Ages of Pre-Rift Basement and Synrift Rocks Along the Conjugate Rift and Transform Margins of the Argentine Precordillera and Laurentia
Making the Southern Margin of Laurentia themed issue Ages of pre-rift basement and synrift rocks along the conjugate rift and transform margins of the Argentine Precordillera and Laurentia William A. Thomas1, Robert D. Tucker2, Ricardo A. Astini3, and Rodger E. Denison4 1Geological Survey of Alabama, 420 Hackberry Lane, P.O. Box 869999, Tuscaloosa, Alabama 35486-6999, USA 2U.S. Geological Survey, 12201 Sunrise Valley Drive, National Center, MS 926A, Reston, Virginia 20192, USA 3Laboratorio de Análisis de Cuencas, Universidad Nacional de Córdoba, Avenida Velez Sarsfi eld 1611, Ofi cino 7, 2° Piso, X5016GCA Córdoba, Argentina 415141 Kingstree Drive, Dallas, Texas 75248, USA ABSTRACT with Grenville-age rocks along the conjugate 1996, 1999, 2003; Astini and Thomas, 1999; margins of the Precordillera and Laurentia. Ramos, 2004). The Laurentian origin of the Pre- New geochronologic data from basement Ages from one newly analyzed collection, cordillera terrane is based on a variety of data rocks support the interpretation that the however, are older than those from other from Precambrian basement rocks, Early Cam- Argentine Precordillera (Cuyania) terrane basement rocks in the Precordillera. These brian synrift deposits, and a Cambrian–Ordovi- was rifted from the Ouachita embayment of ages, from granodioritic-granitic basement cian passive-margin carbonate succession (e.g., the Iapetan margin of Laurentia. New data clasts in a conglomerate olistolith in Ordo- Astini et al., 1995; Astini, 1998; Astini and from the Ozark dome show a range of ages vician slope deposits, are 1370 ± 2 Ma and Thomas 1999; Thomas and Astini, 1999, 2003; in two groups at 1466 ± 3 to 1462 ± 1 Ma 1367 ± 5 Ma.
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