Multibeam investigation of the active North Atlantic plate boundary reorganization tip

Abstract

The previous orthogonal ridge/transform staircase geometry south of Iceland is being progressively changed to the present continuous oblique Reykjanes Ridge spreading geometry as North America-Eurasia transform faults are successively eliminated from north to south. This reorganization is commonly interpreted as a thermal phenomenon, caused by warmer Iceland plume mantle progressively interacting with the ridge, although other diachronous seafloor spreading reorganizations are thought to result from tectonic rift propagation. New marine geophysical data covering our reinterpretation of the reorganization tip near 57°N show successive transform eliminations at a propagation velocity of ~110 km/Myr, ten times the spreading half rate, followed by abrupt reorganization slowing at the Modred transform as it was converted to a migrating non-transform offset. Neither the simple thermal model nor the simple propagating rift model appears adequate to explain the complicated plate boundary reorganization process.

Polyphase Magmatism During the Formation of the Northern East Greenland Continental Margin

“…If the COT is located at the northern East Greenland continental slope, as we propose, the magnetic seafloor spreading anomalies in the oceanic domain terminate against the continental slope, supporting a southward propagating seafloor spreading system in the Greenland Sea (Koopmann et al, ; Voss et al, ). During propagating, the active spreading ridge is offset laterally from the ridge it replaces (Hey et al, ). Thus, propagating seafloor spreading is expected to produce asymmetric patterns and the pinch‐out of oceanic spreading anomalies against the continental margin.…”

“…Research vessel Maria S. Merian's three compressors provided the working pressure of 2,172 psi (150 bar). Table 1 Magmatic and Tectonic Events According to 1 (Abdelmalak, Meyer, et al, 2016), 2 (Storey et al, 2007), 3 (Price et al, 1997), 4 , 5 ), 6 (Tegner et al, 2008, 7 (Mosar et al, 2002), 8 (Hey et al, 2016), 9 (Horni et al, 2017, 10 (Larsen et al, 2013), and 11 Tectonics Impact on the marine fauna was kept to a minimum following the strict regulations that were monitored by two dedicated marine mammal observers and supported by the scientific crew.…”

Tectonic Control of the Theistareykir Geothermal Field by Rift and Transform Zones in North Iceland: A Multidisciplinary Approach

“…Complexities arise in identifying and differentiating some of the fracture sets in areas under the combined influence of rift and transform zones and even within oblique rifting. Examples of those structural features are complex fracture patterns as in Afar [1] [18], Djibouti [19] [20], East African [21] and the Kenyan Rifts [22], and Iceland [23] [24] [25] [26]; pull-aparts on strike-slips [6] [27] [28]; V-shaped ridge and pseudo-faults observed on Iceland shelf [29] [30] and even suggested for onland rift segments in Iceland [31]; en échelon geometry and fracture sinuosity [32] particularly under oblique extension along rift segments [33] [34] [35] such as in Ethiopia [36], Taupo of New Zealand [6] [37] [38] [39] [40], Iceland shelf [13] [41] [42] and in Iceland [43], or oblique extension along a single fracture during dyke injection [44] [45]; stress rotation as in East African Rifts and Gulf of Aden [46] [47] [48] [49].…”

Causes and Consequences of Diachronous V‐Shaped Ridges in the North Atlantic Ocean

“…Recently, two alternative hypotheses for the formation of VSRs have been put forward. The first hypothesis suggests that VSRs are generated by rift propagation, obviating the need for thermally or compositionally generated melt anomalies (Figure b; Benediktsdóttir et al, ; Briais & Rabinowicz, ; Hey et al, , ). A sequence of propagating rifts and transform faults are envisaged, leading to asymmetric accretion along the ridge axis.…”