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The Portland Basin is a roughly topographic and structural depression in the central Puget-Willamette Lowland.〔Beeson, M.H., Tolan, T.L., and Anderson, J.L., 1989, The Columbia River Basalt Group in Western Oregon; Geologic Structures and other Factors that Controlled Flow Emplacement Patterns, in Reidel, S.P. and Hooper, P.R., eds., Volcanism and tectonism in the Columbia River flood-basalt province, Geologic Society of America Special Paper 239, p223-246〕 The Portland Basin is approximately long and wide, with its long axis oriented northwest.〔Evarts, Russell C., 2004, Geologic Map of the Ridgefield Quadrangle, Clark and Cowlitz Counties, Washington, U.S. Geological Survey〕 Studies indicate that as much as of late Miocene and younger sediments have accumulated in the deepest part of the basin near Vancouver. Most of the basin-fill material was carried in from the east by the Columbia River.〔Liberty, L.M., Hemphill-Haley, M.A., and Madin, I.P., 2003, The Portland Hills Fault –uncovering a hidden fault in Portland, Oregon using high-resolution geophysical methods, Tectonphysics, v.368. p. 89-103〕 ==References== 〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Portland Basin (geology)」の詳細全文を読む スポンサード リンク
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