted.  The canyon floors are composed of Recent alluvium from streams.

Some areas of Saugus are quite unstable. Much of the Plum Canyon area is within a major landslide complex that still is apparent today. Vasquez Canyon, northeast of Saugus, is another area of high instability. Both of those areas are located within the Mint Canyon Formation. It was known as the “Land of Moving Earth” by the local Native Americans. In the case of the Vasquez Canyon area, the geology is seemingly set up for landslides. The strata dips down slope, it is composed of interbedded silts and sandstones, and there is also an expansive clay contained within the beds. All these factors combine to create an area where landslides are likely. Vasquez Canyon Road tends to get quite bumpy in areas due to these slides and clays. The photos below depict some of the landslides in the canyon.

Overview of Vasquez Canyon. These hills are composed of the Mint Canyon Formation. Saugus is visible as a green area in the middle right background.
Overview of Vasquez Canyon. These hills are composed of the Mint Canyon Formation. Saugus is visible as a green area in the middle right background.
View of one of the slides in the canyon. The slide is the horseshoe shaped area in the middle of the photo. The cliffs in the background mark the edge of the Cruzan Mesa.
View of one of the slides in the canyon. The slide is the horseshoe shaped area in the middle of the photo. The cliffs in the background mark the edge of the Cruzan Mesa.
Outcropping of Oligocene Vasquez Formation in San Francisquito Canyon near the St Francis Dam site.
Outcropping of Oligocene Vasquez Formation in San Francisquito Canyon near the St Francis Dam site.

Adjacent to the canyon is the Cruzan Mesa, known in earlier years as Mystery Mesa and Puckett Mesa. This mesa is an erosional remnant of the ancient Santa Clarita Valley. The surrounding rock has been eroded away as the surrounding streams have dissected the older valley floor, leaving this remnant high above the area. Few other traces remain of the pre-Pleistocene Santa Clarita Valley. Similar mesas and terraces exist between Bouquet Canyon and Soledad Canyon, west of Whites Canyon Road and east of Bouquet Junction.

Rivers and Drainage

Both Bouquet Creek and San Francisquito Creek are major tributaries to the Santa Clara River. They both are also some of the few perennial creeks in the area. From the city limits to Bouquet Reservoir, Bouquet Creek is uncontrolled. It has no levees nor any concrete bottoms which can create a problem during flood season. These types of streams should not be fully concrete lined but development surrounding the floodplain should be built away from the flood prone areas.

Faults and Folds

Only a few major folds exist in this area. None are very large. Faults are also not common with one exception. The San Gabriel Fault runs very close to here. Its closest approach to Saugus is near Bouquet Junction.

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