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On the basis of lithology and sedimentary structure, a stratigraphic correlation of the three sites drilled during DSDP Leg 42B is attempted. Data reveal an almost continuous section from the upper Miocene to the present. The sediments can be grouped into an upper terrigenous and a lower chemical facies. The chemical facies covers the time interval: upper Miocene-Cromerian. The three major European glacial periods: Elsterian, Saalien, and Weichselian produce a massive terrigenous section up to 450 meters thick. During the Holsteinian, Eemian, and Holocene interglacials, brief marine invasions are indicated by a few meters of nannofossil ooze, sapropel, and micrite intercalations. The chemical facies formed under shallow water conditions first in a restricted marine, upper Miocene-Pliocene basin, and subsequently in an intermediately deep and fresh water-saline environment. During the Cromerian and extending towards the present, the Black Sea changed into the deep basin of today. Major unconformities recognized at the two western sites (380 and 381) at the contact of the terrigenous-chemical facies are a result of this tectonic development. BACKGROUND INFORMATION Stratigraphic correlations and estimates of geologic age in the Pleistocene in the Black Sea are difficult because the biogenic remains mainly indicate facies and not time intervals. In order to get such estimates, we have to rely on absolute age-dating techniques such as radiocarbon methods. Previous studies on piston cores have shown that three main sediment units were deposited during the past 25,000 years (Degens and Ross, 1974). The most recent (commonly called Unit 1) sediments are principally composed of the Coccolith, Emiliania huxleyi. The base of this upper marine unit has an assigned uC age of about 3000 years. Recent age dating using varve techniques, suggest that this C age may be in error by about 2000 years as a consequence of "dead" organic carbon contribution (Degens et al., this volume). The middle unit (Unit 2) is a dark sapropel deposited under brackish conditions. The radiocarbon age at the base of this unit is about 7000 years B.P. which may be too high by 2000 years as suggested by varve dating. Unit 3, deposited in a fresh water environment, was not completely penetrated by piston cores. The age at the base is about 22,000 years B.P. The stratigraphic interpretation of the Black Sea cores is still somewhat controversial. The careful reader should refer to other papers and the summary paper in this volume. These facies differences are clearly related to recent environmental changes. They are a result of Pleistocene sea-level fluctuations. In summary, rates of sedimentation are 30 cm/1000 years for the Coccolith unit (10 cm/1000 years if the initial C measurement is correct), 10 cm/1000 years for the sapropel, and about 1 m/1000 years for the terrigenous fresh water sediments. During Leg 42B of the D/V Glomar Challenger, three sites were occupied in the Black Sea (Figure 1). The background information of the sites is summarized in Table 1.

Stratigraphy and Suggested Ages of Black Sea Sediments Cored during Leg 42B