Remains of prehistoric human in strata deformed by the San Andreas fault near Stone Canyon, San Benito county, California

Human bones discovered in a river terrace about 20 m from an actively creeping trace of the San Andreas fault place an upper limit on the age of a sand deposit which has been deformed by fault-related movements. Amino-acid racemization infers these bones are about 5000 years old. No evidence was found associating this burial with cultural activity. The relationship between these bones and the surrounding soils, as well as the disarticulation and mixing of the bones, suggests that these human remains were buried by stream action. Sorted materials in this terrace dip 20° to the southwest, and other features of this exposure show that fault-related vertical displacements occur along this segment of the San Andreas fault. This style of deformation is consistent with dip-slip movement postulated by published results of dynamic modeling of creep-related strain events at the Stone Canyon Geophysical Observatory, only a few hundred meters from the burial, and with published models of tilt events recorded at Melondy Ranch, 6 km to the southeast. However, extrapolation of deformation rates based on these models and with the shortterm creep rate cannot be reconciled with deformation observed in the terrace. The bone fragments lie in the zone of complex deformation within the San Andreas fault zone. Holocene movements in this zone have occurred at least 20 m beyond the fault trace currently monitored for fault creep.