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Upper Cretaceous volcanoclastic deposits from the Haţeg basin, south Carpathians (Romania): K-Ar ages and intrabasinal correlation

Bojar A.-V., Halas S., Bojar H.-P., Grigorescu D., Vasile S.

Geochronometria

2011

Vol. 38, no. 2

182-188

In order to constrain the age of the Upper Cretaceous continental Densuş-Ciula Formation from the Haţeg basin, South Carpathians, and correlate it with the other continental unit that occurs in the region, the Sânpetru Formation, we separated and dated by the K-Ar method biotites and amphi-boles from volcanoclastic deposits. The mineral phases analysed are from two tuff layers and volcanic bombs cropping out near Rachitova village. Two tuff layers from the Densuş-Ciula Formation give early Maastrichtian ages of 69.8š1.3 and 71.3š1.6 Ma, respectively. The ages determined for the tuff layers constrain the age of deposition for the Densuş-Ciula Formation and enable further correlations with the available palaeomagnetic data from the deposits occurring along the Sibişel Valley that be-long to the Sânpetru Formation. The volcanic bombs collected near to Răchitova village are andesites and dacites. The age determined by K-Ar method on hornblende separated from a volcanic bomb is 82.7š1.5 Ma, which is older than the underlying Campanian marine deposits in turbidite facies. This suggests that the volcanic bombs were re-deposited during the early Maastrichtian. Thus, the volcan-ics found at Răchitova have at least two origins: one type is related to an explosive synsedimentary volcanic activity, and the other type is represented by older andesitic/dacitic bombs, which most probably originate from a volcanic centre situated in the Haţeg region.

Luminescence and radiocarbon dating as tools for the recognition of extraterrestrial impacts

Stankowski W. T. J.

Geochronometria

2011

Vol. 38, no. 1

54-54

Extraterrestrial events and the extraterrestrial origin of both material and impact forms were recognized in the Morasko, Kaali and Przełazy shallow geological profiles by means of luminescence and radiocarbon dating as well as the frequency of magnetic spherules. The obtained results provide a promising tool for proving theat extraterrestrial events affected characteristic lithological and morphological environmental features.