Abstract
The Cemiterio Palaeolake deposit in Catalao, Goias State, Brazil, comprises a single, complete lacustrine sequence, dated from less than 27,500 ± 4000 yr B.P. to more than 51,780 ± 400 14C yr B.P. The unprecedented presence of spongillite and diatomite layers in this deposit was investigated using spicules of continental sponges as proxy data for environmental and climate reconstruction, which was relatively extensive for the ages examined. From the analysis of the sedimentary features and the associations of spicules preserved in the deposit, it was possible to reconstruct the evolution of the limnic system. Five developmental stages were thus identified, corresponding to the installation (lotic and erosion phase), establishment and development of the lake and its colmatation, the latter correlating to the Last Glacial Maximum (LGM). Moreover, based on the ecological requirements of the sponge species identified in the deposit, it was possible to infer the likely weather patterns related to respective phases of the lake. The presence of the sponge species Corvoheteromeyenia australis, presently recorded only from southern South America, indicated that polar incursions originating from the Antarctic were frequent during the last glacial period and might have played a notable role in what is now central Brazil. However, for a short time, drier and hotter weather conditions might have predominated, as suggested by the presence of the species Corvomeyenia thumi.
Highlights
Palaeoenvironmental and palaeoclimatic reconstructions of the Late Pleistocene, in the central re-How to cite this paper: Machado, V.S., Volkmer-Ribeiro, C. and Iannuzzi, R. (2014) Late Pleistocene Climatic Changes in Central Brazil Indicated by Freshwater Sponges
The layers formed predominantly of sponge spicules and others formed by diatom frustules, respectively spongillites and diatomites occurred in three Sections of the Cemitério Palaeolake (Table 1, Figures 2-4)
The spongillites were identified in Layer # 10 from Section 1, Layer # 15 from Section 2, and Layer # 8 (Figure 6(a), Figure 6(b)) from Section 3
Summary
Palaeoenvironmental and palaeoclimatic reconstructions of the Late Pleistocene, in the central re-How to cite this paper: Machado, V.S., Volkmer-Ribeiro, C. and Iannuzzi, R. (2014) Late Pleistocene Climatic Changes in Central Brazil Indicated by Freshwater Sponges. Spongillites and diatomites are evidences that natural environmental conditions can maximize the production of aquatic organisms with silicious supporting structures and generate large deposits of biosilicious rocks, formed in the case of the spongillites from sponge spicules [11] [19], and in that diatomites from diatoms frustules [20] [21] Studies on these deposits, in freshwater lentic environments, are typically rare, they have indicated their unique and preferred characteristics in relation to various contexts, including geomorphology [22]-[27], palaeoenvironment [19] [22] [26]-[28], palaeoclimate [19] [27] [29], and, in the case of diatomite, even orbitals [30]. To date, deposits of diatomites and spongillites have not been recorded in the same basin
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