High-resolution seismic stratigraphy of late Quaternary deposits in Manitounouk Sound, northern Quebec: effects of rapid postglacial emergence

Manitounouk Sound contains a succession of postglacial deposits consisting of three acoustic units separated by disconformities. From base to top, the se are (1) a stratified draped unit interpreted as of glaciolacustrine and glaciomarine origin, (2) an onlapping basin-fill unit of thick transparent beds interpreted as gravity-flow deposits, and (3) a divergent fill unit of stratified and transparent modem marine deposits. The gravity-flow deposit s of unit 2 pass laterally into slide scars that truncate unit 1. Pollen an d dinoflagellate analysis of cores correlated with the acoustic sections in dicate that unit 1 is of early Holocene age and confirms a glaciomarine env ironment. Unit 3 contains modern assemblages of pollen and dinoflagellates. The slide scar and gravity-flow deposits of unit 2 correspond to the perio d of transition from glaciomarine to modern conditions and are interpreted to result from a period of relatively intense earthquake activity due to st ress release along faults during or shortly after the deglaciation of Hudso n Bay.