18 31 dating
Moreover, the ages obtained for this study give us the opportunity to compare the timing of the sea-level fluctuations inferred from the stratigraphic record and that provided by the astrochronologic calibration of the Oxygen isotopic curves, and to assess the calibrations of Assessing ages of sedimentary successions deposited in near-coastal environments in response to sea-level fluctuations is a straightforward mean to investigate the timing of glacio-eustatic cycles and provide insights on their forcing mechanisms.In this light, the coastal plain of the Tiber River near Rome (Fig.Supplementary Figure 1 shows the Zr/Y vs Nb/Y composition of the analysed samples of volcanic deposit and their correlation with known eruptive units.(a) Cross-section showing the stratigraphic relationships among the VGF and the previous (Santa Cecilia Formation -SC, MIS 15 (ref.3)) and the following (San Paolo Formation -SP, MIS 11 (ref.Moreover, at two locations within the Tiber valley incision (Via Flaminia, Fig. 2a) the TP rests directly above a thick gravel layer which constitutes the basal, coarse portion of the VGF aggradational succession in Rome.Stratigraphic evidence at Viale Tiziano and at Capitoline Hill (Fig.By doing so, we provide quantitative constraints, both in amplitude and duration, to the sea-level fluctuations during MIS 13.Ar ages performed for this study and those from literature used to constrain aggradation of the VGF are reported in Table 1.
C age constraints on the aggradational succession of the modern Tiber River, (refs 8 and 9) have shown that the accumulation of a several meters-thick basal gravel layer within the Tiber valley occurred since 15.1 ± 0.1 ka, and that the abrupt sedimentologic transition to a several tens of meters-thick sandy clay package of sediments occurred synchronously in a 30 km-long terminal tract of the river channel, between 13.6 ± 0.2 and 12.8 ± 0.1 ka.The new geochronologic constraints suggest a long duration for the period of sea-level rise (533 ± 2 through 498 ± 2 ka) encompassing two consecutive positive peaks of the δO curve (substages 13.3 and 13.1).Consistently, the litho-stratigraphic features of the sedimentary record account for two aggradational phases separated by an intervening erosional phase.To accomplish this, we employed a method relying on the ratio of immobile elements (i.e.Zr/Y vs Nb/Y)By using ages of four selected tephras interbedded within the aggradational succession, we provide independent time constraints with analytical uncertainties on the order of ±2 ka (2σ) on the associated sea-level fluctuations during MIS 13 and on glacial termination VI.