ODP Site 1092: revised composite depth section has implications for Upper Miocene ‘cryptochrons’.

An Upper Miocene magnetic polarity stratigraphy has been developed for the C3r to C5ABn interval of ODP site 1092 from the sub-Antarctic South Atlantic ( ). New data from X-ray fluorescence (XRF) scanning of half cores has led to development of a revised composite depth section for the site. This has implications for the magnetostratigraphic interpretation. Using the shipboard-derived composite section, four subchrons were identified within the normal polarity zone correlative to C5n.2n. The revised composite section results in subchrons C5n.2n-2 and C5n.2n-3 of becoming a single subchron recorded in two overlapping cores. The revised number of polarity subchrons within C5n.2n is now three, rather than four, which is consistent with the number of ‘cryptochrons’ recognized in marine oceanic anomaly data. [ABSTRACT FROM AUTHOR]