Journal of Geological Research

Review Article

Paleotsunami Inundation of a Beach Ridge Plain: Cobble Ridge Overtopping and Interridge Valley Flooding in Seaside, Oregon, USA

Table 6

Critical shear stress calculated from transported clast sizes.
SiteEventSettingMean clast shear stress dyne cm−2Large clast shear stress dyne cm−2Maximum clast shear stress dyne cm−2
867#1Deposit10 (s)——
3rd A#3,5?Eroded740 (c)870 (c)1130 (b)
712#1Deposit10 (s)——
822#2Deposit10 (s)15 (c)16 (c)
AveK#3,5?Eroded660 (c)930 (c)1140 (b)
j44#1Deposit10 (s)21 (c)26 (c)
j70#1Deposit10 (s)10 (p)—
AveN#3,5?Eroded820 (c)1080 (c)1260 (b)
832#1Deposit10 (s)——
j38#3Deposit—10 (p)—
j38#5Deposit—10 (p)—
j41#3Deposit—10 (p)—
j41#3Deposit—10 (p)—
Estimated ages of paleotsunami events (#) are shown in Table 2. Critical entrainment is evaluated for clasts in paleotsunami deposits (Deposit) and for representative clasts dislodged from cobble beach ridges (Eroded) as shown in Table 4. Critical entrainment shear stresses (dyne cm−2) are estimated for sand-sheet-flow (s) and pebbles (p) in sand-sheet-flow (~10 dyne cm−2), cobbles (c) in sand-sheet-flow (~15–26 dyne cm−2), and cobbles and boulders dislodged from cobble beach ridges (660–1260 dyne cm−2). Flow competence relations [24, 25] used for this analysis are shown in Table 3. Clast sizes are from Table 4.