Magnetic anomaly map of North America

Bankey, Viki; Cuevas, Alejandro; Daniels, David L.; Finn, Carol A.; Hernández, Israel; Hill, Patricia L.; Kucks, R.P.; Miles, W; Pilkington, Mark; Roberts, Carter W.; Roest, W. R.; Rystrom, V.L.; Shearer, Sarah; Snyder, Stephen L.; Sweeney, Ronald E.; Vélez, Julio César Barrera

doi:10.3133/70211067

Cited by 9 publications

(6 citation statements)

References 2 publications

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“…(1967) (which closely follows magnetic anomaly peaks of the North American magnetic anomaly map created by Bankey et al. (2002)) to 1 km. Based on these magnetic anomaly picks, we estimate the strikes and standard deviations of abyssal‐hill faults that may be reactivated during slab bending in 1° wide bins using four distinct anomalies in the study area (Figures 2c and 3).…”

Section: Methodssupporting

confidence: 73%

“…Rupture patches are shown on the overriding plate with colors matching those shown in Figure 1. (c) Mapped bending‐related faults (thin black lines) overlain on a magnetic anomaly grid (Bankey et al., 2002). Note the rotation in the spreading direction from N‐S west of ∼156°W to E‐W east of ∼156°W.…”

Section: Methodsmentioning

confidence: 99%

“…Elvers et al (1967) map isochrons in detail on the subducting Pacific plate in our study area. To estimate the likely orientation of pre-existing faults in our study area, we resample picks made by Elvers et al (1967) (which closely follows magnetic anomaly peaks of the North American magnetic anomaly map created by Bankey et al (2002)) to 1 km. Based on these magnetic anomaly picks, we estimate the strikes and standard deviations of abyssal-hill faults that may be reactivated during slab bending in 1°wide bins using four distinct anomalies in the study area (Figures 2c and 3).…”

Section: Estimating Strikes Of Pre-existing Structures From Magnetic ...mentioning

confidence: 99%

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Controls on Bending‐Related Faulting Offshore of the Alaska Peninsula

Clarke,

Shillington,

Regalla

et al. 2024

Geochem Geophys Geosyst

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Oceanic plates experience extensive normal faulting as they bend and subduct, enabling fracturing of the incoming lithosphere. Debate remains about the relative importance of pre‐existing faults, plate curvature and other factors controlling the extent and style of bending‐related faulting. The subduction zone off the Alaska Peninsula is an ideal place to investigate controls on bending faulting as the orientation of the abyssal‐hill fabric with respect to the trench and plate curvature vary along the margin. Here, we characterize faulting between longitudes 161°W and 155°W using newly collected multibeam bathymetry data. We also use a compilation of seismic reflection data to constrain patterns of sediment thickness on the incoming plate. Although sediment thickness increases over 1 km from 156°W to 160°W, most sediments were deposited prior to the onset of bending faulting and thus should have limited impact on the expression of bend‐related fault strikes and throws in bathymetry data. Where magnetic anomalies trend subparallel to the trench (<30°) west of ∼156°W, bending faults parallel magnetic anomalies, implying that bending faults reactivate pre‐existing structures. Where magnetic anomalies are highly oblique (>30°) to the trench east of 156°W, no bending faults are observed. Summed fault throws increase to the west, including where pre‐existing structure orientations are constant (between 157 and 161°W), suggesting that another factor such as the increase in slab curvature must influence bending faulting. However, the westward increase in summed fault throws is more abrupt than expected for gradual changes in slab bending alone, suggesting potential feedbacks between pre‐existing structures, slab dip, and faulting.

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Section: Methodssupporting

confidence: 73%

Section: Methodsmentioning

confidence: 99%

Section: Estimating Strikes Of Pre-existing Structures From Magnetic ...mentioning

confidence: 99%

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Controls on Bending‐Related Faulting Offshore of the Alaska Peninsula

Clarke,

Shillington,

Regalla

et al. 2024

Geochem Geophys Geosyst

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“…Only faults with minimum scarps of ±5 m in the detrended grid are included in this mapping effort. (Bankey et al, 2002). Note the rotation in spreading direction from N-S west of ~156ºW to E-W east of ~156ºW.…”

Section: Characterizing Bending Faulting In Bathymetry Datamentioning

confidence: 99%

Controls on Bending-Related Faulting Offshore of the Alaska Peninsula

Clarke,

Shillington,

Christine

et al. 2023

Preprint

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Oceanic plates experience extensive normal faulting as they bend and subduct, enabling fracturing of the crust and upper mantle. Debate remains about the relative importance of pre-existing faults, plate curvature and other factors in controlling the extent and style of bending-related faulting. The subduction zone off the Alaska Peninsula is an ideal place to investigate controls on bending-related faulting as the orientation of abyssal-hill fabric with respect to the trench and plate curvature vary along the margin. Here we characterize bending faulting between longitudes 161°W and 155ºW using newly collected multibeam bathymetry data. We also use a compilation of seismic reflection data to constrain patterns of sediment thickness on the incoming plate. Although sediment thickness increases by over 1 km from 156°W to 160°W, most sediments were deposited prior to the onset of bending faulting and thus have limited impact on the expression of bend-related fault strikes and throws in bathymetry data. Where magnetic anomalies trend subparallel to the trench (<30°) west of ~156ºW, bending faulting parallels magnetic anomalies, implying bending faulting reactivates pre-existing structures. Where magnetic anomalies are highly oblique (>30°) to the trench east of 156ºW, no bending faulting is observed. Summed fault throws increase to the west, including where pre-existing structure orientations do not vary between 157-161ºW, suggesting that the increase in slab curvature directly influences fault throws. However, the westward increase in summed fault throws is more abrupt than expected for changes in slab bending alone, suggesting potential feedbacks between pre-existing structures, slab dip, and faulting.

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“…Second, crustal temperatures can be estimated from the depth to where crustal rocks reach their Curie temperature and become largely nonmagnetic, using spectral analyses of aeromagnetic data. The boundary between the North American Cordillera hot backarc and the adjacent cratonic regions is generally well defined by the spatial wavelength and character of the magnetic variations (Figure 12) (e.g., Bankey et al., 2002; Geological Survey of Canada, 2020). In northwestern Canada, the Cordillera backarc has generally shorter wavelength variations, from some combination of small scale magnetic mafic oceanic and arc terranes, and from the magnetization thermal limit being shallower (e.g.,Cook et al., 2004, 2005; Lynn et al., 2005; Pilkington & Saltus, 2009; Saltus & Hudson, 2007).…”

Section: Magnetic and Gravity Definition Of The Hot Backarcmentioning

confidence: 99%

The Thermal Regime of NW Canada and Alaska, and Tectonic and Seismicity Consequences

Hyndman

2023

Geochem Geophys Geosyst

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NW Canada and Alaska are the continuation of the North American Cordillera through Mexico, western USA and western Canada. I show that they have similar thermal regimes and thermal control of tectonics and seismicity. I first summarize the multiple constraints to crust and upper mantle temperatures and then discuss some consequences. There are bimodal crust and upper mantle temperatures characteristic of most subduction zones: cool forearc, uniformly hot backarc (Yukon Composite Terrane to Southern Brooks Range, and Mackenzie Mountains), and stable cratonic backstops (Arctic Alaska Terrane and Canadian Shield). The main constraints are as follows: (a) Heat flow measurements, (b) Temperature‐dependent upper mantle velocities and seismic attenuation, (c) Temperature‐dependent topographic elevations; thermal isostasy, (d) Depth and temperature of the seismic lithosphere‐asthenosphere boundary (LAB), (e) Origin temperature and depth of craton kimberlite xenoliths, (f) Geochemically inferred source temperature and depth of recent volcanic rocks. (g) Depth to the magnetic Curie temperature, (h) Depth extent of seismicity. The backarc lithosphere is thin, LAB at 50–85 km and ∼1,350°C ± 25°C. Moho temperatures at 35 km are 850°C ± 100°C compared to cool cratonic areas of 400°C–500°C. The consequences include the following: (a) Thin and weak backarc lithosphere that accommodates pervasive tectonic deformation indicated by wide‐spread seismicity and GPS‐defined motions, in contrast to the stable cratonic regions; (b) Weak backarc lower crust that flattens the Moho and allows detachment and thrusting of the upper crust over the cold strong Arctic Alaska Terrane and Canadian Shield. This article provides a model for how to estimate deep temperatures from multiple constraints.

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Magnetic anomaly map of North America

Cited by 9 publications

References 2 publications

Controls on Bending‐Related Faulting Offshore of the Alaska Peninsula

Controls on Bending‐Related Faulting Offshore of the Alaska Peninsula

Controls on Bending-Related Faulting Offshore of the Alaska Peninsula

The Thermal Regime of NW Canada and Alaska, and Tectonic and Seismicity Consequences

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