PALEOAMBIENTES SEDIMENTARIOS Y PALEOFLORA ASOCIADA EN EL TRIÁSICO TARDIO DE MALARGÜE (MENDOZA, ARGENTINA)

ARTABE, A.; MOREL, E.; SPALLETTI, L.; BREA, M.

Revista de la Asociación Geológica Argentina

Asociación Geológica Argentina

Lugar: Buenos Aires; Año: 1998 vol. 53 p. 526 - 548

0004-4822

Two stratigraphic units (Chihuíu Formation and Llantenes Formation) are recognized in the Triassic basin located to the south of Malargüe city (Llantenes locality, Tronquimalal stream and Chihuido hill). The Chihuíu Formation is composed of different proximal volcaniclastic facies deposited in humid- and volcanic-controlled alluvial fans and braid-plains. The Llantenes Formation is the record of a large, meromictic and ramp-shaped lake, developed under humid and temperate conditions. Several fluvial- and buoyancy-dominated deltaic mouth-bar deposits and distributary channel deposits intercalate in the Llantenes succession. The taphoflora found in the Chihuíu Formation is represented by 25 taxa, 5 first described and compared here. They are Dicroidium incisum (Frenguelli) Anderson & Anderson, D. odontopteroides var. odontopteroides (Morris) Gothan, D. lancifolium var. lineatum (Tenison-Woods) Retallack, Zuberia feistmantelii (Johnson) Frenguelli emend. Artabe and Pseudoctenis carteriana (Oldham) Du Toit. In the Llantenes Formation, 36 taxa have been recognized, 10 of them first mencioned in this paper. They are Dictyophyllum (T.) tenuiserratum (Menéndez) emend. Herbst, Dicroidium odontopteroides var. remotum (Szajnocha) Retallack, Zuberia zuberi (Szajnocha) Frenguelli, Z. feistmantelii, Pachydermophyllum pinnatum (Walkom) Retallack, Pseudoctenis carteriana, Baiera furcata (Lindley y Hutton) Braun, Baiera africana Baldoni, Linguifolium steinmannii (Solms-Laubach) Frenguelli and Cordaicarpus sp. Based on the palaeofloristic composition, an Upper Triassic age is proposed for the Chihuíu and Llantenes Formations. In the Chihuíu Formation the flora represents a deciduous forest associated with herbaceous and shrub communities developed along proximal fluvial systems. Three taphocenosis are defined in the Llantenes Formation. The first one is related to hipolimnic facies and represents the flora developed around the lake margins. As in the Chihuíu Formation, the other two taphocenosis are related to fluvial and delta plain environments.