SEDIMENTARY ANALYSIS OF A LAKE CORE AT BARROW, ALASKA

It deals with the systematic multi-variable analysis of sedimentary process on the grain-size data and geochemical data of a lake core at Barrow, Alaska, Arctic. The core with length of 60 cm is from under sea level of 2 metre in Elson Lagoon, and about 2 km away from the coast. The top of the core (0-40cm) was separated into 40 samples (one per a centimetre), the bottom (40-60cm) 10 samples (one per 2 cm). It was treated by multivariable analyses including cluster analysis, factor analysis, major component analysis that the data from these 50 samples were made a granular analysis of 25 indexes (size degrees: 10mm, 5mm, 3mm, 1mm, 0.8mm, 0.5mm, 0.35mm, 0.25mm, 0.2mm, 0.15mm, 0.125mm, 0.1mm, 0.07mm, 0.05mm, 0.035mm, 0.025mm, 0.02mm, 0.016mm, 0.01mm, 0.008mm, 0.005mm, 0.002mm, 0.001mm, 0.0005mm, and < 0.0005mm) and a geochemical analysis of 45 indexes (P, Ba, Sr, V, Ni, Cu, Co, Cr, Mo, Zn, Ga, Nb, Sc, Sn, Ta, Y, Yb, Be, Ce, Pb, Zr, La, Li, W, Rb, C, HCO₃^-, Cl^-, SO₄^2-, Ca²⁺, Mg²⁺, K⁺&Na⁺, CaCO₃, pH, SiO₂, P₂O₅, Fe₂O₃, Al₂O₃, CaO, MgO, K₂O, Na₂O, MnO, TiO, and crystaled H₂O). R-type cluster tree of the grain-size has two branches, A Branch is greater than 0.1mm, B Branch less than 0.1mm. First Branch of R-type geochemical cluster tree is composed of Nb, Ce, Cr, Rb, HCO₃^-, CaO, P₂O₅, SiO₂, and pH, Second Branch is composed of residual geochemical indexes. Two branches of R-type cluster tree of colligation of the grain-size and geochemical indexes are mix of A Branch and First Branch, mix of B Branch and Second Branch, respectively. It indicate that there is causality between geochemical indexes and grain-size. The crown of Q-type cluster trees show that 32-60 cm section of the core is continental deposits, and this sedimentary environment and process are stable and steady; 20-32cm section is a transition period from continental deposits to marine sediments, and magnetic mineral with Cr decrease sharply the oxides of Si and Ca reduce, one of Ti and Fe increase, organic matter raise;10-20 cm is marine sediments, coase grain is a little, oxide, silt, organic matter and adsorbed composition fluctuate greatly, leached remain composition speed to increase in surface layer, the source of matter is stable, but dynamic environment change greatly. This research was financially supported by funding from National Natural Science Foundation of China (49971078).