Natural Resources Management and Environmental Sciences Department

Degree Name

BS in Earth Sciences




Scott Johnston


Middle Cretaceous movement along the Sur–Nacimiento Fault has implications for our understanding of how convergent tectonic margins evolve and for the architecture of forearc basins. Traditional explanations suggest an autochthonous California Mesozoic Forearc that underwent sinistral or thrust displacement; although recent research suggests either an allochthonous forearc or an isolated Nacimiento Block that experienced significant dextral displacement. Detrital zircons obtained from the Great Valley Group within the Nacimiento block provide age distribution patterns that can help identify sources of sediment deposition and therefore the past location of the Nacimiento block. Using U-Pb detrital zircon geochronology, we have discovered a dominance of miogeoclinal sources and a significant presence of Central American sources in our samples. This suggests that the Sur–Nacimiento Fault was either a sinistral or thrust fault that lead to autochthonous emplacement of the Nacimiento block or possibly a dextral strike-slip fault that brought the Nacimiento Block northward from Central America.