The Tassajara Formation is a geologic unit within the Livermore Valley of Northern California, United States. The formation surfaces only in the northern upland parts of the Livermore Valley and underlie the central part of the valley floor at a depth ranging from  to .
The Tassajara Formation is a geological entity found within the Livermore Valley of Northern California, United States. The formation's presence is restricted to the northern upland areas of the valley and covers the underlying terrain in the central part of the valley floor at varying depths.