Directory UMM :Data Elmu:jurnal:O:Organic Geochemistry:Vol31.Issue4.2000:

Organic Geochemistry 31 (2000) 287±294
www.elsevier.nl/locate/orggeochem

Molecular-isotopic stratigraphy of long-chain n-alkanes in
Lake Baikal Holocene and glacial age sediments
David Brincat a,*, Keita Yamada a, Ryoshi Ishiwatari a, Hitoshi Uemura b,
Hiroshi Naraoka a
a

Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Minami-Ohsawa 1-1, Hachioji,
Tokyo 192-0397, Japan
b
Department of Environmental Health, Kanagawa Prefectural Public Health Laboratory, Nakao 1-1-1, Asahi-ku,
Yokohama 241-0815, Japan
Received 8 January 1999; accepted 16 December 1999
(returned to author for revision 1 May 1999)

Abstract
The molecular distribution and the carbon-isotopic composition (d13C) of n-alkanes extracted from a Lake Baikal
core spanning the last 20 kyr of sediment accumulation have been investigated. A terrestrial origin has been inferred for
the odd carbon-numbered long-chain (>C27) n-alkanes, on the basis of the observed high CPI27-33 values (range: 8.7±

10.8) typical of n-alkanes derived from leaf waxes of higher plants. A shift in the abundance of n-C27 alkane relative to
n-C31 homologue is observed across the late Pleistocene glacial±Holocene interglacial climate change, perhaps indicative of the climate-induced vegetational change previously deduced from palynological analyses. Compound-speci®c
isotope analyses indicate remarkably uniform d13C values in the range of ÿ31.0 to ÿ33.5% for the leaf-wax C27±C33 nalkanes in the entire cored sequence. Such an isotopic compositional range is characteristic for n-alkanes biosynthesized by plants utilizing the C3 photosynthetic pathway. Our data suggest that the observed 13C-enrichment in the bulk
organic matter in the glacial age sediments, relative to d13C values of total organic carbon in the Holocene section, is
therefore unlikely to be attributed to an expansion of C4-type vegetation in the Baikal watershed during the late
Pleistocene glacial interval. # 2000 Elsevier Science Ltd. All rights reserved.
Keywords: Lake Baikal; Long-chain n-alkanes; Carbon-isotopic compositions; Lacustrine sediments; Paleoclimate

1. Introduction
Organic matter preserved in lake sediments represents
an input from the remains of aquatic organisms as well
as plants which inhabited the surrounding land (Meyers
and Ishiwatari, 1995). The characterization of the stable
carbon-isotopic composition of lacustrine organic matter has been shown to re¯ect variations in limnological
factors resulting from paleoclimatic changes (Stuiver,
1975; HaÊkansson, 1985).
The carbon-isotopic composition of sedimentary
organic matter is useful in identifying organic material
* Corresponding author.
E-mail address: davidbrincat@netscape.net (D. Brincat).

originating from land plants with di€erent metabolic
pathways (e.g. Meyers, 1994). Carbon-isotopic analyses
of bulk tissues from plants utilizing di€erent pathways
of carbon ®xation revealed that those plants which
employ the Calvin cycle pathway (C3 plants) during
photosynthesis are more depleted in 13C than those
plants which use the Hatch-Slack pathway (C4 plants)
(Smith and Epstein, 1971). Indeed, changes in 13C/12C
ratio of organic matter in lake sediments were partly
attributed to a climate-forced change in the type of
watershed ¯ora, re¯ecting varying detrital input of C3
relative to C4 plants (Talbot and Johannessen, 1992;
Street-Perrott et al., 1997).
Lake Baikal, located in southeastern Siberia (Russia),
has been the target of drilling activities during this

0146-6380/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved.
PII: S0146-6380(99)00164-3

288

D. Brincat et al. / Organic Geochemistry 31 (2000) 287±294

decade in an e€ort to recover sediment cores suitable for
paleoclimatic studies of this high latitude, continental
interior location (Colman et al., 1992). Variation in the
isotopic composition of the organic carbon in a short
core recovered from the northern basin of Lake Baikal
(Qiu et al., 1993) has been attributed to a change in the
relative abundance of C3 versus C4 vegetation in the
lake watershed (X. Chen, 1992, cited in Qiu et al., 1993).
The present study evaluates the input of terrestrial
vegetation upon d13C values of bulk organic matter in
Lake Baikal sediments. The approach adopted in this
work involves the determination of the isotopic composition of individual odd carbon-numbered long-chain
(>C27) normal (n-) alkanes as a proxy indicator of input
from terrestrial plants utilizing di€erent metabolic pathways. Several studies have reported the occurrence of
such components, as the major n-alkanes, in leaf waxes of
terrestrial plants (e.g. Eglinton and Hamilton, 1967;

StraÂnsky et al., 1967; Tulloch, 1976). The measurement of
the isotopic composition at the molecular level, using gas
chromatography±isotope ratio mass spectrometry (GC±
IRMS; Hayes et al., 1990), has greatly enhanced the ability to assess the source input of the individual components in the sedimentary environment (Freeman et al.,
1990; Rieley et al., 1991). For example, the distinctive
isotopic di€erence observed in the bulk tissue between C3
and C4 plants is also re¯ected at the molecular level in the
13
C-enriched n-alkanes derived from C4 plants relative to
the isotopically lighter homologues biosynthesized by C3
plants (Collister et al., 1994; Lichtfouse et al., 1994;
Yamada, 1997). Such isotopic di€erences at the molecular level have been successfully exploited in a recent
reconstruction of the temporal variation in the relative
input of C4 versus C3 plant detritus in lake sediments from
eastern Africa (Street-Perrott et al., 1997). However, to
the best of our knowledge, this is the ®rst report of compound-speci®c isotope analyses of individual lipids
extracted from Lake Baikal sediments.

(Takemura et al., 1992). The cored interval has an estimated basal age of 19.8 kyr (Ogura et al., 1992). On the
basis of the available age determinations, it can be

inferred that the upper diatomaceous section is of
Holocene age whereas the lower clayey sequence was
deposited during the late Pleistocene glacial regime
representing the last glacial maximum (LGM; 14±22 kyr
B.P.; Crowley and North, 1991). The age estimates for
the uppermost sediments, characterized by contrasting
lithologies, compare very favorably with the radiocarbon-based chronology for a suite of similar cores
recovered from other sites within Lake Baikal, namely
the Selenga Delta area (southern basin) and Academician Ridge region (Carter and Colman, 1994).
2.2. Previous analyses
Elemental analyses and isotopic composition of total
organic carbon (d13CTOC) for 27 sampled intervals from
core 323-PC1 have already been reported (Ishiwatari et al.,
1992), and are displayed here in Fig. 1 together with the
estimated age determinations of Ogura et al. (1992). Following the initial bulk analyses, nineteen sediment samples
were further selected for more detailed molecular studies
(Ishiwatari et al., 1993, 1995). These samples are indicated
with a ®lled circle in Fig. 1. Details of the extraction procedures have been described elsewhere (Ishiwatari et al.,
1993) and can be summarized as follows. Wet sediment
samples were saponi®ed with 0.5M KOH in methanol

under re¯ux for 2 h. Neutral compounds were recovered
with n-hexane: diethylether (9:1, v/v) and separated into
lipid classes (saturated and unsaturated hydrocarbons,
aromatic hydrocarbons, ketones and alcohols) by silica-gel
(deactivated with 5% H2O w/w) column chromatography.
Alkenes were removed from the hydrocarbon fraction
using a column of AgNO3±impregnated (10% w/w) silicagel. The saturated hydrocarbon fractions obtained by
these procedures were made available for the present study
for the determination of the carbon-isotopic composition
of individual compounds.

2. Materials and methods
2.3. Molecular analyses of n-alkanes
2.1. Sediment samples
The piston core used in this study (Core 323-PC1) was
recovered by a team of Russian and American scientists
(Colman et al., 1992) from the northern basin of Lake
Baikal (55.5347 N, 109.5213 E; water depth 710 m; core
length 461 cm). The cored sequence consists of a
massive clay±silty clay deposit with intercalations of

®ne±medium sand layers (Takemura et al., 1992). A
distinctive change in lithological properties is present at
a depth of ca. 150 cm, with the upper layer consisting of
silt size sediments enriched in diatom fossil remains
relative to the lower, more ®ne-grained clayey sediments,
where very few diatom remains have been observed

The saturated hydrocarbons of all 19 samples were
analyzed by gas chromatography (GC) using a HewlettPackard 5890 series II gas chromatograph equipped
with an on-column injector and a ¯ame ionization
detector. The n-alkanes were separated on a J & W
Scienti®c DB-5 fused silica capillary column (30 m 
0.32 mm i.d.; 0.25 mm ®lm thickness). Helium was used
as carrier gas. The GC oven temperature was programmed as follows: injection at 50 C, 30 C/min to
120 C, 5 C/min to 310 C, isothermal for 17 min. Concentrations of the various n-alkane homologues were
calculated by comparing the peak area of the appropriate compound relative to that of the co-injected

D. Brincat et al. / Organic Geochemistry 31 (2000) 287±294

289

Fig. 1. Depth pro®les of (a) abundance of total organic carbon (wt%); and (b) isotopic composition of total organic carbon for
sediment samples from Lake Baikal core 323-PC1 (after Ishiwatari et al., 1992). Samples represented by a ®lled circle were previously
selected for molecular studies. Estimated ages are from Ogura et al. (1992). Lithological description is after Takemura et al. (1992),
with the horizontal line at 150 cm depth representing a climate-related lithological boundary, separating an upper diatomaceous clay
section from the lower clayey sediments. The vertical broken lines in Fig. 1b indicate average d13CTOC values in glacial age sediments
(ÿ24.1%) and Holocene section (ÿ27.3%).

deuterated n-alkane C24D50. The response factor of
individual n-alkanes relative to the standard was
assumed to be unity.
Compound identi®cation was based on data from
electron±impact gas chromatography±mass spectrometry (GC±MS). The GC±MS system employed was a
Hewlett-Packard 6890 series gas chromatograph ®tted
with a split/splitless injector (280 C) and interfaced with
a Hewlett-Packard 6890 series mass selective detector
(MSD), which was operated in full scan mode. Separation was performed on a DB-5 fused silica capillary
column (30 m  0.32 mm i.d.; 0.25 mm ®lm thickness).
Helium was used as carrier gas, with the oven temperature program being the same as that described for the
GC analyses.

2.4. Molecular sieve treatment for isolation of n-alkanes
for stable carbon isotope analysis
Saturated hydrocarbon fractions containing signi®cant amounts of branched and cyclic compounds
were treated with 5 A molecular sieves (Yamada et al.,
1994) in order to isolate the n-alkanes for accurate isotopic measurements. Such an isolation procedure was
not observed to a€ect the d13C values of the individual

n-alkanes (Yamada et al., 1994). Brie¯y, the saturated
hydrocarbon fractions dissolved in n-hexane were evaporated to dryness under nitrogen. Subsequently, the
saturated hydrocarbons were re-dissolved in 1 ml of isooctane and ca. 200 mg of preheated (350 C for 5 h) 5 A
molecular sieve pellets were added to the vial, which was
kept at room temperature for 12 h. The n-alkanes were
then recovered with n-hexane after dissolution of the
molecular sieves with 47% hydro¯uoric acid solution.
GC analyses of the non-adduct (branched and cyclic)
fraction did not reveal the presence of n-alkanes. Moreover, a procedural blank carried out during the isolation
of n-alkanes from the samples did not indicate the
presence of any contamination.
2.5. Gas chromatography±isotope ratio mass
spectrometry

The carbon-isotopic values of individual n-alkanes
were determined using a gas chromatography±isotope
ratio mass spectrometry (GC±IRMS) system. A HewlettPackard 5890 series II gas chromatograph was used,
equipped with an on-column injector, and interfaced
with a Finnigan MAT delta-S mass spectrometer via a
combustion furnace (840 C) packed with CuO and Pt

290

D. Brincat et al. / Organic Geochemistry 31 (2000) 287±294

wires. The n-alkanes were separated on an HP-5 trace
analysis fused silica capillary column (60 m  0.32 mm
i.d.; 0.25 mm ®lm thickness). Helium was used as carrier
gas. The GC oven temperature was programmed from
50 to 120 C at 30 C/min, from 120 to 310 C at 5 C/
min, and then held isothermally at 310 C for 23 min.
The d13C values were calibrated by co-injected n-alkanes
C16D34, C24D50 and C38H78. All carbon isotope ratios
are expressed as per mil (%) relative to the Pee Dee

Belemnite (PDB) standard. Data were acquired and
processed using ISODAT software. Reported carbonisotopic compositions represent averaged values of triplicate analyses. Standard deviations were generally 4
‹ 0.5%.

3. Results and discussion
3.1. Molecular distribution of n-alkanes
The gas chromatograms of the saturated hydrocarbon
fraction extracted from two sediment samples deposited
under di€erent climatic conditions (Holocene and
LGM) are displayed in Fig. 2. A unimodal distribution
of n-alkanes is observed in all samples analyzed, maximizing at either n-C27 or n-C31. Such a molecular feature in sediments from the strongly oligotrophic Lake
Baikal (Weiss et al., 1991) has been previously observed
in sediments deposited in other oligotrophic lakes
(Cranwell, 1982; Kawamura and Ishiwatari, 1985). The

concentrations of the odd carbon-numbered C27 to C33
n-alkanes extracted from core 323-PC1 are listed in
Table 1, together with other data related to the n-alkane
distribution.
The long-chain n-alkanes are characterized by a pronounced odd-carbon predominance. The carbon preference index (CPI) for n-alkanes in the range C27±C33
varies between 8.7 and 10.8 for the samples analyzed
here (Table 1). The extent of predominance of the odd
carbon-numbered n-C27 to n-C33 homologues is within
the range observed for n-alkanes derived from terrestrial
plant epicuticular leaf waxes (Eglinton and Hamilton,
1967; Tulloch, 1976; Collister et al., 1994), thereby
suggesting a higher plant origin for the long-chain
n-alkanes. This source inference is supported by the
similarity in the CPI27-33 values observed in the lake
sedimentary record and in extracts from a peat bog
interval sampled close to the shoreline of Baikal (Brincat et al., unpublished data).
As indicated in Fig. 2, the distribution of n-alkanes in
the glacial age sediment is dominated by C31 homologue
whereas C27 component is the predominant n-alkane in
the Holocene age sediment. An insight into the downcore variation of the dominant n-alkane homologue is
provided by evaluation of the C27 n-alkane/C31 n-alkane
ratio (Fig. 3). Sediments dated to a glacial age are uniformly dominated by C31 n-alkane. However, the lithological boundary at ca. 150 cm depth marks a change
in the distribution pattern of n-alkanes, with the C27
component becoming increasingly important towards

Fig. 2. Gas chromatograms of the saturated hydrocarbon fraction extracted from Lake Baikal sediment samples deposited during (a)
Holocene and (b) last glacial maximum. The peak marked with (*) denotes the deuterated n-alkane internal standard C24D50.

291

D. Brincat et al. / Organic Geochemistry 31 (2000) 287±294

Table 1
Concentration data for the long-chain odd carbon-numbered n-alkanes analyzed in this study as a function of depth in Lake Baikal
core 323-PC1. The CPI values for the range C27±C33 n-alkanes are also provided
Depth (cm)

TOC (wt%)a

n-C27 mg/g OCb

n-C29 mg/g OC

n-C31 mg/g OC

n-C33 mg/g OC

CPI27ÿ33c

9.5
44.5
55.8
74.8
95.3
120.0
139.0
176.0
200.3
218.0
244.3
274.5
291.3
329.8
350.3
378.0
399.5
419.8
443.8

2.09
2.85
2.72
2.41
1.39
1.02
0.63
0.36
0.31
0.29
0.28
0.25
0.29
0.28
0.26
0.25
0.25
0.26
0.23

49.9
30.3
46.8
63.3
221.9
29.0
58.1
39.9
29.2
34.6
43.2
61.5
37.8
64.8
44.9
56.3
63.6
80.3
121.1

34.0
18.3
30.0
43.1
158.0
22.2
48.1
39.6
31.7
41.5
52.4
72.1
41.6
76.6
54.4
67.2
73.4
95.9
147.7

28.8
14.9
27.1
37.6
163.6
20.0
45.6
44.7
36.6
49.6
61.2
84.1
46.8
90.2
64.6
79.8
81.7
111.1
174.1

11.0
6.2
10.7
14.0
63.3
9.2
16.3
12.7
10.7
14.3
17.5
22.2
13.5
25.6
17.1
22.9
23.1
34.4
51.2

9.5
9.6
9.8
10.4
10.8
8.9
9.8
9.2
9.6
10.2
10.4
10.2
10.2
10.1
10.0
10.1
10.0
8.7
9.9

a
b
c

Total organic carbon data from Ishiwatari et al. (1992).
Concentration expressed as
ÿ mg/g organic carbon.


CPI27-33=0.5*C27;29;31;33 1=C26;28;30;32 ‡ 1=C28;30;32;34 .

Fig. 3. Depth pro®le of the variation in the abundance of C27 relative to C31 n-alkanes together with a summary of the palynological
analyses of Fuji (1992) for Lake Baikal core 323-PC1. The change in lithology described by Takemura et al. (1992) is represented by
the horizontal line at 150 cm depth.

292

D. Brincat et al. / Organic Geochemistry 31 (2000) 287±294

the top of the core. Palynological analyses of these
sediments (Fuji, 1992) revealed abundant pollen grains
typical of present-day forest vegetation surrounding
Lake Baikal in the upper sedimentary section (Holocene). On the other hand, signi®cantly fewer pollen
grains were observed in the lower section, with the pollen assemblage being indicative of the presence of herbaceous vegetation in the Lake Baikal watershed during
the LGM (Fuji, 1992). Therefore, on the basis of the
pollen data, it is suggested that the depth variations in
the relative abundance of the high molecular weight nalkane homologues re¯ect a change in the types of
vegetation in the lake watershed.
3.2. Carbon-isotopic composition of n-alkanes
Compound-speci®c d13C values of the odd carbonnumbered C27 to C33 n-alkanes are listed in Table 2. The
downcore average d13C values indicate that the nalkanes get systematically more 13C depleted with
increasing chain length, a feature also noted for longchain n-alkanes in other lake sediments (Rieley et al.,
1991; Spooner et al., 1994; Ficken et al., 1998). Downcore d13C pro®les of the individual n-alkanes are shown

in Fig. 4. In spite of the signi®cant change in the pollen
record and the n-alkane distribution observed across the
late Pleistocene glacial±Holocene interglacial climate
transition, the d13C pro®les of the high molecular weight
n-alkanes are observed to be remarkably homogeneous
as a function of core depth, with the maximum downcore range of d13C values being 1.6, 0.9, 1.2 and 1.5%
for C27, C29, C31 and C33 n-alkanes, respectively (Table
2).
Moreover, the d13C values of C27 to C33 n-alkanes
vary from ÿ31.0 to ÿ33.5%, well within the range for
leaf-wax n-alkanes biosynthesized by C3 plants (Rieley
et al., 1991; Collister et al., 1994; Yamada, 1997).
Hence, the observed range of the carbon-isotopic composition of the long-chain n-alkanes suggests the prevalence of C3-type vegetation in the Lake Baikal
watershed even during the glacial interval. This inference is corroborated by d13C values of the long-chain
n-C29 and n-C31 alkanes extracted from a glacial age
peat bog interval collected from the lakeside of Baikal
(d13C range: ÿ30.3 to ÿ32.4%; Brincat et al., unpublished data), which are signi®cantly depleted in 13C
relative to the isotopic composition reported for the
corresponding n-alkanes extracted from C4 plants (d13C

Table 2
Carbon-isotopic data for the individual long-chain odd carbon-numbered n-alkanes as a function of depth in Lake Baikal core 323PC1. The isotopic values represent the average of triplicate analyses. Also shown is the isotopic composition of the corresponding total
organic carbon (after Ishiwatari et al., 1992)
Depth (cm)

TOC d13C (%)a

n-C27 d13C (%)

sb

n-C29 d13C (%)

s

n-C31 d13C (%)

s

n-C33 d13C (%)

s

9.5
44.5
55.8
74.8
95.3
120.0
139.0
176.0
200.3
218.0
244.3
274.5
291.3
329.8
350.3
378.0
399.5
419.8
443.8

ÿ26.2
ÿ26.6
ÿ26.3
ÿ25.6
ÿ26.1
ÿ30.3
ÿ26.1
ÿ25.4
ÿ22.8
ÿ23.7
ÿ24.9
ÿ24.9
ÿ24.9
ÿ23.6
ÿ24.0
ÿ23.9
ÿ24.6
ÿ22.2
ÿ24.4

ÿ31.1
ÿ31.7
ÿ32.1
ÿ31.5
ÿ31.3
ÿ32.2
ÿ32.3
ÿ32.6
ÿ31.8
ÿ31.4
ÿ31.8
ÿ31.5
ÿ31.7
ÿ32.0
ÿ31.4
ÿ31.9
ÿ31.3
ÿ31.7
ÿ31.0

0.2
0.0
0.2
0.2
0.2
0.2
0.3
0.3
0.2
0.2
0.1
0.1
0.3
0.3
0.3
0.3
0.3
0.2
0.1

ÿ31.9
ÿ32.0
ÿ32.2
ÿ32.2
ÿ32.2
ÿ32.2
ÿ32.0
ÿ31.8
ÿ32.0
ÿ32.0
ÿ32.1
ÿ31.8
ÿ31.8
ÿ32.3
ÿ31.8
ÿ32.4
ÿ31.7
ÿ32.4
ÿ31.5

0.1
0.1
0.4
0.4
0.4
0.2
0.1
0.5
0.1
0.1
0.2
0.1
0.3
0.3
0.2
0.3
0.2
0.2
0.1

ÿ32.7
ÿ32.7
ÿ32.8
ÿ33.0
ÿ33.0
ÿ32.9
ÿ32.6
ÿ32.4
ÿ32.9
ÿ32.8
ÿ32.7
ÿ32.2
ÿ32.0
ÿ32.7
ÿ31.8
ÿ33.0
ÿ31.9
ÿ32.9
ÿ31.9

0.2
0.2
0.6
0.6
0.5
0.4
0.3
0.4
0.2
0.0
0.1
0.2
0.5
0.2
0.4
0.5
0.2
0.1
0.1

ÿ32.8
ÿ32.9
ÿ32.6
ÿ33.0
ÿ33.0
ÿ32.0
ÿ33.4
ÿ33.1
ÿ32.8
ÿ32.3
ÿ32.8
ÿ32.9
ÿ32.9
ÿ33.2
ÿ32.8
ÿ33.5
ÿ32.5
ÿ33.0
ÿ33.0

0.6
0.2
0.9
0.7
0.3
0.8
0.2
0.7
0.5
0.7
0.1
1.0
0.5
0.1
0.5
0.3
0.4
0.2
0.2

ÿ31.7
1.6

0.4

ÿ32.0
0.9

0.2

ÿ32.6
1.2

0.4

ÿ32.9
1.5

0.4

8.1

Averagec

d (%)d
a
b
c
d

Bulk isotopic values from Ishiwatari et al. (1992).
Represents‹1 standard deviation from the mean of triplicate analyses.
Average=downcore averaged isotopic composition for individual n-alkanes.

d(%)=maximum observed range of d13C values.

D. Brincat et al. / Organic Geochemistry 31 (2000) 287±294

293

previously recognized by palynological analyses of the
same samples we analyze here.
Compound-speci®c isotopic analyses revealed
remarkably homogeneous downcore d13C pro®les for
the leaf-wax n-alkanes in both Holocene and LGM
sediments. The isotopic compositional range of ÿ31.0 to
ÿ33.5% for C27±C33 n-alkanes in the entire cored
sequence represents an input from C3-type plants.
Therefore, the observed 13C-enrichment in the bulk
organic matter in the glacial age sediments is unlikely to
be due to an expansion of C4-type vegetation in the
Baikal watershed during the late Pleistocene glacial
interval.

Acknowledgements
We are grateful to Prof. S. Horie for providing access
to the Lake Baikal samples from core 323-PC1. The
authors would also like to acknowledge Dr. James W.
Collister and Dr. Fred Prahl for reviewing the manuscript and providing many helpful suggestions. This
work was supported by a research grant from the Ministry of Education, Science and Culture of Japan.
Fig. 4. d13C pro®les of the leaf-wax C27 to C33 n-alkanes as a
function of depth in Lake Baikal core 323-PC1. The horizontal
line represents a change in lithology at 150 cm depth (Takemura et al., 1992).

Associate EditorÐJ.W. Collister

References
range: ÿ18.4 to ÿ24.5%; Collister et al., 1994; Lichtfouse et al., 1994; Yamada, 1997). Therefore, our d13C
data for the leaf-wax n-alkanes suggest that the
observed 13C-enrichment in the bulk organic matter in
the glacial age sediments, relative to d13CTOC values in
the Holocene section (Fig. 1b), is unlikely to be attributed to a spread of C4-type vegetation in the Baikal
watershed during the glacial interval.

4. Conclusions
Molecular characterization of n-alkanes extracted
from Lake Baikal sediments, with an estimated basal
age of ca. 20 kyr for the cored interval, revealed a high
predominance of odd carbon-numbered n-alkanes in the
C27±C33 range, consistent with a terrestrial plant epicuticular wax origin. Moreover, a systematic change in the
most abundant n-alkane was also noted as a function of
core depth, with the LGM section being dominated by
n-C31 alkane whereas the Holocene age sediments by nC27 homologue. Such a change in the distribution pattern of the long-chain n-alkanes recorded in the lake
sediments could be indicative of the climate-induced
change in the type of terrestrial vegetation

Carter, S.J., Colman, S.M., 1994. Biogenic silica in Lake Baikal
sediments: results from 1990±1992 American cores. Journal
of Great Lakes Research 20, 751±760.
Chen, X., 1992. Paleolimnological and paleoclimatic signals
from Asian lakes: Lake Baikal, Russia, and lake systems of
China. Ph.D. thesis, University of South Carolina, USA.
Collister, J.W., Rieley, G., Stern, B., Eglinton, G., Fry, B.,
1994. Compound-speci®c d13C analyses of leaf lipids from
plants with di€ering carbon dioxide metabolisms. Organic
Geochemistry 21, 619±627.
Colman, S.M., Karabanov, E.B., Williams, D.F., Hearn, Jr.,
P.P., King, J.W., Orem, W.H. et al., 1992. Lake Baikal
paleoclimate project, southeastern Siberia: initial dating and
paleoenvironmental results. In: Horie, S., Toyoda, K. (Eds.),
International Project on Paleolimnology and Late Cenozoic
Climate Newsletter No. 6. pp. 30±39.
Cranwell, P.A., 1982. Lipids of aquatic sediments and sedimenting particulates. Progress in Lipid Research 21, 271±
308.
Crowley, T.J., North, G.R., 1991. Paleoclimatology. Oxford
University Press, New York.
Eglinton, G., Hamilton, R.J., 1967. Leaf epicuticular waxes.
Science 156, 1322±1335.
Ficken, K.J., Street-Perrott, F.A., Perrott, R.A., Swain, D.L.,
Olago, D.O., Eglinton, G., 1998. Glacial/interglacial variations in carbon cycling revealed by molecular and isotope
stratigraphy of Lake Nkunga, Mt. Kenya, East Africa.
Organic Geochemistry 29, 1701±1719.

294

D. Brincat et al. / Organic Geochemistry 31 (2000) 287±294

Freeman, K.H., Hayes, J.M., Trendel, J.-M., Albrecht, P., 1990.
Evidence from carbon isotope measurements for diverse
origins of sedimentary hydrocarbons. Nature 343, 254±256.
Fuji, N., 1992. Palynological investigation of Core, 323-PC1
from Lake Baikal, southeastern Siberia. In: Horie, S.,
Toyoda, K. (Eds.), International Project on Paleolimnology
and Late Cenozoic Climate Newsletter No. 6. pp. 103±115.
HaÊkansson, S., 1985. A review of various factors in¯uencing
the stable carbon isotope ratio of organic lake sediments by
the change from glacial to post-glacial environmental conditions. Quaternary Science Reviews 4, 135±146.
Hayes, J.M., Freeman, K.H., Popp, B.N., Hoham, C.H., 1990.
Compound-speci®c isotopic analyses: a novel tool for reconstruction of ancient biogeochemical processes. In: Durand,
B., Behar, F. (Eds.), Advances in Organic Geochemistry 1989.
Pergamon Press, Oxford. Organic Geochemistry 16, 1115±1128.
Ishiwatari, R., Uemura, H., Yamamoto, S., 1993. Organic
matter records of environmental changes in Lake Baikal
sediments. 3: molecular characterization of organic compounds in Core 323-PC1 by high-resolution gas chromatography-mass spectrometry. In: Horie, S. (Ed.), International
Project on Paleolimnology and Late Cenozoic Climate
Newsletter No. 7. pp. 56±65.
Ishiwatari, R., Uzaki, M., Yamada, K., Ogura, K., 1992.
Organic matter records of environmental changes in Lake
Baikal sediments. 1: carbon isotopes, organic carbon and
nitrogen. In: Horie, S., Toyoda, K. (Eds.), International
Project on Paleolimnology and Late Cenozoic Climate
Newsletter No. 6. pp. 80-88.
Ishiwatari, R., Yamamoto, S., Uemura, H., 1995. Organic
matter records of environmental changes in Lake Baikal
sediments. 4: temporal variations of biomarker compounds
in Core 323-PC1 in the past 20 kyr. In: Horie, S. (Ed.),
International Project on Paleolimnology and Late Cenozoic
Climate Newsletter No. 9. pp. 67±70.
Kawamura, K., Ishiwatari, R., 1985. Distribution of lipid-class
compounds in bottom sediments of freshwater lakes with
di€erent trophic status, in Japan. Chemical Geology 51, 123±
133.
Lichtfouse, EÂ, Derenne, S., Mariotti, A., Largeau, C., 1994.
Possible algal origin of long chain odd n-alkanes in immature
sediments as revealed by distributions and carbon isotope
ratios. Organic Geochemistry 22, 1023±1027.
Meyers, P.A., 1994. Preservation of elemental and isotopic
source identi®cation of sedimentary organic matter. Chemical Geology 114, 289±302.
Meyers, P.A., Ishiwatari, R., 1995. Organic matter accumulation records in lake sediments. In: Lerman, A., Imboden, D.,
Gat, J. (Eds.), Physics and Chemistry of Lakes. SpringerVerlag, Berlin, pp. 279±328.
Ogura, K., Ishiwatari, R., Nakamura, T., 1992. A preliminary
report on 14C ages of a 4.6m long core sample of Lake Baikal.

In: Horie, S., Toyoda, K. (Eds.), International Project on
Paleolimnology and Late Cenozoic Climate Newsletter No.
6. pp. 123±124.
Qiu, L., Williams, D.F., Gvorzdkov, A., Karabanov, E., Shimaraeva, M., 1993. Biogenic silica accumulation and paleoproductivity in the northern basin of Lake Baikal during the
Holocene. Geology 21, 25±28.
Rieley, G., Collier, R.J., Jones, D.M., Eglinton, G., Eakin,
P.A., Fallick, A.E., 1991. Sources of sedimentary lipids
deduced from stable carbon-isotope analyses of individual
compounds. Nature 352, 425±427.
Smith, B.N., Epstein, S., 1971. Two categories of 13C/12C ratios
for higher plants. Plant Physiology 47, 380±384.
Spooner, N., Rieley, G., Collister, J.W., Lander, M., Cranwell,
P.A., Maxwell, J.R., 1994. Stable carbon isotopic correlation
of individual biolipids in aquatic organisms and a lake bottom sediment. Organic Geochemistry 21, 823±827.
StraÂnskyÂ, K., Streibl, M., Herout, V., 1967. Distribution of wax
hydrocarbons in plants at di€erent evolutionary levels.
Collection of Czechoslovak Chemical Communications 32,
3213±3220.
Street-Perrott, F.A., Huang, Y., Perrott, R.A., Eglinton, G.,
Barker, P., Khelifa, L.B. et al., 1997. Impact of lower atmospheric carbon dioxide on tropical mountain ecosystems.
Science 278, 1422±1426.
Stuiver, M., 1975. Climate versus changes in 13C content of the
organic component of lake sediments during the Late Quarternary. Quaternary Research 5, 251±262.
Takemura, K., Marui, A., Horie, S., 1992. Comments on the
core sample 323-PC1 of Lake Baikal from the sedimentological viewpoint. In: Horie, S., Toyoda, K. (Eds.), International Project on Paleolimnology and Late Cenozoic Climate
Newsletter No. 6. pp. 72±79.
Talbot, M.R., Johannessen, T., 1992. A high resolution
palaeoclimatic record for the last 27,500 years in tropical
West Africa from the carbon and nitrogen isotopic composition of lacustrine organic matter. Earth and Planetary Science Letters 110, 23±37.
Tulloch, A.P., 1976. Chemistry of waxes of higher plants. In:
Kolattukudy, P.E. (Ed.), Chemistry and Biochemistry of
Natural Waxes. Elsevier, Amsterdam, pp. 235±287.
Weiss, R.F., Carmack, E.C., Koropalov, V.M., 1991. Deepwater renewal and biological production in Lake Baikal.
Nature 349, 665±669.
Yamada, K., 1997. Geochemical study of stable carbon isotopic composition of individual hydrocarbons in recent sediments Ph.D. thesis, Tokyo Metropolitan University, Japan.
Yamada, K., Uzaki, M., Kon, M., Naraoka, H., Ishiwatari, R.,
1994. Molecular sieve isolation technique for use in stable
carbon isotope analysis of individual long-chain n-alkanes in
crude oil. Journal of the Mass Spectrometry Society of Japan
42, 237±246, (in Japanese).