The Jura-Cretaceous tectonic Lineament of Santa Lucia-Aiguá-Merin (Uruguay): Kinematic evidences of dextral transcurrent faults and preexisting structural controls.

Abstract

There are new evidences providing a general oblique-extensional kinematics associated with dextral transcurrent displacement within the Santa Lucia-Aiguá-Merin rift-zone in Uruguay, during the Juro-Cretaceous period. It was studied in two particular regions from the Uruguayan Shield's central domain: i) West from Minas's region, with the presence of a basic dyke swarm, some subordinate faults cutting Lavalleja Group, and the dextral dragging of Precambrian quartzites in the southern edge of Santa Lucia Basin, and ii) Southeast from Mariscala's region, where various E-W graben (i.e. Aigua, Mariscala...) show remnants of Juro-Cretaceous volcanic rocks. Their assemblage may provide clues to interpret them as parts of a transcurrent system. Santa Lucia-Aigua-Merin rift developed in NE direction, with border zones controlled by N70ºE strike faults, reworking the preexistent basement anisotropies. These anisotropies are quite different in each domain of Uruguayan Shield (almost 3). In the central domain, N15ºE and N50ºE striking ones are conspicuous. Finally, in this transtensional environment, the age of some conglomeratic units are discussed as well as the tectonic and economic significances from the Laguna Merin strong gravimetric anomaly, that is located in the rift's eastern edge.