New U–Pb zircon ages of the Sandbian (Upper Ordovician) Big K-bentonite in Baltoscandia (Estonia and Sweden) by LA-ICPMS

Oscillatory-zoned euhedral single zircons from the upper Sandbian (Upper Ordovician) Kinnekulle K-bentonite exposed in a hillock at Pääsküla in Estonia and at the type locality on Mt Kinnekulle in Sweden were dated in a grain-by-grain manner by laser ablation-inductively coupled plasma mass spectrometer. The U–Pb (weighed mean) ages of the 25 grains from Mt Kinnekulle and 24 grains from Pääsküla are 453.4 ± 6.6 and 454.9 ± 4.9 Ma, respectively. This study provides the first ca. 454 Ma (late Sandbian) age for the Ordovician K-bentonite in northern Estonia and confirmed its correlation with the type Kinnekulle bed across the Baltic Sea.