INVESTIGADORES
ALVAREZ maria fernanda
congresos y reuniones científicas
Título:
Phytoliths in sequences with icnites in coastal Buenos Aires, Argentina
Autor/es:
ARAMAYO, S.; M. OSTERRIETH; M.F. ALVAREZ; T. MANERA
Lugar:
Mar del Plata, Argentina
Reunión:
Otro; 7th International Meeting on Phytolith Research – 4th Southamerican Meeting on Phytolith Research; 2008
Resumen:
The sedimentary sequences carrying icnites or fósil traces of vertebrates are located on abrasion platforms in the supralitoral area of the beach. They stretch along 5 km parallel to the coastline between the seaside cities of Pehuén-Co and Balneario Monte Hermoso (latitude and longitude). The fossil footprints or icnites are numerous and were left by more than 20 different species of mammals and birds. The age of the site is 12, 000  110 years, which places it within the Upper Pleistocene (Aramayo and Manera de Bianco, 1987,1996). The highest frequency of icnites is found in pelites and diamictites of continental origin. These deposits have been attributed to ephemeral fluvial accumulations by Zavala and Quattrocchio (2001) and described as belonging to a wide variety of facies ranging from cohesive debris –flow, to distal levels consisting of graded tabular beds made up of sand and clay strata. Phytolith content in the sequence with fossil footprints of mammals and birds reaches approximately 30%; if the phytoliths that have not been defined are also included they reach over 40% of the total of mineral components. Diatoms are rare (2%), present only in the bird icnite area. As regards morphotype diversity, a greater variety can be noticed in the sediments with bird fossil footprints, even though they have lower levels, especially of short-cell grass, among which the bilobates, panicoids, trapeziforms and elongate long cells stand out. The sequences with megamammal fossil footprints are rich in big phytoliths, such as elongates, bulliforms and unciforms. The contents, the diversity in the morphologies that were found, and the state of preservation of the phytoliths would signal the presence of moderate grass vegetation covers, coincident with the moment when the footprints were left during the Upper Pleistocene in this area of the Pampean Plain.