Holocene paleoclimatic reconstruction based on the Lagoa Dourada deposits, southern Brazil
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| Formato: | Artículo científico |
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Universitat de Barcelona
2003
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| _version_ | 1876481675768102912 |
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| author | M. S. Melo |
| author_facet | M. S. Melo |
| contents | Holocene paleoclimatic reconstruction based on the Lagoa Dourada deposits, southern Brazil M. S. Melo P. C. F. Giannini L. C. R. Pessenda M. Neto Brandt Ciencias de la Tierra Carbon isotopes Pond sedimentology Holocene paleoclimatology The Lagoa Dourada is a circular-shaped pond formed on the Furnas Formation (Devonian of the ParanáBasin), filled by late Pleistocene - Holocene sediments. It lies in the hydrographic basin of the Guabiroba River,a tributary of the Tibagi River situated in the Campos Gerais region of the State of Paraná, southern Brazil.The pond is about 200 m in diameter and the maximum water depth is 5.4 m. Geological, chemical, texturaland mineralogical studies on a core sample of the sediments collected from the Lagoa Dourada, 12.2 m thick,was obtained for investigations of paleoenvironmental changes as well as to provide additional data to supportprevious reconstructions based on palynomorphs and diatoms. Within the period recorded in the core, thepond has been filled by sandy material introduced by springs at the northern edge of the pond as well as bymuddy material brought in by floodwaters of the Guabiroba River. Thus, the sandy layers could be interpretedas evidence of drier climates with consequent diminution of fluvial overflow, but with maintenance of thesandy deposits coming from springs. The occurrence of euhedral pyrite in the sediments, locally associatedwith gypsum, may indicate periods of increase in the organic matter content or an increase in the water salinity,what could be related to greater evaporation under drier paleoclimate regimes. Three cycles defined byan increase in the total carbon content of the sediments of the pond were observed. These cycles seem to correspondto an increase in the isotope ratio 13C/12C (δ13C). Several hypotheses can be suggested to explain thepresence of these cycles, including the alternation of wetter or drier climatic phases. The convergence of thesedimentological data obtained during this study with previous microfossil paleoclimatic (pollens anddiatoms) indicators and radiocarbon dating suggests that a drier paleoclimatic phase occurred around8720±150 years B.P. The evidence for a second drier phase in more recent times is less consistent. This subsequentphase could correspond to the drier phase in southern and southeastern Brazil between 5000 and 3000years B.P. as suggested by other paleoclimatic studies. 2003 artículo científico 1695-6133 https://www.redalyc.org/articulo.oa?id=50510304 en http://www.redalyc.org/revista.oa?id=505 Geologica Acta: an international earth science journal application/pdf Universitat de Barcelona Geologica Acta: an international earth science journal (España) Num.3 Vol.1 |
| format | Artículo científico |
| id | redalyc_50510304 |
| institution | Redalyc |
| language | en |
| publishDate | 2003 |
| publisher | Universitat de Barcelona |
| spellingShingle | Holocene paleoclimatic reconstruction based on the Lagoa Dourada deposits, southern Brazil M. S. Melo Ciencias de la Tierra Carbon isotopes Pond sedimentology Holocene paleoclimatology Holocene paleoclimatic reconstruction based on the Lagoa Dourada deposits, southern Brazil M. S. Melo P. C. F. Giannini L. C. R. Pessenda M. Neto Brandt Ciencias de la Tierra Carbon isotopes Pond sedimentology Holocene paleoclimatology The Lagoa Dourada is a circular-shaped pond formed on the Furnas Formation (Devonian of the ParanáBasin), filled by late Pleistocene - Holocene sediments. It lies in the hydrographic basin of the Guabiroba River,a tributary of the Tibagi River situated in the Campos Gerais region of the State of Paraná, southern Brazil.The pond is about 200 m in diameter and the maximum water depth is 5.4 m. Geological, chemical, texturaland mineralogical studies on a core sample of the sediments collected from the Lagoa Dourada, 12.2 m thick,was obtained for investigations of paleoenvironmental changes as well as to provide additional data to supportprevious reconstructions based on palynomorphs and diatoms. Within the period recorded in the core, thepond has been filled by sandy material introduced by springs at the northern edge of the pond as well as bymuddy material brought in by floodwaters of the Guabiroba River. Thus, the sandy layers could be interpretedas evidence of drier climates with consequent diminution of fluvial overflow, but with maintenance of thesandy deposits coming from springs. The occurrence of euhedral pyrite in the sediments, locally associatedwith gypsum, may indicate periods of increase in the organic matter content or an increase in the water salinity,what could be related to greater evaporation under drier paleoclimate regimes. Three cycles defined byan increase in the total carbon content of the sediments of the pond were observed. These cycles seem to correspondto an increase in the isotope ratio 13C/12C (δ13C). Several hypotheses can be suggested to explain thepresence of these cycles, including the alternation of wetter or drier climatic phases. The convergence of thesedimentological data obtained during this study with previous microfossil paleoclimatic (pollens anddiatoms) indicators and radiocarbon dating suggests that a drier paleoclimatic phase occurred around8720±150 years B.P. The evidence for a second drier phase in more recent times is less consistent. This subsequentphase could correspond to the drier phase in southern and southeastern Brazil between 5000 and 3000years B.P. as suggested by other paleoclimatic studies. 2003 artículo científico 1695-6133 https://www.redalyc.org/articulo.oa?id=50510304 en http://www.redalyc.org/revista.oa?id=505 Geologica Acta: an international earth science journal application/pdf Universitat de Barcelona Geologica Acta: an international earth science journal (España) Num.3 Vol.1 |
| title | Holocene paleoclimatic reconstruction based on the Lagoa Dourada deposits, southern Brazil |
| topic | Ciencias de la Tierra Carbon isotopes Pond sedimentology Holocene paleoclimatology |
| url | https://www.redalyc.org/articulo.oa?id=50510304 |