NEW 40AR/39AR AGES OF CRETACEOUS CONTINENTAL VOLCANICS FROM CENTRAL CHUKOTKA: IMPLICATIONS FOR INITIATION AND DURATION OF VOLCANISM WITHIN THE NORTHERN PART OF THE OKHOTSK CHUKOTKA VOLCANIC BELT (NORTHEASTERN EURASIA)

Abstract

We used the single-crystal sanidine laser fusion Ar-40/Ar-39 method to date five samples of volcanic rocks from the northern (Chukotka) part of the Cretaceous Okhotsk-Chukotka volcanic belt (northeastern Eurasia). Ages of four samples from lowermost stratigraphic units range from 87.94 to 87.08 Ma, and one sample from the top of the section shows the age of 87.55 Ma. New results combined with previously published Ar-40/Ar-39 data indicate that volcanism within the northern part of the belt started in Coniacian time, at ca. 88 Ma, and was very short-lived (ca. 1-6 m. yr.).