Abstract

Preserved fold shapes usually reveal little about their kinematic evolution. Syntectonic strata preserved in growth synclines in contact with a fold, however, can permit “unfolding”: a sequential reconstruction of fold growth backward through time from a geometry observed at present to an initial undeformed state. Such reconstructions can define the kinematics of fold growth. Growth strata associated with anticlinal forelimbs in the Ebro basin exhibit depositional tapering of beds on fold flanks and progressive limb rotation. Unfolding a well-dated detachment fold defines its kinematic evolution and coevally varying rates of shortening, forelimb uplift, and forelimb rotation. Interplay of these rates with sedimentation rates controls onlap and offlap relations.

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