40Ar/39Ar chronology of sea-level change before and during the interglacial maxima of Marine Isotope Stage 13

Marine Isotope Stage (MIS) 13 represents the most recent “lukewarm” interglacial within the sequence of glacial and interglacial periods that has characterized global climate over the past million years. It comprises two interglacial maxima (MIS 13.3 and MIS 13.1) and follows MIS 14.2, which is generally regarded as a weakly developed glacial period. New and existing data from the 40Ar/39Ar-dated aggradational successions of the Paleotiber drainage system provide precise constraints on the timing and nature of sea-level change before and during MIS 13. Gravel deposition and/or river incision allow identifying two sea-level lowstands, followed by glacial terminations VIb and VIa, which culminated at 533.7 ± 1.6 ka and 515.7 ± 1.3 ka and led to sea-level highstands of different magnitude and duration during interglacial maxima MIS 13.3 and MIS 13.1, respectively. MIS 13.1 featured higher sea level and lasted almost twice as long as MIS 13.3, reflecting an antiphase relationship between obliquity and precession that likely maintained warm northern high latitudes and sustained ice-sheet melting. A warmer and less glaciated Northern Hemisphere at the end of the MIS 13 interglacial supports the view that the transition from “lukewarm” to “super-interglacials” at the Mid-Brunhes Transition was preceded by a long-term shift toward warmer conditions and reduced residual continental ice in the Northern Hemisphere, reaching a maximum during MIS 13.