# Purisima Formation **Domain:** Geology / Paleontology / California Coast **Doc Type:** Canonical Formation Node **Maturity:** Developed ## Definition The **Purisima Formation** is a late Miocene-to-Pliocene marine sedimentary unit exposed along parts of the central California coast and around the San Francisco Peninsula. It preserves marine invertebrates and vertebrates including whales, pinnipeds, sharks and seabirds. ## Nexus Context In [[articles/The Evolutionary Roots of Silicon Valley|The Evolutionary Roots of Silicon Valley]], the formation establishes a changing shoreline beneath the modern technology corridor. Its fossils show that current geography is one temporary state in a much longer sequence. For the continuity architecture, the formation models stratified evidence: later layers do not erase earlier states, but access depends on preservation and exposure. This is a material analogue for [[wiki/Technical Archaeology|Technical Archaeology]], not proof that sedimentary succession preserves subjectivity. ## Sources / Provenance - U.S. Geological Survey, regional geologic mapping: https://www.usgs.gov/programs/national-cooperative-geologic-mapping-program - University of California Museum of Paleontology collections: https://ucmp.berkeley.edu/ ## See Also [[wiki/Fossil Record|Fossil Record]], [[wiki/Paleontology|Paleontology]], [[wiki/Franciscan Complex|Franciscan Complex]], [[wiki/Scalar Nesting|Scalar Nesting]]