Peculiarities of roughness and thickness of oceanic crust in the Eurasian Basin, Arctic Ocean

Abstract

Summary The Gakkel Ridge, northern boundary of the American and Eurasian plates, has the slowest spreading rate of the global ridge system. Therefore, it provides an excellent opportunity to study any dependence of crustal fabric on spreading rate. Two parameters, crustal surface roughness and crustal thickness, at the super‐slow‐spreading Gakkel Ridge (< 20 mm yr−1 full rate) are the subject of the following study. Seismic and gravity data acquired across the Gakkel Ridge and the adjacent Nansen and Amundsen basins during the ARCTIC'91 expedition are used. The surface of the basement, imaged along the seismic multichannel profiles, is very rough and varies in its topography from several hundreds of metres up to 1000 m. Its RMS‐roughness ranges from 450 m in the central Amundsen Basin to 584 m in the southern Eurasian Basin. These values agree reasonably well with RMS‐roughness values derived by an empirical model from spreading rates. The gravity models reveal a 5–6 km thick oceanic crust (density of 2900 kg m−3) in the central part of the Amundsen Basin, increasing to 9 km towards the Gakkel Ridge. At the southwestern end of the Eurasian Basin, the oceanic crust is only 2–5 km thick and thickens towards the Gakkel Ridge. In our model the ridge is composed of a 2 km thick upper layer with a density of 2600 kg m−3, underlain by an 8 km thick zone with a density of 2900 kg m−3. The increase of crustal thickness does not confirm theoretical models for the relation between spreading rate and crustal thickness. The results indicate that the super‐slow spreading rate of the Gakkel Ridge may have caused lateral variations in the crustal thickness of the Eurasian Basin.

Expanding the Cenozoic paleoceanographic record in the Central Arctic Ocean: IODP Expedition 302 Synthesis

“…O'Regan et al [79] show that basinwide compression occurred in two stages: the first phase was caused by a northward movement of the Greenland micro-plate during Eocene times and terminated when Greenland joined the North American plate during Chron C13 [14,81]; The second phase occurred along the Laptev Sea margin and was initiated by plate re-organization during Chron C13. This lasted until Chron C6 at about 19 Ma and resulted in the structural evidence observed on the New Siberian Islands and the northern Verkhoyansk Range, as well as the prominent hiatuses on the Laptev and Siberian shelves [82][83][84]. O'Regan et al [79] argue that the end of the long lasting (56-19 Ma) basin-wide compression occurred shortly prior to, or in conjunction with, the observed onset of early Miocene subsidence of the Lomonosov Ridge, thus permitting post-rifting lithospheric thermal cooling to begin.…”

“…The Amerasian Basin was the only deep basin in the Arctic Ocean for about [80][81][82][83][84][85][86][87][88][89][90] Myr. The Lomonosov Ridge separates the older Amerasian Basin from the younger Eurasian Basin (Figure 1).…”

Subsidence and crustal roughness of ultra-slow spreading ridges in the northern North Atlantic and the Arctic Ocean

“…With exception of the roughness value for the northwestern part of profile 20020500, all new roughness values worked on for the Fram Strait and the Arctic Ocean, including the ones by Weigelt & Jokat (2001), lie above the Malinverno (1991) curve fit. The roughness values of Bird & Pockalny (1994) are generally higher than the rms roughness data of Malinverno (1991) at ultra‐slow spreading rates (<20 mm y −1 ) but similar at intermediate rates (21–40 mm y −1 ).…”

“…In Fig. 6, published roughness values (Ranero et al 1970; Goff 1991, 1997; Bird & Pockalny 1994; Henstock & White 1996; Minshull 1999; Weigelt & Jokat 2001) are shown in a global context, highlighting the relationship between crustal roughness and half spreading rates. The new roughness values supplement the global data for the ultra‐slow end of the spectrum.…”

Evaluation and modelling of Tertiary source rocks in the central Arctic Ocean

“…Estimated sediment thicknesses vary between 0 and 4.5 km for the Nansen Basin and 1.7-2.0 km for the Amundsen Basin (Jokat and Micksch, 2004). Crustal thicknesses of the basins are estimated to range from 3 to 6 km by Weigelt and Jokat (2001).…”