The North Atlantic INTIMATE Project · INTegrating Icecore, MArine and TErrestrial records in the North Atlantic Region A Core Project of the INQUA Palaeoclimate Commission Project

Proceedings of The 8th International Workshop The North Atlantic INTIMATE Project

INTIMATE: Integration of Icecore, Marine and Terrestrial Records

Mýrdalur, Iceland 10-14 September 2005

The 8th INTIMATE (North Atlantic) International Workshop (Iceland, 2005) 2

The North Atlantic INTIMATE Project:

INTegrating Icecore, MArine and TErrestrial records in the North Atlantic Region

A Core Project of the INQUA Palaeoclimate Commission

Project Co-ordinator: Wim Z. Hoek Utrecht University, Faculty of Geosciences, Department of Physical Geography Heidelberglaan 2, NL-3508 TC UTRECHT, The Netherlands Phone: +31 (0)30 2532416, fax: + 31 (0)30 2531145, email: [email protected] Project Secretary: Zicheng Yu Department of Earth and Environmental Sciences, Lehigh University 31 Williams Drive, Bethlehem, PA 18015-3188 U.S.A. Phone: +1(610)758-6751, fax: +1(610)758-3677, email: [email protected]

NTIMATE Workshop 2005 in Iceland

Local Organizers: Jón Eiríksson, Arny Sveinbjornsdottir, Ólafur Ingólfsson and Sigfús Johnsen

Proceedings Editor:

Zicheng Yu ___________________________ Cover Photo: Participants of The 8th INTIMATE Workshop in front of Sólheimajökull, an outlet glacier from Mýrdalsjökull ice cap (11 September 2005; Photo by Zicheng Yu).


Workshop Program Saturday, 10 September 2005 Arrival in Reykjavík (Hotel Cabin) Sunday, 11 September 2005 9:00 – 17:00: Field excursion from Reykjavík to Höfðabrekka Monday, 12 September 2005 Breakfast: 8:00 General Session 9:00-9:20: Wim Hoek - Developments in the Integration of Palaeoclimatic Records from the

North Atlantic Region for the Period from 30-8 ka cal BP 9:20-9:40: Rewi Newnham - The Australasian INTIMATE Initiative: Progress and Plans 9:40-10:30: General Discussion: The Workshop Plan and Beyond 10:30-11:00: Coffee Break Chronology and Correlation I: Ice Cores and Tephras 11:00-11:20: Sigfús Johnsen - A Synchronized Dating of Three Greenland Ice Cores 11:20-11:40: Katrine Anderson - Greenland Ice Core Chronology 2005: Stratigraphic

Dating 8 – 30 kyr b2k 11:40-12:00: Siwan Davies - Tracing Volcanic Events in the Greenland Ice Cores 12:00-12:20: Sean Pyne-O’Donnell - Multiple Eruptions of the Borrobol Tephra Source

Volcano during the Lateglacial Interstadial 12:20-13:20: Lunch 13:20-13:40: Christine Lane - The Tephrochronolgy of Lake Soppensee – Improving

European Terrestrial Correlations 13:40-14:00: Mark Pollard - Numerical Considerations in the Correlation of Tephra

Geochemistry 14:00-14:20: Nanna Noe-Nygaard - Weichselian Tephras in Denmark Located on Two New

Localities - The Slotseng Basin in Jylland and The Tøvelde Basin on Møn 14:20-14:40: Jan Mangerud - The Discovery of a New Cryptotephra with a Geochemical

Composition Similar to the Vedde Ash 4:40-15:00: Discussion on Ice Cores and Tephras 15:00-15:30: Tea Break Chronology and Correlation II: 14C Dating and Tree Rings 15:30-15:50: Jan Mangerud – Present Day and Late Glacial Marine 14C Reservoir Ages of

Surface Waters in the North Atlantic-Norwegian Sea 15:50-16:10: Christopher Bronk Ramsey - Deposition Rates for 14C Dates 16:10-16:30: Simon Blockley -Testing Age Models of Lateglacial and Early Holocene

Sediment Records 16:30-16:50: Klaus F. Kaiser - Status of the Swiss Lateglacial Tree-ring Chronologies 16:50-17:10: John Lowe - Tightening the Chronology of Palaeoenvironmental Events in the British Isles during the Last Termination 17:10-17:30: Discussion on 14C Dating and Other Chronology Issues Dinner


Tuesday, 13 September 2005 Breakfast: 8:00 The North Atlantic Region 9:00-9:20: Holger Cremer - The Late Glacial – Early Holocene Transition in Northeast

Greenland (70°-77° N): Evidence from Lake Sediments 9:20-9:40: Morten Fischer Mortensen - New Results on Late Glacial Vegetation

Development in Southern Denmark - Climate Oscillations and Bio-stratigraphy 9:40-10:00: Stefan Engels - Rapid Climatic Events as Recorded in Middle Weichselian

Thermokarst Lake Sediments 10:00-10:20: Petras Sinkunas - Lateglacial Palaeovegetation Records - Key Sites of

Lithuania 10:20-10:50: Coffee Break 10:50-11:10: Gill Plunkett - Examining Evidence for Solar Forcing of Climate c. 2800 cal

BP with the Aid of Distal Tephras 11:10-11:30: Jón Eiríksson - Lateglacial Tephra Stratigraphy and Climate Related Events on

the North Icelandic Shelf 11:30-11:50: Karen Luise Knudsen - Palaeoceanographic Changes through GS2, GI-1, GS-

1 and the Early Holocene off North Iceland 11:50-12:10: Morten Hald - Oceanic Surface Conditions on the West Spitsbergen

Continental Margin during the Last 15,000 Years 12:10-12:30: Discussion on the North Atlantic Region 12:30-13:30: Lunch Beyond the North Atlantic and Modelling 13:30-13:50: Takeshi Nakagawa - Lake Suigetsu Update: Correlation Between “SG vyr BP”

and “IntCal-04 cal BP” (2005 Temporary Version), and two Different Types of Forcing to the Deglacial Climate Changes

13:50-14:10: Zicheng Yu - Contrasting Late-glacial and Early Holocene Climate Shifts in South-central Alaska: Stable Isotope Record from Lacustrine Carbonate

14:10-14:30: Hans Renssen - Rapid Climate Changes in the North Atlantic Region During the Last Termination: Were They Really Synchronous?

14:30-15:00: Discussion and Instructions for Break-up Groups 15:00-15:30: Tea Break 15:30-17:30: Break-up Workshop Sessions: Key Records on a Common Time Scale Dinner Wednesday, 14 September 2005 Breakfast: 8:00 9:00-10:30: Reports from Break-up Group Sessions 10:30-11:00: Coffee Break 11:00-12:30: Final Wrap-up Discussion: How to Proceed? 12:30-13:30: Lunch 14:00: Departure for Keflavik


Abstracts (In the order of presentations)


Developments in the Integration of Palaeoclimatic Records from the North Atlantic Region for the Period from 30-8 ka cal BP

Wim Z. Hoek

Utrecht University, Department of Physical Geography, Faculty of Geosciences, Heidelberglaan 2, 3508 TC Utrecht, The Netherlands; email: [email protected]

The development of INTIMATE event-stratigraphy for the Last Glacial-Interglacial Transition provided a template to compare other independently dated palaeoclimate records with the high-resolution Greenland oxygen isotope records. The application of this event-stratigrapy, which is based on the GRIP ice core record using the ss08c (modelled) timescale, revealed some interesting patterns in time and space which might be associated to differences in response or, alternatively, erroneous dating. The new Greenland Ice Core Chronology opens up the potential to refine and extend the existing event-stratigraphic framework. The new INTCAL04 calibration dataset may provide us with more accurate calendar ages of the events recorded in different 14C dated marine and terrestrial records up to 26 ka cal BP. Re-evaluation of existing data in this new light revealed some interesting conclusions. Recent advances in tephrochronology lead to the discovery of continuously increasing number of known and unknown, but chemically identical, tephra layers in ice-core, marine and terrestrial records. Especially these tephra layers can be used for detailed correlation, and above this, for the validation of the different timescales. For the marine realms, the combination of 14C dating and tephrochronology, will give a better insight in the highly variable reservoir ages in the North Atlantic marine records. Detailed analysis of well-dated palaeoclimatic records may reveal spatial and temporal patterns in climate. One of the major goals of the North Atlantic INTIMATE project is the compilation of key records presented on a common timescale, which will serve for comparison with other regional INTIMATE groups. Furthermore, the integration of records may result in a series of time-slice map for the main events over the Last Glacial-Interglacial Transition for the North Atlantic region.


The Australasian INTIMATE Initiative: Progress and Plans

Rewi Newnham1, Jamie Shulmeister2, Brent Alloway3 and Simon Haberle4 1School of Geography, University of Plymouth, Plymouth PL4 8AA, UK; e-mail:

[email protected] 2Department of Geological Sciences, University of Canterbury, Private Bag 4800,

Christchurch, New Zealand 3Institute of Geological and Nuclear Sciences, PO Box 303-68, Lower Hutt 6315, New

Zealand 4Department of Archaeology and Natural History, RSPAS, Australian National University,

Canberra ACT 0200, Australia The Australasian INTIMATE project (INQUA project number: 0406), conceived at the 2003 INQUA Congress in Reno, is a direct response to the objective to broaden the geographical scope of the North Atlantic INTIMATE group. The two groups are to communicate progress to one another and pursue similar objectives with the ultimate collective goal of synthesising data from their respective regions and making comparisons at the global scale. At the 2004 North Atlantic Workshop in Bonn, we reported on progress with the Australasian initiative during the first 18 months. Here we report on subsequent progress. As during the previous year, and essentially because of logistical constraints, the Australasian INTIMATE project has continued to operate by convening broadly parallel meetings held separately in Australia and New Zealand with associated outputs co-ordinated at the national level (Table 1). The two national sectors came together in December 2004, at the first full meeting of the Australasian INTIMATE group, where it was agreed that such combined meetings should take place approximately every 12 months, in addition to the parallel national meetings. The next integrated Australasian INTIMATE meeting is scheduled for Northland, New Zealand, in February 2006 (Table 1). The main outcome to date has been the selection of a small number of key records that are considered to best represent climate change for the interval ca 30 - 8 ka (Table 1). Two posters have been produced depicting these records for the Australian and New Zealand regions separately and these will be presented and discussed in Iceland. The New Zealand records have also been published in a separate report (Barrell et al., 2005). Both posters adopt a similar format that depicts both high-resolution (stable isotope, pollen) terrestrial and marine records and fragmentary (glacial advance/retreat, fluvial aggradation, aeolian, coral, dendrochronological) terrestrial records. Key ice core records from Greenland and Antarctica are included for comparison. These posters will provide the basis for paper publications planned for both Australian and New Zealand INTIMATE groups in the very near future. This task completes the first of two major agreed targets; the second, currently in progress, being the production of another pair of posters in which the key records already identified will be used to develop an event stratigraphy for each region. Ultimately these two event stratigraphies will be compared and reconciled in advance of the INQUA 2007 meeting in Cairns.

The Australasian INTIMATE group is grateful to INQUA for continued financial support that enables younger scientists to attend our meetings.


Table 1. Meetings of the Australasian INTIMATE group Dates Venue Forum Comments & Outputs Aug 2003

Reno, USA Australasian INTIMATE Inaugural mtg

Dec 2003

Dunedin, NZ

Australasian INTIMATE Demonstration Workshop

Aug 2004

Lower Hutt, NZ

First NZ INTIMATE workshop

• Proceedings published (Alloway, B.V. 2004) & available at:

http://www.paleoclimate.org.nz/images/2004_NZ-INTIMATE_Proceedings.pdf • Website constructed (www.paleoclimate.org.nz)

Sep 2004

Sydney, Aust.

First OZ-INTIMATE workshop

• Summary and agreed outcomes available at: http://www.aqua.org.au/AQUA/frames_INTIMATE.html

Dec 2004

Cradle Mt, Tasmania, Aust

First Australasian INTIMATE workshop

• See Program and abstracts at: http://palaeoworks.anu.edu.au/AQUA2004abs.pdf • Draft NZ & Australian posters of key records presented • Australian poster available at:

http://palaeoworks.anu.edu.au/publications.html July 2005

WellingtonNZ

Second NZ-INTIMATE

workshop *

• Poster-1 published & available at http://www.paleoclimate.org.nz/images/NZpaleoclimate_poster_high-res.jpg

• Proceedings & Outcomes published (Alloway & Shulmeister, 2005) & available at:

http://www.paleoclimate.org.nz/images/proceedings_of_2005_NZ_INTIMATE_meeting.pdf http://www.paleoclimate.org.nz/images/outcomes_2005_int_meeting.pdf

Feb 2006

Northland, NZ

Second Australasian INTIMATE workshop

A written summary of this meeting by David Lowe to be published in Quaternary Australasia can be viewed/downloaded at http://www.paleoclimate.org.nz/images/2005_INT_Meeting_Report_David_Lowe.pdf References Alloway, B.V. and Shulmeister, J. (editors) 2005: Proceedings of the 2005 NZ-INTIMATE

Meeting, GNS Rafter Laboratory, Wellington: July 4-5 2005. Institute of Geological & Nuclear Sciences science report 2005/18. 29 p.

Alloway, B.V. 2004 NZ-INTIMATE Meeting, GNS Rafter Laboratory, Wellington: 23-24 August 2004. Institute of Geological & Nuclear Sciences science report 2004/22. 43 p.

Barrell, D., Alloway, B.V., Shulmeister, J., Newnham, R.M. (editors), 2005. “Towards a climate event stratigraphy for the last 30,000 years in New Zealand”. Institutre of Geological & Nuclear Sciences science report 2005/07. 12 pages & poster.


A Synchronized Dating of Three Greenland Ice Cores

Bo Vinther, Henrik B Clausen and Sigfus J. Johnsen, The Copenhagen Ice Core Dating Initiative and the NGRIP Chemistry Group, Ice and Climate

Research, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen Ø, Denmark

As part of the effort to create the new Greenland Ice Core Chronology 2005 (GICC05) ECM reference horizons have been used to match the DYE-3, GRIP and NGRIP ice core records throughout the Holocene. Exploiting that the three ice cores were drilled at locations with different climatic conditions and differences in ice sheet flow, the main annual layer counting has been carried out on the most suited records only. For each matched section, however, supplemental counting was done on data from all cores in order to verify the validity of the ECM match. After the verification, the main dating was transferred to all records using the ECM reference horizons as tie points. An assessment of the annual layer thicknesses in each core section confirms that the new synchronized dating is consistent for all three cores. The data series used for the main annual layer counting are the DYE-3, GRIP and NGRIP stable isotope records and the GRIP and NGRIP CFA records. As the high accumulation rate at the DYE-3 drill site makes the seasonal cycle in the DYE-3 stable isotope record the most resistant to firn diffusion, an effort was made to extend and complete the DYE-3 Holocene record. The new synchronized dating relies heavily on this unique record of more than 75,000 isotope samples that now reaches from the present and all the way back through the 8.2 kyr event. Below the 8.2 kyr event, the main annual layer counting is carried out on the GRIP and NGRIP CFA series. The synchronized dating of the DYE-3, GRIP and NGRIP ice cores facilitates the creation of a common history of volcanic events during the entire Holocene. This work is in progress and significant improvements both in the magnitude estimate and dating of prehistoric Holocene eruptions are expected. The GICC05 dating moves back the termination some 200 years as compared to previous datings of the GRIP record. Comparing the GICC05 dating to both the official GISP2 dating and to a dating relying more heavily on the GISP2 visual stratigraphy, it is found that the GICC05 dating is generally in better agreement with the GISP2 visual stratigraphy dating. In fact the GICC05 dating and the GISP2 visual stratigraphy dating agree on the age of the termination within 25 years, whereas the difference between the official GISP2 dating and the GICC05 dating is some 80 years at the termination. Correlations obtained between the Greenland 10Be records and the 14C production curves suggest that the age of the preporeal period could be overestimated by some 150 years, a problem still being debated.


Greenland Ice Core Chronology 2005: Stratigraphic Dating 8 – 30 kyr b2k

Katrine Krogh Andersen, Anders Svensson and Sune Olander Rasmussen, The Copenhagen Ice Core Dating Initiative and the NGRIP Chemistry Group, Ice and

Climate Research, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen Oe, Denmark

Results of the Greenland Ice Core Chronology 2005 (GICC05) for the period 8-30 kyr b2k (before year 2000 AD) will be presented here. Results for the later part of the Holocene (0-8 kyr b2k) will be presented by Sigfus Johnsen. High resolution records have been obtained from the NGRIP ice core enabling a stratigraphic dating of the past 41 kyr. The high resolution profiles used for this work are: (I) Continuous Flow Analysis (CFA) of the mass concentrations of dust, Ca++, Na+, NH4

+, SO4--, NO3

-, and of electrolytical conductivity; (II) Electrical Conductivity Measurement (ECM) of the solid ice; and (III) the light intensity curve of the recorded Visual Stratigraphy (VS). In the section from the 8.2 ka cold event to the Younger Dryas – Preboreal transition the new NGRIP data have been used in conjunction with CFA measurements of Ca++, NH4

+ and H2O2 data from the GRIP ice core. This resulted in an enhanced understanding of the seasonality displayed in the different chemical species, and a more reliable identification of the annual layers. The YD-Preboreal transition on the new timescale is older than on the previous GRIP, NGRIP and GISP2 timescales. Before the transition to the Preboreal the stratigraphy is based on NGRIP data alone. Over the Bølling-Allerød-Younger Dryas period all CFA measurements resolve the annual layers, and a distinct seasonal pattern is often seen during the warmer periods. In the glacial part of the record the resolution becomes marginal for some of the chemical species. During cold periods, where annual layers are thin, the counting is mostly based on VS, ECM and electrolytical conductivity, which have the highest resolution. During milder periods the dating relies more on the chemical records, which generally provide a single annual peak and sometimes seasonal resolution. The maximum counting error is estimated to be 3 % in the Younger Dryas, Allerød and Bølling periods and around 7% for the older part of the record. Comparisons of GICC05 with the modeled “ss09sea” timescale, the GISP2 timescale and INTCAL04 will be presented.


Tracing Volcanic Events in the Greenland Ice Cores

Siwan M. Davies1, Stefan Wastegård2, N. J. Pearce3, Mattias Bigler4, Sigfus, J. Johnsen4, Jørgen Peder Steffensen4 and Anette K. Mortensen5

1Department of Geography, Swansea University, Singleton Park, Swansea, SA2 8PP, UK; e-mail: [email protected]

2Department of Physical Geography and Quaternary Geology, Stockholm University, S-106 91 Stockholm, Sweden

3Institute of Geography and Earth Sciences, University of Wales, Aberystwyth, Llandinum Building, Penglais Campus, Aberystwyth, SY23 3DB

4Department of Geophysics, University of Copenhagen, Juliane maries vej 30, 2100 Copenhagen Ø, Denmark

5Nordic Volcanological Institute, Askja, University of Iceland, Sturlugata 7, 101 Reykjavik, Iceland

Several abrupt and rapid climatic events characterized the period spanning 30-8 ka BP, with significant temperature shifts of 5–10 ºC, some of which occurred within decades, affecting the whole of the North Atlantic region. A key question that is essential to the understanding of the climate-forcing mechanisms is whether these climatic instabilities as well as the environmental response to them were synchronous within the continental, marine and polar realms. Due to the rapidity of these fluctuations, however, the required level of precision by which these past climatic events can be dated and correlated is currently unattainable using the traditional dating methods. Tephrochronology is one of the few techniques that has the potential to resolve some of these issues, particularly as recent advances in the detection of cryptotephra horizons (tephra horizons that are invisible to the naked eye) in areas not traditionally associated with tephrochronological research highlights the scope for utilising this correlation tool on a continent-wide scale. Here we report on the work being undertaken to identify and geochemically characterise tephra horizons within the annually-resolved Greenland ice-core records. The high resolution NGRIP chemostratigraphy (e.g. sulphate and calcium data) obtained by continuous flow analysis is employed to pinpoint the presence of cryptotephra horizons. Several visible and cryptotephra horizons are detected and analysed by electron microprobe analysis within the NGRIP and GRIP ice-cores spanning this period (e.g. Mortensen et al. 2005). These include a number of previously unreported tephra deposits of Icelandic origin as well as some well-known marker horizons. One such example is the Fugloyarbanki tephra (23 14C ka BP) - a widespread marker horizon in North Atlantic marine records. Not only does this tephra horizon provide a key tie-point for the correlation of marine and ice-core sequences during Oxygen Isotope Stage 2, but also allows an estimation of the magnitude of the marine radiocarbon reservoir error at this time. Trace element data are also presented for this tephra - analysed by single grain Laser Ablation-Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). Overall these preliminary results demonstrate the potential of LA-ICP-MS as a diagnostic technique for geochemical fingerprinting of small basaltic glass shards, but it is clear that a number of laboratory improvements are required to improve the capabilities of this method. Reference Mortensen, A. K., Bigler, M., Grönvold, K., Steffensen, J. P. & Johnsen, S., J. 2005: Ash

layers from the Last Glacial Termination in the NGRIP ice core. Journal of Quaternary Science 20, 209-219.


Multiple Eruptions of the Borrobol Tephra Source Volcano during the Lateglacial Interstadial

Sean Pyne-O’Donnell

Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK The Borrobol Tephra was first discovered at the type site of Borrobol in northern Scotland (Turney et al., 1997). Its estimated age at 14,400 14C cal yrs BP places it in a position demonstrated by loss on ignition (LOI) curves to mark the onset of Interstadial warming. In a number of subsequent studies, however, microtephra horizons of equivalent geochemistry have been found to occur much later in the Interstadial as demonstrated by a stratigraphically higher LOI position or significantly earlier dates. Davies et al. (2004) date an horizon from southern Sweden at 13,900 Cariaco varve yrs BP, while Ranner et al. (2005) estimate the age of a ‘Borrobol-like’ microtephra horizon from northwest Scotland at 13,610 14C cal yrs BP. These discrepancies in age and stratigraphic position have led to the hypothesis that there was more than one eruption of the Borrobol Tephra source volcano during the Lateglacial Interstadial. To date, however, sequences containing multiple microtephra horizons have not been found. This work demonstrates the presence of multiple rhyolitic microtephra horizons of Borrobol-like geochemistry occurring together in a number of Lateglacial sequences from Scotland. The earlier horizon occurs in the conventional early Interstadial Borrobol Tephra position of Turney et al. (1997). A later microtephra is also seen in a stratigraphically higher position in the approximate Bølling-Allerød transition region, with a geochemistry which is indistinguishable from the lower Borrobol Tephra, thus suggesting that they both derive from the same source volcano. The large stratigraphic separation clearly demonstrates that the later tephra is a separate event and is deserving of its own name. Therefore, it has been named the Druim Tephra. A further complication exists, however, concerning the stratigraphic distribution of the Borrobol Tephra itself. A number of sequences suggest this horizon possesses a stratigraphically bimodal distribution, with the type site itself clearly demonstrating the presence of two separate peaks below the Druim Tephra. This suggests the Borrobol Tephra was the result of two separate events closely spaced in time which have become merged together in sequences possessing a low early Interstadial sedimentation rate. A higher sedimentation rate at the Borrobol type site may account for the resolution of the two separate peaks, which have been named here as the earlier Borrobol ‘A’ Tephra, and the later Borrobol ‘B’ Tephra. The presence of small quantities of basaltic shards accompanying both the Borrobol Tephra and Druim Tephra at a number of these sites suggests the presence of basaltic components for these eruptions, though whether the basaltic material derives from the same eruptions as the rhyolitic material or from a separate but coincident source is unknown. The presence of basaltic shards in the NGRIP ice core stratigraphy (Mortensen et al., 2005) in approximately the same positions as the Borrobol Tephra and Druim Tephra holds the intriguing possibility that these tephras may be datable by correlation with the ice cores. References Davies, S. M., Wohlfarth, B., Wastegård, S., Andersson, M., Blockley, S., & Possnert, G.,

(2004). Were there two Borrobol Tephras during the early Late-glacial period: implications for tephrochronology? Quaternary Science Reviews, 23, 581-589.


Mortensen, A. K., Bigler, M., Grönvold, K., Steffensen, J. P. & Johnsen, S. J. (2005). Volcanic ash layers from the Last Glacial Termination in the NGRIP ice core. Journal of Quaternary Science, 20, 209-219.

Ranner, P. H., Allen, J. R. M. & Huntley, B. (2005). A new early Holocene cryptotephra from northwest Scotland. Journal of Quaternary Science, 20, 201-208.

Turney, C. S. M., Harkness, D. D. & Lowe, J. J. (1997). The use of microtephra horizons to correlate late-glacial lake sediment successions in Scotland. Journal of Quaternary Science, 12, 525-531.


The Tephrochronolgy of Lake Soppensee – Improving European Terrestrial Correlations

Christine Lane1, Simon P.E.B. Blockley1, Andy F. Lotter2 and Emma Lightfoot1

1 Research Laboratory for Archaeology, University of Oxford, 6 Keble Road Oxford, UK 2University of Utrecht, Utrecht, The Netherlands

Preliminary results from tephrochronological investigations in Lake Soppensee, central Switzerland, reveal the occurrence of multiple previously undetected microtephra horizons. The sediment record of Lake Soppensee stretches back to around 15 000 14C yr BP, and has been much studied over the last two decades. From the mid-early Holocene to the Lateglacial (c.6000 and 12 000 14C yr BP or c.7000 and 13 000 cal yr BP, Hajdas et al, 1993) the sediments of Lake Soppensee provide a nearly continuous annually laminated record. The lake holds a valuable high-resolution record of paleolimnological, vegetational and climatic changes during the Holocene and Lateglacial, accessed through oxygen isotope, pollen and micromorphological studies (Lotter et al., 1992, Lotter, 2001). The Lateglacial Laacher See Tephra (LST) and the early Holocene Vasset/Kilian Tephra (VKT), both visible horizons, have been used as marker layers in correlations between regional proxy archives (Lotter et al., 1992). Both the LST and VKT are found widely across the Swiss Plateau and Central Europe, but rarely are they characterised beyond their optical appearance and stratigraphical location. This study has carried out geochemical analysis of tephras within Soppensee, allowing the correlation of the LST to be made more precisely with specific eruptive phases. Besides the LST and VKT, evidence for up to 5 microtephra deposits, of varying size, has been located in the Soppensee cores. Geochemical analysis of these tephras is in progress. Two microtephras have been identified above the VKT, thus occurring in the early-mid Holocene. Between the VKT and the LST, there are two or threes poorly defined microtephra deposits, requiring further investigation at this stage. Below the LST, there is evidence for a final microtephra horizon, however geochemical analysis suggests down-core migration of glass shards may have taken place. On the basis of geographical location, and European eruptive histories, the microtephras found are believed to have been derived from the Massif Central, France, and/or Italian volcanic sources. At present, sampling resolution is down to 1cm, but there remains the potential for attributing each ash fall deposit to an individual varve layer. References Lotter, A.F., Eicher, U., Siegenthaler, U., Birks, H.J.B. 1992. Late-glacial climatic oscillations

as recorded in Swiss lake sediments. Journal of Quaternary Science, 7 (3), 187-204. Hajdas, I., Ivy, S., Beer, J., Bonani, G., Imboden, D., Lotter, A.F., Sturm, M. and Suter, M.

1993. AMS radiocarbon dating and varve chronology of Lake Soppensee: 600 to 12 000 14C years BP. Climate Dynamics, 9, 107-116.

Lotter, A.F. 2001. The palaeolimnology of Soppensee (Central Switzerland), as evidenced by diatom, pollen and fossil-pigment analyses. Journal of Paleolimnology, 25, 65-79.


Numerical Considerations in the Correlation of Tephra Geochemistry

Mark Pollard Research Laboratory for Archaeology, University of Oxford, 6 Keble Road Oxford, UK

The use of tephra layers as a technique for correlating climate sequences is a key tool in the INTIMATE approach. At the heart of tephrochronology is the use of the geochemical composition (major and minor elements) to 'fingerprint' a tephra layer to a particular eruption. This paper outlines the statistical considerations that need to be taken into account when performing chemical correlations. Using geochemical data from tephra layers in the Adriatic, generated at Oxford examples of logratio analyses and multivariate approaches will be presented and considered.


The Weichselian Tephras in Denmark Located on Two New Localities - The Slotseng Basin in Jylland and The Tøvelde Basin on Møn

Nanna Noe-Nygaard1, Thomas Jørgensen1, John Lowe2, Alison Macleod2 and Ian Matthews2 1Geological Institute, Copenhagen University, Østervoldgade 10, 1350 K Copenhagen, Denmark 2Centre for Quaternary Research, Department of Geography, The Royal Holloway University of

London Egham Surrey TW20 OEX, England In recent years the usefulness of micro tephra as time-parallel markers has become apparent. The more widely spread ash falls may provide the basis for high-resolution correlation between marine, terrestrial and ice-core records. This correlation possibility also offers a potential for testing hypotheses of synchronous climatic changes. We here present the preliminary results of micro tephra from two lacustrine study basins in Denmark - the East Danish Tøvelde basin and the West Danish Slotseng basin, which have been comprehensively and well dated. The Tøvelde basin is a key locality for the study of the Late Weichselian development. It is situated on the south coast of the island of Møn and its elevation is 2.5-7.5 m above sea level. The lake basin is exposed in a south-west/north-east oriented coastal section facing the Western Baltic Sea. The sediment record covers a time span from about 14,700 to 9,000 cal yr BP. Onset of climate amelioration and environmental stability is reflected by organic-rich deposits at 14,300 cal yr BP following the deglaciation of the Young Baltic readvance. In the report on micro tephra for Lake Tøvelde 1and 2 it is concluded that both core samples contain discrete tephra layers of morphologically similar and with highly vesicular and thus unsuitable for geochemical analyses. The shards show great similarities with the Lacher sees Tephra and occur just after the Gertzensee oscillation. Some tephra shards had a geochemical composition compatible with the Sluggan tephra. The Late Weichselian lake succession of the Slotseng basin in western Denmark is of great interest because it represents the first find of the earliest reindeer hunters in the country at about 15,000 cal yr BP in the early Bølling interstadial time (15,000 – 13,800 cal BP), the first relatively warm spell following onset of Weichselian deglaciation. Although the Bølling interstadial is defined in Denmark it has hitherto been known only from thin layers in a few borings. Slotseng is the first locality where the Bølling succession has been exposed in an open pit by a relatively thick layer containing reindeer antlers and bones, including a vertebrate penetrated by a flint arrowhead, still in place. A highly complex, partly inverted stratigraphy of the superficially straightforward fossiliferous lacustrine succession has been demonstrated at the Slotseng site. The Bølling succession has been well dated analysed and contain Tephra shards compatible with the Borrobol ash. In the preliminary report Tephra from the Vedde ash has been located in the Younger Dryas succession, and further shards are located from the early Holocene deposits.


The Discovery of a New Cryptotephra with a Geochemical Composition Similar to the Vedde Ash

Jan Henrik Koren, Jan Mangerud and John Inge Svendsen

Department of Geoscience, University of Bergen, Allégt. 41, N-5007 Norway A new volcanic ash with a geochemistry almost identical to the rhyolitic component of the Vedde Ash, but some 2500 14C years older, has been found in Sunnmøre, western Norway, not far from the type locality of the Vedde Ash (Mangerud et al., 1984). It is found above the marine limit, and therefore has to be air-born all the way from Iceland. It should therefore also be found in the sea between Iceland and Norway. In order to have an easy reference we preliminary name it the Dimna Ash from the island where it first was found. It occurs in a palaeo-lake with typical late glacial stratigraphy; including a basal unit of grey silt and sand overlain by brownish Allerød mud and grey Younger Dryas silt, the latter with a up to 48 cm thick bed of Vedde Ash. A number of AMS dates from macros of terrestrial plants support this stratigraphy. The ash was found in the basal unit, about 120 cm below the base of the Vedde Ash. It was not visible to the naked eye and was detected through the application of the density separation procedure developed by Turney (1998). The ash is concentrated in a zone with two distinct peaks, 20 cm apart. The lowermost peak has an estimated density of 10 600 grains/cm3 and the uppermost of 12 900 grains/cm3, calculated relative to un-treated sediment. The two peaks might possibly indicate two separate eruptions from the same volcano. The uppermost peak is located 25 cm below the lowermost 14C dates yielding 12,780 ± 60 and 12,840 ± 70 B.P. (aprox. 15100 OxCal calibrated years B.P.). Unfortunately we have not found plant macros below the ash. Grains similar to the basaltic component of the Vedde Ash have not been found in the ash reported here. The ash is found in the oldest lacustrine sediments and we can therefore not rule out the possibility that it originally was deposited on the surface of the Scandinavian Ice Sheet and washed into the lake when the ice margin was in the vicinity of the lake. This will be tested by coring lakes that were ice-free even earlier. Ashes with a similar geochemistry to Vedde but with different ages have been reported previously by Bond et al. (2001) and Mortensen et al. (2005). The ash IA2 described by Bond et al is more than 1000 years younger than ours, but was ice-rafted into the N-Atlantic. If the IA2 ash originally was deposited on an Icelandic glacier, one cannot rule out the possibility the IA2 and the Dimna Ash stem from the same eruption. The ash in the NGRIP core (Mortensen et al., 2005) was deposited during Early Ynger Dryas and is certainly younger than ours. These results underpin the demand for the application of LA-ICP-MS (Laser ablation inductively coupled plasma mass spectrometry) analysis to distinguish between single eruptions from the same source volcano. This work is part of the Master thesis of Koren and is still underway. References Bond, G., Mandeville, C., and Hoffmann, S. (2001). Were rhyolitic glasses in the Vedde Ash

and in the North Atlantic's Ash Zone 1 produced by the same volcanic eruption? Quaternary Science Reviews 20, 1189-1199.

Mangerud, J., Lie, S. E., Furnes, H., Kristiansen, I. L., and Lømo, L. (1984). A Younger Dryas ash bed in Western Norway, and its possible correlations with tephra in cores from the Norwegian Sea and the North Atlantic. Quaternary Research 21, 85-104.

Mortensen, A., Bigler, M., Grønvold, K., Steffensen, J. P., and Johnsen, S. (2005). Volcanic ash layers from the last glacial termination in the NGRIP ice core. Journal of Quaternary Science 20, 209-219.


Turney, C. (1998). Extraction of rhyolitic component of Vedde microtephra from minerogenic lake sediments. Journal of Paleolimnology 19, 199-206.


Present-day and Late-glacial Marine 14C Reservoir Ages of Surface Waters in the North Atlantic-Norwegian Sea

Jan Mangerud*, Stein Bondevik, Steinar Gulliksen, Hilary H. Birks, Paula Reimer,

Anne Karin Hufthammer and Tore Høisæter *Department of Geoscience and Bjerknes Centre for Climate Research, University of Bergen,

Allégt. 41, N-5007 Bergen, Norway; e-mail: [email protected] In order to compare radiocarbon dates on samples from marine organisms with dates from terrestrial plants and animals, the marine samples have to be corrected for a marine reservoir age. We have mapped the present day marine reservoir ages in this area by dating 22 whales collected AD 1860-1901 and 23 molluscs collected AD 1857-1926. Whales feed only on plankton and pelagic animals and will provide the reservoir age for the open ocean surface water. However, they travel large distances and integrate the reservoir ages of water masses along their way. Mean reservoir ages are 369 ± 30 and 353 ± 35 yrs, relative to tree ring dates of IntCal04 and British oak, respectively. Molluscs are stationary and monitor the sea water passing their living site. However, many mollusc species also take up C from the sediments, and coastal water may often contain some continental C. Mean reservoir ages for Atlantic-water-molluscs are 435 ± 31 and 399 ± 35 yrs relative to IntCal04 and British oak, respectively. For the surface water in the N-Atlantic and Norwegian Sea we recommend to use the mean of the two sets, i.e. reservoir ages of 400 ± 50 and 380 ± 35 years relative to Intcal04 and British oak respectively, and corresponding ∆R values of 40 ± 45 and 20 ± 45 for the parts of the Holocene where specific time-dependent reservoir ages are not determined. The reservoir ages relative to British oak may best reflect regional processes, and we therefore prefer those, whereas IntCal04 ages are much more precisely determined, but dominated by trees from NW-USA in this time period. The reservoir ages for Allerød-Younger Dryas are obtained by dating parallel samples of terrestrial plant fragments and marine shells from sediment cores from the outermost western coast of Norway. The marine mud contains both terrestrial plant fragments blown or washed in from adjacent land and in situ marine shells. In the earliest period (13,800-14,500 cal yrs BP) the reservoir age is 300-400 years, similar to present day values. This suggests that the exchange of CO2 between the atmosphere and the surface ocean was comparable to the present. During a short interval 13,200-13,500 cal yrs BP we found higher reservoir ages of 500-600 years coinciding with lower organic carbon content in our cores, and an inter-Allerød fluctuation seen in marine records. During the early YD the reservoir ages increased gradually from 400 to 650 years, causing a 700-14C year-long plateau, centred at 11,000 14C yrs BP, for marine dates at a time of high resolution for terrestrial dates. This is related to a strong decline in marine ∆14C from 12,700-12,100 cal yrs BP which may reflect increased annual sea-ice cover, reducing the rate of CO2 exchange between the atmosphere and the sea surface. On the other hand, our dates show that the marine 14C ages decreased rapidly from 10,600 to 10,100 14C yrs BP in the North Atlantic, indicating that the reservoir ages dropped about 300 years during a century at the end of the YD. This is the time of the well-known 10,000 14C year plateau in terrestrial dates, and the result is that one can obtain higher resolution of calibrated marine 14C dates at the YD/Preboreal transition than for terrestrial 14C dates. This presentation is based on two manuscripts that will be submitted about 1 Sept 2005: Bondevik, S., Mangerud, J., Birks, H. H., Gulliksen, S., and Reimer, P.: Late-glacial reservoir

ages of surface waters in the North Atlantic. Mangerud, J., Bondevik, S., Gulliksen, S., Hufthammer, A.K., Høisæter, T.: Marine 14C


reservoir ages for whales and molluscs from the North Atlantic, Norwegian Sea a nd coast of Norway.


Deposition Rates for 14C Dates

Christopher Bronk Ramsey Research Laboratory for Archaeology, University of Oxford, 6 Keble Road, Oxford OX1

2JD, UK When using sedimentary records for high resolution chronology it is essential to make a proper estimate of the uncertainties in age as a function of depth or varve count. A new version of the radiocarbon calibration program OxCal is nearing completion. This provides a number of different mathematical models for the analysis of such records. In this paper the range of methods is discussed. Taking the Soppensee record as an example, analyses using either varve count or depth are considered and tested.


Testing Age Models of Lateglacial and Early Holocene Sediment Records

Simon Blockley1, Maarten Blauuw2 and Chris Bronk Ramsey1

1Research Laboratory for Archaeology, University of Oxford, 6 Keble Road Oxford, UK. 2Centro de Investigación en Matemáticas, A.P. 402, Guanajuato 36000, Mexico.

There is significant scientific interest in understanding the nature and timing of regional and global responses to abrupt climate change during the transition from the last glacial to the Holocene, coupled with strong evidence for numerous abrupt climatic oscillations over this period. The very abrupt nature of these climatic events, however, and the possibilities of asynchronous responses in different environments and regional climate gradients, requires significant improvements in the precision at which many environmental records can be dated. In particular there have been recent attempts to build age models for radiocarbon dated sediment sequences with levels of precision normally associated with annual chronologies such as the Greenland ice cores and tree rings. These include visual wiggle match dating of terrestrial sediment records (e.g., Davies et al. 2004), regression equations applied to dated sequences after calibration, and the application of various Bayesian statistical models to both the calibration of dates (e.g. Blockley et al. 2004) and wiggle match dating (Blaauw et al. 2004). The increasing use of wiggle matching and Bayesian methods to derive both age models for climate sequences and high precision ages for isochronous tephra marker horizons (e.g., Davies et al. 2004) leads us to believe that some form of objective test of the reliability of the methods and their applicability in various contexts is timely. The three main causes of unreliability in any attempt to model radiocarbon dated sequences are 1) the reliability of the radiocarbon dates themselves; 2) the reliability of the calibration curve; and 3) the applicability of the assumptions and methodologies of the models themselves. There is a significant body of literature addressing the first two issues and methodologies have been suggested to address the quality assurance concerns surrounding radiocarbon dates (see e.g., Lowe and Walker 2000) and, at least for the Lateglacial and early Holocene, there is a calibration curve that is seen as a reasonable model for the underlying true calibration curve (See Reimer et al. 2004; Buck and Blackwell 2004). The third issue of uncertainty has been less often addressed but it is possible to test the reliability of these methods and this has been attempted in a limited number of cases (Blockely 2002, Telford et al. 2004). If we assume that the INTCAL04 calibration curve is indeed reliable for the period in question then it is possible to test any available approach by generating artificially simulated sedimentation regimes and using the calibration curve to simulate radiocarbon dates from the calendar sedimentation rates. Radiocarbon date simulation was used by Telford et al. (2004) to successfully test the use of regression equations to model sedimentation rates, which demonstrated that in most cases the number of radiocarbon dates used in age models of this type was far too small. Blockley (2002) tests the reliability of a Bayesian sequence model with a uniform prior to reconstruct changing sedimentation rates in two British Lateglacial sites. Here we adopt this approach to test methodologies that are becoming more prominent in the literature: wiggle match dating, Bayesian wiggle match dating, and Bayesian sequence modelling, which can have varying levels of constraints placed on the modelled output, depending on the assumptions of the nature of the sedimentation rate. We have constructed four scenarios, from simple to complex, that we believe are representative of the range of sedimentary regimes often encountered in dating late Quaternary records. A series of calendar ages generated for these scenarios had spacing between them of between 50 and 200 years. Once generated, they were used to simulate radiocarbon dates, using the INTCAL 04 curve. Using this approach we demonstrate that in these scenarios different


methods are most suitable for different conditions, with the wiggle match methods and highly constrained Bayesian methods being best suited to simple scenarios and the more flexible Bayesian sequence models being best suited to more complex scenarios. Furthermore, this exercise has allowed us to propose an integrated strategy that uses more than one model to allow a researcher to asses how well models are performing and to choose the best model for a given sequence. References Blockley, S.P.E. 2002. Radiocarbon Calibration and the Timing and Effects of Abrupt Late-

glacial Climate Change: Bayesian approaches to radiocarbon dated Late-glacial sequences, unpublished PhD Thesis, University of Bradford, Bradford.

Blockley, S. P. E., Lowe, J. J., Walker, M. J. C., Asioli, A., Trincardi, F., Coope, G. R., Pollard, A. M. and Donahue, R. E. 2004. Bayesian analysis of radiocarbon chronologies: examples from the European Lateglacial. Journal of Quaternary Science 19: 159-175.

Buck, C. E. and Blackwell, P. G. (2004) Formal Statistical Models for Estimating Radiocarbon Calibration Curves. Radiocarbon 46: 1093-1102.

Davies, S. M., Wohlfarth, B., Wastegård, S., Blockley, S. P. E. and Possnert, G. (2004) Were there two Borrobol Tephras in the early Late-glacial (GI-1): implications for tephrochronology? Quaternary Science Reviews 23, 581-589.

Lowe, J.J. and M.J.C. Walker. 2000. Radiocarbon dating the last glacial-interglacial transition (14C ka BP) in terrestrial and marine records: the need for new quality assurance protocols. Radiocarbon 42: 53-68.

Telford, R. J., Heegaard, E. and Birks, H. J. B. 2004. All age-depth models are wrong: but how badly? Quaternary Science Reviews 23: 1-5.

Reimer, P. J., Baillie, M. G. L., Bard, E, Bayliss, A., Beck, J., W., Bertrand, C. J. H., Blackwell, P. G., Buck, C. E., Burr, G. S., Cutler, K. B., Damon, P. E., Edwards, R. L., Fairbanks, R. G., F., M., Guilderson, T. P., Hogg, A. G., Hughen, K. A., Kromer, B., McCormac, G., Manning, S., Ramsey, C. B., Reimer, R. W., Remmele, S., Southon, J. R., Stuiver, M., Talamo, S., Taylor, F.W.; van der Plicht, J. and Weyhenmeyer, C. E. (2004) IntCal04 Terrestrial Radiocarbon Age Calibration, 0–26 Cal Kyr BP. Rdiocarbon 46: 1029-1058.


Status of the Swiss Lateglacial Tree-ring Chronologies

Klaus F. Kaiser1,2, Matthias Schaub1,2, Bernd Kromer3 and Sahra Talamo3

1Swiss Federal Research Institute WSL, Zuercherstr. 111, CH-8903 Birmensdorf, Switzerland 2Department of Geography, University of Zurich, Winterthurerstr. 190, CH-8057 Zurich,

Switzerland 3Heidelberg Academy of Sciences, INF 229, D-69120 Heidelberg, Germany

Alpine glaciers formed numerous lateral drainage channels on the Swiss plateau during the last glacial maximum approx. 23,000 cal BP. Huge melt-water floods followed the ice margins to deeper elevations. According to the ice retreat, different generations of drainage channels were formed in the vicinity of Winterthur, such as the Daettnau valley. In the vicinity of Zurich, the chain of Albis and Uetliberg as nunataks separated both ice lobes of Linth and Reuss glaciers. On both sides, the lateral meltwater outlets of Sihl and Reppisch valleys were carved into the Upper Freshwater Molasse of the Swiss Plateau. Mass movements, solifluction started to fill these channels slowly with debris and till covering the upper parts of the adjacent slopes. Permafrost still retained much of the material. These mass movements accelerated due to thawing permafrost with the climatic shift at the onset of Boelling approx. 14,500 cal BP. The geomorphic activity decelerated some 200 years later, when pioneer forests of birch and pine (Betula pubescens, Pinus sylvestris) started to establish in the shelter of these channels (14,300 cal BP) such as Daettnau, Reppisch, and Sihl valleys.

The first reforestation has been detected in the Daettnau valley. At this site up to 60 trees were excavated. A first tree-ring chronology of 20 trees and 377 years extension (DAEBØCH) represents the gradual immigration of Scots pine (Pinus sylvestris L.) (Fig.1). All the trees germinated within 32 years. Further tree finds reveal a continuous forested period that ended with early Younger Dryas. Living trees in Daettnau were gradually buried by predominantly loamy alluvia which were washed down by precipitation and melt-water. Derived from the age and the height of the tree stumps sedimentation rates of 2.5 to 5 mm prevailed during the interstadials. Scots pines form epitrophic roots but are unable to react to aggradation by building an adventitious root system. For this reason, 1 m of aggradation by these fine-grained sediments killed the trees and preserved them by sealing them hermetically. Gradually, these deposits developed into huge archives containing fossil Scots pines and other macro and micro remains. According to these sedimentation rates, tree ages mainly range between approx. 200 and 400 years.

Figure 1. Swiss lateglacial tree-ring chronologies.


In the Sihl and the Reppisch valleys the opportunity to study the Lateglacial climate further arouse. This was due to two construction sites (Gaenziloo and Landikon) of the divided highway tunnel through Uetliberg More than 140 buried subfossil pine stumps have been excavated. Their radiocarbon ages range from late Bølling throughout to Younger Dryas and finds to Preboreal. For the latter have been scattered finds only. In addition to the dendrochronological investigations, a total of 60 decadal sample segments from Gaenziloo and 21 from Landikon were analysed by high precision measurements at the Heidelberg 14C Lab. Decadal sample segments of 14C age vs. tree-ring ages were obtained. Some of the Daettnau trees have been treated the same way.

At Gaenziloo and Landikon 94 fossil pines from a total of 144 have been crossdated to three independent floating chronologies (Fig. 1):

ALLER_0 consists of 4 trees spanning 304 years of early Allerød (approx. 14,100 - 13,800 cal BP).

ALLER_1 with an excellent replication of 83 trees spans 1050 years in total, 925 of Allerød and about 125 years of YD (approx. 13,800 - 12,750 cal BP) and is evidence of even-tempered environmental conditions during most of the Allerød.

YD_A covers 212 years of early Younger Dryas (approx 12,700 - 12,480 cal BP) with a replication of 9 trees and may indicate the change to unsettled environmental conditions during this stadial.

Both chronologies from Daettnau, DAEALCH1 and DAEALCH2, have been crossdated with ALLER_1. Two fossil pines from Wiedikon, Zurich form the actual onset of the absolute pine chronology at 12,410 cal BP (Friedrich et al. 2004). With respect to the existing Lateglacial chronologies from Central Europe (Daettnau, Wiedikon and the German Preboreal Pine Chronology) the either newly built or extended chronologies close or reduce some gaps between existing chronologies. The available tree-ring series seem to bridge most of Bølling - Allerød and of the important early part of Younger Dryas.

Nevertheless between Bølling and early Allerød and in the break of Younger Dryas, between the start of the absolute chronology 12,410 cal BP, so far no reliable dendromatch can be detected. Average tree ages range between 340 to 440 years during the warmer and wetter interstadials of Bølling and Allerød yield sedimentation rates of 2.3 to 3 mm/a, while average tree ages of 140 to 200 years reveal rates of 5 to 7 mm/a during Younger Dryas. Younger Dryas is believed to be drier, but the finds attest to short intermittent wet phases. Shorter life spans of the trees as well as abundant growth irregularities result from these disruptions and corroborate this belief. Additionally, unfavourable environmental conditions impede crossdating in early Allerød and during Younger Dryas.

The analyses of the decadal samples have provided data for the new radiocarbon calibration-curve. Pollen analyses yield a shift from a birch- to a pine-dominated forest.


The Late Glacial – Early Holocene Transition in Northeast Greenland (70°-77° N): Evidence from Lake Sediments

Holger Cremer1, Bernd Wagner2, Martin Klug2 and Ole Bennike3

1Netherlands Institute of Applied Geoscience TNO – National Geological Survey, Princetonlaan 6, 3584 CB Utrecht, The Netherlands; e-mail: [email protected]

2University of Leipzig, Institute for Geophysics and Geology, Talstraβe 35, 04103 Leipzig, Germany; e-mail: [email protected]

3Geological Survey of Denmark and Greenland, Thoravej 8, 2400 Copenhagen NV, Denmark; e-mail: [email protected]

In this paper we summarize the deglaciation and early Holocene climatic and environmental history of Northeast Greenland as documented in several lacustrine sediment records recovered along the outer coast. In ice-free areas in Northeast Greenland only a few sediment records have been studied so far to unravel the environmental history of this region, although lake sediment records that extend back to the Late Pleistocene and cover the transition to the present Interglacial could provide reliable minimum dates for the deglaciation and the onset of sedimentary and biogenic accumulation.

However, the state-of-the-art of Greenland’s deglaciation history is a compilation by Bennike and Björck (2002), who summarized all known oldest dates from Greenland’s coastal regions. Most of these dates were obtained from calcareous shells and document regional minimum ages for deglaciation. The main outcome of this compilation is that secure pre-Holocene (older than 11,500 cal yr BP) deposits are not known from Northeast Greenland’s coasts. These results are confirmed by our investigations of lake sediment records between 70°-77° N (Fig. 1; Table 1). All investigated sediment sequences have sandy or diamictic layers at their basis. The oldest radiocarbon dates from above these layers vary between 10,270 and 7710 cal yr BP (Table 1) which represent the minimum deglaciation ages for Northeast Greenland. These ages imply that the visited areas were covered by glacial ice during the Last Glacial Maximum, which, however, does not disprove the conversely discussed hypothesis that parts of Northeast Greenland’s outer coast may have remained ice-free during this period (e.g., Hjort 1981).

Immediately after deglaciation low-altitude basins were inundated by the sea and accumulated marine sediments prior to their isostatic uplift above sea level (Noa Sø and Loon Lake). Higher elevated basins started to accumulate lacustrine sediments after deglaciation (Raffles


Sø, Basaltsø, Lake B1, Lake N1, Hjort Sø), but may have been affected by local glacier remnants. These remnants and delayed immigration of plants and animals most likely hampered the onset of productivity in the lakes and their vicinity during the earliest Holocene. Table 1. Oldest radiocarbon dates in lake sediment records from Northeast Greenland (70°-77° N) indicating minimum regional deglaciation ages. 1collected in fluvial sediments. 2collected in a raised marine delta.

The early Holocene environmental history of the low-altitude lakes (Noa Sø and Loon Lake) is characterized by marine and brackish sedimentation, indicated by remains of marine organisms. The transition to limnic sedimentation following the isolation of the lakes from the sea due to isostatic uplift is marked by the occurrence of diatoms, cladocera, chironomid head capsules, and elevated concentrations of organic carbon.

The high-altitude lakes document a limnic depositional environment during the early Holocene that was characterized by high opal and organic carbon concentrations and diatom assemblages of various diversity. Some of the high-altitude lakes (Basaltsø) do also show geochemical and palynological evidence for the early Holocene climatic optimum (9000 to 6500 cal yr BP) that is clearly indicated in the δ18O signature of the Renland ice core. References Bennike, O., Björck, S. (2002). Journal of Quaternary Science 17: 211-219. Bennike et al. (1999). Journal of Biogeography 26: 667-677. Björck, S. et al. (1994a). Boreas 23: 459-472. Björck, S. et al. (1994b). Boreas 23: 513-523. Cremer, H. et al. (2001). Journal of Paleolimnology 26: 67-87. Hjort, C. (1981). Boreas 10: 259-274. Wagner, B., Melles, M. (2002). Quaternary International 89: 165-176. Wagner, B. et al. (2000). Palaeogeography, Palaeoclimatology, Palaeoecology 160: 45-68.


New Results on Late Glacial Vegetation Development in Southern Denmark - Climate Oscillations and Bio-stratigraphy

Morten Fischer Mortensen

The National Museum of Denmark, Danish Prehistoric Collections & Environmental Archaeology, Ny Vestergade 11, forhuset, 1471 Copenhagen K. Denmark; e-mail:

[email protected] In Denmark, there is a long tradition for studies of lake-sedimentary records from the Late Glacial (e.g. Hartz 1902; Iversen 1942, 1954; Andersen 1980) and Denmark hosts the type-sites for the periods Allerød and Bølling. However the bio- and chrono-stratigraphy of the late Weichselian is still somewhat uncertain (de Klerk 2004). For example, it is still debated whether the type locality at Bølling contains sediments from the Bølling interstadial (e.g. Stockmarr 1974; Usinger 1985; Bennike et al. 2004). One reason for this uncertainty is that undisturbed organic sediments from this period are very rare at these latitudes. During an archeological excavation of the kettle hole site Slotseng in the southern part of Jutland, Denmark, late glacial lake sediments, up to a depth of 2 meter, were exposed, covering the entire late glacial period. This has given an opportunity for a high-resolution study of the environmental development during the Late Glacial in southwestern part of Denmark. This paper provides some preliminary results from the pollen analytical investigation and seeks to compare the results with neighboring sites. The pollen record from Slotseng shows several climatic oscillations during the Late Glacial, of which only the first warm stage so far has been 14C-dated. Both the 14C-dates and the bio-stratigraphy, which is marked by an initial rapid increase in Betula nana together with Salix, Hippophaë and Juniperus, show that this warm stage is equivalent to the Bølling interstadial. After this warm stage a change in the pollen composition towards more herbaceous plant community indicates a climate deviation. However, this is not accompanied by a decrease in the thermophilous plants, leading to an interpretation of changes in winter temperature and/or precipitation instead of a change in summer temperature. A second climate advance at the beginning of the Allerød interstadial leads to a rapid expansion of tree Betula and a replacement of the open herbaceous vegetation with an open Betula forest. During this period two intermittent decreases in Betula are recorded. The second decrease is the most pronounced and is followed by a rise in Pinus pollen. With the onset of the Younger Dryas the forest retreats from the area being replaced by a more open and patchy vegetation. During the last part of the Younger Dryas the expansion of Empetrum and Juniperus is very distinct. The transition to the Holocene is marked by an increase of tree Betula the rapidity of which suggests that tree Birch may have been present in the area during at least the later part of the Younger Dryas period. The main trends in the bio-stratigraphy are comparable to records from Schleswig-Holstein (Usinger 1985), Vorpommeren (de Klerk 2002) and from The Netherlands (Hoek 1997). Slotseng is a key locality in the history of human immigration to the Danish area, because it contains bones and antlers from reindeer’s slaughtered by Palaeolithic hunters. These are the earliest, unambiguous evidence of human activity in Denmark (12400-12150 14C BP), yet to be found. Besides the archaeological value, Slotseng is of great interest because the biostratigraphy shows the environmental development in the southwestern Denmark during the early part of the Late Weichselian. References Andersen, S. TH. 1980. Early and Late Weichselian chronology and birch assemblages in

Denmark. Boreas 9: 53-69.


Bennike, O., Sarmaja-Korjonen, K., Seppänen, A. 2004. Reinvestigation of the classic lateglacial Bølling Sø sequence, Denmark: chronology, macrofossil, Cladocera and chydorid ephippia. Journal of Quaternary Science 19(5): 465-478

de Klerk, P. 2002. Changing vegetation patterns in the Endinger Bruch area (Vorpommern, NE Germany) during the Weichselian Lateglacial and Early Holocene. Review of Palaeobotany and Palynology 119: 275-309

de Klerk, P. 2004. Confusing concepts in Lateglacial stratigraphy and geochronology: origin, consequences, conclusions (with special emphasis on the type locality Bøllingsø). Review of Palaeobotany and Palynology 129: 265-298.

Hartz, N. 1902. Bidrag til Danmarks senglaciale Flora og Fauna. Dan. Geol. Unders. 2. Række 11, 1-80.

Hoek, W. Z. 2001. Vegetation response to the ~14.7 and ~11.5 ka cal. BP climate transitions: is vegetation lagging climate? Global and Planetary Change 30:103-115.

Iversen, J. 1942. En pollenanalytisk Tidsfæstelse af Ferskvandslagene ved Nørre Lyngby. Medd. Fra Dansk Geol. Forening. København bd. 10: 130-151.

Iversen, J. 1954. The late-glacial flora of Denmark and its relation to climate and soil. Dan. Geol. Unders 2 Række 80; 87-119.

Stockmarr, J. 1974. Biostratigraphic studies in Late Weichselian sediments near Bøllingsø. Danmarks Geologiske Undersøgelser. Aarbog 1975: 71-89.

Usinger. 1985. Pollenstratigraphischer, vegetations-und klimageschichtliche Gliederung des ‘‘Bølling-Allerød Komplexes’’ in Schleswig-Holstein und ihre Bedeutung für die Spätglazial-Stratigraphie in benachbarten Gebieten. Flora (177): 1-43.


Rapid Climatic Events as Recorded in Middle Weichselian Thermokarst Lake Sediments

Stefan Engels, S.J.P. Bohncke, J.A.A. Bos, O. Heiri and C. Kasse

Department of Quaternary Geology and Geomorphology, Faculty of Earth and Life Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1085, NL-1081 Amsterdam, The Netherlands

There are several factors that can trigger the formation of thermokarst lakes: formation of a thaw lake can be caused by an external factor such as a change in climate, or by an intrinsic mechanism such as a natural fire or erosion by river cut banks. If thermokarst initiation is triggered by climate warming, then evidence of such a thermal spike should be present in especially the lower parts of the thermokarst infilling. Given the short duration of the Pleniglacial warm spikes in the ice core record, one may assume that the bulk of the thermokarst infilling might already represent the waning stage of the thermal spike and the development towards a succeeding cold phase. A 30-cm thick thermokarst lake deposit was retrieved from the Niederlausitz area, eastern Germany, and dated using the AMS 14C-method to an age of approximately the early Middle Weichselian. To test if this thaw lake was formed as a result of an external or an internal forcing mechanism, the thermokarst infilling is analysed for temperature- dependent proxies such as aquatic plant species and chironomids. First, paleotemperature estimates are made based on botanical taxa by using the climate indicator plant species method (sensu Iversen, 1944). Several thermophilous aquatic plant species are known to migrate relatively quickly, are independent of soil formation and can thus react quickly to climate warming. Second, chironomids are used to qualitatively reconstruct paleotemperatures. A canonical correspondence analysis (CCA) constrained by a single environmental variable (mean July air temperature (Tjul)) is performed. 40 Shallow lakes from the Swiss Alps are used as a training set. In the lower parts of the sequence, pollen of thermophilous taxa such as Nymphaea alba, Frangula alnus, Typha angustifolia and fruits of Potamogeton mucronatus indicate mean summer temperatures between 12-14 ºC. At approximately 31 cm core depth, several thermophilous taxa disappear, but remaining taxa such as Ranunculus subgen. Batrachium indicate a Tjul of at least 10 ºC. The uppermost samples show a more open landscape with increased surface erosion, with summer temperatures that are probably around 10 ºC. The fossil chironomid-assemblages show high reconstructed temperatures for the lower part of the sequence. At 12 cm core depth, a sharp decrease in relative temperature occurs, concurrent with the change to a more open landscape as suggested by the botanical analyses. Both the botanical and the zoological indicators suggest temperature as an external forcing mechanism during the formation of the lake. July air temperatures of at least 10 ºC, but probably higher, must have prevailed during the largest part of the infill but at the end of the sequence a sharp decline in Tjul can be seen.


Lateglacial Palaeovegetation Records - Key Sites of Lithuania

Petras Sinkunas, Migle Stancikaite and Dalia Kisieliene Department of Quaternary Research, Institute of Geology and Geography, Sevcenkos 13, LT-

03223, Vilnius, Lithuania; e-mail: [email protected], [email protected], [email protected]

Situated within the marginal area of the ice sheet of Last Fenoscandian (Weichselian) Glaciation the sediment archives of the Lateglacial environment in territory of Lithuania are quite representative. Albeit the Lateglacial survey has long lasting tradition the most relevant sites representing the Last Glacial – Interglacial Transition in Lithuania are investigated only recently and need to be compared inter-regionally. A continuous record encompassing whole Last Interglacial/Glacial cycle was obtained from the Medininkai site located outside the maximum limit of Last Glaciation in eastern Lithuania. Sediments are correlated to Brörup, Odderade, Hengelo (U/Th - 42 kyr BP) and Denekamp interstadials (Satkunas et al., 2003). Accumulation of this sediment sequence under the alternating periglacial and interstadial palaeoenvironments from Eemian Interglacial continued to Lateglacial and Holocene, however the Last Glacial – Interglacial Transition is poorly presented. During the last years a new data set discussing the Lateglacial environmental changes was collected in eastern Lithuania (Blazauskas et al., 1998; Stancikaite et al., 1998, 2002). Detailed description of the Lateglacial environment has been attempted through an interpretation of pollen and plant macro remain data from Rudnia, Kriokslys, Zervynos and Pamerkiai sequences with 14C chronologies. However the temporal resolution of these records is not sufficient enough for inter-regional correlation in most cases. Further more the earliest periods of the Late Glacial e.g. correlated to the Oldest Dryas, Bølling and Older Dryas biozones are lacking or scarcely represented in most of the above mentioned cores. Recently the Lateglacial sediment sequences dated back to pre−Allerød were investigated in northern (Lieporiai) and western (Kasuciai) Lithuania. Best dated and most representative is the core from Kasuciai site, which presents an uninterrupted sediment sequence from about 15 ka 14C yr BP (15450 ± 250 BP, Ki-10914) up to the end of the Last Termination. Palaeobotanically all the vegetation zones correlated to entire interval from Bølling to the Preborial are represented (Fig. 1). The Lateglacial Interstadial is defined by the dominance of Characeae and higher concentration of calcium carbonate in sediments that points to an amelioration of climate. The earlier stage of pre-Allerød (Bølling biozone) is characterised by the pioneer taxa (Artemisia, Chenopodiaceae and Salix) and the communities of open habitats (with Asteraceae, Thalictrum, Caryophyllaceae, Betula nana, etc.). During the later stage of the Interstadial (Allerød biozone) the light demanding taxa was replaced by pine reflecting the development of a closer woodland habitat and dryness of climate. The short period with increased Betula representation and increased number of plants typical of the eroded habitats is recorded between the Bølling and Allerød biozones and could be correlated to the Older Dryas biozone.


Figure 1. Biplot of principal component analysis (PCA) for pollen samples at Kasuciai site. The onset of the Younger Dryas biozone is marked by drop of the AP species (Betula had exchanged Pinus) and increase of heliophytic herbs. The end of the Younger Dryas biozone reflects a restoration of the vegetation cover and contemporaneous expansion of Pinus with the earliest establishment of Picea sp. (needles), Betula nana L., Alnus glutinosa (L.) Gaertn, Alnus incana (L.) Moench. A sharp rise in pollen concentration documents formation of continuous vegetation cover during the Preboreal biozone. Lithuanian State Science and Studies Foundation supported this research, including the projects V-05033 and V-05069. References Blazauskas, N., Kisieliene, D., Kucinskaite, V., Stancikaite, M., Seiriene, V., Sinkunas, P.,

1998. Late Glacial and Holocene sedimentary environment in the region of the Ula River. Geologija, 25, 20-30.

Satkunas, J., Grigienė, A., Velichkevich, F., Robertsson, A.-M., Sandgren, P., 2003. Upper Pleistocene stratigraphy at the Medininkai site, eastern Lithuania: a continuous record of the Eemian-Weichselian sequence. Boreas, 32, 627-641.

Stancikaite, M., Kabailiene, M., Ostrauskas, T. and Guobyte, R., 2002. Environment and man in the vicinity of Lakes Dūba and Pelesa, SE Lithuania, during the Late Glacial and Holocene. Geological Quarterly, 46, 391-409.

Stancikaite, M., Seiriene, V., Sinkunas, P., 1998. The new results of Pamerkys outcrop investigations, South Lithuania. Geologija, 23, 77-88.


Examining Evidence for Solar Forcing of Climate c. 2800 cal BP with the Aid of Distal Tephras

Gill Plunkett and Graeme Swindles

School of Geography, Archaeology & Palaeoecology, Queen's University Belfast, Belfast BT7 1NN, Northern Ireland

Reduced solar activity, inferred from the 14C calibration curve, between 2800 and 2710 cal BP has been evoked as a forcing mechanism to explain evidence for simultaneous, widespread environmental change in the northern and southern hemispheres (e.g. van Geel et al. 1996, 2000; Kilian et al. 2000; Speranza et al. 2000; Blaauw et al. 2004). The dating of climate events around this time, however, is frequently hampered by the occurrence of an extended 14C plateau at 2710-2400 cal BP that can smear the calibrated age of observed phenomena unless 14C determinations are very refined. Consequently, there is a danger that all climate shifts around 2750 cal. BP will be attributed to a single ‘event’. Reconstructions of bog surface wetness using peat humification analysis on seven sites in Ireland suggests that, unlike neighbouring areas on continental Europe, the period of reduced solar activity at 2800 cal. BP was associated not with a shift to increased wetness/coldness but instead with drier conditions (Plunkett, in press). A shift to wetter bog surfaces is observed, however, at c. 2690 cal BP. The timing of this change is bracketed by the deposition of two distal tephras, the GB4-150 and the Microlite, that are dated by high-precision 14C wiggle-matching to 2750-2708 cal BP and 2705-2630 cal BP, respectively (Plunkett et al. 2004). These age constraints indicate that the wet shift in Irish bogs occurred around the end of the 14C anomaly and confirm that it is not synchronous with the 2800 cal BP 'event' recorded elsewhere. The quantitative reconstruction of bog water tables at one of the sites using a testate amoebae transfer function-approach (Swindles, in prep.) suggests that a rapid rise in water tables is in phase with the humification results. These findings call into question the hypothesised effects of solar forcing at this time. It is not yet clear if Ireland experienced a divergent climate response to such forcing at c. 2800 cal BP, if there is a delay in the response of the climate system in this region such that adverse conditions are offset for approximately a century, or indeed if solar forcing played any part in climate change at this time. The discrepancy in the evidence from oceanic and continental Europe offers an opportunity to assess critically the possible mechanisms by which solar output is thought to impact on climate, including its potential influence on North Atlantic Thermohaline Circulation patterns. The tephra horizons, at least one of which (Microlite) has been reported from Germany (van den Bogaard et al. 2002) and Scotland (Langdon & Barber 2001), comprise invaluable time parallel markers that may enable climate responses elsewhere on the north Atlantic fringe to be scrutinised in a similar manner. References Blaauw, M., van Geel, B. & van der Plicht, J. 2004 Solar forcing of climatic change during

the mid-Holocene: indications from raised bogs in The Netherlands. The Holocene 14, 35-44.

Kilian, M.R., van Geel, B. & van der Plicht, J. 2000 14C AMS wiggle matching of raised bog deposits and models of peat accumulation. Quaternary Science Reviews 19, 1011-1033.

Langdon, P.G. & Barber, K.E. 2001 New Holocene tephras and a proxy climate record from a blanket mire in northern Skye, Scotland. Journal of Quaternary Science 16, 753-759.

Plunkett, G. (in press) Tephra-linked peat humification records from Irish ombrotrophic bogs question nature of solar forcing at 850 cal. BC. Journal of Quaternary Science.


Plunkett, G.M., Pilcher, J.R., McCormac, F.G. & Hall, V.A. 2004 New dates for first millennium BC tephra isochrones in Ireland. The Holocene 14, 780-786.

Speranza, A., van Geel, B. & van der Plicht, J. 2002 Evidence for solar forcing of climate change at ca. 850 cal BC from a Czech peat sequence. Global and Planetary Change 35, 51-65.

van den Bogaard, C., Dörfler, W., Sandgren, P. & Schmincke, H.-U. 1994 Correlating the Holocene records: Icelandic tephra found in Schleswig-Holstein (northern Germany). Naturwissenschaften 81, 554-556.

van Geel, B., Buurman, J. & Waterbolk, H.T. 1996 Archaeological and palaeoecological indications of an abrupt climate change in The Netherlands, and evidence for climatological teleconnections around 2650 BP. Journal of Quaternary Science 11, 451-460.

van Geel, B., Heusser, C.J., Renssen, H. & Schuurmans, C.J.E. 2000 Climatic change in Chile at around 2700 BP and global evidence for solar forcing: a hypothesis. The Holocene 10, 659-664.


Lateglacial Tephra Stratigraphy and Climate Related Events on the North Icelandic Shelf

Jón Eiríksson1, Gudrún Larsen1, Karen Luise Knudsen2, Leifur A. Símonarson1, Louise

Pallisgaard Ghysels2,4 ,Mette K.B. Søndergaard2 and Jan Heinemeier3 1Earth Science Institute, University of Iceland, Reykjavík, Iceland

2Department of Earth Sciences, University of Aarhus, Denmark 3The AMS 14C Centre, Institute of Physics and Astronomy, University of Aarhus, Denmark

4Bjerknes Centre for Climate Research, University of Bergen, Norway

The Lateglacial palaeoceanographic record from North Iceland shows that the ocean circulation did change dramatically during this period. The variability is reflected in benthic and planktonic foraminifera, stable isotopes, diatom-based sea surface temperature reconstructions and in sedimentological parameters, including ice rafted debris. Oceanographically, the North Icelandic shelf is a boundary region between surface water masses derived from the cold East Greenland Current and the warmer Irminger Current that generally forms a clockwise gyre around Iceland. The bottom circulation is not well known in details, but the deeper part of the shelf is most probably affected by North Atlantic Deep Water flowing southward from the Nordic Seas. On an east-west transect between Greenland and NW-Europe, the North Icelandic shelf has an intermediate position being distal to both the large ice caps of Greenland and Scandinavia. A detailed study of past oceanographic fluctuations in this region is expected to reflect variable strength of the Nordic Seas heat pump and give information about palaeoatmospheric processes. Work on the tephra stratigraphy on the North Icelandic Shelf is in progress and may contribute to the assessment of the timing of regional climatic changes in the North Atlantic area. Reliably correlated and well dated tephra markers are expected to facilitate correlation and regional comparison of events in data archives containing oceanographic, atmospheric and terrestrial records. Major element geochemistry has been used to identify several Lateglacial and Early Holocene tephras, including the Saksunarvatn ash, the “S” layer from Askja, the Vedde Ash, and the Borrobol Tephra. The tephra stratigraphic work is carried out parallel to AMS 14C dating of molluscs and foraminifera, both in order to investigate the absolute chronology of the records and to establish reservoir age variability during the Lateglacial. Methods for the differentiation of primary tephra deposits from reworked material in relatively shallow marine settings are discussed. This is a problem, which is particularly acute in sedimentary basins proximal to the source volcanoes where not only the tephras, but also the background material is of volcaniclastic origin.


Palaeoceanographic Changes through GS2, GI-1, GS-1 and the Early Holocene off North Iceland

Karen Luise Knudsen1, Jón Eiríksson2, Louise Pallisgaard Ghysels1,3, Mette K.B.

Søndergaard1, Hui Jiang4 and Jan Heinemeier5 1Department of Earth Sciences, University of Aarhus, Denmark

2Earth Science Institute, University of Iceland, Reykjavík, Iceland 3Bjerknes Centre for Climate Research, University of Bergen, Norway

4State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai, P.R. China

5The AMS 14C Centre, Institute of Physics and Astronomy, University of Aarhus, Denmark

Strong climatic gradients between the Arctic and the North Atlantic realms traverse the North Icelandic shelf, enhancing the significance of this as a key area for the study of the regional oceanographic variability through the Lateglacial and the Early Holocene. The shelf is located in a sensitive boundary region between Atlantic water, which is brought to the area by the relatively warm, high-salinity Irminger Current, and cold, low-salinity surface water of the East Icelandic Current. The Arctic water mass of the East Icelandic Current derives partly from the East Greenland Current (Polar water) and partly from westerly eddies of the Norwegian Atlantic Current (the Jan Mayen Gyre). The strength of the North Atlantic Current is generally related to deep water formation in the Nordic Seas, which is again associated with southward overflow across the Greenland-Iceland-Faeroe-Scotland Ridge. The North Atlantic Current is expected to be strong during active deep water formation, and weak during periods of freshening of the surface waters north of Iceland, i.e. during periods with strong input of Polar water from the East Greenland Current and the East Icelandic Current. During periods of strong overflow in the Denmark Strait and across the Iceland-Faeroe Ridge, the cold Norwegian Sea Deep Water (NSDW) may be expected to influence the topographic basins north of Iceland. At present, the NSDW replaces the mixed surface water masses at about 300-400 m depth on the North Icelandic shelf. A combined study of foraminifera, stable isotopes, diatoms and sedimentology in marine sediment cores from about 400 m water depth on the North Icelandic shelf records major changes both in sea surface and sea floor conditions during the deglaciation and the Early Holocene. The chronostratigraphy is based on a combination of well-known tephra markers and a series of AMS 14C dates, and the record is discussed in terms of the Greenland ice-core events. The record includes the interval from GS-2 (pre-Bølling) through GI-1 (Bølling-Allerød), GS-1 (Younger Dryas) and the Preboreal. The presentation will focus on problems with the determination of the GS-1 event (Younger Dryas) in the area. The event boundaries are difficult to determine due to radiocarbon plateau problems, marine reservoir age problems, lack of well defined tephra layers between the Vedde and the Saksunarvatn tephras, and additionally to the fact that GS-1 is not particularly well-defined as a cold interval in the area.


Oceanic Surface Conditions on the West Spitsbergen Continental Margin during the last 15,000 Years

Morten Hald, Hanne Ebbesen and Trond Henrik Lie-Andreassen

Department of Geology, University of Tromsoe, Norway; e-mail: [email protected] A study of planktic foraminifera, their isotopic composition and ice rafted debris has been done using a marine sediment core from the continental margin west of Spitsbergen. The study records oceanographic changes during the last c. 15,000 calendar years BP. During the later part of the deglaciation the area was exposed to an increased content of ice rafted debris (14.8-13.9 cal ka BP) caused by a retreat of glaciers on Spitsbergen. This event can be correlated to several records in the North Atlantic region. During the Younger Dryas the continental margin off Spitsbergen was characterized by an increase in the sea ice cover. The transition from a cold oceanographic mode during the Younger Dryas to a warm stable Holocene was characterized by rapid fluctuations in planktic species and sea surface temperatures, which is interpreted to reflect shifts between relatively warm Atlantic Water and cold Arctic Water. A similar instability has been traced in other marine records from the northeastern North Atlantic, and thus apparently characteristic for the transition between cold and warm states in this region. A Holocene climatic optimum occurred from 10.5-8.8 cal ka BP, where the West Spitsbergen Current strengthened and sea surface temperatures exceeded modern temperatures with >3oC. At 8.8 cal ka BP the West Spitsbergen Current weakened again and colder Arctic Water became the dominant oceanographic regime west of Spitsbergen. This regime seemed to continue during the remaining part of the Holocene. The source for the Arctic Water could be from the Arctic Ocean, north of Spitsbergen.


Lake Suigetsu Update: Correlation Between “SG vyr BP” and “IntCal-04 cal BP” (2005 Temporary Version), and Two Different Types of Forcing to the Deglacial Climate

Changes

Takeshi Nakagawa1, Hiroyuki Kitagawa2 and Yoshinori Yasuda3 1Department of Geography, University of Newcastle: Newcastle upon Tyne, NE1 7RU, England,

UK 2Department of Earth and Environmental Science, Nagoya University: Furo-cho, Chikusa-ku,

Nagoya, 464-8601, Japan 3International Research Center for Japanese Studies: Oeyama-cho, Goryo, Nishikyo-ku, Kyoto,

610-1192, Japan Revision on the Cariaco marine reservoir age beyond ca. 12,900 cal BP, based on a newly established floating Greman pine tree ring chronology (Kromer, INTIMATE 2004 Bonn; Kromer et al., 2004 Radiocarbon), gave a “deep impact” on the Suigetsu late glacial (ca. 10-16 ka) event stratigraphy. Suigetsu palaeoclimate curves were correlated to Cariaco profiles using independent varve chronologies, and the consistency of the two chronologies had been supported by overall matching of 14C age wiggles. However, the newly detected change in Cariaco marine reservoir age (if it is real) makes this support invalid. Because Suigetsu 14C dates were all measured on terrestrial leaf fossils, there is no room for the reservoir age to play an important role. Instead, in order to re-establish good agreement of 14C wiggles between Suigetsu chronology and IntCal-04 Chronology (in other words, in order to establish transfer function between “SG vyr BP” and “cal. BP”), we performed Monte-Carlo simulation by varying only two parameters: (i) anchoring point of the floating chronology, and (ii) counting error rate. The results implied about 5 % of regular miss-counting in Suigetsu varve chronology (more precise formula would be provided in the presentation). After revising the correlation strategy, the lag and lead of millennial scale climate events between N. Atlantic and Japan persisted. In contrast, more spiky climate oscillations in the N. Atlantic (GS-1b, OD and GS-1d), which didn’t have clearly recognized counterparts in Suigetsu event stratigraphy (Nakagawa et al., 2003; 2004), suddenly became synchronous to one of minor peaks in Suigetsu pollen/climate curves (those minor peaks are more numerous in Suigetsu than in the N. Atlantic). Adding to this, most of those centennial peaks in Suigetsu pollen/climate signals chronologically coincide with peaks in ∆14C wiggles in the IntCal-04. This implies the presence of pan-hemispheric climate forcing (such as solar changes) behind the centennial scale deglacial climate oscillations. Finally, possible linkage between Suigetsu centennial pollen/climate curves, solar cyclicity at 208 years and Bond events will be also discussed.


Contrasting Late-glacial and Early Holocene Climate Shifts in South-central Alaska: Stable Isotope Record from Lacustrine Carbonate

Zicheng Yu1, Edward B. Evenson1, Karina N. Walker1 and Irka Hajdas2

1Department of Earth and Environmental sciences, Lehigh University, 31 Williams Drive, Bethlehem, PA 18015, USA; e-mail: [email protected]

2ETH Hoenggerberg HPK H 27, 8093 Zurich, Switzerland Lithology, stable-isotope and pollen data from two cores at Hundred Mile Lake (HML; 61.808°N, 147.842°W, elevation = 506.3 m) in the Matanuska Valley of south-central Alaska were used to investigate climate and vegetation change over the last 13,500 cal years. The chronology of the sediment cores was controlled by six AMS dates – one on organic-rich sediment, one on a terrestrial macrofossil and four on Pisidium mollusk shells. The 14C dates on shells were corrected for the “old carbon effect” based on offset between macrofossil and shell dates at the same horizon, and all dates were calibrated using IntCal98 calibration dataset. An age model was developed based on linear interpolation of five accepted dates. Sediment lithology of the cores changes from clay at ~15-13.5 ka (1 ka = 1,000 cal BP), through marl at 13.5-8 ka, to gyttja at 8-0 ka. The transition from clay to marl suggests increased productivity of the lake in a stabilizing watershed, induced probably by initial warming after ice retreat. The change from marl to gyttja suggests a climate shift to cool and wet conditions in the mid-Holocene, consistent with other regional records. The δ18O record obtained from Pisidium mollusk shells from HML shows several large shifts between 13.5 and 8 ka. A negative excursion of ~2‰ in δ18O occurred at 12.4-11.4 ka, probably a regional expression of the Younger Dryas (YD) cooling event. A 4.5‰ negative shift occurred around 10.5 ka (from -10.5‰ at 13.5–11 ka to -15‰ at 10–8 ka). This surprisingly large and dramatic shift in δ18O values in the early Holocene suggests a major change in atmospheric circulation patterns, which has not been documented elsewhere in the region. Possible causes of this isotopic shift include a change in precipitation seasonality, a shift in regional wind directions, and a change in precipitation source regions modulated by retreating ice sheets/glaciers. Pollen results from marl sediments at HML indicate vegetation change from a herb tundra, through shrub birch-dominated tundra, to an alder forest. Regional vegetation around HML closely follows other regional pollen diagrams for south-central Alaska, but does not appear to follow climate shifts closely. The data from this study suggest that the climatic shift in the region during the early Holocene was more abrupt and in greater magnitude than the YD event. This implies a differential regional response in south-central Alaska to large-scale climate forcing, possibly caused by the stronger regional feedback processes in high latitudes.


Rapid Climate Changes in the North Atlantic Region during the Last Termination: Were They Really Synchronous?

Hans Renssen

Faculty of Earth and Life Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1085, NL-1081 Amsterdam, The Netherlands; e-mail: [email protected]

Within the framework of INTIMATE, the Greenland ice-core oxygen isotope record has been used to set up an event stratigraphy for the last termination in the North Atlantic region (Björck et al. 1998). The underlying idea is that the rapid climatic changes (or events) that occurred during the last deglaciation were synchronous throughout the North Atlantic region and that these events could thus be used for correlation between different locations in this region. However, uncertainties in dating techniques make it difficult to check if the events were really synchronous or, alternatively, that time lags occurred between rapid climate changes at various sites in the North Atlantic region. We address this issue by analysing surface temperatures from a climate model simulation of the 8.2 kyr BP event, thereby assuming that the controlling mechanism (i.e. fluctuations in the strength of the thermohaline circulation) is the same as for the events during the last termination. In our simulation, a climate state in equilibrium with early Holocene boundary conditions (8.5 kyr BP) was perturbed by releasing a freshwater pulse into the Labrador Sea (Renssen et al., 2001, 2002). The amount of freshwater is based on geological constraints. As a result of this freshwater pulse, the deepwater formation in the Nordic Seas (just South of Svalbard) collapses during about 300 years. The simulated climate anomaly is in good agreement with proxy evidence for the 8.2 kyr BP event, with pronounced cooling in the North Atlantic region and relatively dry conditions over Greenland and monsoonal domains (Wiersma and Renssen, in press). To see if the rapid climate changes are synchronous in our experiment, we compare the simulated time-series for surface temperature over Greenland, with similar time-series over northwestern Europe, Iceland, Svalbard and North America (Fig. 1 next page). We find that the temperature changes over northwestern Europe and North America are more or less simultaneous with the changes over Greenland. However, the temperature response over Greenland is not fully synchronous with the response over the Nordic Seas, as the start of the cooling over Greenland lags the response over Svalbard by 30 years and the cooling over Iceland by 10 years. Similarly, the rapid warming at the end of the event starts 20 years earlier over Svalbard than over Greenland. These time lags are due to reorganisations of the ocean circulation in the Nordic Seas, which have dissimilar effects at different locations. Our comparison of simulated temperature time-series suggests that we should be careful with using events that are registered in the Greenland ice-core records for correlation purposes throughout the North Atlantic region. References Björck, S. et al., 1998. An event stratigraphy for the Last Termination in the North Atlantic

region based on the Greenland ice-core record: a proposal by the INTIMATE group. Journal of Quaternary Science, 13(4): 283-292.

Renssen, H., Goosse, H. and Fichefet, T., 2002. Modeling the effect of freshwater pulses on the early Holocene climate: the influence of high frequency climate variability. Paleoceanography, 17(2): 1020, DOI 10.1029/2001PA000649.

Renssen, H., Goosse, H., Fichefet, T. and Campin, J.-M., 2001. The 8.2 kyr BP event simulated by a global atmosphere–sea-ice–ocean model. Geophysical Research


Letters, 28: 567-570. Wiersma, A.P. and Renssen, H., in press. Model-data comparison for the 8.2 ka BP event:

confirmation of a forcing mechanism by catastrophic drainage of Laurentide Lakes. Quaternary Science Reviews (in press).

Figure 1: Simulated time-series of annual mean surface temperature over Greenland (black curves and left y-axis) and NW Europe, N America, Svalbard and Iceland (grey curves and right y-axis). The first 55 years represent the climate in equilibrium with boundary conditions for 8.5 kyr BP and the black arrow marks the timing of the freshwater pulse. The dotted lines indicate the start and end of the cold anomaly over Greenland.

Surface temperature Greenland and NW Europe

-25

-23

-21

-19

-17

-15

-13

0 50 100 150 200 250 300 350 400 450Time (yr)

°C

6

7

8

9

10

11

12

13

14

°C

Greenland NW Europe

freshwater pulse

Surface temperature Greenland and Iceland

-25

-23

-21

-19

-17

-15

-13

0 50 100 150 200 250 300 350 400 450Time (yr)

°C

-20

-15

-10

-5

0

5

10

°C

Greenland Iceland

freshwater pulse

Surface temperature Greenland and Svalbard

-25

-23

-21

-19

-17

-15

-13

0 50 100 150 200 250 300 350 400 450Time (yr)

°C

-60

-50

-40

-30

-20

-10

0

°C

Greenland Svalbard

freshwater pulse

Surface temperature Greenland and N America

-25

-23

-21

-19

-17

-15

-13

0 50 100 150 200 250 300 350 400 450Time (yr)

°C

-4

-3

-2

-1

0

1

2

3

4

5

6

°C

Greenland N America

freshwater pulse


List of Participants Andersen, Katrine Kroch The Copenhagen Ice Core Dating Initiative and the NGRIP Chemistry Group, Ice and Climate Research, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen Oe, Denmark; e-mail: [email protected] Blockey, Simon Peter Research Laboratory for Archaeology, University of Oxford, 6 Keble Road, Oxford, UK; e-mail: [email protected] Bohncke, Siardus Department of Quaternary Geology and Geomorphology, Faculty of Earth and Life Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1085, NL-1081 Amsterdam, The Netherlands; e-mail: [email protected] Bos, Johanna Department of Quaternary Geology and Geomorphology, Faculty of Earth and Life Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1085, NL-1081 Amsterdam, The Netherlands; e-mail: [email protected] Cremer, Holger Netherlands Institute of Applied Geoscience TNO – National Geological Survey, Princetonlaan 6, 3584 CB Utrecht, The Netherlands; e-mail: [email protected] Davies, Siwan Manon Department of Geography, Swansea University, Singleton Park, Swansea, SA2 8PP, UK; e-mail: [email protected] Eiríksson, Jón Earth Science Institute, University of Iceland, Reykjavík, Iceland; e-mail: [email protected] Engels, Stefan Department of Quaternary Geology and Geomorphology, Faculty of Earth and Life Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1085, NL-1081 Amsterdam, The Netherlands; e-mail: [email protected] Hald, Morten Department of Geology, University of Tromsoe, Norway; e-mail: [email protected] Heinemeier, Jan The AMS 14C Centre, Institute of Physics and Astronomy, University of Aarhus, Denmark; e-mail: [email protected] Hoek, Wim Utrecht University, Department of Physical Geography, Faculty of Geosciences, Heidelberglaan 2, 3508 TC Utrecht, The Netherlands; email: [email protected]


Johnsen, Sigfús The Copenhagen Ice Core Dating Initiative and the NGRIP Chemistry Group, Ice and Climate Research, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen Ø, Denmark; e-mail: [email protected] Kaiser, Klaus Felix Swiss Federal Research Institute WSL, Zuercherstr. 111, CH-8903 Birmensdorf, Switzerland; e-mail: [email protected] Knudsen, Karen-Luise Department of Earth Sciences, University of Aarhus, Denmark; e-mail: [email protected] Lane, Christine Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK; e-mail: [email protected] Lowe, John Centre for Quaternary Research, Department of Geography, The Royal Holloway University of London Egham Surrey TW20 OEX, England; e-mail: [email protected] Mangerud, Jan Department of Geoscience, University of Bergen, Allégt. 41, N-5007 Norway; e-mail: [email protected] Mortensen, Morten Fischer The National Museum of Denmark, Danish Prehistoric Collections & Environmental Archaeology, Ny Vestergade 11, forhuset, 1471 Copenhagen K. Denmark; e-mail: [email protected] Nakagawa, Takeshi Department of Geography, University of Newcastle: Newcastle upon Tyne, NE1 7RU, England, UK; e-mail: [email protected] Newnham, Rewi School of Geography, University of Plymouth, Plymouth PL4 8AA, UK; e-mail: [email protected] Noe-Nygaard, Nanna Geological Institute, Copenhagen University, Østervoldgade 10, 1350 K Copenhagen, Denmark; e-mail: [email protected] Plunkett, Gill School of Geography, Archaeology & Palaeoecology, Queen's University Belfast, Belfast BT7 1NN, Northern Ireland; e-mail: [email protected] Pollard, A. Mark Research Laboratory for Archaeology, University of Oxford, 6 Keble Road Oxford, UK; e-mail: [email protected]


Pyne-O'Donnell, Sean Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK; e-mail: S.Pyne-O'[email protected] Ramsey, Christopher Bronk Research Laboratory for Archaeology, University of Oxford, 6 Keble Road, Oxford OX1 2JD, UK; e-mail: [email protected] Renssen, Hans Faculty of Earth and Life Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1085, NL-1081 Amsterdam, The Netherlands; e-mail: [email protected] Sinkunas, Petras Department of Quaternary Research, Institute of Geology and Geography, Sevcenkos 13, LT-03223, Vilnius, Lithuania; e-mail: [email protected] Yu, Zicheng Department of Earth and Environmental Sciences, Lehigh University, 31 Williams Drive, Bethlehem, PA 18015, USA; e-mail: [email protected]

Documents

The North Atlantic INTIMATE Project · INTegrating Icecore, MArine and TErrestrial records in the North Atlantic Region A Core Project of the INQUA Palaeoclimate Commission Project