Samples from the Lomonosov Ridge place new constraints on the geological evolution of the Arctic Ocean

Abstract

A number of rock samples were collected from two dredge positions on the Lomonosov Ridge at water depths of 2–3.5 km. The dredge samples are dominated by sediments deformed and metamorphosed under greenschist-facies conditions 470 myr ago according to 40Ar/39Ar dating of metamorphic muscovite. This shows that the Lomonosov Ridge was involved in a major Mid-Ordovician orogenic event that correlates with early arc–terrane accretion observed in northern Ellesmere Island, Svalbard, and other parts of the Caledonian belt. Detrital zircon age spectra of these metasediments span the Mesoproterozoic–Palaeoproterozoic with a main peak at around 1.6 Ga, and a pattern similar to that known from Caledonian metasedimentary rocks in East Greenland and northern Norway, as well as from Cambrian sediments in Estonia and Palaeozoic sediments on Novaya Zemlya. A second population of dredge samples comprises undeformed, non-metamorphic sandstones and siltstones. Detrital zircons in these sediments span the Palaeoproterozoic with a few Archaean zircons. Both rock types are covered by an up to 8 Ma ferromanganese crust and are evaluated to represent outcrop, and apatite fission-track data from three of the rock samples indicate that exposure at the seabed corresponds to a regional event of uplift and erosion that affected the Arctic in the Late Miocene. The data from the Lomonosov Ridge suggest that the 470 Ma orogenic event extended from Scotland and northern Scandinavia into the Arctic, including Svalbard, the Pearya Terrane and the Chukchi Borderlands.

Significance of Northeast‐Trending Features in Canada Basin, Arctic Ocean

“…Three aspects of the Chukchi Borderland are (a) it has been reduced in east‐west width (current coordinates) to close Northwind Basin, i.e., the basin between Northwind Ridge and the Chukchi Plateau, similar to the closures presented by Shephard et al (), Amato et al (), and O'Brien et al (); (b) it is not significantly rotated relative to Arctic Alaska, i.e., closure is only to the point where the Chukchi Borderland obliquely touches the Canadian margin near Ellesmere Island; and (c) the North Chukchi Basin is closed (NCB, Figures and d), reducing the distance between the Hanna Trough and Chukchi Borderland. The position of the Borderland near the Canadian coast is similar to that determined by lithologic, zircon, and age dating analyses from dredge samples that correlate the Chukchi Plateau with the Pearya terrane on Ellesmere Island and Northwind Ridge with Laurentian (Cambrian Franklinian) rocks to the south of Pearya (P in Figure d) (Knudsen et al, ; O'Brien et al, ). Our position of the Chukchi Borderland is slightly to the north of that proposed by O'Brien et al () and Grantz et al (), so that the Chukchi Borderland is adjacent to and does not overlap Sever Spur.…”

“…Chukchi Basin is closed (NCB, Figures 1 and 7d), reducing the distance between the Hanna Trough and Chukchi Borderland. The position of the Borderland near the Canadian coast is similar to that determined by lithologic, zircon, and age dating analyses from dredge samples that correlate the Chukchi Plateau with the Pearya terrane on Ellesmere Island and Northwind Ridge with Laurentian (Cambrian Franklinian) rocks to the south of Pearya (P in Figure 7d) (Knudsen et al, 2017;O'Brien et al, 2016). Our position of the Chukchi Borderland is slightly to the north of that proposed by O'Brien et al (2016) and Grantz et al (1998), so that the Chukchi Borderland is adjacent to and does not overlap Sever Spur.…”

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

“…Thus, we correlate the oxygenated late Miocene interval in the ACEX record (starting at 193‐m core depth) to a phase of sediment drift accumulation along the LR indicated within unit 4. The top of unit 4 is assigned an age of 10.6–8 Ma based on correlation to a 10 Be dated hiatus at 135.5–140.4 m in the ACEX core (Frank et al, ; recalibrated according to Chmeleff et al, ) and the onset of ferromanganese crust growth on the LR flank (Knudsen et al, ). This latter observation is consistent with the onset of a higher energy environment inferred above unit 4 and that is necessary for the crust to grow and be preserved (Föllmi, ).…”

“…It is uncertain when the high‐energy depositional phase along the LR began, but it may be associated with a hiatus observed in the ACEX cores (Frank et al, ) and the onset of Fe‐Mn crust formation on the ridge flank (Knudsen et al, ), suggesting an age of 10.6–8 Ma (Figure ). The channelized sedimentary regime observed in units 5 and 6 is thus tentatively correlated to the U 1/1‐U 1/3 interval of the ACEX record, which represents large scale‐glaciation of the northern hemisphere (Zachos et al, ).…”

“…Seismic refraction data were collected with sonobuoys and, in some instances, recoverable ice stations (e.g., Chernykh & Krylov, 2011;Fütterer, 1992;Jokat et al, 1995a;Jokat & Micksch, 2004;Ostenso & Wold, 1977). Rock samples collected by dredging are sparse (Brumley et al, 2015;Knudsen et al, 2017;Michael et al, 2003) and shallow cores (Fütterer, 1992;Svindland & Vorren, 2002) constrain only the most recent Quaternary depositional history. The only source of deep stratigraphic information comes from scientific ocean drilling during Integrated Ocean Drilling Program expedition 302, the Arctic Coring Expedition (ACEX).…”