First cross-matched floating chronology from the marine fossil record:: data from growth lines of the long-lived bivalve mollusc Arctica islandica

Integrated understanding of phasings within the climate system over the last glacial cycle, and at higher frequencies, is inhibited because no absolute timescale for the marine environment currently exists. This precludes identification of forcings and feedbacks, accurate temporal calibration of the marine radiocarbon reservoir effect, and the application of radiocarbon as a proxy of short-timescale ocean ventilation. This has prompted a search for annually banded marine proxies in the hope of establishing an accurate marine chronometer. We present annual growth band series from dead-collected specimens of the ong-lived bivalve mollusc Arctica islandica from the northern North Sea and demonstrate their successful cross-matching, with the general timescale context independently verified by radiocarbon dating. Though at present limited to only a few statistically cross-matched series, this has already generated the longest Arctica chronology, and the first 'floating' chronology constructed entirely from marine fossils. The record covers the period from C. AD 1000 to 1400 and integrates a 267-yr series from the longest-lived Arctica specimen yet recorded from the North Sea. This breakthrough in cross-matching demonstrates that Arctica islandica can fulfill its potential as the 'tree of the sea' to provide an absolute timescale for the marine environment.