Tectonic Basis for Anaco Fault, Eastern Venezuela

Abstract

Within the Caribbean Coast Interior Range of eastern Venezuela a concentration of strike-slip faulting contrasts markedly with the province of normal faults on the southern limb of the Maturin basin. The Anaco thrust fault is within this tensional setting, and therefore appears to be somewhat anomalous. For this area of eastern Venezuela no tectonic model has been made that can explain adequately the Anaco fault. I propose that the Anaco fault is the result of third-order, left-lateral strike-slip movement within the stress field generated by the first-order El Pilar wrench fault bounding the Interior Range on the north. The acceleration, or bodily movement, of the Bergantin and Caripe blocks suggests that the Urica and San Francisco faults are second-order, strike-slip faults formed by first-order stresses reoriented into the vector of the second-order stresses to create a new direction for shearing and compression. The Urica fault and the folds and thrusts of the Bergantin block closely follow the application of the strain ellipsoid for deformation. Further analysis of the stress and strain found in northeastern Venezuela strongly suggests that the Anaco fault is a third-order, left-lateral trike-slip fault split off from the Urica fault. Formation of the associated domes found on the Anaco fault plate was controlled by the southeast bodily movement of the Parceles subblock which brings somewhat different facies and thicknesses of the Oficina Formation into juxtaposition. The southeastern acceleration was taken up by northwest-striking thrust faults between the domes. The building of the domes also imparted a vertical component to the Anaco fault plane and allowed an overthrust relation to form. Stresses generated by the El Pilar wrench-fault, which is postulated to be closely related to the right-lateral Venezuelan transform fault bounding the Caribbean and South American plates, are responsible for the structures found in northeast Venezuela.