39. SYNTHESIS OF STRATIGRAPHIC CORRELATIONS OF THE AMAZON FAN¹

David J.W. Piper,² Roger D. Flood,³ Stan Cisowski,⁴ Frank Hall,⁵ Patricia L. Manley,⁶
Mark Maslin,⁷ Naja Mikkelsen,⁸ and William Showers⁹

ABSTRACT

The older part of the Amazon Fan sequence penetrated on Leg 155 predates the last interglacial but is probably no older than oxygen isotopic Stage 8. The presence or absence of the zonal fossil E. huxleyi in sediments interpreted as isotopic Stage 7 appears variable, as the result of ecologic changes, dissolution, or reworking. Last interglacial highstand deposits are identified at Sites 942 and 946 from a microfossil assemblage, isotopic character, and the paleomagnetic Blake Event. They may have been removed by erosion by mass-transport deposits at other deep sites. The available data do not allow a consistent stratigraphy to be developed for the late Pleistocene (Stages 4 and 3) prior to the paleomagnetic Lake Mungo Excursion (32 ka).

A consistent correlation is developed for sequences younger than the Lake Mungo Excursion using oxygen isotopes of planktonic foraminifers, magnetic susceptibility, and paleomagnetic intensity and inclination. This correlation confirms that there is considerable variability in oxygen isotopic variations across the fan. The last glacial maximum is represented by the middle part of the Brown Channel-levee System. Shipboard seismic correlations are shown to be generally correct and confirm that major channel-levee systems formed sequentially. Several levees continued to accumulate mud with silt laminae, derived from flow-stripping of turbidity currents, after shifting of the active channel. A tentative age model is based on sparse ¹⁴C dates and the correlation of paleomagnetic intensity events with the global stack.

¹Flood, R.D., Piper, D.J.W., Klaus, A., and Peterson, L.C. (Eds.), 1997. Proc. ODP, Sci. Results, 155: College Station, TX (Ocean Drilling Program).
²Atlantic Geoscience Centre, Geological Survey of Canada (Atlantic), Bedford Institute of Oceanography, P.O. Box 1006, Dartmouth, Nova Scotia, B2Y 4A2 Canada. piper@agc.bio.ns.ca
³Marine Sciences Research Center, State University of New York, Stony Brook, NY 11794-5000, U.S.A.
⁴Department of Geological Sciences, University of California, Santa Barbara, CA 93105, U.S.A.
⁵Graduate College of Marine Studies, Robinson Hall, University of Delaware, Newark, DE 19716-3501, U.S.A.
⁶Geology Department, Middlebury College, Middlebury, VT 05753, U.S.A.
⁷Environmental Change Research Centre, Department of Geography, University College London, 26 Bedford Way, London WC1H 0AP, United Kingdom.
⁸Geological Survey of Denmark and Greenland, Thoravej 8, DK-2400 Copenhagen NV, Denmark.
⁹Department of Marine, Earth and Atmospheric Sciences, 1125 Jordan Hall, Box 8208, North Carolina State University, Raleigh, NC 27695-8208, U.S.A.