Seismic interpretation of pelagic sedimentation regimes in the 18–53 Ma eastern equatorial Pacific : basin-scale sedimentation and infilling of abyssal valleys
Figure S1: The summary of three representative sedimentation regimes from 24 h underway seismic profiles of jd80, jd91, and jd93. (70.48Mb)
Mitchell, Neil C.
MetadataShow full item record
Understanding how pelagic sediment has been eroded, transported, and deposited is critical to evaluating pelagic sediment records for paleoceanography. We use digital seismic reflection data from an Integrated Ocean Drilling Program site survey (AMAT03) to investigate pelagic sedimentation across the eastern-central equatorial Pacific, which represents the first comprehensive record published covering the 18–53 Ma eastern equatorial Pacific. Our goals are to quantify (1) basin-hill-scale primary deposition regimes and (2) the extent to which seafloor topography has been subdued by abyssal valley-filling sediments. The eastern Pacific seafloor consists of a series of abyssal hills and basins, with minor late stage faulting in the basement. Ocean crust rarely outcrops at the seafloor away from the rise crest; both hills and basins are sediment covered. The carbonate compensation depth is identified at 4440 m by the appearance of acoustically transparent clay intervals in the seismic data. Overall, we recognized three different sedimentation regimes: depositional (high sedimentation rate), transitional, and minimal sedimentation (low sedimentation rate) regimes. In all areas, the sedimented seafloor mimics the underlying basement topography, although the degree to which topography becomes subdued varies. Depositional regimes result in symmetric sedimentation within basins and subdued topography, whereas minimal sedimentation regimes have more asymmetric distribution of sediments within topographic lows and higher seafloor relief. Regardless of sedimentation regime, enhanced sediment deposition occurs within basins. However, we observe that basin infill is rarely more than twice as thick as sediment cover over abyssal hills. If this variation is due to sediment focusing, the focusing factor in the basins, as measured by 230Th, is no more than a factor of ∼1.3 of the total vertical particulate rain.
Author Posting. © American Geophysical Union, 2011. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 12 (2011): Q03004, doi:10.1029/2010GC003347.
Showing items related by title, author, creator and subject.
Evaluating Cenozoic equatorial sediment deposition anomalies for potential paleoceanographic and Pacific plate motion applications Mitchell, Neil C.; Dubois, Nathalie (2013-09)If equatorial sediments form characteristic deposits around the equator, they may help to resolve the amount of northwards drift of the Pacific tectonic plate. Relevant to this issue, it has been shown that 230Th has been ...
Comment on “Do geochemical estimates of sediment focusing pass the sediment test in the equatorial Pacific?” by M. Lyle et al. Francois, Roger; Frank, Martin; Rutgers van der Loeff, Michiel M.; Bacon, Michael P.; Geibert, Walter; Kienast, Stephanie S.; Anderson, Robert F.; Bradtmiller, Louisa I.; Chase, Zanna; Henderson, Gideon M.; Marcantonio, Franco; Allen, Susan E. (American Geophysical Union, 2007-03-06)
Lower export production during glacial periods in the equatorial Pacific derived from (231Pa/230Th)xs,0 measurements in deep-sea sediments Pichat, Sylvain; Sims, Kenneth W. W.; Francois, Roger; McManus, Jerry F.; Leger, Susan Brown; Albarede, Francis (American Geophysical Union, 2004-12-16)The (231Pa/230Th)xs,0 records obtained from two cores from the western (MD97-2138; 1°25′S, 146°24′E, 1900 m) and eastern (Ocean Drilling Program Leg 138 Site 849, 0°11.59′N, 110°31.18′W, 3851 m) equatorial Pacific display ...