NEW PALEOGEOGRAPHY DATA OF THE EASTERN COAST OF GREEN FJORD (WEST SPITSBERGEN ISLAND) BASED ON RESEARCH OF THE HOLOCENE DEPOSITS ON FINNESET CAPE WITH USE OF ISOTOPE-GEOCHEMICAL METHODS

Abstract

The relevance of the research consists in determining the age of mollusks in the Green fjord bay of West Spitsbergen Island and physical and chemical parameters of their habitant environment in conditions of the threat of destruction of geological outcrops as a result of actively developing processes of coastal thermo-abrasion and man-made load of «Arcticugol» combine. The main aim of the research is to reconstruct physical and chemical parameters of mollusks habitant environment in Holocene based on determination of mollusks species and research of isotope-geochemical composition of shells and their host rocks. Methods. Mollusk species were identified using morphological method and decomposition of shell samples – by acid dissection. Content of microelements and microelements was determined on Aurora Elite inductively coupled plasma mass spectrometer (Bruker, Germany) and on LabCenter XRF-1800 wavelength X-ray fluorescence spectrometer and stable isotope ratios – on Finningan MAT253 mass spectrometer. Age of mollusk shells was identified on liquid low-background scintillation counter. Objects of the research are quaternary sediments of the coastal cliff of Finniset cape (Green fjord bay, West Spitsbergen Island), shells of bivalve mollusks and their fragments. Results. The authors have identified the detected macrofauna complexes represented by bivalve mollusks (Hiatella arctica, Mytilus edulis, Tridonta borealis, Mya truncata) and the age of fossil shells of marine mollusks for Finniset cape, which are from 7970 to 8050 years old. It was established that the mollusks found in lower layers lived in a wormer climate than those found in the overlying layers. The authors reconstructed redox conditions using Ni/Co ratios ranging from 1,5 to 9 units and V/Cr less than 2 units. Content of the U was detected in range from 0,2 mg to 4 mg. An analysis of the Cu/Cr ratio in the outcrop shows that the distance from the area of denudation to the sedimentation area changed insignificantly. Zn concentration in sediments indicates the temporal regression of the sea and predominance of continental sedimentary regime over sea regime. Determination of Mn content in mollusk shells shown, that they lived in coastal-marine zone with high oxygen content.

Keywords

• holocene
• bivalve mollusks
• spitsbergen
• green fjord bay
• climatic variations
• paleogeographical reconstruction
• stable isotopes
• geochemical indicators