Influence of rift jump and excess loading on the structural evolution of Northern Iceland

Abstract : New structural data combined with published structural and geochronological data allow reconstruction of the structural evolution that followed the last rift jump across northern Iceland. Tertiary lava flows erupted along the Skagafjördur paleo-rift have been down-bent under the weight of, and in the direction of, Plio-Pleistocene lava flows emitted from the Northern Volcanic Zone and the central part of Iceland. This down-bending process involved development of local flexure zones and a flexural extension along the resulting monoclines. This structural reorganization explains the existence of the Húnaflói-Skagi synform without need for a paleo-rift axis along it, in agreement with previous radiometric dating. The large amount of Plio-Pleistocene lava flows erupted in Central Iceland may have been enhanced by ice cap loading.