The lithospheric transect South Shetland Islands (SSI) — Antarctic Peninsula (AP) includes: the Shetland Trench (subductional) and the adjacent portion of the SE Pacific oceanic crust; the South Shetland Microplate (younger magmatic arc superimposed on continental crust); the Bransfield Rift and Platform (younger back-arc basin); the Trinity Horst (older magmatic arc superimposed on continental crust); the Gustav Rift (Late Cenozoic) and James Ross Platform (older back-arc basin). Deep seismic sounding allowed to trace the Moho discontinuity at about 30 km under South Shetlands and at 38—42 km in the northern part of Antarctic Peninsula (Trinity Horst), under typical continental crust. Modified crust was recognized under Bransfield Strait. Geological interpretation based on deep seismic refraction and multichannel reflection soundings, and surface geological data, is presented.

Three Polish Antarctic Geodynamical Expeditions in 1979/80, 1984/85 and 1987/88 undertook seismic investigations in West Antarctica. Seismic measurements, including multichannel seismic reflection and deep seismic soundings, were carried out in the region of the west coast of the Antarctic Peninsula, between Antarctic Sound and Adelaide Island, Bransfield Strait, South Shetland Islands and South Shetland Trench along several lines with a total length of about 5000 km. Selected crustal sections and one and two-dimensional models of the crust for this area are discussed in detail. The thickness of the crust ranges from 30-33 km in the South Shetland Islands to 38—45 km near the coast of the Antarctic Peninsula. The crustal structure beneath the through of Bransfield Strait is highly anomalous; a seismic discontinuity with velocities of 7.0—7.2 km/s was found at a depth of 10 to 15 km, and a second discontinuity with velocities of about 7.6 km/s was found at a depth of 20—25 km. A seismic inhomogeneity along the Deception-Penguin-Bridgeman volcanic line has also been found. A scheme for the geotectonic division and a geodynamical model of the area are discussed. On the base of all experimental seismic data, it will be possible to construct a continuous geotraverse from Elephant Island, across Bransfield Strait, up to Adelaide Island with a total length of about 1100 km. Crustal section and seismic models along the northern segment of the geotraverse from the King George Island to the Palmer Archipelago are discussed in detail here.

Seismic refraction studies on Central Spitsbergen have shown that there is the fault systems with north-south strike directions, which divide the crust into western, central and eastern blocks. Thickness of the crust in this area varies from 35 to 40 km. Interpretation and modelling of seismic refraction data indicate that the Moho boundary beneath the Central Spitsbergen Basin is a complicated transition zone between crust and upper mantle with the thickness of about 5 km.

The results of the detailed seismoacoustic profilling (CSP, boomar) are presented. The investigation has been carried out in February 1985 and 1988 during two Geodynamical Expeditions organized by the Institute of Geophysics of the Polish Academy of Sciences. The boomar penetration of the caldera floor went down to 150 msec. Four seismoacoustic units of volcanic formations have been determined. The unit A corresponds to pre-caldera series and occurred only in the border part of the flooded caldera. The unit contains mainly pyroclastic rocks (consolidated agglomerates and tuffs) and probably some intercalations of lavas. The units B, C and D fill up the caldera bottom and correspond to post-caldera series. The units are composed of pyroclastic rocks, containing also materials redeposited by lahars, glaciers, landwaters and by wind. The units C and D (the youngest one) were certainly deposited under water. All the units are cut by numerous faults, vents and other types of intrusions. The larger faults, en echelon type, are situated around the bottom and form a ring-fracture. Caldera was formed by succesive stages of collapsing. This process is not finished yet and volcanic activity is still alive (especially in the western part of the flooded caldera).

In the Admiralty Bay 36 taxa of macroalgae were found. Among them the most common were: green alga Monostroma hariotti, red algae — Georgiella confluens, Iridaea cordata, Leptosarca simplex and Plocamium cartilagineum, and brown algae — Adenocystis utricularis, Ascoseira mirabilis, Desmarestia anceps, D. ligulata, D. menziesii and Himatothallus grandifolius. The bottom surface covered with macroalgae (in the orthogonal projection on the water mirror) amounts to 36,9 km2 i.e. 31% of the total surface of the bay. In the central part of the Admiralty Bay the macroalgae aggregations occupy 35% of the bottom surface and are most abundant in respect to the density, biomass, number of taxa (33) and diversity. There were distinguished 3 zones of vertical distribution of phytobenthos in the Admiralty Bay. I zone includes the macroalgae in epilittoral, littoral and sublittoral to the depth of 10 m. II and III zones are situated in sublittoral within the depths of 10 60 m and 60—90 m, respectively. Each zone is characterized by the occurrence of different aggregation of taxa. The bottom areas belong to I, II and III zone of macroalgae make 28%, 64% and 8% respectively in relation to the total surface of phytobenthos in the bay. Vertical range of the distinguished zones varies in different parts of the Bay in relation to the bottom character. Macroalgae occur down to the depth of 90 —100 m. The composition of the macroalgae flora evidences for its transitory character between the benthic subantarctic flora and that of the areas adjacent to the Antarctic continent.

The frequency of wind occurrence at sectors each 30° as well as mean air temperature at particular wind direction were accounted for the warmest and the coldest year of the investigation period 1978—1987 at Polish Antarctic „Arctowski" Station. The effect of orography on wind direction and air temperature was determined. A great rate of dependence of air temperature and wind direction upon atmospheric circulation type was found. High air temperature at the winds from 300° and 330° directions is related both to the kind of air mass and foehn phenomena.

The results of chemical and biological analyses of lake water samples, taken in the Bunger Hills during January—March 1987 by the participants of the 32-nd Soviet Antarctic Expedition from the new seasonal station „Oasis-2" (66°16'S and 110°45'E) are presented. It was discovered that the sea contributed considerably to the formation of intraoasis isolated reservoirs. The water of the epishelf lake — Transkripcii Bay — consists of two layers: upper freshwater (0,3—l,0‰) and lower salt water (19‰); the bottom water contains H2S. The phosphate concentration varied from 3—8 mg 1-1 in freshwater lakes to 37 mg 1-1 in Rybij Chvost Bay (Pass Cove), where the high concentration of chlorophyll „a" (up to 10 mg 1-1) was found.

Schistidium urnulaceum (C. Muell.) B. G. Bell, a species hitherto known from the sub-Antarctic island of South Georgia, is reported for the first time from King George Island, South Shetland Islands, in the Antarctic botanical zone. A description of the species together with illustrations, notes on habitat and a distribution map are provided. Taxonomic notes to assist in the identification of S. urnulaceum are also given.

Studies on the thermics, humidity and refreezing rate of two types of periglacial soils of the marine lowlands of the Hornsund area (SW Spitsbergen) were carried out during spring ablation of the snow cover (1.06.—30.06.1987). Structural soil and peat soil (moss community) were chosen. The soils were studied in places almost completely devoid of the snow cover. A considerable differentiation of temperature in vertical profile and of humidity of surface layer in both soils were found. The dynamics of ground water table and the course and depth of spring refreezing of both soils were also different. The differences reflect the different origin of soils and consequently, their different grain-size distribution, physical properties and morphology of both types of soils as well as their water balance.

Oxygen consumption and carbon dioxide production in some Arctic soils were measured in different thermic and humidity conditions. Testing temperatures was following: 4, 8 and 12°C. The rate of metabolic processes was temperature and humidity dependent. In the temperature of 4°C the metabolic processes intensity was negatively correlated with humidity, however in higher temperatures the higher was the humidity the higher was also the intensity of metabolic processes. The interaction of humidity and temperature is probably to great extent responsible for low rate of decomposition processes of organic matter in polar conditions.

This paper contains the results of phytosociological studies carried out on the model fragment of Spitsbergen tundra at Bellsund. In the area of 4800 m2 19 plant communities have been distinguished through association analysis and these communities, in turn, have been compared according to cluster analysis. Also, ecological groups of species have been distinguished.

The annual rate of decomposition in five soil types of tundra situated in the Fugleberget drainage area (Hornsund Fjord, South Spitsbergen) was investigated by use of the method of standard cellulose samples. The rate of decomposition varied from 15% to over 65% a year and was closely connected with a contents of nitrogen in soil, amount of which varied from 0.33% to 3.44%. The results presently obtained are much higher than those obtained by the same method in other polar regions.

Photogeological map of of Treskelen-Hyrnefjellet-Kruseryggen area, Wedel Jarlsberg Land, Spitsbergen.

Scale 1 : 10,000

In Northwestern and Central Spitsbergen geomorphological and botanical data were collected on slope deposits associated with infrequent meteorological events. In hillslope debris flows triggered by heavy rainfall, compact volumes of debris range from 1 to 600 m3 . Recurrence intervals of major episodes are tentatively estimated from lichenometry at 80 to 500 years. Such debris flows are widespread in Spitsbergen and induce conspicuous geomorphological effects. Nevertheless, typical levees and lobes are small-sized because of the thinness of permafrost and they rarely survive more than one century. In contrast, catastrophic slush avalanches mobilize 1300 to 7000 m3 of rock debris every 500 years, forming long boulder tongues and fans. Such accumulations can been observed in much more restricted sites. In Central Spitsbergen at least three generations of slush avalanche deposits have been identified and lichenometry suggests that such boulder tongues survive for at least 2000 years. So the geomorphic impact of sporadic slush avalanches appears much more important than the effects of recurrent spring snow avalanches which do not generate original and long-lasting landforms. Botanical studies show that investigations of saxicolous lichen communities allow more reliable chronological reconstructions than observations of phanerogamic and bryophytic vegetation cover. Rhizocarpon diameters are partly interpreted from growth curves from Baffin Island and North Alaska. The results will be refined when a curve is published for Spitsbergen. Nevertheless, recurrence intervals proposed here seem to be consistent and are fruitfully compared with previous evaluations from Swedish Lappland and Colorado.

Field mapping and analysis of air photos enabled to prepare a photogeological map of Treskelen-Hyrnefjellet-Kruseryggen area in scale of 1:10,000. Slope, glacial and nival landforms and sediments, and ten raised marine beaches were distinguished. Morphogenetic evolution of the area is also presented, with discussion of probable glacier advances and land uplift during the Late Pleistocene and the Holocene.

Studies of Quaternary sediments of South Spitsbergen (Hornsund, Bellsund and northern Billefjorden regions) focus on their occurrence, origin and chronostratigraphy. Methods and results of geological mapping are described. Glacial, glaciofluvial, glaciolacustrine and aeolian sedimentary environments, rock glaciers, taluses and raised marine beaches are presented. Mutual relations of these sediments as well as their radiocarbon and thermoluminescence datings made chronostratigraphy of Late Quaternary glacial episodes possible. Results of preliminary neotectonic studies are also presented, the same as works on periglacial phenomena, chemical weathering and tundra vegetation. Key significance of the studies for the Quaternary evolution of the Arctic and for better recognition of geodynamic phenomena of Pleistocene glaciations in Poland (Tatra and Sudeten Mts included) is underlined.

On the ground of results obtained by the seismoacoustic profiling carried out in 1985 and primary examination of core samples the following main seismoacoustic units are distinguished and characterized: unit A — bedrock, unit B — till and/or compacted glaciomarine deposit, unit C — glaciomarine ice-front deposit, unit D — glaciomarine mud. These results enabled to present the distribution of seismoacoustic units along the fiord and its extension on the shelf, as well as to determine a relation of bottom structures to Late Vistulian(?) deglaciation and the action of Holocene tributary glaciers, probably during the Little Ice Age. The position of marginal structures corresponding to local retreat stages of the glacier front is also presented.

An analysis of seismic shocks from the Heer Land and the Nordaustlandet was made (shocks recorded by the Hornsund seismological station). Kinematic models and synthetic seismograms were constructed. A system of horizontal discontinuities located in the upper mantle was assumed. A good agreement between observational data from the seismograms and theoretical results was obtained.

The paper presents descriptions and illustrations of Anthracoporella spectabilis Pia (Dasycladaceae) and Palaeoaplisina laminaeformis Krotov (Hydrozoa) from the Treskelodden Formation (Lower Permian, Sakmarian) of the Hornsund area (Treskelen, Urnetoppen), and Chaetetes arcticus sp. n. (Demospongiae) from the „Wordiekammen Limestone" (Pernio — Carboniferous) of the Isfjorden area of the southern and central part of Spitsbergen. A. spectabilis and P. laminaeformis common in the Hornsund area are also known from the northern Ural Mts. and Timan.