Roberto Linares

Investigating a Rock Art Site in Paraná State, South of Brazil

Jaguariaiva 1 is a sandstone rockshelter located in Jaguariaiva, Parana State, Brazil, with rock art on the surface of the walls and ceiling. A stratigraphic analysis of the soil within the shelter showed six occupational layers and a superficial disturbed layer with evidence from the end of the 19th century. The establishment of a rock-art chronology became possible using fallen painted rock sections incorporated into three sedimentary levels underlying this rock shelter. These show superimpositions of several pictures of differently sized animals, such as deer, and lattice motifs, which are generally associated with the Planalto rock art tradition. The chronological study was performed based on radiocarbon ( 14 C) analysis of charcoal collected from six excavated subsurface archaeological contexts. The two oldest layers, associated with hunters and gatherers of the Umbu tradition, were dated to 7680–7516 cal BP and 6913–6656 cal BP. There are four occupational layers from ceramists and farmers related to the south Je linguistic family, and linked to the Itarare-Taquara archaeological tradition: layer 3 linked to the oldest of such occupation, dated to 3058–2796 cal BP, followed by layer 4, dated to 2080–1701 cal BP. Layers 5 and 6, dated to 1995–1526 cal BP and 540–152 cal BP, respectively.

Exploring the 14 C Bomb Peak with Tree Rings of Tropical Species from the Amazon Forest

In this work we explore the radiocarbon ( 14 C) signal as an independent tool to assess the year of formation of individual tree rings of tropical species in northern Brazil. Three different species were analyzed in this work: Dipteryx magnifica , Enterolobium maximum , and Hymenolobium petraeum . The studied samples are from the stem of only one individual of each species, all cut down in 2008 in Porto Trombetas, Para, Brazil. Individual tree rings were identified based on wood anatomy and they were counted from bark to pith. Several rings were selected for 14 C analysis in order to cover the overall shape of the 14 C atmospheric bomb peak (after 1955). The 14 C content was measured at Laboratory of Radiocarbon, Universidade Federal Fluminense (LAC-UFF). Results are compared with the Southern Hemisphere 14 C atmospheric calibration curves. For E. maximum and H. petraeum the 14 C signal exhibits an overall good match with the SH zone 3 and suggests annual seasonality in the growth-ring formation. These species offer suitable characteristics for dendrochronology. The D. magnifica shows mismatches in the 14 C measurements that are likely a result of difficulties in identifying ring boundaries with certainty. Additional techniques may be helpful to disentangle the origin of this discrepancy.

A New {sup 14}C-AMS Facility at UFF- Niteroi, Brazil

We report a new Accelerator Mass Spectrometry facility at the Physics Institute of Fluminense Federal University in Brazil, the Nuclear Chronology Laboratory—LACRON. The sample preparation laboratory is ready to perform chemical treatment through graphitization and the acquisition of a Single Stage Accelerator Mass Spectrometry System is in progress. LACRON will be the first independent laboratory to perform the 14C‐AMS technique not only in Brazil but in Latin America.