Other important lithologies include chert, basalt, limestone, serpentinite, and high-pressure, low-temperature metabasites (blueschists and eclogites) and meta-limestones.

[3] The Franciscan Complex is an assemblage of metamorphosed and deformed rocks, associated with east-dipping subduction zone at the western coast of North America.

[9] Franciscan rocks are thought to have formed prior to the creation of the San Andreas Fault when an ancient deep-sea trench existed along the California continental margin.

[10] This resulted in widespread deformation with the generation of thrust faults and folding, and caused high pressure-low temperature regional metamorphism.

[10] In the Miocene, the Farallon-Pacific spreading center reached the Franciscan trench and the relative motion between Pacific-North America caused the initiation of the San Andreas Fault.

[11] The units of the Franciscan complex are aligned parallel to the active margin between the North American and Pacific plates.

[12] The Franciscan Complex is in contact with the Great Valley Sequence, which was deposited on the Coast Range Ophiolite, along its eastern side.

[13][14] The type area of Franciscan rocks in San Francisco consists of metagraywackes, gray claystone and shale, thin bedded ribbon chert with abundant radiolarians, altered submarine pillow basalts (greenstone) and blueschists.

[20] Vertebrate fossils in the Franciscan are extremely rare, but include three Mesozoic marine reptiles that are shown in the table below.