Agua Dulce is located in the Sierra Pelona Valley, between Santa Clarita and Acton. The valley floor is mostly composed of an early Quaternary alluvium. It is one of the last remnants of a depositional surface which covered much of this region. The valley floor here is currently being eroded by the tributaries of Agua Dulce Creek, which flows to the south to the Santa Clara River. Many houses along Agua Dulce Canyon Road are built on top of this well-drained surface. This type of erosion is called headward erosion.
The rock underlying this valley floor is mostly Oligocene Vasquez Formation. The Sierra Pelona Mountains to the north are made of Precambrian Pelona Schist. These mountains are a part of the Transverse Ranges as they generally run west to east. Vasquez Rocks are also composed of the Vasquez Formation and the shape is due to differential erosion of parts of the formation.
In nearby Tick Canyon, a borax mine flourished from 1906 to about 1920. The remains can still be seen along Davenport Road about half way between Sierra Highway and Agua Dulce Canyon Road. Many minerals can be found there including howlite, colemanite, ulexite, and many others. A great website has been produced covering the mineralogy of the locality in much greater detail by the Mineralogical Society of Southern California.
Rivers and Drainage
Most streams in this area drain southerly into the Santa Clara River via Agua Dulce Canyon. These streams are eroding headward into the Sierra Pelona Valley floor creating a terraced appearance. There is a smaller drainage divide to the northwest that separates the Mint Canyon drainage from Agua Dulce Canyon. Mint Canyon, heading westerly, also drains into the Santa Clara River near Solemint in Santa Clarita.
Faults and Folds
The Elkhorn Fault, one of the faults in the area, runs in a generally east-west line near Escondido Canyon Road. The signs of folding are shown in road cuts and at Vasquez Rocks. They are steeply dipping away from the axis of a large anticline. This faulting is also responsible for the marshy area near Agua Dulce Canyon Road and Escondido Canyon Road.