ALBERT

Description / Table of Contents: Abstract A geological expedition in 1968 into the Strait of Otranto yielded 26 undisturbed box cores, gravity cores, and some additional grab samples (fig. 1). The surface sediments of these samples were examined in order to establish a model of a Recent sedimentary facies of a strait connecting two seas. The recent pattern of the sediment distribution is markedly different from that of a former sedimentary facies which we found documented in deeper parts of the cores (fig. 2). (A detailed description of the sedimentary structures of the cores will be the topic of a forthcoming paper,Hesse, v.Rad &Fabricius in press.) The Strait of Otranto is about 70 km wide and the maximum sill depth is only 760 m. To the N the sea floor drops to 1260 m in the South Adriatic Basin. The Ionian side of the strait shows 4 main morphological structures influencing the sedimentation at least during the Early Holocene, less visibly today: 1. The Apulian shelf (the Greece-Albanian shelf had to be neglected because of political reasons) is covered by the coarsest sediments under consideration here. It is composed mainly of Recent terrigenous and sceletal material, mixed with Quaternary relict sediments; among these oölitic grains in northern areas and glauconite pellets more to the S are noteworthy. 2. The Slope is covered by pelagic mud, which is homogenized by bioturbation. Slumps of unknown dimensions probably occured during the last sea level rise. Their convoluted sediment was found on the foot of the slope (core OT 5, water depth 826 m), showing a sedimentary facies typical for a shelf environment deeper than 120 m and shallower than 180 m. 3. The “Corfu-Kephallinia- Trough”, forming the SE continuation of the sill, is also covered by Recent pelagic muds containing about 30% CaCO3 and about 0,4% organic carbon. During the Holocene one to two sand layers, partly graded, were deposited in the N part of the through. They had probably derived from the Apulian side. At about 9000 a. BP an interlude of a “varved” sedimentation began in the southern part of the trough and adjacent areas of 4. the “Apulian Ionian Ridge”. This sediment has an organic-carbon content about three times higher than normal, and is composed of coccoliths (fig. 3) intercalated with a facies rich of minerals. Burrows crossing the laminations indicate perhaps bionomic less favourable waters but not real “euxinic” conditions. In general a reducing environment causing the diagenetic formation of framboidal pyrite (fig. 4), is restricted to a sediment zone 2–10 cm below the oxydized surface. A study of the heavy minerals revealed the existence of glaucophane, a typical mineral of the N-Adriatic/Alpine area, indicating a transport of sediment by a current from the north southward along the Italian coast. The patterns of regional distribution of the biogenic content mainly depends on the water depth (fig. 6+7). It is possible, therefore to indicate the original depth of formation of a slumped sediment, e. g. station OT 5. The finding of reworked Quaternary oöids on the Apulian shelf is an important document for a warmer climate probably during Late Pleistocene or Early Holocene. From that time, oolitic sediments are only known from southern parts (Tunisian and Libyan coast) of the Ionian Sea.