QUATERNARY DISTAL TEPHRA LAYERS IN ITALY AND THE ADJOINING SEAS: CURRENT KNOWLEDGE AND PROSPECTS FOR FUTURE RESEARCH

Abstract

Tephrochronological studies on Quaternary sedimentary successions of the Central Mediterranean area are reviewed and critically evaluated, with emphasis on the use of distal ash layers for land-sea correlations. The longest tephra records are provided by the deep-sea sediments from the basins adjoining Italy, which have been extensively studied in the last 30 years. Shorter (<100 ka), yet still significant records of ash layers have been recovered in lacustrine basins of the Italian Peninsula. The longest successions show that the tephra layers increase toward the top of the Quaternary record. The dominant Pliocene and lower Pleistocene tephra sources were
likely represented by the volcanoes of the Pontine Islands and the Aeolian arc, while in the middle-upper Pleistocene and Holocene
times Aeolian and Campanian products have been predominant. Tephra correlation is made difficult by the fact that the volcaniclastic
products are extensively reworked by epiclastic processes, even in the marine setting. Inconsistent analytical approaches used in the
old and recent work (bulk sample versus grain-discrete analysis) hinder integration of the available evidence. The regional tephrostratigraphy of early and middle Pleistocene ages is not established yet, because data are scarce and fragmentary and ages of tephra are poorly defined. Tephra correlation is frequent in the late Quaternary time span, in which several widespread marker-tephras have been identified. Recent findings extend the known distribution of the main late Pleistocene markers and suggest complex dispersal patterns, including deposition towards north and northeast. Occurrence of Quaternary tephra layers of probable Italian origin in sites of Central and Eastern Europe opens the prospect for precise correlation of sedimentary records across the European continent. Finally, reliable linking of chemical spikes in North Polar records to Italian explosive eruptions could be critical for a better understanding of palaeoenvironmental issues.