Paleodrainage Insights Into the Fluvial and Glacial History of the Western Chukchi Margin, Arctic Alaska

• Main Author: Stockmaster, Brittany A.
• Format: Thesis
• Language: unknown
• Published: CCU Digital Commons 2017
• Subjects: Alaska; Chukchi; High-resolution subbottom data; Paleochannels; Paleodrainage; Paleovalleys; Geology; Arctic; Barrow Canyon; Chukchi Shelf; Barrow; Ice Shelf
• Online Access: https://digitalcommons.coastal.edu/etd/49; https://digitalcommons.coastal.edu/cgi/viewcontent.cgi?article=1048&context=etd

Chirp subbottom data collected from the Chukchi shelf, offshore of northwest Alaska, revealed extensive paleodrainage networks that incised the margin during sea level lowstands. These features are cut into folded Cretaceous bedrock strata and represent multiple sea level cycles. Several large incised valleys, 10s of km wide and up to 54 m deep, as well as numerous smaller, individual channels were identified. Sources of fluvial input include several, smaller rivers on the northwest Alaskan coast, such as the Kokolik, Kuk, Kukpowruk, and the Utukok Rivers. Correlation of sediment infill patterns provided insight to paleochannels and paleovalleys as well as outlined potential paleodrainage networks. Sediment infill and erosion patterns were examined to assess whether some of the valleys were formed by non-fluvial (i.e. glacial) processes. Results indicate the presence of four paleodrainage networks across the eastern Chukchi shelf based on shape, size, and infill of the paleovalleys: The Southern Valley, Northern Valley, Borderlands Valley, and Barrow Valley. All of the paleodrainage valleys are oriented perpendicular to the western Alaska coast except for Barrow Valley, which follows the northwest Alaskan coastline. All of the paleovalleys contain fluvial infill although some locations, such as the Southern and Barrow Valleys, appear to contain marine infill as well. Barrow Valley also appears to have negative erosional relief of up to 4.5 m on the transgressive surface, possibly from an ice shelf or other glacial features. The presence of ice may have also obstructed Barrow Canyon, which would explain why Barrow Valley appears to bypasses the large, shelf-indenting submarine canyon that presumably should have captured much of the drainage from northern Alaska.