Late Miocene to Plio-Pleistocene volcanic and paleoenvironmental history of the Cerro Domo and Ventisqueros Mesa area, northwest James Ross Island, northern Antarctic Peninsula

Abstract

We present the description and interpretation of a James Ross Island Volcanic Group (JRIVG) succession around the Cerro Domo and Ventisqueros Mesa area. Our aim is to reconstruct the volcanic evolution and provide new palaeoenvironmental information for the northwest sector of James Ross Island, northern Antarctic Peninsula. We present representative stratigraphic logs that are combined with new chronological constraints provided by 40Ar/39Ar ages and 87Sr/86Sr isotope analyses that demonstrate a record of the late Miocene to earliest Pleistocene. The first volcanic activity registered is associated with tuff cone deposits that resulted from marine hydromagmatic eruptions, close to 6.18 ± 0.14 Ma. Subsequently, lodgement till deposits record a grounded glacial advance. Overlying the glacigenic deposits, fossil-bearing sediments record a marine or glacimarine environment following the ice sheet retreat, and an 87Sr/86Sr age of 6.02 (+0.09, −0.09) Ma dates ice-poor conditions. A lava-fed delta system, which yields an age of 5.37 ± 0.12 Ma, prograded over the previous deposits. Stacked pillow lavas, curvy columnar-jointed basalts and subaerial tabular lavas, with a 4.9 ± 0.10 Ma age, were emplaced after the lava-fed delta deposition. Another lava-fed delta located to the north of the previously volcanic units yielded an age of 3.57 ± 0.19 Ma. A glacial pavement carved into the top of these deposits records a second ice advance in the area. The final volcanic activity emplaced Cerro Domo, a large volcanic edifice which was the centre of explosive hydromagmatic eruptions. The presence of pristine, articulated bivalves in life position within the lower volcanic deposits of Cerro Domo, together with an 87Sr/86Sr age of 3.16 (+0.59, −0.43) Ma, are strong indicators of a marine environment and suggest ice-poor “interglacial” conditions at this time. Dykes cutting the volcanic deposits of Cerro Domo and considered coeval with the eruptions afford ages of 2.62 ± 0.08 and 2.72 ± 0.09 Ma. Our results provide new insights on the volcanic and glaciation history of James Ross Island, as well as supporting marine, ice-poor conditions around ~6 Ma, and near or right before the Plio-Pleistocene boundary, between ~3.2 and ~2.6 Ma.