Stefan Strasky

Surface exposure ages imply multiple low-amplitude Pleistocene variations in East Antarctic Ice Sheet, Ricker Hills, Victoria Land

Abstract One of the major issues in (palaeo-) climatology is the response of Antarctic ice sheets to global climate changes. Antarctic ice volume has varied in the past but the extent and timing of these fluctuations are not well known. In this study, we address the question of amplitude and timing of past Antarctic ice level changes by surface exposure dating using in situ produced cosmogenic nuclides (10Be and 21Ne). The study area lies in the Ricker Hills, a nunatak at the boundary of the East Antarctic Ice Sheet in southern Victoria Land. By determining exposure ages of erratic boulders from glacial drifts we directly date East Antarctic Ice Sheet variations. Erosion-corrected neon and beryllium exposure ages indicate that a major ice advance reaching elevations of about 500 m above present ice levels occurred between 1.125 and 1.375 million years before present. Subsequent ice fluctuations were of lesser extent but timing is difficult as all erratic boulders from related deposits show complex exposure histories. Sample-specific erosion rates were on the order of 20–45 cm Ma-1 for a quartzite and 10–65 cm Ma-1 for a sandstone boulder and imply that the modern cold, arid climate has persisted since at least the early Pleistocene.

Cosmogenic 10Be-ages from the Store Koldewey Island NE Greenland

Abstract. Earlier work in northeast Greenland has suggested a limited advance of the Greenland Ice Sheet during the Last Glacial Maximum (LGM). However, this concept has recently been challenged by marine geological studies, indicating grounded ice on the continental shelf at this time. New 10Be‐ages from the Store Koldewey island, northeast Greenland, suggest that unscoured mountain plateaus at the outer coast were covered at least partly by cold‐based ice during the LGM. It is, however, still inconclusive whether this ice was dynamically connected to the Greenland Ice Sheet or not. Regardless of the LGM ice sheet extent, the 10Be results from Store Koldewey add to a growing body of evidence suggesting considerable antiquity of crystalline unscoured terrain near present and Pleistocene ice sheet margins.

Harmonising the lithostratigraphic nomenclature: towards a uniform geological dataset of Switzerland

Uniform geological datasets are a prerequisite for geological GIS analyses. Although the Geological Atlas of Switzerland 1:25,000 aims to supply spatial geological information nationwide, little effort has been undertaken in the past to harmonise this map series and its vector datasets. In the course of the HARMOS project, lithostratigraphic nomenclature was harmonised and standard map legends for a target scale of 1:25,000 were produced. This allows representing the lithostratigraphic units of Switzerland in a homogeneous way and sets a new reference in the lithostratigraphy of Switzerland. More than 40 experts in the field of regional stratigraphy contributed their knowledge to the project and, together with the Swiss Committee on Stratigraphy, guaranteed a high quality level. All results are presented in the Lithostratigraphic Lexicon of Switzerland, available cost-free online at http://www.strati.ch. By improving quality and accessibility of lithostratigraphic information, we supply a fundamental basis for the Swiss geological community and further research.

Where Do the Boundaries Lie

While revising and harmonizing the stratigraphic framework for Swiss geological maps, a number of issues arose, including where to set boundaries when subdividing the vertical successions of strata, how to deal with lateral facies changes and thickness variations, and the extent to which complications such as metamorphic overprints can be overcome. The case of Lower Jurassic deposits from the main tectonic domains of Switzerland and neighbouring regions illustrates the necessity of a rigorous lithostratigraphic approach, despite formal constraints and practical limitations.

Harmonising the Swiss Lithostratigraphic Nomenclature

After more than 80 years of traditional geological map production for the 1:25,000-scale Geological Atlas of Switzerland, 143 printed sheets with equivalent legends of this map series exist. During the last few decades, the Swiss Geological Survey has spent considerable effort on converting the existing map sheets into Geographic Information System (GIS) datasets. By means of an initiative of the Swiss Geological Survey, other federal departments and several cantons, the published Atlas maps were completed with compiled geological GIS maps of lower quality, in order to make GIS maps available for the whole of Switzerland. However, each of the 220 available GIS maps has its individual lithostratigraphic legend. In this work, we present the HARMOS project, which aims to harmonise the multiple existing map legends and to elaborate a lithostratigraphic standard legend, including harmonised descriptions, for Swiss geological maps at a scale of 1:25,000. The project involves 40 recognized experts in stratigraphy. A close collaboration with and quality control by the Swiss Committee on Stratigraphy assures the required quality for broad acceptance. Preliminary results indicate that the application of the elaborated lithostratigraphic map legend to GIS datasets remarkably increases the value of the geological data. This confirms the idea that the new lithostratigraphic standard legend will provide a fundamental base for a future seamless, semantically harmonised, nationwide geological GIS map of Switzerland.