The thermal environment of Cascadia Basin

• Published in: Geochemistry, geophysics, geosystems : G3 Vol. 13; no. 7; pp. np - n/a
• Main Authors: Johnson, H. Paul, Hautala, Susan L., Bjorklund, Tor A.
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 01.07.2012; John Wiley & Sons, Inc
• Subjects: Basins; Cascadia; Combined water; Continental margins; Flow measurement; Heat; Heat flow; Igneous rocks; Ocean floor; Oceanic crust; Physical properties; Sediments; subduction; Water column; INE, Pacific, Cascadia Subduction Zone; INE, Pacific, Juan de Fuca Ridge; INE, Canada, British Columbia, Vancouver I; INE, Pacific, Cascadia Basin
• ISSN: 1525-2027; 1525-2027
• DOI: 10.1029/2011GC003922

Located adjacent to the NE Pacific convergent boundary, Cascadia Basin has a global impact well beyond its small geographic size. Composed of young oceanic crust formed at the Juan de Fuca Ridge, igneous rocks underlying the basin are partially insulated from cooling of their initial heat of formation by a thick layer of pelagic and turbidite sediments derived from the adjacent North American margin. The igneous seafloor is eventually consumed at the Cascadia subduction zone, where interactions between the approaching oceanic crust and the North American continental margin are partially controlled by the thermal environment. Within Cascadia Basin, basement topographic relief varies dramatically, and sediments have a wide range of thickness and physical properties. This variation produces regional differences in heat flow and basement temperatures for seafloor even of similar age. Previous studies proposed a north‐south thermal gradient within Cascadia Basin, with high geothermal flux and crustal temperatures measured in the heavily sedimented northern portion near Vancouver Island and lower than average heat flux and basement temperatures predicted for the central and southern portions of the basin. If confirmed, this prediction has implications for processes associated with the Cascadia subduction zone, including the location of the “locked zone” of the megathrust fault. Although existing archival geophysical data in the central and southern basin are sparse, nonuniformly distributed, and derived from a wide range of historical sources, a substantial N‐S geothermal gradient appears to be confirmed by our present compilation of combined water column and heat flow measurements. Key Points There is a large gradient in basement temperature in Cascadia Basin This gradient in temperature can impact subduction processes Postglacial turbidites can impact thermal history of ocean plates