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 thirty tephra layers whose age, based on physical and biostratigraphic data, encompass a time interval ranging from less than 70 ka to the Present. Chemical features of the tephra, defined by SEM-EDS analyses performed on glass shards, indicate alkaline affinity, mainly with K/Na > 1, and trachytic compositions with two minor benmoreitic and phonolitic groups. These characteristics are consistent with Campanian and subordinate Etnean provenances. Because of chemical and age constraints the glass shards can be referred to six tephra layers already described in the literature, such as C20, C14 (Citara/Ischia), C10 (Campanian Ignimbrite), C2/NYT (Neapolitan Yellow Tuff), AMS/PF (Agnano Monte Spina/Phlegrean Fields) from Campanian area, and Y1 from Etna volcano, indicating an age ranging from about 70 to 4 ka. AMS/PF and C2/NYT, dated 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 sequences up to now, represents a very good marker for Holocene Adriatic sediments; C2/NYT already recorded in the central Tyrrhenian Sea, in lacustrine sediments from southern Italy and in the Campanian area, is 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 the central Mediterranean region. (C) 1998 Elsevier Science B.V. All rights reserved.