Dating of peat by means of uranium series disequilibrium (230-Th/234-U, also known as UTD) with special emphasis on dating the early Weichselian interstadial and last interglacial peats in north western Europe, is the subject of this study. ...

Zie: Introduction

Heijnis, Hendrik,

Dating of peat by means of uranium series disequilibrium (230-Th/234-U, also known as UTD) with special emphasis on dating the early Weichselian interstadial and last interglacial peats in north western Europe, is the subject of this study. ... Zie: Introductio

Heijnis, Hendrik

Proceedings - University of Groningen

   University of GroningenUranium/thorium dating of late Pleistocene peat deposits in N.W. Europe.Heijnis, HendrikIMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:1992Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Heijnis, H. (1992). Uranium/thorium dating of late Pleistocene peat deposits in N.W. Europe. s.n.CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 03-06-2022CHAPTER 1INTRODUCTIONDating of peat by means of uranium series disequilibrium, (23\h/2vIJ, also known asUTD) with special emphasis on dating the early Weichselian interstadial and lastinterglacial peats in north western Europe, is the subject of this study.In principle it is possible to date peat up to 350 ka by UTD, which provides us with animportant extension of the 1aC timescale (with a range up to t 50.000 BP).The first applications of uranium series dating were to deep sea sediments. Joly(1908) observed higher Ra contents in deep sea sediments than in sediments of thecontinental shelf. He concluded that Ra was scavenged out from sea water by depositionof suspended matter. Later Piggot and Urry Q942) showed that the Ra excess wassupported by an excess of 23oTh. In the 1960's the cyclicity of interglacials and glacials,as predicted in the Milankovitch theory on the ryclicity of the ice ages, was recognisedin the 18O isotope record of deep sea cores. The chronology for this new record wasprovided by uranium series dating of fossil coral reefs in Barbados (Mesollela, 1969),New Guinea (Veeh, 1970) and direct dating of deep sea sediment.Cherdyntsev was the first who studied the possibilities of uranium series datingof terrestrial materials such as peat, speleothems and travertines. It was not until thepublication of his translated work in 1971 that his work received the attention of a largegroup of researchers throughout the world. The first results of peat dating were publishedin 1980 (Vogel & Kronfeld, 1980). Vogel's publication and more recently Kafri et al.(1983) and De Vernal et al. (1986) showed very straightforward dating of organics withsimple corrections for the presence of thorium at t=0 and an assumed closed-systembehaviour of the material to be dated. Van der Wijk (1986,1987 and 1988) studied thecorrections for detrital thorium in fossil peat samples in more detail, his work shows ingeneral a good agreement between radiocarbon ages and U/Th ages obtained for peatsamples from several sites in N.W.Europe. This is especially true if no corrections areapplied for the presence of detrital thorium.After van der Wijk had completed his studies a new project was funded by theietherlands Organisation for Scientific Research (NWO) section Earth Sciences{WON), grant number:757.357.0L1, entitled: U/Th dating of the Eemian interglacialr N.W.Europe and the correlation with the palaeotemperature curves deduced fromeep-sea cores. This study results in the present thesis. The number of potential sites isumerous. However, only a small fraction of the sites in N.W.Europe turned out to beateable by UTD. The main subject became the investigation of open-system behaviourlf peat iayers and the corrections for detrital thorium. This more thematic approach wasecessary since the first results were in obvious contradiction with geological and/oralaeoecological evidence. For some unknown reason all obtained (for detrital Thorrected) ages turned out to be too young. This problem was already noted by Vogeln 1980, but not recognised as such. He stated that:"the dates for the samples from Bavaria suggest that theRiss/Wrirmr Interglacial of the northern Alps should be correlatedwith the whole of Stage 5 of the oxygen isotope record preservedin the deep sea cores, and not with stage 5e as various authors havepropounded. It would seem to be a matter of urgency that thisproblem be investigated further by means of the new dating methodproposed here."lhe end of this interglacial was dated at 86 - 89 ka, which to our present knowledge isrbout 25.000 years too young. Van der Wijk also recognized this problem, but solved itry proving that the uncorrected ages can yield reliable UTD dates. However, his:omparison befween iaC and U/Th ages (van der Wijk et al, 1988) for example for thefervola site in Finland is now believed incorrect. The 14C ages for Tervola (Su-688:'8.000 +4100 -2400 and Su-689: 48.000 +3500 -2400 BP) are very close to the detectionimit and are in disagreement with the existing Thermoluminescence dates (Hiitt et al,'Open system behaviour is the free exchange of uranium between peat and ground water afterleposition.2 The Riss/Wiirm interglacial is the Bavarian equivalent of the Eemian interglacial in N.W.Europe. Seeable 1.1.a1982) for both the overlying and underlying deposits. Therefore, the U/Th ages have tobe older. The present study shows that the discrepanry between the obtained young agesand the expected older ages (van der Wijk et al., 1988) was due to the short leachingtime and isotope fractionation during the leaching procedure. As the spiking of samplestook place after the separation of the leachate and residue the fractionation i.e. thedepletion of 230Th could not be observed. A brief explanation and comparisons arepresented in chapter 4 of this thesis.The assumption that a peat layer behaves as a geochemical closed system wasstudied in detail. After the first results new sampling techniques were tested both in thefield and the laboratory. After the analyses of several sites in detail we were able toconstruct a suitability diagram for the U/Th dating of peat. This makes a decision onhow to sample, treat the material and evaluate the results much easier.By careful sampling and evaluation of the obtained ages for early Weichselian andlast interglacial peat samples, it was possible to construct a new chronology for the latePleistocene in North Western Europe. Correlations were made with other chronologiesand records.ON GI,ACIALS AND INTERGI"ACIALS: A SHORT INTRODUCTION.In his orbital theory on the causes of the alternating glacial (cold) periods andinterglacial (temperate, warm) periods, the Yugoslavian astronomer Milankovitchpredicted a cycliciry (Milankovitch,1941). His theory consists of three components thatchange the intensity of the seasons. The first, the tilt of the earths axis (between 21.5 and24.5o), has a periodicity of 42.000 years and intensifies the seasons in both hemispheres.The second is the eccentricity of the earth orbit (from a near circle to an eccentricellipse) with a periodicity of 100.000 years. The growing distance to the sun will intensifythe season in one hemisphere and modify the seasons in the other. The precession orwobble is the third component. The precession of the earths axis is caused by interactionby the first two and determines whether a summer falls near or at a far point in the orbitand has a cyclicity of 23.000 years. For a long time there was a lack of an independentrecord of ice-age timing to test the cyclicity as predicted by Milankovitch.Emiliani (1955) produced the first more or less complete record of thel30enekilp6 lnd€0erel0derdeSfdrupFig. 1.1. schematic diagram showing the conelation of the Last Interglaciat/Gtacialcycle in N.W.Europe (and its vegetational clwracteistics) (after Behre, 1989)and the generalized r8O deep sea record (after Martinson et al, l9B7).alternations of interglacials and glacials. He studied the isotope composition of single cellmarine organisms called foraminifera. It is now understood that the abundance ratiobetween the natural oxygen isotopes 180/160 in the carbonate shells of foraminifera isclosely related to the amount of water locked in glaciers and ice-sheets. As waterevaporates from the relatively warm low-latitude ocean and moves away from the source,its 18O returns preferentially to the oceans as precipitation. The snow that falls on thedistant high altitude glaciers and high latitude ice-sheets is therefore relatively clepletedin 18o and as these glaciers and ice-sheets grow the oceans become more and moreenriched in 18O. This higher 180/160 abundance in sea water propagates into carbonateshells of dead foraminifera later recovered from marine sediments. By analyzing drilledT4' l lABI-E l . l .  T'he SLrb-Division of the Late Qtraternary Biostrat igraphy in N.W.Europe'Netherlands Great Bri tain I re land Sweden Finland France N. Germany GreeceHolocenel Flandrian L,i t t letonian I{olocene Flolocene Holocene Holocene IloloceneWeichsel ian2 l)evensian Mid land ian Weichsel ian Weichsel ian Weichsel ian Weichsel ianOdderade3 Upton Warren JAmtlandlnterstadialcomplexPeriipohjolaSt. Germain II Odderade ElevtheroupolisBrrirup/Amersfoort3Chelford Aghnadarragh St. Germain I Brdrup DramaDoxatonEemianr Ipswichian Gor l i an  ? [,eveiinienri Tepsankumpu Eemian Eemian PangaionSaal ian 2Wolstonian Munsterian Saal ian Saal ian Saalian Saalian Neakaterinil) Interykrciuls, 2) Glaciuls, 3) Interstadiuls.cores from the sea-floor, Emiliani found that the isotope ratio rose and fell according tothe cycles predicted by the Milankovitch theory. This new deep-sea chronology is dividedin odd and even "isotope stages". The warm interglacial stages have odd numbers andrelatively low 180/160 ratios (see figure 1.1.). The cold glacial stages have even numbersand relatively high 180/160 ratios.(see figure 1.1.).In N.W.Europe the subdivision of the I-ast Interglacial/Glacial cycle has beenbased for a considerable period of time on the lithostratigraphical evidence of thepositions of end moraines (so-called morphostratigraphy). As all the ice-advances weredescribed locally, every region or country gave different names to the same interglacialsand glacials. In table 1.1 the most important used names of the Last Interglacial/Glacialcycle are given.During the last Glacial period N.W.Europe was partly covered by ice-sheets (seefigure 5.1.). Outside the area of glaciation a lot of organic deposits were preserved.Inside the area of the maximum Weichselian glaciation less organic deposits werepreserved due to glacial erosion. As deduced from its pollen and macrofossils theseorganic deposits indicate slightly cooler conditions than today for certain intervals withinthe last Glacial. These organic deposits are often sandwiched between full glacial orperiglacial sediments and indicate climatic amelioration within the last Glacial period.These temperate stages are called interstadials. A glacial period can thus be subdividedinto stadials (full glacial conditions) and interstadials (temperate conditions). The mostimportant interstadials of the N.W.European mainland are mentioned in figure 1.1.; theN. European and British equivalents are to be found in table 1.1.At some places complete records embracing several interglacial/glacial cycles aredocumented. The records are called fnng Terrestrial Records and are the terrestrialequivalents of the deep-sea cores. Important l-ong Terrestrial Records in Europe are theTenagi Philippon (Wijmstra,1969), Padul (Florschritz et al.,IgJl), La Grand Pile(Woillard,1975) and l-es Echets (de Beaulieu and Reille,1984). As site-to-site correlationsare often problematic, much of the correlations are based on the laC chronology (of thelast 50.000 years only) (Woillard and Mook,1982) and on the recently published paperson the biostratigraphy of the Last Glacial by Behre (1989) and the special issue on theLast Interglacial/Glacial cycle of Quaternary International (Schliichter and Rutter,1989).16

English

Uranium/thorium dating of late Pleistocene peat deposits in N.W. Europe.

University of Groningen Research Database

  
 University of Groningen
Uranium/thorium dating of late Pleistocene peat deposits in N.W. Europe.
Heijnis, Hendrik
IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from
it. Please check the document version below.
Document Version
Publisher's PDF, also known as Version of record
Publication date:
1992
Link to publication in University of Groningen/UMCG research database
Citation for published version (APA):
Heijnis, H. (1992). Uranium/thorium dating of late Pleistocene peat deposits in N.W. Europe. Groningen:
s.n.
Copyright
Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the
author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).
Take-down policy
If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately
and investigate your claim.
Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the
number of authors shown on this cover page is limited to 10 maximum.
Download date: 10-02-2018
CHAPTER 1
INTRODUCTION
Dating of peat by means of uranium series disequilibrium, (23\h/2vIJ, also known as
UTD) with special emphasis on dating the early Weichselian interstadial and last
interglacial peats in north western Europe, is the subject of this study.
In principle it is possible to date peat up to 350 ka by UTD, which provides us with an
important extension of the 1aC timescale (with a range up to t 50.000 BP).
The first applications of uranium series dating were to deep sea sediments. Joly
(1908) observed higher Ra contents in deep sea sediments than in sediments of the
continental shelf. He concluded that Ra was scavenged out from sea water by deposition
of suspended matter. Later Piggot and Urry Q942) showed that the Ra excess was
supported by an excess of 23oTh. In the 1960's the cyclicity of interglacials and glacials,
as predicted in the Milankovitch theory on the ryclicity of the ice ages, was recognised
in the 18O isotope record of deep sea cores. The chronology for this new record was
provided by uranium series dating of fossil coral reefs in Barbados (Mesollela, 1969),
New Guinea (Veeh, 1970) and direct dating of deep sea sediment.
Cherdyntsev was the first who studied the possibilities of uranium series dating
of terrestrial materials such as peat, speleothems and travertines. It was not until the
publication of his translated work in 1971 that his work received the attention of a large
group of researchers throughout the world. The first results of peat dating were published
in 1980 (Vogel & Kronfeld, 1980). Vogel's publication and more recently Kafri et al.
(1983) and De Vernal et al. (1986) showed very straightforward dating of organics with
simple corrections for the presence of thorium at t=0 and an assumed closed-system
behaviour of the material to be dated. Van der Wijk (1986,1987 and 1988) studied the
corrections for detrital thorium in fossil peat samples in more detail, his work shows in
general a good agreement between radiocarbon ages and U/Th ages obtained for peat
samples from several sites in N.W.Europe. This is especially true if no corrections are
applied for the presence of detrital thorium.
After van der Wijk had completed his studies a new project was funded by the
ietherlands Organisation for Scientific Research (NWO) section Earth Sciences
{WON), grant number:757.357.0L1, entitled: U/Th dating of the Eemian interglacial
r N.W.Europe and the correlation with the palaeotemperature curves deduced from
eep-sea cores. This study results in the present thesis. The number of potential sites is
umerous. However, only a small fraction of the sites in N.W.Europe turned out to be
ateable by UTD. The main subject became the investigation of open-system behaviourl
f peat iayers and the corrections for detrital thorium. This more thematic approach was
ecessary since the first results were in obvious contradiction with geological and/or
alaeoecological evidence. For some unknown reason all obtained (for detrital Th
orrected) ages turned out to be too young. This problem was already noted by Vogel
n 1980, but not recognised as such. He stated that:
"the dates for the samples from Bavaria suggest that the
Riss/Wrirmr Interglacial of the northern Alps should be correlated
with the whole of Stage 5 of the oxygen isotope record preserved
in the deep sea cores, and not with stage 5e as various authors have
propounded. It would seem to be a matter of urgency that this
problem be investigated further by means of the new dating method
proposed here."
lhe end of this interglacial was dated at 86 - 89 ka, which to our present knowledge is
rbout 25.000 years too young. Van der Wijk also recognized this problem, but solved it
ry proving that the uncorrected ages can yield reliable UTD dates. However, his
:omparison befween iaC and U/Th ages (van der Wijk et al, 1988) for example for the
fervola site in Finland is now believed incorrect. The 14C ages for Tervola (Su-688:
'8.000 +4100 -2400 and Su-689: 48.000 +3500 -2400 BP) are very close to the detection
imit and are in disagreement with the existing Thermoluminescence dates (Hiitt et al,
'Open system behaviour is the free exchange of uranium between peat and ground water after
leposition.
2 The Riss/Wiirm interglacial is the Bavarian equivalent of the Eemian interglacial in N.W.Europe. See
able 1.1.
a
1982) for both the overlying and underlying deposits. Therefore, the U/Th ages have to
be older. The present study shows that the discrepanry between the obtained young ages
and the expected older ages (van der Wijk et al., 1988) was due to the short leaching
time and isotope fractionation during the leaching procedure. As the spiking of samples
took place after the separation of the leachate and residue the fractionation i.e. the
depletion of 230Th could not be observed. A brief explanation and comparisons are
presented in chapter 4 of this thesis.
The assumption that a peat layer behaves as a geochemical closed system was
studied in detail. After the first results new sampling techniques were tested both in the
field and the laboratory. After the analyses of several sites in detail we were able to
construct a suitability diagram for the U/Th dating of peat. This makes a decision on
how to sample, treat the material and evaluate the results much easier.
By careful sampling and evaluation of the obtained ages for early Weichselian and
last interglacial peat samples, it was possible to construct a new chronology for the late
Pleistocene in North Western Europe. Correlations were made with other chronologies
and records.
ON GI,ACIALS AND INTERGI"ACIALS: A SHORT INTRODUCTION.
In his orbital theory on the causes of the alternating glacial (cold) periods and
interglacial (temperate, warm) periods, the Yugoslavian astronomer Milankovitch
predicted a cycliciry (Milankovitch,1941). His theory consists of three components that
change the intensity of the seasons. The first, the tilt of the earths axis (between 21.5 and
24.5o), has a periodicity of 42.000 years and intensifies the seasons in both hemispheres.
The second is the eccentricity of the earth orbit (from a near circle to an eccentric
ellipse) with a periodicity of 100.000 years. The growing distance to the sun will intensify
the season in one hemisphere and modify the seasons in the other. The precession or
wobble is the third component. The precession of the earths axis is caused by interaction
by the first two and determines whether a summer falls near or at a far point in the orbit
and has a cyclicity of 23.000 years. For a long time there was a lack of an independent
record of ice-age timing to test the cyclicity as predicted by Milankovitch.
Emiliani (1955) produced the first more or less complete record of the
l3
0enekilp
6 lnd€
0erel
0derde
Sfdrup
Fig. 1.1. schematic diagram showing the conelation of the Last Interglaciat/Gtacial
cycle in N.W.Europe (and its vegetational clwracteistics) (after Behre, 1989)
and the generalized r8O deep sea record (after Martinson et al, l9B7).
alternations of interglacials and glacials. He studied the isotope composition of single cell
marine organisms called foraminifera. It is now understood that the abundance ratio
between the natural oxygen isotopes 180/160 in the carbonate shells of foraminifera is
closely related to the amount of water locked in glaciers and ice-sheets. As water
evaporates from the relatively warm low-latitude ocean and moves away from the source,
its 18O returns preferentially to the oceans as precipitation. The snow that falls on the
distant high altitude glaciers and high latitude ice-sheets is therefore relatively clepleted
in 18o and as these glaciers and ice-sheets grow the oceans become more and more
enriched in 18O. This higher 180/160 abundance in sea water propagates into carbonate
shells of dead foraminifera later recovered from marine sediments. By analyzing drilled
T4
' l lABI-E l . l .  T'he SLrb-Division of the Late Qtraternary Biostrat igraphy in N.W.Europe'
Netherlands Great Bri tain I re land Sweden Finland France N. Germany Greece
Holocenel Flandrian L,i t t letonian I{olocene Flolocene Holocene Holocene Ilolocene
Weichsel ian2 l)evensian Mid land ian Weichsel ian Weichsel ian Weichsel ian Weichsel ian
Odderade3 Upton Warren JAmtland
lnterstadial
complex
Periipohjola
St. Germain II Odderade Elevtheroupolis
Brrirup/
Amersfoort3
Chelford Aghnadarragh St. Germain I Brdrup Drama
Doxaton
Eemianr Ipswichian Gor l i an  ? [,eveiinienri Tepsankumpu Eemian Eemian Pangaion
Saal ian 2Wolstonian Munsterian Saal ian Saal ian Saalian Saalian Neakaterini
l) Interykrciuls, 2) Glaciuls, 3) Interstadiuls.
cores from the sea-floor, Emiliani found that the isotope ratio rose and fell according to
the cycles predicted by the Milankovitch theory. This new deep-sea chronology is divided
in odd and even "isotope stages". The warm interglacial stages have odd numbers and
relatively low 180/160 ratios (see figure 1.1.). The cold glacial stages have even numbers
and relatively high 180/160 ratios.(see figure 1.1.).
In N.W.Europe the subdivision of the I-ast Interglacial/Glacial cycle has been
based for a considerable period of time on the lithostratigraphical evidence of the
positions of end moraines (so-called morphostratigraphy). As all the ice-advances were
described locally, every region or country gave different names to the same interglacials
and glacials. In table 1.1 the most important used names of the Last Interglacial/Glacial
cycle are given.
During the last Glacial period N.W.Europe was partly covered by ice-sheets (see
figure 5.1.). Outside the area of glaciation a lot of organic deposits were preserved.
Inside the area of the maximum Weichselian glaciation less organic deposits were
preserved due to glacial erosion. As deduced from its pollen and macrofossils these
organic deposits indicate slightly cooler conditions than today for certain intervals within
the last Glacial. These organic deposits are often sandwiched between full glacial or
periglacial sediments and indicate climatic amelioration within the last Glacial period.
These temperate stages are called interstadials. A glacial period can thus be subdivided
into stadials (full glacial conditions) and interstadials (temperate conditions). The most
important interstadials of the N.W.European mainland are mentioned in figure 1.1.; the
N. European and British equivalents are to be found in table 1.1.
At some places complete records embracing several interglacial/glacial cycles are
documented. The records are called fnng Terrestrial Records and are the terrestrial
equivalents of the deep-sea cores. Important l-ong Terrestrial Records in Europe are the
Tenagi Philippon (Wijmstra,1969), Padul (Florschritz et al.,IgJl), La Grand Pile
(Woillard,1975) and l-es Echets (de Beaulieu and Reille,1984). As site-to-site correlations
are often problematic, much of the correlations are based on the laC chronology (of the
last 50.000 years only) (Woillard and Mook,1982) and on the recently published papers
on the biostratigraphy of the Last Glacial by Behre (1989) and the special issue on the
Last Interglacial/Glacial cycle of Quaternary International (Schliichter and Rutter,1989).
16


ARTS repository - University of Groningen

   University of GroningenUranium/thorium dating of late Pleistocene peat deposits in N.W. Europe.Heijnis, HendrikIMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:1992Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Heijnis, H. (1992). Uranium/thorium dating of late Pleistocene peat deposits in N.W. Europe. s.n.CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 31-10-2023CHAPTER 1INTRODUCTIONDating of peat by means of uranium series disequilibrium, (23\h/2vIJ, also known asUTD) with special emphasis on dating the early Weichselian interstadial and lastinterglacial peats in north western Europe, is the subject of this study.In principle it is possible to date peat up to 350 ka by UTD, which provides us with animportant extension of the 1aC timescale (with a range up to t 50.000 BP).The first applications of uranium series dating were to deep sea sediments. Joly(1908) observed higher Ra contents in deep sea sediments than in sediments of thecontinental shelf. He concluded that Ra was scavenged out from sea water by depositionof suspended matter. Later Piggot and Urry Q942) showed that the Ra excess wassupported by an excess of 23oTh. In the 1960's the cyclicity of interglacials and glacials,as predicted in the Milankovitch theory on the ryclicity of the ice ages, was recognisedin the 18O isotope record of deep sea cores. The chronology for this new record wasprovided by uranium series dating of fossil coral reefs in Barbados (Mesollela, 1969),New Guinea (Veeh, 1970) and direct dating of deep sea sediment.Cherdyntsev was the first who studied the possibilities of uranium series datingof terrestrial materials such as peat, speleothems and travertines. It was not until thepublication of his translated work in 1971 that his work received the attention of a largegroup of researchers throughout the world. The first results of peat dating were publishedin 1980 (Vogel & Kronfeld, 1980). Vogel's publication and more recently Kafri et al.(1983) and De Vernal et al. (1986) showed very straightforward dating of organics withsimple corrections for the presence of thorium at t=0 and an assumed closed-systembehaviour of the material to be dated. Van der Wijk (1986,1987 and 1988) studied thecorrections for detrital thorium in fossil peat samples in more detail, his work shows ingeneral a good agreement between radiocarbon ages and U/Th ages obtained for peatsamples from several sites in N.W.Europe. This is especially true if no corrections areapplied for the presence of detrital thorium.After van der Wijk had completed his studies a new project was funded by theietherlands Organisation for Scientific Research (NWO) section Earth Sciences{WON), grant number:757.357.0L1, entitled: U/Th dating of the Eemian interglacialr N.W.Europe and the correlation with the palaeotemperature curves deduced fromeep-sea cores. This study results in the present thesis. The number of potential sites isumerous. However, only a small fraction of the sites in N.W.Europe turned out to beateable by UTD. The main subject became the investigation of open-system behaviourlf peat iayers and the corrections for detrital thorium. This more thematic approach wasecessary since the first results were in obvious contradiction with geological and/oralaeoecological evidence. For some unknown reason all obtained (for detrital Thorrected) ages turned out to be too young. This problem was already noted by Vogeln 1980, but not recognised as such. He stated that:"the dates for the samples from Bavaria suggest that theRiss/Wrirmr Interglacial of the northern Alps should be correlatedwith the whole of Stage 5 of the oxygen isotope record preservedin the deep sea cores, and not with stage 5e as various authors havepropounded. It would seem to be a matter of urgency that thisproblem be investigated further by means of the new dating methodproposed here."lhe end of this interglacial was dated at 86 - 89 ka, which to our present knowledge isrbout 25.000 years too young. Van der Wijk also recognized this problem, but solved itry proving that the uncorrected ages can yield reliable UTD dates. However, his:omparison befween iaC and U/Th ages (van der Wijk et al, 1988) for example for thefervola site in Finland is now believed incorrect. The 14C ages for Tervola (Su-688:'8.000 +4100 -2400 and Su-689: 48.000 +3500 -2400 BP) are very close to the detectionimit and are in disagreement with the existing Thermoluminescence dates (Hiitt et al,'Open system behaviour is the free exchange of uranium between peat and ground water afterleposition.2 The Riss/Wiirm interglacial is the Bavarian equivalent of the Eemian interglacial in N.W.Europe. Seeable 1.1.a1982) for both the overlying and underlying deposits. Therefore, the U/Th ages have tobe older. The present study shows that the discrepanry between the obtained young agesand the expected older ages (van der Wijk et al., 1988) was due to the short leachingtime and isotope fractionation during the leaching procedure. As the spiking of samplestook place after the separation of the leachate and residue the fractionation i.e. thedepletion of 230Th could not be observed. A brief explanation and comparisons arepresented in chapter 4 of this thesis.The assumption that a peat layer behaves as a geochemical closed system wasstudied in detail. After the first results new sampling techniques were tested both in thefield and the laboratory. After the analyses of several sites in detail we were able toconstruct a suitability diagram for the U/Th dating of peat. This makes a decision onhow to sample, treat the material and evaluate the results much easier.By careful sampling and evaluation of the obtained ages for early Weichselian andlast interglacial peat samples, it was possible to construct a new chronology for the latePleistocene in North Western Europe. Correlations were made with other chronologiesand records.ON GI,ACIALS AND INTERGI"ACIALS: A SHORT INTRODUCTION.In his orbital theory on the causes of the alternating glacial (cold) periods andinterglacial (temperate, warm) periods, the Yugoslavian astronomer Milankovitchpredicted a cycliciry (Milankovitch,1941). His theory consists of three components thatchange the intensity of the seasons. The first, the tilt of the earths axis (between 21.5 and24.5o), has a periodicity of 42.000 years and intensifies the seasons in both hemispheres.The second is the eccentricity of the earth orbit (from a near circle to an eccentricellipse) with a periodicity of 100.000 years. The growing distance to the sun will intensifythe season in one hemisphere and modify the seasons in the other. The precession orwobble is the third component. The precession of the earths axis is caused by interactionby the first two and determines whether a summer falls near or at a far point in the orbitand has a cyclicity of 23.000 years. For a long time there was a lack of an independentrecord of ice-age timing to test the cyclicity as predicted by Milankovitch.Emiliani (1955) produced the first more or less complete record of thel30enekilp6 lnd€0erel0derdeSfdrupFig. 1.1. schematic diagram showing the conelation of the Last Interglaciat/Gtacialcycle in N.W.Europe (and its vegetational clwracteistics) (after Behre, 1989)and the generalized r8O deep sea record (after Martinson et al, l9B7).alternations of interglacials and glacials. He studied the isotope composition of single cellmarine organisms called foraminifera. It is now understood that the abundance ratiobetween the natural oxygen isotopes 180/160 in the carbonate shells of foraminifera isclosely related to the amount of water locked in glaciers and ice-sheets. As waterevaporates from the relatively warm low-latitude ocean and moves away from the source,its 18O returns preferentially to the oceans as precipitation. The snow that falls on thedistant high altitude glaciers and high latitude ice-sheets is therefore relatively clepletedin 18o and as these glaciers and ice-sheets grow the oceans become more and moreenriched in 18O. This higher 180/160 abundance in sea water propagates into carbonateshells of dead foraminifera later recovered from marine sediments. By analyzing drilledT4' l lABI-E l . l .  T'he SLrb-Division of the Late Qtraternary Biostrat igraphy in N.W.Europe'Netherlands Great Bri tain I re land Sweden Finland France N. Germany GreeceHolocenel Flandrian L,i t t letonian I{olocene Flolocene Holocene Holocene IloloceneWeichsel ian2 l)evensian Mid land ian Weichsel ian Weichsel ian Weichsel ian Weichsel ianOdderade3 Upton Warren JAmtlandlnterstadialcomplexPeriipohjolaSt. Germain II Odderade ElevtheroupolisBrrirup/Amersfoort3Chelford Aghnadarragh St. Germain I Brdrup DramaDoxatonEemianr Ipswichian Gor l i an  ? [,eveiinienri Tepsankumpu Eemian Eemian PangaionSaal ian 2Wolstonian Munsterian Saal ian Saal ian Saalian Saalian Neakaterinil) Interykrciuls, 2) Glaciuls, 3) Interstadiuls.cores from the sea-floor, Emiliani found that the isotope ratio rose and fell according tothe cycles predicted by the Milankovitch theory. This new deep-sea chronology is dividedin odd and even "isotope stages". The warm interglacial stages have odd numbers andrelatively low 180/160 ratios (see figure 1.1.). The cold glacial stages have even numbersand relatively high 180/160 ratios.(see figure 1.1.).In N.W.Europe the subdivision of the I-ast Interglacial/Glacial cycle has beenbased for a considerable period of time on the lithostratigraphical evidence of thepositions of end moraines (so-called morphostratigraphy). As all the ice-advances weredescribed locally, every region or country gave different names to the same interglacialsand glacials. In table 1.1 the most important used names of the Last Interglacial/Glacialcycle are given.During the last Glacial period N.W.Europe was partly covered by ice-sheets (seefigure 5.1.). Outside the area of glaciation a lot of organic deposits were preserved.Inside the area of the maximum Weichselian glaciation less organic deposits werepreserved due to glacial erosion. As deduced from its pollen and macrofossils theseorganic deposits indicate slightly cooler conditions than today for certain intervals withinthe last Glacial. These organic deposits are often sandwiched between full glacial orperiglacial sediments and indicate climatic amelioration within the last Glacial period.These temperate stages are called interstadials. A glacial period can thus be subdividedinto stadials (full glacial conditions) and interstadials (temperate conditions). The mostimportant interstadials of the N.W.European mainland are mentioned in figure 1.1.; theN. European and British equivalents are to be found in table 1.1.At some places complete records embracing several interglacial/glacial cycles aredocumented. The records are called fnng Terrestrial Records and are the terrestrialequivalents of the deep-sea cores. Important l-ong Terrestrial Records in Europe are theTenagi Philippon (Wijmstra,1969), Padul (Florschritz et al.,IgJl), La Grand Pile(Woillard,1975) and l-es Echets (de Beaulieu and Reille,1984). As site-to-site correlationsare often problematic, much of the correlations are based on the laC chronology (of thelast 50.000 years only) (Woillard and Mook,1982) and on the recently published paperson the biostratigraphy of the Last Glacial by Behre (1989) and the special issue on theLast Interglacial/Glacial cycle of Quaternary International (Schliichter and Rutter,1989).16

   University of GroningenUranium/thorium dating of late Pleistocene peat deposits in N.W. Europe.Heijnis, HendrikIMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:1992Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Heijnis, H. (1992). Uranium/thorium dating of late Pleistocene peat deposits in N.W. Europe. s.n.CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 06-06-2022CHAPTER 1INTRODUCTIONDating of peat by means of uranium series disequilibrium, (23\h/2vIJ, also known asUTD) with special emphasis on dating the early Weichselian interstadial and lastinterglacial peats in north western Europe, is the subject of this study.In principle it is possible to date peat up to 350 ka by UTD, which provides us with animportant extension of the 1aC timescale (with a range up to t 50.000 BP).The first applications of uranium series dating were to deep sea sediments. Joly(1908) observed higher Ra contents in deep sea sediments than in sediments of thecontinental shelf. He concluded that Ra was scavenged out from sea water by depositionof suspended matter. Later Piggot and Urry Q942) showed that the Ra excess wassupported by an excess of 23oTh. In the 1960's the cyclicity of interglacials and glacials,as predicted in the Milankovitch theory on the ryclicity of the ice ages, was recognisedin the 18O isotope record of deep sea cores. The chronology for this new record wasprovided by uranium series dating of fossil coral reefs in Barbados (Mesollela, 1969),New Guinea (Veeh, 1970) and direct dating of deep sea sediment.Cherdyntsev was the first who studied the possibilities of uranium series datingof terrestrial materials such as peat, speleothems and travertines. It was not until thepublication of his translated work in 1971 that his work received the attention of a largegroup of researchers throughout the world. The first results of peat dating were publishedin 1980 (Vogel & Kronfeld, 1980). Vogel's publication and more recently Kafri et al.(1983) and De Vernal et al. (1986) showed very straightforward dating of organics withsimple corrections for the presence of thorium at t=0 and an assumed closed-systembehaviour of the material to be dated. Van der Wijk (1986,1987 and 1988) studied thecorrections for detrital thorium in fossil peat samples in more detail, his work shows ingeneral a good agreement between radiocarbon ages and U/Th ages obtained for peatsamples from several sites in N.W.Europe. This is especially true if no corrections areapplied for the presence of detrital thorium.After van der Wijk had completed his studies a new project was funded by theietherlands Organisation for Scientific Research (NWO) section Earth Sciences{WON), grant number:757.357.0L1, entitled: U/Th dating of the Eemian interglacialr N.W.Europe and the correlation with the palaeotemperature curves deduced fromeep-sea cores. This study results in the present thesis. The number of potential sites isumerous. However, only a small fraction of the sites in N.W.Europe turned out to beateable by UTD. The main subject became the investigation of open-system behaviourlf peat iayers and the corrections for detrital thorium. This more thematic approach wasecessary since the first results were in obvious contradiction with geological and/oralaeoecological evidence. For some unknown reason all obtained (for detrital Thorrected) ages turned out to be too young. This problem was already noted by Vogeln 1980, but not recognised as such. He stated that:"the dates for the samples from Bavaria suggest that theRiss/Wrirmr Interglacial of the northern Alps should be correlatedwith the whole of Stage 5 of the oxygen isotope record preservedin the deep sea cores, and not with stage 5e as various authors havepropounded. It would seem to be a matter of urgency that thisproblem be investigated further by means of the new dating methodproposed here."lhe end of this interglacial was dated at 86 - 89 ka, which to our present knowledge isrbout 25.000 years too young. Van der Wijk also recognized this problem, but solved itry proving that the uncorrected ages can yield reliable UTD dates. However, his:omparison befween iaC and U/Th ages (van der Wijk et al, 1988) for example for thefervola site in Finland is now believed incorrect. The 14C ages for Tervola (Su-688:'8.000 +4100 -2400 and Su-689: 48.000 +3500 -2400 BP) are very close to the detectionimit and are in disagreement with the existing Thermoluminescence dates (Hiitt et al,'Open system behaviour is the free exchange of uranium between peat and ground water afterleposition.2 The Riss/Wiirm interglacial is the Bavarian equivalent of the Eemian interglacial in N.W.Europe. Seeable 1.1.a1982) for both the overlying and underlying deposits. Therefore, the U/Th ages have tobe older. The present study shows that the discrepanry between the obtained young agesand the expected older ages (van der Wijk et al., 1988) was due to the short leachingtime and isotope fractionation during the leaching procedure. As the spiking of samplestook place after the separation of the leachate and residue the fractionation i.e. thedepletion of 230Th could not be observed. A brief explanation and comparisons arepresented in chapter 4 of this thesis.The assumption that a peat layer behaves as a geochemical closed system wasstudied in detail. After the first results new sampling techniques were tested both in thefield and the laboratory. After the analyses of several sites in detail we were able toconstruct a suitability diagram for the U/Th dating of peat. This makes a decision onhow to sample, treat the material and evaluate the results much easier.By careful sampling and evaluation of the obtained ages for early Weichselian andlast interglacial peat samples, it was possible to construct a new chronology for the latePleistocene in North Western Europe. Correlations were made with other chronologiesand records.ON GI,ACIALS AND INTERGI"ACIALS: A SHORT INTRODUCTION.In his orbital theory on the causes of the alternating glacial (cold) periods andinterglacial (temperate, warm) periods, the Yugoslavian astronomer Milankovitchpredicted a cycliciry (Milankovitch,1941). His theory consists of three components thatchange the intensity of the seasons. The first, the tilt of the earths axis (between 21.5 and24.5o), has a periodicity of 42.000 years and intensifies the seasons in both hemispheres.The second is the eccentricity of the earth orbit (from a near circle to an eccentricellipse) with a periodicity of 100.000 years. The growing distance to the sun will intensifythe season in one hemisphere and modify the seasons in the other. The precession orwobble is the third component. The precession of the earths axis is caused by interactionby the first two and determines whether a summer falls near or at a far point in the orbitand has a cyclicity of 23.000 years. For a long time there was a lack of an independentrecord of ice-age timing to test the cyclicity as predicted by Milankovitch.Emiliani (1955) produced the first more or less complete record of thel30enekilp6 lnd€0erel0derdeSfdrupFig. 1.1. schematic diagram showing the conelation of the Last Interglaciat/Gtacialcycle in N.W.Europe (and its vegetational clwracteistics) (after Behre, 1989)and the generalized r8O deep sea record (after Martinson et al, l9B7).alternations of interglacials and glacials. He studied the isotope composition of single cellmarine organisms called foraminifera. It is now understood that the abundance ratiobetween the natural oxygen isotopes 180/160 in the carbonate shells of foraminifera isclosely related to the amount of water locked in glaciers and ice-sheets. As waterevaporates from the relatively warm low-latitude ocean and moves away from the source,its 18O returns preferentially to the oceans as precipitation. The snow that falls on thedistant high altitude glaciers and high latitude ice-sheets is therefore relatively clepletedin 18o and as these glaciers and ice-sheets grow the oceans become more and moreenriched in 18O. This higher 180/160 abundance in sea water propagates into carbonateshells of dead foraminifera later recovered from marine sediments. By analyzing drilledT4' l lABI-E l . l .  T'he SLrb-Division of the Late Qtraternary Biostrat igraphy in N.W.Europe'Netherlands Great Bri tain I re land Sweden Finland France N. Germany GreeceHolocenel Flandrian L,i t t letonian I{olocene Flolocene Holocene Holocene IloloceneWeichsel ian2 l)evensian Mid land ian Weichsel ian Weichsel ian Weichsel ian Weichsel ianOdderade3 Upton Warren JAmtlandlnterstadialcomplexPeriipohjolaSt. Germain II Odderade ElevtheroupolisBrrirup/Amersfoort3Chelford Aghnadarragh St. Germain I Brdrup DramaDoxatonEemianr Ipswichian Gor l i an  ? [,eveiinienri Tepsankumpu Eemian Eemian PangaionSaal ian 2Wolstonian Munsterian Saal ian Saal ian Saalian Saalian Neakaterinil) Interykrciuls, 2) Glaciuls, 3) Interstadiuls.cores from the sea-floor, Emiliani found that the isotope ratio rose and fell according tothe cycles predicted by the Milankovitch theory. This new deep-sea chronology is dividedin odd and even "isotope stages". The warm interglacial stages have odd numbers andrelatively low 180/160 ratios (see figure 1.1.). The cold glacial stages have even numbersand relatively high 180/160 ratios.(see figure 1.1.).In N.W.Europe the subdivision of the I-ast Interglacial/Glacial cycle has beenbased for a considerable period of time on the lithostratigraphical evidence of thepositions of end moraines (so-called morphostratigraphy). As all the ice-advances weredescribed locally, every region or country gave different names to the same interglacialsand glacials. In table 1.1 the most important used names of the Last Interglacial/Glacialcycle are given.During the last Glacial period N.W.Europe was partly covered by ice-sheets (seefigure 5.1.). Outside the area of glaciation a lot of organic deposits were preserved.Inside the area of the maximum Weichselian glaciation less organic deposits werepreserved due to glacial erosion. As deduced from its pollen and macrofossils theseorganic deposits indicate slightly cooler conditions than today for certain intervals withinthe last Glacial. These organic deposits are often sandwiched between full glacial orperiglacial sediments and indicate climatic amelioration within the last Glacial period.These temperate stages are called interstadials. A glacial period can thus be subdividedinto stadials (full glacial conditions) and interstadials (temperate conditions). The mostimportant interstadials of the N.W.European mainland are mentioned in figure 1.1.; theN. European and British equivalents are to be found in table 1.1.At some places complete records embracing several interglacial/glacial cycles aredocumented. The records are called fnng Terrestrial Records and are the terrestrialequivalents of the deep-sea cores. Important l-ong Terrestrial Records in Europe are theTenagi Philippon (Wijmstra,1969), Padul (Florschritz et al.,IgJl), La Grand Pile(Woillard,1975) and l-es Echets (de Beaulieu and Reille,1984). As site-to-site correlationsare often problematic, much of the correlations are based on the laC chronology (of thelast 50.000 years only) (Woillard and Mook,1982) and on the recently published paperson the biostratigraphy of the Last Glacial by Behre (1989) and the special issue on theLast Interglacial/Glacial cycle of Quaternary International (Schliichter and Rutter,1989).16

University of Groningen

   University of GroningenUranium/thorium dating of late Pleistocene peat deposits in N.W. Europe.Heijnis, HendrikIMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:1992Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Heijnis, H. (1992). Uranium/thorium dating of late Pleistocene peat deposits in N.W. Europe. Groningen:s.n.CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 12-11-2019CHAPTER 1INTRODUCTIONDating of peat by means of uranium series disequilibrium, (23\h/2vIJ, also known asUTD) with special emphasis on dating the early Weichselian interstadial and lastinterglacial peats in north western Europe, is the subject of this study.In principle it is possible to date peat up to 350 ka by UTD, which provides us with animportant extension of the 1aC timescale (with a range up to t 50.000 BP).The first applications of uranium series dating were to deep sea sediments. Joly(1908) observed higher Ra contents in deep sea sediments than in sediments of thecontinental shelf. He concluded that Ra was scavenged out from sea water by depositionof suspended matter. Later Piggot and Urry Q942) showed that the Ra excess wassupported by an excess of 23oTh. In the 1960's the cyclicity of interglacials and glacials,as predicted in the Milankovitch theory on the ryclicity of the ice ages, was recognisedin the 18O isotope record of deep sea cores. The chronology for this new record wasprovided by uranium series dating of fossil coral reefs in Barbados (Mesollela, 1969),New Guinea (Veeh, 1970) and direct dating of deep sea sediment.Cherdyntsev was the first who studied the possibilities of uranium series datingof terrestrial materials such as peat, speleothems and travertines. It was not until thepublication of his translated work in 1971 that his work received the attention of a largegroup of researchers throughout the world. The first results of peat dating were publishedin 1980 (Vogel & Kronfeld, 1980). Vogel's publication and more recently Kafri et al.(1983) and De Vernal et al. (1986) showed very straightforward dating of organics withsimple corrections for the presence of thorium at t=0 and an assumed closed-systembehaviour of the material to be dated. Van der Wijk (1986,1987 and 1988) studied thecorrections for detrital thorium in fossil peat samples in more detail, his work shows ingeneral a good agreement between radiocarbon ages and U/Th ages obtained for peatsamples from several sites in N.W.Europe. This is especially true if no corrections areapplied for the presence of detrital thorium.After van der Wijk had completed his studies a new project was funded by theietherlands Organisation for Scientific Research (NWO) section Earth Sciences{WON), grant number:757.357.0L1, entitled: U/Th dating of the Eemian interglacialr N.W.Europe and the correlation with the palaeotemperature curves deduced fromeep-sea cores. This study results in the present thesis. The number of potential sites isumerous. However, only a small fraction of the sites in N.W.Europe turned out to beateable by UTD. The main subject became the investigation of open-system behaviourlf peat iayers and the corrections for detrital thorium. This more thematic approach wasecessary since the first results were in obvious contradiction with geological and/oralaeoecological evidence. For some unknown reason all obtained (for detrital Thorrected) ages turned out to be too young. This problem was already noted by Vogeln 1980, but not recognised as such. He stated that:"the dates for the samples from Bavaria suggest that theRiss/Wrirmr Interglacial of the northern Alps should be correlatedwith the whole of Stage 5 of the oxygen isotope record preservedin the deep sea cores, and not with stage 5e as various authors havepropounded. It would seem to be a matter of urgency that thisproblem be investigated further by means of the new dating methodproposed here."lhe end of this interglacial was dated at 86 - 89 ka, which to our present knowledge isrbout 25.000 years too young. Van der Wijk also recognized this problem, but solved itry proving that the uncorrected ages can yield reliable UTD dates. However, his:omparison befween iaC and U/Th ages (van der Wijk et al, 1988) for example for thefervola site in Finland is now believed incorrect. The 14C ages for Tervola (Su-688:'8.000 +4100 -2400 and Su-689: 48.000 +3500 -2400 BP) are very close to the detectionimit and are in disagreement with the existing Thermoluminescence dates (Hiitt et al,'Open system behaviour is the free exchange of uranium between peat and ground water afterleposition.2 The Riss/Wiirm interglacial is the Bavarian equivalent of the Eemian interglacial in N.W.Europe. Seeable 1.1.a1982) for both the overlying and underlying deposits. Therefore, the U/Th ages have tobe older. The present study shows that the discrepanry between the obtained young agesand the expected older ages (van der Wijk et al., 1988) was due to the short leachingtime and isotope fractionation during the leaching procedure. As the spiking of samplestook place after the separation of the leachate and residue the fractionation i.e. thedepletion of 230Th could not be observed. A brief explanation and comparisons arepresented in chapter 4 of this thesis.The assumption that a peat layer behaves as a geochemical closed system wasstudied in detail. After the first results new sampling techniques were tested both in thefield and the laboratory. After the analyses of several sites in detail we were able toconstruct a suitability diagram for the U/Th dating of peat. This makes a decision onhow to sample, treat the material and evaluate the results much easier.By careful sampling and evaluation of the obtained ages for early Weichselian andlast interglacial peat samples, it was possible to construct a new chronology for the latePleistocene in North Western Europe. Correlations were made with other chronologiesand records.ON GI,ACIALS AND INTERGI"ACIALS: A SHORT INTRODUCTION.In his orbital theory on the causes of the alternating glacial (cold) periods andinterglacial (temperate, warm) periods, the Yugoslavian astronomer Milankovitchpredicted a cycliciry (Milankovitch,1941). His theory consists of three components thatchange the intensity of the seasons. The first, the tilt of the earths axis (between 21.5 and24.5o), has a periodicity of 42.000 years and intensifies the seasons in both hemispheres.The second is the eccentricity of the earth orbit (from a near circle to an eccentricellipse) with a periodicity of 100.000 years. The growing distance to the sun will intensifythe season in one hemisphere and modify the seasons in the other. The precession orwobble is the third component. The precession of the earths axis is caused by interactionby the first two and determines whether a summer falls near or at a far point in the orbitand has a cyclicity of 23.000 years. For a long time there was a lack of an independentrecord of ice-age timing to test the cyclicity as predicted by Milankovitch.Emiliani (1955) produced the first more or less complete record of thel30enekilp6 lnd€0erel0derdeSfdrupFig. 1.1. schematic diagram showing the conelation of the Last Interglaciat/Gtacialcycle in N.W.Europe (and its vegetational clwracteistics) (after Behre, 1989)and the generalized r8O deep sea record (after Martinson et al, l9B7).alternations of interglacials and glacials. He studied the isotope composition of single cellmarine organisms called foraminifera. It is now understood that the abundance ratiobetween the natural oxygen isotopes 180/160 in the carbonate shells of foraminifera isclosely related to the amount of water locked in glaciers and ice-sheets. As waterevaporates from the relatively warm low-latitude ocean and moves away from the source,its 18O returns preferentially to the oceans as precipitation. The snow that falls on thedistant high altitude glaciers and high latitude ice-sheets is therefore relatively clepletedin 18o and as these glaciers and ice-sheets grow the oceans become more and moreenriched in 18O. This higher 180/160 abundance in sea water propagates into carbonateshells of dead foraminifera later recovered from marine sediments. By analyzing drilledT4' l lABI-E l . l .  T'he SLrb-Division of the Late Qtraternary Biostrat igraphy in N.W.Europe'Netherlands Great Bri tain I re land Sweden Finland France N. Germany GreeceHolocenel Flandrian L,i t t letonian I{olocene Flolocene Holocene Holocene IloloceneWeichsel ian2 l)evensian Mid land ian Weichsel ian Weichsel ian Weichsel ian Weichsel ianOdderade3 Upton Warren JAmtlandlnterstadialcomplexPeriipohjolaSt. Germain II Odderade ElevtheroupolisBrrirup/Amersfoort3Chelford Aghnadarragh St. Germain I Brdrup DramaDoxatonEemianr Ipswichian Gor l i an  ? [,eveiinienri Tepsankumpu Eemian Eemian PangaionSaal ian 2Wolstonian Munsterian Saal ian Saal ian Saalian Saalian Neakaterinil) Interykrciuls, 2) Glaciuls, 3) Interstadiuls.cores from the sea-floor, Emiliani found that the isotope ratio rose and fell according tothe cycles predicted by the Milankovitch theory. This new deep-sea chronology is dividedin odd and even "isotope stages". The warm interglacial stages have odd numbers andrelatively low 180/160 ratios (see figure 1.1.). The cold glacial stages have even numbersand relatively high 180/160 ratios.(see figure 1.1.).In N.W.Europe the subdivision of the I-ast Interglacial/Glacial cycle has beenbased for a considerable period of time on the lithostratigraphical evidence of thepositions of end moraines (so-called morphostratigraphy). As all the ice-advances weredescribed locally, every region or country gave different names to the same interglacialsand glacials. In table 1.1 the most important used names of the Last Interglacial/Glacialcycle are given.During the last Glacial period N.W.Europe was partly covered by ice-sheets (seefigure 5.1.). Outside the area of glaciation a lot of organic deposits were preserved.Inside the area of the maximum Weichselian glaciation less organic deposits werepreserved due to glacial erosion. As deduced from its pollen and macrofossils theseorganic deposits indicate slightly cooler conditions than today for certain intervals withinthe last Glacial. These organic deposits are often sandwiched between full glacial orperiglacial sediments and indicate climatic amelioration within the last Glacial period.These temperate stages are called interstadials. A glacial period can thus be subdividedinto stadials (full glacial conditions) and interstadials (temperate conditions). The mostimportant interstadials of the N.W.European mainland are mentioned in figure 1.1.; theN. European and British equivalents are to be found in table 1.1.At some places complete records embracing several interglacial/glacial cycles aredocumented. The records are called fnng Terrestrial Records and are the terrestrialequivalents of the deep-sea cores. Important l-ong Terrestrial Records in Europe are theTenagi Philippon (Wijmstra,1969), Padul (Florschritz et al.,IgJl), La Grand Pile(Woillard,1975) and l-es Echets (de Beaulieu and Reille,1984). As site-to-site correlationsare often problematic, much of the correlations are based on the laC chronology (of thelast 50.000 years only) (Woillard and Mook,1982) and on the recently published paperson the biostratigraphy of the Last Glacial by Behre (1989) and the special issue on theLast Interglacial/Glacial cycle of Quaternary International (Schliichter and Rutter,1989).16

Dissertations of the University of Groningen

   University of GroningenUranium/thorium dating of late Pleistocene peat deposits in N.W. Europe.Heijnis, HendrikIMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:1992Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Heijnis, H. (1992). Uranium/thorium dating of late Pleistocene peat deposits in N.W. Europe. s.n.CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 04-06-2022CHAPTER 1INTRODUCTIONDating of peat by means of uranium series disequilibrium, (23\h/2vIJ, also known asUTD) with special emphasis on dating the early Weichselian interstadial and lastinterglacial peats in north western Europe, is the subject of this study.In principle it is possible to date peat up to 350 ka by UTD, which provides us with animportant extension of the 1aC timescale (with a range up to t 50.000 BP).The first applications of uranium series dating were to deep sea sediments. Joly(1908) observed higher Ra contents in deep sea sediments than in sediments of thecontinental shelf. He concluded that Ra was scavenged out from sea water by depositionof suspended matter. Later Piggot and Urry Q942) showed that the Ra excess wassupported by an excess of 23oTh. In the 1960's the cyclicity of interglacials and glacials,as predicted in the Milankovitch theory on the ryclicity of the ice ages, was recognisedin the 18O isotope record of deep sea cores. The chronology for this new record wasprovided by uranium series dating of fossil coral reefs in Barbados (Mesollela, 1969),New Guinea (Veeh, 1970) and direct dating of deep sea sediment.Cherdyntsev was the first who studied the possibilities of uranium series datingof terrestrial materials such as peat, speleothems and travertines. It was not until thepublication of his translated work in 1971 that his work received the attention of a largegroup of researchers throughout the world. The first results of peat dating were publishedin 1980 (Vogel & Kronfeld, 1980). Vogel's publication and more recently Kafri et al.(1983) and De Vernal et al. (1986) showed very straightforward dating of organics withsimple corrections for the presence of thorium at t=0 and an assumed closed-systembehaviour of the material to be dated. Van der Wijk (1986,1987 and 1988) studied thecorrections for detrital thorium in fossil peat samples in more detail, his work shows ingeneral a good agreement between radiocarbon ages and U/Th ages obtained for peatsamples from several sites in N.W.Europe. This is especially true if no corrections areapplied for the presence of detrital thorium.After van der Wijk had completed his studies a new project was funded by theietherlands Organisation for Scientific Research (NWO) section Earth Sciences{WON), grant number:757.357.0L1, entitled: U/Th dating of the Eemian interglacialr N.W.Europe and the correlation with the palaeotemperature curves deduced fromeep-sea cores. This study results in the present thesis. The number of potential sites isumerous. However, only a small fraction of the sites in N.W.Europe turned out to beateable by UTD. The main subject became the investigation of open-system behaviourlf peat iayers and the corrections for detrital thorium. This more thematic approach wasecessary since the first results were in obvious contradiction with geological and/oralaeoecological evidence. For some unknown reason all obtained (for detrital Thorrected) ages turned out to be too young. This problem was already noted by Vogeln 1980, but not recognised as such. He stated that:"the dates for the samples from Bavaria suggest that theRiss/Wrirmr Interglacial of the northern Alps should be correlatedwith the whole of Stage 5 of the oxygen isotope record preservedin the deep sea cores, and not with stage 5e as various authors havepropounded. It would seem to be a matter of urgency that thisproblem be investigated further by means of the new dating methodproposed here."lhe end of this interglacial was dated at 86 - 89 ka, which to our present knowledge isrbout 25.000 years too young. Van der Wijk also recognized this problem, but solved itry proving that the uncorrected ages can yield reliable UTD dates. However, his:omparison befween iaC and U/Th ages (van der Wijk et al, 1988) for example for thefervola site in Finland is now believed incorrect. The 14C ages for Tervola (Su-688:'8.000 +4100 -2400 and Su-689: 48.000 +3500 -2400 BP) are very close to the detectionimit and are in disagreement with the existing Thermoluminescence dates (Hiitt et al,'Open system behaviour is the free exchange of uranium between peat and ground water afterleposition.2 The Riss/Wiirm interglacial is the Bavarian equivalent of the Eemian interglacial in N.W.Europe. Seeable 1.1.a1982) for both the overlying and underlying deposits. Therefore, the U/Th ages have tobe older. The present study shows that the discrepanry between the obtained young agesand the expected older ages (van der Wijk et al., 1988) was due to the short leachingtime and isotope fractionation during the leaching procedure. As the spiking of samplestook place after the separation of the leachate and residue the fractionation i.e. thedepletion of 230Th could not be observed. A brief explanation and comparisons arepresented in chapter 4 of this thesis.The assumption that a peat layer behaves as a geochemical closed system wasstudied in detail. After the first results new sampling techniques were tested both in thefield and the laboratory. After the analyses of several sites in detail we were able toconstruct a suitability diagram for the U/Th dating of peat. This makes a decision onhow to sample, treat the material and evaluate the results much easier.By careful sampling and evaluation of the obtained ages for early Weichselian andlast interglacial peat samples, it was possible to construct a new chronology for the latePleistocene in North Western Europe. Correlations were made with other chronologiesand records.ON GI,ACIALS AND INTERGI"ACIALS: A SHORT INTRODUCTION.In his orbital theory on the causes of the alternating glacial (cold) periods andinterglacial (temperate, warm) periods, the Yugoslavian astronomer Milankovitchpredicted a cycliciry (Milankovitch,1941). His theory consists of three components thatchange the intensity of the seasons. The first, the tilt of the earths axis (between 21.5 and24.5o), has a periodicity of 42.000 years and intensifies the seasons in both hemispheres.The second is the eccentricity of the earth orbit (from a near circle to an eccentricellipse) with a periodicity of 100.000 years. The growing distance to the sun will intensifythe season in one hemisphere and modify the seasons in the other. The precession orwobble is the third component. The precession of the earths axis is caused by interactionby the first two and determines whether a summer falls near or at a far point in the orbitand has a cyclicity of 23.000 years. For a long time there was a lack of an independentrecord of ice-age timing to test the cyclicity as predicted by Milankovitch.Emiliani (1955) produced the first more or less complete record of thel30enekilp6 lnd€0erel0derdeSfdrupFig. 1.1. schematic diagram showing the conelation of the Last Interglaciat/Gtacialcycle in N.W.Europe (and its vegetational clwracteistics) (after Behre, 1989)and the generalized r8O deep sea record (after Martinson et al, l9B7).alternations of interglacials and glacials. He studied the isotope composition of single cellmarine organisms called foraminifera. It is now understood that the abundance ratiobetween the natural oxygen isotopes 180/160 in the carbonate shells of foraminifera isclosely related to the amount of water locked in glaciers and ice-sheets. As waterevaporates from the relatively warm low-latitude ocean and moves away from the source,its 18O returns preferentially to the oceans as precipitation. The snow that falls on thedistant high altitude glaciers and high latitude ice-sheets is therefore relatively clepletedin 18o and as these glaciers and ice-sheets grow the oceans become more and moreenriched in 18O. This higher 180/160 abundance in sea water propagates into carbonateshells of dead foraminifera later recovered from marine sediments. By analyzing drilledT4' l lABI-E l . l .  T'he SLrb-Division of the Late Qtraternary Biostrat igraphy in N.W.Europe'Netherlands Great Bri tain I re land Sweden Finland France N. Germany GreeceHolocenel Flandrian L,i t t letonian I{olocene Flolocene Holocene Holocene IloloceneWeichsel ian2 l)evensian Mid land ian Weichsel ian Weichsel ian Weichsel ian Weichsel ianOdderade3 Upton Warren JAmtlandlnterstadialcomplexPeriipohjolaSt. Germain II Odderade ElevtheroupolisBrrirup/Amersfoort3Chelford Aghnadarragh St. Germain I Brdrup DramaDoxatonEemianr Ipswichian Gor l i an  ? [,eveiinienri Tepsankumpu Eemian Eemian PangaionSaal ian 2Wolstonian Munsterian Saal ian Saal ian Saalian Saalian Neakaterinil) Interykrciuls, 2) Glaciuls, 3) Interstadiuls.cores from the sea-floor, Emiliani found that the isotope ratio rose and fell according tothe cycles predicted by the Milankovitch theory. This new deep-sea chronology is dividedin odd and even "isotope stages". The warm interglacial stages have odd numbers andrelatively low 180/160 ratios (see figure 1.1.). The cold glacial stages have even numbersand relatively high 180/160 ratios.(see figure 1.1.).In N.W.Europe the subdivision of the I-ast Interglacial/Glacial cycle has beenbased for a considerable period of time on the lithostratigraphical evidence of thepositions of end moraines (so-called morphostratigraphy). As all the ice-advances weredescribed locally, every region or country gave different names to the same interglacialsand glacials. In table 1.1 the most important used names of the Last Interglacial/Glacialcycle are given.During the last Glacial period N.W.Europe was partly covered by ice-sheets (seefigure 5.1.). Outside the area of glaciation a lot of organic deposits were preserved.Inside the area of the maximum Weichselian glaciation less organic deposits werepreserved due to glacial erosion. As deduced from its pollen and macrofossils theseorganic deposits indicate slightly cooler conditions than today for certain intervals withinthe last Glacial. These organic deposits are often sandwiched between full glacial orperiglacial sediments and indicate climatic amelioration within the last Glacial period.These temperate stages are called interstadials. A glacial period can thus be subdividedinto stadials (full glacial conditions) and interstadials (temperate conditions). The mostimportant interstadials of the N.W.European mainland are mentioned in figure 1.1.; theN. European and British equivalents are to be found in table 1.1.At some places complete records embracing several interglacial/glacial cycles aredocumented. The records are called fnng Terrestrial Records and are the terrestrialequivalents of the deep-sea cores. Important l-ong Terrestrial Records in Europe are theTenagi Philippon (Wijmstra,1969), Padul (Florschritz et al.,IgJl), La Grand Pile(Woillard,1975) and l-es Echets (de Beaulieu and Reille,1984). As site-to-site correlationsare often problematic, much of the correlations are based on the laC chronology (of thelast 50.000 years only) (Woillard and Mook,1982) and on the recently published paperson the biostratigraphy of the Last Glacial by Behre (1989) and the special issue on theLast Interglacial/Glacial cycle of Quaternary International (Schliichter and Rutter,1989).16

NARCIS 

   University of GroningenUranium/thorium dating of late Pleistocene peat deposits in N.W. Europe.Heijnis, HendrikIMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:1992Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Heijnis, H. (1992). Uranium/thorium dating of late Pleistocene peat deposits in N.W. Europe. s.n.CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 16-07-2023CHAPTER 1INTRODUCTIONDating of peat by means of uranium series disequilibrium, (23\h/2vIJ, also known asUTD) with special emphasis on dating the early Weichselian interstadial and lastinterglacial peats in north western Europe, is the subject of this study.In principle it is possible to date peat up to 350 ka by UTD, which provides us with animportant extension of the 1aC timescale (with a range up to t 50.000 BP).The first applications of uranium series dating were to deep sea sediments. Joly(1908) observed higher Ra contents in deep sea sediments than in sediments of thecontinental shelf. He concluded that Ra was scavenged out from sea water by depositionof suspended matter. Later Piggot and Urry Q942) showed that the Ra excess wassupported by an excess of 23oTh. In the 1960's the cyclicity of interglacials and glacials,as predicted in the Milankovitch theory on the ryclicity of the ice ages, was recognisedin the 18O isotope record of deep sea cores. The chronology for this new record wasprovided by uranium series dating of fossil coral reefs in Barbados (Mesollela, 1969),New Guinea (Veeh, 1970) and direct dating of deep sea sediment.Cherdyntsev was the first who studied the possibilities of uranium series datingof terrestrial materials such as peat, speleothems and travertines. It was not until thepublication of his translated work in 1971 that his work received the attention of a largegroup of researchers throughout the world. The first results of peat dating were publishedin 1980 (Vogel & Kronfeld, 1980). Vogel's publication and more recently Kafri et al.(1983) and De Vernal et al. (1986) showed very straightforward dating of organics withsimple corrections for the presence of thorium at t=0 and an assumed closed-systembehaviour of the material to be dated. Van der Wijk (1986,1987 and 1988) studied thecorrections for detrital thorium in fossil peat samples in more detail, his work shows ingeneral a good agreement between radiocarbon ages and U/Th ages obtained for peatsamples from several sites in N.W.Europe. This is especially true if no corrections areapplied for the presence of detrital thorium.After van der Wijk had completed his studies a new project was funded by theietherlands Organisation for Scientific Research (NWO) section Earth Sciences{WON), grant number:757.357.0L1, entitled: U/Th dating of the Eemian interglacialr N.W.Europe and the correlation with the palaeotemperature curves deduced fromeep-sea cores. This study results in the present thesis. The number of potential sites isumerous. However, only a small fraction of the sites in N.W.Europe turned out to beateable by UTD. The main subject became the investigation of open-system behaviourlf peat iayers and the corrections for detrital thorium. This more thematic approach wasecessary since the first results were in obvious contradiction with geological and/oralaeoecological evidence. For some unknown reason all obtained (for detrital Thorrected) ages turned out to be too young. This problem was already noted by Vogeln 1980, but not recognised as such. He stated that:"the dates for the samples from Bavaria suggest that theRiss/Wrirmr Interglacial of the northern Alps should be correlatedwith the whole of Stage 5 of the oxygen isotope record preservedin the deep sea cores, and not with stage 5e as various authors havepropounded. It would seem to be a matter of urgency that thisproblem be investigated further by means of the new dating methodproposed here."lhe end of this interglacial was dated at 86 - 89 ka, which to our present knowledge isrbout 25.000 years too young. Van der Wijk also recognized this problem, but solved itry proving that the uncorrected ages can yield reliable UTD dates. However, his:omparison befween iaC and U/Th ages (van der Wijk et al, 1988) for example for thefervola site in Finland is now believed incorrect. The 14C ages for Tervola (Su-688:'8.000 +4100 -2400 and Su-689: 48.000 +3500 -2400 BP) are very close to the detectionimit and are in disagreement with the existing Thermoluminescence dates (Hiitt et al,'Open system behaviour is the free exchange of uranium between peat and ground water afterleposition.2 The Riss/Wiirm interglacial is the Bavarian equivalent of the Eemian interglacial in N.W.Europe. Seeable 1.1.a1982) for both the overlying and underlying deposits. Therefore, the U/Th ages have tobe older. The present study shows that the discrepanry between the obtained young agesand the expected older ages (van der Wijk et al., 1988) was due to the short leachingtime and isotope fractionation during the leaching procedure. As the spiking of samplestook place after the separation of the leachate and residue the fractionation i.e. thedepletion of 230Th could not be observed. A brief explanation and comparisons arepresented in chapter 4 of this thesis.The assumption that a peat layer behaves as a geochemical closed system wasstudied in detail. After the first results new sampling techniques were tested both in thefield and the laboratory. After the analyses of several sites in detail we were able toconstruct a suitability diagram for the U/Th dating of peat. This makes a decision onhow to sample, treat the material and evaluate the results much easier.By careful sampling and evaluation of the obtained ages for early Weichselian andlast interglacial peat samples, it was possible to construct a new chronology for the latePleistocene in North Western Europe. Correlations were made with other chronologiesand records.ON GI,ACIALS AND INTERGI"ACIALS: A SHORT INTRODUCTION.In his orbital theory on the causes of the alternating glacial (cold) periods andinterglacial (temperate, warm) periods, the Yugoslavian astronomer Milankovitchpredicted a cycliciry (Milankovitch,1941). His theory consists of three components thatchange the intensity of the seasons. The first, the tilt of the earths axis (between 21.5 and24.5o), has a periodicity of 42.000 years and intensifies the seasons in both hemispheres.The second is the eccentricity of the earth orbit (from a near circle to an eccentricellipse) with a periodicity of 100.000 years. The growing distance to the sun will intensifythe season in one hemisphere and modify the seasons in the other. The precession orwobble is the third component. The precession of the earths axis is caused by interactionby the first two and determines whether a summer falls near or at a far point in the orbitand has a cyclicity of 23.000 years. For a long time there was a lack of an independentrecord of ice-age timing to test the cyclicity as predicted by Milankovitch.Emiliani (1955) produced the first more or less complete record of thel30enekilp6 lnd€0erel0derdeSfdrupFig. 1.1. schematic diagram showing the conelation of the Last Interglaciat/Gtacialcycle in N.W.Europe (and its vegetational clwracteistics) (after Behre, 1989)and the generalized r8O deep sea record (after Martinson et al, l9B7).alternations of interglacials and glacials. He studied the isotope composition of single cellmarine organisms called foraminifera. It is now understood that the abundance ratiobetween the natural oxygen isotopes 180/160 in the carbonate shells of foraminifera isclosely related to the amount of water locked in glaciers and ice-sheets. As waterevaporates from the relatively warm low-latitude ocean and moves away from the source,its 18O returns preferentially to the oceans as precipitation. The snow that falls on thedistant high altitude glaciers and high latitude ice-sheets is therefore relatively clepletedin 18o and as these glaciers and ice-sheets grow the oceans become more and moreenriched in 18O. This higher 180/160 abundance in sea water propagates into carbonateshells of dead foraminifera later recovered from marine sediments. By analyzing drilledT4' l lABI-E l . l .  T'he SLrb-Division of the Late Qtraternary Biostrat igraphy in N.W.Europe'Netherlands Great Bri tain I re land Sweden Finland France N. Germany GreeceHolocenel Flandrian L,i t t letonian I{olocene Flolocene Holocene Holocene IloloceneWeichsel ian2 l)evensian Mid land ian Weichsel ian Weichsel ian Weichsel ian Weichsel ianOdderade3 Upton Warren JAmtlandlnterstadialcomplexPeriipohjolaSt. Germain II Odderade ElevtheroupolisBrrirup/Amersfoort3Chelford Aghnadarragh St. Germain I Brdrup DramaDoxatonEemianr Ipswichian Gor l i an  ? [,eveiinienri Tepsankumpu Eemian Eemian PangaionSaal ian 2Wolstonian Munsterian Saal ian Saal ian Saalian Saalian Neakaterinil) Interykrciuls, 2) Glaciuls, 3) Interstadiuls.cores from the sea-floor, Emiliani found that the isotope ratio rose and fell according tothe cycles predicted by the Milankovitch theory. This new deep-sea chronology is dividedin odd and even "isotope stages". The warm interglacial stages have odd numbers andrelatively low 180/160 ratios (see figure 1.1.). The cold glacial stages have even numbersand relatively high 180/160 ratios.(see figure 1.1.).In N.W.Europe the subdivision of the I-ast Interglacial/Glacial cycle has beenbased for a considerable period of time on the lithostratigraphical evidence of thepositions of end moraines (so-called morphostratigraphy). As all the ice-advances weredescribed locally, every region or country gave different names to the same interglacialsand glacials. In table 1.1 the most important used names of the Last Interglacial/Glacialcycle are given.During the last Glacial period N.W.Europe was partly covered by ice-sheets (seefigure 5.1.). Outside the area of glaciation a lot of organic deposits were preserved.Inside the area of the maximum Weichselian glaciation less organic deposits werepreserved due to glacial erosion. As deduced from its pollen and macrofossils theseorganic deposits indicate slightly cooler conditions than today for certain intervals withinthe last Glacial. These organic deposits are often sandwiched between full glacial orperiglacial sediments and indicate climatic amelioration within the last Glacial period.These temperate stages are called interstadials. A glacial period can thus be subdividedinto stadials (full glacial conditions) and interstadials (temperate conditions). The mostimportant interstadials of the N.W.European mainland are mentioned in figure 1.1.; theN. European and British equivalents are to be found in table 1.1.At some places complete records embracing several interglacial/glacial cycles aredocumented. The records are called fnng Terrestrial Records and are the terrestrialequivalents of the deep-sea cores. Important l-ong Terrestrial Records in Europe are theTenagi Philippon (Wijmstra,1969), Padul (Florschritz et al.,IgJl), La Grand Pile(Woillard,1975) and l-es Echets (de Beaulieu and Reille,1984). As site-to-site correlationsare often problematic, much of the correlations are based on the laC chronology (of thelast 50.000 years only) (Woillard and Mook,1982) and on the recently published paperson the biostratigraphy of the Last Glacial by Behre (1989) and the special issue on theLast Interglacial/Glacial cycle of Quaternary International (Schliichter and Rutter,1989).16

Uranium/thorium dating of late Pleistocene peat deposits in N.W. Europe.

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