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 .
In the Livermore Valley of Northern California, there is a geological unit known as the Tassajara Formation. This formation only appears in the northern hills of the valley and lies beneath the central portion of the valley's floor, spanning depths between  and .