Weichselian Convolution Phenomena and processes in fine sediments.

In three excavations in the southern Netherlands and northern Belgium, the Weichselian convolutions in fine sand, silt and clay deposits were investigated, and an attempt was made towards a semi-quantitative approach to some sediment parameters. This, together with a detailed field survey, enabled interpretation of the deformations as forms of periglacial loadcasting. They originated from the time of permafrost degradation when large quantites of water were available. The amplitude of the involutions can be related to the depth of the permafrost table at that time. During the weichselian, two periods occurred in which this involution process could have been active     

COSMOGENIC 10BE-AGES FROM THE STORE KOLDEWEY ISLAND, NE GREENLAND

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.     

THIN-SECTION SIZE ANALYSIS: A FURTHER NOTE

Criticisms by VAN DER PLAS (1962) of thin-section point counting as a method of size analysis appear to be based on confusion between number percent and volume percent. Points are samples of volume, and point counts yield volume percents. This is as much true of size classes as of other types of constituents, though distortions are caused in the distribution by the sectioning effect. The “ribbon” method advocated by Van der Plas counts individuals rather than points and hence yields number percents. The two types of statistic are fundamentally different.