Stein et al 1994.pdf

E L S E V I E R Marine Geology 119 (1994) 269 285

MARINE GEOLOGY

INTERNATIONAL JOURNAl. OF MARINE GEOLOGE GEOCHEMISTRY AND GEOPHYSICS

Organic carbon, carbonate, and clay mineral distributions in eastern central Arctic Ocean surface sediments

Ruediger Stein, Hannes Grobe, Monika Wahsner Alfred- Wegener-Institute for Polar and Marine Research, Columbusstrafle, D-27515 Bremerhaven, Germany

(Received January 27, 1993; revision accepted October 20, 1993)

Abstract

Results from a detailed sedimentological investigation of surface sediments from the eastern Arctic Ocean indicate that the distribution of different types of sediment facies is controlled by different environmental processes such as sea-ice distribution, terrigenous sediment supply, oceanic currents, and surface-water productivity.

In comparison to other open-ocean environments, total organic carbon contents are high, with maximum values in some deep-basin areas as well as west and north of Svalbard. In general, the organic carbon fraction is dominated by terrigenous material as indicated by low hydrogen index values and high C/N ratios, probably transported by currents and/or sea ice from the Eurasian Shelf areas. The amount of marine organic carbon is of secondary importance reflecting the low-productivity environment described for the modern ice-covered Arctic Ocean. In the area north of Svalbard, some higher amounts of marine organic matter may indicate increased surface-water productivity controlled by the inflow of the warm Westspitsbergen Current (WSC) into the Arctic Ocean and reduced sea-ice cover. This influence of the WSC is also supported by the high content of biogenic carbonate recorded in the Yermak Plateau area.

The clay mineral distribution gives information about different source areas and transport mechanisms. Illite, the dominant clay mineral in the eastern central Arctic Ocean sediments, reaches maximum values in the Morris-Jesup- Rise area and around Svalbard, indicating North Greenland and Svalbard to be most probable source areas. Kaolinite reaches maximum values in the Nansen Basin, east of Svalbard, and in the Barents Sea. Possible source areas are Mesozoic sediments in the Barents Sea (and Franz-Josef-Land). In contrast to the high smectite values determined in sea-ice samples, smectite contents are generally very low in the underlying surface sediments suggesting that the supply by sea ice is not the dominant mechanism for clay accumulation in the studied area of the modern central Arctic Ocean.

1. Introduction

Although it is generally accepted that the Arctic Ocean (Fig. 1) is a very sensitive and important region for changes in the global climate, this region is the last major physiographic province of the earth whose short- and long-term geological history is not very well known. Since the first recovery and description of deep-sea sediments during the famous 1893-1896 Fram-Expedition of Fridtjof Nansen (Nansen, 1897; B6ggild, 1906), the progress in getting a better understanding of the Arctic

0025-3227/94/$7.00 © 1994 Elsevier Science B.V. All rights reserved SSDI 0025-3227 ( 9 4 ) 0 0 0 4 0 - R

Ocean system and its relationship to global change has been slow in comparison to studies in other ocean regions. This lack of knowledge is mainly caused by the major technological/logistic prob- lems in reaching this permanently ice-covered region with normal research vessels and in retriev- ing long and undisturbed sediment cores. The available samples and data from the central Arctic Basins are derived mainly from drifting ice islands such as T-3 (e.g., Clark et al., 1980) and CESAR (Jackson et al., 1985). In the eastern Arctic Basins, ship expeditions such as Ymer 80 (Fig. 2; Bostr6m

270 R. Stein et al./Marine Geology 119 (1994) 269-285

Fig. 1. Surface-water circulation systems in the Arctic Ocean and occurrences of major coal deposits in the surrounding continents (from Bischof et al., 1990, based on Anon, 1978; Hale, 1990), supplemented by probable source areas of clay minerals in the Arctic Ocean. Letters/, K and S indicate the major clay mineral in a chlorite-illite-kaolinite-smectite association (based on Darby, 1975; Naidu and Mowatt, 1983; Dalrymple and Maass, 1987; Elverhoi et al., 1989).

and Thiede, 1984) and Polarstern ARK-IV/3 (Fig. 2; Thiede, 1988) have greatly advanced our knowledge on Arctic Ocean paleoenvironments. Comprehensive summaries about the present knowledge on Arctic Ocean geology are given by Herman (1989), Bleil and Thiede (1990) and Grantz et al. (1990).

In 1991, an international and multidisciplinary three-ship expedition (Arctic 91) has been carried out by the swedish Oden, the american Polar Star, and the German Polarstern. During this very suc- cessful expedition into the extreme central Arctic Ocean area it was possible to recover onboard Polarstern unique undisturbed surface sediments and long sediment cores from the Nansen, Amundsen, and Makarov Basins, the Gakkel and

Lomonosov Ridges, and the Morris-Jesup Rise and the Yermak Plateau (Fig. 2; F~tterer, 1992). The major objective of the Arctic 91 marine geology program is to study the paleoclimatic and paleoceanographic evolution of the Arctic Ocean and its influence on the global (paleo-)environment, including topics such as changes in lithogenic, biogenic, and organogenic sediment supply during glacial/interglacial cycles, glacial/interglacial variations in sea-ice cover, and water-mass exchange between the Arctic and Atlantic Oceans, its global relevance and change through time. In this paper, we present results from a study of surface sediments taken during the 1991 Polarstern Expedition (FOtterer, 1992; Rachor, 1992) to point out the relationship

R. Stein et al./Marine Geology 119 (1994) 269-285 271

160 ° 140 ° 120 °

75 °

75 ~

0 °

Fig. 2. Positions of surface sediment samples considered in the distribution maps of Figs. 3, 6 and 7. Sample positions are marked by triangles: Ymer-80 Expedition (Bostr6m and Thiede, 1984); open squares=Polarstern Expedition ARK-IV/3 (Thiede, 1988); circles=Polarstern Expedition ARK-VIII/2 (Rachor, 1992); and dots=Polarstern Expedition ARK-VIII/3 (ARCTIC '91) (FOtterer, 1992).

between modern environmental processes and sediment accumulation in the eastern central Arctic Ocean.

2. Modern oceanography and environment

Today, two major current systems are domina- ting the surface-water circulation in the Arctic

Ocean: the anticyclonic Beaufort Gyre in the Amerasian Basin and the Transpolar Drift in the Eurasian Basin (Fig. 1). The latter, crossing our study area, is transporting sea ice from the Siberian shelf areas through the central Arctic to the Fram Strait. Through Fram Strait, two major currents exchange water between the Arctic and the world ocean (Fig. 1). The cold, ice-transporting East

272 R. Stein et al./Marine Geology 119 (1994) 269~85

Greenland Current is the main current out of the Arctic Ocean. On the other hand, the Westspitsbergen Current, an extension of the North Atlantic-Norwegian Current, carries warm, relatively saline water into the Arctic Ocean where it cools down and extends in intermediate water depths into the eastern Arctic Basins (Aagard et al., 1985; Carmack, 1990). Of importance for the thermohaline circulation in the Arctic Ocean is the formation of brines on polar shelves, i.e., cold, saline, and well-oxygenated water masses which sink over the continental margin into the deep basins (Aagard et al., 1985). The export of sea ice through Fram Strait and its melt in the Greenland Norwegian Sea as well as the deep- water exchange between Arctic and Atlantic seem to play an important role in controlling the deep- water formation in the northern North Atlantic and, thus, is of global significance (Untersteiner and Carmack, 1992).

Another important phenomenon of the Arctic Ocean is the permanent sea-ice cover with its strong seasonal variation in the marginal (shelf) areas. This sea-ice cover has a distinct influence on marine biota, oceanic circulation, and surface albedo, which all are major controls on climatic change. Although mean primary productivity of the central Arctic Ocean is very low because of the sea-ice cover, productivity might be very high at the ice edge because of supply of nutrients during melting phases and ice edge upwelling, resulting in phytoplankton blooms (Subba Rao and Platt, 1984; Sakshaug and Skjoldal, 1989). Since surface-water productivity may affect the concentration of atmospheric CO2 (i.e., in areas of high production rate of organic matter, the ocean may act as a sink for CO2) which is an important factor controlling the global climate, the quantification of the organic carbon budget in the Arctic Ocean is also of major significance for understanding the global climate system.

A large proportion of the sea ice is "dirty ice" containing high amounts of sediment (Pfirman et al., 1989; Wollenburg 1991; Ftitterer, 1992; Nt~rnberg et al., 1994-this volume). Most of the sediment is incorporated into the sea ice in the Siberian shelf areas and then transported as ice- rafted debris (IRD) through the central Arctic

Ocean via the Transpolar Drift (Wollenburg, 1991). In areas of extensive melting, sediment particles are released and deposited at the sea floor. In these areas, this process may dominate the supply and accumulation of terrigenous material in the polar environment. Icebergs are another possibility for transportation of terrigenous material into the central Arctic, but are very rare today due to the absence of large ice shelves. Source areas for icebergs today are Ellesmere Island, North Greenland, Svalbard, Franz-Josef Land, and Severnaya Zemlya (Sudgen, 1982; Darby et al., 1989). A detailed study of the composition and grain size of the siliciclastic sediment fractions might give an important key to distinguish between different source areas and transport mechnisms (see below).

3. Methods

During Polarstern cruises ARK-VIII/2 and ARK-VIII/3 (Arctic 91), surface and near-surface samples were taken by means of giant box corer (GKG) and multicorer (MUC), and long sediment cores were taken by a kastenlot corer, a giant piston corer, and a gravity corer (Ft~tterer, 1992; Rachor, 1992). Cores were collected from about 60 geological stations in the eastern Arctic Ocean (Fig. 2). On these sediments, a detailed sedimentological and geochemical investigation program has been started. Data produced on the surface sediments (0-1 cm) are presented and discussed in this paper.

Total carbon, total nitrogen, and total organic carbon contents were determined on ground bulk samples and HCl-treated carbonate-free samples, respectively, using a HERAEUS CHN analyser and a LECO-CS analyser. Carbonate contents were calculated as:

(total carbon-total organic carbon) × 8.333

Rock-Eval pyrolysis was performed according to the method described by Espitali6 et al. (1977). Kerogen microscopy was performed on polished, epoxy-impregnated blocks of sediment; the macer- als were classified according to the nomenclature described by Stach et al. (1982).


Samples used for grain size (of the carbonate- free sediment fraction) and clay mineral analyses were treated with acetic acid to dissolve the carbonate, oxidized and disaggregated by means of a 3-10% H 2 0 2 solution, and wet-sieved through a 63 #m sieve. From the <63/~m fraction, the silt (2-63/~m) and clay (<2/~m) fractions were sepa- rated using settling tubes ("Atterberg method"; Mfiller, 1967). From the clay fraction, texturally- oriented specimens were produced by vacuum filtration through a filter of 0.15/~m pore size (Lange, 1982). These specimens were then ana- lyzed by means of a Philips 1700 X-Ray diffraction system with a cobalt K~-radiation. The measure- ments were performed on untreated and glycolated (18 hours at 60°C) samples, both from 2 ° to 40 ° 2® in 0.02 ° steps for 2 seconds at each step. For separation of the kaolinite/chlorite 7 ,& peak, an additional scan was performed in 0.005 ° steps for 2 seconds at each step between 28 ° and 30.5 ° 2 O in order to determine the 3.54 A peak of chlorite and the 3.58 A peak of kaolinite (Biscaye, 1965). Semiquantitative evaluations were based on peak areas of the four clay minerals smectite (~ 17 ]~), illite (10 A), kaolinite (7 and 3.57 A), and chlorite (7 and 3.54 A,) (Biscaye, 1965).

4. Results

Carbonate and organic carbon contents, hydrogen index values and temperatures of maximum pyrolysis yield (Tmax values) derived from Rock-Eval pyrolysis, organic carbon/ nitrogen (C/N) ratios, sand-silt-clay contents of carbonate-free samples, and the clay mineral composition determined on all surface sediment samples are summarized in Tables 1 and 2. Carbonate and organic carbon contents were determined on surface sediment samples taken by both multicorer and giant box corer.

4.1. Carbonate distribution

In general, the carbonate content of the surface sediments is relatively low; most values are less than 10% (Table 1; Figs. 3A and 4). Minimum values of less than 5% occur in the central

Amundsen and Nansen Basins as well as directly north of Svalbard. Carbonate contents of l0 to 20% are common on the Yermark Plateau, the Gakkel Ridge, and the eastern flank of the Lomonosov Ridge. Maximum carbonate contents are recorded on the Morris-Jesup Rise, reaching values of up to 30%. One single value of 38% was measured on a sample from the northwestern Svalbard continental margin. There is no correlation between carbonate content and water depth (Fig. 4).

4.2. Distribution and composition of organic carbon

Almost all of the surface sediment samples have relatively high total organic carbon (TOC) values ranging between about 0.5 and 2% (Table 1; Figs. 3C and 4). Maximum values of > 1% occur around northern Svalbard and in the central Nansen Basin, low values are typical for the Gakkel Ridge, the eastern flank of the Lomonosov Ridge, and the Morris-Jesup Rise. In general, TOC values are higher in the deep-sea basins than on the ridges. There is, however, no simple linear correlation between TOC content and water depth (Fig. 4).

To get informations about the composition of the organic matter, hydrogen index values and C/N ratios have been determined. In immature sediments, hydrogen indices of < 100 mgHC/gC are typical of terrigenous organic matter (kerogen type III), hydrogen indices of 300 to 800 mgHC/gC are typical of marine organic matter (kerogen types I and II) (e.g., Tissot and Welte, 1984). C/N ratios of marine organic matter are around 6 whereas terrigenous organic matter has C/N ratios of >15 (e.g., Bordowskiy, 1965; Hedges et al., 1986). For more precise determinations of the marine and terrigenous proportions of the organic carbon fraction, other methods such as kerogen/coal petrography and gaschromatography are required. These more time-consuming investigations are in progress on Arctic 91 material (Schubert and Stein, in prep.).

Based on low hydrogen index values of < 100, the organic carbon fraction of the central Arctic Ocean surface sediments is clearly dominated by terrigenous material (kerogen type III) (Table 1; Figs. 3C and 5). This is also corrobarated by


Table 1

Summary table of core number, longitude/latitude, water depth (m), carbonate and total organic carbon contents (%), C/N ratios, hydrogen index values (mgHC/gC), and Tm~x values (°C). For most of the ARK-VIII/3 samples (i.e., Cores 2157-2215) carbonate and organic carbon data have been determined on both giant box corer (GKG) and multicorer (MUC) surface sediment samples

Core Long. Lat. Depth CaCOs CaCO3 TOC TOC HI Tmax C/N (m) (GKG) (MUC) (GKG) (MUC)

2111 34.877 76.638 218 2.87 1.45 2113 34.898 76.003 260 2.98 1.40 2114 19.092 77.568 178 5.66 2.13 2115 18.328 77.200 101 5.03 1.75 2116 17.168 75.988 331 9.55 1.53 2117 5.994 79.008 202 12.05 1.02 2119 8.160 79.002 897 8.00 1.00 2120 8.592 79.027 175 14.00 1.41 2121 10.743 79.018 337 11.22 1.75 2122 7.543 80.390 702 4.20 1.17 2123 9.857 80.167 574 4.40 1.41 2124 11.202 79.970 172 5.00 0.17 2125 12.237 80.047 94 38.30 0.42 2127 18.457 81.020 195 5.50 0.35 2128 16.707 81.507 2528 9.00 0.81 2129 17.472 81.367 861 3.40 0.75 2130 18.623 81.290 550 8.00 1.57 2131 27.098 80.975 106 3.70 0.35 2132 31.488 81.443 236 7.70 0.63 2133 30.780 81.432 399 7.80 0.73 2134 29.803 81.680 2440 9.00 1.41 2136 30.550 81.525 1947 6.50 0.82 2137 30.777 81.578 1394 5.00 0.91 2138 30.593 81.535 862 6.30 1.08 2142 30.635 80.848 116 13.40 0.43 2143 30.120 80.812 197 4.80 0.89 2t44 29.473 80.747 505 5.70 1.36 2147 29.136 80.336 380 5.40 0.80 2148 29.603 80.013 339 5.60 1.30 2149 31.733 73.176 77 3.10 0.48 2150 32.134 78.666 283 4.40 1.26 2151 32.939 77.991 143 2.70 0.81 2153 34.810 76.608 187 4.70 1.42 2156 30.230 80.087 258 6.20 1.19 2157 29.915 81.755 2874 11.30 5.70 1.33 2158 29.925 82.776 3800 12.10 0.88 2159 30.370 83.960 4055 10.40 8.80 0.75 2160 37.951 84.881 4029 0.00 2161 44.422 85.450 4005 2.60 0.00 0.78 2162 50.827 85.795 3981 2.90 0.76 2163 59.215 86.242 3040 8.30 7.50 0.47 2164 59.176 86.338 2004 8.30 7.20 0.33 2165 59.960 86.447 2011 8.90 11.30 0.26 2166 59.699 86.860 3618 6.30 5.10 0.52 2167 59.015 86.945 4434 2.70 1.70 0.31 2168 55.934 87.510 3846 4.70 5.30 0.45 2170 60.766 87.590 4226 5.80 5.60 0.55 2171 68.977 87.586 4384 6.20 5.90 0.60 2172 68.377 87.257 4384 6.40 5.60 0.54 2174 90.500 87.495 4427 4.10 3.60 0.63

1.89

0.94 1.12 1.1

0.54 0.24 0.4 0.56 0.49 0.52 0.68 0.71 0.69 0.72

158 411 159 423 109 423 144 420 113 414 183 365 174 410 133 400 147 368 147 408

247 137 135 174 132 122 106 100 117 110 118 108 155 161 143 131 148 185 196 183 172 138 89 57 62

120 97

142 55 46 62 73

108 76 47 71 75 84

393 406 344 381 413 382 404 421 414 383 403 386 425 405 353 376 395 423 513 418 4OO 4OO 421 386 392 518 477 5O2 371 404 378 377 522 349 360 359 326 432

10

26 28 28

19 13 23 20 21 22 24 19 18 21

IL Stein et al./Marine Geology 119 (1994) 269-285 275

Table 1 (continued)

Core Long. Lat. Depth CaCO3 CaCO3 TOC TOC HI Tin. x C/N (m) (GKG) (MUC) (GKG) (MUC)

2175 103.566 87.568 4378 4.30 3.20 0.66 0.77 76 472 27 2176 108.750 87.765 4361 3.80 2.80 0.74 0.87 88 522 22 2177 134.926 88.036 1388 6.20 5.40 0.63 0.62 79 421 16 2178 159.168 88.005 4009 5.80 6.60 0.40 0.43 60 399 15 2179 138.029 87.746 1230 5.90 6.00 0.54 0.6 88 379 16 2180 156.676 87.626 4005 6.30 0.40 72 369 2181 153.059 87.596 3112 9.80 24.00 0.32 0.21 57 403 9 2182 151.120 87.572 2489 15.30 12.20 0.30 0.29 55 393 17 2183 148.830 87.602 2016 6.70 8.40 0.23 0.21 80 398 11 2184 148.140 87.611 1640 11.70 10.50 0.25 0.27 44 398 7 2185 144.166 87.529 1073 8.60 9.20 0.49 0.56 60 385 12 2186 139.907 88.512 1867 10.00 6.50 0.58 0.75 65 382 10 2187 126.913 88.735 3819 3.10 1.70 1.00 1.2 8l 390 10 2189 144.550 88.781 1001 10.70 11.60 0.37 0.41 129 450 13 2190 90.000 90.000 4240 3.30 1.80 0.91 1.12 75 479 11 2191 9.011 88.991 4346 8.10 0.73 57 348 20 2192 9.857 88.260 4375 10.00 8.50 0.56 0.68 52 346 19 2193 11.475 87.512 4399 6.40 5.10 0.67 0.73 64 427 19 2194 7.488 86.593 4326 11.80 0.52 57 353 2195 9.617 86.253 3793 7.80 0.61 63 360 2196 0.165 85.962 3958 8.00 6.50 0.64 0.57 49 391 6 2198 -9.057 85.565 3820 8.90 10.50 0.57 0.44 47 400 10 2199 - 11.913 85.435 1789 12.20 0.30 2200 - 14.022 85.328 1073 23.30 21.10 0.31 0.35 51 388 8 2202 - 14.369 85.109 1081 29.00 28.00 0.25 0.34 44 410 5 2204 - 13.035 85.058 3899 10.70 0.7 77 386 7 2205 -6.767 84.644 4283 6.90 6.90 0.40 0.47 74 526 7 2206 -2.505 84.278 2993 7.40 0.86 67 359 7 2208 4.603 83.640 3681 8.60 0.8 70 364 9 2209 8.573 83.225 4046 13.30 0.95 64 383 2210 10.125 83.045 3949 13.50 17.10 0.89 0.87 58 371 11 2212 15.672 82.024 2531 13.70 13.70 1.15 63 400 2213 8.205 80.473 897 3.40 2.40 1.16 1.42 147 483 10 2214 6.627 80.269 552 3.40 3.70 0.83 0.87 208 380 11 2215 5.341 79.695 2045 4.90 6.30 0.65 0.55 136 390 10

d o m i n a n t l y h igh C / N ra t ios ( T a b l e 1). S e d i m e n t s

f r o m the n o r t h e r n S v a l b a r d C o n t i n e n t a l M a r g i n

s h o w s o m e h i g h e r h y d r o g e n i ndex va lues o f 100

to 250 sugges t ing the p r e s e r v a t i o n o f s o m e h i g h e r

a m o u n t s o f m a r i n e o r g a n i c m a t e r i a l (F igs . 3C

a n d 5).

M o s t o f the o r g a n i c m a t t e r is i m m a t u r e as

i n d i c a t e d by l o w Tma~ va lues o f less t h a n 435°C (cf. Espi ta l i6 et al., 1977; T i s so t a n d Wel te , 1984).

In severa l samples , Tmax r e a c h va lues h i g h e r t h a n

450°C sugges t ing the p re sence o f m o r e m a t u r e

r e w o r k e d o r g a n i c m a t t e r ( T a b l e 1; Fig . 5). R o c k -

E v a l pyro lys i s p e r f o r m e d on single pebb le - s i zed

d a r k g ray s i l t s tones (i.e., I R D ) wi th T O C c o n t e n t s

o f a l m o s t 4% resu l ted in h y d r o g e n index va lues

< 20 a n d Tma x va lues a r o u n d 500°C, i nd i ca t i ng the

h i g h e r m a t u r i t y o f this ma te r i a l .

4.2. Grain-size distribution

Because the c a r b o n a t e c o n t e n t o f m o s t o f the sur face s amples is re la t ive ly l o w ( T a b l e 2; Fig . 3A) ,

the g ra in -s ize d i s t r i b u t i o n o f the c a r b o n a t e - f r e e

s e d i m e n t f r a c t i o n (F ig . 6) was used to c lass i fy the

cen t ra l A r c t i c su r face sed imen t s as m a i n l y si l ty

c lay o r c layey silt. Th i s is s imi la r to s ed imen t s in


,RE.~. , I

~ D E X ] ~)

2.E

5 -

5 -

O-

__ > 2

0."

3 -

5 -

> 1

!~00 ) - 150 I

150 J

Fig. 3. Distribution maps of carbonate (A), total organic carbon (B), and hydrogen indices (C). In the carbonate and organic carbon maps data from Bostr6m and Thiede (1984) and Pagels (1991) are included (open squares).

,-r I -

I - ,<

S U R F A C E S E D I M E N T S

0 = ~ • • 0 8 ° ° •

o ° e • • • -1000 • , -1000 , " •

,,-

L •= -2000 ~ ~ : -200G ~ - •

| • • •

-3000 - . - 3000 . =

• • ee= o ° w -4000, e , - 4000 •

% • • .b q , • • . - ' .

-5000 - 5000 0 1 0 2 0 3 0 0 1 2

C A R B O N A T E (%) T O T A L O R G A N I C C A R B O N (%)

Fig. 4. Variations of carbonate and total organic carbon contents vs. water depth of ARK-VIII/2 and ARK-VIII/3 (Arctic 91) surface sediments.

the western Arctic Ocean (Clark et al., 1980). Only a few samples from the continental margin as well as the Gakkel and Lomonosov Ridges have a higher sand content (sandy silt) (Fig. 6A). The highest sand content occurs in the samples from the Morris-Jesup Rise and on the continental margin north of Svalbard. In the deep-sea basins,

the sand content shows values below 10%. The silt fraction has lowest values north of Svalbard; maximum values occur on the Yermak Plateau, the Gakkel Ridge and the eastern flank of the Lomonosov Ridge (Fig. 6B). In general, the sediments have a distinctly higher clay content in the basins of the Arctic Ocean than on the ridges (Fig. 6C). This is particularly clear in the Amundsen Basin where the clay fraction shows values of more than 60% (with a maximum of up to 80%). The clay fraction is therefore a very important component of Arctic deep-sea sediments. The most drastic variations in the grain-size distribution exist on the Morris-Jesup- Rise and on the Svalbard Continental Margin (Table 2; Fig. 6).

4.3. Clay-mineral distribution

In all surface sediments illite is the dominant clay mineral with concentrations between 40 and 70% (Table 2; Fig. 7A). The highest illite contents occur north of Svalbard and on the Morris-Jesup-

R. Stein et al./Marine Geology 119 (1994) 269 285 2 7 7

500

O 400

b

E v 300 - X LU Q Z - - 200 - Z ILl

o rr 100- >. "t-

O

3 0 0

S U R F A C E S E D I M E N T S o A R K VIII /2 • A R K VIII /3

Jl o i j O

o 0 0 CI~ o o o-°~o ~ \ • o reworked?

0 o^ • ~ o ' • \ A

J

400 soo'k T m a x (oC) ~t~

Coal Fragments Dark Grey Silt/Claystones (Man Macera s: Vitrinite, Inertinite)

Fig. 5. Results of Rock-Eval pyrolysis of surface sediment samples of ARK-VIII/2 and ARK-VIII/3 Expeditions, presented in a hydrogen index vs. Tmax diagram (cf. Espitali6 et al., 1977; Tissot and Welte, 1984). Field I I I indicates terrigenous organic matter ("kerogen type III"), fields I and H indicate marine organic matter ("kerogen types I and II").

Rise. The lowest illite concentrations exist on the Barents Sea Shelf and in the central Nansen Basin north of Franz-Josef-Land. In all samples, the illite is very well crystallized, with a half-height width of about 0.3A°2®.

The average chlorite concentration in the surface sediments is about 22%; only a very few samples show values less than 20% or more than 25% (Table 2). The few sediments with chlorite concentrations of more than 25% are located on the Gakkel Ridge. No significant regional variations in chlorite content is apparent.

The kaolinite values vary between 10 and 40% (Table 2; Fig. 7B). Samples with more than 20% are located in the Nansen Basin northwest of Franz Josef Land and on the Barents Sea Continental Margin north of Svalbard. North of the Gakkel Ridge, kaolinite contents are less than 20%.

In comparison to the other clay minerals, smectite contents are low and vary between < 5% and

20% (Table2; Fig. 7C). Concentrations of less than 5% occur around Svalbard and on the Morris- Jesup-Rise. The highest smectite concentrations (up to a maximum of 20%) were determined on the Lomonosov Ridge.

5. Discussion

5.1. Carbonate content

In pelagic sediments, variations in biogenic carbonate content are mainly controlled by dissolution, dilution, and/or productivity changes. Based on coarse fraction data, the carbonate in the modern eastern central Arctic Ocean sediments (Fig. 3A) is mainly of biogenic origin; detrital carbonate is only of minor importance. Planktonic foraminifers are dominant throughout, whereas benthic foraminifers, bivalves, and ostracodes occur in minor amounts on the ridges and plateaus (F~tterer, 1992). Coccoliths are also present in significant amounts in the surface sediments (Gard, 1993). The occurrence of planktonic foraminifera and coccoliths suggests at least seasonal open-ice conditions.

The generally low content of detrital carbonate in the eastern central Arctic Ocean may indicate that the supply of IRD from the western Arctic is not of major importance today. Only in the Morris-Jesup Rise area, i.e., relatively close to the North Greenland continental margin, major proportions of detrital calcite and dolomite grains were recorded (Vogt and Stein, unpubl, data). This may support the transport of terrigenous (carbonate) sediments from northern Greenland onto the Morris-Jesup Rise, the source area of which are probably the Paleozoic carbonate rocks in North Greenland (Peel, 1982). This preliminary interpretation has to be proven, however, by a more quantitative coarse fraction analysis.

The good preservation of foraminifera tests in all surface sediment samples from about 200 to almost 4500 m water depth suggests that carbonate dissolution has not dominantly controlled the carbonate variations shown in Fig. 3A; instead, dilution by siliciclastics seems to be more important. This is in agreement with results of investigations

8 ~ eb

~

5 i

~

7~

o~

~J

c~


Table 2 (contmued)

Station no. Depth (m) Sand Silt Clay Smectite Illite Chlorite Kaolinite

2178-2 4009 7 48 46 6 59 24 10 2179-1 1230 3 43 55 8 51 26 15 2180-1 4005 8 47 45 8 59 22 12 2181-3 3112 15 55 30 8 59 22 12 2182-1 2489 30 47 24 8 54 25 13 2183-2 2016 38 41 20 8 53 23 16 2184-1 1640 24 51 25 9 55 23 13 2185-3 1073 9 43 48 16 51 22 11 2186-1 1867 8 61 30 10 52 24 14 2187-1 3819 0 38 61 8 50 26 16 2189-1 1001 34 47 19 11 49 24 16 2190-3 4240 1 33 67 14 49 23 14 2192-1 4375 1 29 70 5 63 22 10 2193-2 4399 2 73 25 2 60 22 15 2194-1 4326 1 54 45 1 63 24 13 2195-4 3793 3 38 59 11 54 22 13 2196-2 3958 2 36 62 9 55 23 13 2198-1 3820 13 37 50 6 61 22 12 2199-4 1789 96 3 1 7 57 24 12 2200-2 1073 35 38 27 1 67 21 10 2202-2 1081 46 32 22 3 64 21 12 2205-3 4283 0 39 61 7 53 22 18 2209-1 4046 1 44 55 8 56 20 16 2210-1 3949 3 52 45 9 53 21 16 2212-5 2531 3 83 14 1 60 23 17 2213-1 897 9 47 44 7 54 23 16 2214-1 552 29 54 18 7 56 21 16 2215-2 2045 65 24 11 8 57 17 17

of carbonate dissolut ion on p lank ton ic foramini-

fera tests f rom the eastern central Arctic Ocean (Pagels, 1991). Based on these results, the mode rn lysocline of this area is at abou t 4700 m water

depth. In the Yermak Pla teau area the high carbonate values may addi t ional ly reflect the influence of the warm Westspitsbergen Current , as already suggested by Pagels ( 1991 ).

5.2. Organic carbon record." Productivity indicator vs. terrigenous supply

Data on a m o u n t and composi t ion (i.e., mar ine vs. terrigenous) of the organic ca rbon fract ion in mar ine sediments can yield impor t an t in fo rmat ion abou t the deposi t ional env i ronment , oceanic circulation, and surface-water product ivi ty (e.g., Stein, 1991, and further references therein). In the central Arctic Ocean, this k ind of detailed data was no t

available unt i l now. Dis t r ibu t ion maps of total

organic carbon and carbonate in Arctic Ocean surface sediments nor th of Svalbard up to 86°N

has been produced by Pagels (1991) (based on his own data and data f rom Snare (1985) and Markussen (1986)). The results of Bost r6m and Thiede (1984) and Pagels (1991) agree well with our data and are included in the maps of Fig. 3A and B. Da ta on the quant i ty and qual i ty of the organic ca rbon fract ion (and clay minerals) are determined for the F r a m Strait area, i.e., for the

area directly south of our study area, and presented in d is t r ibut ion maps by Hebbe ln and Berner (1993). Both data sets fit together very well.

In general, the mode rn eastern Arctic Ocean is a low-product ivi ty env i ronment because of its sea- ice coverage (Subba Rao and Platt, 1984). This, together with the well-oxygenated deep-water sphere, results in the very low flux and preservat ion


5 5

1t 2 - 5 0

Fig. 6. Distribution maps of sand (A), silt (B), and clay (C) contents of the carbonate-free sediment fractions.

A ~ B I KAouNtT~ ~ I C I sMEeTITE ~1

15

Fig. 7. Clay mineral distribution maps of surface sediments. (A) Illite, (B) kaolinite, and (C) smectite.


of marine organic matter in the surface sediments. However, the occurrence of significant amount of biogenic carbonate (see above) as well as the occurrence of detectable amounts of unsaturated alkenones (Schubert and Stein, unpubl, data) which are biomarker produced by prymnesio- phytes (e.g., Marlowe et al., 1984), indicate at least seasonal open-ice or ice-free conditions and some bioproductivity.

The relatively high organic carbon contents, i.e., values which are distinctly higher than those recorded in modern normal open-marine environments, are certainly caused by the supply of terrigenous organic matter. This is clearly indicated by the low hydrogen index values (Figs. 3C and 4), generally high C/N ratios (Table 1 ) as well as first results of kerogen/coal microscopy work (Fig. 4). Part of the organic carbon measured in ground bulk sediments derives from black organic-carbon- rich silt stones (up to 4"/0 TOC) and coal fragments which were identified as IRD in the coarse fraction. These particles as well as the other terrigenous organic material were probably derived from the Siberian shelf areas and were transported by sea ice (via the Transpolar Drift) and/or currents (cf. Pfirman et al., 1989; Wollenburg, 1991; Bischof et al., 1992).

Increased organic carbon contents and increased hydrogen index values were recorded in the sediments around Northwest Svalbard (Fig. 3B and C), indicating increased preservation of marine organic matter in this area. These increased marine organic carbon values are probably caused by increased (ice-edge) surface-water productivity due to reduced sea-ice cover and increased nutrient supply, both triggered by the inflow of warm Atlantic Ocean water masses, i.e., the Westspitsbergen Current.

5.3. Clay minerals and grain size." Sources and transport mechanisms

Records on clay-mineral composition and grain- size distribution determined in marine sediment cores might give important information about different source areas and transport mechanisms of the terrigenous material as well as the climate of the source area and their changes through time,

as shown in numerous studies from different parts of the world ocean (e.g., Sarnthein et al., 1982; Naidu and Mowatt, 1983; Stein and Robert, 1985; Cremer et al., 1989; Chamley, 1989, and further references therein). In polar and subpolar regions where physical weathering processes dominate and chemical and diagenetic alterations are negligible, the clay mineral association in marine sediments can be a valuable indicator of sediment sources.

In general, the clay mineralogy of Arctic Ocean sediments reflects the source mineralogies of the landmasses and shelf areas surrounding the central Arctic Ocean basins (Darby et al., 1989 and further references therein): Illite is the dominant clay mineral (mostly > 50%), followed by chlorite and kaolinite (5 to 30%); smectites are variable, but of minor importance. This general picture is valid for the Amerasian Basin (e.g., Naidu et al., 1975; Clark et al., 1980; Dalrymple and Maass, 1987, Darby et al., 1989) as well as the Eurasian Basin (Table 2; Fig. 7; cf. Berner 1991). However when going into details, differences in clay mineral asso- ciations between different source areas are obvious and can be used as source rock indicators (Fig. 1). For example, potential source areas for kaolinite in Arctic Ocean sediments are Mesozoic and Cenozoic strata along the north coast of Alaska and Canada (Darby, 1975; Naidu and Mowatt, 1983; Dalrymple and Maass, 1987) and in the Barents Sea area (Birkenmajer, 1989; Elverhoi et al., 1989). A source for smectite is the Laptev Sea shelf area (Wollenburg, 1991; Ntirnberg et al., 1994-this volume). Locally smectite-rich Mesozoic strata are out-cropping on eastern Svalbard and in the Barents Sea (Elverhoi et al., 1989). The high smectite value of 20%° recorded at Barents Sea Core PS2113 (Table2) might be related to such a smectite-rich source.

The maximum illite concentration north of Svalbard and on the Morris-Jesup Rise (Fig. 7A) support the idea that illite is transported from northern Greenland and from Svalbard into the Arctic Ocean (Fig. 1). Transport of terrigenous sediments from northern Greenland onto the Morris-Jesup Rise is also suggested from the occurrence of sand-sized grains of detrital carbonate (see above).

Based on the distribution map of kaolinite,


probable source areas for kaolinite are the Barents Sea shelf area and Franz-Josef-Land (Figs. 1 and 7B; Berner, 1991). Cold, saline, dense water formed on the shelf, may sink over the continental margin into the Nansen Basin (Aagaard et al., 1985) and carry kaolinite-rich suspension down into the deep-sea environment. Important transport tracks for the suspension-rich water masses might be the major troughs northwest and north- east of Svalbard. Turbidity currents are another common transport mechanism of clay-rich suspen- sions from the Arctic shelves into the deep basins. This is supported by the occurrence of a large number of clayey-silty distal turbidites recorded in the Nansen and Amundsen Basins (Ftitterer, 1992).

Sediments from sea ice sampled at the same locations as surface sediment samples have high smectite contents of 15 to 60% similar to surface sediments from the Laptev Sea shelf which contain up to 45% smectite (Fig. 8; Wollenburg, 199; Niarnberg et al., 1994-this volume). This suggests that the Laptev Sea shelf is the potential source area of the siliciclastic material included in the sea

ice. The surface sediments of the Eurasian Basin, however, have only very low contents of smectite (Figs. 7C and 8; Berner 1991). This indicates that sea ice is not the dominant transport mechanism for clay-sized material in the Eurasian Basin, as proposed by Wollenburg (1991). Other transport mechanisms such as oceanic and turbidity currents are probably more important in controlling the sedimentation for most parts of our study area today. If terrigenous sediments are delivered pri- marily by sea ice, on the other hand, then only the coarser (silt- and sand-sized) material is accumu- lated inplace whereas the clay-sized material is transported/winnowed by oceanic currents. This could explain why the clay mineral signal does not reflect the IRD supply. The high content of terrigenous silt on the ridges supports this also. In the basins, on the other hand, the IRD signal is masked by fine-grained turbidites. A detailed heavy-mineral analysis of central Arctic Ocean sediments will probably yield more information about the importance of IRD input via the Transpolar Drift than a clay mineralogy study does, because very specific heavy minerals (e.g.,

Smectlte (%)

45

40

35

30

2s S

2O

15

10

6

o \ oo + ~ o

~ I ° A + l l o o o

o o o I I o eo + ~ l l ° °

! \ oo ° ° ° ° ° ° I \ ° ° o o

o A r c t i c see ice sediments

+ Leptev Sea surface sediments

Barents See surface •ediments

• Arctic surface sediments

÷/ \ o ° ° o

e . : •

\ • • / . \

o i . ' T : ' ~ t f 4 ~' i I 0 5 10 15 2 0 25 30 35 4 0 Kaolinite (%)

Fig. 8. Smectite versus kaolinite diagram. Four major fields of different smectite-kaolinite provinces have been distinguished. (A) Sea-ice sediments (data from Wollenburg, 1991; Niirnberg et al., 1994-this volume); (B) Laptev Sea surface sediments (data from Nfirnberg etal. , 1994-this volume); (C) Barents Sea surface sediments (data from Table 2); (D) Arctic Ocean surface sediments (data from Table 2).


epidote, pyroxene, etc.) characterize the source sediments in the Laptev Sea area (Korolev, pers. commun., 1993).

Alfred-Wegener-Institute for Polar and Marine Research.

6. Summary

Data on carbonate, organic carbon, grain size, and clay minerals of surface sediments give important information about the depositional environment, oceanic circulation patterns, and surface- water productivity in the modem eastern central Arctic Ocean and can be summarized as follows:

(1) Carbonate contents are generally less than 10%, with higher values typical for the ridges and lower values typical for the basins. The carbonate is mainly of biogenic origin; significant amounts of detrital carbonate were only recorded in the Morris-Jesup-Rise area.

(2) Organic carbon contents vary between 0.5 and 2% and are mainly of terrigenous origin. Higher amounts of marine organic matter are only preserved in the area north of Svalbard indicating at least occasionally open-ice or ice-free conditions and increased surface-water productivity due to the influence of the warm Westspitsbergen Current.

(3) Illite is mainly supplied from the northern Greenland and Svalbard areas. Kaolinite has its origin in the Barents Sea and Franz-Josef-Land areas. Smectite, a major clay mineral in sediments of the Laptev Sea shelf (the major source area of the IRD) as well as sea-ice samples, is of minor importance in the eastern central Arctic Ocean surface sediments.

Acknowledgments

For technical assistance and data discussion we thank R. Petscheck, H. R6ben, C. Schubert, M. Seebeck and R. Stax. The captain and the crew of the R.V. Polarstern are gratefully acknowledged for cooperation during the expedition ARK VIII/3. We also thank two anonymous reviewers for their constructive suggestions for the improvement of the manuscript. Financial support was provided by the Deutsche Forschungsgemeinschaft (grant no. STE 412/6). This is contribution No. 702 of the

References

Aagaard, K., Swift, J. and Carmack, K., 1985. Thermohaline circulation in the Arctic Mediterranean Seas. J. Geophys. Res., 90: 4833-4846.

Anderson, L.G. and Carlsson, M.L., 1991. Swedish Arctic Research Programm 1991, International Arctic Ocean Expedition 1991. Icebreaker Oden Cruise Rep., Swed. Pol. Res. Secret., Stockholm, 128 pp.

Anon, 1978. Polar Regions Atlas. Produced by the Foreign Assessment Center, Central Intelligence Agency.

Berner, H., 1991. Mechanismen der Sedimentbildung in der Framstrasse, im Arktischen Ozean und in der Norwegischen See. Ber. Fachbereich Geowiss. Univ. Bremen, 20, 167 pp.

Birkenmajer, H., 1989. The geology of Svalbard, the western part of the Barents Sea, and the continental margin of Scandinavia. In: A.E. Nairn et al. (Editors), The Ocean Basins and Margins. (The Arctic Ocean, 5.) Plenum, New York, pp. 265-329.

Biscaye, P.E., 1965. Mineralogy and sedimentation of recent deep-sea clays in the Atlantic Ocean and adjacent seas and oceans. Geol. Soc. Am. Bull., 76:803 832.

Bischof, J., Koch, J., Kubisch, M., Spielhagen, R.F. and Thiede, J., 1990. Nordic Seas surface ice drift reconstructions: evidence from ice rafted coal fragments during oxygen isotope stage 6. In: J.A. Dowdeswell and J.D. Scourse (Editors), Glacimarine Environments: Processes and Sediments. Geol. Soc. Spec. Publ., 53:235 251.

Bleil, U. and Thiede, J., 1990. Geological History of the Polar Oceans: Arctic versus Antarctic. (NATO ASI Ser. C.) Kluwer, Dordrecht, 308, 823 pp.

Bordowskiy, O.K., 1965, Sources of organic matter in marine basins. Mar. Geol., 3:5 31.

B6ggild, O.B., 1906. On the bottom deposits of the north polar seas: Scientific results of the Norwegian North Polar Expedition 1893-1896. 5, pp. 1 62.

Bostr6m, K. and Thiede, J., 1984. YMER-80. Swedish Arctic Expedition Cruise Report. Meddel. Stockholms Univ. Geol. Inst., 260, 123 pp.

Carmack, E., 1990. Large-Scale Physical Oceanography of Polar Oceans. In: W.O. Smith (Editor), Polar Oceanography, Part A, Physical Science. Academic Press, San Diego, pp. 171-222.

Chamley, H., 1989. Clay Sedimentology. Springer, Berlin, 623 pp.

Clark, D.L., Whitman, R.R., Morgan, K.A. and Mackay, S.D., 1980. Stratigraphy and glacio-marine sediments of the Amerasian Basin, central Arctic Ocean. Geol. Soc. Am. Spec. Pap., 181, 57 pp.

Cremer, M., Maillet, N. and Latouche, C., 1989. Analysis of sedimentary facies and clay mineralogy of the Neogene-


Quaternary sediments in ODP Site 646, Labrador Sea. Proc. ODP, 105, 1038 pp.

Dalrymple, R.W. and Maass, O.C., 1987. Clay mineralogy of late Cenozoic sediments in the CESAR cores, Alpha Ridge, central Arctic ocean. Can. J. Earth Sci., 24: 1562-1569.

Darby, D.A., 1975. Kaolinite and other clay minerals in Arctic Ocean sediments. J. Sediment. Petrol., 45: 272-279.

Darby, D.A. Naidu, A.S., Mowatt, T.C. and Jones, G., 1989. Sediment composition and sedimentary processes in the Arctic Ocean. In: Y. Herman (Editor), The Arctic Seas-- Climatology, Oceanography, Geology, and Biology. Van Nostrand Reinhold, New York, pp. 657-720.

Elverhoi, A., Pfirman, S.L., Solheim, A. and Larssen, B.B., 1989. Glaciomarine sedimentation in epicontinental seas exemplified by the northern Barents Sea. Mar. Geol., 85:225 250.

Espitali6, J., Laporte, J.L., Madec, M., Marquis, F., Leplat, P., Paulet, J. and Boutefeu, A., 1977. M6thode rapide de characterisation des roches-mere, de leur potential petrolier et de leur degre d'dvolution. Rev. Inst. Tranc. Petrol., 32:23 42.

Ftitterer, D.K., 1992. ARCTIC'91: The Expedition ARK- VIII/3 of RV "Polarstern" in 1991. Ber. Polarsternforsch., 107, 267 pp.

Gard, G., 1993. Late Quaternary coccoliths at the North Pole: Evidence of ice-free conditions and rapid sedimentation in the central Arctic Ocean. Geology, 21: 227-230.

Grantz, A., Johnson, L. and Sweeney, J.F., 1990. The Arctic Ocean Region. (Geology of North America, L.) Geol. Soc. Am., Boulder, CO, 644 pp.

Grobe, H., Mackensen, A., Hubberten, H., Spiess, V. and Ffitterer, D., 1990. Stable Isotope Record and Late Quaternary Sedimentation Rates at the Antarctic Continental Margin. In: U. Bleil and J. Thiede (Editors), Geological History of the Polar Oceans: Arctic versus Antarctic. (NATO ASI Ser. C.) Kluwer, Dordrecht, 308, pp. 539 576.

Hale, P.B., 1990. Offshore hard minerals. In: A. Grantz et al. (Editors) The Arctic Ocean Region. (Geology of North America, L.) Geol. Soc. Am., Boulder, CO, pp. 551 565.

Hebbeln, D. and Berner, H., 1993. Surface sediment distribution in the Fram Strait. Deep-Sea Res., in press.

Herman, Y., 1989 . The Arctic Seas--Climatology, Oceanography, Geology, and Biology. Van Nostrand Reinhold, New York, 888 pp.

Jackson, H.R., Mudie, P.J. and Blasco, S.M., 1985. Initial geological report on CESAR. The Canadian expedition to study the Alpha Ridge. Geol. Surv. Can. Pap., 84-22, 177 pp.

Lange, H., 1982. Distribution of chlorite and kaolinite in eastern Atlantic sediments off North Africa. Sedimentology, 29:427 432.

Markussen, B., 1986. Late Quaternary sedimentation and paleoceanography in the eastern Arctic ocean. Ph.D. Thesis, Oslo Univ., 175 pp.

Marlowe, I.T., Green, J.C., Neal, A.C., Brassell, S.C., Eglinton, G. and Course, P.A., 1984. Long chain alkenones in the Prymnesiophyceae. Distribution of alkenones and other

lipids and their taxonomic significance. Br. J. Phycol., 19: 203-216.

Mtiller, G., 1967. Methods in Sedimentary Petrology. In: W. von Engelhardt, H. Ft~chtbauer and G. MOller (Editors), Sedimentary Petrology, 1. Schweizerbart, Stuttgart, 283 pp.

Naidu, A.S. and Mowatt, T.C., 1983. Sources and dispersial patterns of clay minerals in surface sediments from the continental-shelf areas off Alaska. Geol. Soc. Am. Bull., 94:841 854.

Naidu, A.S., Mowatt, T.C., Hawkins, D.B. and Hood, D.W., 1975. Clay minerals and geochemistry of some Arctic Ocean sediments: Significance of paleoclimate interpretation. In: G. Weller and S.A. Bowling (Editors), Climate of the Arctic. Geophys. Inst., Univ. Alaska, Fairbanks, pp. 59 67.

Nansen, F., 1897. Farthest North. Archibald Constabel and Co., Whitehall Gardens, 510 pp.

Nt~rnberg, D., Wollenburg, I., Dethleff, D., Eicken, H., Kassens, H., Letzig, T., Reimnitz, E. and Thiede, J., 1994. Sediments in Arctic sea ice: Implications for entrainment, transport and release. In: J. Thiede, T.O. Vorren and R.F. Spielhagen (Editors), Arctic Ocean Marine Geology. Mar. Geol., 119: 000-000.

Pagels, U., 1991. Sedimentologische Untersuchungen und Bestimmungen der Karbonatl~sung in sp~itquart~iren Sedimenten des 6stlichen Arktischen Ozeans. Ph.D. Thesis, Kiel Univ., 106 pp.

Peel, J.S., 1982. The lower Paleozoic of Greenland. In: A.F. Embry and H.R. Balkwill (Editors), Arctic Geology and Geophysics. Can. Soc. Pet. Geol. Mem., 8:309 330.

Pfirman, S., Lange, M.A., Wollenburg, I. and Schlosser, P., 1989. Sea ice characteristics and the role of sediment inclusions in deep-sea deposition: Arcti~Antarctic comparison. In: U. Bleil and J. Thiede (Editors), Geological History of the Polar Oceans: Arctic versus Antarctic. (NATO ASI Ser. C.) Kluwer, Dordrecht, 308, pp. 187-211.

Rachor, E., 1992. Scientific Report of RV "Polarstern" Cruise ARK-VIII/2. Ber. Polarforsch., 115, 150 pp.

Sakshaug, E. and Skjoldal H.R., 1989. Life at the ice edge. Ambio, 18:60 67.

Sarnthein, M., Thiede, J., Pflaumann, U., Erlenkeuser, H., FtRterer, D., Koopmann, B., Lange, H. and Seibold, E., 1982. Atmospheric and oceanic circulation patterns off Northwest Africa during the past 25 millions years. In: U. von Rad et al. (Editors), Geology of the Northwest African Continental Margin. Springer, Berlin, pp. 545-604.

Scheffer, F. and Schachtschabel, P., 1984. Lehrbuch der Bodenkunde. Enke, Stuttgart, 442 pp.

Snare, T., 1985. Sedimentk~irnor (YMER-80) fran kontinental- sluttingen norr om Nordaustlandet-Svalbard. Cand. Sci. Thesis, Oslo Univ., 115 pp.

Stach, E. Mackowsky, M.T., Teichmt~ller, M., Taylor, G.H., Chandra, D. and Teichmaller, R., 1982. Stach's Textbook of Coal Petrology. Borntraeger, Berlin, 535 pp.

Stein, R., 1991. Accumulation of Organic Carbon in Marine Sediments. (Lecture Notes in Earth Sci., 34.) Springer, Heidelberg, 217 pp.

Stein, R. and Robert, C., 1985. Siliciclastic sediments at Sites


588, 590, and 591: Neogene and Paleogene evolution in the Southwest Pacific and Australian climate. Init. Rep. DSDP, 90:1437 1455.

Stein, R. and Stax, R., 1991. Late Quaternary organic carbon cycles and paleoproductivity in the Labrador Sea. Geo-Mar. Lett., 11:90 95.

Subba Rao, D.V. and Platt, T., 1984. Primary Production of Arctic Waters. Polar Biol., 3:191 201.

Sudgen, D., 1982. Arctic and Antarctic A Modern Geographical Synthesis. Blackwell, Oxford, 472 pp.

Thiede, J., 1988. Scientific Cruise Report of Arctic Expedition ARK-IV/3. Ber. Polarforsch., 43, 237 pp.

Tissot, B.P. and Welte, D.H., 1984. Petroleum Formation and Occurrence. Springer, Heidelberg, 699 pp.

Untersteiner, N. and Carmack, E., 1990. Arctic sea ice, freshwater, and global ocean climate: some possible connec- tions. Appendix. WMO Working Group on Sea Ice and Climate. Rep. 4th Session.

Wollenburg, I., 1991. Sedimenttransport durch das arktische Meereis Die rezente lithogene und biogene Materialfracht. Ph.D. Thesis, Kiel Univ., 189 pp.

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