Ecological reconstruction of a mixed Middle Triassic forest from Argentina

BREA, M., ARTABE, A. Y SPALLETTI, L.A

ALCHERINGA

Taylor & Francis

Lugar: Wollongong (Australia); Año: 2008 vol. 32 p. 365 - 393

0311-5518

This contribution aims to analyse the palaeoecology of an in situ Middle Triassic forest from the Paramillo Formation of Argentina. The forest was interpreted based on palaeobotanical, sedimentological and spatial analyses. The soil upon which the forest was developed is classified as an andisol, and was formed on volcaniclastic floodplain deposits. The burial of the forest was fast. The volcanic nature of detrital components and the rhythmic amalgamation of upper flow-regime tractional deposits indicate that the demise of the Paramillo trees was produced by a subaerial, cool and wet pyroclastic base surge flow. The permineralized stumps, which have been assigned to corystosperms and conifers, represent the dominant elements of the large in situ forest. The plant community reconstruction was based on the quantitative data of the mapped forest integrated with taxonomic and sedimentological information. The estimated tree heights were calculated. The overall distribution pattern was continuous with a density of 427 -759 trees/ha. Biomass and total basal area were calculated. The understorey was composed of Cladophlebis ssp. Coniferous wood growth ring analyses have been used to evaluate seasonality. Based on the coniferous quantitative analysis outlined by Falcon-Lang, the Araucarioxylon protoaraucana growth ring anatomy suggests that these trees could have been an evergreen habit. Structure of vegetation, growth ring analyses and sedimentation suggest that this evergreen subtropical seasonal forest developed under dry subtropical strongly seasonal conditions.