Columbia River Basalt
87
SERIES GROUP SUB-GROUP FORMATION MEMBER K-Ar AGE (m.y) MAGNETIC POLARITY
MIOCENE
UPPER
GROUP
SUBGROUP
LOWER MONUMENTAL MEMBER 6 N
EROSIONAL UNCONFORMITY
ICE HARBOR MEMBER
Basalt of Goose Island
Basalt of Martindale
Basalt of Basin City 8.5
N
R
N
EROSIONAL UNCONFORMITY
BUFORD MEMBER
R
ELEPHANT MOUNTAIN MEMBER 10.5
R, T
EROSIONAL UNCONFORMITY
POMONA MEMBER 12
R
EROSIONAL UNCONFORMITY
ESQUATZEL MEMBER
N
EROSIONAL UNCONFORMITY
WEISSENFELS RIDGE MEMBER
Basalt of Slippery Creek
Basalt of Tenmile Creek
Basalt of Lewiston Orchards
Basalt of Cloverland
N
N
N
ASOTIN MEMBER
Basalt of Huntzinger 13
N
LOCAL EROSIONAL UNCONFORMITY
WILBUH CREEK MEMBER
Basalt of Lapwal
Basalt of Wahluke
N
UMATILLA MEMBER
Basalt of Sillius
Basalt of Umatilla
N
LOCAL EROSIONAL UNCONFORMITY
PRIEST RAPIDS MEMBER
Basalt of Lolo
Basalt of Rosalla 14.5
R
ROZA MEMBER
T, R
FRENCHMAN SPRINGS MEMBER
Basalt of Lyons Ferry
Basalt of Sentinel Gap
Basalt of Sand Hollow
Basalt of Silver Falls
Basalt of Ginkgo
Basalt of Palouse Falls
15.3
N
N
N, E
E
15.5
E
ECKLER MOUNTAIN MEMBER
Basalt of Shumaker Creek
Basalt of Dodge
Basalt of Robinette Mountain
N
N
N
GRANDE RONDE
PICTURE GORGE BASALT
(See Mangan and others, 1986;
Reidel, 1983 for individual flows) 15.6-16.5
N2
R2
N1
BASALT
R1
Musselshell
Julietta
IMNAHA BASALT
(See Hooper and others, 1984) 16.5-17.0
R1
T
N0
R0
Figure 2. Stratigraphy of the Columbia River Basalt Group. Modified from Swanson and others (1979)
by Reidel and Fecht (1987). Natural remanent magnetization indicated by: N=normal, R=reversed,
T=transitional, and E=excursion.
cf. REIDEL, S.P. AND FECHT, K.R. 1986. THE HUNTZIGER
FLOW: evidence of surface mixing of The Columbia
River Basalt and its petrogenetic implications.
Geol. Soc. Amer. Bull. 98: 664-672.