The Late Weichselian-Holocene transition in the 
Barents Sea: sedimentological and early diagenetic 
studies 

CARL FREDRIK FORSBERG 

Forsberg. C. F. 1987: The Late Weichselian-Holocene transition in the Barents Sea: sedimentological and 
early diagenetic studies. Polar Research 5 n . s . ,  289-290. 

Carl Fredrik Forsberg, Norwegian Geotechnical Institute, P . O .  Box 40 T h e n ,  0801 Oslo 8, Norway. 

Gravity cores and grab samples from the Barents Sea (Fig. 1) 
were studied with respect to mineralogy, grain size distribution. 
total carbon content and ‘Rock Eval’ pyrolysis. The samples 
were classified as either Late Weichselian or Holocene accord- 
ing to Bjarlykke et al. (1978) and Elverhoi & Solheim (1983). 

The grain size distributions show as expected that the Late 
Weichselian sediments are coarser than those from the 
Holocene. The ‘Rock Eval’ results show that while the carbon 
in the Late Weichselian sediments is almost exclusively re- 
worked with the greatest concentration in the 2-6 ym fraction, 
the carbon in the Holocene sediments contains increasingly 

... 

LOCATION PAP 

Fig. 1. The sample locations studied and the approximate posi- 
tion of the oceanic polar front. Subscript ‘g’ indicates grab 
samples. 

greater amounts of primary carbon up towards the sea bed with 
the highest content in the < 2 y m  fraction. There is a close 
connection between the period of annual ice cover and the 
carbon content in the Holocene sediments (Fig. 2). 

The Holocene sediments contain significant amounts of smec- 
tite and mixed layered minerals. whereas the Late Weichselian 
sediments d o  not. These minerals are indications of the Holo- 
cene deposits having, at least partially, a source outside the 
Barents Sea. Unlike the primary carbon the mineralogical distri- 
bution in the Holocene sediments is not much affected by the 
present hydrological regimes. 

The Late Weichselian glacial and climatic conditions were too 
severe to support primary production of carbon, and sediments 
from this period contain only carbon reworked from local sedi- 
mentary rocks. With the onset of the Holocene and the 
accompanying climatic amelioration primary production 
increased, allowing sedimentation of first cycle algal debris. A 
combination of deglaciation and the accompanying eustatic rise 
in sea level freed a potential sediment transportation path from 
the Arctic Ocean. The shelf and land masses surrounding the 
Arctic Ocean thus became potential sediment source areas for 
the Barents Sea. 

In the absence of any large rivers running into the Barents 
Sea one of the main agents of Holocene sediment supply is 
deemed to be dirty sea ice which may originate on the Siberian 
shelf. Published grainsize distributions of sediments from sea 
ice (Sharma 1979) compare very well with the silt and clay sized 
sub-populations from the sediments in the Barents Sea. 

Thus. the Late Weichselian to Holocene transition in the 
Barents Sea seems to have been accompanied by the onset of 
primary production in the water masses and a change from 
sedimentation of locally derived material by glacial processes 
to intrabasinal reworking by marine processes and the supply 
of extrabasinal inorganic material by sea ice rafting. 

References 
Bjerlykke, K . .  Bue, B. & Elverhei, A. 1978: Quaternary sedi- 

ments in the northwestern part of the Barents Sea and their 
relation to the underlying Mesozoic bedrock. Sedimentology 
25, 227-413. 

Elverhbi, A .  & Solheim, A. 1983: The Barents Sea ice sheet - 
a sedimentological discussion. Polar Research 1 n.s., 23-42. 



290 Carl Fredrik Forsberg 

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0.3. 
0 . 2 -  

SOUTB NORTH 

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Annual ice cover 10 
. 

8 .  
6 .  (months t 

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20 
10 

. 
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4 . 0  

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nineralog). 
I 

Total c a r b o n  content 
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- 

> 63 

illite/smectite 

chlorite/kaolinio 

5 3 / 5 2  

sr/s2 

, ,  

1 10 1 4  16 19 29 5 0  

C o r e  numbers 

Fig. 2 Summary of the main results for the surface core samples. The period of ice coverage is from Vinle (1977) 

Sharma. G .  D. 1979: The Alaskan sher. hydrographic, sedi- Vinje. T. 1977: Frequency distribution of sea ice in the 
mentary and geochemical environments. Springer. N.Y. 488 Greenland and Barents Seas, 1971-1980. U . S .  d e p .  
PP commerce. net. technical information.