Transition from slab to slabless: Results from the 1993 Mendocino triple junction seismic experiment

Beaudoin, B. C.; Godfrey, Nicola J.; Klemperer, S. L.; Lendl, Christof; Tréhu, Anne M.; Henstock, T.; Levander, A.; Holl, James E.; Meltzer, A.; Luetger, James H.; Mooney, Walter D.

doi:10.1130/0091-7613(1996)024<0195:tfstsr>2.3.co;2

Cited by 52 publications

(43 citation statements)

References 20 publications

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“…Vergence direction is obscured by slump debris from 43øN and 44øN, but a seaward vergent basal thrust is observed cutting through older slump debris between 42øN to 43øN [Goldfinger et al, 1999]. South of 42øN, where the Siletz terrane is absent and the crystalline backstop of the Klamath terrane forms a landward dipping backstop [Beaudoin et al, 1996], vergence appears to be mixed [Gulick et al, 1998]. These changes in vergence at the deformation front have been previously attributed to differences in pore pressure on the decollement resulting from differences in the thickness and composition of sediments on the subducting plate.…”

Section: Demagnetization Of Juan De Fuca Plate Crustmentioning

confidence: 87%

Crustal structure beneath the central Oregon convergent margin from potential‐field modeling: Evidence for a buried basement ridge in local contact with a seaward dipping backstop

Fleming¹,

Tréhu²

1999

J. Geophys. Res.

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Abstract. Models of magnetic and gravity anomalies along two E-W transects offshore central Oregon, one of which is coincident with a detailed velocity model, provide quantitative limits on the structure of the subducting oceanic crust and the crystalline backstop. The models indicate that the backstop-forming western edge of the Siletz terrane, an oceanic plateau that was accreted to North America-50 million years ago, has a seaward dip of less than 60ø3. Seismic, magnetic, and gravity data are compatible with no more than 2 km of subducted sediments between the Siletz terrane and the underlying crystalline crust of the Juan de Fuca plate. The data also suggest the presence of a N-S trending, 200-km-long basaltic ridge buried beneath the accretionary complex from about 43øN to 45øN. Although the height and width of this ridge probably vary along strike, it may be up to 4 km high and several kilometers wide in places and appears to be locally in contact with the Siletz terrane beneath Heceta Bank. Several models for the origin of this ridge are discussed. These include: a sliver of Siletz terrane detached from the main Siletz terrane during a late Eocene episode of strike-slip faulting; imbrication and thickening of subducted oceanic crust in place; an aseismic ridge rafted in on the subducting oceanic crust during the past 1.2 million years; and a series of ridges and/or seamounts rafted in over a longer period of time and transferred from the subducting plate to the overlying plate. The last model is the most consistent with the complicated history of local uplift, subsidence, and slope instability recorded in the ridges, basins, and banks of this part of the margin. We speculate that the massive seaward dipping western edge of the Siletz terrane in this region inhibits subduction of seamounts and sediments, resulting in fomation of buried ridge as the accumulated flotsam and jetsom of subduction. This process may also be responsible for thickening of lower accretionary complex material, oversteepening of slopes leading to massive slumping, and north-south extension through strike-slip faulting in the accretionary complex to the west of the buried ridge. Regardless of its origin, the ridge may currently be acting as an asperity inhibiting subduction.

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Section: Demagnetization Of Juan De Fuca Plate Crustmentioning

confidence: 87%

Crustal structure beneath the central Oregon convergent margin from potential‐field modeling: Evidence for a buried basement ridge in local contact with a seaward dipping backstop

Fleming¹,

Tréhu²

1999

J. Geophys. Res.

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“…To the south, where the plate margin transitions from a subduction zone to a strike-slip fault, the North American crust thins in the area of the slab window to the south of the Mendocino Triple Junction zone (Hole et al, 2000). On the Pacifi c plate, to the west of the San Andreas fault, is crust that is thinner than that found on the North American plate to the south of the triple junction (Verdonck and Zandt, 1994;Beaudoin et al, 1996).…”

Section: Previous Investigationsmentioning

confidence: 97%

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Gilbert

2012

Geosphere

115

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“…Map summarizing topography, heat flow [Blackwell et al, 1991], and relevant seismic data in the northern Basin and Range Province. Dashed black and white lines indicate COCORP seismic reflection profiles [Allmendinger et al, 1987]; solid black lines indicate PASSCAL experiment [Catchings and Mooney, 1991], Wyoming Ruby profile [Stoerzel and Smithson, 1998], USGS profiles in northern CA [Zucca et al, 1986], Cascadia profiles [Trehu et al, 1994], and Mendocino profiles from Beaudoin et al [1996]. Short dashed black line shows profile of Hill and Pakiser [1976]; long dashed black line shows mine-blast profile of the University of Nevada, Reno [Louie et al, 2004].…”

Section: Pre-40 Ma: East Of the Black Rock Rangementioning

confidence: 99%

Crustal structure of the northwestern Basin and Range Province and its transition to unextended volcanic plateaus

Lerch¹,

Klemperer

Glen

et al. 2007

Geochem Geophys Geosyst

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[1] The northwestern margin of the Basin and Range Province is characterized by a transition from lowmagnitude ($20%) extension in northwestern Nevada to relatively unextended volcanic plateaus in northeastern California. Seismic-velocity and potential-field modeling provides new control on the Mesozoic-to-present tectonic evolution of this poorly understood portion of the U.S. Cordillera. We document $20% crustal thinning associated with Basin and Range extension from a crustal thickness of $37 km under northeastern California to $31 km under northwestern Nevada that is consistent with the amount of extension recorded in the upper crust in northwestern Nevada, suggesting the crustal response to extension was relatively homogeneous over the entire crustal column. Our modeling also shows a welldefined, 80-km-wide zone of unusually low upper-crustal velocities ($5.9-6.1 km/s) that coincide with the surface location of sparse Cretaceous granites, locating the elusive northern extension of the Sierra Nevada batholith through northwestern Nevada for the first time in the subsurface. Combining geological and geophysical data, we reconstruct the late Cretaceous-to-present crustal evolution of this region, documenting an interplay between magmatic addition to the crust, erosional exhumation, sedimentation, and extension that has reversed the direction of crustal thinning from a west-facing continental margin to an east-facing interior basin margin over this time interval. Finally, we find no evidence in northwestern Nevada for unusually thick crust (>40 km) prior to Basin and Range extension.

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Transition from slab to slabless: Results from the 1993 Mendocino triple junction seismic experiment

Cited by 52 publications

References 20 publications

Crustal structure beneath the central Oregon convergent margin from potential‐field modeling: Evidence for a buried basement ridge in local contact with a seaward dipping backstop

Crustal structure beneath the central Oregon convergent margin from potential‐field modeling: Evidence for a buried basement ridge in local contact with a seaward dipping backstop

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Crustal structure of the northwestern Basin and Range Province and its transition to unextended volcanic plateaus

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