Argentine Precordillera: Sedimentary and Plate Tectonic History of a Laurentian Crustal Fragment in South America

Abstract

The Argentine Precordillera ("Precordillera") is part of a larger terrane which is exotic to the western margin of Gondwana. This larger terrane is characterized by a Grenvillian-type basement and the presence of Laurentian carbonate-platform rocks of Cambrian-Ordovician age. The original position of the terrane is interpreted to be the Ouachita embayment of southeastern Laurentia.Terminal Neoproterozoic continental breakup and the formation of the Appalachian-Ouachita margin during the late Precambrian-Early Cambrian established a passive margin to the present east of the Precordillera. This passive margin is the original continental margin of Laurentia, which was located outboard of the Precordillera. Continuous crustal extension during the Cambrian along the Ouachita margin created a marginal plateau that accommodated the Argentine Precordillera carbonate platform. This marginal plateau to Laurentia was separated from mainland Laurentia by a deep graben system, today represented by the offshore Ouachita facies of the southeastern United States. The Cambrian through earliest Middle Ordovician mark the climax of the Laurentian episode because the Argentine Precordillera sediments and fauna are indistinguishible from Laurentia.In the carbonate platform succession of the Argentine Precordillera, the La Laja Formation marks the transition from rift-related redbeds to carbonate sedimentation. The La Laja Formation was deposited on a platform seaward of the nearshore siliciclastic trap but inboard of a (only partly exposed) carbonate belt which might have marked the platform margin. Several third-order cycles developed; differential rates of sea-level rise were the driving forces for cycle formation. Near the base of the La Laja Formation, a sandy interval is separated from the older rocks by a presumed hiatus. This hiatus might represent the Hawke Bay regression event of the eastern margin of Laurentia. Upper Cambrian limestones and dolostones of the Zonda and La Flecha Formations record the evolution of vast peritidal flats. The spatial and biostratigraphical relations between both formations are not clear and await further research. At present, it seems that the lower, more calcareous facies of the La Flecha Formation in the Guandacol subbasin is coeval to the dolomite facies of the Zonda Formation in the San Juan subbasin. The last important terrigenous input is noticed inMarjuman sediments of the La Flecha Formation, which marks a major shift in coastal onlap toward the hinterland. The Tremadocian La Silla Formation reflects a somewhat deeper environment, although open-marine rocks are absent. However, extensive tidal flats are also absent. The rocks are mud-dominated limestones and dolostones with locally abundant oolites. 1 Geological Society of America Special Paper 341 1999 on July 16, 2015 specialpapers.gsapubs.org Downloaded from Small-scale cycles are locally present. The general arrangement of facies is best explained by a tidal-flat island model. The La Silla Formation shows the most uniform facies deve...

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

“…(1986). 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).…”

Carbonate microfacies of the San Juan Formation (Ordovician: Oepikodus evae and Oepikodus intermedius conodont zones), Niquivil, Central Precordillera, Province of San Juan (Argentina)

“…1). It is composed of a variety of carbonate rocks that cover the entire range of carbonate textures (Keller, 1999 Lehnert (1993), recording from the Prioniodus elegans zone to probably the "Eoplacognathus" variabilis/ Microzarkodina flabellum subzone. Albanesi et al (2003Albanesi et al ( , 2006 Cañas (1995Cañas ( , 1999Cañas ( , 2002 (Fig.…”

A lowermost Ordovician tabulate-like coralomorph from the Precordillera of western Argentina: a main component of a reef-framework consortium

“…Within its 325 m of thickness (Fig. 2), three major lower-rank cycles have been recognized (Keller, 1999(Keller, , 2012Raviolo et al, 2007), each containing higher-frequency meter-scale cycles that record upward-shallowing trends.…”

“…Major type 1 sequence boundaries separate the La Silla Formation from the under-and overlying units (Cañas, 1999;Keller, 1999). Accommodation within this largely detached passive-margin setting is interpreted to relate to global sea-level fluctuations rather than with local subsidence (see Astini and Thomas, 1999;Thomas and Astini, 1999).…”

“…1). The La Silla Formation (Keller et al, 1994) is considered to be an ancient tropical Bahamian-type platform (Cañas, 1999;Keller, 1999;Pratt et al, 2012) that accumulated on a uniformly subsiding passive margin within the exotic Precordillera terrane (Astini et al, 1995;Gomez and Astini, 2015). Paleogeographically, by this time, the Precordillera terrane was drifting within the southern Iapetus Ocean (Astini et al, 1995;Benedetto, 2004;Keller, 2012).…”