Research Note Some notes on glacial geomorphology in the inner part of St. Jonsfjorden, Svalbard ARNT-IVAR KVERNDAL Kverndal. A . 4 . 1991: Some notes on glacial geomorphology in the inner part of St. Jonsfjorden. Svalhard. Polar Research 9(2). 215-217. Working as a field assistant for Dr. Harmon Maher during the Norwegian Polar Research Institute's Svalbard Expedition 1991, A:I. Kverndal had the opportunity to do a large-scale study on thc glacial geology in the St. Jonsfjorden area. This note emphasises thc glacial geomorphology connected to the Konowbreen/Osbornebreen glacier system: i t also comments on thc possibilities for further research in this area. Arnl-Ivar Kverndal, University of T r o m m . Departtnenl of Geology. Tromsm Mu.reum. N-9000 Trojnsm. Norway. St. Jonsfjorden (78"30'N, 12"30'E) is situated on the western coast of Spitsbergen, Svalbard (Fig. 1 ) . The area is characterised by jagged peaks, nunataks, and the many glaciers draining down to thc fjord. The bedrock geology is dominated by a complex composition of metamorphic rocks, the oldest of which comprise the Hecla Hoek hasement rocks that were deformed and met- amorphised during the Caledonian and older events. Overlying the Hecla Koek we find the Upper Paleozoic and Mesozoic rocks, deformed and metamorphised during the Early Tertiary opening of the Norwegian-Greenland and Arctic oceanic basins (Maher 1989). The glaciers in the St. Jonsfjorden area are of the typical Spitsbergen typc: topographically influenced ice-masses drain- ing down to the fjord from composite accumulation areas. Supraglacial meltwater drainage, the observation of icings, and the significance of icc-cored moraincs in the frontal areas indicate a subpolar tcmperature regime of the St. Jonsfjordcn glaciers. A recorded surge on Osbornehreen and the estimation that YO%, of the glaciers on Svalhard are of the surging typc (Hagen & Liestdl 1990) suggest that most of the glaciers around St. Jonsfjordcn are influenced by this special periodic hehav- iour. the phenomenon makes it difficult to establish a relation- ship between climatic and glacier front variations in the region. Glacial geology According to Liestd (1988). the advance of the glacier fronts o n western Spitsbcrgen in the second half of the last century represents the maximum extension of ice cover in the Holocene. Maps, aerial photographs, and mass-balance investigations in the Kongsfjorden area show that the glaciers' icc-mass volume change has been negative since the beginning of this century (Hagen & Liest01 1990; Lefauconnier & Hagen 1990). This continuous deficit in mass-balance can be explained by higher summer temperatures (Hagen & Liestol IY90), or by the low precipitation rate (Liest01 1988). In the inner part of St. Jonsfjorden, the two glaciers Konow- breen and Osbornebrecn compose the most dominant glacier system in the area (Fig. 1). Distally to today's glacier fronts, lateral moraines along both sides of the fjord give an indication of the system's extensions during the Holocene. Even though the moraines have a very complex morphology, it is possible t o interprete different glacial stages. The marginal and oldest moraine, possibly deposited in the second half of the last ccntury, gives a picture of the system's maximum Holocenc extension (Fig. 1). The moraines indicate a low-gradient ice profile, extending to the Piriepynten and Konowfjcllet area. where push-moraines containing marine scdiments and shcll fragments were discovered (Fig. 2). The ridges are locatcd 2- 7 m a.s.1.. and both the situation and morphology connect them to thc Konowbreen/Osbornebreen glacier system. The marine sediments and the content of shells indicate that the glacier front was grounded during this advance. Glacial erraties arc found in the same area as thc push- moraines (Fig. 1). In fact, at Konowfjellet erratics are found on top of the ridges. They are conglomerates of Carbonifcrous age and limestones of Permian age. belonging respectively to the Tornkanten and Kapp Starostin formations. The latter formation is only to be found in the Osbornebreen drainage area. documenting the origin of the morainic material. Between 1987 and 1089 Osbornehreen surged, and the glacier front advanced about 2 km (Fig. 1). A 40 to 5 0 m lowering of the ice-profile in the accumulation area shows how ice-mass surplus has been transported from this area down t o the frontal part of the glacier. Today the front displays a typical post-surge situation: a heavily crevassed frontal area. steep lateral sides. and a high calving rate. The present glacier flow is not sufficient Some notes on glacial geomorphology of St. Jonsfjorden, Sualbard 217 Fig. 2. Push-moraine at Piriepynten. Dr. Maher as scale. Fig. 3. Vertical section at the front of Osbornebrecn docu- menting that the glacier has been sliding over the old ice-cored moraine, leaving it almost undisturbed. Further research The complex geology and geomorphology. the different typcs o f glaciers draining down to t h e fjord. and the fact that 01- borncbreen surged between 1987 and 1989 all make the St. Jonsfjordcn area very interesting for further and more detailed research. However. thcrc have been few investigations in the St. Jonsfjorden arca, probably because of its inaccessibility. Only one paper published by Forman (1989) is known to the author. One of thc most challenging topics in glacial geological rerearch today is achicving better understanding of thc geo- morphological proccsscs associated with glacier front oscil- lations. In St. Jonsfjordcn the glaciers are easily accessible by boat. making i t possible to investigatc many different types of glaciers. Thc Osborncbrcen surge also makes it possible to carry out detailed studics on the formation of marginal moraines in front of a surging glacier. Bccausc of thc complex geology in the St. Jonsfjorden area, a detailed petrographical mapping of morainic material and glacial erratics can provide valuable information about glacier limits. A 1 : 100000 scale bedrock map is in preparation at the Norwegian Polar Research Institute. References Forman. S. L. 1989: Late Weichselian glaciation and dcglacia- tion of Forlandsundct area. western Spitsbcrgcn. Boreus 18, 51-6U. Hagen, J. 0. & Liestd, 0. 1990: Long-term glacier mass- balance investigations i n Svalbard 1950--1988. A n n . Glaciol. 14, 148-152. Lefauconnier, B. & Hagen. J . 0. 1990: Glaciers and Climate in Svalbard, statistical analysis of the BrBgger glacier mass balance for the last 77 years. Ann. Glaciol. 14, 102-106. Liestol, 0. 1988: The Glaciers in the Kongsfjorden arca, Sval- hard. N o r . Geogr. T i d s k r . 4 2 , 231-238. Maher, H . D . , Jr. 1989: Photointerpretation of Tertiary struc- tures in platform cover strata of interior Oscar I I Land, Spitsbergen. Poiur Kesearch 6, 155-172