Independent ⁴⁰Ar/³⁹Ar and ¹⁴C age constraints on the last five glacial terminations from the aggradational successions of the Tiber River, Rome (Italy)
Date
2016
Authors
Marra, F.
Rohling, E.J.
Florindo, F.
Jicha, B.
Nomade, S.
Pereira, A.
Renne, P.R.
Journal Title
Journal ISSN
Volume Title
Publisher
Elsevier
Abstract
We use 13 new ⁴⁰Ar/³⁹Ar and 4 new 14C datings of volcanic deposits and organic material found within near-coastal aggradational successions deposited by the Tiber River near Rome, Italy, to integrate a larger dataset previously achieved in order to offer independent age constraints to the sea-level fluctuations associated with Late Quaternary glacial cycles during the last 450 ka. Results are compared with the chronologically independently constrained Red Sea relative sea-level curve, and with the astronomically tuned deep-sea benthic δ¹⁸O record. We find good agreements for the timings of change, and in several cases for both the amplitudes and timings of change during glacial terminations T-1, T-2, T-3, and T-5. There is one striking exception, namely for glacial termination T-4 that led into interglacial Marine Isotope Stage (MIS) 9. T-4 in our results is dated a full 18 ka earlier than in the Red Sea and deep-sea benthic δ¹⁸O records (which are in good agreement with each other in spite of their independent chronological constraints). The observed discrepancy is beyond the scale of the combined age uncertainties. One possible explanation is that the documented aggradation represents an early phase, triggered by a smaller event in the sea-level record, but the thickness of the aggradational sediment sequence then suggests that the amplitude of this earlier sea-level rise is underestimated in the Red Sea and benthic δ¹⁸O records. Also, this would imply that the aggradational succession of the main T-4 deglaciation has not yet been located in the study region, which is hard to reconcile with our extensive fieldwork and borehole coverage, unless unlikely non-deposition or complete erosion. Resolving this discrepancy will improve understanding of the timing of deglaciations relative to the orbitally modulated insolation forcing of climate and will require further focused research, both into the nature and chronology of the Tiber sequences of this period, and into the chronologies of the Red Sea and deep-sea benthic δ¹⁸O records.
Description
Keywords
aggradational succession, glac ial termination, glacio-eustatic forcing, Tiber River, ⁴⁰Ar/³⁹Ar dating
Citation
Collections
Source
Earth and Planetary Science Letters
Type
Journal article