ПЕРВЫЕ ДАННЫЕ О ПОЗДНЕМЕЛОВЫХ ТЕРРИГЕННЫХ ОТЛОЖЕНИЯХ ВЕРХНЕЙ ЧАСТИ РАЗРЕЗА ЖУРАВЛЕВСКО-АМУРСКОГО ТЕРРЕЙНА В НИЖНЕМ ПРИАМУРЬЕ (ПО РЕЗУЛЬТАТАМ U/PB ДАТИРОВАНИЯ ЦИРКОНА)

Abstract

The study was performed on the age and composition of little-studied Cretaceous terrigenous deposits of lower Priamurie, which are part of the Zhuravlevka-Amur terrane and are referred to the Berriasian-Valanginian Komsomolsk Series. U/Pb dating of detrital zircons yielded reliable dates of 99 and 90 Ma for the Gorin and Pioneer formations, respectively. Thus, for the first time, a Late Cretaceous age of sedimentation was identified for the sedimentary complex within the Sikhote-Alin orogenic belt based on U/Pb dating of detrital zircons. In terms of composition and detrital zircon age distribution patterns, the studied rocks are similar to the sediments of the upper Hauterivian-Albian part of the Zhuravlevka-Amur terrane section, and not the Berriasian-Valanginian. In rocks of the Pioneer Formation, the youngest population of zircon with an age of about 90 Ma accounts for more than 40 % of all the dated grains. Andesites of the Bolba Formation and granitoids of the Nizhneamurskii Complex, which are distributed nearby are probably the main source of clastic material of this age. Felsic rocks of the Albian-Cenomanian igneous province of Pacific Asia were probably the source of detritus for sediments of the Gorin Formation of about 99 Ma. The issue of inconsistency between the Late Cretaceous age obtained by us and the paleontologically established Berriasian-Valanginian stratigraphic age of the formations requires additional research. New data on the Late Cretaceous age of sediments of the Zhuravlevka-Amur pull-apart continental margin basin invite further investigations to better understand the geologic evolution of the terrane and the Sikhote-Alin orogenic belt as a whole.