Huippuvuorten Koillismaan Isvika–lahden Holoseenin aikainen sedimentaatio raekoostumuksen avulla kuvattuna

A high-resolution grain size analysis was carried out on a 2,5 meter long marine core series from Isvika Bay, Nordauslandet, Svalbard. Grain size analysis was performed with a Malvern Mastersizer 2000 laser grain size analysator. The analysis of the results was determined by the relative proportions of sand (greater than 63 microns), silt (8-63 microns) and clay (less than 8 microns). Clay, silt and sand proportions were made in to a triangle diagram. On certain depths a model diagram was taken and its curves were examined. The material was determined by the following standard deviations (d₁₀, d₂₅, d₃₀, d₅₀, d₆₀, d₇₅ ja d₉₀), which were calculated to parameters: the coefficient of uniformity (Cu), the coefficient of curvature (Cc), standard deviation (So), skewness (Sk), and kurtosis (K). The modes were obtained directly from the Malvern software results. In addition, graphs of interpenetration rates dd₅₀ and d₉₀ were made. The grain size of the marine sediment core gave a comprehensive picture of the sedimentation of the last 11700 years in Isvika Bay. IRD-material of over 500 microns accumulates almost the entire time series. IRD's minimum sections describe a momentarily colder period in the climate, which lead to the freezing of the sea and the perennial sea ice. These colder periods prevented sea ice and icebergs importing IRD-material to Isvika Bay. These cold 25-80 years lasting periods have been 10300, 8300, 6700, 5700, 2000, 1200, 500, 300 and 200 cal. years BP. The intervals of cold phases have been on an average of 1150 years. Based to grain size distribution 11700 – 9400 cal. years BP, stable sedimentation environment and cold climate prevailed. 9500 cal. years BP there has been strong warming. 9500 – 7500 cal. years BP, there has been a warm climate, which led to an intensive glacier melting. 7500 – 4500 cal. years BP, the climate got colder for several thousands of years. 4500-4000 cal. years BP the climate got warmer for a period of about 500 years. The climate cooled down gradually between 4000 – 500 cal. years BP toward the present time. The last 500 years the climate has been warmer than the previous, but very variable. During this time, the presence of the multi-annual sea ice has declined.