An Early Cretaceous Volcanic Sequence in Central Israel and Its Significance to the Absolute Date of the Base of the Cretaceous

Abstract

Lower Cretaceous volcanics in Samaria, Central Israel, consist of a 230 m thick sequence defined as Tayasir Volcanics. It is subdivided into a Lower Basalt, a Tuff Member (a volcano-sedimentary unit), and an Upper Basalt. Concurrent normal faulting controlled the volcanic activity as well as the nature of the accumulation of the entire unit. K-Ar absolute ages are 144 and 148 m.a. for the lower flow and 133 and 134 m.a. for the upper flow. These represent Berriasian-Valanginian ages and suggest a slip rate of 0.015-0.018 mm/year along the main fault system. The Tayasir Volcanics are distinguished from other younger (110-120 m.a.) Lower Cretaceous volcanic occurrences previously described both in northern and southern Israel. Lower Cretaceous age of the volcanics is supported by field relations. It is concluded, therefore, that the absolute date of the base of the Cretaceous in the area is about the determined age of the lower basaltic flow. This conclusion is relevant to the numeric age determination of the Jurassic-Cretaceous boundary in general.