Overconsolidated sub-till clays in Herlandsdalen, lower Numedal, south Norway
ELEN ROALDSET
Roaldset, E. 1980. Overconsolidated sub-till clays in Herlandsdalen, lower Numedal, south Norway. Norsk Geologisk Tidsskrift, Vol. 60, pp. 39-51. Oslo 1980. ISSN 0029-196X.
A description is given of overconsolidated sub-tiU day sediments situated about 260 m a.s.l., i.e. 90 m above the 1ocal marine limit ofi the last deglaciation. The clay sediments contain neither macro- nor micro-fossils. Textural, mineralogical and geochemical investigations, strongly supported by the Ce deficient lanthanide abundance pattern, indicate marine depositional environment. The clay sediments are assumed to be of Middle-Weichselian age and are thus correlated with the Sandnes Interstadial, described from SW-Norway, and its analogues. E. Roaldset, Institutt for geologi, Universitetet i Oslo, Boks 1047, Blindern, Oslo 3, Norway.
In the Numedal river basin sub-till sediments The bedrock consists of Permian monzonite have previously been described from the north and alkali granite of the Oslo lgneous Province. em parts of the area (Roaldset 1973a, Rosenqvist Precambrian rocks occur about lO km WNW of 1973). This paper presents data on the ftrst sub Herlandsdalen (BrØgger & Schetelig 1923). till clays in the lower part of the Numedal river basin, where in 1973 in the valley Herlandsdalen, The Herlandsdalen sediments overconsolidated sub-till clays situated 260 m a.s.l. (Fig. l) were discovered. The sub-till clay was exposed near the head of Herlandsdalen (Fig. 2). The exposed sections are shown in Fig. 3.
Geological setting The Locality l sediments are glacially tectonized and display small fissures and faults. Well A sketch map of the superficialdeposits, given in rounded pebbles of Precambrian rocks are scat Fig. 2, shows thick till cover in the SW, and thin tered throughout the clay bed, becoming more discontinuous cover of till NE of Herlandsda abundant upwards. A 30 cm thick bed of silty len.Dead ice terrain is locally developed, and at sand succeeds the elay, with distinct contact to K viberg-Olsli a glaciofluvial delta was deposited the bluish grey zone above. This zone, being a and built up to the postglacial marine limit (173± mixture of clay and till material, gradually 2 m a.s.l.; KorbØl 1972), simultaneously with changes over to a yellowish brown till. Frag deposition of marine clays in the ancient ments of rock as well as of consolidated clay 'Numedalsfjorden'. Accordingly the sub-till occur in the til!. clays are found almost 90 metres above the post-glacial marine limit. The Locality 2 sediments consist of homogenous The main directions of glacial striae, as fine grained clay in distinct contact with alkali observed north and southeast of the Herlandsda granite below, and till above. The elay shows no len area, are N 100c and N 160c - 110c respec sign of glacial tectonism or disturbance, and is tively (Holtedahl & Andersen 1960, D.E. Nilsen presumably preserved in situ. The till is fur pers. comm. 1978, K. Pederstad, pers. comm. rowed by small channels (5-20 m wide, 2-10 m 1978). Like the valley innfills of till in valleys deep). The coarser till fragments consist of well tributary to Gudbrandsdalen (Mangerud 1965, rounded cobbles of Precambrian rocks. Frag Garnes & Bergersen 1977), the preservation of ments of Lower Palaeozoic or of Permian rocks till in SW-areas of Herlandsdalen may be ex were not identified in the coarsest fractions, but plained by their lee-side position during ice flow occur in small amounts, below 10 per cent in obliquely across the valley (Hillefors 1973). total, in the grave! fraction. 40 E. Roaldset NORSK GEOLOGISK TIDSSKRIFT l (1980)
o
o
o
- �ls SKI 19800- 9900 BP l
RA 110200 BP)
20km
lOO m.a.s.l.
Fig. l. Oslofjorden and the location of the Herlandsdalen area. The 300m contour is indicated. Terminal moraines from the last deglaciation are indicated with broad black lines.
Fig. 2. Superficial deposits in the Herlandsdalen area (KorbØII972, unpublished data, Numedalsprosjektet, Institutt for geologi, Universitetet i Oslo). NORSK GEOLOGISK TIDSSKRIFT l (1980) Sub-ti/1 clays in Numedal 41
Bedrock with small areas eovered by lill
Thin cover with tiU
Thick cover with un
Glaciofluvial gravet and sand
Fluviat sand
Bog
- Eskor
Orainag.e ehannel
Glaciofluvial terrace
SOm
HERLANDSDALEN
SOOm 42 E. Roaldset NORSK GEOLOGISK TIDSSKRIFT l (1980)
Loe. 1. Loe. 2.
M o M
o Ablotion lill lill
Till 2
2
Till/Cloy 4 Sand
4 Silt y Cl a y clay 6 * 7Tf////J/////////////77; Slumped 6 mot•rial not excavat•d ?r!!!!!!!!� Alko li +++++++++++++++++ 8 +++++++++++++++++ gronite
Fig. 3. Sections through the till and clay sediments. The clays are bluish grey and the tills yellowish brown. Asterisks show the sample positions. At Loe. l (disturbed) the clay in the upper parts contains well-rounded pebbles ofPrecambrian rocks. The sand bed rnay represent a fluvial or glaciofluvial event.
Neither macro- nor microfossils were detected methods of mineral identification were essen in clay samples prepared for pollen, foramini tially based on Brown (1961). fera, and diatom analysis. The major elements were determined by X-ray Sediment texture and particle size distribu fluorescencespectrography (XRF). Ferrous iron tions are illustrated by means of electron was determined by dissolving the sample powder micrographs in Fig. 4. The Loe. 2 clay shows a in cold concentrated HF with subsequent col great abundance of <2 �-tm materials with a few orimetric titration against K2Cr207• The igni scattered coarse fragments, while coarser frag tion loss was determined as the weight loss of ments dominate in the Loe. l ela y. material dried at ll0°C after heating for 2 hours at 1050°C. The relative distributions of lanthanide (Ln) Experimental methods elements were determined by a modified GEC/ AEI MS 702 solid source mass spectrometer pH measurements were carried out in situ, using (Taylor 1965, Nicholls et al. 1967 ). A description a Beckman H5 pH-meter and a combined glass of the analytical procedure is given by Prestvik calomel electrode. & Roaldset (197 8). Christie (1977) showed that The clay samples were examined without any the precision of the method is 8 per cent, the pretreatment with a JEOL scanning electron accuracy within sample is 10 per cent and the microscope. accuracy of the method, which is a measure of Geotechnical parameters were determined by reproducibility of sample preparation, conventional methods according to Skempton homogeneity and precision combined, is 25 per (1953). cent. Material coarser than 63 �-tm was wet sieved employing screens of whole phi unit intervals, while the grain size distribution of the fine frac Results and comparisons tion was determined by pipette analysis (Krum pH-measurements bein & Pettijohn 1938). Mineralogical analyses of the clay-sized frac In sit u the pH value was 7.5 for the sub-till clays, tion (finer than 2 �-tm) were made with oriented which is of the same order as for Scandinavian samples by X-ray diffractometry (XRD). The postglacial marine clays isostatically lifted above NORSK GEOLOGISK TIDSSKRIFT l (1980) Sub-till c/ays in Numedal 43
Fig. 4. Sub-tiU clays. Scanning electron micrographs of horizontal sections: Loe l. A- 300X, B- 3000x; Loe 2. C- 300x, D-3000x. sea-level (J. Moum, pers. comm. 1973), and therefore assumed to be greatly overconsoli higher than normally found for Numedal tills dated. The clays did not shrink with further (unpublished data, Numedalsprosjektet, Institutt drying, which proved that they have been con for geologi, Universitetet i Oslo). solidated to beyond the shrinkage limit, which is normally 15-20 relative per cent beyond the plastic limit (Hogentogler 1937). The following Determination of consolidation stress considerations and calculations are analogous to The sub-till clays had a considerable hardness those made by Rosenqvist (1973) for the and did not crack during drying. They were FønnebØfjord sub-till clay in upper Numedal. 44 E. Roaldset NORSK GEOLOGISK TIDSSKRIFT l (1980)
Table l. Geotechnical parameters for � than the estimated load of 1000 tons/m2 for sub-till clay (Loe. 2, undisturbed). FønnebØ clays, upper Numedal (Rosenqvist 197 3).
Water content (WJ 14.9 ' Obviously the eonsolidation stress for the
P1astic limit (W ) 17.3 ' P Herlandsdalen sub-till clay was much higher Liquid limit (� ) 32.3 ' than the weight of the overlying till, and it is \' o. 40 Void ratio (e) unlikely that this material alone eonsolidated the P1asticity index (PI = W -W ) 15. o ' L P sediments. Thus the consolidation is due to an COntent of Clay < 2 lJm (c) 55. o ' overlying glacier with a thiekness of at least ACtivity (A = Pl/C) o. 27 7--800 m. This must correspond to a major glacial advance. l)Calculated on the basis of a specific qravity of the
particles of 2. 7 g/cm3. Grain-size characteristics The grain size distribution was plotted as weight The fundamental geoteehnical data for the in per cent (log probability scale) versus phi (
99.5 " . 99 ,, 98 11 : ; l : 97 , l : 95 ...�' ! 95 90 .,"',... ' : ...... 84 80 Ti li C loc.t) ...... ,' "' "' · 75 70 '\.. .". ." ..·· ��...... 60 ...... · ,��-"'.., . ······ · 50 \. . 40 ··' r f' . , .. 30 . " ' Sand ( loc.l) 20 ".""' /' / .... 16 ,. "' 10 , "" .," ,. "', ,...... ' : ,.-' , Till ' 0- units NORSK GEOLOGISK TIDSSKRIFT l (1980) Sub-till clays in Numedal 45 Table 2. Sorne standard size and particle distribution parameters (Folk 1 Ward 1957) for the Herlandsdalen clay and till. Loe. l Loe. 2 Measure Sub-til l Sand Till Sub-til l Til l ela y ela y Graphic rnean l) 7.3 0.16 2.8 10.0 2.3 sorting (Inclusive 3 graphic 2) .4 1.2 3.0 2.9 2.7 standard deviation) Skewness (Inclusive raphic 9 - 0.18 0.14 - 0.08 - 0.08 31 0.5 skewness) ) Graphic 4 0.62 kurtosis 1.00 1.14 0.96 l. 21 (Peakedness) 3 l) ) + 4>s �9 2 11 "' �16 + �84 - 2�50 + 5 - �50 z Sk 1 2 - 1 2) 4) s - = 95 : 4>16 - 4>8.4 Loe. 2. Clay, very poorly sorted, near sym diffractograms. The clay beds differed from the metrical mesokurtic. eoarser sediments but were similar to each Till, very poorly sorted, near symmetri other. For this reason only the X-ray cal leptokurtic. diffraetograms for the Loe. 2 clay and till are presented (Fig. 7). The in situ clay is finer than most marine clays The phyllosilicates present in the clay frac around Svarstad (KorbØI 1972), and similar to tions of the tills and the sand bed are illite (lOÅ), the most fine-grainedmarine clays in the Skager vermiculite, and a mixed layer illite-vermiculite rak (RØnningsland 1976), and sub-till lacustrine (l0-14Å). In addition mierocline (3.25Å), clays of central South Norway (Rosenqvist 1973, plagioclase (3.19Å), amphibole (8.4Å), quartz Vorren Roaldset 1977). The tills have grain & (4.26Å), and small amounts of smectite were size distributions typieal for basal tills of the detected. After treatment with HCl the 7Å peak surrounding area (KorbØI1972). disappears, thus eliminating the presenee of ka By plotting sorting (u1) versus mean grain size olinite. (Mz) for late- and postglacial sediments of the The sub-til! clay eonsists of illite, chlorite Svarstad area, a clear distinction appeared be (l4Å) together with traces of smectite, and tween marine clays, tills, fluvialsand, and grave! mixed layer illite-chlorite minerals. Besides th (KorbØl 1972). The Herlandsdalen samples fit ese, amphibole, quartz, mierocline, and this division. The overconsolidated clays and the plagioclase are present. Not in this material sand plot within the areas for marine clays, either was a 7 Å kaolinite peak observered after glacio-fluvial sediments, and fluvial sediments HCI treatment. The X-ray diffraetogramsfor this respectively (Fig. 6). clay resemble the diagrams obtained for river mud and some till samples from Numedal (Roaldset 1972) as well as marine Skagerrak Clay mineralogy clays (RØnningsland 1976). The clay fractions (< 2 J.tm) of the tills and the Treatment of the < 2 JLm material with sand bed gave almost identical X-ray sodium-tetraphenyl-boron (NaTBP) revealed in 46 E. Roaldset NORSK GEOLOGISK TIDSSKRIFT l (1980) o lill o Glaciofluvial (?) • Sub-til l elay 1 Loc.1 4 / MARINE / 2 Loe 2 2 SEDIMENTS l e l l l 1 / TILLS l 3 . l l l l l l l - l --- 1 ------__ _ ,_ -- - _ 01 GLACIO- FLUVIAL AND FLUVIAL SEOIMENTS Fig. 6. Plot of sorting (inclusive graphic standard deviation) ver sus graphic mean. The divisions were obtained for different sedi -2 8 6 4 2 o o ment types from the lower 1mm Mz 2p 63 fl Herlandsdalen - Svarstad region Effective diameter (after KorbØI 1972). 71 841 10A 141 3331 3 JJl Ti li ( fr•ction Sub- lill elay C fraction < 2 �) Glycol 4so•c Fig. 7. X-ray diffractograms of the clay fraction (<2p.m) of the overconsolidated clay and the overlying till (Loe. 2). both cases the illites to be of di- and trioctahedral opposite distribution of vermiculite deserves at type (DeMumbrum 1%3, Robert 1973, Schmith tention. According to Garrels & Christ (1965) & Scott 1973, Rueslåtten 1976). chorite is stable in marine environments, but The Jack of chlorite in the till and its appear unstable in weakly acidic ones. The high content ance in the underlying clay samples and the of vermiculite minerals in the till can be attri- NORSK GEOLOGISKTIDSSKRIFT l (1980) Sub-till clays in Numedal 47 Tab1e 3. loiajor chemical compositi on (weight per cent) for tbe c1ay fraction (<2 um) of the Herlandsdalen sediments. Loe. l Loe. 2 Elements Sub till Sand Till Sub-till Till c1ay bed c1ay 510 49.6 56.2 63.3 53.2 54.9 2 Ti0 l. 07 0.95 0.95 1.42 0.86 2 A1 o 15.7 16.5 15.2 16.7 15.9 2 3 Fe o 10.7 7, 2·6 4.93 6.67 4.54 2 3 FeO 3.10 2.80 2.54 3.12 2.50 MnO 0.12 0.13 0.12 0.12 Mg O 5.15 3.08 2.40 4.13 l. 98 cao 2.52 3.00 3.14 2.68 2.79 Na o l. 59 2.41 2.53 2.04 2.18 2 0 3.75 3.66 3.12 4.34 2.49 K2 P 0 0.19 0.14 0.23 0.18 0.26 2 5 Loss ignition 5.50 3.96 2.67 5.47 12.3 Total 99.0 100.1 101.1 100.0 100.8 buted to formation of vermiculite from biotite clay beds and laminae from Hardangervidda and and plagioclase (Meunier & Velde 1976, 1977) as upper Numedalen gave mol ratios Mg0/Al203= well as to transformation of chlorite and 50-60 per cent, except for one value of 70 per trioctahedral illite during subaerial weathering cent. Thus, although the major chemical com processes. position would seem to indicate a marine origin The mineralogical analyses do not identify the for the elay, a lacustrine depositional environ sub-till clay in Herlandsdalen as undisputable ment cannot be completely ruled out. manne. Lanthanide (Ln) elements Chemical composition The distributions of the Ln elements within the The chemical composition of the< 2�.tm fraction < 2 �.tm fraction, relative to La= 100, are given of the ela y and till is given in Tab1e 3. The data in Table4. are in agreement with chemical data of the clay To facilitate their presentation it is usual to fractions of Numedal sediments and when re divide one Ln distribution, element by element, calculated to mol percentages of basic oxides by another distribution, plotting the resulting plot within the same area as Numedal clays in a ratios in a logarithmic scale against a linear scale (Fe203 + FeO + Mg0)-Al203-(K20 + Na20 + of atomic number (Masuda 1962, Coryell et al. K20) triangle (Roaldset 1972). 1963). The data for the present work were thus Roaldset (1972) found a consistent geochemi normalized to their average compositions and cal variation for mol ratios MgO/ Al203 and plotted together with a true marine clay from the K20/ Al203 between marine and non-marine Skagerrak in Fig. 8. clays. The marine clays usually had higher and The lanthanide distribution pattern may be the non-marine clays lower, mol ratios than used as an environment indicator within certain MgO/Al203 = 60 per cent and K20/Al203 = 25 limits (cf. Balashov et al. 1964, Ronov et al. per cent. U sing these criteria, the Herlandsdalen 1967, Fleischer & Altschuler 1969, Martin et al. sub-till clays (MgO/ Al203 = 64 and 87 per cent, 1976). The pH-dependent oxidation of cerium is K20/ Al203 = 29 and 28 per cent) fall within the well known. At pH 8.2, which corresponds to marine region, while the tills and sand plot in the marine conditions, nearly all cerium exists as 3 non-marine group. Analyses of lacustrine sub-till CeH, while the prevailing ion at. pH 7 is Ce +. 48 E. Roaldset NORSK GEOLOGISK TIDSSKRIFT l (1980) for (Ln) distributions = 100) the Table 4. Relative lanthanide (I.a Her1andsdalen eamplee. Loc.l Loe. 2 silb-Hn Sand silb-tlli Element c1ay bed Til l clay Til1 La 100 100 100 10 0 100 Ce 215 224 321 207 916 Pr 44 29 9.4 16.4 29 Nd 152 86 22 65 81 Sm 50 20 4.2 13.5 31 Eu 15.5 2.2 0.5 1.6 5.3 Gd 98 27 5.4 16.9 40 Tb 10.4 1.8 o. 54 1.7 4.4 Dy 40.5 8.6 4.0 12.5 34 Ho 8.2 1.9 0.75 2.5 5.7 Er 29 9.6 3.2 6.4 19.0 Tm 3.3 0.27 o. 74 Yb 17.7 7.7 l.S 4.4 13.1 Lu 5.5 0.26 0.92 The oxidation of ca+ to Ce4+ explains the cerium of the Ln's in the river/ocean boundary in the enrichment in hydrolysate minerals and sub Gironde estuary, France. For soluble river loads aerial weathering products, and the cerium de they found a gradual decrease in the Ce/La fiency in ocean water (Goldberg 1961, Carpenter ration from 1.66 to 0.35 as the salinity increased & Grant 1969, Piper 1974 a,b). According to from O.l %o to 35.5 %o. Hogdahl (pers. comm. 1967) the North Atlantic The Loe. 2 samples (Fig. 8), the clay and the deep water has a pronounced cerium deficiency. till above, exhibit pronounced positive and nega Martin et al. (1976) investigated the behaviour tive Ce anomalies respectively, and thus attach Loe. l. Gl.acial t�ctonized and redeposited s�diments Loe. 2. Undisturbed sediment �q��n:e • Ill • 3 .. lJ Q. E � 0.5 """ !:>;,:�<�::::::� r / /...... \ .. /·\ • Sub-til! clay :; ...-- ...... · · _. ···-- •-• . ...- "--/ - • • -. • m.arint?" -. . ·-· J .,- - !:-:.·�-..::.- .! ------·--- \. ·-· ; \ ...... /. ·----- . .,... ------. . . '\. . 105 Glaclofluvlal' bed • •-• .....- Skagerak clay ', (532) \ \ •/ ',, • Il ....._ • Marine / ...... _., / ...... __ _.... SmEu Gd Tb Dy Ho Er Tm Yb Lu La C� Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Lanthanide atomic numb�r Fig. 8. Lanthanide comparison diagram relative to the average of the Herlandsdalen samples, together with sample S 32, a true marine clay from Skagerrak (Roaldset & Christie 1975). NORSK GEOLOGISK TIDSSKRIFT l (1980) Sub-till clays in Numedal 49 significance when trying to arrive at an under during the last deglaciation (Preboreal?) about standing of the depositional conditions. 10,000 years ago. The basal til! may represent For the overlying til! the Ce enrichment pro either the Weichsel Il or Ill advance (Lundqvist duces evidence for a high content of subaerial 1974). Extensive studies of distribution and weathering products. genesis of tills in central south Norway signify A Ce depletion occurs rarely in postglacial that the basal tills were most probably deposited Numedalen-sediments deposited in brackish and during the onset of a glaciation (Bergersen & non-marine environments, and has been found Garnes 1977). only in one sample, which was actually from Herlandsdalen (Roaldset 1973b). The clay. - Since evidence exists that the Ee The Herlandsdalen elay, due to the Ce defiency mian shoreline in SW Norway and SW Sweden and its resemblance with Skagerrak elay, may was only about 10-20 metres above present have been deposited in a true marine environ sea-leve! (Mangerud 1970, Feyling-Hanssen ment. The possibility of a marine origin requires 1971, Hillefors 1974), and since clays of pre-Ee further discussion as the locality Iies 90 m above mian age have not been found in Norway, the marine limit of the last glaciation. the clays in Herlandsdalen may be assumed to be younger than Eemian. Their stratigraphical posi tion and overconsolidation appear to leave open the possibility that the ela y was deposited during Discussion and correlation . a Middle Weichselian interstadial prior to the The investigations led to the following conclu great Weichsel advance. sions: Taking into consideration the proposed marine The pH, grain size, mineralogical and major origin, the clay must have been deposited at a chemical analyses all suggest a marine deposi time when the sea leve! was about 100 m above tional environment, though Iacustrine conditions the local postglacial marine limit. The cause of cannot be completely ruled out. such high sea-leve! has been generally attributed The Ce-defiency exhibited in the distribution to glacial isostasy. For the Weichsel glaciation, pattern points to a marine origin of the sub-til! Asseev (1968) considers that the maximum clays. isostatic depression was about 1000 m, and The degree of overconsolidation of the undis Nansen (1928) and Gutenberg (1941) give turbed clay indicates a major glacial advance minimum values of 550-700 m. As no eustatic across the Herlandsdalen area after the clay rise in sea level above present niveau has occur deposited. Hence the clay was at !east deposited red within the last 30,000-35,000 years (Milliman prior to the Weichsel III glacial advance (Lund & Emery 1968), glacio-isostatic depression alone qvist 1974), which culminated 17,900 ± 1300 would explain a marine transgression reaching years B.P. (Pisias 1976, see also CLIMAP pro 250-300 m above present sea leve!. ject members 1976, Lawrence Gates 1976, Porter Recent investigations present evidence of et al. 1977). large postglacial vertical displacements (up to As the sub-til! clay sediments Iie 260 metres 100 m) within the southern Fennoscandian Bor above present-day sea-level, i.e. about 90 metres der zone and the Baltic Shield (Lagerlund 1977 above the postglacial marine limit at this locality, a,b, Lundqvist & Lagerbiick 1976, Lagerbiick a marine depositional milieu cannot be explained 1977, Morner 1977 a,b). Worthy of mention is by isostatic/eustatic conditions comparable with also the observation by Reusch (190 l) of vertical those which have prevailed since the last de displacement across glacial striations at Gryte glaciation. fjellet, near Vøringsfossen, west Norway. Thus, The Jack of organic material, pollen diatoms, referring to these investigations a tectonic uplift and foraminifera unfortunately precludes age of the Herlandsdalen area cannot be excluded. datings by means of biostratigraphical and From W and SW Norway marine clays lying radiocarbon methods. far (at Jæren up to 250 m) above the postglacial shoreline has been described by several authors Age and correlation (Grimnes 1910, Kaldhol 1930, 1931, Feyling Hanssen 1966, 1971, 1974, Garnes 1976). At The til/. - The thin ablation til! on top of the basal Foss-Eigeland, near Sandnes, an almost com til! (Fig. 3, Loe. l) was probably deposited plete W eichselian profile has been recorded 4- Geologisk Tidsskr. 1/80 50 E. Roaldset NORSK GEOLOGISK TIDSSKRIFT l (1980) (Bergersen & Pollestad 1971, Feyling-Hanssen offer my sincere thanks. The financial support of Norges 1974). Here, below a 3-5 m thick basal till, a clay Almenvitenskapelige Forskningsråd grant D. 40.31-11 is grate fuUy acknowledged. zone occurs with its base 65 m above present day sea leve!. The clay represents the upper parts of a Middle Weichselian fining upwards sediment sequence corresponding to a marine References transgression before the last large glacial Andersen, A.-L.L. 1971: Foraminifera from the Older Yoldia advance. This transgression has also been rec Clay at Hirtshals, 159-184. In Feyling-Hanssen, R. W., ognized in the Egersund district (Garnes 1976). Jorgensen, J.A., Knudsen, K.L. & Andersen, A.-L.L., Late The Herlandsdalen clay most probably corre Quaternary Foraminifera from Vendsyssel, Denmark and Sandnes, Norway. Bull. Geo/. Soc. Den. 21. lates with the clay unit B) at Foss-Eigeland Aseev, A.A. 1968: Dynamik und geomorphologische Wirkung which according to Feyling-Hanssen (1971, 1974) der europaischen Eisschilde. Petermann' s Geo gr. Mitt ei/un was deposited during the Sandnes Interstadial gen, IJ2, 113-II5. (50,000-20,000 years B.P.). This Middle Weich Bahnson, H., Petersen, K. Strand, Konradi, P. B. & Knudsen, K.L. 1974: Lithology and biostratigraphy of selian interstadial is correlatedwith the Hirtshals Quaternary deposits of the Skærumhede Il boring. Dan. Older Yoldia Clay (Andersen 1971), the Port Geo/. Unders. Årb. 1973, 27-f>2. landia arctica zone of the Skærumhede I (Jessen Balashov, Yu.A., Ronov, A.B., Migdisov, A.A. & Turans et al. 1910), and the zone I of the Skærumhede Il kaya, N.V. l %4: The effect of climate and facies environ ment in the fractionation of the rare earths during sedimen sequence (Bahnson et al. 1973), the Swedish tation. Geochem. lnt. JO, 951-969. analogues the Gotaelv and Y ounger Dosebacka Bergersen, O.F. & Pollestad, B.A. 1971: Evidence of fossil Ellesbo interstadials (Brotzen 1961, Hillefors ice wedges in early Weichselian deposits at Foss-Eikjeland, 1969, 1971), and the Cape Broughton Interstadial Jæren, south west Norway. Nor. Geogr. Tidsskr. 25, 39-45. Bergersen, O.F. & Garnes, K. 1971: Evidence of sub-till (Mid-Wisconsian) known from Arctic Canada sediments from a Weichselian interstadial in the (Feyling-Hanssen 1976a,b). Gudbrandsdalen valley, central east Norway. Nor. Geogr. Tidsskr. 25, 99-108. Bjerrum, L. & Rosenqvist, I.Th. 1956: Some experiments with artificially cemented clays. Geotechnique 6, 1-13. Conclusions Brotzen, F. 1961: An lnterstadial (radiocarbon dated) and the sub-stages of the last glaciation in Sweden. Geo/. Foren. The lanthanide abundance pattern may point to a Forh. Sth. 83, 144-150. Brown, G. (ed.) 1961: The X-ray ldentification and Crystal marine origin for the sub-til! clay sediments in Structures of Ciay Minerals. Mineralogical Society, Herlandsdalen. Their degree of overconsolida London. tion and the fact that they Iie about 90 m above Brogger, W.C. & Schetelig, J. 1923: Geologisk oversiktskart the postglacial marine limit support a correlation over Kristianiafeltet. Nor. Geo/. Unders. with the Sandnes Interstadial. Thus in the terms Carpenter, J.H. & Grant, V.E. 1969: Concentration and state of cerium in coastal waters. J. Mariner Res. 25, 228-238. of Mangerud et al. (1974), the elay was deposited Christie, O.H.J. 1977: Ana/ytical Procedure for the Determi· during a Middle W eichselian Interstadial. The nation of Lanthanoids in Six African Amphibolites. Progress interstadial conditions were followed by the Report series, Massespektrometrisk laboratorium, Uni great Weichsel Il (?)/Ill advance(s) (Lundqvist versitetet i Oslo. CLIMAP project Members, 1976: The surface of the lee-Age 1974). Glaciers from the NW overrode the clay Earth. Science 191, 1131-1138. (Loe. 2), eroding it and transporting part of it as Coryell, C.D., Chase, J.W. and Winchester, J.W. 1963: A thrust slices and also incorporating some clay in procedure for geochemical interpretation of terrestrial rare the til! (Loe. l) which was subsequently depo earth abundance pattern. J. Geophys. Res. 68, 559-566. De Mumbrum, L.E. 1963: X-ray diffraction changes by K-loss sited. from orthoklase and microcline feldspars. Soil Sei. 96, The author wishes to keep open the question 428-430. whether the high Middle Weichselian sea leve! in Feyling-Hanssen, R.W. 1966: Geologiske observasjoner i Herlandsdalen was due to glacio-isostatic Sandnes-området. Nor. Geo/. Unders. 242, 26-43. Feyling-Hanssen, R.W. 1971: Weichselian Interstadial depression, or to neotectonic movements, or Foraminifera from the Sandnes-Jæren area, 72-116. 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