Frost weathering in contemporary active-layer deposits—micro-scale records from Kaffiøyra Plain (NW Spitsbergen)

Abstract

Frost weathering serves a critical role under cold, nonglacial (i.e., periglacial) conditions. Within a contemporaneous active layer, the progressive development of microscale frost-weathering features may be recorded on the surface of sand-fraction quartz grains (0.5–0.8 mm). The purpose of this study is to identify the factors responsible for the effects of this type of frost weathering. Sediments from four profiles were tested from the Kaffiøyra Plain (NW Spitsbergen) in 2011. These profiles represent sediments of various origins and ages, ranging from 11 to 9 ka B.P., and on to the Little Ice Age. Scanning electron microscopy, grain-size distribution, CaCO₃ content, pH, and deposit geochemistry were used to determine the intensity of frost weathering on study sediments. The results from sand-sized quartz-grain microtexture analysis indicates that a low degree of micro-scale frost weathering had occurred regardless of sediment age. Most of the micro-scale frost-weathering effects were recorded in the active layer's top and base. Quartz-sand-grain microtextures predominate in these two locations, their extant providing insight into the initial development of such weathering. Microtexture's predominance signifies an inception of weathering development, manifested as large and small conchoidal fractures (>10 μm and <10 μm, respectively). Small and large breakage blocks (>10 μm and <10 μm, respectively) are recorded as accessory microtextures, requiring more freeze–thaw cycles and longer operating times. Of note, frost-weathering effects are dependent on grain-size composition; the finer the sediment, the more intense is the grain-weathering development.