Types of coasts of South Bellsund (West Spitsbergen) and
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Types of coasts of South Bellsund (West Spitsbergen) and
Marian Harasimiuk, Waldemar Institute of Earth Sciences Maria Curie-Sklodowska University Lublin, Poland Jezierski Wyprawy Geograficzne na Spitsbergen UMCS. Lublin 1991 TYPES OF COASTS OF SOUTH BELLSUND (WEST SPITSBERGEN) AND TENDENCY OF THEIR EVOLUTION During geographical expeditions Bellsund 1986 —1988 which were organized by the Institute of Earth Sciences University of Maria Curie-Skłodowska, Lublin the studies were carried out on the dynamics of the coasts of south Bellsund and Fiord Recherche. The studies covered the coast section 52 km long. The types of coasts with a close relation to the geological structure were mapped. Some observations concering dynamics of coast processes were made. Based on the observation of a drifting ice movement the directions of currents in the coastal sea zone about 1 km wide were recorded. GEOLOGY AND GEOMORPHOLOGY Bellsund is a wide bay in the southern part of Spitsbergen, opened to the West. Two big fiords discharge to this'bay: Van Mijen and. Van Keulen, and the also wide, short Fiord Recherche. The investigated section of the seashore is the northern part of Wedel Jarlsberg Land. As for tectonics Wedel Jarlsberg Land may be divided into three structural elements: a western block, a ten kilometer wide ^one of folded deformations and central depression (Foreland) in the East (Orvin 1940, Birkenmajer 1958). The whole investigated area is situated in the western block. It is characterized by the prevalence of Proterozoic and Older Paleozoic rocks which were took part in fold and block movements including volcanic activity many times. As a result a very differentiated complex of rocks of various range of metamorphisation was formed (called Hecla Hoek formation after Orvin 1940). This area is built of rocks that can be included among the youngest links of Hecla Hoek formations (called as Kapp Lyell Formation). It consists of tillites, phyllites and sandstones. Craddock et al. (1985) consider these sediments to be glacial, fluvioglacial and limnoglacial with various degrees of metamorphisation. Nowadays, they form a flat, wide syncline with the North — South direction of an axis. The western block is not of a homogeneous character. It is divided with faults of a NNW to SSE and SW to NE directions. In the north of Bellsund there is a long, narrow through called Forlandsundet which also belongs to the western block. Fiord Recherche is a southern part of this 17 structure. It was filled with Paleocene deposits (mainly sandstones and shales poorly cemented, inclined in the NE direction at an angle of 5° to 25°). The center of the northern part of Wedel Jarlsberg Land is a glaciated mountain area about 600 m to 830 m high (Fig. 1.). Small glaciers go down in a N and NE directions across wide short valleys, however the usually do not reach a sea shore. Their recent marginal zones are from 2 to 4 km from the coast. Only the Renard Glacier (the biggest one) reaches a sea shore, forming in some places an active ice cliff. On western and southern forelands of the mountain massif there are coastal plains which are uplifted abrasive platforms with many rock remnants, and locally with a cover of sandy gravels marine deposits (Szczęsny et al. 1990). The width of these plains is from 3 km on western Lognedalsflya and North-East (Calypsostranda) sides to 500 m (Dyrstadflya and Lyellstranda). Within the shore plain one can distinguish the system of three terraces, 5 m to 8 m, 17 m to 25 m and 30 m to 35 m high. One the slopes of mountain ridges dipping on the coast zone there are 3 other terraces (45 m, 55 m and 80 m) of the shape of narrow rock shelves. The biggest areas are occupied by the terrace 17 m to 25 m. Generally, there are not glacial deposits on the surface of these terraces. Only in the area of Calypsostranda terrace till deposits were found and also the Young Pleistocene sea clays. The northern marginal of Wedel Jarlsberg Land like most coasts of Spitsbergen are characterized by young (recent) lifting movements with a clearly differentiated spatial tempo (Marcinkiewicz 1961, Stablein 1978, Stankowski 1982). TYPES OF COASTS The main factors which form coasts are the activity of waves, sea currents and tidal (Hayes et al. 1980). The character and intensity of processes occurring in the coast zone are modified by the local factors: lithology, tectonics, exposition to sea currents. As a result sections of. coasts differentiated morphologically developed (Harasimiuk, Jezierski 1988). There were distinguished the following types of coasts: 1. Group of abrasion coasts (la. active cliff in Proterozoic rocks, lb. active cliff in Paleocene rocks, lc. active cliff in Quaternary deposits, Id. ice cliff). 2. Group of accumulation coasts (2a. beaches with a fully developed profile, 2b. sand bar, 2c. tidal flat or delta). 3. The plain coasts with a leveled accumulation — abrassion shape with undeveloped beaches (3a. shaped on metamorphic rocks and 3b. shaped on Quaternary deposits). Active cliff in Proterozoic rocks. Irregular cliffs cut in a series of tillites and sandstones with different resistance and also with a complicated system of faults and joints. These are many arched incisions with a character of small bays of different radii (from 100 m to 1 km). On the prolongation of the capes between 18 arches there are numerous stacks. The maximal height of the cliff cut in Proterozoic rocks is 25 m. In the bays narrow undeveloped beaches were formed — dependent on the dynamics of processes they are built of sand, gravels or boulders. The coasts of such a character occupy about 30% of the investigated coast line. Active cliff in Paleocene rocks. This type of coast occurs only in Skilvika Bay and it makes about 2% of the coast line (Fig. 1) Nonresistant rocks (mainly poorly cemented sandstones and mudstones) cause quick retreating of the cliff in SE direction. Abrasion processes are excellently legible here. A narrow gravel beach of incomplete profile formed at the foot of the cliff. Thermodenudation processes are also very important in developing the cliff of this type. Active cliff in Quaternary deposits. Quaternary deposits occur in the eastern zone of the coast. They are the covers of slope deposits, fluvioglacial gravels and sands, glacial and marine deposits. In the eastern part of the investigated area (Recherche Fiord) there are cliffs cut in slope and moraines deposits with differentiated heights — from 1 m to 5 m. In the northern part there are cliffs cut in beach gravels building the older marine terrace. On the cliffs cut in moraines and marine clays landslides and solifluction processes play a significant role in modelling cliffs. There also quickly retreating cliffs. Ice cliff. As the result of progressing deglaciation of the area the zone of the contact of glacier ice and sea is still being reduced. Nowadays, the majority of the ice cliffs consists of a part of Recherche Glacier. This cliff is about 15-20 m a high. Flat sea shores are formed in the places where ice cliff regresses. Full developed beaches. The are formed in the strong shore currents zone with additional balance of sediments transport. They appear in the places were intensive processes of accumulation take place, as the result of currents convergention with a great transport of sandy gravel materials along the seashore. The beach there is about 350 m wide. Parallel sandy gravel bars. Bars appear only in Recherche Fiord. The develop in the proximal side of fluvioglacial fans or by small alluvial fans (deltas) that are formed at the mouths of the streams. Tidal accumulation flats or delta. The tidal accumulation flat was formed in a big structurally conditioned bay of Recherche Fiord at the mouth Chamberlin River, where currents parallel to the coast do not appear, and where tides amplitude is about 1.5 m. The flat watt surfaces reaches about 1 km 2 . This zone is dissected by a composite system of transit channels of fluvio-glacial waters. The surface of the tidal flat is made of silts in the lower part and silty sands in the upper part. There are not storm ridges on this tidal flat because the whole bay is screened from the storm winds. The plain coasts with leveled accumulation — abrasion shape with undeveloped beaches. These kinds of coasts make up about 30% of the investigated shore line. In the western part (Lognedalsflya) there is a wide mesotidal abrasive plain (tidal 19 range is about 2 m) with small storm accumulation ridges (Fig. 1). This type of coast was formed on gently sloped metamorphic rocks. In the eastern part (Recherche Fiord) this type of coast was formed in Quaternary deposits (mainly glacial tills and solifluction covers), (Pękala, Repelewska-Pękalowa 1988). CONCLUSIONS The results of the investigations carried out in different areas of Wedel Jarlsberg Land enable comparisons of processes and forms in the segments of coast characterized by environmental parameters. The eastern part (particularly the coast of Recherche Fiord) represents the coasts of low wave energy conditions with prevailing accretion processes. The northern and western parts of the coast are zones of high wave energy conditions, with prevailing abrasion processes. The most important waves to operate in these parts of the coast are generated by strong winds from the West (large oceanic waves). Detailed investigations will be carried out during next expeditions. REFERENCES Birkenmajer K., 1958: Z badań nad stratygrafią i tektoniką formacji Hecla Hoek w Ziemi Wedel-Jarlsberg (sprawozdanie wstępne) Prz. Geofiz. R. 3 (11) z. 2 Craddock C., Hauser E.,Maher M. D., Sun A.Y., Zhu-Guo-Qiang, 1985: Tectonic evolution of the West Spitsbergen fold belt. Tectophysics, 114. Harasimiuk M., Jezierski W., 1988: Typy wybrzeży południowego Bellsundu. Wyprawy Geograficzne na Spitsbergen. UMCS Lublin, Hayes M., Owens E. H., Hubbard D. K., Abele R. W., 1980: The investigation of form and processes in the coastal zone. Coastal Geomorphology. Marcinkiewicz A., 1961: Podniesione terasy morskie południowego wybrzeża Bellsundu i fiordu Van Keulena między lodowcami Recherche i Hessa (Zachodni Spitsbergen) Biul. Geol. t. 1 cz. 1. Orvin A. K., 1940: Outline of the geological history of Spitsbergen. Shrifter om Svalbard og ishavet nr 78. Stablein G., 1970: Untersuchung der Auftauschicht iiber Dauerfrost in Spitsbergen. Eiszeitalter u. Gegenwart, 21, Obringen. Siankowski W., 1982: The role of marine processes in the morphogenesis of the Lisbetdalen (NW Sórkapp Land, Spitsbergen) Questiones Geographicae 8. Szczęsny R., Nitychoruk J., Dzierżek J., Harasimiuk M., Pękala К., Repelewska-Pękalowa J., 1989: Photogeological map of the Renardbreen, Scottbreen and Blomlibreen forefield (Wedel Jarlsberg Land, Spitsbergen) 1:10 000. Wydawnictwa Geologiczne. 20 STRESZCZENIE Podczas geograficznych ekspedycji „Bellsund 1986 — 1988" organizowanych przez Instytut Nauk o Ziemi Uniwersytetu Marii Curie Skłodowskiej z Lublina prowadzone były badania nad typami wybrzeży i dynamiką procesów w strefie brzegowej w północnej części Ziemi Wedel Jarlsberga. Głównym czynnikiem modelującym badany odcinek wybrzeża o długości 52 km jest działalność fal, przy współudziale prądów morskich i pływów. Procesy soliflukcyjne i termoabrazja odgrywają znikomą rolę. Charakter i natężenie procesów zachodzących w strefie wybrzeża modyfikują czynniki lokalne: litologia skał, tektonika, ekspozycja w stosunku do przeważającego kierunku ruchu fal. W konsekwencji powstały wyraźnie zróżnicowane pod względem morfologicznym odcinki wybrzeża. Wyróżniono następujące typy wybrzeża: 1. wybrzeża abrazyjne (la. aktywne klify w skałach proterozoicznych, lb. aktywne klify w skałach paleoceńskich, lc. aktywne klify w osadach czwartorzędowych, ld. klify lodowe). 2. Wybrzeża akumulacyjne (2a. plaże o pełnym profilu, 2b. wybrzeża mierzejowe, 2c. równiny pływowe — delty). 3. Abrazyjne równiny nadmorskie z plażami o niepełnym profilu. We wschodniej części badanego obszaru (fiord Recherche) przeważają wybrzeża kształtowane przez fale o małej energii, z dominacją procesów akrecji. Północna i zachodnia część badanego wybrzeża kształtowana jest przez fale oceaniczne o wysokiej energii za zdecydowaną przewagą procesów abrazji. 21 COAST TYPES OF SOUTH BELLSUND ы to ABRASION FORMS JVWM •л* SVALBARO Archipelago mm 2 Ц 5 6 Ш- 7 ACCUMULATION FORMS Q 9 JOSEPHBUKTA 10 FLAT, ABRASIVE ANO ACCUMULATIVE COAST "П •«••• 12 / TTOMTOOOEN FAGERBUKTA DIRECTION OF SEA CURRENT < = = 13 - — 14 — 15 KVITFISKPYNTEN DUNDERBUKTA Fig. 1. Types of coasts of south Bellsund. Abrasion forms: 1 — active cliff in Proterozoic rocks, 2 — active cliff in Tertiary rocks, 3 — cliff in sea gravels, 4 — cliff in moraine, 5 — ice cliff, 6 — old cliff, 7 — abrasive remnants. Accumulation forms: 8 — beaches of the developed profile, 9 — tidal flat or delta accumulation, 10 — old shore ridges. Flat, abrasive and accumulative coast: 11 — on the Proterozoic rocks, 12 — on the Quaternary deposits. Direction of sea current: 13 — oceanic drift (high ware energy), 14 — foehn wind drift (low wave energy), 15 — local near shore drift. 16 — points of abrasion measurements.