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

Table 4

Paleotsunami clast sizes from the Seaside beach plain.

Site	Event	Transport condition	Depth (m)	Bed clast size 𝐷𝐵±1𝜎 cm	Largest clast size 𝐷𝑚 (cm)	Maximum clast size𝐷max (cm)
867	#1	Deposited	0.5	0.02	0.02
3rd Ave	#3,5?	Eroded	Ridge	9.1±3.8	13.6	26
712	#1	Deposited	0.3	0.02	0.02
822	#2	Deposited	0.9	0.02	5.2	6.0
AveK	#3,5?	Eroded	Ridge	8.1±5.3	19	32
j44	#1	Deposited	1.2	0.02	12.4	20
j70	#1	Deposited	0.7	0.02	2.0^∗
AveN	#3,5?	Eroded	Ridge	10±5	20	30
832	#1	Deposited	1.1	0.02	0.02
j38	#3	Deposited	2.0	0.02	2.0^∗	—
j38	#5	Deposited	3.2	0.02	2.0^∗	—
j41	#3	Deposited	1.5	0.02	2.0^∗	—

Paleotsunami events (#) are presented in Table 2.
Bed grain size includes mean (𝐷_𝐵) with ±1 std Dev (cm) from sample plot.
Largest clast sizes (𝐷_𝑚) are from the sample plots (0.25 m²) analyzed for each site.
Maximum clast sizes (𝐷_max) are from largest clast size observed in several sample plots from each site.
∗Deposited pebble sizes (sites j70, j38, j41) are taken from cores (diameter 2.5 cm) thereby limiting large clast size to less than 2.5 cm diameter.
Core sites 867, 712, 822, 832 are reported elsewhere [4], as are core sites j44, j70, j38, j41 [6]. Entrenchment sites 3rd Ave, AveK, and AveN, are first identified in this paper.
Eroded cobble sizes are taken from breached cobble ridge crests at 3rd Ave, AveK, and southwest of AveN. Deposited cobble sizes are taken from cutbank exposures at sites 822 and j44. See core site locations in Figures 6–14.