Characterizing structural and lithologic controls on deep-seated landsliding: Implications for topographic relief and landscape evolution in the Oregon Coast Range, USA

Abstract

Research Article| May 01, 2005 Characterizing structural and lithologic controls on deep-seated landsliding: Implications for topographic relief and landscape evolution in the Oregon Coast Range, USA Joshua J. Roering; Joshua J. Roering 1Department of Geological Sciences, University of Oregon, Eugene, Oregon 97403-1272, USA Search for other works by this author on: GSW Google Scholar James W. Kirchner; James W. Kirchner 2Department of Earth and Planetary Science, 307 McCone Hall, University of California, Berkeley, California 94720-4767, USA Search for other works by this author on: GSW Google Scholar William E. Dietrich William E. Dietrich 2Department of Earth and Planetary Science, 307 McCone Hall, University of California, Berkeley, California 94720-4767, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Joshua J. Roering 1Department of Geological Sciences, University of Oregon, Eugene, Oregon 97403-1272, USA James W. Kirchner 2Department of Earth and Planetary Science, 307 McCone Hall, University of California, Berkeley, California 94720-4767, USA William E. Dietrich 2Department of Earth and Planetary Science, 307 McCone Hall, University of California, Berkeley, California 94720-4767, USA Publisher: Geological Society of America Received: 18 Jan 2004 Revision Received: 13 Sep 2004 Accepted: 05 Oct 2004 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (2005) 117 (5-6): 654–668. https://doi.org/10.1130/B25567.1 Article history Received: 18 Jan 2004 Revision Received: 13 Sep 2004 Accepted: 05 Oct 2004 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Joshua J. Roering, James W. Kirchner, William E. Dietrich; Characterizing structural and lithologic controls on deep-seated landsliding: Implications for topographic relief and landscape evolution in the Oregon Coast Range, USA. GSA Bulletin 2005;; 117 (5-6): 654–668. doi: https://doi.org/10.1130/B25567.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract In mountainous areas, landslides regulate temporal variations in sediment production and may suppress simple linkages between topographic development and tectonic forcing. Rates and mechanisms of mass wasting depend on lithology, bedrock structure, and climatic and tectonic setting. These factors tend to vary significantly in active tectonic regions, thus clouding our ability to predict how landsliding modulates topographic development over human and geological time scales.Here, we use a novel DEM-based technique to document the distribution of large landslides in the Oregon Coast Range (OCR) and quantify how they affect topographic relief. We developed an automated algorithm that exploits the distinctive topographic signature (specifically the relationship between curvature and gradient) of large landslides to map their distribution within the gently folded Tyee Formation (Eocene deltaic-submarine ramp sediments). In contrast to steep and highly dissected terrain frequently identified as characteristic of the OCR (which exhibits steep, planar side slopes and highly curved, low-gradient ridge tops and valleys), terrain prone to large landslides tends to have low values of both drainage density and curvature and gradient values that cluster between 0.16 and 0.44. The distribution of failur-dominated terrain in our 10,000 km2 study area is influenced by systematic variations in sedimentary facies and bedrock structure. The fraction of terrain altered by large landslides (>0.1 km2) varies from 5% in the sand-rich (delta-slope and proximal ramp facies) southern section of our study area to ∼25% in the north (distal ramp facies), coincident with an increase in the thickness of siltstone beds and a decrease in the sandstone:siltstone ratio. Local relief declines progressively northward, suggesting that deep-seated landsliding is sensitive to the thickness and frequency of low-shear-strength siltstone beds and may serve to limit topographic development in the OCR. Structural controls are superimposed on facies-related variations as deep-seated landslides are frequently found on slopes whose downslope aspect corresponds to the bedrock dip direction. For 1516 strike and dip measurements in our study area, we calculated the fraction of proximal terrain (<2.5 km) altered by deep-seated landsliding. In the sand-rich southern region, the proportion of proximal slid-dominated terrain increases modestly with bedrock dip. In the silt-rich northern region, terrain altered by deep-seated landsliding is pervasive, and an increase in dip from 0° to 16° corresponds to a change in the fraction