Geology and Paleoceanography
-- Geolog y and Paleoceanography --
Sources of Ice-Rafted Detritus and Iceberg Tracks in the Arctic Ocean
Dennis A. Darby and Jens F. Bischof
The sources of ice-rafted detritus (dropstones) were determined by match-
ing the elemental composition of iron oxide grains and percentages of grain
types in Arctic Ocean deep-sea sediment cores to potential sources around the
Arctic Ocean. This "fingerprinting" technique required prior characterization
of source areas in the Arctic providing debris that could be rafted into the
central Arctic Ocean by icebergs or sea ice. Eleven statistically unique source
areas were defined by grain type percentages and microprobe chemical analy-
ses of thousands of individual iron oxide grains (Darby and Bischof 1996).
Erk Reimnitz col-
from the ice.
For the first time the sources of ice-rafted grains in the Arctic Ocean were
traced with a high level of statistical probability. This allowed us to recon-
struct the ice drift tracks and the ocean surface currents in the past and to get
a better understanding of the nature and history of Arctic glaciations. Finally
the potential of pollutants being spread throughout the Arctic Ocean from
point sources on the Russian shelves can be assessed.
The major sources of detritus in 17 of the deep-sea cores thus far analyzed
(4 of 18 cores from the AOS-94 cruise and 13 from previous expeditions) are
the Banks and Victoria Island area and the Sverdrup Basin area around Ellef
Ringnes Island and northern Melville Island. The Mackenzie River basin con-
Dennis Darby and Jens Bischof are with the Department of Geological Sciences at Old Dominion University in
Norfolk, Virginia, U.S.A.