Seven seismic units were identified: one of Tertiary age (U1), four of Pleistocene age (U2 U5) which are interpreted as 4th-order sequences deposited between MIS 11 and MIS 2, and Late Pleistocene (U6) and Holocene (U7) units corresponding with post-glacial sedimentation.
Persistent ice retreat in Cascade Canyon was slowed by an interval of small glacier activity between ∼13.5 and 11.5 ka, prior to the end of glacial lacustrine sedimentation ∼11.5 ka.
Ice ages result in the alteration of the landscape by glacial erosion and sedimentation; lead to the formation of periglacial permafrost; and impose significant transient hydraulic, mechanical, thermal, and chemical changes that can influence groundwater flow and radionuclide mobility.
Spatial and temporal variability of the FIS is illustrated by the gradual development of fast-flowing ice streams and associated intensification of focused glacial erosion and sedimentation since that time.
The data suggest that TMF continental slope progradation depends on short-lived episodes of extreme sedimentation during glacial maxima and during the early deglaciation phase, and that an important controlling factor is the mechanism of ice stream retreat from the continental shelf edge.
High mean sedimentation rates during glacial maxima of up to 18 kg m−2 yr−1 likely allow excess pore pressure to develop in the water rich plumites and hemipelagic sediments deposited in the previous deglacial period, particularly where such plumites attain a significant thickness.
Rather, they proposed that sedimentation in the Glacial Lake Missoula basin was the result of jökulhlaups draining into Lake Missoula from British Columbia to the north.
Destabilisation of sediment sources and increased sediment fluxes in the Late Quaternary followed millennia of climatic deterioration (cooling/aridity) and vegetation change and led to altered patterns of sedimentation during the Last Glacial Maximum (LGM).
Sedimentation increased during the Late Glacial and the early Holocene with an upwards fining of sediments in the lower part of the section.
Discrete acoustic units define four prominent sedimentation cycles, one Late-glacial and three Holocene, within the seismic stratigraphy.
