Woods Hole Oceanographic Institution

Masako Tominaga

»12. Seismic interpretation of pelagic sedimentation regimes in the 18-53 Ma eastern equatorial Pacific: basin-scale sedimentation and infilling of abyssal valleys
»11. Revised Pacific M-anomaly Geomagnetic Polarity Time Scale
»10. Lava Deposition History in ODP Hole 1256D: Insights from Log-based Volcanostratigraphy
»9. Origin of the smooth zone in early Cretaceous North Atlantic magnetic anomalies
»8. Determination of the volcanostratigraphy of oceanic crust formed at superfast spreading ridge: Electrofacies analyses of ODP/IODP Hole 1256D
»7. Paleomagnetic and rock magnetic results from lower crustal rocks of IODP Site U1309: Implication for thermal and accretion history of the Atlantis Massif
» 6. Deep-tow magnetic anomaly study of the Pacific Jurassic Quiet Zone and implications for the geomagnetic polarity reversal timescale and geomagnetic field behavior
»5. Velocity structure of upper ocean crust at Ocean Drilling Program Site 1256
»4. Drilling to Gabbro in Intact Ocean Crust
»3. Origin of the Pacific Jurassic quiet zone
»2. Paleomagnetism of the igneous section, Hoke 1213B, Shatsky Rise
»1. Shear-type borehole wall shifts induced during lost circulations

Masako Tominaga, Mitchell Lyle, and Neil Mitchell, 12. Seismic interpretation of pelagic sedimentation regimes in the 18-53 Ma eastern equatorial Pacific: basin-scale sedimentation and infilling of abyssal valleys, G cubed, accepted

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) abyssal 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 is 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 (CCD) 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 have 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 ~1.3 of the total vertical particulate rain.

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