The Ordovician chitinozoans from the western Gondwana margin, northwestern Argentina

DE LA PUENTE, G.S., RUBINSTEIN, C.V.

Tres Cantos, Madrid, España

Congreso; 4th European Meeting on the Palaeontology and Stratigraphy of Latin America; 2007

Instituto Geológico y Minero de España

Chitinozoans, marine organic-walled microfossils whose known species range from the early Ordovician (Tremadocian) to the latest Devonian (latest Famennian) (Paris et al., 1999a; Paris et al., 2004), are one of the palynomorph groups biostratigraphically important for the Ordovician (Servais and Paris, 2000). Currently, biostratigraphy is the main tool to correlate and determine the age of Ordovician sediments (Paris and Servais, 2005).There is chitinozoan information available for the main palaeogeographical domains: Laurentia (Achab, 1989; Achab et al., 2003), Baltoescandia (Nõlvak and Grahn, 1993; Nõlvak, 1999), and northern Gondwana (Paris, 1990; Paris et al., 1999b; Webby et al., 2004). This Ordovician chitinozoan database records assemblages that correspond to low, middle and high latitudes respectively.In Argentina, the study of Ordovician palynomorphs began in the late seventies (Volkheimer, 1978; Volkheimer et al., 1980; Bultynck and Martin, 1982) but has recently expanded with new findings in the Puna, Cordillera Oriental, Sierras Subandinas, Famatina System and Precordillera during the last two decades (Ottone et al., 1992, 1995, 1999; Rubinstein, 1997, 2001a,b, 2002, 2003a,b; Rubinstein et al., in press; Rubinstein and Astini, 2000; Rubinstein and Toro, 1999, 2001; Toro et al., 2003; Astini et al., 2003; Achab et al., 2006; Rubinstein and Vaccari, 2004; Aráoz and Vergel, 2006; Vecoli et al., 2006). As a whole, Ordovician chitinozoan information has been scarce in South America. The documented chitinozoan associations come from Bolivia (Heuse et al., 1999), Brazil (Grahn, 1992; Grahn and Paris, 1992), and Argentina (Volkheimer, 1978; Volkheimer et al., 1980; Ottone et al., 1992, 2001). In spite of the fact that Ordovician sediments in Argentina are widespread and occur in very thick successions, chitinozoans have not been extensively studied. Recently, Achab et al. (2006) have published palynomorph data from the Famatina area, which include chitinozoan descriptions. New studies on chitinozoans are being carried out in the CentralAndean Basin of northwestern Argentina, and some preliminary results have already been presented (de la Puente et al., 2005, 2006; de la Puente and Rubinstein, 2006; Rubinstein et al., in press). The Central Andean Basin is situated in the northwest part of Argentina extending into Chile, Bolivia and Peru and contains widespread Paleozoic sequences among others. It is regarded as one of the most spectacular areas in the world for the study of Gondwanan Ordovician sequences (Astini, 2003 and references therein).The aim of this contribution is to summarize the recent chitinozoan information available from Ordovician successions of Argentina. In this work, we use the Time Slices (TS) extracted from Webby et al. (2004).