Structure and evolution of the Easter plate

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Abstract
Seismicity, magnetic anomaly, and bathymetric data are used to interpret the tectonic structure and history of the Easter plate. The Easter plate is a small oceanic plate in an area of locally anomalous sea-floor spreading activity that internally disrupts the tectonic continuity of the Nazca-Pacific divergent plate boundary west of Easter Island. Active sea-floor spreading centers, mapped as the plate’s eastern and western boundaries, are positioned along the crests of two northwardly-trending topographic rises, herein referred to as the Este and Oeste Rises. Active fault zones characterized by rugged topography are mapped as the plate’s northern and southern boundaries. The fault zones are inferred by constraints of plate tectonics theory to presently connect the Este and Oeste spreading centers to segments of the Nazca-Pacific spreading center north and south of the Easter plate through ridge-fault-fault or ridge-ridge-fault triple junctions. Magnetic anomaly and bathymetric lineations, identified on the Easter plate and adjacent portions of the Nazca and Pacific plates, provide constraints used for reconstructing the evolution of the Easter plate. Our reconstruction shows the Easter plate to be 3.2 m.y. old, having been progressively generated by and between the Este and Oeste spreading centers since that time. We speculate that the Este spreading center is assuming a more dominant kinematic role relative to Nazca-Pacific plate divergence and that it will eventually be incorporated as a segment of the Nazca-Pacific spreading center. At that time, spreading activity on the Oeste Rise would have ceased, leaving the Eater plate as a captured crustal component of the Pacific plate. Furthermore, we speculate on possible genetic relationships between the Easter plate and the Easter-Sala y Gomez island-seamount chain, a major structural lineament transecting the Nazca plate eastward of the Easter plate.

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