Devonian geology of Banks Island, Arctic Canada, and its bearing on the tectonic development of the circum-Arctic region

摘要

New information, predominantly from the subsurface, shows that the Devonian rocks of Banks Island comprise four units: a shelf carbonate formation (Siegenian? to Eifelian), a basin-slope calcareous shale (Emsian to late Givetian), a basinal cherry shale (Emsian to Eifelian), and a predominantly deltaic clastic unit (Givetian to Famennian). Paleogeographic reconstructions show southern Banks Island as part of the stable shelf in Early Devonian time. During Middle Devonian time, subsidence took place, and basinal conditions encroached on the shelf from the north. The deep basin is considered to be part of Hazen Trough, which probably was connected with Richardson Trough of northern Yukon. Subsequent tectonic events have left the Devonian rocks of Banks Island relatively undisturbed, in comparison with those of the Parry Islands to the north. Evidence of subduction and plate collision — such as strong deformation, the development of orogenic welts, and the production of thick, locally derived clastic wedges — is absent in Banks Island, in contrast to areas such as northern Ellesmere Island and northern Alaska. Therefore, if plate movements did take place in the Arctic during Devonian time, Banks Island may have lain opposite an embayment in the advancing plate, resulting in incomplete suturing, as described by Dewey and Burke. However, no satisfactory hypothesis of plate motion in the Arctic has yet been developed, in spite of many attempts.