TY - DATA AB - The Portland and Tualatin basins are part of the Puget-Willamette Lowland in the Cascadia forearc of Oregon and Washington. The Coast Range to the west has undergone Paleogene transtension and Neogene transpression, which is reflected in basin stratigraphy. To better understand the tectonic evolution of the region, Darby Scanlon modeled three key stratigraphic horizons and their associated depocenters (areas of maximum sediment accumulation) through space and time using well log, seismic, outcrop, aeromagnetic, and gravity data. Three isochore maps were created to constrain the location of Portland and Tualatin basin depocenters during 1) Pleistocene to mid-Miocene (0-15 Ma), 2) eruption of the Columbia River Basalt Group (CRBG, 15.5-16.5 Ma), and 3) MidMiocene to late Eocene time (~17-35 Ma). Results show that the two basins each have distinct mid-Miocene to Pleistocene depocenters. The depth to CRBG in the Portland basin reaches a maximum of ~1,640 ft, 160 ft deeper than the Tualatin basin. Although the Portland basin is separated from the Tualatin basin by the Portland Hills, inversion of gravity data suggests that the two were connected as one continuous basin prior to CRBG deposition. Local thickening of CRBG flows over a gravity low coincident with the Portland Hills suggests that Neogene transpression in the forearc reactivated the SylvanOatfield and Portland Hills faults as high angle reverse faults. This structural inversion separated the once continuous Portland and Tualatin basins in the mid-late Miocene. A change in the stress regime at that time marks the transition from Paleogene forearc extension to deformation dominated by north-south shortening due to collision of the forearc against the Canadian Coast Mountains. An eastward shift of the forearc basin ii depocenter over the Neogene likely reflects uplift of the Coast Range to the west. A change in regional stress in the mid to late-Miocene, along with uplift of the Oregon Coast Range, caused a 10-fold decrease in sediment accumulation rates across the Portland and Tualatin basins. Transpressional oblique-slip faulting continues to deform the region as the forearc undergoes clockwise rotation and collides with the rigid Canadian Coast Mountains to the north. AU - Scanlon, Darby DB - Open Energy Data Initiative (OEDI) DP - Open EI | National Renewable Energy Laboratory DO - KW - geothermal KW - energy KW - tetonic eveolution KW - isochore maps KW - modeling KW - top crbg KW - eocene basement KW - paleogene KW - neogene KW - resource assement KW - spatial KW - temporal KW - portland KW - tualatin basin KW - oregon KW - geophysics KW - geophysical KW - geothermal exploration LA - English DA - 2019/07/29 PY - 2019 PB - Portland State University T1 - Portland DDU Feasibility Study: The Spatial and Temporal Evolution of the Portland and Tualatin Basins, Oregon, USA UR - https://data.openei.org/submissions/ ER -