Evidence from IODP Site U1537 in the Dove Basin, Scotia Sea for a warmer Antarctica during the early Pleistocene (2.4-2.1 Ma)

IODP Site U1537 is located in a contourite deposit in the Dove Basin of the southeastern Scotia Sea, in 3,713 meters of water. It consists of alternating diatom oozes and silty clays, with variable amounts of sand to gravel-sized clasts delivered as IRD.   Shipboard track measurements, weight percent ice-rafted detritus (IRD), ⁴⁰Ar/³⁹Ar hornblende and biotite age (provenance), and split core XRF elemental measurements were collected and examined to study Antarctic ice-sheet dynamics between 1.75 and 3.35 Ma, the Plio-Pleistocene transition. 

            The highest and most variable amounts of IRD (from 0 to >0.4 g/cm²/ky) are in the earliest part of the study before 3.24 Ma. Between 3.24 and 2.4 Ma, with the exception of one sample, IRD comprises < 0.2 g/cm²/ky of the sediment. Between 2.4 and 2.1 Ma, IRD form < 0.05 g/cm²/ky, and from 2.1 Ma to the end of the study, they return to values of < 0.1, g/cm²/ky. With the exception of the lowest IRD interval (2.4 and 2.1 Ma), ⁴⁰Ar/³⁹Ar ages of biotite and hornblende grains are sourced from both East and West Antarctica, with the majority being between about 400 and 600 Ma old, broadly corresponding to the Pan-African event, and the assemblage of Gondwana.

            The 300,000-year, diatom-rich, low IRD interval between 2.4 and 2.1 Ma is unique in that all of the grains, except one, came from West Antarctica. Other Antarctic sites such as IODP Site U1361 (Wilkes Land), and ODP Site 1011 (northwest tip of the Antarctic Peninsula), also have their lowest IRD values during this time interval. We propose that this was a warmer time interval and that icebergs from East Antarctica either melted before reaching the Dove Basin or there were no ice-terminating glaciers.