Specifics of the Formation and Syngenetic Deformations of the Sharvaozero Kame (North Karelia)

Abstract

A study of a section exposed in a quarry near ​​the village of Loukhi revealed a radial kame ridge composed of horizontally layered lacustrine sands with cross-bedded sand lenses and interlayers of siltstone with a 0.2- to 1.2-m-thick horizon of convolutions occurring as wide synclines, narrow anticlines, and pseudonodules. The lacustrine sediments overlain by sand and gravel sediments with paleosols down the slope of the ridge give way to moraine boulder sands overlying the heavily dislocated strata. The objective of this work is to analyze the conditions for the formation of the kame and the deformation structures in its section as possible indicators of paleoseismicity. To account for the structural features of the section, it is proposed that the ridge formed as a result of the projection of sediments of a flowing subglacial lake, which emerged in the body of the glacier during the deglaciation period, onto the moraine. A structural analysis of reverse faults in the dislocated sediments proved their gravitational nature, which is not evident from glaciotectonics, indicating the immobility of the ice mass during ridge formation. Convolutions are developed in layers of a narrow granulometric range (fine-grained sands and silts), which is significantly different from seismites in subaqueous sediments of highly seismic regions. Therefore, these structures are not associated with seismic liquefaction, although the section is 40 km from the southwestern side of the Kandalaksha graben, where Holocene 8.0-point paleoearthquakes with moderate magnitudes were revealed. Thus, the study did not confirm the occurrence of ​​paleoearthquakes with M ≥ 6–6.5 in the study area during the Late Ice Age.