Age modelling of late Quaternary marine sequences in the Adriatic: Towards improved precision and accuracy using volcanic event stratigraphy

• DOI: 10.1016/j.csr.2005.12.017
• Publication Date: 2007-01-13T17:13:38Z
• Authors: J.J. Lowe; S. Blockley; F. Trincardi; A. Asioli; A. Cattaneo; I.P. Matthews; M. Pollard; S. Wulf
• Keywords: 550; Faculty of Science\Geography; Lago Monticchio record; Radiocarbon-based age models; CLIMATE CHANGES; radiocarbon-based age models; LATE-GLACIAL SEQUENCE; Volcanic event stratigraphy; 550 - Earth sciences; WDS geochemical data; Bayesian method; 01 natural sciences; 333; GRANDE-DI-MONTICCHIO; Discriminant function analysis (DFA); Lago Monticchio record;; ENVIRONMENTAL RECORD; 14. Life underwater; discriminant function analysis (DFA); tephrochronology; 0105 earth and related environmental sciences; EARLY HOLOCENE; BAYESIAN-APPROACH; Radiocarbon-based age models;; Tephrochronology;; MEDITERRANEAN SEA; NORTHERN-HEMISPHERE; Volcanic event stratigraphy;; Research Groups and Centres\Geography\Centre for Quaternary Research; 13. Climate action; volcanic event stratigraphy; RADIOCARBON RESERVOIR AGES; Tephrochronology; LAST DEGLACIATION

The first part of this paper presents a review of the problems that constrain the reliability of radiocarbon-based age models with particular focus on those used to underpin marine records. The reasons why radiocarbon data-sets need to be much more comprehensive than has been the norm hitherto, and why age models should be based on calibrated data only, are outlined. The complexity of the probability structure of calibrated radiocarbon data and the advantages of a Bayesian statistical approach for constructing calibrated age models are illustrated. The second part of the paper tests the potential for reducing the uncertainties that constrain radiocarbon-based age models using tephrostratigraphy. Fine (distal) ash layers of Holocene age preserved in Adriatic prodelta sediments are analysed geochemically and compared to tephras preserved in the Lago Grande di Monticchio site in southern Italy. The Monticchio tephras have been dated both by radiocarbon and varve chronology. The importance of basing such comparisons on standardised geochemical and robust statistical procedures is stressed. In this instance, both the Adriatic and Monticchio geochemical measurements are based on wavelength dispersive spectrometry, while discriminant function analysis is employed for statistical comparisons. Using this approach, the ages of some of the Adriatic marine ash layers could be estimated in Monticchio varve years, circumventing some of the uncertainty of radiocarbon-based age models introduced by marine reservoir effects. Fine (distal) ash layers are more widespread and better preserved in Mediterranean marine sequences than realised hitherto and may offer much wider potential for refining the dating and correlation of Mediterranean marine sequences as well as marine-land correlations.