Permineralized plants in calcareous concretions from the Campanian, James Ross Basin, Antarctic Peninsula.

PIPO M.L.; IGLESIAS A.

General Roca

Congreso; 11° Congreso de la Asociacion Paleontologica Argentina; 2016

Asociacion Paleontologica Argentina

The Santa Marta Formation, in the basal section of the Marambio Group (James Ross Basin), mainly consists of Santonian-Campanian estuaric and marine platform deposits. Fossil plants, which were originally transported by the estuarine currents from the east margin of theAntarctic Peninsula, have been collected from the Beta Member (early-mid Campanian). They are stored in the ?Instituto Antártico Argentino? repository. The macroflora is diverse and known by compressions of leaves, seeds, wood and twigs. It has been recorded Cycads(Zamiaceae), conifers (Araucariaceae, Brachyphyllum, and Pagiophyllum), ferns (including Pteridaceae and Schizaeaceae?) and several angiosperms (including Cunoniaceae? and Lauraceae). Permineralized specimens in marine calcareous concretions from the same fossiliferous level have preserved vegetative and reproductive organs with delicate tissuessuch as parenchymatic cells from the mesophyll of leaves and branches pith, with exquisite three-dimensionall organic connections as well. This kind of preservation allows us to study the phylotaxis, disposition of vascular traces and secretory channels, and the fruit and seedsinner structure. The peel-technique is been used for the study of the material, using HCl and acetate sheets. The information obtained from the peels provides more precise taxonomy and more complete plant reconstructions. The whole descriptions and anatomical comparisonswith living relative taxa are a key to understand the continental environment were these plants lived, 80 million years ago, in so high latitudes of the Antarctic Peninsula.