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Data report: a revised biomagnetostratigraphic age model for Site U1338, IODP Expedition 320/3211

Jan Backman,2 Jack G. Baldauf,3 Marina Ciummelli,4 and Isabella Raffi5


The development of late middle Miocene through recent sedimentation rates was determined for Integrated Ocean Drilling Program Site U1338 in the eastern equatorial Pacific using available geomagnetic chron boundaries and biostratigraphic biohorizons provided by calcareous nannofossils and diatoms. These data were set in a revised depth splice of the three holes at Site U1338 and provide a lower resolution image of the sedimentation rate history in the region of Site U1338 through relatively long linear interpolations between 11 chosen age-depth control points encompassing 18 My. The resulting sedimentation rates depict the movement of Site U1338 from just south of the Equator with modest sedimentation rates starting at 11 m/My to tripling of these rates near 13 Ma, when the site moved onto the Equator and into the equatorial high-productivity belt. High sedimentation rates continued into the earliest Pliocene (5 Ma) except for a 50% decrease during the so-called “carbonate crash” centered around 9.6 Ma ± 0.4 My. The site’s movement north, away from the equatorial high-productivity belt, began between 5.0 and 4.2 Ma, when the site was located ~75–90 nmi north of the Equator, and resulted in a series of successively decreasing sedimentation rates to the present rate of 11 m/My, identical to the rate when sedimentation began at Site U1338 at nearly 18 Ma, when the site was located ~100 nmi south of the Equator.

1 Backman, J., Baldauf, J.G., Ciummelli, M., and Raffi, I., 2016. Data report: a revised biomagnetostratigraphic age model for Site U1338, IODP Expedition 320/321. In Pälike, H., Lyle, M., Nishi, H., Raffi, I., Gamage, K., Klaus, A., and the Expedition 320/321 Scientists, Proceedings of the Integrated Ocean Drilling Program, 320/321: Tokyo (Integrated Ocean Drilling Program Management International, Inc.). doi:10.2204/iodp.proc.320321.219.2016

2 Department of Geological Sciences, Stockholm University, SE-10691 Stockholm, Sweden.

3 Department of Oceanography, Texas A&M University, College Station TX 77843, USA.

4 Petrostrat Ltd., Tan-Y-Graig, Parc Caer Seion, LL32 8FA Conwy, United Kingdom.

5 Dipartimento di Ingegneria e Geologia, Università “G. d'Annunzio” di Chieti-Pescara, I-66013 Chieti Scalo, Italy.

Initial receipt: 8 September 2015
Acceptance: 5 November 2015
Publication: 11 February 2016
MS 320321-219