RADIOCARBON DATED RAISED BEACHES IN ... - Lublin

Otto Salvigsen, Anne Elgersma Norwegian Polar Research Institute, Oslo

Wyprawy Geograficzne na Spitsbergen UMCS. Lublin 1991

Jon Y. Landvik

Agricultural University of Norway, Js

ЕЗ

RADIOCARBON DATED RAISED BEACHES IN NORTHWESTERN WEDEL JARLSBERG LAND, SPITSBERGEN, SVALBARD

INTRODUCTION

Raised beaches are characteristic features along the coasts of northwestern Wedel Jarlsberg Land (Pękala, Reder 1989), but so far radiocorbon dates from them are few (Salvigsen 1977, Troitsky et al. 1979, Dallman et al. 1990). TL dates from Holocene levels have also appeared recently (Pękala, Repelewska-Pękalowa 1990, Reder 1990.) In the summer of 1987 we studied the coastal area south of Bellsund, between Calypsobyen and Torellbreen. One of our main objectives was to determine the Late Weichselian marine limit (LWML) and outline the shoreline displacement by radiocarbon dating of driftwood, whale bones an mollusc shells from the raised beaches. We will here briefly present the results from the area between Calypsobyen and Dunderdalen (Fig. 1). The altitudes were determined either by precise levelling (L) or by Pauline barometric altimetres (B) from the mean tide level.

DESCRIPTION OF DATED SAMPLES AND SITES Sa87-85. Dyrstaddaien. Section in a marine terrace on the northern river bank showing till underlying beach material with shell fragments. The terrace reaches 58 m (L) above sea level which is the marine limit in the area, but shell fragments for dating were collected just above the till in the section at 50.5 m above sea level. One fragment (105 mg) was sent for dating and the age 12.350 +155 years (Ua-1081) was reported from the laboratory. The apparent age of 440 years (Mangerud, Gulliksen 1975) was then subtracted to get the real age, 11.910 ± 145 years. This date indicates that the marine limit in Dyrstaddaien is about 12.000 years old. Sa87-ioi. Lognedaien. Shell fragments were found in the bed of a small stream on the northern side of the main river in Lognedaien about 48 m (B) above sea level. The fragments which were of My a truncal a and/or Hiatella arctica seemed to have been washed out from a finegrained sediment (silt/clay). One fragment (79 mg)

9

was sent for dating, and the reported result was 11.795 ± 160 years (Ua-1082) which means a real age of 11.355 ±160 years. The marine limit in Lognedaien was determined as 55 m above sea level (L), and the date gives the minimum age for the marine limit. Sa87-63. Tjomdaien. Small piece of bone (about 0.5 kg), most probably of whale, which was found on a beach ridge west of and near the river in Tjorndalen, 51.3 m above sea level. It was lying among, and was partly covered by well rounded pebbles and cobbles, and the piece of bone itself was also abraded and rounded. It had a dense structure and the quality seemed to be very good for dating. The result was 9470 +130 years BP (T-7669) which is probably about 1500 years too low. The reason could be either contamination by Younger Carbon, or that the bone has been moved by men or animals upwards from where it originally was deposited. This date does not seem reliable, and is therefore left out in further discussion. Sa87-84. Lognedaien. Sample from large whale vertebra found halfway buried in beach material on the south side of the river in Lognedaien, 25.3 m above sea level. The quality of the sample was good even though the bone structure was rather porous. It revealed the age 9180 + 130 years BP (T-7671). Sa87-97. Lognedaien. Sample from driftwood log, diameter 20 cm, found in swampy area 10.8 m above sea level, about 1 km north of the main river in Lognedaien. It was stuck in sandy permafrost below 0.3 m of peat material. The wood quality was very good, but the upper part of the log was shattered, probably by frost Table 1. RADIOCARBON DATES FROM BEACHES IN NORTHWESTERN WEDEL JARLSBERG LAND Corrections for deviations from a 1 3 C= -25%0 PDB have been applied. 440 years have been subtracted from the original ages of shells arid bones, which is the standardized mean reservoir age used by the Radiocarbon Laboratorly in Trondheim for Norwegian (including Svalbard) samples. Sample Lab.No. Acre a13C %0 PDB M a.s. 1. Material Location 85 Ua-1081 11,910+145 * 50.5 Shells Dyrstaddaien * Ua-1082 11,355+160 101 48 Shells Lognedaien 63 T-7669 9470+130 -14.6 51.3 Bone Tjerndalen 84 T-7671 9180+130 -15.6 25.3 Bone Lognedaien 97 T-7672 8760+120 + 10.8 Wood Lognedaien 68 T-7670 5970+100 -14.4 6.7 Bone Lognedaien + 99 T-7679 1100+80 6.0 Wood Dyrstaddaien 3 * a' not measured. Standard value of 0.0%q used for correction. + a 1 3 not measured. Standard value of -26.1 % 0 used for correction. 10

processes. It was determined as the species Larix sibirica, and the age is 8760 ±120 years BP (T-7672). Sa87-68. Lognedaien. Sample from large whale cranium incorporated in beach sediments on top of the lower beach ridge terrace A 6.7 m above sea level. The bone quality was very good and it was dated to 5970 ±100 years BP or BC4980-4750 (T-7670). All ВС ages have been calculated according to Stuiver and Reimer 1986. sa87-99. Dyrstaddaien. Sample from 10 m long driftwood log with root. Largest diameter was 35 cm, and it was determined to be of the species Larix occidentalis. It was found 6.0 m above sea level which is lower than terrace A and clearly higher than the level of the modern driftwood. The dating revealed the age 1100 ±80 years PB or BC880-1010 (T-7679). It should, however, be noted here that the log was found on a high energy beach where flotsam and jetsam reach higher levels than usual along the coast.

THE E M E R G E N C E CURVE

The radiocarbon dates have been plotted in a time/elevation diagram, Fig. 2, and constitute the basis for the drawn emergence curve. The dates are few, but they are supported by dates from the north side of Bellsund (Landvik et al. 1987) and also by dates from areas further south along the coast, so far not published. Most of the dates are from Lognedaien, and the curve demonstrates roughly the emergence of this valley. The marine limit south of the river in Lognedaien was determined to 55.0 m above sea level. The uppermost beach ridge is distinct, and is followed immediately above by an unwashed till cover. The upper outstanding beach ridge terrace in Lognedaien has an altitude of about 37 m above sea level and is correlated to level В north of Bellsund (Landvik et al. 1987). It has been marked on the curve as a small notch. The curve continues very steeply down to present sea level about 8000 years BP, but the exact minimum level is not known here. Thereafter a transgression took place and resulted in the distinct beach ridge terrace which can be correlated to level A north of Bellsund (Landvik et al. 1987). Precise levelling of top levels on two different sites in Lognedaien gave the results 6.7 m and 6.8 m above sea level, respectively. The date of a whale cranium from the top level showed the age of about 6000 years (T-7670) which is in accordance with the results from the northern side of Bellsund (Landvik et al. 1987). The sea regression after 6000 BP is impossible to follow in detail. The altitudes are very small compared to the possible variation in deposition level of driftwood and whale bones. The log of about 1100 years (T-7679) primarily demonstrates that driftwood sometimes can be thrown high above its contemporaneous sea level. The Calypsobyen dates of Salvigsen (1976) are also shown in Fig. 2. Their 11

positions indicate .that they only show maximum ages for the levels where they were found.

LATE WEICHSELIAN MARINE LIMITS AND DISTINCT MORPHOLOGICAL LEVELS

Marine terraces which have been covered by glacier ice occur in most of the valleys in the studied area. In Dyrstaddaien they have a thin till cover and were found up to 85.5 m (L) above sea level which is the highest marine level observed with certainty in this area. These levels are of pre-Late Weichselian age and out of range for the radiocarbon method. The altitude/distance diagram (Fig. 3) shows Late Weichselian marine limits and two distinct levels corresponding to levels A and В on Nordenskioldkysten north of Bellsund (Landvik et al. 1987). The LWML in Lognedaien was determined to 55 (L) m, in Dyrstaddaien 58 (L) m, and in Tjorndalen 59 (L) m. In addition a few Pauline measurements of observed marine limits are also plotted in the diagram. In Beisdalen the marine limit was measured to 55 m (B), and Blomlidalen and the Scottbreen area showed values about 60 m (B). These values demonstrate clearly that the LWML is increasing slightly from the west towards the east. The age of the LWML is about 12,000 years. The beach level В has been described north of Bellsund (Landvik et al. 1987), and it also occurs south of Bellsund. In Dyrstaddaien the top level of this distinct beach ridge was 39.2 m and in Tjorndalen 41.6 m. In Beisdalen and Lognedaien distinct top levels were measured at 37 m (B), and about 40 m (B) was observed near Scottbreen. This level is also rising slightly from the west towards the east, and its age is roughly 10,000 years. Also beach level A (Landvik et al. 1987) is very distinct on the south side of Bellsund. It has only been levelled in Lognedaien where it is 6.7 to 6.8 m above present sea level and about 6000 years old. East of Lognedaien most of the coast has so high bedrock cliffs that beach level A is missing.

ACKNOWLEDGEMENT

Radiocarbon dates were performed by The Radiological Dating Laboratory in Trondheim under the supervision of Reidar Nydal and Steinar Gulliksen and by The Svedberg Laboratory in Uppsala under the supervision of Goran Possnert. Leif M. Paulssen identified the wood species.

12

REFERENCES Dallmann W. К., Hjelle A., Ohta Y., Salvigsen O., Bjornerud M.G., Hauser E.C., Maher H.D., Craddock C., 1990: Van Keulenfjorden. Geological map 1:100,000. Norsk Polarinstitutt Temakart nr. 15., MangerudJ., Gulliksen S., 1975: Apparent radiocarbon age of recent marine shells from Norway, Spitsbergen and Arctic Canada. Quaternary Research 5, 263-273. Landvik J. Y., Mangerud J., Salvigsen O. 1987: The Late Weichselian and Holocene shoreline displacement of the west-central coast of Svalbard. Polar Research 5 n.s., 29-44. Pękala К., Reder J., 1989: Relief and Quaternary deposits of the Dyrstaddalen and Lognedalen (West Spitsbergen). (In Polish). Wyprawy Geograficzne na Spitsbergen, 159-169 Lublin. Pękala К., Repelewska-Pękalowa J., 1990: Relief and stratigraphy of Quaternary deposits in the region of Recherche Fiord and southern Bellsund (Western Spitsbergen). Wyprawy Geograficzne na Spitsbergen, 9-20. Lublin. Reder J., 1990: TL age of Quaternary sediments of the Dyrstad Valley (Bellsund, Spitsbergen). Wyprawy Geograficzne na Spitsbergen, 21-26. Lublin. Salvigsen O., 1976: Radiocarbon datings and the extension of the Weichselian ice-sheet in Svalbard. Norsk Polarinst. Arbok 1976, 209-224. Stuiver M., Reimer P. J., 1986: A computer program for radiocarbon age calibration. Radiocarbon 28, 1022-1030. Troitsky L., Punning J. M., Hiitt G., Rajamae R., 1979: Pleistocene glaciation chronology of Spitsbergen. Boreas 8, 401-407. STRESZCZENIE W artykule przedstawiono wyniki datowań metodą radiowęgla osadów z obszaru równin nadmorskich NW części Ziemi Wedela Jarlsberga (Spitsbergen). Na podstawie wielu utworów oraz kryteriów wysokościowych podniesionych teras morskich stwierdzono nierównomierną wielkość i różpe tempo ruchów izostatycznych terenu w okresie schyłkowym plejstocenu i w holocenie.

13

5 km

Renardodden

Be 'sda/en

Grytdalen

Fig. 1. Location map, northwestern Wedel Jarlsberg Land. The numbers show roughly the location of dated samples. Table 1.

14

Ma.s.l.

14

1000

С years

Fig. 2. Shoreline displacement curve for northwestern Wedel Jarlsberg Land (Lognedaien).

15

m

a.s.l.

6040200-

i

1—r