Along‐Margin Variations in Breakup Volcanism at the Eastern North American Margin. Issue 12 (26th November 2020)

• Record Type: Journal Article
• Authors: Greene, John A.; Tominaga, Masako; Miller, Nathaniel C.
• Is Part Of: Journal of geophysical research. Volume 125:Issue 12(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-11-26
• Subjects: ENAM -- rifted margin -- breakup magmatism -- magnetic modeling -- continental breakup -- Atlantic Ocean; Geomagnetism -- Periodicals; Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 551.1
• DOI: 10.1029/2020JB020040
• Languages: English
• ISSNs: 2169-9313

Abstract

Abstract: We model the magnetic signature of rift‐related volcanism to understand the distribution and volume of magmatic activity that occurred during the breakup of Pangaea and early Atlantic opening at the Eastern North American Margin (ENAM). Along‐strike variations in the amplitude and character of the prominent East Coast Magnetic Anomaly (ECMA) suggest that the emplacement of the volcanic layers producing this anomaly similarly varied along the margin. We use three‐dimensional magnetic forward modeling constrained by seismic interpretations to identify along‐margin variations in volcanic thickness and width that can explain the observed amplitude and character of the ECMA. Our model results suggest that the ECMA is produced by a combination of both first‐order (~600–1, 000 km) and second‐order (~50–100 km) magmatic segmentation. The first‐order magmatic segmentation could have resulted from preexisting variations in crustal thickness and rheology developed during the tectonic amalgamation of Pangaea. The second‐order magmatic segmentation developed during continental breakup and likely influenced the segmentation and transform fault spacing of the initial, and modern, Mid‐Atlantic Ridge. These variations in magmatism show how extension and thermal weakening was distributed at the ENAM during continental breakup and how this breakup magmatism was related to both previous and subsequent Wilson cycle stages. Key Points: Variations in the East Coast Magnetic Anomaly indicate coincident variations in the breakup volcanics at the Eastern North American Margin Modeling suggests that the East Coast Magnetic Anomaly is produced by first‐order (~600–1, 000 km) and second‐order (~50–100 km) magmatic segmentation Second‐order magmatic segmentation during breakup likely influenced the segmentation and transform fault spacing of the Mid‐Atlantic Ridge