Seismic structure of the St. Paul Fracture Zone and Late Cretaceous to Mid Eocene oceanic crust in the equatorial Atlantic Ocean near 18°W

Abstract

 Seismic structure along the St. Paul fracture zone reflects magmatically accreted oceanic crust  Oceanic crust across St. Paul shows only small thickness variations, lacking evidence for regional crustal thinning near fracture zones  Magmatic nature of crust supports a mechanism where transform crust is augmented before being turned into a fracture zone

Seismic Crustal Structure and Morphotectonic Features Associated With the Chain Fracture Zone and Their Role in the Evolution of the Equatorial Atlantic Region

“…Based on the location of the seismic profiles presented in the literature, we made a compilation separating the results obtained for the FZ and TF domains. In Figure 11, we show the resulting crustal thicknesses mapped at different TFs and FZs (including this study, i.e., the Chain FZ, and the preliminary result for the St. Paul FZ reported by Growe et al, 2019) offsetting slow‐spreading centers. Also, we add crustal thickness detected at a number of NTOs (Canales et al, 2000; Dannowski et al, 2018; Davy et al, 2020; Detrick et al, 1993; Dunn et al, 2017; Hooft et al, 2000; Kahle et al, 2016) to enable potential comparison with the crustal thickness obtained across the pseudofault formed by the ridge propagation.…”

“…For the cases where the range of crustal thickness was reported, the range is indicated by error bars and the average crustal thickness is indicated in the corresponding symbol. The vertical dashed line indicates interruption in horizontal axis to show the crustal thickness for the St. Paul FZ (Growe et al, 2019) displaying a cumulative offset of 630 km (e.g., Maia et al, 2016). The IFP and OFP stand for inner and outer pseudofaults, respectively, from Dannowski et al (2018).…”

“…This active‐source seismic survey was followed by a passive seismic experiment Pi‐LAB (Harmon et al, 2018) recording the earthquake activity within the region focused around and north of the Chain TF for the period of 1 yr (2016–2017). In addition, two active‐source seismic refraction surveys were conducted: LITHOS in 2017 (Grevemeyer et al, 2019; Growe et al, 2019; Vaddineni et al, 2019) and ILAB‐St. Paul Romanche and Chain (ILAB‐SPARC) in 2018 (Gregory et al, 2020; Marjanović et al, 2019).…”