CLAMS AS RECORDERS OF OCEAN RIDGE VOLCANISM AND HYDROTHERMAL VENT FIELD ACTIVITY

The clam Calyptogena magnifica lives at abyssal depths in association with hydrothermal venting on midocean ridges. Analysis of strontium/ca lcium ratios in C. magnifica shells provides a temperature proxy with submonthly time resolution. A 21-year strontium/calcium record of two clams from 9 degrees 50'N on the East Pacific Rise captures the known 1991 and 1992 eruptive events, documents several additional events bet ween 1992 and 1996, and demonstrates the absence of major hydrothermal episodes during the period 1974 to 1991. These clam archives can incr ease our understanding of the thermal and chemical history of midocean ridge hydrothermal and volcanic activity on decadal time scales.