The Tillamook map area crosses a broad, northeast-plunging structural arch in Tertiary volcanic and sedimentary strata that form the northern Oregon Coast Range (Figure 1). The core of the uplift consists of Eocene basalt and interbedded marine strata which were previously correlated with the Siletz River Volcanics of the central Oregon Coast Range (Wells and Peck, 1961). In this study, the Eocene volcanics have been divided into five units, and a distinction is made between the lower Eocene Siletz River Volcanics and the overlying Tillamook Volcanics of late middle Eocene age. Marine mudstone and sandstone are interbedded with all of the volcanic units and comprise most of the late Eocene to Miocene stratigraphic section which forms the flanks of the Coast Range uplift. Continental shelf and slope sequences predominate in the basins flanking the Coast Range uplift."
Geologic Map of the Tillamook Highlands, Northwest Oregon Coast Range (Tillamook, Nehalem, Enright, Timber, Fairdale, and Blaine15 minute Quadrangles)
by Ray E. Wells1, Parke D. Snavely, Jr1, N. S. MacLeod2, Michael M. Kelly3, and Michael J. Parker4 Open File Report 94-21 1994
NEH_GEO.PAT COLUMN ITEM NAME WIDTH OUTPUT TYPE N.DEC 1 AREA 4 12 F 3 5 PERIMETER 4 12 F 3 9 NEH_GEO# 4 5 B - 13 NEH_GEO-ID 4 5 B - 17 PTYPE 35 35 C - NEH_GEO.AAT COLUMN ITEM NAME WIDTH OUTPUT TYPE N.DEC 1 FNODE# 4 5 B - 5 TNODE# 4 5 B - 9 LPOLY# 4 5 B - 13 RPOLY# 4 5 B - 17 LENGTH 4 12 F 3 21 NEH_GEO# 4 5 B - 25 NEH_GEO-ID 4 5 B - 29 LTYPE 35 35 C - NEH_GEO.NAT COLUMN ITEM NAME WIDTH OUTPUT TYPE N.DEC 1 ARC# 4 5 B - 5 NEH_GEO# 4 5 B - 9 NEH_GEO-ID 4 5 B - 13 NODE_ID 4 5 B - LTYPE 'contact, approx. located' 'contact, certain' 'contact, concealed' 'contact, concealed, queried' 'contact, inferred, queried' 'dike, Tib' 'dike, Tis' 'fault, approx. located' 'fault, certain' 'fault, concealed' 'fault, concealed, queried' 'fault, inferred, queried' 'map boundary, certain' 'thrust fault, approx. located' 'thrust fault, certain' 'water boundary, certain'