Abstract

In this work we show some general patterns inferred from a rodent middens database that has been established in northern Chile. Most of these deposits are formed by Abrocoma (chinchilla rat) and Phyllotis (leaf-eared mouse) rodents. We review methods and approximations currently in use for paleoclimate reconstruction based on this biotic record of past environmental change. We include also the recent advances in paleoclimate reconstruction in the North of country. Since 1996, a total of 1025 middens have been collected in the Regions I to IV of Chile, of which 308 are dated by radiocarbon. For this analysis we classify the collection according to the biomes: 61% correspond to the Prepuna, 9% to the Puna, 7% to Semiarid and High-Andean, while 3% belong to the Coastal Mountains. Regarding the temporal distribution, 50% of middens are dated between 0-6 ka (ka = 103 cal year BP), while 11% range between 6-9 ka, 30 % between 9-14 ka, 5% between 14-19 ka; 3% correspond to 19-25 ka and 0,3% are >25 ka old. With regard to the forming agent, 43% are Abrocoma, Phyllotis is 32% and 20% are middens formed by more than one species. About 17% of these samples are undetermined. Diverse approaches for paleoclimatic reconstructions are currently used in the analysis of middens; the analysis of the composition and richness of plant macroremains as well as cuticles and pollen allow us to visualize the qualitative and quantitative changes on the seasonality and changes in precipitation. Among the most innovative approaches, direct measurements on Abrocoma feces allow for the assessment of quantitative variations in rainfall. Finally, we propose a meta-analysis project for the last 20 ka for the north of Chile using these samples to develop regional paleoclimate reconstructions. A potential application of this metadata is the analysis of niche conservatism through the niche modeling applications.