Abstract

MOREL, Eduardo M et al. El triásico de la Formación Carrizal en el depocentro de Marayes (San Juan, Argentina): paleobotánica, tafonomía y bioestratigrafía. Rev. Asoc. Geol. Argent. [online]. 2015, vol.72, n.4, pp.456-469. ISSN 0004-4822.

In this contribution, we studied the fossil plants preserved as impressions-compressions from Carrizal Formation (Triassic), Marayes depocenter, San Juan, Argentina. The recognized taxa correspond to Equisetales (Equisetites fertilis (Frenguelli) Frenguelli, Neocalamites carrerrei (Zeiller) Halle), Osmundales (Cladophlebis kurtzi Frenguelli, C. mesozoica (Kurtz) Frenguelli), Corystospermales (Dicroidium lancifolium (Morris) Gothan, D. odontopteroides (Morris) Gothan, Peltaspermales (Scytophyllum cf. argentinum), Cycadales (Kurtziana brandmayri Frenguelli, K. cacheutensis (Kurtz) Frenguelli), Ginkgoales (Ginkgoites matatiensis), Voltziales (Heidiphyllum elongatum (Morris) Retallack), Gnetales (Yabeiella brackebuschiana (Kurtz) Ôishi). Furthermore, we realized a stratigraphic arrangement of the fossil plant record, describing three fossiliferous levels, one belonging to Arroyo Seco Member (lower) and two corresponding to Rickard Member (upper). In the bed-load dominated fluvial deposits of Arroyo Seco Member, the preserved taphocenosis, with the predominance of corystosperms, indicate the development of mesoxerophytic paleocommunities. In the Rickard Member, the fossiliferous levels, dominated by ferns and equisetales, indicate a paleocommunity formed under mesohydrophytic conditions, in a mixed-load fluvial system with low sinuosity. On the basis of the comparison with other Argentinean Triassic units, we can conclude that Carrizal Formation flora can be assigned to the Cortaderitian Stage (upper Middle Triassic and lower Upper Triassic).

Keywords : Paleobotany; Paleoenvironmets; Lower Mesozoic; Marayes Group.

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