Physical properties of seafloor sediments from the Russian Pechora Sea

Abstract

This study is the first of its kind in the English language that characterizes and quantifies the physical, acoustical, and geotechnical properties of the surficial marine sediments in the Pechora Sea. Profiles of bulk density, porosity, velocity, and shear strength for seven cores are presented and correlated with their corresponding lithological units and x-radiographs records. Furthermore, measurements of the above properties show the density profiles as sensitive and, consequently, better indicators of lithological changes downcore than the velocity profiles; conversely, the presence of large clasts and shell fragments are better indicated gn the velocity profiles. Sedimentological and geophysical Arguments support the glacial nature of Boulder Clay deposits within the study area, solving the long controversy regarding the marine or glacial origin for these late Pleistocene deposits in the Pechora area. An evaluation of the influence of the Novaya Zemlya and Scandinavian ice masses on the convergence character of the Pechora Sea and the direction of the ice flow are presented and supported by geophysical data and modified paleogeographical maps. Interpretation of high resolution seismic profiles and the correlation with their corresponding stratigraphic sections indicate that the regional seismic reflector Rl, called after Epshteyn et al. (1 983), corresponds to the top of the Boulder Clay. Furthermore, this reflector is either covered conformably by a thickness between 0 and 1 0 meters of the most recent deposits or crops out in small promontories as a hard bottom in the sea floor. The results of the grain size analysis of 28 surficial samples in the Pechora Sea indicate a close correlation between mean grain size and Total Organic Content (TOC). The medium to coarse silt range is associated with TOC values larger than 0.5%; th6 range of fine to very fine sands shows TOC values lower than 0.5%. These sands, located outside of the Pechora Gulf, exhibit well sorting as a result of the dynamic influence of the longshore current whose east directional flow is responsible for the formation of the Russkiy Zavarot Peninsula and the Ostrava Gulyayevskiye Koshki Islands.