Lithogeochemical Characteristics of Vendian Rocks in the Northern Patom Highland

Abstract

The results of analyzing litho- and isotopic geochemical indicators of the composition of paleocatchment areas, paleoclimate, and paleobioproductivity in rocks of the Mariinsk–Nokhtui interval (Upper Riphean?–Vendian–Lower Cambrian) in the northern Patom Highland (Lena–Zhuya region) are presented. It was found that the Th/Sc, Th/Co, and (La/Yb)_N values in the fine-grained clastic/clayey rocks, as well as the age of detrital zircons in sandstones of the Mariinsk–Barakun interval and the overlying deposits, are different, indicating the emergence of new sources of fine-grained aluminosiliciclastics in the pre-Ura or Ura periods. This is consistent with the conclusions in previous studies. Significant increase in ε_Nd (t) values and decrease in Nd model ages, recorded at the base of the Nikol’sk Formation, can be traced upsection to the Early Cambrian Nokhtui Formation. Based on the geochemical data on sediments in large modern rivers, the Vendian and Early Cambrian paleocatchment areas were likely composed of rocks influenced by the humid subtropical and tropical climate. The absence of a prominent negative correlation between the EF_P value and the ratios of several trace elements reflecting the rock composition in the paleocatchment areas, and, presumably, sedimentary basin types, suggests the lack of any significant relationship between the paleoproductivity and geodynamic settings in the Vendian.