In normal to wet rain seasons vernal pools can be found throughout the Simi Hills. The pool pictured above is near the sheep corral at China Flat, and another small pond was found nearby, along Albertson Motorway fire road. I’ve also found vernal pools in the Rocky Peak area and near Sage Ranch.
Geologically, the Simi Hills are characterized by the sandstone rocks of the Chatsworth formation. These inclined layers are of varying hardness, and erode at different rates. It’s my guess that water collects in sandy soils between, or at the base of, the more resistant layers.
The photographs of the ponds at China Flat are from Sunday’s Scenic Route to Simi Peak run.