Reconstructing habitats in central Amazonia using megafauna, sedimentology, radiocarbon, and isotope analyses Dilce de Fa ´tima Rossetti, a, * Peter Mann de Toledo, a Heloı ´sa Maria Moraes-Santos, a and Anto ˆnio Emı ´dio de Arau ´jo Santos, Jr. b a Museu Paraense Emı ´lio Goeldi, Av. Perimetral, 1901, CP 399, CEP 66710-530 Bele ´m, PA, Brazil b Universidade Federal do Para ´, Centro de Geocie ˆncias, Campus do Guama ´ S/N, Bele ´m, PA, Brazil Received 14 November 2002 Available online 30 April 2004 Abstract A paleomegafauna site from central Amazonia with exceptional preservation of mastodons and ground sloths allows for the first time a precise age control based on 14 C analysis, which, together with sedimentological and y 13 C isotope data, provided the basis to discuss habitat evolution within the context of climate change during the past 15,000 yr. The fossil-bearing deposits, trapped within a depression in the Paleozoic basement, record three episodes of sedimentation formed on floodplains, with an intermediate unit recording a catastrophic deposition through debris flows, probably favored during fast floodings. The integrated approach presented herein supports a change in humidity in central Amazonia through the past 15,000 yr, with a shift from drier to arboreal savanna at 11,340 (F50) 14 C yr B.P. and then to a dense forest like we see today at 4620 (F60) 14 C yr B.P. D 2004 University of Washington. All rights reserved. Keywords: Amazonia; Pleistocene; Paleontology; Mammals; Sedimentology; Radiocarbon dating; Landscape evolution Introduction Deciphering the origin of the Amazon biodiversity has been a challenge to the scientific community with special interest in issues related to natural history and conservation of communities and ecosystems. An important aspect of this multidisciplinary field is the understanding of the main historical factors relating physical and biological phenome- na that acted upon the shaping of the modern biome as we see today. In order to reconstruct the origin and the historical events of the main ecological processes that took place to form the rain forest, an analysis and organization of a series of multidisciplinary data related to geology and climate and a reasonable control of the fossil history are needed. So far, geological and paleontological data are relatively scarce, considering the continental dimensions of the Amazon region, and the information available furnishes only a broad view on the evolutionary patterns. The building of historical datasets is an important contribution to the understanding of such a large and complex natural system. Although the entire history back to at least the Early Tertiary is relevant to these studies, the Pleistocene should be particularly addressed, as it bears the closest relationship with the modern ecosystem. Only a broad picture of what happened in the Amazon region during the major ecological shifts between ice-age aridity and more humid interglacial periods has been provided so far (reviewed by Latrubesse, 2000). This is mainly due to the following reasons: (1) geological, palynological, and vertebrate paleontological data are still scarce and spotty; (2) information refers only to some areas located in southeastern and southwestern Amazonia; and (3) the best information is related to times before 24,000 yr ago (Latrubesse, 2000). The incomplete information has moti- vated many debates, with the arid Amazonia refugia model (Haffer, 1969; Prance, 1982) on one side against stability of the forest throughout the Cenozoic on the other side (Colinvaux et al., 2000; Colinvaux and Oliveira, 2001). This paper reports a new fossil quarry bearing two megafauna elements consisting of Haplomastodon waringi and Eremotherium laurillardi from the locality of Itaituba, State of Para ´, northern Brazil (Fig. 1), in Central Amazonia, 0033-5894/$ - see front matter D 2004 University of Washington. All rights reserved. doi:10.1016/j.yqres.2004.02.010 * Corresponding author. Fax: (091) 249-0466. E-mail address: rossetti@museu-goeldi.br (D. de Fa ´tima Rossetti). www.elsevier.com/locate/yqres Quaternary Research 61 (2004) 289 – 300