1

Field guide

for the NORDQUA excursion

to Sunnmøre, western Norway,

22-25 September 2014.

Eiliv Larsen

1, Jan Mangerud

2, and John Inge

Svendsen2.

1The Geological Survey of Norway.

E-mail: Eiliv.Larsen@ngu.no

Mobile phone: +47 95 85 50 51.

2Department of Earth Science, University of Bergen.

Jan.Mangerud@geo.uib.no, Mobile phone: +47 90 94 49 46

John.Svendsen@geo.uib.no, Mobile phone: +47 97 46 50 13

2

Foreword

This excursion guide was written before our pre-excursion planning trip. It will therefore probably

be some minor changes in the program.

Most of the older literature that we refer to in the guide can be down-loaded from Jan Mangeruds

home page: http://www.folk.uib.no/ngljm/. If any of you have problems to obtain papers where one

of us is author/co-author then do not hesitate to send us an e-mail with request.

Program Day 1.

Arrival at Ålesund airport, Vigra.

Site 1: Skjonghelleren Cave. Only some 8-10 people can creep into Skjonghelleren at a time, so we

will try to find some parallel activity.

Site 2: Dimna bog. Coring. Vedde and Dimna ash beds.

Stay overnight in Quality Hotel, Ulsteinvik.

Day 2.

Site 3: Mulevika on the westernmost shore of Nerlandsøy. Beach ridge at marine limit.

Site 4. Frøystadmyra, Leinøy. Coring. Tsunami, sea-level changes.

Site 4: Litlevatn, Gurskøy. Coring. Sea-level changes. Litlevatn was isolated during Late Allerød.

Stay overnight in Best Western Hotel Baronen, Spjelkavik.

Day 3.

Site 5. Riksheim, Sykkylven. Sections in Younger Dryas local moraine.

Site 6. Hundeidvik. Gravel pit in Younger Dryas sandur-delta.

Stay overnight in Best Western Hotel Baronen, Spjelkavik.

Day 4.

We will see Younger Dryas moraines, blockfields in the mountains, in addition to the major

geomorphology along the fjords on our way.

Site 7. Skorgenes in Tresfjorden. Three superimposed ice marginal deltas.

Departure from Ålesund or Vigra.

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Fig. 1 An overview map. The red square shows the excursion area. The Last Glacial Maximum

(LGM) ice limit is marked along the continental shelf edge. Note that the YD ice margin in

Sunnmøre is located near the fjord heads in contrast to around Bergen where the YD margin almost

reached the open ocean.

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Fig. 2. Overview map of the excursion area.

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Skjonghelleren and the Ålesund interstadial

Skjonghelleren is a cave located close to the Vigra (Ålesund) airport and will be the first locality we

visit. The cave is the type locality for the Ålesund Interstadial (Larsen et al., 1987), the best dated

pre-LGM interstadial in the Nordic countries. The cave is formed by sea waves during the Early

Weichselian or before. Simplified there are two types of sediments (Fig. 4); 1) blocks deposited

during ice-free periods and 2) laminated clay deposited when the opening was blocked by the

Scandinavian Ice Sheet. Three pre-Holocene block layers are described (Fig. 6) (Larsen et al.,

1987); here we will concentrate on the youngest, the Ålesund interstadial bed. The Laschamp

paleomagnetic excursion is identified in the clay bed below Ålesund, and the Mono Lake excursion

in the bed above Ålesund (Fig. 10) (Larsen et al., 1987; Løvlie and Sandnes, 1987). These

excursions are correlated with increased fluxes of cosmic-radiation produced isotopes in Greenland

ice cores (Mangerud et al., 2003). The Ålesund interstadial is dated by more than 40 AMS 14

C dates

(Figs 8 and 10) (Mangerud et al., 2010) from Skjonghelleren and Hamnsundhelleren – a cave east

of Skjonghelleren.

Fig. 3. Map of Valderøya with Skjonghelleren marked with blue dot.

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Fig. 4. The depositional environments and sediment succession in Skjonghelleren, from Mangerud

et al. (2010).

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Fig. 5. Upper panel: Longitudinal profile of Skjonghelleren. Note that the cave is >70 m long and

that there is >20 m thick sediments in the cave. Lower panel: map of the cave. From (Larsen et al.,

1987).

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Fig. 6. The section and coring results from the outer part of the cave. From Larsen et al. (1987).

During the excursion we will see Laminated clay F and the block on top.

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Fig. 7. The section in the innermost part of the cave, that we will see during the excursion. From

Larsen et al. (1987).

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Fig. 8 .Table of bones identified at an early stage From Larsen et al (1987).

Presently > 30 000 bones are picked from Ålesund interstadial beds in Skjongehelleren and 15 000

in Hamnsundhelleren.

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Fig. 9. The radiocarbon ages from Skjonghelleren, Hamnsundhelleren and shellbearing tills. From

Mangerud et al. (2010).

Fig. 10. Comparison betwen Greenland ice cores and Sunnmøre. Note that black curves and ages

refer to the Middle Weichselian, whereas red refer to the Late Weichselian. From Mangerud et al.

(2010).

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Fig. 11. Correlation between the Ålesund and Greenland ice cores. From Mangerud et al. (2010).

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Fig. 12. A glaciation curve for the entire Weichselian, where the events found in Sunnmøre are

marked. From Mangerud et al. (2011).

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Shellbearing tills

The Ålesund interstadial was originally defined from radiocarbon dates from shell fragments in till

(Mangerud et al., 1981; Mangerud et al., 1979). Such tills are only exposed in temporarily

excavations for buildings, roads, etc. and we do yet not know if any exposure will be available.

Later re-dating with AMS confirm that most of the sites are of Ålesund age (as defined in

Skjonghelleren), whereas some sites pre-date the Laschamp and we therefore named that ice-free

period for Austnes interstadial (Mangerud et al., 2010).

Fig. 13. The excavated caves (red dots and names) and sites with shell-bearing tills (numbers). 1 -

Rogne, 2 - Longva, 3 - Ullaholmen, 4 - Austnes, 5 – Hildrestrand, 6 – Gjøsundet, Vigra, 7 – Synnes,

Vigra, 8 – Vikebukt, Vigra, 9 – Dyb, Godøy, 10 – Liaaen, Ålesund (that was the first site

discovered), 11 – Spjelkavik, Ålesund, 12 – Eidsvik.

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The Vedde and Dimna ash beds

The discovery of the Vedde Ash and its correlation with Ash Zone 1 in the North Atlantic and ash

beds in the Norwegian Sea (Kvamme et al., 1989; Mangerud et al., 1984) triggered a search for

Vedde and other ashes in the north-west Europe, the surrounding seas and in Greenland ice cores.

Vedde is presently found at a large number of sites (Lane et al., 2012) and is a key horizon for

correlation between continental, marine and Greenland ice core sequences. We will see the Vedde

Ash at several coring sites the first and second day.

We searched for more ashes and discovered the Dimna Ash with identical composition as the

rhyolitic component of the Vedde Ash (Koren et al., 2008; Lane et al., 2012). We will core the type

locality, where the Vedde Ash also is much thicker than any other place in Norway - up to 48 cm

thick.

Fig. 14. Vedde Ash in the Ålesund area. After Mangerud et al (1984)

Fig. 15. Stratigraphic position of the Vedde Ash in different settings and elevations above sea level.

After Mangerud et al (1984)

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Fig. 16. The distribution of the Vedde Ash – from Greenland to Italy. From Lane et al (2012).

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Fig. 17. Maps showing of the location and coring sites at Dimnamyra (-bog). From Koren et al

(2008).

Fig. 18. Cross section of Dimnamyra. From Koren et al. (2008).

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Fig. 19. Stratigraphy in Dimnamyra. From Koren et al. (2008).

Fig. 20. Ashes in Dimnamyra (-bog). From Koren et al. (2008).

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Fig. 21. Left figure: Geochemistry of ash beds. Right figure: Late glacial ashes in NW Europe.

From Koren et al (2008).

Fig. 22. Trace element composition of the Vedde and Dimna ashes. From Lane et al (2012).

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Fig. 23. Pollen diagram from Dimnamyra. From Krüger et al. (2011).

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Relative sea-level fluctuations

Shore lines and sea-level fluctuations will be the main theme for the second day. We have used the

classical Nordic method utilizing isolation basins. This might be familiar for most participants, but

we include a first figure explaining the principle.

We include then a number of illustrations from the sites we will core. In the next section include

some figures from a syntheses paper for sea-level changes for the entire Late Glacial and the

Holocene and across a larger area. Note that these “old” papers use only un-calibrated C-14 years.

Fig. 24. The principle of isolation basin method. From Svendsen and Mangerud (1987)

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Fig. 25. Location map for the coring sites. From Svendsen and Mangerud (1990).

Fig. 26. Map of Frøystadmyra. From Svendsen and Mangerud (1990).

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Fig. 27. The stratigraphy in the studied basins – as we described them before we discovered the

Storegga tsunami. Note “Mixed sediments” in Skolemyra. A “tsunami version” is given in Fig. 34.

Note the dashed line that connect the Vedde Ash between the columns. From Svendsen and

Mangerud (1990).

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Fig. 28. Cross section of Frøystadmyra I. From Svendsen and Mangerud (1990).

Fig. 29. The original sea-level curve and the one revised after we discovered the Storegga tsunami.

From Bondevik et al (1998).

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The Storegga tsunami

The very last day of field work for his Master thesis in 1983 John Inge Svendsen discovered a bed

of marine sand and shell above the Tapes transgression level. He proposed that it possibly could be

a deposit from a tsunami that the Storegga Slide could have released. However, because Jan

Mangerud now had started a major research project on Svalbard, where John Inge followed to do

his Dr. thesis, the tsunami hypothesis was not tested until Stein Bondevik started with his Dr. thesis

ten years later. We, and other scientists, had earlier interpreted the tsunami deposits as the result of

the Tapes transgression (relative sea-level rise). This had led to construction of a too fast, and some

places too high Tapes transgression (Bondevik et al., 1998). We subsequently found that the Tapes

very rarely (never?) had eroded sediments in basins that are some few meter deep, whereas the

tsunami most often had eroded. Deposits from the Storegga tsunami are now found around the

entire North Sea and also on Greenland (Bondevik et al., 2005a; Bondevik et al., 2005b; Bondevik

et al., 1997a; Bondevik et al., 1997b).

Fig. 30. The Storegga Slide and sites where Storegga tsunami deposits are described. From

Bondevik et al (2005).

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Fig. 31. How run-up for the tsunami is determined. From Bondevik et al (2005).

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Fig. 32. Modeling of the tsunami. After Bondevik et al (2005).

Fig.,33. Tsunami facies. From Bondevik et al (1997a).

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Fig. 34. The Storegga tsunami deposits in Frøystadmyra and neighbouring sites. From Bondevik et

al. (1997a)

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A synthesis of sea-level changes.

Fig. 35. An overview map showing the area we studued (Hatched) and the profile line for Fig. X.

After Svendsen and Mangerud (1987).

Fig. 36. The isobases and projection planes used. After Svendsen and Mangerud (1987).

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Fig. 37. Shoreline diagram for Sunnmøre-Trøndelag. Note that ages are in uncalibrated C-14 years.

After Svendsen and Mangerud (1987).

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Fig. 38. Sea-level curves deduced from the shore-line diagram. After Svendsen and Mangerud

(1987).

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Fig. 39. Profiles across Scandinavia, indicating how “shorelines” should bend over the landmass.

After Svendsen and Mangerud (1987).

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Younger Dryas cirque moraines

As seen from the map Fig. 1 the Younger Dryas ice sheet moraines are located near the head of the

fjords. In the, often alpine type, mountains farther west there were numerous cirque glaciers during

the Younger Dryas. Most of these local glaciers apparently survived the Allerød, although they

probably were smaller than during the Younger Dryas (Larsen et al., 1998), whereas the well-

studied Kråkenes glacier was formed soon after the onset of the Younger Dryas (Larsen et al., 1984;

Lohne et al., 2014; Mangerud et al., 1979). On day 3 we will visit the site Riksheim with an

exposure in such a moraine and also some other sites in the vicinity of Riksheim.

Fig. 40. The black lines are moraines, mainly cirque moraines. Note Ålesund in upper left corner.

We will visit Sykkylvsfjorden, a tributary to Storfjorden in the right hand part of the map. From

Follestad (1995)

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Fig. 41. Maps of the cirque moraines at Riksheim and adjacent sites. From Larsen et al (1998).

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Fig. 42. Profile from Riksheim. From Larsen et al (1998).

Fig. 43. Glaciation relative to sea level at Riksheim. From Larsen et al (1998).

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Fig. 44. Reconstructions of the develoment at Riksheim. From Larsen et al (1998).

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Skorgenes – two pre-LGM interstadials in superposition

Skorgenes is a rare, if not unique site in Norway because the late-glacial marine limit delta directly

overlies two earlier deglacial sequences separated by two basal tills (Larsen and Ward, 1992).

Fig. 45. Location of Skorgenes. From Larsen and Ward (1992).

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Fig. 46. Map of the Skorgens site. From Larsen and Ward (1992).

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Fig. 47. Stratigraphy at Skorgenes. From Larsen and Ward (1992).

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Fig. 48. Stratigraphy and fabric at Skorgenes. From Larsen and Ward (1992).

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Fig. 49. Obtained OSL dates from Skorgenes and correlation with Skjonghelleren. From Larsen and

Ward (1992).

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In the lowest formation at Skorgenes there are some spectacular clastic dikes, interpreted as

injection veins from the sole of the ice sheet into the underlying sediments (Larsen and Mangerud,

1992). They are some few cm in diameter and many meters long, mainly almost vertical, but

sometimes horizontal for several meters. This part of the section is normally covered by sloped

material, but we will attempt to find an operator with excavator to clean that part for our excursion.

Fig. 50. Detail of a clastic dike at Skorgenes – horizontal with a branch turning down. Note the

small offset in the primary bedding. The scale is the top of a knife, so this vein is 2-3 cm thick.

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Other topics

As we travel around and see the landscape the excursion guides and any of the participants can

comment on, ask questions, or start a provocative discussion about the observations.

We will for example see the large, almost horizontal platform along the coast, named the

Norwegian Strandflat, for which ages and processes are much discussed.

Fjords and fjord formation is probably easier, or ---?

We will from Vigra (see Gamlemsveten) and when crossing the mountains the last day, see

extensive mountain block fields. Do they demonstrate ice free summits during glaciations?

If we are not too unlucky with the weather we will several places have nice view of the

alpine topography of the mountains “Sunnmørsalpene”. Did these narrow peaks escape

glaciation, or did they survive under cold-based ice?

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References. Bondevik, S., Løvholt, F., Harbitz, C., Mangerud, J., Dawson, A., Svendsen, J.I., 2005a. The

Storegga Slide tsunami—comparing field observations with numerical simulations.

Marine and Petroleum Geology 22, 195-208.

Bondevik, S., Mangerud, J., Dawson, S., Dawson, A., Lohne, Ø., 2005b. Evidence for three North

Sea tsunamis at the Shetland Islands between 8000 and 1500 years ago. Quaternary

Science Reviews 24, 1757-1775.

Bondevik, S., Svendsen, J.I., Johnsen, G., Mangerud, J., Kaland, P.E., 1997a. The Storegga tsunami

along the Norwegian coast, its age and runup. Boreas 26, 29-53.

Bondevik, S., Svendsen, J.I., Mangerud, J., 1997b. Tsunami sedimentary facies deposited by the

Storegga tsunami in shallow marine basins and coastal lakes, western Norway.

Sedimentology 44, 1115-1131.

Bondevik, S., Svendsen, J.I., Mangerud, J., 1998. Distinction between the Storegga tsunami and the

Holocene marine transgression in coastal basin deposits of western Norway. Journal of

Quaternary Science 13, 529-537.

Follestad, B.A., 1995. Møre og Romsdal Fylke - kvartærgeologisk kart 1 : 250 000. Norges

geologiske undersøkelse.

Koren, J.H., Svendsen, J.I., Mangerud, J., Furnes, H., 2008. The Dimna Ash -- a 12.8 14

C ka-old

volcanic ash in Western Norway. Quaternary Science Reviews 27, 85-94.

Krüger, L.C., Paus, A., Svendsen, J.I., Bjune, A.E., 2011. Lateglacial vegetation and

palaeoenvironment in W Norway, with new pollen data from the Sunnmøre region.

Boreas 10, no-no.

Kvamme, T., Mangerud, J., Furnes, H., Ruddiman, W., 1989. Geochemistry of Pleistocene ash

zones in cores from the North Atlantic. Norsk Geologisk Tidsskrift 69, 251-272.

Lane, C.S., Blockley, S.P.E., Mangerud, J., Smith, V.C., Lohne, Ø.S., Tomlinson, E.L., Matthews,

I.P., Lotter, A.F., 2012. Was the 12.1 ka Icelandic Vedde Ash one of a kind? Quaternary

Science Reviews 33, 87-99.

Larsen, E., Attig, J.W., Rune Aa, A., Sønstegaard, E., 1998. Late-glacial cirque glaciation in parts

of western Norway. Journal of Quaternary Science 13, 17-27.

Larsen, E., Eide, F., Longva, O., Mangerud, J., 1984. Allerød - Younger Dryas climatic inferences

from cirque glaciers and vegetational development in the Nordfjord area, western

Norway. Arctic and Alpine Research 16, 137-160.

Larsen, E., Gulliksen, S., Lauritzen, S.-E., Lie, R., Løvlie, R., Mangerud, J., 1987. Cave

stratigraphy in western Norway; multiple Weichselian glaciations and interstadial

vertebrate fauna. Boreas 16, 267-292.

Larsen, E., Mangerud, J., 1992. Subglacially formed clastic dikes. Svergies Geologiska

Undersøkning, Ser. Ca 81, 163-170.

Larsen, E., Ward, B., 1992. Sedimentology and stratigraphy of two glacial-deglacial sequence of

Skorgenes, western Norway. Norsk Geologisk Tidsskrift 72, 357-368.

Lohne, Ø.S., Mangerud, J., Birks, H.H., 2014. IntCal13 calibrated ages of the Vedde and

Saksunarvatn ashes and the Younger Dryas boundaries from Kråkenes, western

Norway. Journal of Quaternary Science 29, 506-507.

Løvlie, R., Sandnes, A., 1987. Paleomagnetic excursions recorded in mid-Weichselian cave

sediments from Skjonghelleren, Valderøy, W. Norway. Physics of the Earth and

Planetary Interior 45, 337-348.

Mangerud, J., Gulliksen, S., Larsen, E., 2010. 14

C-dated fluctuations of the western flank of the

Scandinavian Ice Sheet 45-25 kyr BP compared with Bølling-Younger Dryas

fluctuations and Dansgaard-Oeschger events in Greenland. Boreas 39, 328-342.

Mangerud, J., Gulliksen, S., Larsen, E., Longva, O., Miller, G.H., Sejrup, H.-P., Sønstegaard, E.,

1981. A Middle Weichselian ice-free period in Western Norway: the Ålesund

Interstadial. Boreas 10, 447-462.

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Mangerud, J., Gyllencreutz, R., Lohne, Ø., Svendsen, J.I., 2011. Glacial history of Norway, In:

Ehlers, J., Gibbard, P., Hughes, P. (Eds.), Quaternary Glaciations - Extent and

Chronology. Elsevier, Amsterdam.

Mangerud, J., Larsen, E., Longva, O., Sønstegaard, E., 1979. Glacial history of western Norway

15,000-10,000 B P. Boreas 8, 179-187.

Mangerud, J., Lie, S.E., Furnes, H., Kristiansen, I.L., 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.

Mangerud, J., Løvlie, R., Gulliksen, S., Hufthammer, A.-K., Larsen, E., Valen, V., 2003.

Paleomagnetic correlations between Scandinavian Ice-Sheet fluctuations and Greenland

Dansgaard-Oeschger Events, 45,000-25,000 yrs B.P. Quaternary Research 59, 213-222.

Svendsen, J.I., Mangerud, J., 1987. Late Weichselian and Holocene sea-level history for a cross-

section of western Norway. Journal of Quaternary Science 2, 113-132.

Svendsen, J.I., Mangerud, J., 1990. Sea-level changes and pollen stratigraphy on the outer coast of

Sunnmøre, western Norway. Norsk Geologisk Tidsskrift 70, 111-134.