The chemistry of interstitial waters at DSDP Site 45-395@en

Chemical analysis of fluids sampled in situ during Leg 78B has been carried out. The fluids found in Hole 395A upon reoccupation of the site after a five-year hiatus were identical in composition to local bottom seawater to depths of at least 400 meters, suggesting drawdown. No local bottom-water component is present at 543 meters however. The chemistry of this deep sample shows a large depletion in magnesium, with charge balance maintained by sodium, rather than calcium, enrichment. Calcium is lost through calcite precipitation. A sediment interstitial-water sample from the offset Hole 395B has a chemical signature indicative of glacial influence, thereby constraining drawdown through the sediments to a velocity less than 0.5 cm/y.