The Hettangian-Early Pliensbachian Evolution Phase of the Anabar-Lena Sedimentary Basin, Nordvik Facies Region

摘要

New data on the structure and formation conditions of the Anabar-Lena sedimentary basin in the Nordvik facies region at the beginning of the Early Jurassic (Hettangian-early Pliensbachian) are presented. Based on a detailed lithofacies analysis, coastal-continental, coastal-marine, and shallow-marine sedimentation conditions were reconstructed. Ichnofacies studies were carried out for the first time: various traces of the vital activity of organisms identified as Scolithos and Cruziana ichnofacies were identified. An analysis of the relationship between individual lithofacies and their associations made it possible to identify a series of different rank cyclites in the section. In the general regressive series, six decameter-scale cyclites corresponding (except the basal, regressive migration regime of cyclogenesis) were established. They are characterized by an asymmetric internal structure, reflecting periods of coastline migration. The reconstructed model of the sedimentary sequence allows one to trace temporal changes in the sedimentation conditions and identify the main events in the sedimentary basin. It is established that the main Early Jurassic evolution phases in the western part of the Anabar-Lena paleobasin are reflected in the structure of the section and are caused by the alternation of transgressive and regressive periods against the background of a gradual attenuation of the regional tectonic activity. The results obtained allow us to significantly refine our understanding of sedimentation evolution in the Anabar-Lena basin. The revealed cyclical nature of the Lower Jurassic sequence can be used for the regional lithostratigraphic correlation.