The Argentine Precordillera: A Traveler from the Ouachita Embayment of North American Laurentia

Abstract

The Argentine Precordillera is a continental fragment rifted from the Ouachita embayment of the southern margin of Laurentia (North America) during Cambrian time [about 515 million years ago (Ma)] and accreted to the western margin of Gondwana (South America) during Ordovician time (about 455 Ma). Similarities of Cambrian stratigraphic successions and faunas, Grenville basement rocks, and dimensions link the Argentine Precordillera to the Ouachita embayment. Evidence of rifting during Cambrian time and of a wide ocean basin during Ordovician time indicates that the Precordillera traveled as an independent microcontinent to collide with Gondwana.

Sr, C and O isotope geochemistry and stratigraphy of Precambrian and lower Paleozoic carbonate sequences from the Western Sierras Pampeanas of Argentina: tectonic implications

“…Subsequent lithological, pa leogeographical and paleontological evidence was accumulated that reinforced the idea of a Lau rentian connection for the Argentine Precordillera (see Astini et aI., 1995;Thomas and Astini, 1996;Benedetto, 1998 and references therein;Keller, 1999), leading to models of Precordillera derivation and Laurentia-Gondwana interaction in the early Pa leozoic. In most of these models the Precordillera carbonate platform is seen as a remnant of the Lau rentian passive margin resulting from the break-up of Rodinia, amalgamated to the proto-Andean margin of Gondwana in early Paleozoic times (Dalla Salda et aI., 1992;Astini et aI., 1995;Thomas and Astini, 1996;Dalziel, 1997;Rapela et aI., 1998). Since recognition of a crystalline basement of Grenville age in the Sierra de Pie de Palo (McDonough et aI., 1993), the West ern Sierras Pampeanas have generally been integrated with the Precordillera as a single block of Laurentian derivation, the exotic Precordillera terrane (or Cuya nia) (Astini et aI., 1995;Ramos et aI., 1998;Dalla Salda et aI., 1998;Rapela et aI., 1998;Casquet et aI., 2001).…”

“…This terrane, often referred to in the geological literature as the Argentine Precordillera terrane (Astini et aI., 1995) has become a key piece for early Paleozoic Laurentia-Gondwana paleogeographic reconstructions (e.g. Astini et aI., 1995;Thomas and Astini, 1996;Dalziel, 1997;Acefiolaza and To selli, 1999;Condie, 2001;Thomas et aI., 2002). However, the precise age and manner of amalgamation of the Precordillera terrane is a long debated matter (e.g.…”

Regional deformation of the Sierra de San Luis, Argentina: Implications for the Paleozoic development of western Gondwana

“…During this period, the Precordillera terrane may have undergone the initial stages of rifting from the Ouachita embayment of southeastern Laurentia (present-day Texas [Thomas and Astini, 1996]; Figure 9a). Disagreement continues regarding the source location of the Precordillera, and other interpretations represent it as an extended ''plateau'' that remained attached to Laurentia following Neoproterozoic breakup [Dalziel, 1997], or as a suspect terrane that originated along the southwestern margin of western Gondwana (south of the Kalahari craton region [Aceñolaza et al, 2002]; Figure 9a).…”

“…Much of this research has focused on the Precordillera of western Argentina, an exotic terrane most often linked with a Laurentian origin [Dalla Salda et al, 1992a, 1992bAstini et al, 1995;Thomas and Astini, 1996;Dalziel, 1997], but also interpreted as a migratory terrane of Gondwanan affinity Toselli, 1988, 2000;Aceñolaza et al, 2002;Finney et al, 2003]. Interaction of the Precordillera with Gondwana is part of a complex tectonic sequence that likely initiated with east directed subduction off the west coast of Gondwana (present-day coordinates) in the Early Cambrian, and included multiple collisional episodes throughout the Early to Middle Paleozoic [Aceñolaza and Toselli, 1976;Ramos, 1988;Aceñolaza et al, 1990;Durand and Aceñolaza, 1990;Astini et al, 1995;Kraemer et al, 1995;Durand, 1996;Davis et al, 1999].…”

Ordovician back arc foreland and Ocloyic thrust belt development on the western Gondwana margin as a response to Precordillera terrane accretion

“…Astini et al, 1995]. This microplate has been interpreted as a driftedrifted crustal block from the Ouachita embayment of southeastern Laurentia [Thomas and Astini, 1996;Dalziel, 1997;Astini, 1998a] that accreted to western Gondwana by MidLate Ordovician time [e.g., Astini et al, 1995;Thomas and Astini, 2003]. On the basis of preliminary analyses of detrital zircons [Finney et al, 2003a], the Laurentian origin of the Argentine Precordillera has recently been questioned, which in turn, greatly modifies the plate tectonic reconstructions (for a thorough dis-cussion, see Aceñolaza et al [2002]; Astini and Rapalini [2003]).…”