Osterman and others—DISTRIBUTION OF BENTHIC FORAMINIFERS (>125 μm), ARCTIC OCEAN—U.S. Geological Survey Bulletin 2164

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U.S. Geological Survey

Distribution of Benthic Foraminifers (>125 μm) in the 

Surface Sediments of the Arctic Ocean

By Lisa E. Osterman, Richard Z. Poore, and Kevin M. Foley

U.S. GEOLOGICAL SURVEY BULLETIN 2164

Environmental and oceanographic preferences of

benthic foraminifers are interpreted by using 

surface sediment samples from 49 box cores 

from the sea floor in the Arctic Ocean
U.S. DEPARTMENT OF THE INTERIOR

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY

CHARLES G. GROAT, Director

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1999

Published in the Eastern Region, Reston, Va.

Manuscript approved for publication October 9, 1998.

Any use of trade, product, or firm names in this publication is for descriptive purposes only and

does not imply endorsement by the U.S. Government.

For sale by

U.S. Geological Survey

Information Services

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Denver, CO 80225

Library of Congress Cataloging in Publication Data

Osterman, Lisa E.

Distribution of benthic foraminifers (>125 μm) in the surface sediments of the Arctic Ocean / by Lisa E. Osterman, Richard Z.

Poore, and Kevin M. Foley.

p. cm.—(U.S. Geological Survey bulletin ; 2164)

Includes bibliographical references.

1. Foraminifera—Arctic Ocean—Vertical distribution. I. Poore, Richard Z. II. Foley, Kevin M. III. Title. IV. Series. 

QL368.F6078 1999 98–49720

579.4'417732—dc21 CIP
III

CONTENTS

Abstract ........................................................................................................................... 1

Introduction .................................................................................................................... 1

Acknowledgments................................................................................................... 1

Ridges and Basins of the Arctic Basin .................................................................... 1

Oceanography of the Arctic Ocean ......................................................................... 5

Productivity of the Arctic Ocean............................................................................. 5

 Previous Foraminiferal Studies of the Arctic Ocean ............................................... 7

Methods........................................................................................................................... 8

Results ............................................................................................................................. 9

Northwind Ridge, Canada Basin, and Beaufort Slope and Shelf (Table 4)............ 9

Arctic Transect (Table 5)......................................................................................... 9

Discussion ....................................................................................................................... 9

Depth Zonation of Benthic Foraminifers................................................................ 9

Shelf Biofacies................................................................................................... 12

Intermediate-Depth Calcareous Biofacies ......................................................... 12

Deepwater Calcareous Biofacies....................................................................... 13

Deepwater Mixed Calcareous/Agglutinated Biofacies...................................... 13

Distribution of Fontbotia wuellerstorfi................................................................... 14

Distribution of Triloculina frigida ......................................................................... 15

The Question of Sieve Size .................................................................................... 16

Summary ......................................................................................................................... 16

References Cited ............................................................................................................. 17

Appendix. Systematic List and Taxonomic Notes for Benthic Foraminifers

>125 μm Counted in This Study of the Arctic Ocean ........................................... 26

FIGURES

1, 2. Maps of the Arctic Ocean showing bathymetry and—

1. Locations where box cores were collected in 1992, 1993, and 1994 .................................................................. 2

2. Geographic features mentioned in the text, ice-island stations discussed by Scott and Vilks (1991), 

and Hydrocast stations mentioned in figure 3 ..................................................................................................... 3

3. Graph showing temperature and salinity profiles from Hydrocast stations H93-13 (Northwind Ridge), 

H93-21 and H93-22 (central Canada Basin), and H93-26 (eastern Canada Basin)..................................................... 6

4–6. Graphs showing percentages of benthic foraminifers plotted by water depth:

4. Selected benthic foraminifer species >125 μm in samples from the Arctic Ocean............................................. 11

5. Two benthic foraminifer species >125 μm (Fontbotia wuellerstorfi and Miliolinella subrotunda)

in samples from two different geographic areas of the Arctic Ocean ................................................................. 12

6. Selected benthic foraminifer species >63 μm in samples from the Chukchi Basin, Alpha Ridge, and 

Canada Basin....................................................................................................................................................... 14
IV CONTENTS

TABLES

[Tables 4–7 follow References Cited and precede Appendix]

 

1. Latitude, longitude, water depth, and location of sites where box cores were collected in this study 

of the Arctic Ocean..................................................................................................................................................... 4

2. Rank and percentage of major benthic foraminifer species in two size fractions (>63 μm and >125 μm)

of five samples from a previous study of the Arctic Ocean........................................................................................ 8

3. Planktic foraminifers, benthic foraminifers, and sediment grains per gram in surface sediment 

samples (>125 μm) from this study of the Arctic Ocean ........................................................................................... 10

4, 5. Percentages of benthic foraminifers >125 μm in samples from the—

4. Northwind Ridge area, Canada Basin, and Beaufort area................................................................................... 20

5. Arctic transect from the Chukchi Shelf to the Eurasian Basin ........................................................................... 22

6, 7. Percentages of selected shallow-water benthic foraminifers >125 μm in samples from the—

6. Northwind Ridge area, Canada Basin, and Beaufort area.................................................................................. 24

7. Arctic transect from the Chukchi Shelf to the Eurasian Basin........................................................................... 24

 For temperature conversions from degrees Celsius (°C) to degrees 

Fahrenheit (°F), use the following:

°F = (1.8 × °C) + 32

METRIC CONVERSION FACTORS

Multiply By To obtain

micrometer (μm) 0.0000394 inch

meter (m) 3.281 foot

cubic centimeter (cm3) 0.06102 cubic inch

gram (g) 0.03527 ounce avoirdupois
1

Distribution of Benthic Foraminifers (>125 μm) in the 

Surface Sediments of the Arctic Ocean

By Lisa E. Osterman, Richard Z. Poore, and Kevin M. Foley 

ABSTRACT

Census data on benthic foraminifers (>125 μm) 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

transport.

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. 

INTRODUCTION

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. 

ACKNOWLEDGMENTS

The work described in this report was funded by the

U.S. Geological Survey’s Global Change and Climate History Program. We thank the U.S. Coast Guard for assistance

in collecting the box cores in the 1992, 1993, and 1994 field

seasons. We also thank the Canadian Coast Guard for support with the 1994 sampling program. We thank Ann Rogers

(of the USGS) for technical assistance. We thank Martin A.

Buzas (Smithsonian Institution), Scott E. Ishman (USGS),

Leonid V. Polyak (Ohio State University), and David B.

Scott (Dalhousie University) for helpful reviews. 

RIDGES AND BASINS OF THE ARCTIC BASIN

The Arctic Ocean occupies the Arctic Basin, which

contains several basins and ridges (fig. 2):

• The Lomonosov Ridge, a flat-topped continental fragment believed to have been rifted from the Eurasian

margin, lies at an average of 1,600 meters water depth

(mwd) and effectively prevents deepwater exchange

between the Eurasian Basin to the east and the Amerasian Basin to the west (Aagaard and others, 1985;

Aagaard and Carmack, 1994). 

• The Eurasian Basin, centered around the actively

spreading Gakkel Ridge, lies between 3,000 and 4,000

mwd. The Eurasian Basin contains the Nansen and

Amundsen Basins. 
2 DISTRIBUTION OF BENTHIC FORAMINIFERS (>125 μm) IN THE SURFACE SEDIMENTS OF THE ARCTIC OCEAN



STUDY AREA

Pacific

Ocean

500

2000

2000

2000

2000

3000

3000

3000

3000

500

500

500

500

Alaska

Greenland

EXPLANATION

RUSSIA

USA

CANADA

Arctic

Ocean

Atlantic

Ocean

1994 

1992 

1993 

Individual 

box core sites:

1992 (Samples 7, 8,

9, 10, 11, and 12)

1993 (Samples 2, 3, 4,

5, 7, 8, 10, 11, and 12)

Closely spaced 

box core sites:

Russia

Svalbard

120° 120°

180°

90°E

180°

30°

75°

150°

80°

60°

TRANSPOLAR DRIFT

93-14

94-33

94-31

94-30 94-26,28

94-25

94-12 94-16

94-17

94-19

94-20

94-21

94-23

94-24

94-8

94-7

94-6

92-17

92-15

92-16

92-6

93-16 93-15

93-17

93-18

93-19

93-20

93-21

92-5

92-4

92-3

92-1

92-2

94-32

Figure 1. Locations in the Arctic Ocean where box cores were collected in

1992, 1993, and 1994. To save space, the box core designation “B” is omitted

from sample numbers on the map; the full sample numbers and location

descriptions are given in table 1. Generalized bathymetry in meters is modified from Perry and Fleming (1986).
INTRODUCTION 3

STUDY AREA

Pacific

Ocean

500

2000

2000

2000

2000

3000

3000

3000

3000

500

500

500

500

Alaska

Greenland

RUSSIA

USA

CANADA

Arctic

Ocean

Atlantic

Ocean

Russia

Svalbard

120° 120°

180°

90°E

180°

30°

75°

150°

80°

60°





     



Amundsen 

Basin

Makarov Basin

Mendeleyev Ridge

Gakkel Ridge

T-3

Nansen Basin

Canada 

Basin

Barents 

Sea

Chukchi 

Sea

Laptev

Sea

Kara 

Sea

East Siberia 

Sea

26

22

2113

Bering 

Strait 

T-3

T-3

EURASIAN BASIN

AMERASIAN BASIN

Beaufort 

Sea

Chukchi

Plateau

Northwind

 Ridge

Chukchi

Basin

T-3

Lomonosov Ridge

CESAR

Alpha

Ridge

LOREX

Franz-Josef

 Land

Morris 

Jesup

Rise 

Fram II

Fram 

Strait

Fram lll

Greenland 

Basin

Figure 2. Bathymetry of the Arctic Ocean and geographic features

mentioned in the text. LOREX, CESAR, Fram II, Fram III, and T-3

are ice-island stations yielding benthic foraminifers discussed by

Scott and Vilks (1991); see text section, “Previous Foraminiferal Studies of the Arctic Ocean.” Data collected at the four Hydrocast stations

(triangles numbered 13, 21, 22, and 26) are presented in figure 3; to

save space, the prefix “H93-” is omitted from each sample number.
4 DISTRIBUTION OF BENTHIC FORAMINIFERS (>125 μm) IN THE SURFACE SEDIMENTS OF THE ARCTIC OCEAN

Table 1. Latitude, longitude, water depth, and location of sites where box cores were collected in this study of the Arctic Ocean.

[Core sites are plotted in figure 1, and ridges and basins are labeled in figure 2. yr B.P., years before present; carbon-14 ages in the last column are given

in years before 1950, the beginning of the present era of widespread human use of radioactivity. The accelerator mass spectrometer (AMS) carbon-14

ages were determined on more than 2,000 specimens of the planktic foraminifer Neogloboquadrina pachydermal (sinistral) from the surface sediment

samples; the ages were determined at the Lawrence Livermore Laboratory’s Center for Accelerator Mass Spectrometry (CAMS) in Livermore, Calif. The

carbon-14 ages are corrected for water-mass-reservoir effects by subtracting 440 years (Darby and others, 1997)]

Box core no. Latitude Longitude

Water depth 

(meters) Location name

C-14 age 

(yr B.P.)

92-B5.................. 74°30.58' N 159°58.63' W 585 Northwind Ridge

93-B2.................. 74°45.33' N 157°53.2' W 893 Northwind Ridge

92-B7.................. 74°49.22' N 157°33.48' W 1,055 Northwind Ridge 3,470 ± 60

92-B8.................. 74°49.42' N 157°25.54' W 1,402 Northwind Ridge

93-B3.................. 74°44.5' N 157°27.4' W 1,536 Northwind Ridge

93-B4.................. 74°44.4' N 157°23.5' W 1,779 Northwind Ridge

93-B5.................. 74°44.4' N 157°21.7' W 1,942 Northwind Ridge

92-B9.................. 74°49.5' N 157°12.3' W 2,120 Northwind Ridge 3,640 ± 60

93-B7.................. 74°44.4' N 157°18.9' W 2,476 Northwind Ridge

93-B8.................. 74°44.0' N 157°17.1' W 2,560 Northwind Ridge

92-B10................ 74°48.8' N 157°06.2' W 3,145 Northwind Ridge 3,540 ± 60

93-B10................ 74°44.5' N 157°11.4' W 3,365 Northwind Ridge

93-B11................ 74°44.2' N 157°09.5' W 3,482 Northwind Ridge

93-B17................ 73°52.4' N 140°36.5' W 3,498 Canada Basin

93-B16................ 74°36.2' N 142°05.8' W 3,680 Canada Basin

93-B15................ 75°20.3' N 150°00.4' W 3,808 Canada Basin

92-B12................ 74°49.46' N 156°52.37' W 3,811 Canada Basin 1,500 ± 60

93-B12................ 74°43.5' N 156°52.8' W 3,818 Canada Basin

93-B14................ 74°49.2' N 155°00.3' W 3,842 Canada Basin

93-B18................ 72°08.5' N 141°08.1' W 2,940 Beaufort Sea continental slope

93-B19................ 71°17.0' N 147°20.9' W 2,089 Beaufort Sea continental slope

93-B20................ 71°03.8' N 147°19.9' W 1,190 Beaufort Sea continental slope

93-B21................ 71°00.9' N 147°21.5' W 401 Beaufort Sea continental shelf

92-B1.................. 72°24.2' N 164°18.2' W 49 Chukchi Sea continental shelf

92-B2.................. 72°23.8' N 164°16.2' W 48 Chukchi Sea continental shelf

92-B3.................. 73°41.6' N 162°39.8' W 201 Chukchi Sea continental shelf

92-B17................ 76°05.19' N 164°50.15' W 402 Chukchi Plateau 2,110 ± 60

92-B4.................. 74°00.00' N 161°23.7' W 447 Chukchi Sea continental slope

94-B6.................. 75°21.45' N 170°30.44' W 528 Chukchi Sea continental slope

92-B16................ 75°43.75' N 160°05.54' W 1,388 Chukchi Sea continental slope

92-B6.................. 74°59.74' N 159°18.27' W 1,845 Chukchi Basin 1,240 ± 60

92-B15................ 75°44.05' N 160°51.63'W 2,135 Chukchi Basin

94-B7.................. 76°39.99' N 173°23.09' W 2,214 Chukchi Basin

94-B8.................. 78°07.68' N 176°44.67' W 1,031 Mendeleyev Ridge

94-B12................ 79°59.32' N 174°17.32' W 1,609 Mendeleyev Ridge

94-B16................ 80°20.33' N 178°42.71' W 1,533 Mendeleyev Ridge

94-B17................ 81°15.91' N 178°58.05' E 2,217 Mendeleyev Slope

94-B19................ 82°26.80' N 175°45.50' E 2,400 Mendeleyev Slope

94-B20................ 83°10.20' N 174°06.36' E 3,110 Makarov Basin

94-B21................ 84°05.72' N 174°57.82' E 3,193 Makarov Basin

94-B23................ 85°54.40' N 166°41.00' E 3,475 Makarov Basin

94-B24................ 87°09.70' N 161°02.20' E 3,890 Makarov Basin

94-B25................ 88°03.30' N 147°40.80' E 2,125 Lomonosov Slope

94-B26................ 88°48.60' N 142°58.90' E 1,020 Lomonosov Ridge

 94-B28................ 88°52.40' N 140°10.80' E 1,990 Lomonosov Slope 2,250 ± 60
INTRODUCTION 5

• The Amerasian Basin is divided into the Makarov and

Canada Basins. The Makarov Basin is a smaller triangular basin, which lies between the Lomonosov Ridge

and the Alpha Ridge-Mendeleyev Ridge. The Canada

Basin is west of the Makarov Basin and contains several continental fragments and associated basins

(Northwind Ridge and Chukchi Plateau and Basin). 

The deep basins in the Arctic Basin are surrounded by

a narrow Canadian Continental Shelf and a wide Eurasian

Continental Shelf. Seas above the Eurasian Shelf are the

Chukchi, East Siberia, Laptev, Kara, and Barents Seas

(fig. 2).

OCEANOGRAPHY OF THE ARCTIC OCEAN

The modern Arctic Ocean has a Mediterranean-type

circulation. Freshwater from rivers combined with lowsalinity surface water entering from the Pacific Ocean

results in a strongly stratified ocean consisting of three main

water masses (fig. 3): Arctic Surface Water (ASW), Arctic

Intermediate Water (AIW), and Arctic Deep Water (ADW).

ASW contains input from the surface waters of both the

Pacific and Atlantic, which may be introduced to the deeper

Arctic Ocean through brine formation. In addition, the various forms of ADW and especially the AIW also contain elements of the deeper layers of the Atlantic Ocean. The

multiple sources of water complicate the oceanography of

the Arctic Ocean.

The Arctic Surface Water usually lies above the upper

0°C isotherm (fig. 3). The depth to the thermocline and the

thickness of the ASW are highly variable (75–300 mwd),

depending upon the location within the Arctic Ocean (Carmack, 1990; Aagaard and Carmack, 1994) (fig. 3). The

ASW includes areas of relatively warm and salty Atlantic

water (>3°C, >34.9 ‰) over the Barents Shelf and lowsalinity Polar water (<0°C, <34.4 ‰) in areas of melting

pack ice. Pacific water, having low salinity (32–33 ‰) and

high nutrient contents, enters through the Bering Strait. As

some Pacific water freezes on the Chukchi Shelf, the salt

content of the ocean water increases to form dense brines,

which are injected periodically into the intermediate and deep

waters of the Canada Basin (Aagaard and others, 1985;

Anderson and others, 1994; Swift and others, 1997). Similarly, it has been suggested by Anderson and others (1994)

that Atlantic-derived water freezes on the Barents and Kara

Shelves to form brines that are injected into the Eurasian

Basin.

The Arctic Intermediate Water, sometimes referred to

as “the Atlantic Layer,” lies between the two 0°C isotherms

and is identified as the warmest layer of the Arctic Ocean

with a relatively high salinity (Aagaard and others, 1985)

(fig. 3). The AIW represents the inflow of Atlantic water

into the Arctic Ocean through the Fram Strait. The core of

the AIW lies between 200 and 900 mwd, but the depth is

variable as the AIW is modified by various processes, such

as brine injection, that differ across the Arctic Ocean (Carmack, 1990; Swift and others, 1997). 

The Arctic Deep Water is mostly deeper than 900 mwd

and is cold (<0°C), but its temperature varies slightly by

location. The Canada Basin Deep Water (CBDW; –0.5°C,

>34.95 ‰) is the warmest and most saline Arctic Deep

Water. The coldest and freshest deep water is in the Greenland Basin (–1.2°C, <34.9 ‰), adjacent to the Arctic Ocean.

The Eurasian Basin has water of intermediate temperature

and salinity (–0.7°C, 34.94 ‰). The exchange of deep water

between the North Atlantic and the Arctic Ocean is limited

by the sill depth of the Fram Strait at 2,600 mwd.

PRODUCTIVITY OF THE ARCTIC OCEAN

Conventional wisdom would indicate that productivity

of the Arctic Ocean is low because of the heavy ice cover.

However, ice cover varies throughout the year, and large

fringe areas of pack ice melt each summer (Parkinson and

others, 1987). On the continental shelves of the Chukchi

and Bering Seas, a close relationship exists between surface-water productivity and benthic biomass (Grebmeier

and Barry, 1991). On these Arctic shelves, the highest total

benthic biomass is found in areas with the largest flux of

high-quality nitrogen-rich food (Grebmeier, 1993). The

high surface-water productivity in this area is related to the

influx of nutrient-rich Pacific water (Springer and McRoy,

1993). Pacific water contains double the nitrogen (N) and

phosphorus (P) and seven times the silicon (Si) of North

Table 1. Latitude, longitude, water depth, and location of sites where box cores were collected in this study of the Arctic Ocean—

Continued.

Box core no. Latitude Longitude

Water depth 

(meters) Location name

C-14 age 

(yr B.P.)

94-B30 ................ 88°59.97' N 137°29.70' E 3,930 Eurasian Basin/Amundsen Basin

94-B31 ................ 89°58.85' N 40°30.39' E 4,180 Eurasian Basin/Amundsen Basin

94-B32 ................ 85°43.04' N 37°44.52' E 3,450 Eurasian Basin/Gakkel Ridge

94-B33 ................ 84°16.14' N 34°44.39' E 3,940 Eurasian Basin/Nansen Basin
6 DISTRIBUTION OF BENTHIC FORAMINIFERS (>125 μm) IN THE SURFACE SEDIMENTS OF THE ARCTIC OCEAN

Atlantic water (Heimdal, 1989); these nutrients result in

extremely high primary production of surface plankton,

which often sinks directly to the sea floor (Grebmeier, 1993;

Springer and McRoy, 1993).

Surface-water productivity in the upper 100 m of the

Amerasian Basin indicates an active planktonic community,

which would support the cycling of organic carbon to the

benthos. The highest productivity occurs in the surface

waters above the Northwind Ridge to Makarov Basin

(Wheeler and others, 1996). Productivity is lower in the

Chukchi Sea and the Eurasian Basin. Plankton productivity

depends on ice conditions, as well as nutrients. The higher

surface-water productivity of the Amerasian Basin is

probably related to the increased nutrient concentration of

the inflowing Pacific water (Wheeler and others, 1996,

1997). On the Arctic shelves, increased productivity is

reflected in the benthic biomass (Grebmeier, 1993), but it is

unclear whether it would be reflected by an increased

benthic biomass in deeper water. 

Even if Amerasian Basin surface-water productivity is

high, the flux of organic matter to the deeper portions of the

Arctic Ocean is not well known. It is probable that shallow

organic material is transported from the shelf into the basins

incorporated in brines. In addition, vertical transport of primary organic material is also increased over oceanographic

fronts such as shelf breaks or the one identified between

Lomonosov Ridge and Mendeleyev Ridge (Springer and

McRoy, 1993; Anderson and others, 1994; Swift and others,

1997). At this time, measurements of benthic biomass in the

deep Arctic are in a preliminary stage. Clough and others

(1997) indicated that at most stations studied, a significant

portion of the biomass consists of foraminifers and values

for benthic biomass are highest on the shelves and decrease

in the basin. The values for the deep basins are low when

compared with values for other ocean basins but are only a

first approximation in an area where there is variability of

the biomass due to the episodic and seasonal nature of food

influx (Clough and others, 1997).

Figure 3. Temperature profiles (solid lines) and salinity profiles

(dashed lines) from Hydrocast stations H93-13 (Northwind Ridge),

H93-21 and H93-22 (central Canada Basin), and H93-26 (eastern

Canada Basin). Station locations are shown in figure 2. Data were

collected by the shipboard party as described by Grantz and others

(1993). ASW, Arctic Surface Water; AIW, Arctic Intermediate

Water; CBDW, Canada Basin Deep Water, a type of Arctic Deep

Water.

-2 -1 0 1 2 3 4

28 36

Temp. (°C)

Salinity (‰)

-2 -1 0 1 2 3 4

28 36

0

Temp. ( °C)

Salinity (‰)

H-93-13 H-93-21 H-93-26

-2 -1 0 1 2 3 4

28 36

Temp. (°C)

Salinity (‰)

-2 -1 0 1 2 3 4

28 36

Temp. ( °C)

Salinity (‰)

H-93-22

CBDW

AIW

ASW

WATER DEPTH, IN METERS 2,000

3,000

4,000

1,000
INTRODUCTION 7

PREVIOUS FORAMINIFERAL STUDIES OF THE 

ARCTIC OCEAN

Modern deepwater benthic foraminifers have been

reported from several studies of the Arctic Ocean. Green

(1960) and Lagoe (1977, 1980) reported on the T-3 core

tops of the Alpha Ridge and the Canada and Chukchi

Basins. Scott and Vilks (1991), Bergsten (1994), Wollenburg (1995), and Wollenburg and Mackensen (1998)

described the benthic foraminifers from the Eurasian Basin,

and Ishman and Foley (1996) reported on the modern

benthic foraminiferal distributions of the Northwind Ridge

and Canada Basin. Studies of foraminifers from Arctic continental shelves include those by Loeblich and Tappan

(1953), Todd and Low (1967), Vilks (1989), SchröderAdams and others (1990), Hald and Steinsund (1996),

Steinsund and others (in press), and many others.

Green (1960) studied foraminifers (>63 μm) collected

between 433 and 2,760 mwd from the continental slope of

Ellesmere Island and the Alpha Ridge. He recognized that

most species occur at all depths but established four depth

zonations where certain species were abundant. The shelf

assemblage was characterized by Cassidulina teretis, the

slope fauna by Valvulineria arctica, the apron fauna by

Eponides tumidulus (=Ioanella tumidula of this study), and

the abyssal fauna by Eponides tener (=Oridorsalis

umbonatus of this study). 

Lagoe (1977) examined the benthic foraminiferal

fauna (>63 μm) in 118 samples between 1,069 and 3,812

mwd from the Alpha Ridge and the Chukchi and Canada

Basins and correlated foraminiferal assemblages primarily

with water masses (Lagoe, 1980). Samples collected

beneath Arctic Surface Water contain agglutinated foraminifers or calcareous species. Agglutinated foraminifers are

also found in association with the upper portion of the Arctic Intermediate Water, but deeper samples of the AIW are

characterized by C. teretis. Foraminifers of the Arctic Deep

Water include Stetsonia horvathi, E. tener, E. tumidulus, V.

arctica, and Planulina wuellerstorfi (=Fontbotia wuellerstorfi of this study).

Scott and Vilks (1991) presented benthic foraminiferal

counts (>63 μm) from several ice island stations, including

LOREX (fig. 2) (across the Lomonosov Ridge from

Amundsen Basin to Makarov Basin), Fram II (Amundsen

Basin off the Morris Jesup Rise), Fram III (Svalbard Continental Slope to Nansen Basin), CESAR (Alpha Ridge), and

T-3 (Canada Basin). Their study differs from all the other

work in that the samples were prepared and counted to

ensure high numbers of agglutinated foraminifers. Scott and

Vilks (1991) reported that deepwater (>3,600 mwd) samples

contained an average of 44 percent Stetsonia arctica (which

includes S. horvathi and Epistominella arctica in this study,

see taxonomic notes in appendix). In addition, Scott and

Vilks (1991) reported a previously unrecognized occurrence

of deepwater agglutinated foraminifers.

Bergsten (1994) reported on the recent benthic foraminifers (>63 μm) in 18 samples collected in a transect

from the Yermak Plateau to the Lomonosov Ridge and

found the deep Eurasian Basin to be dominated by S. arctica

(average 77 percent). At intermediate depths (500 to 2,000–

2,500 mwd), foraminiferal assemblages contain species

common in the North Atlantic, including O. umbonatus and

P. wuellerstorfi. The transition from intermediate to deep

water is interpreted to occur between 2,000 and 2,500 mwd

in the eastern Arctic Ocean (Bergsten, 1994). This transition

is below the depth of the core of AIW, which was reported

by Swift and others (1997) to be between 200 and 900 mwd.

However, Bergsten (1994) believed that it is reasonable to

expect Atlantic fauna to the depth of 2,500 m in the eastern

Arctic given the sill depth of the Fram Strait at 2,600 m.

Wollenburg (1995) and Wollenburg and Mackensen

(1998) reported on two size fractions—those >63 μm and

>125 μm—of living and total benthic foraminifers in 50

multicore top samples in the Eurasian and Makarov Basins.

In contrast to all other researchers, Wollenburg (1995)

believed that the foraminiferal distribution is controlled primarily by productivity in the Arctic Ocean and less by

depth, currents, or water masses. 

Wollenburg and Mackensen (1998) reported seven factor assemblages based on living assemblages (>125 μm).

However, most assemblages occur in only a few widely

spaced samples. The assemblages are listed below:

1. The Lobatula lobatula assemblage is found associated with strong currents and coarse sediments in

<500 mwd along the Svalbard/Barents Sea Shelf. 

2. The C. teretis assemblage is found between 500

and 1,400 mwd along the Svalbard margin and

Morris Jesup Rise and is believed to correspond to

increased phytodetritus flux and low current

activity. 

3. The F. wuellerstorfi assemblage occurs between

1,500 and 3,000 mwd along the Amerasian side of

the Lomonosov Ridge and is believed to be related

to food availability. 

4. From 1,500 to 3,000 mwd on the Morris Jesup

Rise and the Lomonosov Ridge, the I. tumidula

assemblage is related to competition and food

supply.

5. An assemblage containing O. tener (=O.

umbonatus of this study) and Triloculina frigida

occurs between 2,000 and 3,600 mwd and relates

to food availability and competition. Wollenburg

and Mackensen (1998) showed O. tener on the

Gakkel Ridge and T. frigida at the toe of the slope

along the Morris Jesup Rise and the Svalbard

margin. 

6 & 7. The deepest water of the Eurasian Basin has two

agglutinated assemblages containing several primitive and attached forms that were not included in

our study. 
8 DISTRIBUTION OF BENTHIC FORAMINIFERS (>125 μm) IN THE SURFACE SEDIMENTS OF THE ARCTIC OCEAN

Table 2. Rank and percentage of major benthic foraminifer species in two size fractions (>63 μm and >125 μm) of five samples from a

previous study of the Arctic Ocean.

[mwd, meters water depth; N, number of foraminifers counted; dash (—), species not present. Data and species names from Foley and Ishman (1993). Samples are from surface sediments of box cores. Species counts of samples >125 μm differ slightly from data presented in tables 4 and 5 because of taxonomic

reassignments indicated in the footnotes]

Ishman and Foley (1996) reported on 22 samples from

the Chukchi Shelf and Plateau, Northwind Ridge, Canada

Basin, and Beaufort Shelf; they discussed benthic foraminifers in the >125-μm size fraction. Data for the >63-μm fractions of some of the samples are provided in Foley and

Ishman (1993). Table 2 shows five samples that were

counted at two different sieve sizes (Foley and Ishman,

1993) and gives the most abundant species in rank of abundance as well as percentage occurrence. Cluster analysis of

the samples (>125 μm) resulted in the recognition of three

biofacies determined by water-mass properties (Ishman and

Foley, 1996). The Textularia spp. and Spiroplectammina

biformis biofacies occurred between 48 and 201 mwd. Intermediate-depth samples (401 to 1,190 mwd) are dominated

by the C. teretis biofacies. The deepest samples (893–3,811

mwd) are composed of the O. tener and E. tumidulus

biofacies. 

METHODS

This report describes the modern benthic foraminiferal

distribution in surface sediment samples from 49 box cores

from 48 to 4,180 mwd in the Arctic Ocean (fig. 1, table 1).

The samples were collected during three cruises: the

USCGC Polar Star in 1992 and 1993 and the USCGC Polar

Sea in 1994 (Aagaard and others, 1996; Ishman and Foley,

1996; Wheeler, 1997). The 1992 cruise collected box cores

from the Chukchi Shelf, Northwind Ridge, and Chukchi

Plateau. The 1993 cruise collected box cores from the

Northwind Ridge, Canada Basin, and continental shelf and

slope of the Beaufort Sea. Twenty-two samples from 1992

and 1993 have been previously reported (Ishman and Foley,

1996). The 1994 cruise collected samples in a transect from

the Chukchi Sea to the Nansen Basin (Travis, 1994;

Aagaard and others, 1996); they provide data on an area of

the Arctic Ocean not previously discussed. This report

includes the results from all three cruises.

92-B17 92-B7 92-B8 92-B15 92-B12

402 mwd

Chukchi Plateau

1,055 mwd

Northwind Ridge

1,402 mwd

Northwind Ridge

2,135 mwd

Chukchi Basin

3,811 mwd

Canada Basin

Foraminifer

>63 μm

(N=849)

Rank %

>125 μm

(N=312)

Rank %

>63 μm

(N=922)

Rank %

>125 μm

(N=363)

Rank %

>63 μm

(N=1,464)

Rank %

>125 μm

(N=334)

Rank %

>63 μm

(N=1,177)

Rank %

>125 μm

(N=342)

Rank %

>63 μm

(N=261)

Rank %

>125 μm

(N=75)

Rank %

Cassidulina norcrossi1 ................ 9 0.6 5 1.6 — — — — — — — —

Cassidulina teretis ...................... 1 66.4 1 81.4 2 20.5 2 29.5 5 3.9 2 6.9 — — — —

Cibicides lobatulus2 ................... 4 2.6 3 3.2 — — — — 6 5.2 — — —

Eponides tumidulus3.................... — — 1 23.8 6 3.3 3 22.8 4 3.6 2 21.6 4 2.6 3 23.8 2 10.7

Fontbotia wuellerstorfi ............... — — 8 1.6 5 4.1 7 2.5 3 6.6 3 11.5 2 39.5 — —

Globocassidulina 

subglobosa4............................. 2 15.7 2 8.6 — — — — — — — —

Nodosariids ................................. 7 1.2 3 3.2 — — — — 9 2 5 2 4 3.1 2 10.7

Oridorsalis tener5 ....................... — 7 .6 3 17.4 1 32.8 2 26.2 1 72.2 1 22.4 1 44.2 1 33.3 1 73.3

Quinqueloculina akneriana6 ....... — 6 .9 6 7.8 3 19.8 — 6 2.4 8 4.1 3 8.5 — —

Stainforthia concava .................. 5 2.4 8 .3 — — — — — — — —

Stetsonia horvathi ....................... 3 7.8 — 4 10.4 — 1 32.5 — 4 11.1 — 2 28.4 —

Triloculina frigida ...................... 6 1.3 — 7 5.7 4 5.5 4 5.2 4 3.4 7 4.3 6 1.8 — 4 1.3

Trochammina 

subglobigeriniformis7 ............. 8 1 — — — — — — — 5 1.9 —

Valvulineria arctica .................... — — 5 9 7 1.9 6 3.4 7 1.5 5 10 — — —

 % of total assemblages ........... 99 99 96 97 96 97 92 99 91 96

1

Cassidulina norcrossi = Islandiella norcrossi of this report. 2Cibicides lobatulus = Lobatula lobatula of this report. 3Eponides tumidulus = Ioanella tumidula of this report. 4Specimens identified as Globocassidulina subglobosa have been reidentified as Cassidulina reniforme. 5

Oridorsalis tener = Oridorsalis umbonatus of this report. 6

Specimens identified as Quinqueloculina akneriana have been reidentified as Quinqueloculina arctica, Miliolinella subrotunda, and Triloculinella

tegminis. 7Trochammina subglobigeriniformis = Trochammina globigeriniformis of this report.
DISCUSSION 9

At most stations, a 50-cubic-centimeter subsample of

surface sediments was collected from the top of the boxcore

or subcore. Samples were not stained, and no attempt has

been made to separate live from dead specimens. In the lab,

samples were oven dried (usually overnight at <50°C),

weighed, and wet sieved at 63 μm. Samples were dry sieved

at 2,000 and 125 μm. Benthic foraminifers in the fraction

>125 μm were studied. The entire sample >125 μm was

examined, or a representative fraction containing approximately 300 foraminifers was obtained by using a microsplitter; the benthic split ratios are shown in table 3. Benthic

foraminiferal counts may differ slightly from previously

reported values (Foley and Ishman, 1993; Ishman and Foley,

1996), owing to taxonomic reassignments and additional

counts of most samples.

Numbers of sediment grains and of planktic and

benthic foraminifers per gram of sediment were calculated

from counts of the number of each occurring in a fraction of

the sample (table 3). Overall, the highest numbers of planktic and benthic foraminifers per gram in the surface samples

are found on the Mendeleyev and Northwind Ridges. The

fewest foraminifers per gram occur in the deepest samples

of the Canada and Eurasian Basins (table 3). 

RESULTS

The percentage of foraminiferal species in each sample

is presented in tables 4 and 5. It is most convenient to discuss the benthic foraminifers in two geographic areas. The

first includes the Northwind Ridge, Canada Basin, and

Beaufort Slope and Shelf; the second is the Arctic transect

from the Chukchi Shelf to the Nansen Basin.

NORTHWIND RIDGE, CANADA BASIN, AND 

BEAUFORT SLOPE AND SHELF (TABLE 4)

Diversity and abundance of foraminifers are high in the

Northwind Ridge samples but decrease with depth into the

Canada Basin. Cassidulina teretis is common to abundant in

samples from 585 to 1,055 mwd (>20 percent), and O.

umbonatus is abundant (33–93 percent) in water depths

greater than 893 m (fig. 4). Fontbotia wuellerstorfi is 2 to 15

percent in samples from water depths between approximately 1,000 and 3,500 m. Triloculina frigida (>10 percent), I. tumidula, and selected agglutinated foraminifers are

minor components in some samples from intermediate to

deep water of the Canada Basin (table 4).

The deepest Beaufort Slope sample (93-B18, 2,940

mwd) resembles samples of comparable depth on the slope

of the Northwind Ridge, but the upper three slope and shelf

samples (93-B19, 93-B20, and 93-B21) are highly variable,

with low-abundance agglutinated assemblages and higher

diversity shallow-water calcareous assemblages. The variable

nature of the foraminifers near the Canada margin reflects the

steepness of the slope and probable downslope transport.

ARCTIC TRANSECT (TABLE 5)

The Arctic transect crosses the Chukchi Shelf and

Basin, Mendeleyev Ridge, Makarov Basin, Lomonosov

Ridge, and Eurasian Basin; it ends in the Nansen Basin of

the Eurasian Basin. Chukchi Shelf samples show considerable variability, including both shallow-water calcareous

and low-abundance agglutinated benthic foraminiferal

assemblages. Cassidulina teretis occurs abundantly (30–80

percent) between 402 and 528 mwd on the Chukchi Plateau

and to 1,031 mwd on the Mendeleyev and Lomonosov

Ridges (table 5). Oridorsalis umbonatus (12–60 percent)

occurs in water deeper than 1,020 m. Fontbotia wuellerstorfi

is more abundant (19–47 percent) in the intermediate-depth

waters (1,533–2,400 mwd) of the Chukchi Basin and Mendeleyev Ridge and the northwestern slope of the

Lomonosov Ridge (fig. 5) than it is in the intermediatedepth waters of the Northwind Ridge, Canada Basin, and

Beaufort Slope and Shelf. Miliolinella subrotunda occurs

most commonly (13–26 percent) in deep to intermediate

samples (1,031–3,198 mwd) on both the Mendeleyev and

Lomonosov Ridges and to a lesser extent in the Makarov

Basin. Triloculina frigida is found throughout the Arctic

Ocean but is common to abundant (21–50 percent) in four

samples on the lower slope of the Makarov and Eurasian

Basins. Ioanella tumidula is a consistent component of the

samples from intermediate to deep water and is most abundant in the Eurasian Basin.

DISCUSSION

DEPTH ZONATION OF BENTHIC FORAMINIFERS

Because of the stratified oceanography of the Arctic

Ocean, it is not surprising that the distribution of benthic

foraminifers would be overwhelmingly controlled by depth.

We recognize four depth facies: a shelf biofacies, an intermediate-depth calcareous biofacies, a deepwater calcareous

biofacies, and a deepwater mixed calcareous/agglutinated

biofacies. However, the distribution is far from simple, and

some species appear to be responding to other influences,

including the melting of pack ice, brine formation, strong

bottom contour currents, downslope transport, and inflow of

nutrient-rich Pacific water and intermediate-depth Atlantic

water.
10 DISTRIBUTION OF BENTHIC FORAMINIFERS (>125 μm) IN THE SURFACE SEDIMENTS OF THE ARCTIC OCEAN

Table 3. Planktic foraminifers, benthic foraminifers, and sediment grains per gram in surface sediment samples (>125 μm) from

this study of the Arctic Ocean.

[The samples are from surface sediments in the box cores (table 1, fig. 1). The benthic split ratio represents the fraction of the sample used to obtain

the number of foraminifers presented in tables 4 and 5. ND, no data; planktic foraminifers and sediment grains per gram were not calculated for the

1992 samples]

Box 

core no.

Water

depth

(meters)

Sample 

dry 

wt. (grams)

No. of 

planktics 

>125 μm 

per gram

Benthic

split ratio

No. of 

benthics 

>125 μm 

per gram

No. of 

sediment 

grains 

125–2,000 

μm per gram Location name

92-B1 ................ 49 19.46 ND 1 5 ND Chukchi Sea continental shelf

92-B2 ................ 48 32.06 ND 1 4 ND Chukchi Sea continental shelf

92-B3 ................ 201 23.5 ND 1 17 ND Chukchi Sea continental shelf

92-B4 ................ 447 61.04 ND 0.125 25 ND Chukchi Sea continental slope

92-B5 ................ 585 15.65 ND 1 22 ND Northwind Ridge

92-B6 ................ 1,845 29.17 ND 0.5 85 ND Chukchi Basin

92-B7 ................ 1,055 24.52 ND 0.125 127 ND Northwind Ridge

92-B8 ................ 1,402 76.91 ND 0.0078 515 ND Northwind Ridge

92-B9 ................ 2,120 49.65 ND 0.03125 302 ND Northwind Ridge

92-B10 .............. 3,145 36.99 ND 0.03125 259 ND Northwind Ridge

92-B12 .............. 3,811 76.27 ND 1 1 ND Canada Basin

92-B15 .............. 2,135 26.42 ND 0.125 105 ND Chukchi Basin

92-B16 .............. 1,388 37.07 ND 0.0625 110 ND Chukchi Sea continental slope

92-B17 .............. 402 36.11 ND 0.0078 1,125 ND Chukchi Plateau

93-B2 ................ 893 29.97 3,981 0.125 83 254 Northwind Ridge

93-B3 ................ 1,536 14 4,325 0.125 320 706 Northwind Ridge

93-B4 ................ 1,779 39.26 12,934 0.0156 502 1,930 Northwind Ridge

93-B5 ................ 1,942 35.11 21,466 0.0156 612 4,142 Northwind Ridge

93-B7 ................ 2,476 38.69 18,967 0.03125 331 7,250 Northwind Ridge

93-B8 ................ 2,560 55.63 12,333 0.0625 241 1,224 Northwind Ridge

93-B10 .............. 3,365 35.47 6,990 0.375 25 1,386 Northwind Ridge

93-B11 .............. 3,482 27 7,918 0.5 22 6,732 Northwind Ridge

93-B12 .............. 3,818 21.12 576 1 2 73 Canada Basin

93-B14 .............. 3,842 20.65 1,547 1 4 24 Canada Basin

93-B15 .............. 3,808 26.89 1,376 1 7 18 Canada Basin

93-B16 .............. 3,680 26.46 2,384 1 7 24 Canada Basin

93-B17 .............. 3,498 29.72 2,088 1 10 26 Canada Basin

93-B18 .............. 2,940 26.78 363 1 16 461 Beaufort Sea continental slope

93-B19 .............. 2,089 21.05 0 1 2 292 Beaufort Sea continental slope

93-B20 .............. 1,190 23.34 0 1 4 4,069 Beaufort Sea continental slope

93-B21 .............. 401 38.67 0 0.375 20 2,485 Beaufort Sea continental shelf

94-B6 ................ 528 39.64 144 0.218 46 364 Chukchi Sea continental slope

94-B7 ................ 2,214 50.23 7,309 0.031 182 914 Chukchi Basin

94-B8 ................ 1,031 44.29 8,227 0.018 338 1,082 Mendeleyev Ridge

94-B12 .............. 1,609 65.9 24,848 0.016 290 3,035 Mendeleyev Ridge

94-B16 .............. 1,533 62.18 22,276 0.02 172 1,498 Mendeleyev Ridge

94-B17 .............. 2,217 53.34 5,730 0.089 75 212 Mendeleyev Slope

94-B19 .............. 2,400 63.73 9,453 0.047 120 691 Mendeleyev Slope

94-B20 .............. 3,110 61.97 11,359 0.063 94 1,042 Makarov Basin

94-B21 .............. 3,193 49.11 10,682 0.125 103 751 Makarov Basin

94-B23 .............. 3,475 78.82 7,306 0.125 32 819 Makarov Basin

94-B24 .............. 3,890 75.8 7,434 0.25 16 1,568 Makarov Basin

94-B25 .............. 2,125 116.75 5,926 0.033 87 6,729 Lomonosov Slope

94-B26 .............. 1,020 60.06 8,666 0.01 563 3,890 Lomonosov Ridge
DISCUSSION 11

Table 3. Planktic foraminifers, benthic foraminifers, and sediment grains per gram in surface sediment samples (>125 μm) from

this study of the Arctic Ocean—Continued.

Box 

core no.

Water

depth

(meters)

Sample 

dry 

wt. (grams)

No. of 

planktics 

>125 μm 

per gram

Benthic

split ratio

No. of 

benthics 

>125 μm 

per gram

No. of 

sediment 

grains 

125–2,000 

μm per gram Location name

94-B28.............. 1,990 53.14 4,651 0.125 59 405 Lomonosov Slope

94-B30.............. 3,930 44.9 2,197 1 3 198 Eurasian Basin/Amundsen Basin

94-B31.............. 4,180 46.57 2,301 1 5 154 Eurasian Basin/Amundsen Basin

94-B32.............. 3,450 64.09 9,033 0.125 61 4,236 Eurasian Basin/Gakkel Ridge

94-B33.............. 3,940 61.14 6,139 0.5 15 885 Eurasian Basin/Nansen Basin

WATER DEPTH, IN METERS

0 50 100 048 0 10 20 30

C. teretis V. arctica M. subrotunda F. wuellerstorfi I. tumidula T. frigida O. umbonatus select agglutinated

species 

0 30 60 0 5 10 15 0 25 50 0 50 100 0 25 50

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

0

Figure 4. Percentages of selected benthic foraminifer species

>125 μm in samples from the Arctic Ocean plotted by water depth.

The data are from all samples in tables 4 and 5. The shelf biofacies

is not indicated in this figure. Due to the variable nature of this

assemblage, many of the species occurring in this biofacies are not

included in this figure. The horizontal lines are the boundaries

between the intermediate-depth calcareous biofacies (500–1,100

meters water depth, mwd), deepwater calcareous biofacies (1,100–

3,500 mwd), and deepwater mixed calcareous/agglutinated biofacies (>3,500 mwd).
12 DISTRIBUTION OF BENTHIC FORAMINIFERS (>125 μm) IN THE SURFACE SEDIMENTS OF THE ARCTIC OCEAN

SHELF BIOFACIES

The samples collected on the Beaufort and Chukchi

Continental Shelves (<500 mwd) have an extremely variable faunal composition (tables 4 and 5). Assemblages are

dominated by either calcareous or agglutinated foraminifers

and have variable abundance and diversity. The changing

compositions of both the shelf sediments and the Arctic Surface Water are affected by seasonal melt of pack ice, brine

formation, reworking of sediment by pack ice, and other

shelf processes and are responsible for the heterogeneous

nature of the foraminifers on the shelf (Lagoe, 1980; Polyak,

1990; Schröder-Adams and others, 1990; Ishman and Foley,

1996). 

In spite of the heterogeneity, we combine the shallowwater assemblages into a shelf biofacies, which is clearly

distinguishable from intermediate and deeper water

biofacies. The shelf biofacies contains shallow-water agglutinated foraminifers including Trochammina spp.,

Recurvoides scitulus, Saccammina difflugiformis, Adercotryma glomerata, and Saccorhiza ramosa. Some typical

calcareous species of the shelf biofacies include Islandiella

norcrossi, Elphidium spp., and Cassidulina reniforme. Shelf

species that are found in deeper water are assumed to have

been transported either by ice rafting or downslope transport

(Reimnitz and others, 1992). 

We detect no relationship between ice cover and the

occurrence of agglutinated foraminifers on the shelf, as

reported by Lagoe (1980). It is probable that ice conditions

on the continental shelves fluctuate on decadal scales (Carmack, 1990; Aagaard and Carmack, 1994), whereas the foraminiferal faunas in our samples accumulated during

hundreds to thousands of years and therefore represent conditions averaged over longer intervals (see dates in table 1). 

 INTERMEDIATE-DEPTH CALCAREOUS BIOFACIES

Away from the influence of ASW on the continental

shelves, the foraminiferal distribution is strongly correlated

with depth. In water depths between 500 and 1,100 m, the

intermediate-depth calcareous biofacies contains abundant

C. teretis, along with common Valvulineria arctica (fig. 4).

The distribution of C. teretis corresponds to the influx of

Atlantic water into the Arctic Ocean at intermediate depth.

Northwind Ridge to

Canada Basin

0 10%

M. subrotunda

0

1,000

2,000

3,000

4,000

WATER DEPTH, IN METERS

0 10 20%

F. wuellerstorfi

Chukchi Shelf to

Lomonosov Ridge

0 10 20 30 40 50%

F. wuellerstorfi

0 10 20 30%

M. subrotunda

0

1,000

2,000

3,000

4,000

WATER DEPTH, IN METERS

Figure 5. Percentages of two benthic foraminifer species >125

μm in samples from two different geographic areas of the Arctic

Ocean—Northwind Ridge to Canada Basin (table 4) and the Chukchi Shelf to the Lomonosov Ridge (table 5)—plotted by water

depth. Both Fontbotia wuellerstorfi and Miliolinella subrotunda

are intermediate-depth species that occur more abundantly in the

region of the Chukchi Sea to the Lomonosov Ridge than in the

region of the Northwind Ridge and Canada Basin. There are no

reported occurrences of these species in less than 500 meters water

depth, and these species do not occur in the Beaufort Slope region.
DISCUSSION 13

The “ring” of C. teretis between 500 and 1,100 mwd

throughout the Arctic has been recognized in earlier studies

(Polyak, 1990; Bergsten, 1994; Wollenburg, 1995; Ishman

and Foley, 1996) and is evident in the data of Green (1960)

and Lagoe (1977). Although the exact controls of Atlantic

water on C. teretis are not understood, an abundance of this

species may be a good long-term indicator of Atlantic water

at a particular site.

DEEPWATER CALCAREOUS BIOFACIES

The deepwater calcareous biofacies occurs in water

depths from 1,100 to 3,500 m. In this biofacies, O.

umbonatus is abundant, and it dominates the assemblages in

many of our samples (which are >125 μm). Other calcareous species that are common in our deepwater calcareous

biofacies include Miliolinella subrotunda, I. tumidula, T.

frigida, and F. wuellerstorfi (tables 4 and 5, fig. 4). 

An abundance of O. umbonatus in the deep water of

the Arctic Ocean has also been recognized in previous studies (for example, those by Green, 1960; Lagoe, 1977, 1980;

Ishman and Foley, 1996). In studies that used the >63-μm

fraction, S. horvathi is reported to dominate in deepwater

samples (Scott and Vilks, 1991; Bergsten, 1994). However,

a large percentage of E. tener (=O. umbonatus of this study)

was also recorded by Lagoe (1977) in the >63-μm fraction.

Figure 6 shows a plot of Lagoe’s (1977) data that records up

to 33 percent of the foraminifer fauna consisting of O.

umbonatus between 1,069 and 3,812 mwd in the Canada

Basin. It is significant that this species constitutes a significant percentage of the assemblage even at the smaller size

fraction. This fact can also be seen in the size-fraction study

of Foley and Ishman (1993; see this report, table 2). 

DEEPWATER MIXED CALCAREOUS/AGGLUTINATED 

BIOFACIES

Agglutinated benthic foraminifers occur in two different environments in the Arctic. As discussed above, on the

Chukchi and Beaufort Shelves, the shelf biofacies contains

a shallow-water agglutinated assemblage including Trochammina spp., R. scitulus, S. difflugiformis, A. glomerata,

and S. ramosa. However, in the deepest water samples of the

Canada, Makarov, and Eurasian Basins, a different agglutinated assemblage occurs. The deepwater (>3,500 mwd)

mixed calcareous/agglutinated biofacies consists of

Reophax nodulosus and Hyperammina elongata, along with

assorted calcareous species. A similar deepwater agglutinated assemblage was recognized in the Amundsen Basin

by Scott and Vilks (1991) and was correlated with turbidite

activity there. These tubular foraminifers either are transported by turbidity currents or are early colonizers in areas

of turbidites (Schröder, 1988).

Partial to total loss of the calcareous fauna through dissolution can result in a relative increase in the amount of

agglutinated foraminifers (Murray and Alve, 1994).

Increased dissolution is consistent with the fact that the

deepwater agglutinates occur in Arctic Basin samples having low totals of calcareous benthic foraminifers (tables 4

and 5). Selective dissolution of some calcareous fauna in the

Arctic Ocean basins could result from a buildup of carbon

dioxide (CO2) due to low temperatures, great water depths,

and slow deepwater overturning. Deepwater residence time

is estimated to range from 150 years in the Eurasian Basin

to >400 years in the Amerasian Basin (Östlund and others,

1987; Macdonald and others, 1993; Schlosser and others,

1995). Therefore, decreases in calcareous foraminifers and

relative increases in agglutinated foraminifers are consistent

with increased calcium carbonate dissolution in the deep

Arctic basins.

Other possibilities for the low numbers of benthic foraminifers per gram in samples from the Canada, Makarov,

and Eurasian Basins could be lower foraminiferal productivity or dilution of the fauna by sediment accumulating at a

high rate. Heavy ice cover would limit productivity and

result in lower foraminiferal numbers but would result in

lower sediment accumulation from melting ice rafts. Neither decreased productivity nor decreased ice rafting would

result in increased numbers of agglutinated foraminifers. On

the other hand, increased sedimentation in the form of turbidites might result in higher numbers of tubular agglutinated benthic foraminifers and might decrease the total

numbers of foraminifers per gram by sediment dilution

(Schröder, 1988). However, previous evidence indicates that

the sedimentation rates of the Canada Basin are very low

(Clark and others, 1980). Most likely a combination of low

productivity, turbidite sedimentation, and increased dissolution is responsible for the origin of the deepwater mixed calcareous/agglutinated biofacies.

Furthermore, there is an interesting difference in the

calcareous foraminifers in the deep mixed biofacies of the

Canada, Makarov, and Eurasian Basins. The Canada Basin

contains the deepwater calcareous species O. umbonatus.

The Eurasian Basin, on the other hand, contains a higher

percentage of shallow-water species such as Haynesina germanica, Buccella spp., Cassidulina reniforme, and various

Elphidium spp. (tables 6 and 7). In fact, our samples from

the Eurasian and Makarov Basins contain the largest percentage of shallow-water calcareous species, whereas the

Canada Basin contains the smallest percentage. The processes for the transport of shallow-water species into deep

water are ice rafting and downslope transport. The heavy ice

cover of the Canada Basin most likely provides the explanation for the decreased percentage of ice-rafted shelf fauna,

whereas high percentages of shelf fauna are expected in the

Eurasian and Makarov Basins beneath the Transpolar drift

of pack ice (Reimnitz and others, 1992).
14 DISTRIBUTION OF BENTHIC FORAMINIFERS (>125 μm) IN THE SURFACE SEDIMENTS OF THE ARCTIC OCEAN

However, the amount of ice rafting alone cannot fully

explain the differences seen in the Arctic. For example, a high

percentage of shelf species occurs in the deepest parts of both

the Eurasian and Makarov Basins, but lower values occur on

the Lomonosov Ridge and Gakkel Ridge (table 7). It is

unlikely that the amount of ice rafting would vary significantly over this geographic area, especially considering the

position of the Transpolar drift of pack ice over these sites

(Reimnitz and others, 1992). We propose that the amounts of

ice-rafted foraminifers are fairly uniform over the Arctic,

except in the Canada Basin, where they are lower. Higher values of shelf species in the Eurasian and Makarov Basins are

probably the result of downslope transport of shelf species via

turbidity currents. This interpretation is supported by the

increased abundance of tubular foraminifers in both basins

(Schröder, 1988). Further discussion of this evidence is in the

section below on “Distribution of Triloculina frigida.”

DISTRIBUTION OF FONTBOTIA WUELLERSTORFI

In our study, the highest concentration of Fontbotia

wuellerstorfi (19–47 percent) occurs in the area from the

Northwind Ridge to the western Lomonosov Ridge between

1,533 and 2,400 mwd (fig. 5), and the highest values are on

the Mendeleyev Ridge (average 24 percent). Elsewhere in

the Amerasian Basin, this species occurs in smaller percentages (0.3–18 percent) between 893 and 3,498 mwd (tables 4

and 5). Fontbotia wuellerstorfi does not occur in the Canada

Basin below 3,498 mwd and is absent from the Eurasian

Basin (3,450–4,180 mwd). Other reports of F. wuellerstorfi

in the Amerasian Basin include from 740 to 2,760 mwd on

the Alpha Ridge (Green, 1960; Lagoe, 1975, 1977; Scott

and others, 1989) and from 1,570 to 1,980 mwd on the west

side of the Lomonosov Ridge (Scott and Vilks, 1991; Wollenburg, 1995; Wollenburg and Mackensen, 1998). 

0 5 10 15%

C. teretis

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

WATER DEPTH, IN METERS

0 5 10 15 20%

V. arctica

0 5 10 15%

F. wuellerstorfi

0 10 20 30 40%

O. tener

0 10 20 30%

T. frigida

Figure 6. Percentages of selected benthic foraminifer species

>63 μm in samples from the Chukchi Basin, Alpha Ridge, and

Canada Basin plotted by water depth. Data are from Lagoe (1977),

who did not report sample data from less than 1,069 meters water

depth. Oridorsalis tener of Lagoe (1977) is equivalent to Oridorsalis umbonatus of this report.
DISCUSSION 15

Fontbotia wuellerstorfi appears to have its distribution

partially controlled by depth, and it occurs throughout the

Arctic Ocean between 900 and 3,500 mwd. However, the

distribution is modified by some other process that causes

the species to be most abundant in the Amerasian Basin,

specifically in the area of the Mendeleyev Ridge (fig. 5).

Bergsten (1994) suggested that F. wuellerstorfi is controlled

by Atlantic water, whereas Wollenburg (1995) believed that

this species responds primarily to food supply. Polyak

(1990) reported that F. wuellerstorfi is related to relatively

mobile water between 1,500 and 2,400 mwd. 

The oceanography of the Arctic Ocean is far from completely understood, and the foraminiferal distribution may

supply additional information about the oceanography. Evidence of a strong temperature front in the intermediatedepth water over the Lomonosov Ridge indicates that Atlantic water is not exchanged over the central Lomonosov

Ridge (Anderson and others, 1994). Instead, Atlantic water

travels along the slope to cross the ridge just north of the

Russian Continental Slope and enters the Makarov Basin

between 500 and 1,500 mwd (Östlund and others, 1987;

Swift and others, 1997). In the Amerasian Basin, the Atlantic layer presumably mixes with denser shelf brines to form

the relatively warm and saline Canada Basin Deep Water,

which is recognized exiting the Amerasian Basin across the

Morris Jesup Rise of the Greenland continental margin

(Östlund and others, 1987; Anderson and others, 1994). The

increased abundance of F. wuellerstorfi on the western

Lomonosov Ridge and in the Makarov Basin appears to be

related to this path of Atlantic water, which is at a deeper

bathymetric interval than previously suspected. Fontbotia

wuellerstorfi is an epibenthic suspension feeder that prefers

elevated habitats and is tolerant of sediments having low

contents of organic matter (Altenbach and Sarnthein, 1989).

Colonization of elevated substrates allows F. wuellerstorfi to

capture suspended food from passing currents. The geographic distribution of F. wuellerstorfi in the Arctic Ocean

suggests that this foraminifer may be responding to the

organic matter that is transported by an intermediate-depth

current.

Wollenburg (1995) reported that productivity and the

availability of food are the main controls on the distribution

of benthic foraminifers in the Arctic Ocean. However,

because of the spatial and temporal variability of food supply to the Arctic benthos, it is unlikely that productivity

alone can explain the occurrence of species such as F. wuellerstorfi, as proposed by Wollenburg and Mackensen

(1998). Although local productivity and food supply are

obviously important to the Arctic Ocean benthos, the transport of organic matter by ocean currents, as discussed

above, appears to be more important in explaining the

observed foraminiferal distributions over the long term. 

Our studies also suggest a similar Amerasian Basin

occurrence for the species Miliolinella subrotunda, with a

preference for the intermediate waters of the Northwind

Ridge to Makarov Basin (fig. 5). However, the preferences

of this common species, given the confused taxonomy (see

taxonomic notes in appendix), are unclear. The study of

geographic preferences of several Arctic Ocean benthic foraminifers, including M. subrotunda, is currently in progress.

DISTRIBUTION OF TRILOCULINA FRIGIDA 

Another trend observed in our data is the common

occurrence (>20 percent) of Triloculina frigida in four

deepwater samples of both the Makarov and Eurasian

Basins (3,475–3,940 mwd). Triloculina frigida occurs with

significant percentage (>7 percent) in additional samples on

the Chukchi Plateau at 1,388 mwd, on the Northwind Ridge

and in the Canada Basin from 2,120 to 3,498 mwd, and on

the Mendeleyev Ridge/Makarov Basin from 1,606 to 3,198

mwd. Because T. frigida occurs in the Eurasian Basin,

where F. wuellerstorfi is absent, it appears to be related to

different environmental conditions. Triloculina frigida

could be responding strictly as an indicator of intermediate

to deep water, ranging from 1,388 to 3,940 mwd with maximum abundance occurring from 3,475 to 3,940 mwd. However, it is the abundance (21–50 percent) in certain samples

that is not easily explained. Triloculina frigida was first

identified by Lagoe (1977) and has been reported in small

percentages throughout the Arctic. It appears to be closely

related to Triloculina trihedra and Triloculina tricarinata

and has sometimes been misidentified as such, but it is

clearly a distinct species (see taxonomic notes in appendix). 

Triloculina frigida has been reported in bathyal to

abyssal depths of the Norwegian Sea (Sejrup and others,

1981; Mackensen, and others, 1985) and the Gulf of Alaska

(Bergen and O’Neil, 1979, as T. trihedra). Scott and Vilks

(1991, as T. trihedra) and Wollenburg (1995) reported up to

18 percent at the base of the Svalbard margin (3,675 mwd),

and Lagoe (1977) reported up to 26 percent in the Canada

Basin (fig. 6). Examination of our data suggests that the

samples where T. frigida occurs most commonly are characterized by increased currents or downslope transport. Several lines of evidence suggest this. 

First, T. frigida is more widespread geographically

than F. wuellerstorfi, and this difference suggests that the

distribution is not related to water masses alone. Most

occurrences of T. frigida are concentrated along the lower

slope and rise, and the maximum abundance is at the base of

both sides of the Lomonosov Ridge and along the Svalbard

margin. It has been reported that strong bottom contour currents sweep past the Svalbard margin (site 94-B33) and

along the base of the Lomonosov Ridge (site 94-B30) in the

Eurasian Basin (Aagaard and Carmack, 1994). This strong

current activity would likely cause erosion but may transport organic material as well.

Second, most of our samples containing T. frigida also

contain the tubular agglutinated foraminifer Hyperammina.
16 DISTRIBUTION OF BENTHIC FORAMINIFERS (>125 μm) IN THE SURFACE SEDIMENTS OF THE ARCTIC OCEAN

Large tubular foraminifers have been documented to occur

in continental marginal settings in areas of currents or

downslope transport (Schröder, 1988; Gooday and others,

1997). Scott and Vilks (1991) reported high occurrences of

Hyperammina at the base of the Lomonosov Ridge, which

is believed to be an area of downslope transport. Most of

their samples that contain high abundance of Hyperammina

also contain small percentages of T. frigida (Scott and Vilks,

1991). However, the greatest values of T. frigida reported by

Scott and Vilks (1991) occur at the base of the Morris Jesup

Rise, an area swept by contour currents (Aagaard and Carmack, 1994). In our samples, almost all occurrences of

tubular agglutinated foraminifers are marked by an increase

in the percentage of T. frigida. 

Third, our samples with high values of T. frigida (94-

B23, B24, B30, B31, and B33) also contain numerous shallow-water species, including C. reniforme, H. germanica,

Elphidium spp., and Buccella frigida (tables 6 and 7). The

occurrence of these species suggests transport of shelf sediment, either by ice rafting or by turbidites. Ice rafting of shelf

fauna is common in the Arctic Ocean (Wollenburg, 1995), but

T. frigida has not been reported in any shallow-water samples

(Loeblich and Tappan, 1953; Todd and Low, 1967; Vilks,

1989; Steinsund and others, in press), so it is unlikely that

ice rafting is responsible for the distribution of both T.

frigida and the shallow-water species in these samples. As

discussed above in the section “Deepwater Mixed Calcareous/Agglutinated Biofacies,” the higher abundance of shallow-water species in the deeper samples of the Eurasian

Basin probably relates to downslope transport. Samples that

contain the highest abundance of T. frigida also contain

higher percentages of shelf species. This relationship even

holds true in the perennially ice covered Canada Basin, suggesting that the rare occurrences of shelf species in the Canada Basin are also deposited by downslope transport. 

These occurrences of T. frigida throughout the Arctic

Ocean suggest that T. frigida is a species that prefers the

lower slope and rise and may tolerate the transported sediments that are often found there. Turbidites commonly have

high contents of transported shallow-water organic matter,

which may make them desirable for food in the ice-covered

central Arctic. If T. frigida prefers this type of habitat, that

preference may explain its occurrence on the slope of both

the Canada and Eurasian Basins in areas that are susceptible

to both strong contour currents and downslope transport of

sediments.

THE QUESTION OF SIEVE SIZE

Concerns have been expressed that, because Arctic foraminifer species are small, the analysis of only the >125-μm

fraction will result in the loss of biologic data, as well as

valuable oceanographic information (Scott and Vilks, 1991).

Data presented on both size fractions—>63 μm and

>125 μm—indicate that smaller species are indeed underrepresented in, or even absent from, the >125-μm fraction

(Foley and Ishman, 1993; see this report, table 2). However,

the goal of our study was to understand the past and present

oceanography of the Arctic Ocean through the study of foraminifers and not necessarily to complete a detailed taxonomic assessment.

To determine the effect of sieve size on the data set, we

selected five samples that were analyzed at multiple sieve

sizes by Foley and Ishman (1993; see this report, table 2).

Table 2 includes one sample from each of our biofacies and

one sample from the Chukchi Basin in the region where F.

wuellerstorfi is more abundant. The data presented in table 2

include the most abundant species in rank of abundance, as

well as the percentage occurrence for the two sieve fractions

(Foley and Ishman, 1993). In all samples, the small species

Stetsonia horvathi is present (8–33 percent) in the >63-μm

fraction and absent from the >125-μm fraction. However,

the loss of this species does not significantly alter the interpretation of the data. Stetsonia horvathi is the dominant

(rank 1) species in only one sample (>63 μm, 92-B8, 33 percent), and, in that sample, it is followed closely by the second ranking species, O. umbonatus (26 percent). 

In three of the samples (92-B17, 92-B15, and 92-B12),

the same species is dominant in both size fractions: C. teretis for the shallow sample and O. umbonatus for the two

deeper samples. Table 2 suggests that significant information is not lost by using only the larger size fraction and that

the same depth biofacies (shelf, intermediate-depth calcareous, deepwater calcareous, and deepwater mixed calcareous/agglutinated biofacies) are recognizable regardless of

the size fraction used. 

Table 2 does indicate some differences in the data sets.

The most disparity between the two size fractions occurs

with the species Ioanella tumidula; however, it still remains

in the top six most abundant species even in the larger size

fraction (table 2). Therefore, it should be recognized that a

small percentage of this species in the >125-μm fraction is

more significant than other species. In summary, we feel

that the use of the >125-μm fraction in this study does not

invalidate the overall conclusions presented in this report.

The same depth and environmental biofacies are recognizable, although possibly composed of slightly different species, and regardless of the sieve size used, the same

oceanographic trend is discerned. 

SUMMARY

Benthic foraminifers (>125 μm) in surface sediment

samples of box cores provide information about the oceanography of the Arctic Ocean. Four depth-controlled biofacies are recognized, which are modified by other

oceanographic processes. The shelf biofacies is represented
REFERENCES CITED 17

by variable foraminiferal faunas found in samples from the

Beaufort and Chukchi Continental Shelves. Some shelf

samples contain shallow-water calcareous species, whereas

others contain low-diversity agglutinated species. This distribution is most likely related to the variable substrate and

surface-water processes occurring on the Arctic shelves

(Carmack, 1990; Aagaard and Carmack, 1994).

The intermediate-depth calcareous biofacies, found

between 500 and 1,100 mwd, contains abundant Cassidulina

teretis and is apparently associated with Atlantic-water influence in the Arctic Intermediate Water. The exact nature of this

relationship is still unclear. A deepwater calcareous biofacies

includes an abundance of Oridorsalis umbonatus between

1,100 and 3,500 mwd. A deepwater (>3,500 mwd) mixed calcareous/agglutinated biofacies results from low productivity,

selective carbonate dissolution in the deepest Arctic basins,

the input of shelf foraminifers by downslope transport, and, to

a lesser extent, ice rafting.

This study recognizes that the species Fontbotia wuellerstorfi has a depth range of 900 to 3,500 mwd throughout

the Arctic. Within this depth range, F. wuellerstorfi exhibits

a geographic preference for the Amerasian Basin, with the

highest values of F. wuellerstorfi (>24 percent) occurring on

the Mendeleyev Ridge from 1,500 to 2,400 mwd. We suggest that the distribution of F. wuellerstorfi is related to a

branch of Atlantic water that crosses the Lomonosov Ridge

near the Russian Continental Shelf. This current may redistribute organic matter to intermediate-depth benthos.

The most abundant and diverse benthic foraminifer

assemblages occur in the region from the Northwind to

Mendeleyev Ridges and may result from the high surfacewater productivity of this area. In contrast, lower foraminiferal diversity and abundance in the Canada and Eurasian

Basins are probably related to low productivity, turbidite

sedimentation, and increased carbonate dissolution. Turbidite-transported shallow-water foraminifer species compose

a significant portion of the assemblage in the samples from

the Makarov and Eurasian Basins. 

Finally, Triloculina frigida is recognized to be a species preferring lower slope sediments affected by downslope

transport and strong contour currents in both the Eurasian

and Amerasian Basins. Identification of this species in older

sediments may indicate areas of downslope transport or episodes of more vigorous bottom circulation.

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and biota in the Northwest Passage and implications for

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circulation in the transport of contaminants: Deep-Sea

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Scott, D.B., Mudie, P.J., Baki, V., MacKinnon, K.D., and Cole,

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Sejrup. H.-P., Fjaeran, Tor, Hald, Morten, Beck, Lennart, Hagen,

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production: Continental Shelf Research, v. 13, p. 575–599.

Steinsund, P.I., Polyak, L., Hald, M., Mikhaylov, M., and Karsun,

S., in press, Distribution of calcareous benthic Foraminifera

in recent sediments of the Barents and Kara Seas: Journal of

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Swift, J.H., Jones, E.P., Aagaard, K., Carmack, E.C., Hingston, M.,

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TABLES 4–7 AND APPENDIX 19

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TABLES 4–7 AND APPENDIX
20 DISTRIBUTION OF BENTHIC FORAMINIFERS (>125 μm) IN THE SURFACE SEDIMENTS OF THE ARCTIC OCEAN

Table 4. Percentages of benthic foraminifers >125 μm in samples from the Northwind Ridge area, Canada Basin, and

Beaufort area.

[Only general locations are given here; specific locations are in table 1 and figure 1. The transition between the Northwind Ridge and the

Canada Basin is gradual. To save space, dashes following collection year were dropped from sample numbers; for example, sample 92-B5

in table 1 is 92B5 in this table. Asterisks (*) indicate agglutinated foraminifers; all others are calcareous foraminifers]

Northwind Ridge area

Water depth (meters) ............................ 585 893 1,055 1,402 1,536 1,779 1,942 2,120 2,476 2,560

Box core number .................................. 92B5 93B2 92B7 92B8 93B3 93B4 93B5 92B9 93B7 93B8

Adercotryma glomerata*............................... 0 0 0 0 0 0 0 0 0 0 

Ammodiscus catinus * ................................... 0 0 0 0 0 0 0 0 0 0 

Buccella arctica............................................. 0 0 0 0 0 0 0 0 0 0 

Buccella frigida ............................................. 0 0 0 .97 0 .32 0 0 0 .24 

Cassidulina reniforme ................................... 0 .32 .52 0 .18 .65 .60 .43 .25 0 

Cassidulina teretis......................................... 21.10 27.30 29.38 6.47 4.64 1.95 .30 0 0 0 

Cornuspira involvens..................................... 0 0 .26 0 .18 0 0 0 0 0 

Dentalina spp. ............................................... 0 0 .26 .32 0 0 0 0 0 0 

Elphidium albiumbilicatum ........................... 0 0 0 0 0 0 0 0 0 0 

Elphidium excavatum .................................... 0 0 .26 .32 0 0 0 0 0 0 

Elphidium subarcticum.................................. .29 0 .77 0 0 0 0 0 0 .12 

Fontbotia wuellerstorfi .................................. 0 .63 0 2.91 15.36 5.84 11.01 5.76 3.49 9.76 

Glandulina laevigata..................................... 0 0 0 0 0 0 0 0 0 0 

Glomospira gordialis *.................................. 1.45 0 0 0 0 0 0 .21 0 0 

Haynesina germanica.................................... 0 0 0 0 0 0 0 0 0 .36 

Hyperammina elongata * .............................. 0 0 0 0 0 0 0 0 0 0 

Ioanella tumidula .......................................... 0 2.86 3.09 3.56 .18 .32 .30 1.28 .25 1.07 

Islandiella norcrossi ...................................... 0 0 0 0 0 0 0 0 0 0 

Laminononion stellatum................................ 0 0 0 0 0 0 0 0 0 0 

Lobatula lobatula .......................................... 0 .95 .77 0 0 0 0 0 0 0 

Melonis barleeanus ....................................... .58 0 0 0 0 0 0 0 0 0 

Miliolinella subrotunda ................................. 0 1.59 1.03 3.56 10.18 .97 0 2.35 0 .24 

Nodosariids.................................................... .87 .32 1.55 .65 1.79 .97 0 .43 .25 .60 

Nonionella labradorica ................................. 0 0 0 0 0 0 0 0 0 0

Oridorsalis umbonatus .................................. .29 41.59 33.76 72.49 55.54 83.44 79.46 80.38 93.27 85.00 

Patellina corrugata........................................ 0 0 0 0 .18 0 0 0 0 0 

Portatrochammina bipolaris *....................... 2.60 0 0 0 0 0 0 0 0 0 

Pyrgo murrhina ............................................. 0 0 0 0 0 0 0 .21 .75 .12 

Pyrgo williamsoni.......................................... 0 .95 .77 0 .54 0 0 0 0 0 

Quinqueloculina arctica................................ .87 3.17 10.57 .32 6.07 .65 2.38 .85 .50 0 

Quinqueloculina sp. B................................... 0 0 .52 0 0 0 0 0 0 0 

Recurvoides scitulus * ................................... 17.92 4.44 1.55 0 0 0 0 0 0 0 

Reophanus oviculus *.................................... 0 0 0 0 0 0 0 0 0 .12 

Reophax guttifer * ......................................... 10.40 0 0 .65 0 0 0 0 0 0 

Reophax nodulosus *..................................... 1.16 0 0 0 0 0 0 0 0 0 

Robertinoides charlottensis........................... 0 0 .52 .65 .18 0 0 .21 0 0 

Saccammina difflugiformis * ......................... 17.34 0 0 0 0 0 0 0 0 0 

Saccorhiza ramosa * ..................................... 10.12 0 0 0 0 0 0 0 0 0 

Stainforthia concava...................................... 0 0 0 0 0 0 0 0 0 0 

Stetsonia horvathi.......................................... 0 0 0 .32 0 0 0 0 0 0 

Triloculina frigida ......................................... 0 1.27 2.32 4.21 5.00 4.55 5.95 7.89 1.25 2.38 

Triloculinella tegminis................................... 0 7.94 10.31 .65 0 0 0 0 0 0 

Trochammina globigeriniformis * ................. 10.69 .32 0 0 0 0 0 0 0 0 

Trochammina sp. * ........................................ 2.89 0 0 0 0 0 0 0 0 0 

Valvulineria arctica ....................................... 0 6.03 1.80 1.94 0 .32 0 0 0 0 

Verneuilinulla advena *................................. .58 0 0 0 0 0 0 0 0 0 

Other agglutinated * ...................................... .87 0 0 0 0 0 0 0 0 0 

Other calcareous ............................................ 0 .32 0 0 0 0 0 0 0 0 

Total number of foraminifers.................... 346 315 388 309 560 308 336 469 401 840
TABLE 4 21

Table 4. Percentages of benthic foraminifers >125 μm in samples from the Northwind Ridge area, Canada 

Basin, and Beaufort area—Continued.

Canada Basin Beaufort area

2,940 3,145 3,365 3,482 3,498 3,680 3,808 3,811 3,818 3,842 2,089 1,190 401

93B18 92B10 93B10 93B11 93B17 93B16 93B15 92B12 93B12 93B14 93B19 93B20 93B21

 0 0 0 0 0 0 0 0 0 0 10.87 9.68 6.32

 .70 0 0 0 .34 00000 17.39 0 4.56

 0 0 0 0 0 .52 .05 0 0 0 0 0 0

 0 0 0 .66 0 .52 0 1.19 00000

 0 .67 0 .33 0000 2.38 0 0 0 .35

 0 0 0 .66 0 0 0 0 0 0 0 2.15 4.56

 0 0 0 0 0 0 0 0 0 0 0 0 0

 .23 0 .30 .33 .34 00000000

 0 1.00 0 0000000000

 0 1.00 1.50 .99 0 0 0 1.19 0 0 0 2.15 0

 0 .67 .30 .66 0 .52 0 0 2.38 0000

 8.39 2.34 7.49 8.25 .34 00000000

 0 2.01 0 000000000 1.40

 0 0 0 0 0 0 0 0 0 0 30.43 0 0

 0 0 .30 .33 .34 0 0 0 0 0 0 0 .35

 0 0 0 0 .34 3.14 4.52 0 4.76 15.48 0 70.97 0

 .23 4.68 6.29 .99 6.48 13.61 .50 9.52 2.38 4.76 0 0 0

 0 0 0 0 0 0 0 0 0 0 0 0 0

 0 0 0 0 0 0 0 0 0 0 0 0 0

 0 0 0 0 0 0 0 0 0 0 0 0 0

 0 0 0 0 0 0 0 0 0 0 0 0 2.11

 0 1.00 0 0000 1.19 4.76 0000

 .23 .33 3.29 7.59 7.85 4.19 3.52 10.71 16.67 11.90 0 1.08 1.05

 0 0 0 0 0 0 0 0 0 0 0 0 54.74

 84.85 77.26 64.07 58.42 70.99 65.97 59.80 73.81 52.38 58.33 0 0 0

 0 0 0 0 0 0 0 0 0 0 0 0 0

.23 0 0 0 1.02 .52 3.02 0 0 0 4.35 4.30 4.91

 0 1.34 2.69 2.31 000000000

 0 0 0 0 0 0 0 0 0 0 0 0 0

 0 0 0 0 0 0 0 0 0 0 0 0 0

 0 0 0 0 0 0 0 0 0 0 0 0 0

 2.80 0 0 0000000 21.74 0 0

 0 0 0 0 0 0 0 0 2.38 0 0 2.15 4.21

 0 0 0 0 0 0 0 0 0 0 8.70 0 0

 1.17 0 0 0 1.02 9.42 25.13 0 7.14 5.95 0 0 0

 0 0 0 0 0 0 0 0 0 0 0 0 0

 0 0 0 0 0 0 0 0 0 0 0 0 0

 0 0 0 0 0 0 0 0 0 0 0 0 0

 0 0 0 0 0 0 0 0 0 0 0 0 5.61

 0 0 0 0 0 0 0 0 0 0 0 0 0

 .23 7.36 13.77 18.48 10.92 1.57 3.02 1.19 4.76 3.57 0 0 0

 0 0 0 0 0 0 0 0 0 0 0 0 0

 .93 0 0 0 0 000000 4.30 0

 0 0 0 0 0 0 0 0 0 0 0 0 0

 0 0 0 0 0 0 0 0 0 0 0 0 0

 0 0 0 0 0 0 0 0 0 0 2.17 0 0

 0 0 0 0 0 0 0 1.19 0 0 4.35 3.23 8.77

 0 .33 0 000000000 1.05

429 299 334 303 293 191 199 84 42 84 46 93 285
22 DISTRIBUTION OF BENTHIC FORAMINIFERS (>125 μm) IN THE SURFACE SEDIMENTS OF THE ARCTIC OCEAN

Table 5. Percentages of benthic foraminifers >125 μm in samples from the Arctic transect from the Chukchi Shelf to

the Eurasian Basin.

[Only general locations are given here; specific locations are in table 1 and figure 1. To save space, dashes following collection year were

dropped from sample numbers; for example, sample 92-B2 in table 1 is 92B2 in this table. Asterisks (*) indicate agglutinated foraminifers; all others are calcareous foraminifers]

Chukchi Shelf Chukchi Slope Chukchi Basin

 Water depth (meters) ..................... 48 49 201 402 447 528 1,388 1,845 2,135 2,214

Box core number ............................ 92B2 92B1 92B3 92B17 92B4 94B6 92B16 92B6 92B15 94B7

Adercotryma glomerata *..................... 0 0 8.38 0 1.60 0 0 0 0 0 

Ammodiscus catinus * .......................... 0 0 .25 0 0 0 0 0 .29 0 

Buccella arctica.................................... 0 0 0 0 0 0 0 0 0 0 

Buccella frigida .................................... 1.60 5.21 1.52 0 0 0 0 .08 0 .35 

Cassidulina reniforme .......................... .80 3.13 7.87 10.09 0 2.99 .39 .16 0 0 

Cassidulina teretis................................ 0 0 4.82 80.13 0 49.25 5.91 .08 0 0 

Cornuspira involvens............................ 0 0 0 0 0 0 0 0 0 0 

Dentalina spp. .................................... 0 0 0 0 0 0 0 .97 0 0 

Elphidium albiumbilicatum .................. 0 1.04 1.02 0 0 0 0 0 0 .70 

Elphidium excavatum ........................... 23.20 57.29 12.69 0 0 1.24 0 0 .29 0 

Elphidium subarcticum......................... 0 0 0 0 0 0 0 0 0 0 

Fontbotia wuellerstorfi ......................... 0 0 0 0 0 0 7.09 31.02 39.19 47.20 

Glandulina laevigata............................ .80 3.13 0 0 0 0 0 0 0 0 

Glomospira gordialis *......................... 0 0 0 0 0 .25 .79 .57 0 0 

Haynesina germanica........................... .80 3.13 0 0 0 0 0 .16 0 0 

Hyperammina elongata * ..................... 0 0 0 0 1.07 0 0 0 0 0 

Ioanella tumidula ................................. 0 0 0 0 0 0 2.36 3.07 2.59 1.40 

Islandiella norcrossi ............................. 0 0 47.72 0 0 .25 0 0 0 0 

Laminononion stellatum....................... 0 0 .76 0 0 .25 0 0 0 0 

Lobatula lobatula ................................. 0 0 0 3.15 0 0 0 0 0 0 

Melonis barleeanus .............................. 0 0 6.85 .32 0 0 0 0 0 0 

Miliolinella subrotunda ........................ 0 0 0 0 0 0 9.45 0 7.20 0 

Nodosariids........................................... 0 0 1.52 3.15 0 1.00 2.76 1.86 2.02 .35 

Nonionella labradorica ........................ 0 1.04 2.03 0 0 0 0 0 0 0 

Oridorsalis umbonatus......................... 0 0 0 .63 0 0 56.69 51.29 43.52 49.30 

Patellina corrugata............................... 0 0 0 0 0 0 0 0 0 0 

Portatrochammina bipolaris *.............. 0 0 0 0 8.56 4.48 0 .73 0 0 

Pyrgo murrhina .................................... 0 0 0 0 0 0 0 0 0 0 

Pyrgo williamsoni................................. 0 0 .76 0 0 0 0 .08 .29 0 

Quinqueloculina arctica....................... 0 0 .25 .95 0 0 3.15 .40 .86 0 

Quinqueloculina sp. B.......................... 0 0 0 0 0 0 0 0 0 0 

Recurvoides scitulus * .......................... 0 0 0 .95 5.88 7.96 0 3.63 0 0 

Reophanus oviculus *........................... 0 0 0 0 0 .25 0 .48 0 0 

Reophax guttifer * ................................ 0 0 0 0 4.81 2.49 0 0 0 0 

Reophax nodulosus *............................ 0 0 0 0 3.21 3.23 0 .48 0 0 

Robertinoides charlottensis.................. 0 0 .25 0 0 0 1.18 0 1.44 0 

Saccammina difflugiformis * ................ 1.60 1.04 1.02 .32 19.25 2.99 0 0 0 0 

Saccorhiza ramosa * ............................ 0 0 0 0 42.78 15.42 0 0 0 0 

Stainforthia concava............................. 0 0 .51 .32 0 .25 0 0 0 0 

Stetsonia horvathi................................. 0 0 0 0 0 0 0 .32 0 0 

Triloculina frigida ................................ 0 0 0 0 0 .50 7.87 1.94 2.02 0 

Triloculinella tegminis.......................... 0 0 0 0 0 1.24 0 .65 0 .70 

Trochammina globigeriniformis * ........ 0 0 0 0 9.63 4.23 0 .32 0 0 

Trochammina sp. * ............................... 0 0 .25 0 .53 .75 0 .16 0 0 

Valvulineria arctica .............................. 0 0 0 0 0 1.00 2.36 1.29 0 0 

Verneuilinulla advena *........................ 3 .20 10.42 .25 0 1.60 0 0 .24 0 0 

Other agglutinated * ............................. 68.00 14.58 .25 0 1.07 0 0 0 0 0 

Other calcareous ................................... 0 0 1.02 0 0 0 0 0 .29 0 

Total number of foraminifers............ 125 96 394 317 187 402 254 1,238 347 286
TABLE 5 23

Table 5. Percentages of benthic foraminifers >125 μm in samples from the Arctic transect from the Chukchi Shelf to the Eurasian

Basin—Continued.

Mendeleyev Ridge Makarov Basin Lomonosov Ridge Eurasian Basin

1,031 1,609 1,533 2,217 2,400 3,110 3,193 3,475 3,890 2,125 1,020 1,990 3,930 4,180 3,450 3,940

94B8 94B12 94B16 94B17 94B19 94B20 94B21 94B23 94B24 94B25 94B26 94B28 94B30 94B31 94B32 94B33

 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

 .38 0 0 0 0 .28 0 .32 .68 0 .30 0 1.42 .85 .41 1.35 

 .38 0 0 .85 0 0 0 .63 1.02 0 0 .51 4.96 2.14 0 2.25 

 31.56 .33 1.91 0 0 0 0 0 0 0 47.88 0 0 0 0 0 

 0 0 0 .28 0 0 0 0 0 0 .30 0 0 0 0 0 

 1.14 1.34 0 0 0 1.10 0 .32 .68 0 .30 0 2.13 2.14 0 .45 

 0 0 .48 0 2.51 2.20 1.75 4.13 5.46 .32 .30 1.78 13.48 7.26 4.28 9.89 

 .76 0 .96 2.27 0 .28 1.27 .63 2.39 1.26 .61 0 4.96 2.14 1.22 2.25 

 0 0 0 .28 .56 .28 .48 .32 1.37 0 0 0 9.93 6.41 0 2.92 

 1.52 18.73 21.05 24.08 30.08 9.92 6.35 2.86 0 29.97 .30 4.06 0 0 0 0 

 0 0 0 0 0 0 0 0 .34 0 0 0 0 0 .61 .22 

 0 0 0 0 .28 0 .16 .32 0 .32 0 0 0 0 0 0 

 0 0 0 0 1.11 0 0 2.54 5.12 .32 0 1.27 4.26 9.83 2.85 3.37 

 0 0 0 0 0 .55 0 1.90 2.73 .32 .30 0 14.18 26.50 0 5.39 

 5.70 4.68 6.70 7.37 3.34 8.26 8.57 12.38 2.73 8.52 .91 6.09 0 0 13.44 2.25 

 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

 0 0 0 0 0 0 0 0 0 0 .30 0 0 0 0 0 

 0 0 0 0 0 0 0 0 .34 0 0 0 0 0 0 0 

 20.15 17.73 26.79 22.10 18.66 19.28 13.33 0 0 18.61 24.24 19.80 0 0 .41 0 

 .38 2.01 2.87 2.55 1.11 3.58 0 4.13 13.99 2.21 1.21 3.05 20.57 13.25 2.44 8.99 

 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

 31.94 39.46 23.92 32.01 33.15 43.53 59.84 34.60 26.28 29.97 12.42 60.41 0 0 67.62 .90 

 0 0 1.91 0 0 0 0 0 0 .95 .30 0 0 0 .20 0 

 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

 0 0 0 .85 0 0 0 0 0 0 0 0 0 0 0 0 

 0 0 7.18 2.27 1.39 0 0 .32 0 .32 5.76 0 0 0 0 0 

 0 .33 .96 .28 0 0 0 0 0 .63 0 .51 0 .43 0 0 

 0 0 0 0 0 0 0 0 0 0 1.52 0 0 0 0 0 

 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

 0 0 0 0 0 0 0 0 .34 0 0 0 0 22.22 0 6.29 

 0 .67 0 1.13 3.06 1.65 .63 0 0 1.26 0 .25 0 0 0 0 

 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

 0 0 0 .28 0 0 0 0 0 0 .30 0 0 0 0 0 

 0 0 0 0 0 0 0 0 1.02 0 0 .25 0 0 0 2.92 

 1.52 14.05 5.26 2.55 4.74 9.09 7.62 34.60 35.15 5.05 1.82 1.52 21.28 5.56 6.52 49.66 

 0 0 0 0 0 0 0 0 0 0 0 .51 0 0 0 0 

 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

 0 0 0 0 0 0 0 0 .34 0 0 0 .71 .43 0 0 

 4.56 .67 0 .85 0 0 0 0 0 0 .91 0 0 0 0 .22 

 0 0 0 0 0 0 0 0 0 0 0 0 2.13 .85 0 0 

 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 .67 

263 299 209 353 359 363 630 315 293 317 330 394 141 234 491 445
24 DISTRIBUTION OF BENTHIC FORAMINIFERS (>125 μm) IN THE SURFACE SEDIMENTS OF THE ARCTIC OCEAN

Table 6. Percentages of selected shallow-water benthic foraminifers >125 μm in samples from the Northwind Ridge

area, Canada Basin, and Beaufort area.

[Only general locations are given here; specific locations are in table 1 and figure 1. The transition between the Northwind Ridge and

Canada Basin is gradual. To save space, dashes following collection year were dropped from sample numbers; for example, sample 92-

B5 in table 1 is 92B5 in this table]

Table 7. Percentages of selected shallow-water benthic foraminifers >125 μm in samples from the Arctic transect from the Chukchi

Shelf to the Eurasian Basin.

[Only general locations are given here; specific locations are in table 1 and figure 1. To save space, dashes following collection year were dropped from

sample numbers; for example, sample 92-B2 in table 1 is 92B2 in this table]

Northwind Ridge area

Water depth (meters) ......................... 585 893 1,055 1,402 1,536 1,779 1,942 2,120 2,476 2,560

Box core number ............................... 92B5 93B2 92B7 92B8 93B3 93B4 93B5 92B9 93B7 93B8

Buccella arctica ..................................... 0000000000

 Buccella frigida ...................................... 0 0 0 .97 0 .32 0 0 0 .24

Cassidulina reniforme ........................... 0 .30 .52 0 .18 .65 .60 .43 .25 0

 Elphidium albiumbilicatum .................... 0000000000

Elphidium excavatum ............................ 0 0 .26 .32 000000

Elphidium subarcticum .......................... .30 0 .77 0 0 0 0 0 0 .12

Haynesina germanica ............................ 0 0 0 0 0 0 0 0 0 .36

Islandiella norcrossi .............................. 0000000000

Laminononion stellatum ........................ 0000000000

 Lobatula lobatula .................................. 0 1 .77 0000000

Total % shallow species ...................... .30 1.30 2.32 1.29 .18 .97 .60 .43 .25 .72

Total number of foraminifers .............. 346 315 388 309 560 308 336 469 401 840

Chukchi Shelf Chukchi Slope Chukchi Basin Mendeleyev Ridge

Water depth (meters) ................ 48 49 201 402 447 528 1,388 1,845 2,135 2,214 1,031 1,609

Box core number ...................... 92B2 92B1 92B3 92B17 92B4 94B6 92B16 92B6 92B15 94B7 94B8 94B12

Buccella arctica................................. 00000000000 0

Buccella frigida ................................. 1.60 5.20 1.52 0 0 0 0 .08 0 .35 .38 0

Cassidulina reniforme ....................... .80 3.10 7.87 10.10 0 2.99 .39 .16 0 0 .38 0

Elphidium albiumbilicatum............... 0 1.00 1.02 0 0 0 0 0 0 .70 0 0

Elphidium excavatum ........................ 23 57.00 12.70 0 0 1.24 0 0 .29 0 .76 0

Elphidium subarcticum...................... 00000000000 0

Haynesina germanica........................ .80 3.10 0 0 0 0 0 .16 0 0 0 0

Islandiella norcrossi.......................... 0 0 47.70 0 0 .25 00000 0

Laminononion stellatum.................... 0 0 .76 0 0 .25 00000 0

Lobatula lobatula .............................. 0 0 0 3.15 0000000 0

Total % shallow species................. 26.20 69.40 71.57 13.25 0 4.73 .39 .40 .29 1.05 1.52 0

Total number of foraminifers........ 125 96 394 317 187 402 254 1,238 347 286 263 299
TABLE 6 25

Table 6. Percentages of selected shallow-water benthic foraminifers >125 μm in samples from the Northwind 

Ridge area, Canada Basin, and Beaufort area—Continued.

Table 7. Percentages of selected shallow-water benthic foraminifers >125 μm in samples from the Arctic transect from

the Chukchi Shelf to the Eurasian Basin—Continued.

 Canada Basin Beaufort area

2,940 3,145 3,365 3,482 3,498 3,680 3,808 3,811 3,818 3,842 2,089 1,190 401

93B18 92B10 93B10 93B11 93B17 93B16 93B15 92B12 93B12 93B14 93B19 93B20 93B21

0 0 0 0 0 .52 .50 0 0 0 0 0 0

0 0 0 .66 0 .52 0 1.19 00000

0 .67 0 .33 0 0 0 0 2.38 0 0 0 .35

0 1.00 0 0000000000

0 1.00 1.50 .99 0 0 0 1.19 0 0 0 2.15 0

0 .67 .30 .66 0 .52 0 0 2.38 0000

0 0 .30 .33 .34 0 0 0 0 0 0 0 .35

0 00 0 0 0 0 0 0 0 0 0 0

0 00 0 0 0 0 0 0 0 0 0 0

0 00 0 0 0 0 0 0 0 0 0 0

0 3.34 2.10 2.97 .34 1.56 .50 2.38 4.76 0 0 2.15 .70

429 299 334 303 293 191 199 84 42 84 46 93 285

Mendeleyev Ridge—Continued Makarov Basin Lomonosov Ridge Eurasian Basin 

1,533 2,217 2,400 3,110 3,193 3,475 3,890 2,125 1,020 1,990 3,930 4,180 3,450 3,940

94B16 94B17 94B19 94B20 94B21 94B23 94B24 94B25 94B26 94B28 94B30 94B31 94B32 94B33

0 0 0 0 0 00 0 0 0 0 0 0 0

0 0 0 .28 0 .32 .68 0 .30 0 1.42 .85 .41 1.35

0 .85 0 0 0 .63 1.02 0 0 .51 4.96 2.14 0 2.25

.48 0 2.51 2.20 1.75 4.13 5.46 .32 .30 1.78 13.50 7.26 4.28 9.89

.96 2.27 0 .28 1.27 .63 2.39 1.26 .61 0 4.96 2.14 1.22 2.25

0 .28 .56 .28 .48 .32 1.37 0 0 0 9.93 6.41 0 2.92

0 0 1.11 0 0 2.54 5.12 .32 0 1.27 4.26 9.83 2.85 3.37

0 0 0 0 0 00 0 0 0 0 0 0 0

0 0 0 0 0 00 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 .30 0 0 0 0 0

1.44 3.40 4.18 3.04 3.50 8.57 16.04 1.90 1.51 3.56 39.03 28.63 8.76 22.03

209 353 359 363 630 315 293 317 330 394 141 234 491 445
26

APPENDIX. SYSTEMATIC LIST AND TAXONOMIC NOTES FOR BENTHIC 

FORAMINIFERS >125 μm COUNTED IN THIS STUDY OF THE ARCTIC OCEAN

[This appendix provides the names of all species listed in tables 4 and 5, which are the species present in samples counted for this study; it

does not list species discussed in the text and table 2 as reported by other authors. Specimens in the National Museum of Natural History

(formerly called the United States National Museum), Smithsonian Institution, Washington, D.C., are identified by USNM catalog

number]

Adercotryma glomerata (Brady) = Lituola glomerata Brady,

1878, Annals and Magazine of Natural History (London), ser. 5, v. 1, p. 433, pl. 20, figs. 1a–c. 

Ammodiscus catinus Höglund, 1947, Zoologiska Bidrag

Fran Uppsala, v. 26, p. 122, pl. 8, figs. 1 and 7; pl. 28,

figs. 19–23; text figs. 82–84, 105–107, 109.

Buccella arctica Voloshinova, 1960, Microfauna of the

USSR, Vses. Neft. Nauchno-Issled. Geol.-Razved. Inst.

(VNIGRI, Moscow), Trudy, 1960, no. 153, sbornik 11,

pl. 8, figs. 2–4.

Buccella frigida (Cushman) = Pulvinulina frigida Cushman,

1921, Results of the Hudson Bay Expedition, 1920, 1.

The Foraminifera, Contributions to Canadian Biology,

no. 9 (1921), p. 135–147.

Cassidulina reniforme (Nørvang) = Cassidulina crassa

d’Orbigny var. reniforme Nørvang, 1945, The Zoology

of Iceland, Foraminifera, v. 2, no. 2, p. 1–79.

Cassidulina teretis Tappan, 1951, Northern Alaska Index

Foraminifera, Cushman Foundation for Foraminiferal

Research Contributions, v. 2, pt. 1, p. 7, pl. 1, fig. 30. 

Cornuspira involvens (Reuss) = Operculina involvens

Reuss, 1850, Denkschriften der Kaiserlichen Akademie

der Wissenschaften Wien Mathematisch-naturwissenschaftlichen, Classe 1, p. 370, pl. 46, fig. 30.

Dentalina spp. includes Dentalina frobisherensis Loeblich

and Tappan, 1953, Studies of Arctic Foraminifera,

Smithsonian Miscellaneous Collections, v. 121, no. 7,

p. 55, pl. 10, figs. 1–9, and Dentalina pauperata

d’Orbigny.

Elphidium albiumbilicatum (Weiss) = Nonion pauciloculum

albiumbilicatum Weiss, 1954, Foraminifera and origin

of the Gardiners clay (Pleistocene), eastern Long Island, N.Y., U.S. Geological Survey Professional Paper

254–G, p. 157, pl. 32, figs. 1–2.

Elphidium excavatum (Terquem) = Polystomella excavata

Terquem, 1876, Société Dunquerquoise, Mémoires, v.

19 (1874–75) p. 429. Note: all forma of E. excavatum

are included together in these counts.

Elphidium subarcticum Cushman, 1944, Smithsonian Miscellaneous Collections, v. 89, p. 27, pl. 3, figs. 34a, b,

35.

Epistominella arctica Green, 1960, Micropaleontology, v. 6,

no. 1, p. 71, pl. 1, fig. 4 (USNM 689643). Note: recorded very rarely in >125-μm fraction of surface samples.

See Stetsonia horvathi in this list.

Fontbotia wuellerstorfi (Schwager) = Anomalina wuellerstorfi Schwager, 1866, Fossile foraminiferen von KarNicobar, Geol. Teil, v. 2, no. 1, Geologische Beobachtungen, no. 2, Paläontologische Mitteilungen, p. 258, pl.

7, figs. 105, 107. Note: F. wuellerstorfi includes individuals identified as Planulina wuellerstorfi by Lagoe

(1977, 1980) and other authors.

Glandulina laevigata (d’Orbigny) = Nodosaria laevigata

d’Orbigny, 1826, Ann. Sci. Nat., ser. 1, v. 7, p. 252, pl.

10, figs. 1–3. 

Glomospira gordialis (Jones and Parker) = Trochammina

squamata var. gourdialis Jones and Parker, 1860, Geological Society of London Quarterly Journal, v. 16, p.

304.

Haynesina germanica (Ehrenberg) = Nonionina germanica

Ehrenberg, 1840, Koenigliche Akademie Wissenschaften, Berlin, Physik-Math., v. 11, p. 23, pl. 2, figs.

1a–g.

Hyperammina elongata Brady, 1878, Annals and Magazine

of Natural History (London), ser. 5, v. 1, p. 433, pl. 20,

figs. 2a, b.

Ioanella tumidula (Brady) = Truncatulina tumidula Brady,

1884, Rept. Voy. Challenger, v. 9 (Zoology), p. 666, pl.

95, figs. 8a–d. Note: Ioanella tumidula includes individuals identified as Eponides tumidulus by other

authors.

Islandiella norcrossi (Cushman) = Cassidulina norcrossi

Cushman, 1933, Smithsonian Miscellaneous Collections, v. 89, no. 9, p. 7, pl. 2, fig. 7. 

Laminononion stellatum (Cushman and Edwards) = Astrononion stellatum Cushman and Edwards, 1937, Astrononion, a new genus of the Foraminifera, and its

species, Contributions from the Cushman Laboratory

for Foraminiferal Research, v. 13, p. 29–36. Note: includes Astrononion gallowayi Loeblich and Tappan,

1953, in Loeblich and Tappan, 1988, Foraminiferal

genera and their classifications, p. 620, pl. 696, figs. 3,

4. 

Lobatula lobatula (Walker and Jacob) = Nautilus lobatulus

Walker and Jacob, 1789, in Kanmacher, Adam’s Essays

on the Microscope, 2d ed., chap. XI, p. 629–645, pl.

XIV. 

Melonis barleeanus (Williamson) = Nonionina barleeana

Williamson, 1858, On the Recent Foraminifera of Great

Britain, Royal Society [of London] Publication, p. 32,

pl. 3, figs. 68–69. 
APPENDIX 27

Miliolinella subrotunda (Montague) = Vermiculum subrotundum Montague, 1803. Note: Type species concept

was revised with the establishment of neotype for M.

subrotunda in 1974 by Ponder, The Foramineral Genus

Miliolinella Wiesner, 1931, and its Synonyms, Micropaleontology, v. 20, p. 197–208. Includes Pateoris

hauerinoides (Rhumbler) Loeblich and Tappan, 1953,

pl. 7, figs. 8–12. Description is quinqueloculine to

planispiral chambers with four to five (and as many as

seven) chambers visible in last whorl, rounded periphery. Terminal arched aperture is open and rarely may

have a small flap or nub, but not a large flap.

Nodosariids. Includes a variety of unilocular calcareous

benthic species.

Nonionella labradorica (Dawson) = Nonionina labradorica

Dawson, 1860, Canadian Naturalist, v. 5, p. 191, fig. 4.

Oridorsalis umbonatus (Reuss) = Rotalina umbonatus

Reuss, 1851, Zeitschrift der Deutschen Geologischen

Gesellschaft, Berlin, v. 3, p. 75, pl. 5, figs. 35a–c. Note:

O. umbonatus includes individuals identified as

Eponides tener by other authors.

Patellina corrugata Williamson, 1858, On the Recent Foraminifera of Great Britain, London, Ray Society, p. 46.

Portatrochammina bipolaris (Brady) = Haplophragmium

nanum Brady, 1881, Notes on Some of the Reticularian

Rhizopoda of the Challenger Expedition, Part III. 1.

Classification. 2. Further Notes on New Species. 3.

Note on Biloculina Mud, Quarterly Journal of Microscopical Science, new ser., v. 21, p. 50. 

Pyrgo murrhina (Schwager) = Biloculina murrhina Schwager, 1866, Geologischer Teil, v. 2, no. 1, Geologische

Beobachtungen, no. 2, Paläontologische Mitteilungen,

p. 187–268.

Pyrgo williamsoni (Silvestri) = Biloculina williamsoni Silvestri, 1923, Atti Accad. Pont. Romana Nuovi Lincei,

v. 76 (1922–23), p. 73, pl. 6, figs. 169–170.

Quinqueloculina arctica Cushman, 1933, New Arctic Foraminifera Collected by Capt. R.A. Bartlett from Fox Basin and off the Northeast Coast of Greenland,

Smithsonian Miscellaneous Collections, v. 89, no. 9, p.

2, pl. 1, figs. 3a–c. Note: illustrated as having an angular periphery with pronounced costae. However, Cushman also reported more rounded specimens (1933, p.

3). Type material shows that small specimens lack costae but have longitudinal striations. Always has a bifid

tooth. The holotype is USNM 26152; other examined

specimens are in the Cushman Collection, including

59765, 60148.

Quinqueloculina sp. B, Lagoe, 1977, Recent Benthic Foraminifera from the Central Arctic Ocean, Journal of Foraminiferal Research, v. 7, no. 2, p. 119, pl. 2, figs. 19,

20.

Recurvoides scitulus (Brady) = Haplophragmium scitulum

Brady, 1881, Üeber einige arktische Tiefsee-Foraminiferen gesammelt während der österreichisch-ungarischen Nordpol-Expedition in den Jahren 1872–74,

Denkschriften der Kaiserlichen Akademie der Wissenschaften Wien Mathematisch-naturwissenschaftlichen

Classe, v. 43, p. 50.

Reophanus oviculus (Brady) = Reophax ovicula Brady,

1879, Notes on Some of the Reticularian Rhizopoda of

the Challenger Expedition, Quarterly Journal of Microscopical Science, new ser., v. 19, p. 20–62.

Reophax guttifer (Brady) = Lituola (Reophax) guttifera

Brady, 1881, Üeber einige arktische Tiefsee-Foraminiferen gesammelt während der österreichisch-ungarischen Nordpol-Expedition in den Jahren 1872–74,

Denkschriften der Kaiserlichen Akademie der Wissenschaften Wien Mathematisch-naturwissenschaftlichen

Classe, v. 43, p. 9–110.

Reophax nodulosus Brady, 1881, Üeber einige arktische

Tiefsee-Foraminiferen gesammelt während der österreichisch-ungarischen Nordpol-Expedition in den Jahren

1872–74, Denkschriften der Kaiserlichen Akademie

der Wissenschaften Wien Mathematisch-naturwissenschaftlichen Classe, v. 43, p. 9–110.

Robertinoides charlottensis (Cushman) = Cassidulina charlottensis Cushman, 1925, Contributions from the Cushman Laboratory for Foraminiferal Research, v. 1, pt. 2,

p. 41, pl. 6, figs. 6, 7. 

Saccammina difflugiformis (Brady) = Reophax difflugiformis Brady, 1879, Notes on Some of the Reticularian

Rhizopoda of the Challenger Expedition, Quarterly

Journal of Microscopical Science, new ser., v. 19, p.

20–62.

Saccorhiza ramosa (Brady) = Hyperammina ramosa Brady,

1879, Notes on Some of the Reticularian Rhizopoda of

the Challenger Expedition, Quarterly Journal of Microscopical Science, new ser., v. 19, p. 20–62.

Stainforthia concava Höglund, 1947, Zoologiska Bidrag

Fran Uppsala, v. 26, p. 257, pl. 23, figs. 3, 4; pl. 32, figs.

4–7.

Stetsonia horvathi (Green) 1960, Ecology of Some Arctic

Foraminifera, Micropaleontology, v. 6, no. 1, p. 72, pl.

1, figs. 6a,b. Note: In this study, the taxonomic rank of

Stetsonia horvathi has been retained. Scott and Vilks

(1991) showed a gradational series between S. horvathi

and Epistominella arctica but concentrated on the inflated last chamber and did not mention the pronounced

differences in coiling that are observed both in the illustrations of Green (1960) and in the type specimens.

Stetsonia horvathi (USNM 689784) is planispiral to

slightly trochospiral, whereas E. arctica (USNM

689643) is strongly trochospiral. Until the differences

in coiling direction can also be shown to be gradational,

we propose to retain the original taxonomic division of

Green (1960).
28 DISTRIBUTION OF BENTHIC FORAMINIFERS (>125 μm) IN THE SURFACE SEDIMENTS OF THE ARCTIC OCEAN

Triloculina frigida Lagoe, 1977, Recent Benthic Foraminifera from the Central Arctic Ocean, Journal of Foraminiferal Research, v. 7, no. 2, p. 120, pl. 1, figs. 12, 17,

18, text figs. 6D, 6E. Note: described by Lagoe as differing from Triloculina trihedra (Loeblich and Tappan,

1953) by the presence of an apertural neck. Comparison

USNM collection material indicates that Triloculina

trihedra has no neck and a very distinct tooth, whereas

T. frigida ranges from having only a small neck with a

distinct tooth to having a long neck with an indistinct

tooth. Examination of several slides deposited in the

USNM and identified by Loeblich and Tappan as T. trihedra shows no specimens that could be identified as T.

frigida (holotype USNM P2110; paratypes USNM

372115 and 372116). It does not appear likely that T.

frigida is a variety of T. trihedra, although it has been

misidentified as such. Triloculina trihedra was not

identified in this study.

Triloculinella tegminis (Loeblich and Tappan) = Scutuloris

tegminus Loeblich and Tappan, 1953, Studies of Arctic

Foraminifera, Smithsonian Miscellaneous Collections,

v. 121, no. 7, p. 41, pl. 6, fig. 10; includes Miliolinella

chukchiensis (Loeblich and Tappan) 1953, pl. 7, fig. 7;

Quinqueloculina subrotunda (Montague) Todd and

Low, 1967; and Quinqueloculina subrotunda (Montague?) Cushman, 1948. Note: quinqueloculine or cryptoquinqueloculine with three to five chambers visible.

Semicircular aperture at the end of last chamber is nearly filled with a broad low flap, which leaves a slitlike

crescentic opening. Found only in shallow-water

samples.

Trochammina globigeriniformis (Parker and Jones) = Lituola nautiloidea Lamarck var. globigeriniformis Parker

and Jones, 1865, Royal Society of London Philosophical Transactions, v. 155, p. 407, pl. 17, fig. 96.

Trochammina spp. Includes a variety of unidentified species

of Trochammina.

Valvulineria arctica Green, 1960, Ecology of Some Arctic

Foraminifera, Micropaleontology, v. 6, no. 1, p. 71, pl.

1, figs. 3a–c.

Verneuilinulla advena (Cushman) = Verneuilina advena

Cushman, 1922, Results of the Hudson Bay Expedition,

1920, 1. The Foraminifera, Contributions to Canadian

Biology, no. 9 (1921), p. 141.
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Osterman and others—DISTRIBUTION OF BENTHIC FORAMINIFERS (>125 μm), ARCTIC OCEAN—U.S. Geological Survey Bulletin 2164

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