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Data report: coarse fraction record for the Eocene megasplice at IODP Sites U1406, U1408, U1409, and U14111

P.M. Hull,2 S.M. Bohaty,3 A. Cameron,4 H.K. Coxall,5 S. D’haenens,2 D. De Vleeschouwer,6 L.E. Elder,2 O. Friedrich,7 K. Kerr,4 S.K. Turner,8 W.E.C. Kordesch,3 K. Moriya,9 R.D. Norris,10 B.N. Opdyke,11 D.E. Penman,2 H. Pälike,6 P.A. Wilson,3 P.F. Sexton,4 M. Vahlenkamp,6 F. Wu,12 and J.C. Zachos12


Integrated Ocean Drilling Program Expedition 342 recovered cores from multiple sites with expanded sections of Eocene sediments, often with exceptional carbonate preservation. These cores presented the opportunity to build an Eocene-spanning, orbital-resolution megasplice for refining the Eocene timescale and detailing paleoceanographic change in a high-latitude North Atlantic location. Here we present a sediment coarse fraction record (i.e., a record of the relative portion of >63 µm sized sedimentary particles), considered alongside shipboard estimates of sedimentation rates, from 8,674 of the 10,829 samples of the Eocene megasplice. Weight percent coarse fraction (wt% CF) data were collected in 10 different laboratories, but we find that long-term trends in wt% CF are robust to interlaboratory differences in sample processing. In particular, this record details a progressive decline in wt% CF from around 5%–8% around 50 Ma to lows of less than 1% around 36 Ma. The decline in weight percent carbonate from ~50–36 Ma is not monotonic; rather, it is interrupted by at least four local highs at around 46.5, 44, 41.7, and 39 Ma. Interestingly, the abrupt onset of drift sedimentation in the early middle Eocene at Site U1409 (~47 Ma) does not coincide with a step decline in wt% CF. Because the early Eocene section of Site U1409 has lower sedimentation rates (mean = 0.99 cm/ky) compared to the middle Eocene section of Site U1408 (mean = 3.08 cm/ky), the generally lower wt% CaC03 in the middle Eocene section of Site U1408 was hypothesized to be driven by clay dilution in shipboard discussions. However, within the sites with variable sedimentation rates (i.e., Sites U1411, U1406, U1408, and U1409), wt% CF exhibited weak covariance with sedimentation rates (highest r2 = 0.112; significant p-values for Sites U1411 and U1408 on pairwise correlation tests). Precise age models are thus needed to further resolve the relationship between the mass accumulation of clay, nannofossils, and foraminifer-dominated coarse fraction in these sections. Finally, within well-resolved intervals like the middle Eocene section of Site U1408, orbital scale variability is present in the wt% CF record, supporting shipboard observations of pronounced orbital variation in drift lithology (e.g., core color and weight percent carbonate).

1 Hull, P.M., Bohaty, S.M., Cameron, A., Coxall, H.K., D’haenens, S., De Vleeschouwer, D., Elder, L.E., Friedrich, O., Kerr, K., Turner, S.K., Kordesch, W.E.C., Moriya, K., Norris, R.N., Opdyke, B.N., Penman, D.E., Pälike, H., Wilson, P.A., Sexton, P.F., Vahlenkamp, M., Wu, F., and Zachos, J.C., 2017. Data report: coarse fraction record for the Eocene megasplice at IODP Sites U1406, U1408, U1409, and U1411. In Norris, R.D., Wilson, P.A, Blum, P., and the Expedition 342 Scientists, Proceedings of the Integrated Ocean Drilling Program, 342: College Station, TX (Integrated Ocean Drilling Program). doi:10.2204/iodp.proc.342.203.2017

2 Department of Geology and Geophysics, Yale University, CT 06520-8109, USA. Correspondence author:

3 Ocean and Earth Science, National Oceanography Centre Southampton, SO14 3ZH, United Kingdom.

4 Centre for Earth, Planetary, Space & Astronomical Research, The Open University, Milton Keynes MK7 66AA, United Kingdom.

5 Department of Geological Sciences, Stockholm University, SE-106 91, Sweden.

6 MARUM-Center for Marine Environmental Sciences, University of Bremen, 28359 Bremen, Germany.

7 Institute of Earth Sciences, Heidelberg University, 69120 Heidelberg, Germany.

8 Department of Earth Sciences, University of California Riverside, CA 92521, USA.

9 Department of Earth Sciences, Waseda University, Tokyo 169-8050, Japan.

10 Scripps Institution of Oceanography, La Jolla CA 92093, USA.

11 Research School of Earth Sciences, The Australian National University, Acton ACT 0200, Australia.

12 Department of Earth and Planetary Sciences, University of California Santa Cruz, CA 95064, USA.

Initial receipt: 23 March 2016
Acceptance: 21 October 2016
Publication: 11 January 2017
MS 342-203