The role of mantle melts in the transition from rifting to seafloor spreading offshore eastern North America

Shuck, Brandon; Avendonk, H. J. Van; Bécel, A.

doi:10.1016/j.epsl.2019.115756

Cited by 31 publications

(120 citation statements)

References 45 publications

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“…In addition, if there was a ridge jump, we would expect differences in basement structure and internal reflectivity between the BSMA and igneous crust farther seaward. However, the continuity of the top basement and Moho reflections as noted by Shuck et al (2019) and intracrustal reflectivity between the BSMA crust and crust farther seaward do not indicate any discontinuity and would thus be in agreement with the BSMA crust representing the earliest steady state oceanic crust.…”

Section: Blake Spur Crust and Oceanic Crust Seaward: Steady-state Seamentioning

confidence: 65%

“…The ECMA was commonly thought to represent the Continent/Ocean transition, which implied that normal oceanic crust formed along an incipient mid-ocean ridge to the east (Alsop & Talwani, 1984). However, the recent study of Shuck et al (2019) suggests that this transition occurs at the BSMA, 200 km farther seaward than the ECMA (Figure 1). It is unclear whether or not CAMP magmatism triggered continental breakup as the exact temporal relationships between CAMP magmatism, and the offshore volcanic rocks remain unclear (e.g., McHone, 2000;Schlische, 2003).…”

Section: Journal Of Geophysical Research: Solid Earthmentioning

confidence: 99%

“…For seismic wavespeeds exceeding 7.2 km/s, we used the velocity-density relationship for diabase, gabbro, and eclogite of Birch (1961) to account for the high mafic content in the lower crust. Parts of the crustal model that were not well imaged by refraction data (Shuck et al, 2019) may be further constrained by gravity modeling. For Line 1, we used 25 homogeneous density blocks or layers to predict the main trend of the gravity anomaly along the profile.…”

Section: 1029/2020jb020093mentioning

confidence: 99%

“…In the seismic reflection image, the Moho is interpreted as a continuous low frequency reflection at the base of the reflective lower crust, and it exhibits more structure than the crust-mantle boundary inferred from the ENAM seismic refraction data (Shuck et al, 2019), which involved a smoothed tomographic inversion.…”

Section: Crustal Structurementioning

confidence: 99%

“…The mantle lithospheric lid could either be oceanic or continental as its nature would not have a major difference in terms of the observed structures of the proto-oceanic domain (i.e., roughness, thickness, and/or seismic velocities). However, the relatively hot mantle (~1420°C) conditions inferred at the time of the ECMA (Shuck et al, 2019) would likely prevent the presence of a significant oceanic lithospheric lid in the proto-oceanic domain. Recent independent estimates of the mantle potential temperature for the CAMP source, based on olivine compositions of CAMP lavas, range between 1430°C and 1480°C (Callegaro et al, 2013;Herzberg & Gazel, 2009;Whalen et al, 2015).…”

Section: Journal Of Geophysical Research: Solid Earthmentioning

confidence: 99%

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Evidence for a Prolonged Continental Breakup Resulting From Slow Extension Rates at the Eastern North American Volcanic Rifted Margin

et al. 2020

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When continental rifting is accompanied by localized magmatism under extensional stress, the breakup duration can be short and the continent/ocean transition sharp, as mantle melts are thought to be efficient at heating and weakening the lithosphere. This mode of rifting has been invoked for the Eastern North American Margin (ENAM) based on the existing geophysical data. Here, we present results from multichannel seismic profiles from the ENAM Community Seismic Experiment offshore North Carolina, U.S. Our survey area encompasses both the East Coast Magnetic Anomaly (ECMA) and the Blake Spur Magnetic Anomaly (BSMA), which lies~200-km farther seaward. Our prestack depth-migrated seismic images reveal major changes in the structure of the igneous crust across the BSMA. Between the ECMA and BSMA, we image a proto-oceanic domain of rough, faulted, and thin igneous crust. The roughness of this oceanic crust is similar to modern ultraslow spreading environments which involve the continued presence of a pre-existing lithospheric lid. Seaward of the BSMA the basement is smooth, and the crust is relatively thick, which is typical for Jurassic oceanic crust. Across the BSMA, we image a step up in basement and crustal root, which we interpret to represent complete lithospheric breakup and a transition to steady-state seafloor spreading in agreement with coincident refraction results. Our results would also indicate low extension rates in the final stages of rifting that may have influenced the thermal structure of the lithosphere and could explain the delay for continental breakup. All of these observations show that although continental rifting between eastern North America and northwest Africa was assisted by magmatic activity, it did not lead to rapid localization of extensional strain as previously thought.

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Section: Blake Spur Crust and Oceanic Crust Seaward: Steady-state Seamentioning

confidence: 65%

Section: Journal Of Geophysical Research: Solid Earthmentioning

confidence: 99%

Section: 1029/2020jb020093mentioning

confidence: 99%

Section: Crustal Structurementioning

confidence: 99%

Section: Journal Of Geophysical Research: Solid Earthmentioning

confidence: 99%

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Evidence for a Prolonged Continental Breakup Resulting From Slow Extension Rates at the Eastern North American Volcanic Rifted Margin

et al. 2020

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The role of pre-magmatic rifting in shaping a volcanic continental margin: An example from the Eastern North American Margin

Lang

Hutchinson

Brink

et al. 2020

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Both magmatic and tectonic processes contribute to the formation of volcanic continental margins. Such margins are thought to undergo extension across a narrow zone of lithospheric thinning (~100 km). New observations based on existing and reprocessed data from the Eastern North American Margin contradict this hypothesis. With ~64,000 km of 2-D seismic data tied to 40 wells combined with published refraction, deep reflection, receiver function, and onshore drilling efforts, we quantified along-strike variations in the distribution of rift structures, magmatism, crustal thickness, and early post-rift sedimentation under the shelf of Baltimore Canyon Trough (BCT), Long Island Platform, and Georges Bank Basin (GBB). Results indicate that BCT is narrow (80-120 km) with a sharp basement hinge and few rift basins. The seaward dipping reflectors (SDR) there extend ~50 km seaward of the hinge line. In contrast, the GBB is wide (~200 km), has many syn-rift structures, and the SDR there extend ~200 km seaward of the hinge line. Early post-rift depocenters at the GBB coincide with thinner crust suggesting "uniform" thinning of the entire lithosphere. Models for the formation of volcanic margins do not explain the wide structure of the GBB. We argue that crustal thinning of the BCT was closely associated with late syn-rift magmatism, whereas the broad thinning of the GBB segment predated magmatism. Correlation of these variations to crustal terranes of different compositions suggests that the inherited rheology determined the premagmatic response of the lithosphere to extension.

show abstract

The role of pre-magmatic rifting in shaping a volcanic continental margin: An example from the Eastern North American Margin

Lang

Brink

Hutchinson

et al. 2020

Preprint

View full text Add to dashboard Cite

Both magmatic and tectonic processes contribute to the formation of volcanic continental margins. Such margins are thought to undergo extension across a narrow zone of lithospheric thinning (~100 km). New observations based on existing and reprocessed data from the Eastern North American Margin contradict this hypothesis. With~64,000 km of 2-D seismic data tied to 40 wells combined with published refraction, deep reflection, receiver function, and onshore drilling efforts, we quantified along-strike variations in the distribution of rift structures, magmatism, crustal thickness, and early post-rift sedimentation under the shelf of Baltimore Canyon Trough (BCT), Long Island Platform, and Georges Bank Basin (GBB). Results indicate that BCT is narrow (80-120 km) with a sharp basement hinge and few rift basins. The seaward dipping reflectors (SDR) there extend~50 km seaward of the hinge line. In contrast, the GBB is wide (~200 km), has many syn-rift structures, and the SDR there extend~200 km seaward of the hinge line. Early post-rift depocenters at the GBB coincide with thinner crust suggesting "uniform" thinning of the entire lithosphere. Models for the formation of volcanic margins do not explain the wide structure of the GBB. We argue that crustal thinning of the BCT was closely associated with late syn-rift magmatism, whereas the broad thinning of the GBB segment predated magmatism. Correlation of these variations to crustal terranes of different compositions suggests that the inherited rheology determined the premagmatic response of the lithosphere to extension.

show abstract

The role of mantle melts in the transition from rifting to seafloor spreading offshore eastern North America

Cited by 31 publications

References 45 publications

Evidence for a Prolonged Continental Breakup Resulting From Slow Extension Rates at the Eastern North American Volcanic Rifted Margin

Evidence for a Prolonged Continental Breakup Resulting From Slow Extension Rates at the Eastern North American Volcanic Rifted Margin

The role of pre-magmatic rifting in shaping a volcanic continental margin: An example from the Eastern North American Margin

The role of pre-magmatic rifting in shaping a volcanic continental margin: An example from the Eastern North American Margin

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