Sedimentology of the Prince Gustaf Adolf Sea area, District of Franklin

The Prince Gustaf Adolf Sea area is located on the continental shelf bordering the Arctic Ocean . It is und erlain principally by moderately deformed siltstone , sandstone, and shal e formations of Mesozoic to Tertiary age that form part of the Sverdrup Basin st r uctural province, and by uncon solidated sand and gravel of the Arct ic Coastal Plain (Beaufort Formation). The physical setting.is dominated by a polar climat ic regime, whichmaintains an ice cover over the area throughout most of the year . Physiographic features of the area suggest that the sea bottom has been exposed previously to subaerial processes of erosion. On a broad scale, channels form a d end ritic pattern , the gradient of which is generally toward the Arctic Ocean. Smaller scale features suggest that ice action has been effective in shap ing the present sea bottom . An island shelf and slope occurs around all the land masses of the area and forms a nickpoint in the bottom profile that may represent a stillstand of sea level 300- 400 metres deeper than the present level. Under present conditions, sand is transported from the islands by ephemeral streams and deposited in relatively shallow depths near shore. Mud covers the greater part of the area . However, sandy layers occur in the sub - bottom at nearshore stations, indicating that hydraulic energy levels at those stations have been higher in the past than they are at present. Sediment textures coarsen with depth in cores from throughout the area and suggest that there was a general lowering of energy levels during the deposition of the sediment contained in core samples. Increasing depth of water associated with a transgressive sea i s infe r red from these data . Core samples show tha t two major stratigraphic units are present in the sediment of Prince Gustaf Adolf Sea . These are ( 1) an upper, yellowbrown, generally structureless unit containing foraminiferal remains and abundant oxidized , detrital pyrite; and (2) an underlying, grey unit that conta ins fine bedding structures, fresh, detrital pyrite, and no faunal remains. Contacts between these units are generally transitional , and commonly do not coincide with textural changes . Characteristics of the two units indicate that they were deposited in widely differing sedimentary environments . In the lower unit, the absence of faunal remains and the presence of fresh, detrital pyrite and fine depositional structures suggest a restricted, reducing environment in which there was little or no life. Very fine, cyclical laminae in this unit indicate that glaciers or ice caps may have dominated the sedimentary environment during the deposition of the unit. Beds of the upper unit, however, appear to have been deposited in a relatively well-oxygenated environment in which an abundant microfauna existed. The change from restricted to open, ventilated conditions probably was a result of an incursion of water from the Arctic Ocean over topographic sills into the Prince Gustaf Adolf Sea area. The distribution of foraminifera in the upper unit may be related to former current patterns