Dynamic Topography Development North of Iceland from Subaerial Exposure of the Igneous Logi Ridge, NE Atlantic

Abstract

The Logi Ridge, located north of the West Jan Mayen Fracture Zone, is E-W oriented and 140-150 km long. The seafloor surrounding the Logi Ridge is ∼0.65 km shallower than the conjugate seafloor east of the Mohn's Ridge, attributed to asymmetry in the regional NE Atlantic dynamic uplift. Eight reflection seismic lines across the Logi Ridge constrain its development. Both the western and eastern parts have flat tops, indicating erosion at sea level. Three different basement types surrounding the Logi Ridge are observed: rough basement represents abyssal hills original or reactivated by later magmatic/tectonic events; smooth basement caused by basalt flows overprinting early sediments; and irregular basement formed by later basalt flows and intrusions. The surrounding sediments have two distinct units, where the unit boundary is Middle Miocene (12-14 Ma). Mass transport from the Logi Ridge appears episodically throughout Late Oligocene to Middle Miocene, when development ends. The end of erosion age can also be estimated from seamount height, or present top seamount depth. In the west there is agreement with the age constrained by the sedimentation, proving little dynamic topography change. In the east, discrepancies between the methods are explained by 0.15-0.3 km dynamic uplift after submergence. Hence, most of the regional dynamic uplift occurred before the end of the Logi Ridge development in the Middle Miocene, suggesting a causative relationship. Minor recent magmatic growth and seafloor uplift over a ∼100 km wide zone southeast of the Logi Ridge may be tied to the younger dynamic uplift in the east.

Formation of the Igneous Logi Ridge, NE Atlantic

“…The magma generation rate depends on the duration of the Logi Ridge formation. If building starts at the Eocene/Oligocene boundary at about 35 Ma and is over by the Middle Miocene at around 15 Ma (Tan et al., 2019), the maximum duration is 20 Ma. If the magma generation was evenly distributed over this time interval, then the generation rate becomes approximately 0.02–0.04 m 3 /s.…”

“…Traill Ø is located at the westernmost end of the TIC (Figure 2), where syenitic intrusions exposed onshore are dated to 10.1029/2021JB023891 4 of 24 34-36 Ma, coeval with the rifting of the JMMC (Noble et al, 1988;Price et al, 1997) (Figure 1). Tan et al (2019) found that the onset of formation of the Logi Ridge also started in the Oligocene, and that its formation correlates with a regional dynamic topography rise expected to come from the increasing Iceland Plume influence in the asthenosphere.…”

“…The Logi Ridge is located along the same trend as the TIC on the shelf (Figure 2). The formation of the TIC has been related to the establishment of the WJMFZ during the rifting of the JMMC from Greenland around the Eocene/Oligocene boundary (e.g., Franke et al., 2019; Larsen et al., 2014; Price et al., 1997; Voss & Jokat, 2007), coeval with the start of the Logi Ridge formation (Tan et al., 2019). The results of our study also place the main magmatism to the time of the TIC formation, and a common cause seems likely.…”

“…The Alfred Wegener Institute (AWI) supplied the 2D crustal velocity model AWI20030500, including free‐air ship‐track gravity measurements (Voss & Jokat, 2007). The biggest data set consists of five single‐channel seismic reflection lines (Profiles 2–6) that were collected by the University of Bergen and Oslo, including ship‐track free‐air gravity and echo‐sounder recordings (Tan et al., 2019). In addition, we use one multichannel seismic reflection line (NPD0005) supplied by the Norwegian Petroleum Directorate that covers the eastern Logi Ridge (Figure 2) (Tan et al., 2019).…”

“…(2018), but further include the seismic reflection lines of Tan et al. (2019). These profiles also have recorded ship‐track gravity, and density models of the profiles can be tested by gravity modeling.…”