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Distribution of benthic foraminifers (>125 um) in the surface sediments of the Arctic Ocean

August 1, 1999

Census data on benthic foraminifers (>125 ?m) in surface
sediment samples from 49 box cores are used to define
four depth-controlled biofacies, which will aid in the paleoceanographic
reconstruction of the Arctic Ocean. The shelf
biofacies contains a mix of shallow-water calcareous and
agglutinated species from the continental shelves of the
Beaufort and Chukchi Seas and reflects the variable sedimentologic
and oceanic conditions of the Arctic shelves.
The intermediate-depth calcareous biofacies, found between
500 and 1,100 meters water depth (mwd), contains abundant
Cassidulina teretis
, presumably indicating the influence of
Atlantic-derived water at this depth. In water depths
between 1,100 and 3,500 m, a deepwater calcareous biofacies
contains abundant
Oridorsalis umbonatus
. Below 3,500
mwd, the deepwater mixed calcareous/agglutinated biofacies
of the Canada, Makarov, and Eurasian Basins reflects a
combination of low productivity, dissolution, and sediment
Two other benthic foraminiferal species show specific
environmental preferences.
Fontbotia wuellerstorfi
has a
depth distribution between 900 and 3,500 mwd, but maximum
abundance occurs in the region of the Mendeleyev
Ridge. The elevated abundance of
F. wuellerstorfi
may be
related to increased food supply carried by a branch of
Atlantic water that crosses the Lomonosov Ridge near the
Russian Continental Shelf.
Triloculina frigida
is recognized
to be a species preferring lower slope sediments commonly
disturbed by turbidites and bottom currents.
At present, our understanding of the Arctic Ocean lags
behind our understanding of other oceans, and fundamental
questions still exist about its role in and response to global
climate change. The Arctic Ocean is particularly sensitive to
climatic fluctuations because small changes in the amounts
of sea-ice cover can alter global albedo and thermohaline
circulation (Aagaard and Carmack, 1994). Numerous questions
still exist regarding the nature and timing of paleoclimatic
events in the Arctic Ocean. In order to attempt to
answer some of these questions, baseline studies are imperative.
This report discusses the distribution of benthic foraminifers
in surface sediment samples from 49 box cores
(figs. 1 and 2, table 1) collected by the U.S. Geological Survey
(USGS) with the assistance of the U.S. Coast Guard
(USCG). A modern data set of benthic foraminiferal distribution
is necessary for interpreting the paleoclimatic and
oceanographic history of the Arctic Ocean.