Strontium and oxygen isotopic composition of East Greenland rivers and surface waters: implication for palaeoenvironmental interpretation

Abstract

Isotopic composition of strontium and oxygen and strontium concentrations from 4 hydrographic sites in Scoresby Sund Fjord and 6 rivers draining the adjacent Jameson Land have been investigated. Schuchert Flod, the major river on Jameson Land, erodes a large celestite (SrSO 4) deposit. Dissolved Sr in Schuchert Flod has 87Sr/ 86Sr = 0.7137 and is responsible for most of the continental Sr flux to the fjord. The Sr isotope data have been used to construct a mixing model for the surface water in Scoresby Sund Fjord. Salinity ( S) and Sr concentrations ( C Sr) of brackish water from the fjord show conservative mixing between river water and seawater. Results of the 87Sr/ 86Sr–salinity mixing model of seawater and fresh water were used to interpret the isotopic composition of Sr ( 87Sr/ 86Sr) and oxygen (δ 18O c) of recent and interglacial (Eemian ≈120 ka) shallow-water bivalve shells from the coast of Jameson Land. Because of the high C Sr in some of the rivers draining Jameson Land, a correlation exists between 87Sr/ 86Sr and δ 18O c of recent and interglacial shallow water bivalve shells from the coast of Jameson Land. Higher-than-seawater 87Sr/ 86Sr values in shells from the Langelandselv interglaciation can be explained only if the shells were formed close to a Sr-rich fresh water source which is not present in the Langelandselv area today. These results suggest that there was a different river and drainage system on the Jameson Land peninsula during the Last Interglacial. The 87Sr/ 86Sr values indicate that shell formation took place in waters with salinities between 20 and 31‰ in a fjord with less glacial melt-water than seen today.