Younger Dryas end morainesbetween Hardangerfjorden and Sognefjorden,Western

INCE AARSF,THAND JAN MANGERUD 'nl.?11,,'l'J,*I,:T:;:"i'+:,1 BOREN ff,';:ll'"j;t.y,:1,'.::1* :liJ::ii:tn*,';'J'."ii;t:;'f;l: End molaines (called the Moraines) from tho Younger Dryas Stadial are mor- phologicallymapped along the westerncoast of Norway, lrom Hardangerfjordento north of Sogncl.iorden.Thc: submar-ineposition of thc moraines arc found by means of a con- vcntional echo sounder. Stratigraphicalstudies with many c" datings are uscd for lge determination,giring L.ate Younger Dryas (10,000-10,500C'r year.sB.P.) for the Hcrdla Moraincs.Tho morainesirre corrclatedwith thc Ra-SalpaussclkiiMoraincs. Isobases fol the Younger Dryas arc obtained from marine tefrilccs formed conlemDoraneouslywith the moralncs.

Itlge Aurselh & Jun Muryerttd, Geologisk institttrt, Ayd. R., Olol Ryest,ei19,5011 Urriversitetet,Norh'u!, lTth I)ecenber,1973.

The largest end moraines in Eastern Norway moraines in was by Undis are the Ra Moraines, which according to Cll (1963). We were sceptical about some of his datings originate from the Younger Dryas conclusionsbecause of the lack of datings out- Stadial (referencesin Mangerud 1970, Fig. 10). side the supposed Younger Dryas moraines, These moraines have been known for more and becauseseveral of the depositsmapped by than 100 years and from many later investiga- him are very small and are, in our opinion, not tions (O. Holtedahl 1953: 617-658). Since the ice-front deposits.We have to revise the inter- discovery of the Ra Moraines, geologistshave pretations of Undis (1963) in many places, tried to find moraines of the same age in other but he is neverthelessright in his main con- parts of Norway. In the Ra Mo- clusions concerning the position of Younger raincs have been correlated with several dif- Dryas end moraines in this area. ferent moraines, such as the Moraines The position of the Younger Dryas and (Kaldhol 1941), and the Moraines other end moraines in Hordaland has remained (Undis 1944) at the very head of - unknown until recently because of two main fjorden, the Romarheim and Eidsland Mo- problems: raines (C. F. Kolderup 1908; N. H. Kolderup First, most of the end moraines 'l926) are very further north-west, the Ulven and Herdla small, l-5 m high, and in many areas the ice- Moraines (UndAs 1963; Mangerud 1970) even front sediments do not have constructional closer to the coast: location outside the coast forms at all. Obviously such deposits are very at Blomciy has also been discussed(H. Holte- difficult to map for long distar.rces,especially dahl 19621).Several methods have been used in forested and mountainous regions like parts for the correlations; all of them, however, of the present area. The area is also dissected were uncertain until the Cla dating was in- by numerous fjords and sounds, increasing the troduced. Wc therefore will not discussall the problem of correlation. older correlations. The second main problem has been the Beforc we started the investigations,the most dating of moraines. Because the mapping of recent attempt to map the Younger Dryas end end moraines is so extremely difficult. the { Inge Aursetlt and Jan Mangerttd BOREAS 3 (1914)

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i,'#; ltu$ tsoREAS3 (197,1) Younger Dryus end rtutraittes 5 corrclations with other areas depend strongly Submqrine areas upon datir-rgs.Introduction of the radiocarbon method provided a new solution, and by com- The complex landscapc with fjords and straits bining radiocarbon dating with other strati- dissectingthe landmass makes a correlation of graphical studies lve have achievcd relativcly supramarine moraines difficult. Attempts to good rcsults. trace submarine moraines on continental sheives by conver.rtionalecho soundings (King 1967, 1969) encouraged a similar investigation Methods in the fjords of Western Norway. The fact that the largest ice-front deposits are found below The moraines were first mapped on land. the marine limit also indicated the possibility However, for r-rearlyhalf the distancc thcy are of finding big submarineaccumulations. found below sea level. We therefore developed The ccho soundcr used is a 18 kHz Sinrrctd a simple mcthod for investigation of the mo- Scientilic Sounder -LK. This soundcr has a raines at the sca floor. depth-independent amplifier in addition to a penetrating effect in the sediment. The rclative Supramarine areas low pulsc powcr output (l kW) limits the The whole area is covcrcd by vertical air sub-bottom penetration to clay and silt. The photos (scalc ca. l:l5,000). In our opinion a beam width (13' x 20 ) reducesthc quality of satisfactory mapping would have been nearly the recording at grcater depths, but gives inter- impossiblc without the air photos, because as pretablereadings down to ca. 300 m. previously mentioned thc moraines in most of Several methods of using the soundcr were thc area are vcry small and discontinuous,artd testcd. In some arcas bottorn samples were they partly occur in forestsand steepmountain- taken to calibrate the recordings. The first slopes. attempt was madc in Fusafjorderr (Aarseth Wc have also studied the moraincs from a 1971) where a geological map (Fig. 3) was small airplane. The main advantage of this constructed on the basis of a dense pattern of method was a general view of the moraincs soundings. As can be seen from examples of (at full length ca. 200 km) and their topo- recordings from this fjord (Fig. ?), the moraine graphical positions. ridge differs clcarly from the ridges mainly Both of us have been doing ficld work cor.r- consistingof bedrock. The moraines have a ccrning Quaternary geology ir.r this arca for smooth surface, while the bedrock outcrops several ycars, and have investigated most of have a jagged topography. Grab sampling gave the moraines in somc dctail. Glacial striae are boulders, gravel, and fine sand on the mo- extcnsively mapped, some of thcm arc indi- raines, but no samples werc obtained from the cated in Fig. 1, and the youngest dircctions bedrock ridges. havc been used for thc reconstruction of thc The recordings from the echo soundings glacicr-front. show an increasing acoustic transparency of The most important resultsof the field work the sediments down the distal slopes of the have beer.rthe stratigraphy of the few sections moraines. This was interpreted as a grading of in the moraincs, arrd the stratigraphy of the the scdiments which was confirmed by grab sedimentsin the arcas inside and outside the samplesgiving finer sedimentsdown-slope. The nloraines. These investigations have provided maximum inclination of the distal slopesvaries material for Cla datings, and thereby an in- from 12 to 17 degrees. Small basins and flat dependent method for correlations of the arcas distal to the moraines gave the dcepest moraines within the area, and the only satis- echo penetration. I5 m, without reaching factory mcthod of correlation to other areas in bcdrock. Scandinavia. Continuous seismic profiling by thc Seis- mological Observatory in Bergcn showed that l'ig. 1. lVIap of thc coastal area betwecrt Hardanger- the maximum thickncss of the sediments in fjorclen and Sogncljordcn, Norway. Somc moraincs the deepestbasins of Bjcirnafjorden is ca. 100 m rroltlr and south ol thLr map urca ilre indicated in (Sellevoll,pers.comm.). Most of this is thought Fig. I l. C)n thc kcy map thc Youngcr Dryas cnd moraincs (Raet) in Southern Norway arc indicatcd to be glaciornarine sediments, dcpositcd in (scc Fig. ll). Allercid and Younger Dryas time. 6 Inge Aar.seth and Jan Manperud BOREAS 3 (971)

,/=^*\ fl ,\ ll It 'Jl

A 500m

DEPTH m * BEDROC K "Jl 25

O ,1, -8"r, MORAINE RIDGE p o or"( 175- I -.il I o-- \ T-

I\4ORAINERIDGE

c (1974\ BOREAS3 Younger Dryas end moraines 7

.1km- Londo,"o Compoct bottom with rough ! topogrophy(liloinly bedrocrT Soft bottom with ironsporeni echogrom(Cloy-Silt) z, _\4 ) lce-contoct slope Compoct bottom with smooth or A A Block concentrotion on the shore undulofing surfoce (TiI l- Sond-Grovel) Fig. 3. Fusafjorden between Vinnes and Os. Bathymetry and distribution of sedimentary units accord- ing to echogram interpretation. Echo depth in m. Based on 37 echo-sounding profiles with a total lensth of 120 km.

In the middle of Fusafjorden (Fig. 3), at a marine sedimentation ended ca. 3000 years depth of 200 m, the moraine ridges are lacking, ago. These figures are all taken from basins, but a belt of sediment crosses the fjord. Near where the sedimentation is supposed to be the Os area there is again a well-defined greatest. On top of the moraines in - moraine ridge (Fig. 2C) at a depth of 70-100 m fjorden grab samples showed till-like sediments (130-160 m at the time of deposition). The on the surface indicating no significant sedi- height of the ridge is 15 m on the proximal mentation in the Holocene. The same is slope and 25 m on the distal slope which has a obviously the case when bedrock is found at gradient of only 8'. or near the sea floor. This morphological interpretation is only In the Herdla area sufficient soundings have possible in aieas where the glacial forms are been obtained to give a relatively complete not buried by younger sediments. The maxi- picture of the form of the moraine, Fig. 7. In mum thickness of the Holocene sediments is the narrow straits further north, a single sound- found to be 15 m in Raunefjorden (Maisey ing along the deepest part of the strait gave the 1968), 5-12 m in Fensfjorden (Aarseth & main information on the sedimentary facies. Myhre in prep.) and 50 m for the pelagic The total number of echo-sounding profiles sediments in Hardangerfjorden (Holtedahl is ca. 300 with a total leneth of ca. 750 km. 1965). The Holocene sequence in the Vinnes Clay is 6.5 m thick, but at the actual core the Descriptionof the moraines Most of the information about the moraines Fig. 2. Echogram profiles from Bjdrnafjorden and Fusafjorden. A. From , 300 rn outside the is given in Fig. 1. The descriptionand discus- moraine headland. B. Outside Vinnes. C. Outside Os. sion are siven from south to north. 8 Inge Aorseth and Jan Manperuel BORL,AS3 (I974)

Strototypes fjorden (460 m deep), no moraine_like ridges are found. The glacier front was most lik;ly Frye & Willman (1962) proposed the use of floating, as the depth at that time exceeded land forms for formal stratigraphicalclassifica_ 530 m. The floating glacier resulted in an tion. This is widely used, especiallyfor strand_ extensive calving, which again caused a con_ lines and end moraines. There exists, however, verging ice movement in the fjord basin, with no general agreementabout its use and, among ice coming from north, easf, arrdsouth (Fig. 1). others, Flint (1971) argues against the use of The two last directions are the results oi ice end moraines as stratigraphic units. In our flowing from the Hardangerfjord glacier, opinion (Mangerud I970, 1973) end moraines where the most important ablation factor, provide a sound basis for stratigraphical clas_ calving, was limited at the grounded glacier sifications in glaciated areas, independent of front. other classifications,for instance. lithostratig_ In Strandvik the moraine forms a small raphy. A morphostratigraphic classification headland (Fig. a) of clayey till, protected should not be in opposition to the principles againstmarine abrasion by large boulders.This of thc Int. Subcom. Strat. Class. (1970a, b; ridge, 15 m high near the shore, can be traced 197la, b: I97T. out on the submarine platform where it fornrs In this paper we use Moraine - with a a 50 m high ridge (with a bedrock core?) with capital M - as a morphostratigraphic unit boulders on the surface (Fig. 2A1. The supra- term. In Norway the term substageis widely marine moraines can be traced almost con_ used with the same meaning (e.g. Anundsen tinuously up to 300 m a.s.l. (Fig. 4), and a I972; Follestad 1972). This should, however, nunatak moraine is situated on a 4g0 m hish be avoided, as substageis a chronostratigraphic mountain north-east of Strandvik. In this area unlt term. the supramarine moraines usually are small, We have mapped the end moraines for 1-3 m high, but distinct from the generally approximalely 200 km in very rugged topog_ bare bedrock surface. The very steep gradient, raphy. Nevertheless we find the correlations 100 m/km for the last 4 km, is due to the ice certain enough to use one term (Herdla Mo_ fall in the nunatak area and to the chanse in rair.res)for thc whole area. The description of flow direction from south to west nea; the lhe stratotype.Herdla. is gircn below, in con- front. A small glaciofluvial terracc marks the nection with the descriptior.rof the end mo- marine limit in Strandvik at that time (77 raines. m a.s.l.).

Hardangerf jorden - Strandvik Vinnes - Fusol jorden The maximum extension of the glacier irr On the Fusafjord side of the peninsula, the Hardangerfjordenduring rhc younler Dryas lateral moraines can be traced from Vinnes Stadial is marked by the large end rno.uin. along the mountain side up to 340 m a.s.l. crossingthe island of Halsnciy (Fig. 11) (Undis They are lacking on the northern side of thc 1963; H. Holtedahl 1967; Follestad1972). The mountain. The gradient of the fjord glacier is fjord sill west of Halsnciy controlled the posi- 50 m/km for the last 5.5 km. tion of the glacier front during this readvance Undis (1963:13) interpreted the moraines (H. Holtedahl 1967: 194). at Vinnes as having been deposited from thc Undis (1963: 12) has describeddistinct mo_ east by a glacier in Bjcirnafjorden. The Vinncs raines in the central part of island. Clay, 0-1 km southeast of the moraines was Here a brar.rchof the Hardangerfjorden glacier according to Undis, washcd out from the has been moving up-valley, causing gla- moraines after deposition. The Cra dating b]- ciolacustrine sediments to be interbedded in Mangerud r 1970tf rom Vinnes(T-594, fO.S70 i the till. The stcep mountain sides on the 180)made rhis doubrful. eastern side of Tysncs have no traces of a A stratigraphical analysis of a 27 m deep glacier margin, but on the slopes down to core in the VinnesCtay tAarseth I97l) shows Bjcirnafjorden lateral moraines occur both a contlnuous sedimentation from Allercid time. above and below the marine terrace at Hasen The lower half of the core, consistingof clayey (68 m a.s.l.t. In lhe deepesl part ol' Bjcirna_ silt and silty clay, is thought to be depositei BOREAS3 (1974) Younger Dryas end moraines 9

Fig" 4. Air photo of Strandvik towards NE. The headland made up of till in the foreground forms the moraine. The further courss of the moraine is indicated (dotted). The nunatak moraine is in the upper right (m). The location of the terrace indicating the marine limit (77 m a.s.l.) is marked in the center of the photo. Direction of glacier fiow is indicated by arrow. Photo by Fjellanger Widerije A/S, Sept. 1950.

before the readvance in the Late Younger that the Vinnes Clay lies distal to the Vinnes Dryas. This gives a mean rate of sedimenta- Moraines. If we consider the striae in the area, tion of approximately 8 mm/year. Above this the southern striation in Fusafjorden dis- sequence lies a zone containing the high-arctic appears only a few hundred meters north of mollusc Portlandia arctica. The sediments be- the Vinnes Moraine and is probably con- come more varied, containing layers of graded temporary with the moraine. The moraines sand-silt. One of the graded layers contain in Fusafjorden are described above in the sec- leaves of Betula nana and Salix herbacea tion on submarine areas. together with mosses, some of which today only grow in alpine regions (Ovstedahl & Aar- seth in prep.). These macrofossils all indicate Os area high-arctic conditions, and the graded layers The Quaternary deposits are more extensive are thought to have been deposited by floods in the Os area than in most other coastal areas from the glacier margin. The coarser material in Hordaland. The deglaciation of Os has was deposited at the glaciomarine delta at Dal- therefore been discussed by several authors, land (72 m a.s.l.). most recently by Undis (1963), H. Holtedahl Oedometer tests from two horizons in the (1964), and Mangerud (1970). core show normally consolidated sediment. In Fig. 5 a reconstruction is given of the This, together with the continuous sedimenta- ice front during the Late Younger Dryas. This tion of the Vinnes Clay and the Cla dating reconstruction is based on morphologically mentioned above, corroborates the statement evident ice-contact slopes and end moraines, 10 Inge Aarseth and Jan Mangerud BOREAS3 (1974) BOREAS3 (19'74\ Younger Dryas end moraines l1

Fig. 6. Air photo of Fanafjorden and Fanafjellet. The lateral morairie in the northern slooe of Fanafjell is indicated (dotted). Note the more extensive till cover on the inside (left hand) of the moraine compared with the outside. The approximate position of Marine limit (50 m a.s.1.)is in- dicated. From that point the (calving) ice front crossed the fjord, and the sediments in the foreground (Milde) are parts of the ice-front deposits on the northern side of the fjord. Photo by Fjeilanger Wider6e A/S, Aug. 1954.

while the maximum advance during Late reach the sea to the south, at Osciyri, but Younger Dryas no doubt reached a few hun- spilled out from the western flank of the lobe, dred meters further south and west. at Ulvensletta. The reason for this was prob- The directions of the glacial striae south of ably that the pressure from the glacier in the end moraines (Fig. 5) are oblique to the Fusafjorden caused a westward sloping of the direction of Fusafjorden, indicating that during glacier surface. the deglaciation in the Allercid the glacier flow According to seismic investigations, the did not adjust to tl're topography of the fjord, maximum 'the thickness of the glaciofluvial sedi- probably because deglaciation was very ments at Ulvensletta is 34 m, while in most rapid. This provides an independent method of areas the thickness is considerably less. This limiting the Younger Dryas advance to the sediment basin had a narrow connection with boundary between the two directions of striae. the sea towards SW (Fig. 5), where most of In Os there was a confluence of two glaciers, the fine-grained sediments were transported to one in the Os valley from Sdfteland and one the sea. The surfaces of the deposits form 'nunatak in Fusafjorden, separated by a large nearly horizontal terraces with an elevation of around Borgafjell (Fig. 5). The subglacial approximately 58 m a.s.l. at Ulvensletta and meltwater from the Os valley glacier did not 57 m a.s.l. at Grindavoll, indicating that the whole deposit was built up to sea level in the Late Younger Dryas. These figures are used Flg. 5. Paleogeographicalmap of the Os area (west for the construction of the isobase map (Fig. of Fusafjorden, Fig. 1) during Late Younger Dryas. 11). (19'.74) 12 Inge Aarseth and Jan Mangerud BOREAS3

ffi fxposedbedrock _.- Glacialsediments [,;,il on tand. (Partty redeposited)

a a Boulderbelts

| ,.', lce-contactslopes

,rrr_Mlio terrace- escarpment 32 Marine I l+ Echosounding profites at Fig.9

N

tl

Fig. 7. Simplified glacial map ol the Herdla area. Contours only below sea level. Depth in meters. The elevation on land does not exceed 50 m in the map area (Fig. 8). In the shallow area between the northern part of Herdla and Lille Angiiy, mainty marine sand is found on the sea floor, assumed to be redeposited glacial sediments.

Undis (1963) does not seem to have noticed Os - Herdla thesemoraines, and he assumedthat the posi- Between Os and Lysefjorden (Fig. 1) ,only tion of the ice front was a little further west. small deposits without clear ice-contact slopes Inside the morainesa (discontinuous)cover of are found. till is found, with an abrupt transition to naked At Fanafjell mountain, between Lysefjorden bedrock outside the moraines (Fig. 6). Obvi- and Fanafjorden (Fig. 1), are small, but very ously the till sheet was deposited simuita- prominent lateral-moraines, especially along neously with the moraines,thus proving that the northern slope (Fig. 6). Surprisingly enough, the advance did not reach further west. The BOREAS3 (1974) Younger Dryas end moraines 13

Fig. 8. Air photo of Herdla towards north. The dark forests in the central part of Herdla are mainly the bedrock areas, indicated on the map (Fig. 7). The cultivated areas are the glacial sediments. The conditions in the foreground, on Askiiy, are typical for most of the region discussed in this paper: Bare bedrock with some sediments (including peat) in the depressions only. Photo by Fjellanger Widerde A/S, Aug. 1961.

lateral-moraines slope 250 m for a distance of the bottom is very rough. Based on the given 3 km, indicating a steep glacier-front. observations,and in accordancewith the direc- In the Fanafjord - Raunefjord - Agotnes tions of the glacial striae, we assumethat the area (Fig. 1), some moraines have been found, glacier has been floating in , both on land and by echo sounding in the causinga fairly straight,calving glacier front. fjords, and even though the moraines are not continuous, the main trend should be correct. Most problematic is the position of the Herdla area glacier front in Hjeltefjorden between Agotnes The island of Herdla is, morphologically,the and Herdla. Dated Aller

3Km 2Km 0Km

SE

It

][

50

l00m

E

[, ,oo' J- as,umeo ice-contactslope bedrock \ \assumeo 2dangte of stope 9. lr-{a. l-lcho-soundingprofiles from thc-Hcrdla arca. For locationsee Fis. 7

narrow sounds between Herdlefjordcn and the depth of 130 m can be secn, but, on the Hjeltefjorden. Bedrock occurs in parts of the basis of the present observations,it is imoos- island (Fig. 7), while large areas are covered sible to determinethc border ol' the real con- by unconsolidated sediments. The surfaces of structional ice-contact slopc. No doubt, the the sediments are mainly terraces of different ice-contactslope is more than -50m high below elevations, thc highest being a slightly sloping sea level in several places, including profilcs, terrace ca. 34 m a.s.l. (Fig. 7). This possibly I, II and I1l (Fig. 9). reprcsents the marir-relimit and the sea level The sediments and stratigraphy are so far of the time of deposition(Late younger Dryas). known from a few sectior-rsand borines. The For the construction (Fig. of the isobases I 1), maximum observeddepth is ca. 30 m, 6rt *itl however, the elevation of 32 m, obtained from probably turn out to be considerably more. In a marked beach ridge, has been used. -foward the higher terraces the main sediments are the east are very clear ice-contact glaciofluvial and glaciomarine. Till is seen in slopes.These are directly observablefrom land, one section in the proximal slope. The block but are obviously even more prominent below belts indicated at the map (Fig. 7) are sup_ sea level, as can be seen from the echo- posed to have been cithcr depositecldirectiv sounding profiles (Fig. 7 and 9). On profile from the glacier, or most probably to be the III (Fig. 9) a smooth sedimentslope down to erosional remnants of till. Due to the pattern. BOREAS 3 (1e71) Younger Dryus end ntoraines l5

FENSFJORDEN NW S,AND6Y SE

200

400 400

60

?1

800 ' ' rB00 35 Km 30 25 ZO rS r0 5 0--- l-'ig. 10. Lotlgitudinal profilc of Fensfjor.den, based on .15 tr.ansrcrsal ccho sourrdings.Echo depth rn m. The moraine at Sandoy, immedialcly north of thc sill, is indicatetl.

we assumc they indicate thc ice front position the ice flow (from SW) south of thc mountain in certain periods. During the Holocene an rvasthc more imporlant. extensive littoral erosion and redeposition of the glacial sediments took place, as indicated jorden - by the lower terracesand sediments. Mangersf Fensl jorden So far only one radiocarbon date has been The area between Mangersfjorden and Fcns- obtained. In the western part of the island fjorden is mainly a part of the low-lying (Fig. 7) large specimensof Mya truncota were strcrndllat,most of which was submcrgedduring found in shelly sand immediately above bed- this readvance. The moraines are therefore rock, close to the present day sea level. Above mainly made up of glaciomarine silt and clay, the sand is ca. 20 m of glaciomarine sedi- consolidatedby the pressureof the ice. During ments, mainly silt, and on the top 8-10 m of the postglacial emergencethese moraines were coarse glaciofluvial gravel. The dating gave exposed to marine abrasion. This resulted in the age (T-1049) 10,5401130 B.P., indicating resedimentationof silt and clay in the depres- that the whole sequenceabove was deposited sions. In the Fosnciy area the moraines consist during the Upper Younger Dryas. of two parallel ridges, at most 1 km apart. The deposits at Herdla continue below sea The submarine moraines in this area are also level northwards to Lille Agnciy (Fig. 7) and very small. The straits have usually two or Holsnciy. The submarine deposits here are three ridges, 5-10 m high. In the 400 m deep possibly as thick as the sediments at Herdla. Mangersfjorden, the bottom topography Probably Herdlefjorden has drained meltwater changeswestwards from a narrow trench to a from extensive areas, depositing the large wide sediment basin at the supposedmargin of amount of glaciofluvial and glaciomarine sedi- the glacier. ments at the ice front. Fensfjorden has been subject to a special Glaciomarine terracesand end moraines are marine geological investigation (Aarseth & also found at the island of Holsnciy, indicating Myhre in prep.). A longitudinal profile of the the position of the ice front. Just inside the fjord is shown in Fig. 10. The 385 m deep sill moraines is a more than 300 m high mountain south of the island of Sandciy most likely has (Fig. 1), without lateral moraines. The glacial a bedrock core, but the morphology indicates (Fig. striae 1) indicates that the ice first a considcrable sediment cover. The sill is reached the moraines from NW, while later located between well-defined moraines on land 16 Inge Aarseth and Jan Mangerud BOREAS 3 (1e74)

both to the south and north, and the sediment the dominating glacier in this fjord, which cover on the sill is therefore probably a part caused the ice movement throueh the sounds of the end moraine. north-eastof Sula.

Sognet'jorden zrea CIadatings The moraines on the island of Sandiiy (Fig. 1) are very distinct both above and below the The dated materials are in nearly all the marine limit which is marked by an abrasion localities marine shells. For the mcthod the terrace at Anneland, 35 m a.s.l. The moraine reader is rcferred to Mangerud (1972a). All drops 200 m the last km down to the terrace. ages are given in convcntional (Tt/2: -5570) The same steep glacier front is also indicated radiocarbon years B.P. by the moraines on Mjcimna. Fossil-bearing tills havc been known in the Thc clcar morphological evidence of an ice Bergen area for a long time (Rckstad 1900; front deposit suddenly disappears north of C. F. Kolderup 190t3).The first Cra datings of this island. Only small boulder accumulations the tills were obtained by Undis (1963) and occur on some of the islets. The sounds in H. Holtedahl (196,1) and gave Allercid and bctween have no marked traces of an ice front. Younger Dryas ages, thus proving that the The same lack of clear end moraines also Younger Dryas end moraines had to be found charactcrises the area just north of Sogne- west of the dated localities. Later many more fjorden. According to Undis (1963:23) mo- datings giving the same ages were obtained raines on Ytre Sula and r,vestof Steinsund(Fig. from till and sub-till sediments(Fig. l) (Mange- 1I ) belong to this ice advance.This is a several rud 1970, 1972b, Aarseth 1971). The geo- kilometer broad belt of boulders with only a graphical distribution (Fig. 1) of the overridden few small ridges. The first sign of a well- sediments indicates a great ice advance during defined ice front deposit north of Sogne- Younger Dryas (Mangerud 1970), and obvi- fjorden is a 7 km long, continuous end moraine ously the end moraines must be situated out- along the mountainsof Sula, from 360 m a.s.l. side the area of overridden sediments. Theo- down to sea levcl. retically, however, the moraines could be The discontinuity of the moraines around situatedfar outside the known localitiesof these the mouth of Sognefjorden is most likely a sediments, and a position outside the coast result of an unstable glacier front. The 275 m (H. Holtedahl 1964) was a very realistic deep sill southeastof Ytre Sula is thought by alternative. Undis (1963:23) to be the Ra Moraine in At Blomciy (Fig. 1), Mangerud (1970) ob- Sognefjorden. Echo soundings from the area tained several datings of Allercjd age frorn a show a sediment cover over the threshold. but bog undisturbed by ice, giving clear evidence the lack of continuation ashore makes the that the Younger Dryas advance did not reach assumption by Undis doubtful. Most likely that island.He (Mangerud 1970) also obtained this accumulation was deposited as a reces- a dating of museum specimensfrom the Vinnes sional moraine at the fjord entrance while the Clay (Fig. 1), giving the age ('I-591) I0,97Ot glacier obtained equilibrium during the Al- 180 B.P. and Aarseth (1971) found that the lerciddeglaciation. clay had not been consolidated by ice. Also at The extensive clay deposit north of Dals- Agotnes (Fig. 1) a dating of marine sediments fjorden with Portlandiu arctica (Kaldhol 1941) (T-1023, 12,250+150) undisturbedby ice has indicates a glacial environment at the time of been obtained. Finally we can mention the deposition. Thc glacier front must have been previously discussed dating from Herdla (T- situated south of the fjord where large end 1049, 10,540r 130), which indicates that the moraines are found at Fure. There are two Herdla Moraine is from the Younger Dryas. parallel ridges. the innermost can be traced Fig. 1 shows that there is only a narrow for a distance of l0 km, partly as a submarine zone between the area with sediments over- ridge. An abrasion terrace at 27 m a.s.l. marks ridden by the ice advance during the Younger the marine limit in this area. Dryas and the localities with sedirnents un- The change in ice front direction north of disturbed by the same advance. In this narrow Sognefjorden (Fig. 11) was probably due to zone we have mapped the Herdla Moraines, BOREAS 3 (1971) Yourtger Dryus end nloraines 17

.-4$"1&:ft#'#:*,i'. i ,'ffi{fiffff'f\}*h,i

. t.t. i\ p o \ir[

BERGEN NORTH SEA

t- '0' \E

q?{( i - Younger Dryas lsobases {r L)o,t Younger Dryas sobases - - - eilrapolated nside lhe odt morat nes o ?? Localitvrnd elelal on of r\ o"_ Young6r Dryas marrne lerraces n metres Younger Dryas end- -..-..- moraines souih of Sognetjorden(Fig I )

. End mora nes north of .r"" Sognefjorden {j'f <:rI Fig. 11. Isobasemap of the End moraLnes norlhof ^^/ Younger Dryas sca level rn Sogneljorden acc a.^ the area bctween Hardanger- lo UndSs (t963) fjordcn and Dalsfjorden.The moraine south of Hardanger- Ijorden is accordingto Folie- stad ( I 972).

2 - lforeas 1/74 BOREAS3(911) 18 Inge Aarseth und Jun Mattgerud

B.P' and although these in most places are small fjorden was deglaciatedbefore 9720+330 and not fully continuous, we do not doubt that (T-585) (Anundsen & Simonsen 1968), and they represent the Younger Dryas moraines the head of Sognefjorden before 9790+160 between Hardangerfjorden and Sognefjorden. B.P. (T-901) (Bergstrcimin prep.). The retreat the The next problem is to obtain more precise of the ice front from the coastal areas to time, dating within the Younger Dryas of the Herdla head of the fjords necessarilytook some the Moraines. The northernmost dating (Fonnes, and these datings therefore indicate that Fig. I) was obtained from sediments inter- retreat from the Herdla Moraines must have preted to be glaciomarine clay, thus indicating started very close to 10,000B.P. that the ice front was approaching at (T-1168) 10.770t 140 B.P. The dating from Herdla indicates that the whole moraine was deposited Sealevel after (T-1049) 10,540* 130. In the Os area (Fig. 1) ages of (T-752) 10,790+110 and In Western Norway the problem of shoreline I-22q 10.150+300 were obtained from tills displacement during Late Weichselian and j close to the end moraines,and (T-30'1)10,050 Holocene time has been difficult because of 250 from clay overridden by the ice, showing the uncertainty of the isobases.In the Sogne- has that the ice reached Os very late in the fjord area the direction of the isobases (along Younger Dryas. Further south (Lunde' Fig. 1) been supposedto be N-S the coast) by (T-847) 10.570+100 was obtainedfrom a till. severalauthors (Brathole 1951; Kyrkjebcj 1953; (1963) the Assuming that the Younger Dryas Stadial Carlsson 1960). Undis constructed lasted from I0,900 to 10,000 Cl4 years B.P' 60 m isobasesouth of Bergen, but due to some (Mangerud 1970), these datings clearly indicate obviously wrong interpretations he obtained (N in dif- that the Herdla Moraines are of Late Younger different directions 17 W-N 34 W) (Undls 1945) Dryas age. Actually there is a possibility that ferent areas.In a previous paper of the glacier was advancing to the very end of just north of Bergen he used a direction the Younger Dryas and did not reach equilib- N 2 W without discussingit. rium until the climatic amelioration. The latest attempt to construct a shoreline A further possibleinterpretation of the dates diagram in a part of this area is by Follestad is that the ice first reached the position of the (1972). His assumption of the three base local- moraines in the northern area - compare the ities in the outer part of Hardangerfjorden as re- interpretation of the date from Fonnes - and contemporaneous marine limits must be a later the position in the more southern area, jected. The terrace at Skinevik, 83 m a.s.l. is at Herdla and especiallyOs' This interpretation pronounced wave-cut platform in the moraine, level is in accordance with all datings obtained so representing the Younger Dryas sea U3 m far, and is also glaciologically reasonable' (Anundsen 1972: 1.3).The terrace at Eik, North of Fensfjorden are high mountains, a.s.l.,is very small, and a marine formation is continuing eastward. Analysis of glacial striae not obvious. In addition it is situated 20 km indicates that these mountains have been an inside the Younger Dryas moraines at Halsnciy. important accumulation area, influencing the The terrace at Onarheim, 70 m a.s.l', is known ice flow south to Fusafjorden. lt is therefore as a bedrock terrace (Kaldhol 1941), probably very likely that the glaciers reached the Fens- the upper edge of the Strandflat. This terrace fjord area before the coastal areas further is therefore definitely older than the events south. This interpretation is, however, based discussedhere. on very few datings, and should only be re- The terraces used for construction of the garded as a reasonablehypothesis. present isobasemap are clearly connected with So far the younger border of the Herdla the moraine itself, either as abrasion terraces Moraines has not been discussed.Mangerud on the distal side of the moraine or as ac- and his students have obtained some pollen cumulation terraces which were built up by diagrams from Preboreal sediments inside the drainage from the glacier front. The various moraines, including a radiocarbon dating giving localities are mentioned in the description of (T-1487) 9760i 180 B.P. (Aa, pers.comm.), the moraines. The levels refer to the present which indicate that the deglaciation started day mean sea level. Most of the terraces are early in the Holocene. The head of Hardanger- relatively flat, but some have slightly undulat- BOREAS3 (1974) Younger DrYas end ntoraines 19

to Marthinussen (1961) ing surfaces. The heights are therefore given indicated according (1968), in Sweden according in whole meters as the variation in level is of and Andersen (1965) and in Finland according this order. to Lundqvist (1965) Hyvdrinen (1973)' The Herdla Moraines have a general course to Donner and problems appear concern- along the coast, and over long distances they However, several precise chronostratigraphical cor- are situated on the low-lying Strandflat, and ing a more Younger Dryas end moraines: very few terraces are found. Only in the relation of the southern part of the area can both the direc- the tion of the isobases and the gradient of (1) The end moraines, even though continuous, shorelines be constructed' This gives a direc- are not necessarilydeposited simultaneous- mTkm tion of N 13 W and a gradient of 1'4 ly in their full length. in Bjtirnafjorden area (Aarseth 1971)' (2) Dating of end moraines is often difficult' In In the area, just north of the area fact surprisingly few Cla dates are closely covered by Fig. 11, the gradient of the well- relatedto the Younger Dryas end moraines defined Main shore line, correlated to the in Scandinavia. Younger Dryas ice advance, is 1.1 m/km (3) The level of correlation is very precise'The (Fareth 1970). For construction of the isobase duration of the Younger Dryas is tl00-900 map (Fig. 11) an interpolation of the gradiert years, and the discussionis now concerned between these two areas is necessary'Thus the with ascertaining in which part of the m/km gradient is assumed to drop from l '4 Younger Dryas the different moraines were in Bj,iirnafjorden to 1.2 m/km in Dalsfjorden' formed. We are therefore very close to, or two This agrees well with the elevation of the beyond, the precision level of Cla dating' terracei in this fjord, at Fure (27 m a's'l') and Dale G7 m a.s'[.). One feature is, however, very striking: Ir-r Norway the Younger Dryas end moraines con- sist of one ridge, or a few ridges very close to Correlations each other. Close to the Swedish border, the up and The Middle Swedish The dating of the Herdla Moraines to the Ra Moraine splits of several,usually smal[, Younger Dryas makes the correlation with End-moraines consist other Younger Dryas moraines more or less ridges. disagreement exlsts con- obvious. ancl this correlation was established In Sweden some of the Middle Swedish by Mangerud (1970)' cerning the definition (Mcirner 1970). It is, however' At present a morphostratigraphical correla- End-moraines parts several moraines tion is also possible, as the moraines are clear that in western eastern parts the ice front mapped nearly continuously south of this are found, while in cnd moraines' area (Andersen1954, 1960; H' Holtedahl 1967; retreatedwithout depositing between Hardanger- Anundsen 19721 Follestad 1972) to the Ra In the present area, a significant ice Moraines in Eastern Norway. The morpho- fjorden and Sognefjorden, have taken place during stratigraphicalcorrelations of the Ra Moraines, advance is proved to and the Herdla Moraines the Middle Swedish End-moraines (Lundqvist the Younger Dryas, Younger Dryas, between 1965) and the Salpausselk[ Moraines in Fin- are dated to the Late possibly only between land (Donner 1965) are also generally accepted' 10.500 and 10,000, and B.P' We have compiled a map of the Younger 10,200and 10,000Cl4 Years probably no significant Dryas end moraines in Scandinavia (Fig' 12)' ln Eastern Norway the Ra Moraine is The end moraines in Southern Norway are advance occurred, arrd deposited through the indicated according to compilation in Mange- thought to have been (Feyling-Hanssen 1964: rud (1970). with additions from Anundsen whole Younger Dryas 75-78). (1972) and Follestad 19'72) in the area south 1,72-1'75;Andersen 1968: correlations of the of Hardangerfjorden, from the present paper The chronostratigraphical moraines in Sweden, in the area between Hardangerfjorden and Younger Dryas end Norway therefore appear Sognefjorden and from Fareth (1970) in the Eastern, and Western 13' In this connection Nordfjord area (for location' see key map' to be as shown in Fig. Moraines in Northern Fis. 1). The moraines in Northern Norway are the Tromsci-Lyngen 20 Irtge Aurseth und Jun Mangerud BOREAS3 (1974)

l

"-\ '',i \ .-\ rr -. I \ '" iirr-'! .+ il \..-/ )/ l- \r'J \/"il, II r !/! f: fi -If-" L f 1l 1," l"' ,,i\ \!r tsoREAS (r971) 3 Younger Dryas end ntoroines 21

MORPHOSTRATIGRAPHY Clayears CHRONO- BP. STRATIGRAPHYWESTERN EASTERN SWEDEN NORWAY NORWAY

HOLOCENE

r0000 Bittingen Herdla

Lrl (J z. YOUNGER Skovde o

I IU DRYAS O

Taberg

r1000

ALLEROD

hig. 13. Chlonostratigraphicaland morphostratigraphical(dashccl) correlations of Younger Dryas cnd moraincs in Swcdcn altd Easlern and Westcrn Nolay. tslack: Most probable agcs. Dottc4: Possiblccxtension. Age of Ra Moraines according to Fcyling-Hanssen(1964). Moraincs in Sweden according 1o Mirrner (1970).

Norway might also be mentioned. These were Foundation and The Norwegian Research Council no doubt partly formed during the Younger for Scicnceand the Humanities (NAVF). Thcsc investigationswele startcdby .ud,who Dryas, but possibly the deposition started al- mapped thc area betwcen Fusafjorden and Mangcrs- ready early in the Allercid (Andersen 1968: f.iordcn.In his thcsis,Aarseth (1971)mappcd the area 71-7 5). furthef to thc southeastunder the guidance of Mange- rud. The method of mapping thc submarincmoraincs was devcloped by Aarscth, who carricd out all the submarine investigations from thc research boat llarrs - .4ckrtov'ledgenter?/s. We both wish to cxpress our Rettsch.The mapping north of Mangerrsfjordenand gratitude 1o Mr'. Kjcll Siigncn for assistanceat sca, the isobasemap wete done by Aarseth. The Cr1 intef- Miss Ellen lrgens for drawing the maps and figures, pretationsand thc corrclationswcrc donc by Mange- and Mr. James for helping with the language. rud. The authorshave written thcir respcctivechapters, Thc work was financiirlly supportcd by thc Nanscn but both are responsiblefol the results. tsoRL,AS 3 ( 1974) 22 Inge Aarseth and Jan Mangerud

Report on Riostrutigraphic Llnits' 50 pp' 24th Int' RL,FE,RENCF,S Ccol. Congre:s'Montrcul. Int. Subcom. StratigraphicClass' l97lb: Prelirnittury Aarseth, I. 1971: Deglasiasionslo116peti Bjdrnaliords- (un- Report on Chrotrostratigrttphic I)nits' 39 pp' 24th ontrdtlet, Hortluland- Thesis, Univ' Bergen Int. Geol. Congress,Montreal' published). Int. Subcom. Stratigraphic Class' 1972: Introduction Aarscth. L & Myhre, L. A. (in prep ): Morphology to an InternationuiGui.l" to StratigraphicClassifica- and sedimcnts in Fensfjorden, Western Norway' tion, Terminology, and Usage. Lethuiu 5, 283-295', Andersen. B. G. 1954: Randmorener i Sorvest-Norge' fotanot, H. 1941: Terrusse-ttg strandlinierndlingerlru Norsk geogr. Titlsskr. 14, 274-342' Sttnnljorcl tit Rogalund.206pp' Hellesvlt' e. C. tSeO: Sorlandet i Sen- og Postglacial Andersen. of a conventionalecho-sounder 210,142 pp' fing, L. H. 1967:Use ticl.Norges geol. Llnders. sedimcntatl Weste,rn uid t"*t.l.ul analyses in delineating Andersen, g. C. l96g: Glacial geology of - 256' facres.Canadian Iount. Earth Sci'1,691-'708' Troms, North Nolvay- Norges geol' Unders' fir,g,--JJpotltt f-. H. 1969: End molaines and associatcd 160 PP. on the Scotian Shelf' Geol Soc' Am Brill Anundscn, K. & Simonsen, A' 1968: Et -preborealt og i omr'6dct meilom 80, 83-96. brcfram.stdtpi Hardangervidda og tilstotcnde Bt'rgettArbok' Koljcrup, C. F. 1908: Bcrgcnsfeltet SatgantUon"nog Jotunheimen,Llniv' Mtts- traktei'i senglacial og postglacial titl' Bergen Mdt-Natltryit.Ser. 1967:7,42 PP' parts of Arb. 1907:14,268 PP. Anon.l,r"n, K. lg72'. Glacial chronology in N. H. 1926: Bygningen r\ moricrlel og Norway. Norges geol' Urders' 260' Kolclclup, south-wcstern Stirfjorden ved Bcrgen' Bergcrt r f/ t".r"rra-. i Oster- og I Mus. Arbok. Nutur\'. rekke, l-71 Bcr'{:trdm, B. (in prep.): Deglaciasionsfor{dptet N. H. 1938: Herdlalrinnet, dc ylterste A"urlanclrdrlcnog omlidellc omkring, Vest Norgc' Kolderup,--gi".i"fj"g i Bergensfeltct.Norsk geol' Tidsskr' 17' N orgas ge,il. U ndrrs. undersijkelser t 203-207. Brathic, A. 1951: Kvartergeologiske Hdyurtgerontra- (unpublished)' Kyrkjebij,-dei A. 1953: Geonnrlologi lra Intlre . Thesis, Univ. Oslo Sogn' kritrg og'srrumllinie- og isttt'snteltningsstrtdierlra Car-lsson,e. t96O, Isttvsmiiltningeni trakler1a Stock- Thesis, Univ. Bcrgcn. Sogneijortle,, ruuler sistuistirlerr. Thcsis, Univ' ln t-urulqvist, J. 1965: Thc Quaternary of Swcden'. holm (unPublished). Thi giaternury, Vol. l, London, IntcrsciencePub- Donncr, J. J. 1965: The Quaternary of Finland In Pub- lishcr:, Inc. | 39-l 98. The Qtturernary,Vol, 1, London, Interscience Maisey, G. H. 1968: Geornorlologiske og nraringeolo' lishers, Inc. 199-272. pisie ttndersiikelser i og omkring Ruttneljortlett' Fareth, t). W. 1970: Breruntlstadier i nidtre og irdre (unpublishcd).' Hordalantl. Thesis, Univ. Bergerr (unpublishcd)' N ordI jo rd. Thesis.Univ' Bergen Mangelud, J. 1970: Late Wcichselian vcgetation irnd Fcyling-ilanssen, R. W' 1964: Foraminifera in Late icelfront oscillations in the Bergcn District, Wcstcrn t)u"i"tn"ty deposits from the Oslofiord atea Norges Norway. Norsk geogr- Tidsskr' 21, 121-148' geol. llttJts 225' .183PP. Mangcrud, J. 197):d: Radiocarbon dating of marine Flint, R. T. l97l: Gluciul attd Qttdlerttury U(otogy' inits, incluoing a discussionof apparent age of 89i pp. John Wiley & Sons,Inc. New York'- Recent shellsfrom Notvay' Boreus l, 143-112' Follestai, B. A. 1972: The deglaciation of the -south- Mangerud, J. 19'l2b: The Emian lntelglacial and the westclri part of the Folgefonn peninsula, Hordaland' successionof glaciations during thc Last Ice Agc Norgt'sgeol. L)ttLlers. 280, 31 64' '6. (Weichselian) in Southcrn Norway' Amhio Spe' Frye,'i. & will-"n, H. B' 1962: Morphostrati- Rep. 2, 39-44' Univ. Fdrlaget, Stockholm' graphic units in Pleistocene stratigraphy' Rul' Anr' J. 1973: Kritisk ot'ersikt over slratigrulisk Ass.Petr. Geol 16, 1I2-l 13' Manierucl, ter-tninoiogi og klussilikasiort uv Kvarter i Norge' Holtcdahl, H. 196'1: An Aller