Stratigraphic studies in the snow and firn of the Greenland ice sheet

Abstract : The Greenland ice sheet is treated as a monomineralic rock formation, primarily metamorphic, but with a sedimentary veneer of snow and firn. The sedimentary part is perennial above the firn line, and the classical methods of stratigraphy and sedimentation can be profitably applied to it. During a 4-yr period 146 pit studies and 288 supplementary Rammsonde profiles were made along 1100 miles of over snow traverse (Fig. I). Temperature, density, ram hardness, and grain size were measured in the strata exposed in each pit. Stratification of snow results from variations in the conditions of deposition and is emphasized by subsequent diagenesis. Summer layers are coarser grained and have generally lower density and hardness values than winter layers; they may also show evidence of surface melt. The onset of fall is usually identified by an abrupt increase in density and hard ness accompanied by a decrease in grain size. This stratigraphic discontinuity is used as the annual reference plane.