HR: 1340h
AN: T23A-0537    [Abstracts]
TI: Thermal Cooling of Ocean Lithosphere - New Data - New Insights
AU: * Kominz, M A
EM: michelle.kominz@wmich.edu
AF: Michelle A. Kominz, Department of Geosciences Western Michigan University 1187 Rood Hall 1903 West Michigan Ave., Kalamazoo, MI 49008 United States
AU: Scotese, C R
EM: cscotese@uta.edu
AF: Christopher R. Scotese, Department of Geology University of Texas at Arlington Box 19049, Arlington, TX 76019 United States
AB: One of the fundamental sources of information for the nature and physical properties of the earth's lithosphere is the cooling history of the global oceans. We have revisited this relation applying updated age and depth data. Sediment thicknesses were derived from gridded NGDC ocean data while porosities were estimated by compilation of data from ODP data; porosity = 72 e^-z/462 for z = 0 to z = 100; and p=62 e^-z/1483 for z > 100; where depths are in meters and porosity is in %. Ocean depths between 2000 m and 7000 m were used. Age data was based on 1995 magnetic time scales. Applying the recent 2004 magnetic time scale to the data resulted in a slight flattening of the curve that was well within the error of the data. Age vs. depth relations were derived using gridded 0.1 x 0.1 degree data. Regression was also performed on the mean results from this data set and on means weighted by the area of each grid point. The weighted mean data differed from the grid point data by less than ± 30 m and showed a slight deepening trend with age. The relations with the highest correlation coefficient were: AP: z = 2785 + 275√t 0 to 90 Ma; r=0.75; pts=1,804,422 MP: z = 2620 + 316√t 0 to 51 Ma; r=0.99 pts=51 averaged from 1,208,149 pts WM: z = 2657 + 308√t 0 to 51 Ma; r=0.99 pts=51 averaged from 1,208,149 pts AP: z = 5754 - 2509 e^-t/62.3 r=0.75 pts = 2,416,097 MP&WM: z = 5301 - 2339 e^-t/32.1 r=0.99 pts = 110 averaged from 2,033,070 pts Where: AP = all points; MP = mid points, WM = weighted mid points; t = time in million years and z=depth in meters. Fitting the square root time and exponential relations to the mean values requires a tighter curvature. Age vs. depth relations were derived for 8 ocean basins including: the North, Central and South Atlantic; North, Central and South Pacific, the Indian and the Southern Ocean between Australia and Antarctica. Small ocean basins, the northern-most Atlantic and the Arctic Oceans were not included in the analyses. An inverse relationship was found between the slope and the intercept of the square root time relations of these basins, suggesting that higher spreading rates result in slower subsidence, consistent with recent asthenospheric flow models. Consideration of individual basins showed large deviations from a predicted exponential for old ocean floor, suggest that cooling to a plate model is not appropriate for the oceanic lithosphere.
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
DE: 8159 Rheology: crust and lithosphere (8031)
SC: Tectonophysics [T]
MN: Fall Meeting 2005