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In the succession of redox conditions encountered with increasing depth in sediments, the first major redox change is the oxic/post-oxic boundary. The geochemical behaviour of Hg is investigated in three different deep-sea situations where this boundary has been localised within a narrow depth zone for a sustained period (thousands of years) because of changes in sedimentary accumulation conditions. From previous work it is known that a variety of redox-sensitive elements form diagenetic peak concentrations above and below this boundary. This work shows for the first time that Hg also develops sharp peaks immediately into post-oxic conditions in two different situations where sediments containing trace pyrite have been re-oxidised. The Hg peaks are always closely associated with corresponding Se peaks, and the diagenetic concentrations of both elements are persistent over millions of years on subsequent burial into more reducing conditions. There is an apparent offset in the locations of Hg and Se peaks observed in a continuously accumulated case where Se uptake from bottom waters occurs independently of pyrite formation or re-oxidation, which may be a consequence of a widely spread Se peak. It is proposed that formation of the HgSe species tiemannite is involved, by analogy with selenium ore occurrences and the other elements found immobilised along with Se and Hg in the cases studied. Copyright © 1999 Elsevier Science Ltd

A boxcore taken from the top of a seamount south of Crete, on the outer (south) side of the Hellenic Trench, contains allochtonous coarse clastics, consisting mainly of rock fragments of alpine basement, brecciated Early/Middle Pliocene marls and reworked older Neogene sediments. This mixture of lithologies is interpreted as an Early/Middle Pliocene mass-flow deposit, which can be correlated with similar deposits from adjoining on- and offshore areas. The wide distribution of these sediments may be related to a period of increased tectonic activity which caused substantial vertical movements in the south Hellenic Arc. It is concluded that at the time of the formation of the mass-flow deposits this part of the Hellenic Trench had not yet evolved.

This paper summarizes micropaleontologic (foraminifera, calcareous nannoplankton, radiolaria, pteropods and pollen grains) and sedimentologic piston core data from the Eastern Mediterranean Tyro and Kretheus basins. 14 C datings indicate a Holocene age for the Tyro Basin cores. The latter show anoxic bottom conditions throughout, while the Kretheus Basin core indicates anoxic conditions prior to 3000 years ago and oxic conditions after that time. Resedimentation — through slumps, turbidity currents and from suspension — resulted in high sediment accumulation rates in both basins. Reworking in the Tyro Basin predominantly originated from the basin flanks, while the presence of common to abundant metamorphic clastics in the Kretheus Basin points to a more distant source. The Minoan eruption of Santorini (ca.3350 yrs B.P.) which is supposed to have caused a gigantic tsunami, is linked to the presence of turbidites and a thick homogenite in the Tyro Basin. The same event may be responsible for the initiation of oxic conditions in the Kretheus Basin.

Paleoclimate changes are reconstructed from Late Miocene-earliest Pleistocene deep-water sediments of the Solo River section, using fluctuations in planktonic foraminiferal faunas, water depth and clastic influx. Intervals with common cold-water planktonics (Globigerina bulloides, Neogloboquadrina cf. pachyderma) are thought to reflect periods of increased upwelling, triggered by Antarctic glaciations. Correlations with well Bodjonegoro-1 (Java), DSDP Site 62-1 and Lamont Core RC 12–66 (Equatorial Pacific) using planktonic foraminiferal datum levels and paleoclimate trends suggest non-synchroneity of several commonly used datums, probably due to differences in species concepts. It also allowed dating of the climate changes with regard to the magnetostratigraphic and numerical time scales. For correlations between different faunal provinces global climate changes are an extremely useful tool, probably superior to any single faunal datum. Using this, with other evidence, the following correlations could be obtained between the five “climatostratigraphic” zones in the Solo River section and the Mediterranean and New Zealand stages (from bottom to top): 1. Zone I, samples SR 63–SR 53, cool, older than 6.0 m.y. – ±5.8 m.y., magnetostratigraphic Epoch 6 (and older?) — basal Epoch 5, planktonic zone (Upper N16?-) N17, Mediterranean stages (upper?) Tortonian—Early Messinian, New Zealand Stages Tongaporutuan—Early Kapitean, Late Miocene. 2. Zone II, SR 52–SR 35, moderately warm with fluctuations, ± 5.8 m.y.–5.0 m.y., Epoch—lowermost Gilbert, upper N17 (−N18?), Late Messinian (evaporite phase), Late Kapitean, Late Miocene. 3. Zone III, SR 34–SR 33, cool, 5.0–4.8 m.y., within Lower Gilbert, (N18?-) basal N19, latest Messinian (“Lago Mare” phase), latest Kapitean or earliest Opoitian, latest Miocene. 4. Zone IV, SR32–SR 18, warm to very warm, 4.8–±2.7 m.y., within Lower Gilbert — within Upperg Gauss, N19 within N21, Zanclean-Piacenzian, Opoitian Pliocene. 5. Zone V, SR17–SR 12, cool, ±2.7 m.y.—age of top unknown, Upper Gauss-Lower Matuyama, within N21 (−N22?), Santernian or basal Calabrian s.l., Waipipian, basal Pleistocene (Late Pliocene of workers with different Pliocene-Pleistocene boundary concepts).