Chapter 20B. Miospores from Argentinian Triassic deposits and their potential for intercontinental correlation

ZAVATTIERI, A.M. & BATTEN, D.J.

Palynology: principles and applications

AMER ASSOC STRATIGRAPHIC PALYNOLOGISTS FOUNDATION

Lugar: Salt Lake City, Utah; Año: 1996; p. 767 - 778

The value of the palynological analysis as an aid to resolving stratigraphic and palaeoenvironmental problems within Triassic successions has increased enormously since the pioneering studies of three decades and more ago. Nevertheless, much remains to be done to improve the precision of subdivision and correlation of Triassic strata based on the occurrence of miospores. Among the most important reasons for this are uncertainties concerning the range of many taxa, and the scarcity of biostratographic markers. These may be linked both with insufficient taxonomic rigour and a lack of stratigraphic control, particularly with respect to the widespread nonmarine successions. Here, we review some of the characteristic miospore associations from Triassic basins in Argentina. They are defined mainly by the presence of certain palynomorphs and typically co-occurring forms. A selection of taxa from one of the formations is illustrated in Plates 1 and 2. We compare the associations with those encountered in successions elsewhere, chiefly in the Southern Hemisphere. Although there is little basis for long-distance correlation with palynofloras north of the equator, some of the taxa recorded are present also in European successions. The Triassic sedimentary successions of Argentina has been studied for more than a century. Stratigraphic relationships and correlations have been discussed by, among others, Rollery & Criado Roque (1968), Stipanicic (1969, 1983) and Strelkov & Alvarez (1984). Palynological stuies were iniciated by Orlando (1954) in a brief report on some palynomorphs from the Cacheuta Formation in Mendoza Province. Subsequently, Jain (1968) presented a more comprehensive analysis of the rich assembalges from the same formation, and Yrigoyen & Stover (1969) attemped to correlate various Triassic basins of Argentina mainly on genera of palynomorphs. More recent palynological studies on the Triassic have been documented by Azcuy & Longobucco (1983), Volkheimer & Zavattieri (1985, 1991), Zavattieri (1986, 1987, 1990a-c, 1991a, b, 1992a, b), Zavattieri & Volheimer (1992) and Zavattieri et al. (1994). Some of the taxa encountered have yet to be recorded elsewhere in the Gondwanan realm. All of the successions are continental, most of the assemblages having been recpovered from fluvial sequences.