The paper presents results of geochronological and paleomagnetic studies of the volcanogenicsedimentary sequence of Henrietta Island in the East Siberian Sea. Our 40Ar/39Ar investigations confirm existing ideas that the bottom part of the section formed in the Ediacaran (~565 Ma) and that the basalts in the top of the section formed before the middle Cambrian (~520 Ma). Calculated paleomagnetic data confirm that during the rocks formation the territory of present-day Henrietta Island was located close to the 20A degrees latitude, which lets us adjust some information published earlier on the age and natural remanent magnetization of the dolerite dikes of the nearby Jeannette Island. The new data also let us propose that a regional tectonothermal event, probably caused by accretion-related processes, took place at the beginning of the Ordovician.
