Interstitial Waters of Black Sea Cores

Abstract

Black Sea interstitial waters show three major features: (1) at Sites 379 and 380 a clear reflection of fresh-water lake stages is obtained. Data from Site 379 indicate that waters in the "Riss" fresh-water or regressive stage, as indicated by Zhuze and Mukhina (this volume), were even fresher than in the latest "Würm" regression and glacial maximum. In the former, chlorinitis of less than 2 °/oo were found, contrasting to about 3 °/oo for the "Würm." No fresh-water stage was found at Site 381, indicating truncation or nondeposition of sediments. (2) Beneath the fresh-water zones (Mindel zone, according to Zhuze and Mukhina, this volume) hypersaline episodes occur, reaching more than 100 °/oo salinity, but there are no permanent evaporitic sediments, such as gypsum. These zones exhibited high calcium and magnesium concentrations. The Black Sea in late Miocene time had waters of more standard marine character in the vicinity of Site 381, and no evaporites occur within middle to late Miocene sediments at this site or, by inference, the remainder of the Black Sea. (3) Many strong diagenetic features occur, including NH4 concentrations considerably exceeding those of K in pore fluids, absence of SO4, and reaction of both Mg and Na with calcium-bearing phases to form diagenetic minerals and liberate CaCh. Silica concentrations are high in diatom-rich zones and lower in clayey sediments, which lack amorphous silica in large quantity.