Abstract

Volcanic horizons interbedded with fluviodeltaic clastic sediments of the Tiber and Fosso Galeria River valleys near Rome provide a unique opportunity to date five middle Pleistocene fining-upward aggradational sections. 40Ar/39Ar ages from the interbedded volcanic beds illustrate that aggradation occurred on an approximate 100 k.y. cycle and was initiated by sea-level rise associated with glacial melting. The age constraint additionally shows that aggradation occurs rapidly in response to sea-level change, and thus ages from volcanic strata within the aggradational sections provide high-resolution constraint on the timing of relative sea-level rise. The established chronology is consistent with other glacial proxies and their (radioisotopically or orbitally based) time scales for the timing of glacial terminations VI and V, but is significantly older than most records for the timing of termination III. Ultimately, the age of each termination should be determined by radioisotopic means, and to that end the work here shows that fluviodeltaic sedimentology provides valuable information for middle Pleistocene time-scale calibration.

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