Abstract

La Desirade Island in the Guadeloupe archipelago is a keystone of the structural framework of the Lesser Antilles island arc. Hypothetical ophiolitic series and wide discrepancy in the radiometric datings of its igneous basement have raised considerable debate concerning the structural significance of this island and the geodynamic constraints for the Caribbean plate. Recent detailed field work leads to a reconsideration of the problem. The volcanic basement of La Desirade can be subdivided into three independent units. The cherts interbedded in the unit 2 basalts contain Hauterivian-Barremian radiolarians that represent the oldest biostratigraphic assemblage found in the Lesser Antilles. This affirms the Jurassic radiometric age of the unit 1 trondhjemite outcrop. Observations and analyses allow us to discard the concept of an ophiolitic origin for La Desirade, whose basement was generated, like the northern half of the Lesser Antilles arc, by island-arc processes during the Mesozoic.

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