HR: 0800h
AN: T41C-1326    [Abstracts]
TI: Global gravity, bathymetry, and the distribution of submarine volcanism through space and time
AU: * Watts, A B
EM: tony@earth.ox.ac.uk
AF: University of Oxford, Department of Earth Sciences, Oxford, Oxo OX13PR United Kingdom
AU: Sandwell, D
EM: dsandwell@ucsd.edu
AF: University of California, Scripps Institution of Oceanography, La Jolla, CA 92093-0225 United States
AU: Smith, W H
EM: walter@duck.grdl.noaa.gov
AF: NOAA, Laboratory for Satellite Altimetry, Silver Spring, MD 20910-3282 United States
AU: Wessel, P
EM: pwessel@hawaii.edu
AF: University of Hawaii, SOEST, Department of Geology and Geophysics, Honolulu, HI 96822 United States
AB: The seafloor is characterized by numerous seamounts and oceanic islands which are mainly volcanic in origin. Relatively few of these features (< ~0.1%) have been dated and so there is little known about their tectonic setting. One parameter that is sensitive to whether a seamount formed on, near, or far from a mid-ocean ridge is the elastic thickness, T_e, which is a proxy for the long-term strength of the lithosphere. Most previous estimates are based on using the bathymetry to calculate the gravity anomaly for different values of T_e and then, comparing the calculated and observed gravity anomaly. The problem is that bathymetry data are mostly limited to single-beam echo-sounder data acquired along a ship track and these data are usually too sparse to define the shape of the seamount. Therefore in this paper we use the satellite-derived gravity anomaly, which includes information on seamount shape, to find the T_e that best predicts the bathymetry. Comparisons with the T_e at sites of previous estimates and at sites where both sample and crustal ages are known show that bathymetric prediction is a robust way to estimate T_e and its lower and upper bounds. By comparing the predicted and measured bathymetry within windows centered on each locality in the Wessel (2001) global seamount database, we have obtained 9758 estimates of T_e from a large number of submarine volcanic features in the Pacific, Indian and Atlantic oceans. We have used the T_e estimates to estimate whether an individual seamount formed in an on-ridge, flank ridge or off-ridge setting. The most striking patterns are found in the Pacific ocean where a broad swathe of on-ridge volcanism extends from the Foundation seamounts and Ducie-Easter island line in the southeast, across the equator, to the Shatsky and Hess rises in the northwest. Interspersed among the on-ridge are flank ridge and off ridge estimates. The Indian and Atlantic oceans show a similar mix of tectonic settings. We estimate the total volume of the volcanism to be ~7.6×10⁶ km³ which suggests a submarine seamount addition rate of ~0.048 km³ a^-1. Rates probably varied through geological time, reaching their peak during the Early Cretaceous/Late Jurassic and then declining to the present-day. The decline since the Late Cretaceous correlates with an increase in strontium and oxygen stable isotopes, suggesting that some link might exist between submarine volcanism, hydrothermal activity, and seawater temperature.
DE: 1219 Gravity anomalies and Earth structure (0920, 7205, 7240)
DE: 3010 Gravity and isostasy (1218, 1222)
DE: 3075 Submarine tectonics and volcanism
DE: 8138 Lithospheric flexure
SC: Tectonophysics [T]
MN: Fall Meeting 2005