A LATE HOLOCENE PALEOENVIRONMENTAL HISTORY OF MASS MOVEMENT IN AN ANOXIC MARINE FJORD OF THE CENTRAL BRITISH COLUMBIA COAST MOUNTAINS

A late Holocene record of Northeast Pacific hydroclimate variability is recorded in a 5.8 kyr laminated sediment record punctuated by mass movement deposits in Frederick Sound, a highly restricted marine fjord in the extensive Seymour-Belize inlet complex of the central British Columbia Coast Mountains. Previous high-resolution studies of laminated sediments in marine fjords have been focused in the more southern Effingham and Saanich marine inlets of the Vancouver Island Range, where sediment deposition is more influenced by external oceanographic conditions and a rainfall-driven hydrologic regime. This new paleoenvironmental record archived in the highly terrigenous sediments of Frederick Sound extends the regional analysis of these records northward to the steeper terrain and glacio-nival hydrologic regime of the central British Columbia Coast Mountains. A depositional model constructed from high-resolution radiocarbon dating and sediment physical property measurements delineates lower sedimentation rates under environmentally quiescent conditions, when deposition is dominated by runoff and in situ productivity. These quiescent conditions are frequently punctuated by numerous mass movement deposits of varying physical properties, suggesting the more frequent and diverse activity of highly energetic depositional processes than those predominating in the anoxic fjord basins of southern British Columbia.