Some ages from Leg 104 Site 642 obtained by Rb-Sr glauconite dating and Sr isotope stratigraphy

Abstract

We have attempted to date several samples from Site 642 using a combination of Sr isotope stratigraphy and Rb-Sr dating of glauconite. A carbonate shell fragment gives a Sr isotope stratigraphy date of 17.3±1.0 Ma, which agrees well with available biostratigraphic and paleomagnetic data. Glauconites from a nearby sample give a similar date. One carbonate shell fragment and two fish teeth samples give concordant Sr isotope stratigraphy ages of about 37 Ma (latest Eocene). Rb-Sr glauconite analyses from one of the samples, while showing some substrate contamination, also support an Eocene age. As specific reworking of fish teeth and carbonate macrofossils (and also glauconite) from 37 Ma-old sediments into three different samples is most unlikely, we view the 37-Ma date as the depositional age of the core. -from Authors