Geologic controls on paleodrainage incision and morphology during sea level lowstands on the Cascadia shelf in Oregon, USA

Details

• Journal Title:
  Marine Geology
• Personal Author:
  Klotsko, Shannon ; Skakun, Matthew ; Maloney, Jillian ; Gusick, Amy ; Davis, Loren ; Nyers, Alexander ; Ball, David
• NOAA Program & Office:
  OAR (Oceanic and Atmospheric Research)
• Description:
  The lowstand extensions of two fluvial systems from the Cascadia subduction margin are investigated using high-resolution seismic reflection data to determine the relative controls on paleodrainage morphology. We document distinct differences between the two systems, located ~40 km apart, attributed to underlying structure and lithology, shelf gradient, and drainage basin characteristics. A cross-shelf valley exists for only one of the drainage systems, the Umpqua River. The outer shelf part of the valley is a syncline, which formed a natural structural low for lowstand drainage, while the inner shelf part of the valley exhibits incision and is associated with a mid-shelf convex change is slope. The other drainage system, the Siuslaw River, did not develop an across-shelf valley and is only denoted in the seismic data by an erosional subaerial unconformity. Structural trends are perpendicular to cross-shelf drainage, supporting a more anastomosing stream morphology for the paleo-Siuslaw. The shelf edge for this system was not exposed for a long period of time during the last lowstand, preventing substantial outer shelf incision. Differences in fluvial elevation, discharge, and hinterland geology, also played a role in the cross-shelf morphologies of the paleo-Umpqua and paleo-Siuslaw. These results highlight how controls on lowstand paleodrainage morphology can change over short distances on an active margin.
• Subjects:
  • Geochemistry and Petrology
  • Geology
  • Oceanography
• Keywords:
  • Geochemistry and Petrology
  • Geology
  • Oceanography
• Source:
  Marine Geology, 434, 106444
• DOI:
  https://doi.org/10.1016/j.margeo.2021.106444
• ISSN:
  0025-3227
• Format:
  PDF
• Publisher:
  Elsevier BV
• Document Type:
  Journal Article
• Funding:
  Grant no. NA16OAR0110197
• Rights Information:
  Accepted Manuscript
• Compliance:
  Library
• Download URL:
  https://repository.library.noaa.gov/view/noaa/57863/noaa_57863_DS1.pdf
• File Type:
  [PDF - 167.56 MB]
• Collection(s):
  Office of Oceanic and Atmospheric Research (OAR)
• Main Document Checksum:
  urn:sha256:2c340054381eb620b92bc041f768e4a6d8269aac57a994774a95b19eb489bc9e