1984 Articles

Oxygen isotope calibration of the onset of ice-rafting and history of glaciation in the North Atlantic region

Shackleton, N. J.; Backman, J.; Zimmerman, H.; Kent, Dennis V.; Hall, M. A.; Roberts, D. G.; Schnitker, D.; Baldauf, J. G.; Desprairies, A.; Homrighausen, R.; Huddleston, P.; Keene, J. B.; Kaltenback, A. J.; Krumsiek, K. A. O.; Morton, A. C.; Murray, J. W.; Westberg-Smith, J.

We report here that DSDP Site SS2A, cored with the hydraulic piston corer on the west flank of RockaU Bank, recovered an undisturbed sequence of alternating white deep-sea carbonate oozes and dark-coloured layers that are rich in glacial debris. Oxygen isotope analysis of the sequence together with detailed nannofossil and palaeomagnetic stratigraphy shows that the first major horizon of ice-rafting occurred at about 2.4 Myr, and was preceded by a minor pulse of ice-rafting at about 2.5 Myr. The carbon isotope record shows that the site has been bathed by a water mass of similar characteristics to present-day North Atlantic deep water at least since 3.5 Myr.