Chronostratigraphy of CRP-2/2A, Victoria Land Basin, Antarctica

The 624.15 m glaciomarine sedimentary succession recovered in the CRP-2/2A drillcore comprises lower Oligocene (< c. 31 Ma) to lower Miocene (18.5 Ma) strata that are overlain by a thin succession of Pliocene and Pleistocene strata. The age model for the CRP-2/2A drillhole, as presented in this paper, is based on combined microfossil biostratigraphy, 40Ar/39Ar ages on volcanic material, 87Sr/86Sr analyses on mollusc shells, and correlation of a magnetic polarity zonation to the magnetic polarity time scale (MPTS). Between 25.92 and 109.05 metres below sea floor (mbsf), several alternative correlations to the MPTS are possible, all of which suggest that sediment accumulation rates averaged ~180 m/m.y. between unconformities, although actual sedimentation rates may have been higher. Between 109.05 and 306.65 mbsf, the age model is straightforward and average sedimentation rates were much higher (≥1000 m/m.y.). Between 306.65 mbsf and the bottom of the drillcore (624.15 mbsf), fewer datums are available to constrain the age model and unique correlation with the MPTS is not possible, although high average sediment accumulation rates are likely. A significant unconformity is identified at 306.65 mbsf, which may represent as much as 5 m.y. of missing time. Additional unconformities at 25.92 and 130.27 mbsf account for c. 16 and 2.5 m.y. of missing time, respectively. The Oligocene lower Miocene interval documented in the CRP-2/2A drillcore spans about 13 million years, however, it is possible that more time is missing in sequence-bounding unconformities than is represented in the stratigraphic record recovered in the CRP-2/2A drillcore.