CONICET | Buscador de Institutos y Recursos Humanos

We analyze macrofloras from the north part of the James Ross Island at the Santa Marta and Snow Hill Island formations, Marambio Group, James Ross Basin. At the upper section of the Beta Member of the Santa Marta Formation, well preserved petrified trunks, charcoalified wood, and twists, leaves and seeds compression were collected. Leaves and seeds of angiosperms, podocarps and Araucaria are preserved with other plant debris in large calcareous nodules within fine-grained sands, escaping from bioturbation and taphonomical destruction. Some twists are preserved with attached large leaves of podocarps and Araucaria. Woody angiosperm leaves are quite diverse, with medium sizes (notophyll) and entire margins. Complete, small heteromorph ammonites in several orientations are generally associated with the plants, whereas inner-shelf coquina beds with charcoal are observed at the top of the unit. The ammonite assemblages indicate that this plant level is early-mid Campanian in age. At the Santa Marta Cove, the Snow Hill Island Formation shows less abundant plant debris. Small calcareous nodules in different levels have preserved diverse angiosperm and conifer woods. In some cases, the specimens conserved the external cortex of branches and twists with 3D leaf scar arrangement. Some large podocarp leaves were collected preserving stomata arrangement on the surface. The ammonite assemblages indicate a lateCampanian ? early Maastrichtian age for these plant levels. Facies analysis suggests the evolution of a progradational deep-water delta system. Plant remains may be transported seawards by deltaic currents from the continental areas of the Antarctic Peninsula. Systematic and taphonomic studies of these plants and other transported fossils (i.e. vertebrates) give evidence about how high-latitude continental environments were in Antarctica in places that today are permanently covered by ice.