Rifting of oceanic crust at Endeavor Deep on the Juan Fernandez microplate |
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| Authors: | Emilie Hooft Martin Kleinrock Carolyn Ruppel |
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| Institution: | (1) Department of Geology and Geophysics, Woods Hole Oceanographic Institution, 02543 Woods Hole, MA, USA;(2) Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institue of Technology, 02139 Cambridge, MA, USA;(3) Present address: Department of Geology, Vanderbilt University, 37235 Nashville, TN, USA;(4) Present address: School of Earth and Atmospheric Sciences, Georgia Institute of Technology, 30332 Atlanta, GA, USA |
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| Abstract: | The development of an anomalously deep rift appears to be a common characteristic of the evolution of microplates along the East Pacific Rise, including the Galapagos, Easter, and Juan Fernandez microplates. We investigate crustal rifting at Endeavor Deep on the Juan Fernandez microplate using bathymetry, gravity and side scan sonar data. An initial phase of lithospheric extension accompanied by extensive subsidence results in the formation of a very deep rift valley (up to 4 km of relief, 70 km long and 20 km wide). Morphological observations and gravity data derived from GEOSAT satellite altimetry show the subsequent initiation of crustal accretion and development of a mature spreading center. Recent models of the kinematics of microplate rotation allow the amount of opening across Endeavor Deep over the past 1 m.y. to be quantified. We develop a simple mechanical model of rifting involving block faulting and flexural response to explain the gravity signature over the rift valley. The Bouguer gravity anomaly is asymmetric with respect to the surface topography and requires that a shallow-dipping fault on the western wall of the valley dominate the extension at Endeavor Deep. Consideration of three similar microplate rift valleys leads us to suggest that asymmetric rifting is the characteristic process forming microplate deeps. |
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| Keywords: | Extensional modeling Bouguer anomalies rift propagation microplate |
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