Implications of Heat Flow and Bottom Water Temperature in the Eastern Equatorial Pacific

Summary The distribution of terrestrial heat flow through the sea floor of the eastern equatorial Pacific Ocean is compared to recent tectonic interpretations of this complex region. Some 500 values between 25° N to 20° S latitude, including 146 newly reported here, show that the theoretical distribution of heat flow for sea-floor spreading models matches well with smoothed data over portions of the Pacific, Cocos and Nasca lithospheric plates created within about the past 18 My from the East Pacific Rise. For the Galapagos Rift Zone, the fit is reasonable for lithosphere formed within the last 5 My only if a significant proportion of low heat-flow values is ignored. The heat flow on the Mathematicians’ Ridge and Galapagos Rise indicates that these were sea-floor spreading axes along which activity terminated about 5 and 10 My ago, respectively; this interpretation and its time scale are generally consistent with tectonic histories deduced from magnetic and topographic evidence. Detailed surveys and repeated measurements at stations suggest that localized heat-flow variability is frequently associated with topographic variability of the sea floor. Bottom water temperature profiles show that the East Pacific Rise is a barrier to eastward flow of waters at depths greater than 3 km, the approximate sill depth over the Nasca plate.

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