Palaeoecology and palaeoenvironments of the Ameghino Petrified Forest (Danian), Chubut, Argentina

BREA M.; MATHEOS S.D.; RAIGEMBORN, M.S; IGLESIAS, A; ZUCOL, A.F. ; M. PRÁMPARO

GEOLOGICA ACTA

UNIV BARCELONA

Lugar: Barcelona; Año: 2011 vol. 9 p. 13 - 28

1695-6133

During the Early Paleocene (Danian), Central Patagonia had a warm-temperate climate and was dominated by evergreenconiferous forests. Abundant permineralized conifer woods along with some dicot and palm leaf compressions were found inthe Ameghino Petrified Forest, and provide evidence of this type of flora. All the permineralized wood and large trunks recoveredwere assigned to the species Podocarpoxylon mazzonii. An estimated tree height of 17-29m was calculated on the basis ofdiameter measurements. Based on 14 ring sequences, with a total of 169 rings, the mean ring width and Mean Sensitivity (MS)were 1.23 and 0.19mm respectively. The growth rings are moderately wide, extremely uniform and complacent, indicatingthat the environment was favourable and constant, and lacked significant stress factors limiting tree growth. Following thequantitative analysis for conifers outlined by Falcon-Lang, the growth ring anatomy of the Podocarpoxylon mazzonii suggeststhat these trees had an evergreen habit. The combination of the fossil flora, growth ring, and sedimentological analyses suggestthat this mostly evergreen coniferous forest developed under warm-temperate conditions and without limiting factors.