Sedimentation and subsidence history of the Lomonosov Ridge

Depositional Evolution of the Western Amundsen Basin, Arctic Ocean: Paleoceanographic and Tectonic Implications

“…The cause of nondeposition and/or erosion has been attributed to tectonic uplift, either as a result of mantle phase changes (Minakov & Podladchikov, ) or as a result of the Eurekan orogeny, which reached its peak during the Eocene (Døssing et al, ). Others have related the hiatus to erosion by oceanic bottom currents (Jokat et al, ; Moore and the Expedition 302 Scientists, ), implying that a vigorous circulation system was established in the late Eocene, although this may have happened in combination with tectonic uplift (O'Regan et al, ).…”

Early to middle Eocene history of the Arctic Ocean from Nd‐Sr isotopes in fossil fish debris, Lomonosov Ridge

“…Lomonosov Ridge preserves a history of sedimentation dating back to the Late Cretaceous when it was still joined with continental Eurasia [ Backman et al , 2006; Moore and Expedition 302 Scientists , 2006; O'Regan et al , 2008]. It represents a sliver of thinned and submerged continental crust in the central Arctic Ocean that rifted from continental Eurasia ∼57 million years ago, migrating slowly away via seafloor spreading at the Gakkel Ridge (Figure 1) and accumulating more than 400 m of postrift marine pelagic sediment [ Moran et al , 2006; Moore and Expedition 302 Scientists , 2006; Backman et al , 2006, 2008; Backman and Moran , 2008].…”

“…It represents a sliver of thinned and submerged continental crust in the central Arctic Ocean that rifted from continental Eurasia ∼57 million years ago, migrating slowly away via seafloor spreading at the Gakkel Ridge (Figure 1) and accumulating more than 400 m of postrift marine pelagic sediment [ Moran et al , 2006; Moore and Expedition 302 Scientists , 2006; Backman et al , 2006, 2008; Backman and Moran , 2008]. Four IODP 302 drill sites were cored atop Lomonosov Ridge at ∼1,200 m water depth (Sites M0002 through M0004) near 88°N, resulting in a 428 m composite sedimentary section [ Backman et al , 2008] consisting of the following main lithologic age units, from oldest to youngest: (1) Late Cretaceous shallow marginal marine sediments (ACEX Lithostratigraphic Unit 4), separated by angular unconformity from; (2) a late Paleocene through early and middle Eocene section of variably organic‐rich, sulfide‐bearing, partly microlaminated biosiliceous clay and silty clay (ACEX Lithostratigraphic Units 3 and 2 and Lithostratigraphic Subunit 1/6); (3) a highly condensed, or missing, interval from ∼44 to ∼17.5 Ma; and (4) brown oxidized, silty clays containing abundant ice rafted debris of Neogene age (ACEX Lithostratigraphic Subunits 1/1–1/4) with a transitional subunit (1/5) of Miocene age, all <17.5 Ma [ Expedition 302 Scientists , 2005, 2006; Moran et al , 2006; Moore and Expedition 302 Scientists , 2006; Jakobsson et al , 2007; Backman et al , 2008]. Details of the ACEX lithostratigraphy can be found online in the IODP Proceedings Volume 302 http://publications.iodp.org/proceedings/302/302toc.htm), and in papers from the 2008 ACEX special section “Cenozoic Paleoceanography of the Central Arctic Ocean” in Paleoceanography , 23 (1), 2008 [see Backman and Moran , 2008].…”

Tectonic subsidence of the Lomonosov Ridge

“…44 Ma) to lower Miocene (ca. 18.2 Ma) strata are missing in the section (Moore et al, 2006;Moran et al, 2006;Backman et al, 2008). It is generally accepted that such large unconformities must be related to tectonic uplift and erosion.…”

“…However, according to conventional thermal kinematic models, the Lomonosov Ridge should have subsided by >1 km due to crustal thinning and cooling of the lithosphere by the middle Eocene. To explain the missing section, some (e.g., Moore et al, 2006) suggest a 26-m.y.-long period of non-deposition related to paleoenvironmental processes such as large-scale seabottom currents. The evidence of high surface temperatures (~24 ºC) in the Eocene (below the hiatus), the presence of ice-rafted debris in the Neogene sediments (above the hiatus), and Miocene opening of the Fram Strait (e.g., Moran et al, 2006) contribute to this hypothesis.…”