Depositional environments and sea-level changes deduced from Middle Weichselian tidally influenced sediments, Arkhangelsk region, northwestern Russia

Abstract

Deposits from a Middle Weichselian transgression, the Mezen Transgression, are found in coastal sections in the Mezen and Chyorskaya Bays, northwestern Russia. The marine event is bracketed between two ice advances from the Barents and Kara Sea shelves and dated by Optically Stimulated Luminescence (OSL) to around 60 kyr BP. The deposits represent a shallowing upward succession from offshore marine to intertidal coastal environments. Relative sea-level maximum was at least 40 m above the present owing to significant isostatic subsidence. The sedimentary record is dominated by shallow-marine, subtidal deposits bounded below by an erosion surface representing a downward shift in facies and above by subaerial exposure. The succession reflects deposition during forced regression due to isostatic uplift. A rapidly aggrading succession of subtidal deposits at one site suggests a relative sea-level rise or stillstand superimposed on the isostatically controlled sea-level fall. The rhythmic tidal deposits allow identification of semi-monthly to yearly cycles, providing an estimate of the sedimentation rate of 39 cm/year. This implies a high sediment yield and a rapid relative sea-level rise. We correlate this signal with the rapid eustatic sea-level rise at the end of OIS 4 known from deep-sea records.