Resumo

MIRANDA-AVILES, Raúl; PUY-ALQUIZA, María Jesús  e  CAUDILLO-GONZALEZ, Martín. Stratigraphic and geochemical evidence of the temporal variation of natural and anthropogenic sediments on the Guanajuato river alluvial plain. Rev. mex. cienc. geol [online]. 2009, vol.26, n.3, pp.564-574. ISSN 2007-2902.

In this paper we analyze the stratigraphy of floodplain sediments from the Guanajuato river, based on sedimentology, ¹⁴C ages and geochemistry of trace elements of anthropogenic and natural sequences. The natural sediments were deposited in a floodplain environment between 7460 ± 40 BC (bottom) and 500 ± 50 BC (middle). Anthropogenic floodplain sediments, related to mining activities in the Guanajuato mining district, were deposited at least since 1660 ± 40 AD over the natural floodplain sediments. The stratigraphic interpretation is supported by trace elements analysis, which reveal that the anthropogenic floodplain sediments contain high levels of Pb, Zn and Cu as well as relatively low values of Cr and Ni, while the natural floodplain sediments, contain low values of Pb, Zn, Cu and high values of Cr and Ni. The combination of stratigraphy and geochemistry proves a useful tool in the detection and discrimination of natural and anthropogenic sediments related to the historic mining activity in the Guanajuato mining district.

Palavras-chave : stratigraphy; geochemistry; ¹⁴C age; river floodplain; anthropogenic sediments; natural sediments; Guanajuato river; Guanajuato mining district; Mexico.

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