An area of active fluid discharge characterized by authigenic barite format
ion and populated by vestimentiferan tubeworms has been discovered by remot
ely operated vehicle exploration in Monterey Canyon, Slumping and mass wast
ing, presumably triggered by seismic activity, have exposed barium-rich por
e fluids to sulfate-rich bottom water, leading to barite precipitation on t
he sea floor. Age estimates based on (210)pb/Ra-226 dating of the barite sa
mples and growth rates of vestimentiferan tubeworms indicate that the seep
site might be as young as 100 yr. Systematic variations in sulfur and stron
tium isotope ratios, the lack of visible fluid now, and the abundance of de
ad tubeworms indicate decreasing flow rates. This newly discovered site sho
ws many similarities to a previously described barite deposit in the Califo
rnia Borderland, possibly misinterpreted as a hydrothermal vent site, The d
iscovery of a cold seep associated with barite deposits on the seismically
active, transpressional California margin raises the possibility that numer
ous unexplored areas along the continental margins might have similar low-t
emperature deposits.