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Data report: late Miocene to early Pliocene coccolithophore and foraminiferal preservation at Site U1338 from scanning electron microscopy1

Anna Joy Drury,2,3 Geoffrey P. Lee,2,4 Gillian M. Pennock,5 and Cédric M. John2


The late Miocene to early Pliocene carbonate-rich sediments recovered at Integrated Ocean Drilling Program (IODP) Site U1338 during the Expedition 320/321 Pacific Equatorial Age Transect (PEAT) program contain abundant calcareous nanno- and microfossils. Geochemical proxies from benthic and planktonic foraminiferal and coccolithophore calcite could be very useful at this location; however, good preservation of the calcite is crucial for the proxies to be robust. Here, we evaluate the preservation of specific benthic and planktonic foraminifer species and coccolithophores in fine fraction sediment at Site U1338 using backscattered electron (topography mode) scanning electron microscopy (BSE-TOPO SEM). Both investigated foraminiferal species, Cibicidoides mundulus and Globigerinoides sacculifer, have undergone some alteration. The C. mundulus show minor evidence for dissolution, and only some specimens show evidence of overgrowth. The Gs. sacculifer show definite signs of alteration and exhibit variable preservation, ranging from fair to poor; some specimens show minor overgrowth and internal recrystallization but retain original features such as pores, spine pits, and internal test-wall growth structure, whereas in other specimens the recrystallization and overgrowth disguise many of the original features. Secondary electron and BSE-TOPO SEM images show that coccolith calcite preservation is moderate or moderate to poor. Slight to moderate etching has removed central heterococcolith features, and a small amount of secondary overgrowth is also visible. Energy dispersive spectroscopy analyses indicate that the main sedimentary components of the fine fraction sediment are biogenic CaCO3 and SiO2, with some marine barite. Based on the investigations in this data report, geochemical analyses on benthic foraminifers are unlikely to be affected by preservation, although geochemical analyses on the planktonic foraminifers should be treated cautiously because of the fair to poor and highly variable preservation.

1 Drury, A.J., Lee, G.P., Pennock, G.M., and John, C.M., 2014. Data report: late Miocene to early Pliocene coccolithophore and foraminiferal preservation at Site U1338 from scanning electron microscopy. In Pälike, H., Lyle, M., Nishi, H., Raffi, I., Gamage, K., Klaus, A., and the Expedition 320/321 Scientists, Proc. IODP, 320/321: Tokyo (Integrated Ocean Drilling Program Management International, Inc.). doi:10.2204/iodp.proc.320321.218.2014

2 Department of Earth Science and Engineering, Imperial College London, SW7 2BP, United Kingdom.

3 Present address: MARUM-Center for Marine Environmental Sciences, University of Bremen, Leobener Strasse, DE-28359 Bremen, Germany.

4 Present address: School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, United Kingdom.

5 Department of Earth Sciences, Utrecht University, 3584 CD Utrecht, The Netherlands.

Initial receipt: 2 May 2014
Acceptance: 23 July 2014
Publication: 15 October 2014
MS 320321-218