Magnetostratigraphy of Lower Miocene Strata from the CRP-1 Core, McMurdo Sound, Ross Sea, Antarctica

A lower Miocene glaciomarine sequence was recovered in the lowermost 90 m of the CRP-1 core from McMurdo Sound, Antarctica. Palaeomagnetic studies were conducted to constrain the chronology of the core and to enable comparison with other records from the Antarctic margin and the Southern Ocean. The palaeomagnetic behaviour is generally stable and magnetite appears to be the dominant remanence carrier. A clear polarity zonation has been obtained, although a zone of mixed polarity between 143 and 148 metres below sea floor (mbsf) is probably remagnetised. For the interval from 43 - 143 mbsf, diatom biostratigraphy, ⁴⁰Ar/³⁹Ar dating and ⁸⁷Sr/⁸⁶Sr ratios provide constraints on correlations of the magnetostratigraphy with the magnetic polarity timescale (MPTS). The constraints imposed by the relevant data sets are not mutually consistent, therefore several possibilities exist for correlation with the MPTS. Our preferred correlation indicates that the record from 43 - 143 mbsf ranges in age from 21.5 Ma at the base to 17.5 Ma immediately beneath an unconformity at c. 43 mbsf, with as much as 2 m.y. missing in an unconformity beneath lodgement diamictite at 124.2 mbsf.