Description: We present ten 40Ar/39Ar age determinations, both on primary volcanic deposits and on detrital sanidine, which provide geochronologic control on the MIS 5.5 and MIS 5.3 sea-level indicators that occur at three coastal caves in the central Tyrrhenian Sea of Italy. Samples dated for the present work are as follows: - Two pumice clasts (MOSC-22, MOSC-37) extracted from the sand layers constituting the sedimentary fill of Moscerini Cave, recovered during the original archaeological excavations performed in the year 1949, stored at the IIPU (Istituto Italiano di Paleontolgia Umana) repository in Anagni (Frosinone, italy). These two samples were processed at the rare Gas Laboratory of the University of Wisconsin Madison in March, 2019. - One tephra layer (sample GDC-10) intercalated in the sedimentary fill of Capre Cave collected in June, 2021. - Seven sedimentary sand samples collected at Guattari Cave (GU-1, GU-5, GU-105, GU-116) in June, 2020, and at Capre Cave (GDC-6, GDC-8, GDC-0) in June, 2021 . These dates constrain the age of a Strombus-bearing biodetritic conglomerate associated with a tidal notch occurring at 9.5 m a.s.l. at Cape Circeo between 121.5±5.8 and 116.2±1.2 ka. Moreover, deposition of backbeach deposits intercalated in the sedimentary filling of Guattari and Capre coastal caves is bracketed in the interval 110.4±1.4 ka to 104.9±0.9 ka. Such deposits are directly correlated with a tidal notch at ~2.5 m associated with another biodetritic conglomerate at Cape Circeo. The latter is correlated with the adjacent marine terrace, occurring at 3-5 m in the coast between Capes Circeo and Anzio, for which a maximum age of 100.7±6.6 ka was previously reported. These data provide evidence for a maximum sea level around 9.5 m above the present sea level and a duration of MIS 5.5 highstand until 116 ka, in line with estimation from other regions in the world. In contrast, they suggest a maximum sea level during MIS 5.3 highstand that is similar to the present level, and only ~7 m lower than the MIS 5.5 highstand, challenging the reconstructions of the MIS 5 ice-sheet volumes and derived global sea levels that are based on the benthic oxygen isotope records.

Description: The AND-1B drill core recovered a 13.57 million year Miocene through Pleistocene record from beneath the McMurdo Ice Shelf in Antarctica (77.9°S, 167.1°E). Varying sedimentary facies in the 1285 m core indicate glacial-interglacial cyclicity with the proximity of ice at the site ranging from grounding of ice in 917 m of water to ice free marine conditions. Broader interpretation of climatic conditions of the wider Ross Sea Embayment is deduced from provenance studies. Here we present an analysis of the iron oxide assemblages in the AND-1B core and interpret their variability with respect to wider paleoclimatic conditions. The core is naturally divided into an upper and lower succession by an expanded 170 m thick volcanic interval between 590 and 760 m. Above 590 m the Plio-Pleistocene glacial cycles are diatom rich and below 760 m late Miocene glacial cycles are terrigenous. Electron microscopy and rock magnetic parameters confirm the subdivision with biogenic silica diluting the terrigenous input (fine pseudo-single domain and stable single domain titanomagnetite from the McMurdo Volcanic Group with a variety of textures and compositions) above 590 m. Below 760 m, the Miocene section consists of coarse-grained ilmenite and multidomain magnetite derived from Transantarctic Mountain lithologies. This may reflect ice flow patterns and the absence of McMurdo Volcanic Group volcanic centers or indicate that volcanic centers had not yet grown to a significant size. The combined rock magnetic and electron microscopy signatures of magnetic minerals serve as provenance tracers in both ice proximal and distal sedimentary units, aiding in the study of ice sheet extent and dynamics, and the identification of ice rafted debris sources and dispersal patterns in the Ross Sea sector of Antarctica.

Description: Magnetotactic bacteria intracellularly biomineralize magnetite of an ideal grain size for recording palaeomagnetic signals. However, bacterial magnetite has only been reported in a few pre-Quaternary records because progressive burial into anoxic diagenetic environments causes its dissolution. Deep-sea carbonate sequences provide optimal environments for preserving bacterial magnetite due to low rates of organic carbon burial and expanded pore-water redox zonations. Such sequences often do not become anoxic for tens to hundreds of metres below the seafloor. Nevertheless, the biogeochemical factors that control magnetotactic bacterial populations in such settings are not well known. We document the preservation of bacterial magnetite, which dominates the palaeomagnetic signal throughout Eocene pelagic carbonates from the southern Kerguelen Plateau, Southern Ocean. We provide evidence that iron fertilization, associated with increased aeolian dust flux, resulted in surface water eutrophication in the late Eocene that controlled bacterial magnetite abundance via export of organic carbon to the seafloor. Increased flux of aeolian iron-bearing phases also delivered iron to the seafloor, some of which became bioavailable through iron reduction. Our results suggest that magnetotactic bacterial populations in pelagic settings depend crucially on particulate iron and organic carbon delivery to the seafloor.