Abstract:
Fifty sites on the Mackenzie Shelf were sampled for foraminifera as part of the 2004 (Leg 8) Canadian Shelf Exchange Study (CASES). Part of this study sampled the Kopanoar mud volcano. A group of species observed on the Kopanoar mud volcano are described, along with the possibility of using the foraminifera to detect methane gas on the shelf and the implications (if any) this may have on the atmosphere. Two cores, 805A from the top of the mud volcano and 805C from the moat of the mud volcano, had samples taken every centimeter. Another core, 609A, from a non-mud volcano control site in the pingo area of the shelf, was sampled every 5 centimeters. The foraminifera in the core samples are typical for the Arctic shelf marine environment and include species such as Islandiella teretis and Elphidium exc. f. clavatum. The presence of Ammotium cassis in parts of the cores may be an indicator that thermogenic methane is being released from the mud volcano area, along with the possibility of oxidation of biogenic methane in the non mud volcano area. The presence of Trochammina macrescens implies ice transport from salt marshes on the Mackenzie Delta. Elphidiella hannai has been found for the first time north of Vancouver Island, and seems only to occur with methane related areas. The three cores contain 37 species. The >63 mu samples had the highest diversity of foraminifera and the >45 mu < 63 mu samples had large numbers but relatively few species; some of these species were deep water Arctic species. The species that were found in the small fraction were normally not found in the >63 mu size fraction. The 805A sample had foraminifera in the top three centimeters followed by a dead zone with no foraminifera until the 14 centimeter level. A second dead zone occurred in the lower half of the 805A core. These dead zones could be interpreted as a sign of higher than normal methane activity. No such zone was found in the 805C which is at the base of the mud volcano, although there is a good presence of Ammotium cassis. This suggests, that at least during two periods of time, that there were much higher concentrations of methane seepage at the summit of the volcano, than there were at the areas of the other two cores.