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Maria Boni, Steven M. Reddy, Nicola Mondillo, Giuseppina Balassone, Rich Taylor

A distant magmatic source for Cretaceous karst bauxites of Southern Apennines (Italy), revealed through SHRIMP zircon age dating
doi: 10.1111/j.1365-3121.2012.01068.x

Terra Nova vol. 24, N° 4, p.326-332.

 

ABSTRACT

Karst bauxites occur at a Late Cretaceous hiatus on a Bahamian type platform in Southern Apennines, Italy. In contrast to the well-defined stratigraphic context, their origin remains controversial. Detrital zircon grains preserve textures and Th ?U ratios consistent with crystallization from a melt, occasionally around older cores. U-Pb isotopic data, collected using SHRIMP II, record several age populations. The youngest (around 90 Ma) falls into the age interval of bauxite formation as defined by stratigraphic criteria. The zircons must therefore be derived from a contemporary Cretaceous volcanic source. The older zircons may be interpreted as xenocrysts associated with the Cretaceous magmas or derived from different sources. Because the bauxite occurs on a isolated carbonate platform, the grains must come from far away sources, most probably transported by wind. The age, palaeogeography and inferred Cretaceous wind pattern are consistent with a prevailing origin from the Dinaric and Carpatho-Balkan orogenic belts, with its Cretaceous bimodal volcanism

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