In-situ Late Triassic fossil conifer woods from the fluvial channel deposits of the Soturno River (Caturrita Formation, Rio Grande do Sul, Brazil)

Abstract

Three new fossil gymnosperm woods are described from a new outcrop exposed on the margins of the Soturno River, State of Rio Grande do Sul, eastward located in relation to other well-known petrified forests from São Pedro do Sul and Mata, in South Brazil. The interest of their study lays on the in situ condition of the woods and its inclusion in the fluvial deposits of the Caturrita Formation, at Faxinal do Soturno County, from where such kind of fossil material were known only recently. The analysis allows to assign it to the conifers Agathoxylon africanum (Bamford) Kurzawe and Merlotti, Megaporoxylon kaokense Kräusel and Chapmanoxylon sp. cf. C. jamuriense Pant and Singh. Previously known mainly from Permian localities of Gondwana (Namibia, India and South America), and with few Triassic representatives, the field relations and stratigraphic context suggest a Late Triassic age and a life around low sinuosity river systems under the influence of climatic seasonal dry conditions.

Keywords: fossil woods, Agathoxylon, Megaporoxylon, Chapmanoxylon, Late Triassic, Brazil.