TEPHRA LAYERS IN LATE QUATERNARY SEDIMENTS OF THE CENTRAL ADRIATIC SEA

Magnetic susceptibility curves of ten cores, collected in the western Adriatic shelf and in the Mid-Adriatic Deep, allowed us to recognize t hirty tephra layers whose age, based on physical and biostratigraphic data, encompass a time interval ranging from less than 70 ka to the Pr esent. Chemical features of the tephra, defined by SEM-EDS analyses pe rformed on glass shards, indicate alkaline affinity, mainly with K/Na > 1, and trachytic compositions with two minor benmoreitic and phonoli tic groups. These characteristics are consistent with Campanian and su bordinate Etnean provenances. Because of chemical and age constraints the glass shards can be referred to six tephra layers already describe d in the literature, such as C20, C14 (Citara/Ischia), C10 (Campanian Ignimbrite), C2/NYT (Neapolitan Yellow Tuff), AMS/PF (Agnano Monte Spi na/Phlegrean Fields) from Campanian area, and Y1 from Etna volcano, in dicating an age ranging from about 70 to 4 ka. AMS/PF and C2/NYT, date d 4.4 and 12.3 ka respectively, are the most widespread tephra beds in the study cores. The occurrence of AMS/PF, never recorded in marine s equences up to now, represents a very good marker for Holocene Adriati c sediments; C2/NYT already recorded in the central Tyrrhenian Sea, in lacustrine sediments from southern Italy and in the Campanian area, i s a good stratigraphic marker for inter-sea and sea-land correlations. Y1 tephra, dated 14.2 ka, also occurs in on-land sediments of central Italy and in marine sediments from the Tyrrhenian and Ionian seas: it now represents one of the most widespread stratigraphic markers in th e central Mediterranean region. (C) 1998 Elsevier Science B.V. All rig hts reserved.