Vedde Ash Research Articles

Volcanic ash layers from the Last Glacial Termination in the NGRIP ice core

AbstractThe tephrochronological record of the 1400–1640 m depth (∼10 000–16 000 calendar ice core years before present) of the NGRIP ice core has been established by particle screening of selected samples. Ash was identified in 20 samples. Correlation with ice, marine and terrestrial records from volcanic source regions in the northern hemisphere positively identifies the Saksunarvatn Ash and the Vedde Ash (Ash Zone 1). Major element chemistry of the remaining identified ash layers mainly points towards an Icelandic origin. This tephrochronological record provides new important marker horizons for correlating the timing of the climatic changes associated with the Last Glacial Termination within the North Atlantic region, as well as outlining more details concerning the frequency and composition of volcanic eruptions occurring at this deglaciation. Copyright © 2005 John Wiley & Sons, Ltd.

Calendar year age estimates of Allerød–Younger Dryas sea‐level oscillations at Os, western Norway

AbstractA detailed shoreline displacement curve documents the Younger Dryas transgression in western Norway. The relative sea‐level rise was more than 9 m in an area which subsequently experienced an emergence of almost 60 m. The sea‐level curve is based on the stratigraphy of six isolation basins with bedrock thresholds. Effort has been made to establish an accurate chronology using a calendar year time‐scale by 14C wiggle matching and the use of time synchronic markers (the Vedde Ash Bed and the post‐glacial rise in Betula (birch) pollen). The sea‐level curve demonstrates that the Younger Dryas transgression started close to the Allerød–Younger Dryas transition and that the high stand was reached only 200 yr before the Younger Dryas–Holocene boundary. The sea level remained at the high stand for about 300 yr and 100 yr into Holocene it started to fall rapidly.The peak of the Younger Dryas transgression occurred simultaneously with the maximum extent of the ice‐sheet readvance in the area. Our results support earlier geophysical modelling concluding a causal relationship between the Younger Dryas glacier advance and Younger Dryas transgression in western Norway. We argue that the sea‐level curve indicates that the Younger Dryas glacial advance started in the late Allerød or close to the Allerød–Younger Dryas transition. Copyright © 2004 John Wiley & Sons, Ltd.

Late Quaternary tephrochronology of Sweden: a review

Studies of Late Quaternary sediments in south and central Sweden have yielded a detailed tephrochronology for the Last Glacial–Interglacial transition (LGIT; ca. 15,000–10,000 cal. yr BP) and the Holocene. More than ten tephra layers have been detected and geochemically characterised. The most widespread tephra from the LGIT is the rhyolitic phase of the Vedde Ash (ca. 12,000 cal. yr BP) which has been found in lacustrine sediments and marine clays south of the Younger Dryas moraines in south Sweden. Other horizons from the LGIT identified to date include the Borrobol tephra (ca. 14,400 cal. yr BP), the Hässeldalen tephra (ca. 11,500 cal. yr BP), the 10-ka Askja tephra (ca. 11,300 cal. yr BP) and the Högstorpsmossen tephra (ca. 10,200 cal. yr BP). The most significant Holocene isochrones are Hekla-4 (ca. 4260 cal. yr BP), Hekla-Selsund/Kebister (ca. 3750 cal. yr BP), Hekla-3 (ca. 3000 cal. yr BP) and Askja-1875. Two new Late Holocene tephra horizons (the Stömyren tephra, ca. 2100 cal. yr BP and the Gullbergby tephra; ca. 2700 cal. yr BP) were identified in single sites and are so far less valuable as marker horizons, but are potentially important for the future.

A coherent high‐precision radiocarbon chronology for the Late‐glacial sequence at Sluggan Bog, Co. Antrim, Northern Ireland

AbstractSeventy‐five radiocarbon dates are presented from Sluggan Bog in Co. Antrim, Northern Ireland. The Holocene peats are underlain by Late‐glacial sediments, which also appear to have accumulated largely in a mire environment. The radiocarbon dates, from the Late‐glacial and early Holocene part of the profile, were obtained from the humic and humin fractions of the sedimentary matrix, and from plant macrofossils. The last‐named were dated by AMS and the sediment samples by radiometric (beta counting) methods. Age–depth models for the three dating series show a very high level of agreement between the two fractions and the macrofossils. No statistically significant difference is found between the beta counting and AMS results. Three tephras were located in the profile, the uppermost of which is in a stratigraphical position suggestive of the Vedde Ash, but the geochemical and radiocarbon evidence do not support this interpretation. The lower ashes are in the correct stratigraphical position for the Laacher See and Borrobol tephras, attributions substantiated by the radiocarbon evidence, but not by the geochemical data. The Sluggan sequence has generated one of the most internally consistent radiocarbon chronologies for any Late‐glacial site in the British Isles, and it is suggested that in future more effort should be devoted to the search for, and analysis of, Late‐glacial mire sequences, rather than the limnic records that have formed the principal focus of Late‐glacial investigations hitherto. Copyright © 2004 John Wiley & Sons, Ltd.

Environmental changes off North Iceland during the deglaciation and the Holocene: foraminifera, diatoms and stable isotopes

A combined study of foraminifera, diatoms and stable isotopes in marine sediments off North Iceland records major changes in sea surface conditions since about 15 800 cal years (yr) BP. Results are presented from two gravity cores obtained at about 400 m water depth from two separate sedimentary basins on each side of the submarine Kolbeinsey Ridge. The chronology of the sedimentary record is based partly on AMS 14C dates, partly on the Vedde and the Saksunarvatn tephra markers, as well as the historical Hekla AD 1104 tephra. During the regional deglaciation, the planktonic foraminiferal assemblages are characterised by consistently high percentages of sinistrally coiled Neogloboquadrina pachyderma. However, major environmental variability is reflected by changes in stable isotope values and diatom assemblages. Low δ 18O values indicate a strong freshwater peak as well as possible brine formation by sea-ice freezing during a pre-Bølling interval (Greenland Stadial 2), corresponding to the Heinrich 1 event. The foraminifera suggest a strong concurrent influence of relatively warm and saline Atlantic water, and both the foraminifera and the diatoms suggest mixing of cold and warm water masses. Similar but weaker environmental signals are observed during the Younger Dryas (Greenland Stadial 1) around the level of the Vedde Ash. Each freshwater peak is succeeded by an interval of severe cooling both at the beginning of the Bølling–Allerød Interstadial Complex (Greenland Interstadial 1) and during the Preboreal, presumably associated with the onset of intense deep water formatiom in the Nordic Seas. The Holocene thermal optimum, between 10 200 and about 7000 cal years (yr) BP, is interrupted by a marked cooling of the surface waters around 8200 cal yr BP. This cold event is clearly expressed by a pronounced increase in the percentages of sinistrally coiled N. pachyderma, corresponding to a temperature decrease of about 3°C. A general cooling in the area is indicated after 7000–6000 cal yr BP, both by the diatom data and by the planktonic foraminiferal data. After a severe cooling around 6000 cal yr BP, the planktonic foraminiferal assemblages suggest a warmer interval between 5500 and 4500 cal yr BP. Minor temperature fluctuations are reflected both in the foraminiferal and in the diatom data in the upper part of the record, but the time resolution of the present data is not high enough to pick up details in environmental changes through the late Holocene.

Modelling the southern extent of the last Icelandic ice‐sheet

AbstractA three‐dimensional, time‐dependent numerical ice‐sheet model is used to investigate the southern extent of the last Icelandic ice‐sheet since the Last Glacial Maximum (LGM, ca. 20 000 14C yr BP). Ice development over southern Iceland is forced using a linear relationship between mass balance and altitude based on observations over Sólheimajökull, a southern outlet glacier of the Mýrdalsjökull ice‐cap. A continentality factor is introduced that raises inland equilibrium‐line altitudes (ELAs) and also slackens the mass‐balance/altitude gradient driving the model. With this calibration the present‐day ice distribution can be reconstructed. Growth from ice‐free to total ice cover is assessed and the sensitivity of ice extent to ELA change is shown to be non‐linear. The model indicates that an ELA lowering of 500 m, consistent with a ca. 5°C temperature depression for southern Iceland at the LGM, would enable glacier ice to cover the whole land surface within the modelled area and inundate any putative ecological refugia. Modelling with a 300 m ELA depression, consistent with previous reconstructions of Younger Dryas (YD, 10 000–11 000 14C yr BP) ice extent, indicates that the principal outcrops of the Sólheimar ignimbrite were glaciated at this time, suggesting that an origin during this stadial (and a correlation with North Atlantic Ash Zone I / Vedde Ash) is problematic. Copyright © 2003 John Wiley & Sons, Ltd.

Chemical composition, distribution, and origin of silicic volcanic ash layers in the Greenland–Iceland–Norwegian Sea: explosive volcanism from 10 to 300 ka as recorded in deep-sea sediments

Explosive ocean island volcanism in the Greenland–Iceland–Norwegian Sea (GIN Sea) is indicated by marine tephra layers at 10–300 ka. Peaks of explosive volcanism occurred in oxygen isotope stages 8, 7, 5 and 1. The depositional age of the tephra was estimated using the oxygen isotope stratigraphy and dating of marine records. Geochemical analyses of the tephra layers show that all originate from Iceland. Here we report the characteristics of tephra from these major Icelandic events in 30 deep-sea cores from the GIN Sea. Our findings provide constraints on the distribution of tephra from the eruption source. For the Vedde Ash (oxygen isotope stage 1) we estimate a minimum fallout area of 2∗10 5 km 2, stretching from central Greenland in the west and southern Sweden in the east, to 71°N in the GIN Sea. The magnitude of the eruption and the regional wind conditions controlled the extent and concentrations of these ash fallout events. Oceanic circulation and differential settling may have affected the distribution and final deposition of ash particles such as bubble wall shards.

High‐resolution study of Icelandic tephras in the Kangerlussuaq Trough, southeast Greenland, during the last deglaciation

AbstractTephra abundance data and geochemistry in Late‐glacial and Holocene sediments on the East Greenland shelf are presented. Two well‐known tephras were identified from electron microprobe analysis of tephra shards picked from ash peaks in the cores. These are the Vedde Ash and Saksunarvatn Ash, which probably were deposited on the shelf after transport on drifting ice. The radiocarbon dates (marine reservoir corrected by −550 yr) that constrain the timing of deposition of the tephra layers compare well with the terrestrial and ice‐core ages of the tephras without requiring additional reservoir correction to align them with the known tephra ages. Several prominent tephra layers with a composition of Ash Zone 2 tephra punctuate the deglacial sediments. These tephra peaks coincide with significant light stable isotope events (signifying glacial meltwater) and fine‐grained sediments poor in ice‐rafted detritus. We interpret the Ash Zone 2 tephra peaks as sediment released from the Greenland Ice Sheet during strong melting pulses of the deglaciation. Copyright © 2002 John Wiley & Sons, Ltd.

Early to middle Holocene silicic tephra horizons from the Katla volcanic system, Iceland: new results from the Faroe Islands

AbstractComparatively few Icelandic tephra horizons dated to the early part of the Holocene have so far been detected outside Iceland. Here, I present several tephra horizons that have been recorded in a Holocene peat sequence on the Faroe Islands. Geochemical analyses show that at least two dacitic and one rhyolitic tephra layers were erupted from the Katla volcanic system on southern Iceland between ca. 8000 and 5900 cal. yr BP. The upper two layers can be correlated with the SILK tephras described from southern Iceland, whereas the third, dated to ca. 8000 cal. yr BP, has a geochemistry virtually identical to the rhyolitic component of the Vedde Ash. The results suggest that the Late Weichselian and early Holocene eruption history of the Katla volcano was probably more complex than inferred from Iceland. A new, early Holocene rhyolitic tephra dated to ca. 10 500 cal. yr BP probably originates in the Snæfellsnes volcanic centre in western Iceland. These new findings may play an important role in developing a Holocene tephra framework for northwest Europe. Copyright © 2002 John Wiley & Sons, Ltd.

The use of magnetic separation techniques to detect basaltic microtephra in last glacial-interglacial transition (LGIT; 15–10 ka cal. bp ) sediment sequences in Scotland

Synopsis Basaltic tephra horizons dominate the Icelandic tephrochronological framework during the last glacial-interglacial transition (LGIT; 15–10 ka cal. bp ), providing excellent potential for high precision correlation of palaeoclimate data-sets as recorded in ice, marine and terrestrial sequences of the North Atlantic region. Although significant advances have been made in identifying and extending the known provenance of rhyolitic tephras (in the form of microtephra horizons), the detection of basaltic layers has proved problematic. The bimodal Vedde Ash is an important chronological marker horizon that lies firmly within the GS-1/Younger Dryas chronozone (ca. 10.3 ka 14 C bp ; 12.0 ka GRIP ice-core yrs) and provides an excellent opportunity to develop methodologies for extracting both rhyolitic and basaltic ash. The recent identification of the rhyolitic component across Europe using flotation techniques has significantly extended the known provenance of this eruption event. However, there is no routine methodology for the identification of basaltic microtephra horizons and the separation of this component of the Vedde Ash has therefore been limited to visible horizons in Iceland, western Norway and the Isle of Skye. Here, we use magnetic separation techniques to identify for the first time basaltic Vedde Ash as a microtephra horizon in minerogenic sequences from two sites in western Scotland.

Towards a European tephrochronological framework for Termination 1 and the Early Holocene.

The record of deposition of tephras in Europe and the North Atlantic during the period 18.5-8.0 (14)C ka BP (the Last Termination and Early Holocene) is reviewed. Altogether, 34 tephras originating from four main volcanic provinces (Iceland, the Eifel district, the Massif Central and Italy) have been identified so far in geological sequences spanning this time-interval. Most of the records have been based, until very recently, on observations of visible layers of tephras. Here, we report on the potential for extending the areas over which some of the tephras can be traced by the search for layers of micro-tephra, which are not visible to the naked eye, and on the use of geochemical methods to correlate them with known tephra horizons. This approach has greatly extended the area in Northern Europe over which the Vedde Ash can be traced. The same potential exists in southern Europe, which is demonstrated for the first time by the discovery of a distinct layer of micro-tephra of the Neapolitan Yellow Tuff in a site in the Northern Apennines in Italy, far to the north of the occurrences of visible records of this tephra. The paper closes by considering the potential for developing a robust European tephrostratigraphy to underpin the chronology of records of the Last Termination and Early Holocene, thereby promoting a better understanding of the nature, timing and environmental effects of the abrupt climatic changes that characterized this period.

Palaeohydrography and marine conditions in the south-western part of the Vänern basin during the Younger Dryas and Early Preboreal

A clay-sequence from Lake Götesjön in the south-western part of the Lake Vänern basin has been investigated with respect to the foraminiferal and ostracod faunas and δ18Oc and δ13Cc. The sequence covers the middle/late Younger Dryas and the early part of the Preboreal chronozones. The conditions were severe during the Younger Dryas due to sea ice cover and a proximal position to the ice. The faunal assemblages indicate arctic glaciomarine conditions with a reduced salinity and the marine conditions ceased at c. 9700 14C-years BP. In the late Younger Dryas an increased ice retreat raised the salinity of the bottomwater. This was due to the formation of reaction currents with marine water entering the basin at the bottom as a response to a surface freshwater flowing out from the basin. A period with improved marine conditions is recorded in the Early Preboreal. The transition from the Younger Dryas to the Preboreal is recorded as a lowering in the δ18Oc due to increased input of meltwater and higher δ13Cc as a consequence of a more intensive mixing of water masses and a less extensive sea ice cover. The Vedde Ash is found in the lower part of the sequence and AMS radiocarbon datings of bivalves suggest a marine reservoir age in the area of 800–900 years during the Younger Dryas. The final drainage of the Baltic Ice Lake had only limited effects on the marine environment in the south-western part of the Vänern basin.

Climate and environment on the Karelian Isthmus, northwestern Russia, 13000‐9000 cal. yrs BP

Sediment sequences retrieved from Lake Medvedevskoye (60°13'N; 29°54'E) and Lake Pastorskoye (60°13'N; 30°02'E), Karelian Isthmus, northwestern Russia, were analysed for lithology, pollen and diatom stratigraphy, total organic carbon content and mineral magnetic parameters. Age control for both sequences was provided by AMS 14C measurements and the Vedde Ash tephra. The reconstructed climatic and environmental development shows the deglaciation of the sites and the establishment of sparse shrub and herb/grass vegetation before 12650 cal. yrs BP (‘Allerød’; GI‐1a). Steppe tundra and cold, dry conditions prevailed until about 11000 cal. yrs BP, i.e. throughout the ‘Younger Dryas’ (GS‐1) and the earliest Holocene. The establishment of open Picea‐Pinus‐Betula forest around the lakes at about 11 000 cal. yrs BP coincides with the first distinct change towards gradually warmer and more humid climatic conditions. Boreal forest with Picea, Pinus, Betula, Alnus incana and Corylus was present at the lower altitude site between c. 10700 and 10200 cal. yrs BP, while open Betula‐Pinus forest continued to dominate the vegetation around the higher altitude site. After a short, possibly colder, phase around 10200‐10000 cal. yrs BP, which is expressed by a marked reduction in vegetation cover and decreased lake productivity, climatic conditions became significantly warmer and possibly more humid. Boreal forest with Pinus, Betula, Picea, Alnus incana, Corylus and Ulmus became widespread in the region after 10000 cal. yrs BP. The delayed environmental response of the lakes and their catchment to hemispheric warming at the Pleistocene/Holocene boundary may be explained by a sustained blocking of westerly air masses due to the presence of the Scandinavian ice sheet and associated strengthened easterlies and anticy‐clonic circulation and/or extensive permafrost.

Climate and environment on the Karelian Isthmus, northwestern Russia, 13000-9000 cal. yrs BP

Sediment sequences retrieved from Lake Medvedevskoye (60degrees13'N 29degrees54'E) and Lake Pastorskoye (60degrees13'N, 30degrees02'E). Karelian Isthmus, northwestern Russia, were analysed for lithology, pollen and diatom stratigraphy, total organic carbon content and mineral magnetic parameters. Age control for both sequences was provided by AMS C-14 measurements and the Vedde Ash tephra. The reconstructed climatic and environmental development shows the deglaciation of the sites a-ad the establishment of sparse shrub and herb/grass vegetation before 12650 cal. yrs BP ('Allerod'; GI-1a). Steppe tundra and cold, dry conditions prevailed until about 11000 cal. yrs BP. i.e. throughout the 'Younger Dryas' (GS-1) and the earliest Holocene. The establishment of open Picea-Pinus-Betula forest around the lakes at about 11000 cal. yrs BP coincides with the first distinct change towards gradually warmer and more humid climatic conditions. Boreal forest with Picea, Pinus, Betula, Alnus incana and Corylus was present at the lower altitude site between c. 10700 and 10200 cal. yrs BP. while open Betula-Pinus forest continued to dominate the vegetation around the higher altitude site. After a short, possibly colder, phase around 10200-10000 cal. yrs BP, which is expressed by a marked reduction in vegetation Cover and decreased lake productivity. Climatic conditions became significantly warmer and possibly more humid. Boreal forest with Pinus, Betula, Picea, Alnus incana, Con-his and Ulmus became widespread in the region after 10000 cal. yrs BP, The delayed environmental response of the lakes and their catchment to hemispheric warming at the Pleistocene/Holocene boundary may be explained by a sustained blocking of westerly air masses due to the presence of the Scandinavian ice sheet and associated strengthened easterlies and anticyclonic circulation and/or extensive permafrost. (Less)

A calendar age estimate of a very late Younger Dryas ice sheet maximum in western Norway

We have established an accurate chronology in calendar years for the maximum phase of the Younger Dryas (YD) Scandinavian Ice Sheet in western Norway. Glaciomarine silt confidentially identified in shallow marine basins located was 1-2 km distal to a YD ice-marginal delta. Due to the topography of this area, the silt monitors faithfully the period when the ice sheet reached and remained at its maximum position. In these basins the deposition of silt commenced 6–10 cm above the Vedde Ash Bed (ca 10,300 14C yr BP or ca 12,000 cal yr BP). According to calculated sedimentation rates of the deposits, the deposition of silt started, and thus the ice sheet reached its maximum, 300–400 years after the Vedde Ash fall, around 11,600–11,700 cal yr BP. The ice sheet receded from its maximum position simultaneously with the increase of Betula (birch) pollen at the YD/Holocene boundary, ca 11,500 cal yr BP. The duration of the YD glacial maximum of the Scandinavian Ice Sheet in western Norway was only about 100–200 years, and is constrained within the 14C plateau at 10,000 14C yr BP. The YD glacial maximum occurred extremely late in western Norway, later than elsewhere in Scandinavia. The result also demonstrates different response times for different glaciers. Small cirque glaciers farther north in western Norway expanded to their maximum position very early in the YD, whereas the ice cap at Ålfotbreen reached its maximum later, but still before the Vedde Ash fall. The ice sheet reached its maximum well after the Vedde Ash fall, and only 100–200 years before the YD/Holocene boundary.

An event stratigraphy for the Last Glacial–Holocene transition in eastern middle Sweden: results from investigations of varved clay and terrestrial sequences

This paper presents an event stratigraphy for the Last Glacial–Holocene transition in eastern middle Sweden. The event stratigraphy for eastern middle Sweden comprises ten events and covers the time-span from ca 12,900 to 10,200 cal yr BP. The local event stratigraphy has been linked to the GRIP isotopic event stratigraphy by different correlations. The onset of the Younger Dryas is dated to 12,650 cal yr BP. This cold event lasted for ca 1125 cal yr in the area. The Vedde Ash (ca 12,000 cal yr BP) has been recorded in two terrestrial sequences, which makes it possible to exactly link the event stratigraphy to the GRIP ice-core and to marine cores in the North Atlantic region. The final drainage of the Baltic Ice Lake has been dated to ca 11,560 cal yr BP, which predates the Younger Dryas/Preboreal climatic boundary with ca 35 yr. An early Holocene cold event has been detected both in terrestrial and varved clay sequences at ca 11,305–11,185 cal yr BP. This cold event coincides almost exactly with a brackish water phase in the Baltic Sea. A previously unrecorded early Holocene tephra horizon has been found in lacustrine sediments at ca 10,200 cal yr BP.

Were rhyolitic glasses in the Vedde Ash and in the North Atlantic's Ash Zone 1 produced by the same volcanic eruption?

New evidence from North Atlantic deep-sea sediment cores suggests that rhyolitic glass shards in Ash Zone 1 and in the Vedde Ash may not have been produced by the same eruption as has been widely assumed. Our argument is based on (1) a marine ice-rafted deposit approximately 1000 years older than the Vedde Ash contains rhyolitic shards with the same major element chemistry as the Vedde Ash itself and (2) coincidence of Ash Zone 1 with an abrupt increase in discharge of glacial icebergs into the North Atlantic. Hence, we cannot rule out the possibility that Vedde-like rhyolitic glasses were erupted onto Icelandic glaciers before eruption of the Vedde Ash, stored in the glacial ice, then dispersed by icebergs into the North Atlantic and deposited partly or entirely as Ash Zone 1. While not disproving that Ash Zone 1 and the Vedde Ash came from the same eruption, our findings indicate that further study is needed to establish the exact relation between the two ash deposits.

Identification and significance of a visible, basalt‐rich Vedde Ash layer in a Late‐glacial sequence on the Isle of Skye, Inner Hebrides, Scotland

AbstractThis paper reports the discovery of a visible, tephra horizon of Late‐glacial age from the site of Loch Ashik in the Isle of Skye, the Inner Hebrides, Scotland. Although the tephra shards have a bimodal geochemical composition identical to that of the Vedde Ash (a well known marker horizon within Late‐glacial sequences. The horizon at Ashik is dominated by basaltic shards and devitrified tephra shards, giving the layer its characteristic black colour. Only rhyolitic shards have previously been reported from Vedde Ash horizons in the British Isles. This new evidence raises some important questions about the factors that govern the distribution and accumulation of basaltic tephra, and about the methods used to detect ash shards in basins distal to centres of volcanic activity. Copyright © 2001 John Wiley & Sons, Ltd.

The marine14C age of the Vedde Ash Bed along the west coast of Norway

Articulated molluscs, sea urchins and barnacle fragments close to the Vedde Ash Bed in a shallow marine deposit on the west coast of Norway have been 14C dated. The weighted mean of four dates from a sediment slice 8 cm thick centred on the Vedde Ash Bed is 10920 ± 24 14C yr BP. The most accurate 14C age of the Vedde Ash from terrestrial plant macrofossils is 10310 ± 50 yr BP. The difference is the 14C reservoir age for coastal water at the west coast of Norway during the mid-Younger Dryas and equals 610 ± 55 yr. This is 230 yr older than the reservoir age for the Bolling/Allerod and for the present day in this area. The result supports earlier conclusions of a higher reservoir age for the Younger Dryas in the North Atlantic and Nordic Seas, although our reservoir age of 610 ± 55 yr is a few hundred years younger. This suggests that the 14C reservoir age at Vedde Ash time may increase from coastal water towards the open North Atlantic and Nordic Seas. Copyright © 2001 John Wiley & Sons, Ltd.

The marine 14C age of the Vedde Ash Bed along the west coast of Norway

The marine 14C age of the Vedde Ash Bed along the west coast of Norway