Developing Geophysical Constraints on the History of the Amerasian Basin of the Arctic Ocean

Abstract

Abstract The Chukchi Edges project was designed to establish the relationship betweenthe Chukchi Shelf and Borderland and indirectly test theories of opening forthe Canada Basin. During this cruise, ~5300 km of 2D multi-channel seismicprofiles and other geophysical measurements (swath bathymetry, gravity, magnetics, sonobuoy refraction seismic) were collected from the RV Marcus G. Langseth across the transition between the Chukchi Shelf and ChukchiBorderland. These profiles reveal extended basins separated by faulted high-standingblocks. Basin stratigraphy can be subdivided on the basis of gross stratalgeometry, reflection terminations and inferred unconformities. The wedge-shapedsynrift sequences terminate against the basement highs and/or major faults, burying the basement topography. The inferred postrift seismic units are morenearly tabular, but thicken locally due to compaction of underlying synriftsediments. Reflection character is dominated by alternating high and low amplitudecontinuous reflectors which may be consistent with pelagic or turbiditesediments. Chaotic units are also observed, which may indicate mass-flowdeposits. The truncated sediments over the basement highs of the Chukchi Shelf, Chukchi Plateau and Northwind Ridge suggest major erosion due both to glacialplanation and earlier erosional events perhaps associated with basement upliftprior to or during rifting and extension. It is believed that the bulk of the synrift sediments are Mesozoic in age. Certainly Cenozoic sediments are also preserved in these basins, but theposition of the boundary is uncertain. Locally, continuous reflectors areobserved underlying the rift basin fill. These older units, of very uncertainage, would, if sampled, provide constraint on the history and affinities of theChukchi Borderland. In addition to the extensional basins, a number of small symmetric basinsare observed on the flanks of the Chukchi Plateau. These basins may betranstensional and argue for a 2nd phase of tectonism, which overprinted theobvious extensional fabric of the Borderland. This is supported by theobservation of uplifted postrift sediments on the flanks of some of theintermedial basement highs. Understanding the timing, distribution and extentof these two phases of tectonism, relative to the known history of N-Sextension on the Chukchi shelf and the apparent orthogonal extension observedon the Beaufort Shelf will further constrain the unknown history of the CanadaBasin.