EL LINEAMIENTO SANTA LÚCIA-AIGUÁ-MÉRIN (URUGUAY): UN CORREDOR TECTÓNICO EXTENSIVO Y TRANSCURRENTE DEXTRAL PRECURSOR DE LA APERTURA ATLÁNTICA

Abstract

THESANTALUC.A_AIGUA_MERIN LINEAMENT(URUGUAY): AN EXTENSIONALAND DEXTRALWRENCHING CORRIDOR RELATED TO THE EARLY ATLANTIC BREAK-UPTho Santa Lucía-Aigua-Merín Lineament (SaLAM) is a 450 km long structural conidor running across the southeastern cratonic area of Uruguay, flanked by the shores of the Río de la Plata and Laguna Metíu whete two pull-apart depocentels (Santa Lucía and Laguna Merín basins) are developed. The SaLAM exhibits three segments, bounded by the Sarandí del Yí and SierraBallena N-S trending regional faults. The southwestern segmeut is represented by the Santa Lucía basin filled with 2,500 m Mesozoic volcanoclastic sediments. The intermediate segment is represented by an uplifted crystalline basement block that shows thin volcanosedimentary Mesozoic remains. The northeastern segment shows important alkaline magmatism and contains the Laguna Merírr basin with Early Mesozoic volcanic rocks. The SaLAM was affected by two main tectonic phases: i) a Jurassic to Early Cretaceous extentional phase, lepresentèd by intraplate magmatisnr with few associated sediments, and ii) an Aptian-Albian dextral transtensive phase, with right-lateral strike-slip rnovement. The dextlal strike-slip pattern is supported by the attitude of both volcanic and clastic elongated depocentet's and coñtempomneous with the Santa Lucía, Minas, Aiguá, Lascano and Velásquez troughs. Additional structural support comes from: i) the geometry of the biecciated fluorine and quartz veins located on the southern border of the Aiguá trough; ii) the rombohedrical shape of the lnain cretaceous depocenters; and iii) the geometry of the high gravimetric anomaly in the Laguna Merín basin. The genesis of the SaLAM is associated with an'aborted rift, precursoiof the Àtlantic brèak-up. We suggest that the SaLAM was initially controlled by old structutes of the Gondwana crystalline basement during the continental rifting followed by a second strike-slip tectonic phase associated with the drifting movement that leä to the opening ofthtAtlantic. The integráted tectonic study ofthis colridor improves the stratigrâphic correlations between the contemporaíeous depocenters located at both extremes and support new econornic perspectives related with the colltrol on the ole aud enetgy resources of the region.