Antarctic Response to Orbital Forcing During the Intensification of Extensive Bipolar Glaciation (1.75–3.30 Ma) From Relative Paleomagnetic Intensity Stratigraphy of the Dove Basin, Scotia Sea

The sediments of “Iceberg Alley,” north of the Weddell Sea Embayment of Antarctica, are a key archive of Antarctic Ice Sheet and Southern Ocean history but are challenging to date at orbital timescales due to lack of foraminifera. We present a relative paleomagnetic intensity (RPI) chronology for sediments deposited across the Pliocene-Pleistocene Transition (3.14–1.75 Ma) at Dove Basin, International Ocean Discovery Program (IODP) Sites U1536 and U1537. Leveraging the well-defined magnetizations of these deep-sea contourite deposits, for the first time we correlate a Dove Basin RPI proxy to a North Atlantic RPI template that is intercalibrated with benthic δ¹⁸O and lithologic signals that record the history of Northern Hemisphere glaciation intensification (iNHG) from ∼2.7 Ma. Our new RPI chronology demonstrates a close relationship between sedimentation rates and physical lithology, with high accumulation occurring at times of high biogenic silica concentrations. This relationship is found at both long periods that reflect the amplitude modulation of orbital forcing and at glacial-interglacial timescales. Moreover, the chronology indicates a transition in the pacing of lithologic variability during iNHG from having greater precession-paced variations than benthic δ¹⁸O prior to 2.8 Ma and obliquity-paced variations after 2.6 Ma that are nearly identical to benthic δ¹⁸O. A clear and persistent influence of precession, especially during extreme early Pleistocene interglacial intervals (high biogenic silica and high accumulation rates) nevertheless persisted during times of high variance in both precession and obliquity forcing—most notable during Marine Isotope Stages 87, 89, and 91.