During Leg 42A of the Deep Sea Drilling Project, we recovered over 150 discrete layers of dark colored organic-rich sediment at five sites in the eastern Mediterranean. We consider about twothirds of these to be sapropels, on the basis of a definition that recognizes a sapropel as "a discrete layer, greater than 1 cm in thickness, set in open marine pelagic sediment and containing greater than 2.0% organic carbon."This paper includes a catalogue of all the sapropels and sapropelic layers recovered, including analysis of their sedimentary structures, general composition, fossil content, and stratigraphic position.Sapropels are identified, dating back to the middle Miocene, and a single occurrence is recorded in the Pleistocene of the western Mediterranean. We recognize that the record of sapropel stratigraphy provided by Leg 42A and Leg 13 drilling is incomplete in both time and space. Despite this, we can make tentative basin-wide correlations between individual layers at least back to the early Pliocene, proving that these stagnation events cannot merely be linked to glacial phenomena. Their widespread distribution and the wide range of depths argue against the presence of an "oxygen-minimum layer."Stagnation of the Mediterranean basins resulted from a number of interacting factors which caused stratification within the water column. This was a transient situation that developed repeatedly since the mid-Miocene when the Mediterranean took on it present configuration. Glacial expansions were primary factors bringing about stratification in the Pleistocene; whereas, similar factors are as yet unidentified in the Pliocene and Miocene sediments.

We made oxygen and carbon isotopic determinations in monospecific samples of benthic foraminifers from over 200 samples from the upper 500 meters of DSDP Site 397. From these measurements, we constructed a history of isotopic variations through the past 7 m.y. (middle-late Miocene to Holocene) with a sampling resolution of better than 20,000 years over much of the interval.The frequency of climatic oscillations during most of this time was similar to that of the Pleistocene (i.e., more than 10 cycles/ m.y.). More constant conditions prevailed between 6 and 5.5 m.y. B.P., and between 4 and 3 m.y.B.P. During both these intervals, oxygen isotopic values are more negative than today; Atlantic Ocean deep waters were probably up to two degrees warmer than they are today.During the last 3 m.y. (late Pliocene to present), the temperature of Atlantic Ocean deep waters has remained rather constant, and the oxygen isotopic record reflects oscillations in the volume of the earth's major ice sheets. Prior to the late Pliocene, we are unable at present to distinguish with certainty between the effect of changes in the size of the Antarctic ice sheet, and changes in the temperature of deep waters, although the fact that the few data available from deep Pacific sites show smaller fluctuations suggests that temperature variations may have been the more important variable.

The late Neogene succession continuously cored at Hole 397 has been investigated in detail from Cores 69 to 19 to calibrate datum planes based on calcareous nannofossils and planktonic foraminifers with the sequence of magnetic reversals detected in the cores. Nine datum planes based on calcareous nannofossils, 7 based on planktonic foraminifers, and 15 magnetic reversals were detected from Section 57-3 to Core 19. The interval spans 5 m.y., and encompasses paleomagnetic Epoch 7 (partim) to the Matuyama Epoch (partim). Correlations are presented for the Bou Regreg section of northwestern Morocco; the Melilla section of northern Morocco; Rio Mazzapiedi section of northern Italy (Tortonian stratotype); Cape Rossello, Sicily (Zanclean stratotype); and DSDP Site 132 (Tyrrhenian Basin). The Tortonian/Messinian, Messinian/Zanclean, and Zanclean/ Piacenzian boundaries are biostratigraphically recognized and located with accuracy. Taxa ^^\T otal Abundance Amaurolithus amplificus Amaurolithus delicatus Amaurolithus primus Amaurolithus tricorniculatus Ceratolithus acutus Ceratolithus rugosus Ceratolithus telesmus Cyclococcolithus leptoporus Cyclococcolithus macintyrei Discoaster asymmetricus Discoaster bellus Discoaster berggrenii Discoaster bollii Discoaster brouweri Discoaster calcaris Discoaster challengeri Discoaster decorus Discoaster hamatus Discoaster icarus Discoaster intercalaris Discoaster loeblichii Discoaster neohamatus Discoaster neorectus Discoaster pentaradiatus Discoaster pseudovariabilis Discoaster quinqueramus Discoaster surculus Discoaster tamalis Discoaster variabilis s.i.

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