Interstitial water studies on small core samples, Leg 22

Abstract

Interstitial waters from Leg 22 in the Indian Ocean revealed two unique results: Site 214, on the Ninetyeast Ridge, penetrated through a 30-meter sequence of fine-grained basalt and reentered hard, silty clay containing carbonate skeletal debris. Such a basalt layer may well have been impervious and extensive enough to seal off underlying (fossil) seawater of Paleocene age. However, except for a marked increase in calcium and a slight increase in chloride, no appreciable changes in pore fluid chemistry could be confirmed. Site 217, at the northernmost end of the Ninetyeast Ridge, demonstrated record concentrations of interstitial calcium in clayey nannofossil oozes and a relatively small but significant increment in chloride with depth. Presumably, these increments signal the existence of evaporitic sediments or evaporite-influenced brines at considerably greater depth than penetrated.