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Review of Palaeobotany and Palynology 124 (2003) 113^129
www.elsevier.com/locate/revpalbo
Pollen distribution in marine surface sediments o¡shore
Western Australia
Sander van der Kaars a; , Patrick De Deckker b
a
Centre for Palynology and Palaeoecology, School of Geography and Environmental Science, Monash University, Clayton,
VIC 3800, Australia
b
Department of Geology, The Australian National University, Canberra, ACT 0200, Australia
Received 1 June 2001; accepted 25 November 2002
Abstract
We have examined the pollen content in sediments from the top of 38 cores taken offshore Western Australia
(WA). Water depth for these cores ranges between 81 and 4090 m. All samples are used to plot maps of total pollen
and total Pteridophyta spore concentration. Only the 26 core tops that yielded sufficient pollen grains ( s 35) are used
in the present study to plot percentage maps for individual pollen taxa, including that of the genus Pinus (recently
introduced to Australia). Five major bioclimatic zones are recognised by the distribution of pollen assemblages
offshore WA. These are related to the amount and seasonality of rainfall and vegetation distribution on land. They
reflect: (1) the open Eucalyptus forests and woodlands of northern WA with high and summer rainfall; (2) the open
Eucalyptus woodlands with Acacia and grasslands of northwestern WA with lower (400^600 mm) and summer
rainfall; (3) the open Acacia shrublands with grasses and grasslands of northwestern WA with low (300^400 mm) and
summer rainfall; (4) the open Acacia shrublands of central WA with low ( 6 300 mm) and summer as well as winter
rainfall; and (5) the open Eucalyptus forests and mixed shrublands of southwestern WA with lower (300^600 mm) and
winter rainfall. The influence of Indonesian-derived waters via surficial currents such as the Leeuwin Current is
recognised by the presence of Pteridophyta spores in the sediments at northern sites.
; 2003 Elsevier Science B.V. All rights reserved.
Keywords: pollen; marine palynology; Pteridophyta spores; Western Australia; core tops
1. Introduction
Palynological records from relatively dry areas
are di⁄cult to obtain by traditional terrestrial
studies due to the paucity of lakes and/or bogs
in these areas. However, marine palynological re-
* Corresponding author.
E-mail address: [email protected]
(S. van der Kaars).
search can provide important information on continental vegetation and climatic developments, as
well as the direction of predominant wind and
ocean currents and represent an alternative source
of palaeoecological information for some of these
relatively dry areas (for instance, West Africa,
northwestern Australia and the Arabian Sea
area). It has been shown that detailed palaeoecological interpretations are possible for these regions by comparison of core top samples and
marine core spectra (see Hooghiemstra, 1988;
0034-6667 / 03 / $ ^ see front matter ; 2003 Elsevier Science B.V. All rights reserved.
doi:10.1016/S0034-6667(02)00250-6
PALBO 2515 17-3-03
114
S. van der Kaars, P. De Deckker / Review of Palaeobotany and Palynology 124 (2003) 113^129
Hooghiemstra and Agwu (1988)). This approach
is particularly appropriate for o¡shore Western
Australia (WA) as there are very few records on
land (see Wallis, 2001 and references therein), especially in the northern regions of this very large
arid Australian state. Despite the importance of
marine palynological records in the palaeoecological study of WA (van der Kaars, 1991; Wang et
al., 1999; van der Kaars and De Deckker, 2002),
very little is known about the recent pollen distribution patterns in marine sediments from the
waters of WA. This study aims to provide a basis
for re¢ned interpretation of the marine palynological records of WA through analysis of pollen assemblages from marine core top samples along its
coast. The pollen distribution in marine surface
sediments from the waters of WA is analysed in
relation to the onshore vegetation distribution,
climate and pollen transport by water and/or
wind. The results will be of use for the bioclimatic
interpretation of palynological records and as a
guide in the selection of cores and future coring
sites for marine palynological research in the region.
Marine palynological studies are proving very
important nowadays when attempting to reconstruct palaeoclimates, and even more so when
aiming at identifying links between signals at sea
and on land. Such studies can only be achieved
through better knowledge of the distribution of
pollen at sea before interpreting the fossil record.
This is exactly what our present work aims at:
providing a sound base for palaeoecological studies of an arid region such as a large part of WA.
2. Environmental setting
WA encompasses approximately 20 degrees of
latitude and therefore covers a wide variety of
climatic conditions. The northern part of WA
comprises the humido^arid tropical summer rain
region, the centre the subtropical arid region and
the southern part the arido^humid winter rain
region (Sturman and Tapper, 1996). Annual precipitation along the transect varies from between
400 and 1600 mm in the north and south to less
than 300 mm in the centre (see Fig. 1). In the
north, rainfall is predominantly produced in
summer and in the south rainfall is predominantly
a winter feature, while the area in between receives both summer and winter rain (see Fig. 1).
The vegetation along a north^south transect
varies from open Eucalyptus forests with a grassy
understorey and grass-rich open Eucalyptus
woodlands in the north, to grass-rich open Acacia
shrublands and (coastal) grasslands, grading to
open Acacia shrublands in the centre and to
mixed shrublands, grading to open Eucalyptus
woodlands and Eucalyptus forests in the south
(see Fig. 2). In general, the vegetation north of
latitude 23‡S is much richer in grasses than the
area to the south.
The area of interest here, i.e. the eastern Indian
Ocean and WA, is characterised by contrasting
seasons that are re£ected by changes in ocean surface current directions. The strengths and directions of these surface currents are strongly controlled by winds. The generalised surface
circulation in summer is characterised by predominantly northwesterly winds in northern Australia
that are accompanied by much rainfall, as part of
cyclonic depressions. The region registers a complete change of wind direction to southeasterly
during the austral winter. At that time, the northern part of WA is dry and the southern portion of
the state is wet. Up to 50% of the rainfall in
northern WA can be delivered by cyclones in
summer (Wyrwoll, 1993). These cyclonic depressions cause strong river discharge, and it is likely
that much pollen is transported o¡shore during
that time. Ocean currents are also likely to in£uence the distribution of pollen. The major current
that follows the periphery of WA is the Leeuwin
Current (LC), which is an o¡shoot of the Indonesian Through£ow (Cresswell, 1991; Wij¡els et
al., 1996). The LC is characteristically a low salinity, warm water current that £ows poleward as
far as Cape Leeuwin; it eventually engenders
large eddies of low density water at higher latitudes in the vicinity of Geraldton down to Cape
Leeuwin (see Cresswell, 1991 for more details).
The strength of the LC is strongest during the
winter season. The cold, equatorward-£owing
West Australian Current travels below the LC.
It is found along the west coast of WA north-
PALBO 2515 17-3-03
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115
Fig. 1. Map showing the core top locations, topographic names mentioned in the text and rainfall data (source: Commonwealth
of Australia, Bureau of Meteorology, 2000, http://www.bom.gov.au).
wards to North West Cape from where it migrates
west to form part of the South Equatorial Current. This current has the potential to transport
pollen from the southern portion of WA northward.
3. Materials and methods
Selected core tops obtained during two RV
Franklin cruises, Fr10/95 (December 1995) and
Fr2/96 (February^March 1996), in the waters of
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Fig. 2. Map showing core top location and relevant vegetation of WA (simpli¢ed after AUSLIG, 1990). Heavy solid line indicates extent of sand dune country.
WA were sampled for this study. The two cruises
aimed at gathering oceanographic as well as palaeoceanographic data, which included the collection of some 52 deep-sea sediment cores along a
depth transect from 81 to 4090 m. The same core
tops have been used to study the distribution of
planktonic foraminifera (Mart|¤nez et al., 1998),
terrigenous clays (Gingele et al., 2001) and
benthic foraminifera (Murgese, submitted).
Samples for pollen analysis were prepared using
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the following method. The sediment was suspended in about 40 ml of tetra^sodium^pyrophosphate ( P 10%), sieved over 210- and 7-Wm meshes,
followed by hydrochloric acid (10%) treatment
and heavy liquid separation (sodium^polytungstate, SG 2.0, 20 min at 2000 rpm, twice) and
hydro£uoric acid (50%) treatment. The organic
residue was stained with safranin. Slides were
mounted in glycerol and sealed with para⁄n
117
wax. A known amount of Lycopodium marker
spores was added to each sample prior to chemical treatment in order to establish palynomorph
concentrations. All slides were counted along
evenly spaced transects using a Zeiss Axioskop
microscope at U630 magni¢cation. All percentage
values were calculated on the total pollen sum (all
pollen counted, excluding unknown pollen grains
and Pteridophyta spores).
Table 1
Core top samples Fr10/95 and Fr2/96 cruises
Core
Location
Fr95-2
Fr95-3
Fr95-4
Fr95-5
Fr95-6
Fr95-7
Fr95-8
Fr95-9
Fr95-10
Fr95-11
Fr95-12
Fr95-13
Fr95-14
Fr95-15
Fr95-16
Fr95-17
Fr95-18
Fr95-19
Fr95-20
Fr95-25
Fr95-26
Fr95-27
Fr96-4
Fr96-6
Fr96-7
Fr96-11
Fr96-12
Fr96-14
Fr96-17
Fr96-19
Fr96-21
Fr96-22
Fr96-23
Fr96-24
Fr96-25
Fr96-26
Fr96-28
Fr96-29
12‡32.86PS, 126‡14.84PE
13‡14.53PS, 124‡00.2PE
13‡55.18PS, 122‡01.51PE
14‡00.55PS, 121‡01.58PE
14‡19.67PS, 121‡09.81PE
14‡42.58PS, 120‡32.74PE
14‡54.97PS, 120‡57.49PE
18‡07.63PS, 118‡00.92PE
18‡08.93PS, 116‡01.29PE
17‡38.57PS, 114‡59.93PE
18‡14.7PS, 114‡59.63PE
18‡49.26PS, 113‡58.26PE
20‡02.71PS, 112‡39.73PE
19‡53.75PS, 112‡13.37PE
20‡59.83PS, 112‡59.35PE
22‡07.74PS, 113‡30.11PE
22‡59.64PS, 112‡49.86PE
24‡14.11PS, 110‡00.18PE
24‡44.67PS, 111‡49.75PE
28‡43.93PS, 113‡22.08PE
29‡14.42PS, 113‡33.48PE
30‡30.14PS, 114‡16.64PE
28‡43.02PS, 113‡23.32PE
28‡25.21PS, 112‡17.37PE
26‡58.76PS, 111‡20.13PE
23‡57.16PS, 108‡22.14PE
23‡44.23PS, 108‡31.91PE
19‡24.64PS, 110‡30.40PE
12‡14.80PS, 112‡44.27PE
12‡22.76PS, 114‡16.96PE
14‡48.68PS, 114‡16.37PE
16‡34.71PS, 113‡11.98PE
16‡54.81PS, 113‡20.14PE
16‡55.61PS, 114‡15.46PE
16‡54.65PS, 115‡15.90PE
16‡54PS, 115‡31PE
18‡47.93PS, 116‡20.23PE
18‡57.81PS, 116‡23.52PE
a
Water
depth
(m)
81
182
470
2472
2177
1445
678
498
1462
2458
2034
1454
997
1393
1211
1093
1055
1974
841
1010
1738
843
936
3575
3090
2404
2100
4090
2571
3355
2919
2501
1967
1603
1666
1958
502
344
Sample dry
weight
(g)
Pollen
counta
Spore
count
3.44
3.50
1.76
4.00
3.70
2.16
4.25
3.78
3.78
3.55
2.53
3.54
3.88
4.88
3.33
4.36
3.04
3.82
2.00
3.92
4.75
5.53
3.15
2.94
2.27
2.17
3.77
3.15
3.56
2.36
6.09
4.19
3.80
5.73
3.97
4.08
3.92
4.78
109
45
115
114
118
147
156
173
122
43
44
100
153
151
122
196
126
9
105
117
134
108
94
2
37
5
1
3
23
5
2
4
2
4
28
39
244
295
^
^
2
27
56
8
5
^
10
6
6
4
2
1
5
^
2
2
1
5
7
3
2
^
3
^
^
1
30
12
1
^
^
^
3
1
1
1
Excluding unknown grains.
PALBO 2515 17-3-03
Pollen
concentration
(pollen/g)
104
109
638
239
81
1195
1026
805
70
24
38
54
369
165
106
1188
309
15
112
147
101
99
170
3
35
11
1
4
15
10
3
5
5
7
19
23
719
1005
Spore
concentration
(spores/g)
^
^
11
57
39
65
33
^
6
3
5
2
5
1
4
^
5
3
1
6
5
3
4
^
3
^
^
1
20
23
1
^
^
^
2
1
3
3
118
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4. Results
In all 38 core top samples were processed for
this study (see Table 1). All samples were used to
establish pollen and Pteridophyta spore concentrations. However, any sample with a pollen
count of less than 35 pollen grains was omitted
from further analysis (12 samples in total). The
remaining 26 samples were used to establish
the pollen distribution patterns. Samples Fr95-3,
Fr95-11, Fr95-12, Fr96-7, and Fr96-26 have low
pollen sums, between 37 and 45 pollen grains, and
their percentage values can be considered as less
reliable. Therefore, percentage values obtained
from these ¢ve samples were only used in the
description of the pollen assemblages when they
agreed with the percentage values obtained from
nearby samples with higher pollen sums. Selected
results are presented as isopoll (i.e. equal pollen
percentage value) maps (Figs. 3^6), while the
complete results are presented as a pollen percentage diagram in Fig. 7. In the pollen diagram the
core locations are arranged in north^south direction according to their latitude.
4.1. Pollen and Pteridophyta concentrations
The pollen concentrations show a distinct pattern that roughly follows the outline of the continental shelf (see Fig. 3A). The pollen concentration values decrease rapidly with increasing
distance from the shore. The northwestern part
of the WA waters shows higher pollen concentrations than their southwestern portion, with a relatively broad band of values above 1000 pollen
grains per gram being restricted to the northwest.
Values between 100 and 1000 pollen grains per
gram occur in a narrow area within the northwestern sector and the area is located further
from shore than in the southwest. Pteridophyta
spore concentrations are much lower, in general
below ¢ve spores per gram at all locations except
for the most northern ones (Fig. 3B). There, concentration values of more than ten spores per
119
gram occur, and it appears that Pteridophyta
spore concentration values increase with increasing distance from shore.
4.2. Rhizophoraceae
Rhizophoraceae (Fig. 3C) occur only with low
percentages or are absent altogether at most sites,
except for the northern part of the waters of WA
where higher values (up to 3.5%) are encountered.
4.3. Herbs
Asteraceae Tubuli£orae (Fig. 3D) show a gradual increase from the northern waters to approximately 25‡S, from less than 5% to more than
20%. Further south values vary, but are generally
higher than 20%.
The Chenopodiaceae/Amaranthaceae percentages (Fig. 4A) also show a gradual increase.
From the northern waters to approximately 23‡S,
values increase from less than 5% to more than
20%. Further south, percentages gradually decrease to less than 10%.
The percentages for Poaceae (Fig. 4B), on the
other hand, decrease southward. Values greater
than 40% occur in the northern part of the waters
of WA, decreasing to less 10% in the southern
part.
The Cyperaceae percentages (Fig. 4C) vary
more but are, in general, higher o¡shore the
northern part of WA, between 5 and 10%, and
lower southward, mostly below 5%.
Restionaceae (Fig. 4D) occur in low numbers
north of latitude 16‡S, are absent between approximately latitudes 16 and 20‡S, and reach
somewhat higher values southward, with the highest ^ more than 10% ^ at the southernmost site.
4.4. Trees and shrubs
The distribution pattern of Callitris (Fig. 5A) is
patchy and pollen representation is poor. Only
north of latitude 16‡S, around latitude 20‡S as
Fig. 3. Isopoll maps for pollen (A) and Pteridophyta spore (B) concentrations, as well as Rhizophoraceae (C) and Asteraceae Tubuli£orae (D) percentages, in relation to the onshore vegetation. Open circles indicate absence.
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well as around latitude 30‡S Callitris pollen is
recorded with low percentages.
Gyrostemon pollen (Fig. 5B) is present with values of around 5% at most locations. However,
around latitude 19‡S, values of more than 10%
are found.
Acacia pollen (Fig. 5C) is recorded with low
percentages only, generally around 1%, north of
19‡S and between latitudes 20 and 29‡S.
High values for Myrtaceae pollen (Fig. 5D),
greater than 10%, occur north of latitude 16‡S
and south of latitude 28‡S. Values in between
the two areas are below 10%, with values of less
than 5% recorded between latitudes 16 and 20‡S.
Casuarina (Fig. 6A) is absent at latitude 18‡S;
it is present in low abundance, around 1%, at
most other locations. Only between latitudes 26
and 28‡S values greater than 5% are found.
The introduced genus Pinus (Fig. 6B) is present,
but with a patchy distribution north of 25‡S.
South of that latitude Pinus pollen is well represented, and values greater than 10% are recorded
at the two southernmost sites.
121
cladus, Podocarpus) and the exotic taxa (Alnus
and Pinus). The other zones have 29 taxa or less.
4.5.2. Zone B
Between 16 and 18‡30PS, the pollen assemblages
are characterised by the absence of Rhizophoraceae, low Asteraceae Tubuli£orae ( P 6%), high
Poaceae ( P 50%), high Chenopodiaceae/Amaranthaceae (10^17%), and varying Cyperaceae ( P 7%)
values, the absence of Restionaceae, a virtual absence of Callitris, varying Gyrostemon (6^14%),
low Acacia ( P 2%), varying Myrtaceae (1^8%),
and low Casuarina values (0^3%).
4.5.3. Zone C
Characteristic of the pollen assemblages between 18‡30PS and 21‡S are the virtual absence
of Rhizophoraceae, high Asteraceae Tubuli£orae
(10^20%), high Poaceae (30^50%), high Chenopodiaceae/Amaranthaceae (6^30%), varying Cyperaceae (1^4%), low Restionaceae (0^2%), low Callitris (0^1%), varying Gyrostemon (1^14%),
varying Acacia (0^3%), varying Myrtaceae (3^
9%) and low Casuarina values (0^2%).
4.5. Pollen diagram
The pollen diagram (Fig. 7) has been divided
into ¢ve zones. Each zone is brie£y described using only the 11 most common taxa.
4.5.1. Zone A
The pollen assemblages between 12 and 16‡S
are characterised by a low presence of Rhizophoraceae (0^4%), low Asteraceae Tubuli£orae (1^
5%), high Poaceae ( P 60%), low Chenopodiaceae/Amaranthaceae ( 6 5%), and high Cyperaceae values (5^14%), low presence of Restionaceae, the presence of Callitris ( P 2%), varying
presence of Gyrostemon ( P 5%), varying presence
of Acacia (1^5%), high abundance of Myrtaceae
(10^20%), and low presence of Casuarina (0^4%).
These assemblages also show the highest diversity,
with more than 44 taxa not including the Indonesian taxa (Dipterocarpaceae, Dacrycarpus, Phyllo-
4.5.4. Zone D
The pollen assemblages between latitudes 21
and 26‡S are characterised by a virtual absence
of Rhizophoraceae, high Asteraceae Tubuli£orae
(30^38%), lower Poaceae (11^25%), high Chenopodiaceae/Amaranthaceae (14^33%), varying Cyperaceae (1^4%), and low Restionaceae (0^2%),
the absence of Callitris, low Gyrostemon (2^3%),
varying Acacia (1^5%), low Myrtaceae (7^9%),
and low Casuarina values (1^2%).
4.5.5. Zone E
Between 26 and 31‡S, the pollen assemblages
are characterised by the absence of Rhizophoraceae, high Asteraceae Tubuli£orae (18^32%),
varying Poaceae (2^14%), lower Chenopodiaceae/Amaranthaceae (4^9%), low Cyperaceae (2^
4%), higher Restionaceae (1^11%), low Callitris
(0^1%), higher Gyrostemon (3^7%), low Acacia
Fig. 4. Isopoll maps for Chenopodiaceae/Amaranthaceae (A), Poaceae (B), Cyperaceae (C), and Restionaceae (D) percentages, in
relation to the onshore vegetation. Open circles indicate absence.
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123
Fig. 6. Isopoll maps for Casuarina (A) and Pinus (B) percentages, in relation to the onshore vegetation. Open circles indicate absence.
(0^3%), higher Myrtaceae (8^33%), and high Casuarina values (2^5%).
A simple correspondence analysis using all of
these common taxa except Rhizophoraceae seems
to support this zonation, as sites for each zone are
plotted in distinct ¢elds that do not show any
overlap (Fig. 8). The ¢rst four ordination axes
in the correspondence analysis had the following
eigenvalues: Axis 1, eigenvalue 0.218; Axis 2, eigenvalue 0.130; Axis 3, eigenvalue 0.055; Axis 4,
eigenvalue 0.037. According to ter Braak (1987),
only ordination axes with an eigenvalue greater
than 0.3 are considered to explain major variations in the data. We therefore assume that for
this data set the ¢rst four ordination axes do not
explain major variations in the pollen assemblages. As a result, the following discussion makes
largely use of information obtained from the isopoll maps and the pollen diagram.
5. Discussion
Newsome (1999) found a good relationship between the patterns of vegetation and pollen distribution onshore in the semi-arid southwestern
part of WA. Our results indicate that the onshore
distribution of the present-day vegetation is re£ected also by the pollen distribution in the marine sediments o¡shore WA. Vegetation types
such as the northern and southern Eucalyptus forests can easily be recognised by their pollen signal
in the marine sediments, with Myrtaceae percentages of around 20% or higher. The latter can be
Fig. 5. Isopoll maps for Callitris (A), Gyrostemon (B), Acacia (C), and Myrtaceae (D) percentages, in relation to the onshore vegetation. Open circles indicate absence.
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Fig. 7. Pollen diagram showing percentage values for individual taxa from core tops o¡shore WA.
124
PALBO 2515 17-3-03
Fig. 7 (Continued).
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PALBO 2515 17-3-03
125
126
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0.8
Fr95-2
0.6
Fr95-27
♦
>900 mm, summer rain
Fr95-26 ♦
Fr95-4
♦
0.4
Fr95-3
♦
Axis 2
0.2
♦
♦ Fr96-4
♦ Fr96-7
♦ Fr95-8
Fr95-6
♦
300-600 mm, winter rain
Fr95-7
♦ Fr95-5
0
♦Fr95-25
♦
Fr95-11
♦
♦ Fr95-13
400-600 mm, summer rain Fr95-10
-0.2
Fr95-12
-0.4
♦
♦
Fr95-16
♦ Fr96-26
♦
♦
♦
♦ Fr95-14
Fr95-15
♦ Fr95-20
♦ Fr95-18
♦ Fr96-28
Fr95-9
300-400 mm, summer rain
<300 mm
♦ Fr96-29
-0.6
♦ Fr95-17
-0.8
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
Axis 1
Fig. 8. Correspondence plot for the core tops o¡shore WA, using ten of the most common taxa only.
separated from each other by high Poaceae percentages in the marine pollen assemblages derived
from the northern forests and by high Asteraceae
Tubuli£orae percentages in the marine pollen assemblages derived from the southern forests. The
grass-rich vegetation types north of latitude 23‡S,
from the area of predominantly summer rain, are
re£ected by high Poaceae percentages in the marine sediments north of that latitude. The poor
representation of Acacia pollen in the marine sediments makes the recognition of the pollen signal
derived from open Acacia shrublands di⁄cult.
The Acacia shrublands, with grasses north of latitude 23‡S, may be recognised by high Asteraceae
Tubuli£orae, Poaceae and Chenopodiaceae/
Amaranthaceae percentages, while those poor in
grasses ^ south of latitude 23‡S ^ have higher
percentages of Asteraceae Tubuli£orae and Chenopodiaceae/Amaranthaceae, and distinctly lower
ones of Poaceae.
For most of the taxa presented in the isopoll
maps, the distribution in marine sediments seems
to re£ect their onshore distribution. For instance,
the disjunct distribution of Callitris in the marine
sediments seems to re£ect the distribution of Callitris onshore, with Callitris intratropica being restricted to the northern part of the state and Callitris glaucophylla to the central arid area and
(topographically high) ranges, and with C. verrucosa, C. preissii, C. roei and C. drummondii in the
southwest of WA (see Fig. 9). Casuarina occurs in
high percentages only in marine sediments adjacent to the Casuarina shrublands and Casuarina
mixed shrublands in southwestern WA. Rhizophoraceae are best represented in the marine sediments of the northern part of the state, adjacent
to where the most extensive mangrove vegetation
in WA is found. Even the introduced Pinus shows
its highest values (more than 10%) in the waters
southwest of WA, close to the pine plantations
around Perth (see AUSLIG, 1990). The distribution of Restionaceae is restricted to the southwest
of WA (see Fig. 10) south of latitude 23‡S; this is
well re£ected by the pollen distribution in the marine sediments, with the exception of the presence
of Restionaceae pollen in the marine sediments
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127
north of 16‡S. However, pollen from Centrolepidaceae and Restionaceae look very similar and
Centrolepidaceae do occur in the northern part
of the state (see Fig. 11). It is therefore likely
that the ‘Restionaceae’ pollen grains north of
16‡S were actually derived from Centrolepidaceae.
The increase in Pteridophyta spore concentration,
with increasing distance from shore, especially in
the northwest of the WA waters, probably re£ects
an in£ux of spores transported from the Indonesian region into the waters of WA via the LC.
Pteridophyta form an important element of the
ever-wet rainforests of Indonesia and Pteridophyta spores are transported easily by water and
ocean currents (van der Kaars, 2001).
With increasing distance from shore, the composition of the marine pollen assemblages is
clearly in£uenced by di¡erential pollen transport
and longshore currents. For instance, relative
Fig. 10. Distribution of Restionaceae in WA (after Hnatiuk,
1990).
abundance of Chenopodiaceae/Amaranthaceae
seems to decrease with increasing distance from
the shoreline, while the Poaceae values do the
opposite ; they increase with increasing distance
from shore.
The pollen distribution pattern seems to form a
coherent pattern. Even with the limited number of
available samples (38), it is possible to present a
tentative correlation between the marine pollen
distribution in the waters of WA and the onshore
vegetation and climate. Table 2 presents the proposed relationship between the major bioclimatic
zones in WA and the main components of the
marine pollen assemblages (see also Fig. 8).
6. Conclusions
Fig. 9. Distribution of Callitris intratropica and C. glaucophylla in WA (after Hnatiuk, 1990; Bowman and Harris,
1995).
Our pollen concentration map indicates that
suitable core sites for marine palynological re-
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128
S. van der Kaars, P. De Deckker / Review of Palaeobotany and Palynology 124 (2003) 113^129
Fig. 11. Distribution of Centrolepidaceae in WA (after Hnatiuk, 1990).
search o¡shore WA could be found in a relatively
narrow band parallel to the coastline up to 400
km o¡shore in the northwest and 150 km in the
southwest of WA. Suitable sites are mostly located at water depths ranging between 400 and
2500 m.
In general, the bioclimatic zones are well re£ected in the marine pollen assemblages o¡shore
WA. This phenomenon may prove to be a useful
tool for the interpretation of the Late Quaternary
marine palynological records from the region.
The area of WA, with predominantly summer
rain, can be recognised in the marine pollen assemblages north of latitude 23‡S by Poaceae percentages s 30. The area of predominantly winter
rain is re£ected in the marine pollen assemblages
south of latitude 26‡S by Poaceae percentages between 10 and 20. The area with low summer and
winter rainfall between 21 and 26‡S is re£ected by
Asteraceae Tubuli£orae percentages s 30.
The arid central area of WA is re£ected in the
marine pollen assemblages between 18‡30PS and
26‡S by Chenopodiaceae/Amaranthaceae and Asteraceae Tubuli£orae percentages both v 10, with
combined percentages v 30, and Myrtaceae percentages 6 10.
At this stage, we are unable to decipher
whether the pollen distribution in the marine sedi-
Table 2
Proposed relationship between bioclimatic zones in WA and the composition of marine pollen assemblages
Bioclimatic zones
Myrtaceae Poaceae Cyperaceae Asteraceae
Tubuli£orae
(%)
(%)
(%)
(%)
Chenopodiaceae/
Amaranthaceae
(%)
Northern WA: grass-rich open Eucalyptus forests and open s 10
Eucalyptus woodlands; annual precipitation s 900 mm,
predominantly summer rain
40^60
5^10
65
6 10
Northwestern WA: open Eucalyptus woodlands with Acacia, 6 10
and grasslands; annual precipitation 400^600 mm,
predominantly summer rain
P 50
P5
P5
10^20
Northwestern WA: open Acacia shrublands with grasses
and grasslands; annual precipitation 300^400 mm,
predominantly summer rain
30^50
65
10^20
10^30
Central WA: open Acacia shrublands; annual precipitation 5^10
6 300 mm
6 25
65
30^40
15^35
Southwestern WA: open Eucalyptus forests and mixed
shrublands; annual precipitation 300^600 mm,
predominantly winter rain
10^20
65
20^30
6 10
6 10
s 10
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ments is principally caused by aeolian or by £uvial processes. We expect that close to shore in the
northern regions of WA, where rivers contribute
to a large in£ux of freshwater during the summer
rainy season, pollen are principally transported by
water as well as wind. The pollen distribution
further o¡shore is likely to be predominantly of
aeolian origin.
The LC, which follows the outline of WA and
partly originates from the Indonesian Through£ow, is more than likely the ‘carrier’ of Pteridophyta spores of Indonesian origin.
Acknowledgements
We would like to thank Gary Swinton for
drafting the maps. This research was supported
by a Monash Logan Research Fellowship to
S.v.d.K. The cores were obtained by P.D.D.
with help of several ARC grants and access to
the Australian national facility RV Franklin. We
thank the reviewers for their many useful comments.
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