Location

Portland State University

Start Date

2-5-2018 11:00 AM

End Date

2-5-2018 1:00 PM

Subjects

Geology--United States, Sedimentology, Erosion -- Oregon

Abstract

Eolian sand ramps are features that are sculpted from beach sand blowing up against sea cliffs or bluffs. In some coastal areas, sand ramp deposits only appear as the erosional remnants of pre-existing ramps that have been truncated at eroded shorelines, separating them from their previous sediment supply. Although sand ramp features have been observed in other areas on the western coast of the United States , they had not been studied or documented within the Lincoln City Dune Sheet (LINC) prior to this study – which documents the existence of truncated eolian sand ramps in LINC and uses them to estimate both a volume and rate of erosion since their initial deposition. The eroded volume was estimated to be 1.17X106 ± 4.4X105 m3; based on cross-sectional sand ramp areas calculated using the height of the eroded sea cliff, the slope of the sea cliff, the mid-beach slope, and an estimated pre-erosional sand ramp slope. Using radiometric dating, the beginning of sand ramp deposition was dated as 1,160 calBP. Given that erosion must have occurred some time after the onset of deposition, this date was used to create as average rate of erosion of 1.47X103 ± 3.78X102 m3/yr, or 1.47X106 ± 3.78X105 m3 per m of sea level rise (SLR), given 1 m SLR per ka for the last 3 ka within LINC.

Persistent Identifier

http://archives.pdx.edu/ds/psu/25027

Included in

Geology Commons

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May 2nd, 11:00 AM May 2nd, 1:00 PM

Estimating Sand Loss: Using Eolian Sand Ramps as a Proxy for Estimating Past Erosion within the Lincoln City Dune Sheet; Lincoln City, Oregon

Portland State University

Eolian sand ramps are features that are sculpted from beach sand blowing up against sea cliffs or bluffs. In some coastal areas, sand ramp deposits only appear as the erosional remnants of pre-existing ramps that have been truncated at eroded shorelines, separating them from their previous sediment supply. Although sand ramp features have been observed in other areas on the western coast of the United States , they had not been studied or documented within the Lincoln City Dune Sheet (LINC) prior to this study – which documents the existence of truncated eolian sand ramps in LINC and uses them to estimate both a volume and rate of erosion since their initial deposition. The eroded volume was estimated to be 1.17X106 ± 4.4X105 m3; based on cross-sectional sand ramp areas calculated using the height of the eroded sea cliff, the slope of the sea cliff, the mid-beach slope, and an estimated pre-erosional sand ramp slope. Using radiometric dating, the beginning of sand ramp deposition was dated as 1,160 calBP. Given that erosion must have occurred some time after the onset of deposition, this date was used to create as average rate of erosion of 1.47X103 ± 3.78X102 m3/yr, or 1.47X106 ± 3.78X105 m3 per m of sea level rise (SLR), given 1 m SLR per ka for the last 3 ka within LINC.