Download Source and grain-size influences upon the clay mineral distribution

Clay Minerals (1998) 33, 3-13
Source and grain-size influences upon the
clay mineral distribution in the Skagerrak
and northern Kattegat
H. BENGTSSON
AND R. L. S T E V E N S
Department of Geology, Earth Sciences Centre, G6teborg University, Box 460, S-40530 G6teborg, Sweden
(Received 12 August 1996; revised 27 January 1997)
A B S T R A C T : Bottom sediments from 78 sites in the Skagerrak-Kattegat area have been used to
determine the semi-quantitative distribution of clay minerals, and to interpret sediment provenance
and the transport pathways. The sediment reflects incorporation of four sources, affected both by
earlier glacial processes and on-going marine mixing. The southern North Sea, characterized by
dioctaheadral illite, kaolinite and smectite, is the dominating source. The central North Sea provides
a limited, but significant, source for chlorite. The sediment from the Swedish west coast has an
unweathered character, containing trioctaheadral illite, vermiculite, illite-vermiculite mixed-layer
minerals and chlorite. The contribution from the southern Kattegat (southern Sweden and Denmark)
is dominated by kaolinite and smectite. Correlation between clay content and the contents of
smectite, kaolinite and chlorite in the Skagerrak indicate that the clay mineral distribution is
influenced by sorting. This grain-size dependency must be considered when interpreting sources.
The Skagerrak is an eastern extension of the North
Sea, and has a maximum depth of 700 m in the
central, Norwegian Trench (Fig. 1). The shallower
Kattegat (maximum depth of 100 m) lies south-east
of Skagerrak and is connected in the south to the
Baltic Sea. The Skagerrak provides a natural
sediment trap for the material transported from
the Baltic, the Scandinavian rivers and the
comparatively shallow North Sea. The dominant
sediment transport pathways from the North Sea are
well established in general (Svansson, 1975; Eisma
et al., 1979; Eisma & Kalf, 1987; van Weering,
1981, 1982; Kuijpers et al., 1993; Lepland &
Stevens, 1996). Drainage from the Baltic,
Scandinavian rivers from adjacent land, and seabottom erosion are also considered significant
sediment sources. Recent volumes of collected
papers dealing with the Skagerrak-Kattegat are
found in Liebezeit et al. (1993) and Rosenberg
(1996).
Several clay mineral investigations have been
published for parts of the Skagerrak and the
Kattegat, although usually as an extension of
samplings in the North Sea proper or limited to a
local region with particular interest (Ronningsland,
1976; Jorgensen et al., 1981; Pederstad, 1982;
Pederstad et al., 1993; Wirth & Wiesner, 1988;
Meyenburg & Liebezeit, 1993; Z611mer & Irion,
1993). Considering the importance of fine-grained
sedimentation, therefore, we have extended the
geographic coverage with the objective of interpreting transport pathways and sources. This
investigation also evaluates the association
between grain size and clay mineralogy, which
involves important modifications in some areas due
to sediment sorting processes.
SAMPLES
AND
METHODOLOGY
The samples consist of the upper 2 cm of the
sediment, subsampled from box cores and multicore tubes c o l l e c t e d d u r i n g three cruises
( 1 9 8 8 - 1 9 9 3 ) . Additional samples have been
collected in co-operation with the Geological
Survey of Sweden during marine geological
mapping along the Swedish west coast (Fig. 1).
9 1998 The Mineralogical Society
H. Bengtsson and R. L. Stevens
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FIG. 1. The Skagerrak and Kattegat area with crosses showing the positions of the sampled sites. The main
surface currents are indicated with thick arrows for the dominant currents and thin arrows for episodic currents
(after Svansson, 1975; Rodhe, 1987). The sites marked with a square and with circles are referred to in Fig. 3.
The samples were treated with hydrogen peroxide
to remove organic matter, and dispersed with
sodium diphosphate. Grain-size analyses combined
wet-sieving and pipette methodologies (Krumbein
& Pettijohn, 1938).
The mineralogical analyses were performed by
X-ray diffractometry (XRD) using a Siemens
D5000 diffractometer, Ni-filtered Cu-Kc~ radiation
(40 kV and 25 mA), and a scanning speed of 1~ 20
per minute. After removal of the organic material,
the clay fraction (<2 p.m) was separated from the
coarser sediment by repeated gravitational settling.
Oriented preparations of the clay were first
collected onto a 0.45 p.m membrane filter and
then transferred to a glass slide (Drever, 1973).
The clay samples were all routinely investigated
with two preparations: Mg-saturated and, separately, Mg-saturated with glycerol saturation. For
selected samples, additional pretreatments included
ethylene glycol saturation, K saturation followed by
heating to 350~ and, separately, to 550~
and
partial dissolution with 1 M hydrochloric acid for
6 h in an 80~ water bath. Non-oriented powder
samples were run to identify the predominance of
dioctahedral (060 = c. 1.50 A) or trioctahedral
(060 = c. 1.54 .~) clay mineral varieties. In
addition, the dioctahedral and trioctahedral characterization of illite could also be estimated using
the intensity ratio of the 001 and 002 peaks, where
001/002 <4 is consistent with a predominance of
dioctahedral illite. Criteria for clay mineral
identification were based upon information in
Brown (1961), Brown & Brindley (1980), and
Reynolds (1985). Illite has a strong 10 A peak with
MgC12 saturation. A comparison of XRD curves for
various pretreatments is given in Fig. 3. The
Grain-size influence on clay mineral distribution
5
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40
Clay content
I
/
I,
' II
>50%
--
40-50%
/
<40%
FIG. 2. The bottom-sediment clay content in the Skagerrak-Kattegat area (after van Weering, 1982; Pederstad et
al., 1993; Stevens et al., 1996). The increasing clay content corresponds closely to increasing depth. The
bathymetry is displayed with 100 m contour lines.
patterns from the MgC12 and glycerol saturated pretreatment were used for the semi-quantitative
calculations. The computer program DIFFRAC/AT
version 3.06 was used to measure the integrated
peak areas in a consistent manner. Clay mineral
percentages were obtained by resolving overlapping
peaks when necessary and multiplying the peak
areas with weighting factors to compensate for their
relative intensities (Table 1).
RESULTS
The grain-size character of the bottom sediments in
the Skagerrak and the Kattegat varies from sandy
deposits along the west coast of Denmark (Jutland),
with a few percent clay, to the clay-rich (>50%)
deposits of the Norwegian Trench (Fig. 2).
The clay fractions include the clay minerals illite,
kaolinite, smectite, chlorite, mixed-layer minerals
and vermiculite (Fig. 3A); amphiboles, quartz,
feldspars and calcite are also present. With the
exception of vermiculite, all clay minerals are
present at all sites, although the proportion of
each mineral species varies (Table 1).
The highest contents of chlorite are in western
Skagerrak (>15%, Fig. 4A). Low contents (<5%)
are only found in restricted areas west of the north
end of Denmark and at the border between the
6
H. Bengtsson and R. L. Stevens
(A)
Chlorite
Illite
(B)
to
20
~o
3o
to
20
Jo
;o
FIG. 3. Typical XRD patterns from the Skagerrak-Kattegat region, showing the different preparations (A) that
were selectively used for mineral identification (example from north of Jutland, Denmark, marked with a square
in Fig. 1). Mixed-layer minerals (I-S and I-V) and vermiculite are only present in very small amounts in this
example. The peak at 12 ~. in the air-dried treatment is not a mixed-layer mineral, as it disappears with MgCI2
saturation. Rather, this peak is a degraded illite presumably expanded by the laboratory dispersion treatment.
(B) X-ray diffraction patterns for samples after treatment with MgCI2 and glycerol saturation from regions of
different composition. The sites used as examples are marked with circles in Fig. 1. Cu-K~x radiation.
Skagerrak and Kattegat. Large amounts of kaolinite
are found north east and north west of Jutland,
Denmark (>20%, Fig. 4B). Smaller amounts are
found in western Skagerrak. The ratio between
kaolinite and chlorite is based on the 3.58 A peak
for kaolinite and the 3.54 A. peak for chlorite
(Biscaye, 1964). This ratio ranges from 0.8-1.9
(Table 1). It is at its greatest off the Jutland coast,
and smallest in western Skagerrak and near the
Swedish coast (Fig. 4C).
The lowest contents of illite are found in the
southern part of the Skagerrak (Fig. 4D), where the
illite is predominantly a dioctahedral mica. The
highest illite contents are near-shore to the
Grain-size influence on clay mineral distribution
TABLE 1. Clay mineral percentages calculated using the peak area of the glycerol-saturated sample, recalculated
to 100% intensity if necessary, and then normalized relative to the other minerals using an intensity factor, I.F.
(after Snail, 1973; Pederstad & J~rgensen, 1985; Reynolds, 1989).
Mineral
Chlorite
Kaolinite
Kaolinite/chlorite ratio
Illite
Mixed-layer minerals
Vermiculite
Smectite
Peak
4.74/k
7.18 A
3.58 ,~/3.54 ]~
10.0 A
12-13 ,~
14/k
17 ,~
I.F.
Calc. formulae
Statistical parameters (%)
Av. Min. Max.
S.D.
2
3
(4.74 ~ x 2.5)/2,
(7.18 A-(4.74 Ax2.5))/3
1
2
3
3
10.0 ~,/1
11-13 A/2
(14 ~ - ( 4 . 7 4 A x 1.5))/3
17 A/3
Scandinavian mainland, where the illite is of mainly
trioctahedral character. Although these regional
trends are seen in Fig. 3B (cf. 001/002 ratio of
illite), the separate distributions of dioctahedral and
trioctahedral mica are not presented because of the
difficulties in quantifying their proportions. The
mixed-layer minerals consist of illite-smeetite (I-S)
and illite-vermiculite (I-V) varieties. The I-S
composition predominates in all samples except
for a few sites near Sweden. The large variation of
mixed-layer minerals ( 1 - 2 4 % ) reflects the extremely high contents in a few samples near Swedish
river outlets (Fig. 4E). The individual distributions
of I-S and I-V are not presented because of their
low average percentage and irregular distribution.
Vermiculite is not present at all sites, and in many
cases only as a trace mineral (Fig. 4F). The largest
contents are near the Grta ~ilv River outlet on the
central coast of western Sweden (Fig. 1). The
greatest smectite contents are in the deepest part
of the Skagerrak (Fig. 4G), and the smallest are just
north of Denmark.
The mineralogical variation is sufficient to
distinguish different sub-areas by comparison of
the XRD patterns from key sites (Fig. 3B). The
average XRD pattem in the Kattegat is characterized by trioctahedral illite and chlorite. The
southern Skagerrak primarily contains dioctahedrat
illite, kaolinite and smectite. The mixed-layer
minerals in the southern Skagerrak are mainly l-S,
but I-V is also present. Eastern Skagerrak has a
composition intermediate between those found in
southern Skagerrak and the Kattegat, characterized
by dioctahedral illite, kaolinite, smectite, chlorite
and feldspars. In north western Skagerrak, dioctahe-
9
15
1.3
62
4
1
10
3
7
0.8
43
1
0
3
18
25
1.9
74
24
5
27
+_4
+5
+0.3
+7.5
_+4.5
_ 1
-+5
dral illite and chlorite predominate, while the
kaolinite, smectite and feldspar contents are
relatively low. In western Skagerrak, smectite and
chlorite increase, while kaolinite and illite decrease
compared to north western Skagerrak.
For the entire sample set, there are no significant
correlations between grain size and the individual
clay minerals. For samples w i t h i n western
Skagerrak, however, there is a weak, positive
correlation between the contents of clay (<2 gm)
and smectite (Fig. 5A). Also, mixed-layer minerals
in this area have a very weak, positive correlation
with clay content, whereas a weak, negative
relationship exists between clay and both kaolinite
and chlorite (not shown). Elsewhere, the only
correlation that was evident was the very weak,
negative relationship between smectite and clay
content in the Kattegat (Fig. 5B).
DISCUSSION
General mineralogy
The illite-rich clay composition of the Skagerrak
and Kattegat sediments (Table 1, Fig. 4D) is in
common with most marine deposits of the North
Atlantic and adjacent seas (cf. Griffin et al., 1968).
Illite, particularly the trioctahedral form, reflects the
limited weathering of micaceous source material
within a temperate, terrestrial climate, complemented in northern latitudes with the recent
reworking of widespread glacial deposits of
immature mineralogy. Although in lesser amounts,
the presence of chlorite in all samples also requires
a relatively unweathered source, as does the
H, Bengtsson and R. L. Stevens
(A)
(C)
Ratio
kaolinite/chlorite
(F)
(B)
Chlorite
(D)
Illite
Vermiculite
Kaolinite
(E)
(G)
Mixed-layer minerals
Smectite
05
FIG. 4, Distribution of clay minerals (%) in the Skagerrak-Kattegat area, based on semi-quantitative calculations
from the XRD patterns. The illite content (D) includes both dioctahedral and l~ioctahedral mineral varieties, and
the I-S and I-V mixed-layer minerals (E) are combined.
survival of a feldspar component in the clay
fraction of most samples.
At the same time, the smectite and kaolinite
contents suggest the incorporation of significant
materials produced by recent or ancient weathering
processes. For the Quaternary clays in southwestern Sweden, a similar reflection of dual
source character has been explained by the glacial
erosion of a terrain with areas of both pre-
weathered mantle and non-weathered sediments
and crystalline bedrock (Stevens et al., 1987).
However, in the Swedish deposits, the predominant
products of weathering are vermiculite and I-V
mixed-layer clay minerals, which are only poorly
represented in the Skagerrak-Kattegat sediments.
Therefore, kaolinite and smectite are probably
derived from areas where older deposits or
sedimentary bedrock occur, e.g. south of the
Grain-size influence on clay mineral distribution
(A)
~
9
(B)
R=0.43
15
9 :
"5
~1o
10
V
9 ""
E
oO
9"
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E
03 5
,"
5
V
G)
R=0.82
.
10
.
20
.
. 30
.
40.
50
60~176
Clay content
;o
~o
1o
d0
Clay content
F~G. 5. Bivariant plots for smecfite and clay contents in the Skagerrak along the Jutland Current (A), and the
Kattegat (B).
Tomqvist zone separating the crystalline bedrock of
the Fennoscandian segment from the younger
sedimentary formations in Denmark, southernmost
Sweden and most of the North Sea and westem
Europe. The non-glaciated areas to the south also
have greater preservation of older and, in places,
more extensive soil development.
The regional clay mineral variations are evaluated below in terms of possible sources. It is also
necessary to consider the grain-size dependency
that, although weak, may have influenced the
patterns of mineral concentration. Since the grain
size to mineral content relationships are weak and
only regionally defined, normalization of mineral
contents is not feasible. The weak correlations
themselves may suggest that the sediments in most
areas have been mixed from more than one source
and modified by transport and depositional
processes that were variable over time. Sediment
sorting may also have been limited by the
prevalence of clay particles within larger aggregates, although the timing of aggregate formation is
not clearly established (Eisma & Kalf, 1987;
Stevens et al., 1996). Therefore, the mineral
trends are apparently not controlled solely by
grain-size influences, and provenance interpretations based upon multiple sites are believed to be
generally reliable when due consideration is given
to the sedimentological conditions.
North Sea p r o v e n a n c e
Chlorite contents in the Skagerrak increase
westward along the deep Norwegian Trench (to
>15%), suggesting a North Sea origin. This
interpretation is strengthened by the weak, negative
correlation between chlorite and clay content which
would favour lower chlorite contents in the very
fine-grained trench sediments, where they are
highest, and therefore not a grain-size effect. The
most likely sources for chlorite are the exposed
Pleistocene deposits with immature mineralogy in
the central North Sea (Wirth & Weisner, 1988;
Zrllmer & Irion, 1993). Transport into the
Norwegian Trench, along which this chlorite trend
is aligned, is consistent with the inflow of the North
Atlantic Water Current from the west. Although
volumetrically the largest in the Skagerrak, this
deep water current has not previously been
attributed a major role in the sediment supply.
Variations of approximately 5% in the chlorite
content are, nevertheless, a reasonable effect of
diffuse (low concentration) transport of a relatively
chlorite-rich sediment in suspension.
The high content of kaolinite along the west
coast of Denmark and eastward to the Swedish
coast (Fig. 4B) is consistent with its transport from
the southern North Sea by the Jutland Current along
the Danish west coast, as has been suggested by
several authors (Wirth & Wiesner, 1988; Zrllmer &
[rion, 1993). The tendency for kaolinite particles to
be larger and more stable than other clay minerals
could help to concentrate kaolinite in the coarser,
near-shore sediments. However, this grain-size
relationship was very weak when tested, and the
southern source supply is interpreted to be primarily
responsible for the distribution pattern.
Since the western Skagerrak has well defined
distribution patterns and low grain-size dependency
for both chlorite and kaolinite, the mapped ratio of
these two minerals (Fig. 4C) represents the relative
contributions from two sources: a mineralogically
immature source in the central North Sea for
chlorite-rich sediment, and a more southern North
10
H. Bengtsson and R. L. Stevens
Sea source with kaolinite reflecting its history of
weathered alteration. The K/C ratio is lowest in the
Norwegian Trench, but increases eastward in both
deep and shallow portions of south-western
Skagerrak, indicating increasing sedimentation in
this direction from the coastal Jutland Current
relative to that of the North Atlantic Deep Water
Current. The trends documented here extend and add
detail to the same ratio mapped in the North Sea by
Wirth & Wiesner (1988). Further eastward, beyond a
north-south boundary that corresponds to the
relatively deep trough 'Djupa r'annan', the K/C
relationship decreases rapidly, indicating increasing
amounts of chlorite eroded from exposures of less
mature glacial deposits in the Kattegat and along the
Swedish west coast (see below). Furthermore, the
diminished importance of the Jutland Current in this
area of interaction with the northward surface
outflow of Baltic waters may selectively limit the
transport of relatively coarse kaolinite from the west.
The grain-size dependency associated with
smectite is presumably due to its smaller and less
stable particles, which would tend to be enriched
within the areas of very low turbulence, in
particular the Norwegian Trench (Fig. 4G).
Similar to kaolinite, smectite has been attributed
to southem North Sea sources (Wirth & Wiesner,
1988; Z611mer & Irion, 1993). We concur with this
interpretation, noting that the different distribution
patterns of kaolinite and smectite from the same
source can be explained by the selective transport
of fine-grained smectite offshore. The minor
amounts of mixed-layer minerals demonstrate a
distribution similar to smectite, likely due to a
southern North Sea supply that is modified by the
tendency for the fine-grained mixed-layer minerals
to also be transported offshore.
Other sources
There are two different sottrce types that are
combined in the Kattegat area. Together with
trioctahedral illite and chlorite, the widespread
occurrence of feldspars and amphibole in the clay
fraction indicates a relatively unweathered mineralogical source material (Fig. 3B, 4A, 4D).
Kaolinite and smectite reflect, on the other hand,
the concurrent erosion of weathered sources,
especially in the southern part of the Kattegat
(Fig. 3B, 4B, 4G).
The relatively low contents of chlorite near the
border between the Skagerrak and the Kattegat
(Fig. 4A) are partly influenced by the Jutland
Current, which transports chlorite-poor sediment
into the area, masking the local input. This effect is
not so evident for illite, as it predominates in the
sediment from the local sources as well as from the
Jutland Current. However, the illite from the North
Sea has a stronger dioctahedral character than do
the sites from western Sweden. High illite contents
of mainly trioctahedral character along the Swedish
west coast strongly suggest a local source,
presumably derived by terrigenous or near-shore
erosion (Fig. 4D). This is in agreement with the
composition of Pleistocene surface deposits in
south-western Sweden (Bengtsson, 1991; Lfing &
Stevens, 1996). The illite distribution agrees with
the results by Pederstad et al. (1993), documenting
an illite-rich sediment in the fjords of western
Sweden and southern Norway. They noted a
decrease in illite content towards the Skagerrak.
Large chlorite contents have also been recorded in
the Norwegian fjords (Ronningsland, 1976;
Pederstad, 1982; Pederstad et al., 1993), but a
significantly higher chlorite content was not
recorded at the few fjord sites in this study.
Vermiculite and I-V mixed-layer minerals are
interpreted to be principally supplied by the G6ta
~ilv River and other coastal sources in western
Sweden (Fig. 4E, 4F) where these minerals are the
principal products of moderate podzol weathering in
this area (Melkerud, 1984; Lhng & Stevens, 1996).
The smectite, kaolinite and mixed-layer minerals of
I-S composition in the Kattegat originate either
from the southern North Sea (via the Jutland
Current) or, more likely, from erosion of
Mesozoic and Tertiary sediments in Denmark and
southern Sweden (Bondam, 1967; Nielsen, 1974;
Pederstad et al., 1993).
CONCLUSIONS
The clay mineral composition in the SkagerrakKattegat area reflects the incorporation of four
regional sources (Fig. 6). A smectite and kaolinite
source in the southern North Sea and the
subsequent north-east transport of these minerals
along the Jutland Current is interpreted from the
distribution patterns, with consideration for the
mineral sorting effects related to grain size
(Fig. 4B, 4G). The distribution of chlorite in
western Skagerrak indicates an influx transported
by the North Atlantic Deep Water, although of
limited proportions. This component probably
Grain-size influence on clay mineral distribution
11
e'--Illite
Vermiculite
I-V
Chlorite
Chlorite
Smectite
Kaolinite
Vermiculite
I-S
FIG. 6. Interpreted clay-mineral contributions from the principal sources. Smectite, kaolinite and I-S mixed-layer
minerals are derived from the southern North Sea. The central North Sea source is characterized by a chlorite
component. Illite, vermiculite, I-V mixed-layer minerals, and chlorite are supplied from the Swedish west coast.
Southern Sweden and Denmark are sources for smectite, kaolinite, vermiculite and I-S mixed-layer minerals.
originates from sea-floor erosion of chlorite-rich
Pleistocene deposits of immature (unweathered)
mineralogy. In the Kattegat and along the
Swedish west coast in the Skagerrak, the relatively
large amounts of trioctahedral illite, chlorite,
amphiboles and feldspar minerals originate from
unweathered, local sources. The relatively large
amounts of vermiculite and mixed-layer minerals of
I-V composition in the Kattegat, especially near the
G6ta ~ilv River mouth, indicate input from
terrigenous sources. The presence of smectite,
kaolinite and mixed-layer minerals of I-S composition in the Kattegat indicate the erosion of a
weathered source within the area or transport by
bottom currents from the Skagerrak.
The suspension deposition within marine environments is not conducive to simple correlations
between fine-grained deposits and their sources.
The complex source character, related to hinterland
weathering and erosion variability, as well as the
mixing involved during transport and sedimenta-
tion, will result in a mineralogical continuum most
appropriate for relative interpretations. On the other
hand, fine-grained samples provide a time-integrated record that is representative for the combined
processes within an environment, which may be
hard to approximate when sampling coarser
deposits. Also, clay mineralogy allows identification of rather subtle changes in the components that
are most sensitive to provenance differences in
weathering history, in this case, the areas with
immature glacial deposits compared with southern,
less glacially influenced provenances with greater
amounts of weathering products.
ACKNOWLEDGMENTS
This work is part of the Swedish West Coast Project,
organized by a Swedish interdisciplinary project group
and financed by the Swedish Environmental Protection
Agency. Hierta-Retzeius foundation and Wilhelm and
Martina Lundgrens foundation provided financial
1t. Bengtsson and R. L. Stevens
12
support for analyses. We also thank the marine
geological division at the Swedish Geological Survey
for samples complementing our basin coverage.
REFERENCES
Bengtsson H. (1991) Mineralogiska unders6kningar av
jordm~nsprover fr~n Vgstergrtland. GU/CTH publikationsserie, B 362, 1-42.
Biscaye P.E. (1964) Distinction between kaolinite and
chlorite in recent sediments by X-ray diffraction.
Am. Miner. 46, 1281-1289.
Bondam J. (1967) Undersogekser vedr~rende de geokemiske forhold i kaolinforekomsten ved Ranne ph
Bomholm. Dan. Geol. Foren. Medd. 17, 297-365.
Brown G., editor (1961) X-ray Identification and Crystal
Structures of Clay Minerals. Second edition.
Mineralogical Society, London.
Brown G. & Brindley G.W. (1980) X-ray diffraction
procedures for clay mineral identification. Pp.
305-359 in: Crystal Structures of Clay Minerals
and their X-ray Identification. (G.W. Brindley & G.
Brown, editors). Mineralogical Society, Monograph
5, London.
Drever J.I. (1973) The preparation of oriented clay
mineral specimens for X-ray diffraction analysis by a
filter-membrane peel technique. Am. Miner. 58,
553-554.
Eisma D. & Kalf J. (1987) Dispersal, concentration and
deposition of suspended matter in the North Sea. J.
Geol. Soc. London, 144, 161- 178.
Eisma D., Jansen J.H.F. & van Weering T.C.E. (1979)
Sea floor morphology and recent sediment movement in the North Sea. Pp. 217-231 in: The
Quaternary of the North Sea. (E. Oele, R.T.E.
Schtittenhelm & A.J. Wiggers, editors). Acta Univ.
Ups. Syrup. Univ. Ups. Annum Quintegentesimum
Celebrantis, Uppsala.
Griffin J.J., Windom H. & Goldberg E.D. (1968) The
distribution of clay minerals in the world ocean.
Deep-sea Res. 15, 433-459.
Jorgensen P., Erlenkeuser H., Lange H., Nagy J.,
Rumohr J. & Werner F. (1981) Sedimentological
and stratigraphical studies of two cores in the
Skagerrak. Pp. 397-414 in: Holocene Marine
Sedimentation in the North Sea Basin. (S.-D. Nio,
R.T.E. Schiittenhelm & T.C.E. van Weering, editors). Spec. Publ. Int. Assoc. Sedimentol. 5.
Krumbein W.C. & Pettijohn F.C. (1938) Manual of
Sedimentary Petrography. Appleton-Century-Crotts
Inc., New York.
Kuijpers A., Detmeg~.rd B., Albinsson Y. & Jensen A.
(1993) Sediment transport pathways in the Skagerrak
and Kattegat as indicated by sediment Chernobyl
radioactivity and heavy metal concentrations. Pp.
2 3 1 - 2 4 4 in: Holocene Sedimentation in the
Skagerrak. (G. Liebezeit, T.C.E. van Weering & J.
Rumohr, editors). Mar. Geol. 111.
Lepland A. & Stevens R.L. (1996) Mineral magnetic
and textural interpretations of sedimentation in the
Skagerrak, eastern North Sea. Mar. Geol. 135,
51-64.
Liebezeit G., van Weering T.C.E. & Rumohr J., editors
(1993) Holocene sedimentation in the Skagerrak.
Mar. Geol. 111.
Lhng L.-O. & Stevens R.L. (1996) Weathering variability and aluminium interlayering: clay mineralogy
of podzol profiles in till and glaciofluvial deposits,
SW Sweden. AppL Geochem. 11, 87-92.
Melkerud P.-A. (1984) Distribution of clay minerals in
soil profiles - - a tool in chronostratigraphical and
lithostratigraphical investigations of till. Striae 20,
31-37.
Meyenburg G. & Liebezeit G. (1993) Mineralogy and
geochemistry of a core from the Skagerrak/Kattegat
boundary. Pp. 337-344 in: Holocene Sedimentation
in the Skagerrak. (G. Liebezeit, T.C.E. van Weering
& ]. Rumohr, editors). Mar. Geol. 111.
Nielsen O.B. (1974) Sedimentation and diagenesis of
Lower Eocene sediments at Olst, Denmark.
Sediment. Geol. 12, 25-44.
Pederstad K. (1982) Sedimentologiske, mineralogiske og
geokjemiske undersokelser av sedimenter fra
OsloJ~orden og Skagerrak. PhD thesis, Univ. Oslo,
Norway.
Pederstad K. & Jorgensen P. (1985) Weathering in a
marine clay during postglacial time. Clay Miner. 20,
477-491.
Pederstad K., Roaldset E. & R~nningsland T.M. (1993)
Sedimentation and environmental conditions in the
inner Skagerrak- outer Oslofjord. Pp. 245-264 in:
Holocene Sedimentation in the Skagerrak. (G.
Liebezeit, T.C.E. van Weering & J. Rumohr,
editors). Mar. Geol. 111.
Reynolds R.C., Jr. (1985) NEWMOD 9 a Computer
Program for the Calculation of One-dimensional
Diffraction Patterns of Mixed-layer Clays. R.C.
Reynolds, 8 Brook Rd., Hanover, N.H.
Reynolds R.C., Jr. (1989) Principles and techniques of
quantitative analysis of clay minerals by X-ray
powder diffraction. Pp. 4 - 3 6 in: Quantitative
Mineral Analysis of Clays. (D.R. Pevear & F.A.
Mumpton, editors). The Clay Mineral Society, CMS
Workshop Lectures, vol. 1, Evergreen, Colorado.
Rodhe J. (1987) The large scale circulation in the
Skagerrak: interpretations of some observations.
Tellus, 39A, 245- 253.
Rosenberg R., editor (1996) Swedish West Coast
Project. J. Sea. Res. 35, 1-234.
Ronningsland T.M. (1976) Mineralogi og geokjemi av
resente leirsedimenter i Skagerrak, Kattegat og
tilgrensende J~ordomrgtder. Can& Real. thesis,
Univ. Oslo, Norway.
Grain-size influence on clay mineral distribution
Sn~ill S., Persson Ch. & Wikstr6m A. (1973)
Mineralogisk unders6kning av morfin fr~n ett omr~tde
vaster om Katrineholm. SGU. Ser. C, 761, 1-32.
Stevens R.L. April R. & Wedel P. (1987) Sediment color
and weathered preglacial sources of Quaternary
clays in southwestern Sweden. Geol. F6ren.
Stockh. F6rh. 109, 241-253.
Stevens R.L., Be ngtsson H. & Lepland A. (1996)
Textural provinces and transport interpretations with
fine-grained sediments in the Skagerrak. J. Sea Res.
35, 99-110.
Svansson A. (1975) Physical and chemical oceanography of the Skagerrak and Kattegat. 1. Open sea
conditions. Fish. Board, Swed. Inst. Mar. Res. Rep.
1, 1-88.
van Weering T.C.E. (1981) Recent sediments and
sediment transport in the northern North Sea; surface
sediments of the Skagerrak. Pp. 335-359 in:
13
Holocene Marine Sedimentation in the North Sea
Basin. (S.-D. Nio, R.T.E. Schiittenhelm & T.C.E.
van Weering, editors). Spec. Publ. Int. Assoc.
Sedimentol. 5.
van Weering T.C.E. (1982) Recent sediments and
sediment transport in the northern North Sea;
pistoncores from the Skagerrak. Proc. Koninklyke
Akademie van Wetenschappen Series. B85,
155-201.
Wirth H. & Weisner M.G. (1988) Sedimentary facies in
the North sea. Mitt. Geol.-Paliiontol. Inst. Univ.
Hamburg, 65, 269-287.
Z611mer V. & Irion G. (1993) Clay mineral and heavy
metal distributions in the north-eastern North Sea.
Pp. 223- 230 in: Holocene Sedimentation in the
Skagerrak. (G. Liebezeit, T.C.E. van Weering & J.
Rumohr, editors). Mar. Geol. 111.