precipitation to the ostracod valve, i.e. (1) the major
hydrological processes controlling the present and past links
between d
18 O L and d
18 O P, and (2) the effects related to the
valve formation (temperature-dependent fractionation and
vital effects). Most of the data used to illustrate those processes are from lakes situated within a small region of
southern Germany and are the author’s published or
unpublished material. The data was collected to support and
refine the quantitative interpretation of the d
18 O records from
sub-recent and late Glacial to Holocene mainly from one of
those lakes (Ammersee), which is presented in the fourth
part of this chapter. The reason for this regional concentration is the lack of case studies as comprehensive from other
regions, combining investigation of the modern isotope
hydrology, the physical limnology, and the ostracod geochemistry within the settings of a fossil record. The last part
of the chapter aims to show how d
18 O P reconstruction from
deep lake ostracods could be further developed and exploited to address secondary effects in more complex archives.
This chapter is an update of a previously published book
section (von Grafenstein 2002). It incorporates major
advances concerning our understanding of the oxygen isotope signal preserved in ostracod valves and gives an overview of new and upcoming records in Europe.
Existing Deep-Lake Oxygen-Isotope Records
The first published ostracod stable isotope record was from
Lake Erie (Fritz et al. 1975). This showed a 4‰ shift at the
late Wisconsin to Holocene transition, which was interpreted
as a temperature controlled change in d
18 O P . Later,
deep-lake oxygen-isotope ostracod records from the Great
Lakes demonstrated that the Late Wisconsin and Holocene
re-arrangements of the hydrological pathways and episodic
drainage from pro-glacial lakes largely controlled the isotopic composition of the lakes’ water (Colman et al. 1994;
Dettman et al. 1995; Forester et al. 1994; Lewis and
Anderson 1992; Rea et al. 1994). Although it is almost
impossible to extract information on d
18 O P from those
ostracod records, they are still excellent examples of successful and very useful reconstructions of relative d
18 O L
changes. Data for the isotopic composition of modern
ostracod valves have been reported for Lake Huron (Dettman et al. 1995). However, whilst these data suggested that
the most important taxa showed vital offsets, they were
insufficient for these offsets to be quantified.
Lister et al. (1991) presented an oxygen-isotope record
from Lake Qinghai (Qinghai-Tibetan Plateau) based on
measurements of Limnocythere inopinata and Eucypris
inflata, which alternately dominate the lake’s benthic ostracod assemblage throughout the past 15,000 years. The
record shows an overall increase of 6‰ from 8000
14 C-years
BP to 3000
14 C-years BP, which the authors attribute to the
slow accumulative evaporative concentration following a
major reduction in humidity in the region. This hypothesis is
strengthened by the fact that the reconstructed
oxygen-isotope values of the lake water, prevailing for the
last 3000 years, are close to the endpoint of isotopic
enrichment under modern conditions. Short term excursions
from this trend and a substantial variability before 8000
14 C-years BP are interpreted as episodic changes in the
lake’s water balance and water level variations. However, it
cannot be excluded that shifts of
18 O P and/or d
18 O A (which
are documented in the d
18 O record from the Guliya ice cap
(Thompson et al. 1997) or changes of the bottom water
temperature (the lake today is only 23 m deep) might have
contributed to both the long-term shifts and to the
small-scale fluctuations of d
18 O L .
In Europe, early monospecific deep-lake records exist
from Lake Zürich (Lister 1988) and Lake Lugano (Niessen
and Kelts 1989), both have a strong glacial to interglacial
shift but lack resolution of abrupt events during the transitions. Two moderately better-resolved d
18 O L histories of two
neighbouring lakes in the northern alpine foreland
(Ammersee and Starnberger See, southern Germany) (von
Grafenstein et al. 1992) provided evidence of climateinduced changes of d
18 O P consistent with the pollen-inferred
local climate history, including a strong negative excursion
during the Younger Dryas. They also show systematic and
constant offsets between the d
18 O values of different taxa
from the same sediment layer, indicative of physiologically
controlled fractionation in addition to temperature-dependent
fractionation. d
18 O records of monospecific ostracod samples from a deep-lake core from Lac Neuchâtel (Switzerland), depicted similar millennial-scale, late-glacial
variations, in addition to sudden changes in the lake’s water
balance and shifts of the mean isotopic composition of the
input, due to the episodic connection to the Aare river system (Schwalb et al. 1994). Shallow-water, late-glacial
records from the Ammersee (von Grafenstein et al. 1994),
from southern Sweden (Hammarlund et al. 1999), and
Switzerland (von Grafenstein et al. 2000, 2013) give evidence that the large shifts of d
18 O, bracketing the Younger
Dryas cold period, were accompanied by relative changes in
summer water temperatures, consistent with air-temperature
controlled shifts of d
18 O P . Quantitative reconstruction of
d
18 O P from those records remains biased by the temperature
effects, by seasonal variation of shallow water d
18 O, and
often by unknown changes in the lakes’ water balances. The
best-resolved European oxygen-isotope record from
deep-lake ostracod valves is from Ammersee (von Grafenstein et al. 1996, 1998, 1999a, b), and the accompanying
hydrological and isotope-geochemical calibration (von
Grafenstein et al. 1999a, b) will be used below as an
example to discuss the possible effects in more detail.
180
U. von Grafenstein and I. Labuhn
hydrological processes controlling the present and past links
between d
18 O L and d
18 O P, and (2) the effects related to the
valve formation (temperature-dependent fractionation and
vital effects). Most of the data used to illustrate those processes are from lakes situated within a small region of
southern Germany and are the author’s published or
unpublished material. The data was collected to support and
refine the quantitative interpretation of the d
18 O records from
sub-recent and late Glacial to Holocene mainly from one of
those lakes (Ammersee), which is presented in the fourth
part of this chapter. The reason for this regional concentration is the lack of case studies as comprehensive from other
regions, combining investigation of the modern isotope
hydrology, the physical limnology, and the ostracod geochemistry within the settings of a fossil record. The last part
of the chapter aims to show how d
18 O P reconstruction from
deep lake ostracods could be further developed and exploited to address secondary effects in more complex archives.
This chapter is an update of a previously published book
section (von Grafenstein 2002). It incorporates major
advances concerning our understanding of the oxygen isotope signal preserved in ostracod valves and gives an overview of new and upcoming records in Europe.
Existing Deep-Lake Oxygen-Isotope Records
The first published ostracod stable isotope record was from
Lake Erie (Fritz et al. 1975). This showed a 4‰ shift at the
late Wisconsin to Holocene transition, which was interpreted
as a temperature controlled change in d
18 O P . Later,
deep-lake oxygen-isotope ostracod records from the Great
Lakes demonstrated that the Late Wisconsin and Holocene
re-arrangements of the hydrological pathways and episodic
drainage from pro-glacial lakes largely controlled the isotopic composition of the lakes’ water (Colman et al. 1994;
Dettman et al. 1995; Forester et al. 1994; Lewis and
Anderson 1992; Rea et al. 1994). Although it is almost
impossible to extract information on d
18 O P from those
ostracod records, they are still excellent examples of successful and very useful reconstructions of relative d
18 O L
changes. Data for the isotopic composition of modern
ostracod valves have been reported for Lake Huron (Dettman et al. 1995). However, whilst these data suggested that
the most important taxa showed vital offsets, they were
insufficient for these offsets to be quantified.
Lister et al. (1991) presented an oxygen-isotope record
from Lake Qinghai (Qinghai-Tibetan Plateau) based on
measurements of Limnocythere inopinata and Eucypris
inflata, which alternately dominate the lake’s benthic ostracod assemblage throughout the past 15,000 years. The
record shows an overall increase of 6‰ from 8000
14 C-years
BP to 3000
14 C-years BP, which the authors attribute to the
slow accumulative evaporative concentration following a
major reduction in humidity in the region. This hypothesis is
strengthened by the fact that the reconstructed
oxygen-isotope values of the lake water, prevailing for the
last 3000 years, are close to the endpoint of isotopic
enrichment under modern conditions. Short term excursions
from this trend and a substantial variability before 8000
14 C-years BP are interpreted as episodic changes in the
lake’s water balance and water level variations. However, it
cannot be excluded that shifts of
18 O P and/or d
18 O A (which
are documented in the d
18 O record from the Guliya ice cap
(Thompson et al. 1997) or changes of the bottom water
temperature (the lake today is only 23 m deep) might have
contributed to both the long-term shifts and to the
small-scale fluctuations of d
18 O L .
In Europe, early monospecific deep-lake records exist
from Lake Zürich (Lister 1988) and Lake Lugano (Niessen
and Kelts 1989), both have a strong glacial to interglacial
shift but lack resolution of abrupt events during the transitions. Two moderately better-resolved d
18 O L histories of two
neighbouring lakes in the northern alpine foreland
(Ammersee and Starnberger See, southern Germany) (von
Grafenstein et al. 1992) provided evidence of climateinduced changes of d
18 O P consistent with the pollen-inferred
local climate history, including a strong negative excursion
during the Younger Dryas. They also show systematic and
constant offsets between the d
18 O values of different taxa
from the same sediment layer, indicative of physiologically
controlled fractionation in addition to temperature-dependent
fractionation. d
18 O records of monospecific ostracod samples from a deep-lake core from Lac Neuchâtel (Switzerland), depicted similar millennial-scale, late-glacial
variations, in addition to sudden changes in the lake’s water
balance and shifts of the mean isotopic composition of the
input, due to the episodic connection to the Aare river system (Schwalb et al. 1994). Shallow-water, late-glacial
records from the Ammersee (von Grafenstein et al. 1994),
from southern Sweden (Hammarlund et al. 1999), and
Switzerland (von Grafenstein et al. 2000, 2013) give evidence that the large shifts of d
18 O, bracketing the Younger
Dryas cold period, were accompanied by relative changes in
summer water temperatures, consistent with air-temperature
controlled shifts of d
18 O P . Quantitative reconstruction of
d
18 O P from those records remains biased by the temperature
effects, by seasonal variation of shallow water d
18 O, and
often by unknown changes in the lakes’ water balances. The
best-resolved European oxygen-isotope record from
deep-lake ostracod valves is from Ammersee (von Grafenstein et al. 1996, 1998, 1999a, b), and the accompanying
hydrological and isotope-geochemical calibration (von
Grafenstein et al. 1999a, b) will be used below as an
example to discuss the possible effects in more detail.
180
U. von Grafenstein and I. Labuhn