First bedrock samples dredged from submarine outcrops in the Chukchi Borderland, Arctic Ocean

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

“…It has not been possible to correlate horizons between the top and bottom of the escarpment, although the minimum throw can be constrained by the 2,000–2,800 m offset between the top of Northwind Ridge and the adjacent seafloor of Canada Basin. Previous studies have interpreted Northwind Escarpment as a compressional zone resulting from clockwise rotation of Chukchi Borderland (Doré et al, ; Grantz et al, ) or an extensional fault system that is part of a basin and range tectonic regime (Brumley, ). The seismic reflection data crossing the escarpment do not support either of those opposing interpretations.…”

“…Northeast‐trending features are evident in the bathymetric fabric (Figure a) within Chukchi Borderland (Brumley, ; Hall, ). The most prominent of these features is an elongate northeast‐trending basin within Chukchi Plateau called the Egiazarov Trough (ET, Figures and a), formerly called the Central Chukchi Basin by Brumley () and Brumley et al (). This trough is ∼175 km long by ∼30 km wide (i.e., an aspect ratio of almost 6:1), with vertical relief of more than 2,000 m. Slopes along the edges of the basin are commonly greater than 5° and locally more than 60° (Brumley, ).…”

“…The most prominent of these features is an elongate northeast‐trending basin within Chukchi Plateau called the Egiazarov Trough (ET, Figures and a), formerly called the Central Chukchi Basin by Brumley () and Brumley et al (). This trough is ∼175 km long by ∼30 km wide (i.e., an aspect ratio of almost 6:1), with vertical relief of more than 2,000 m. Slopes along the edges of the basin are commonly greater than 5° and locally more than 60° (Brumley, ). Although interpreted by Brumley () to be caused by east‐west extension, the Egiazarov Trough has limited seismic data that show faults with normal movement, steep, en‐echelon faults of variable dips with little consistent thickening of the sedimentary section across the faults, and many horst blocks (Figure a).…”

“…This trough is ∼175 km long by ∼30 km wide (i.e., an aspect ratio of almost 6:1), with vertical relief of more than 2,000 m. Slopes along the edges of the basin are commonly greater than 5° and locally more than 60° (Brumley, ). Although interpreted by Brumley () to be caused by east‐west extension, the Egiazarov Trough has limited seismic data that show faults with normal movement, steep, en‐echelon faults of variable dips with little consistent thickening of the sedimentary section across the faults, and many horst blocks (Figure a). These geometries are similar to ones along similar sized pull‐apart basins such as the Gulf of Aqaba at the south end of the Dead Sea (Ben‐Avraham et al, ), where 6–8 km of sediment are contained within large normal faults on each side of the pull‐apart basin and intrabasinal longitudinal and oblique faults form the internal structural fabric.…”

“…When reconstructed, the borderland overlaps the Canadian Arctic Islands, requiring unique complexities to avoid the overlap (e.g., Amato et al, ; Doré et al, ; Grantz et al, ; Lawver & Scotese, ; Shephard et al, ). Recent detrital zircon analyses have linked Chukchi Borderland to Ellesmere Island (O'Brien et al, ) or more broadly to Caledonian rocks further north (Brumley et al, ). Complicating any tectonic interpretation is the presence of the Alpha‐Mendeleev Ridge System and its associated High Arctic Large Igneous Province (HALIP; Døssing et al, ; Maher, ; Oakey & Saltus, ; Saltus et al, ).…”