Thermal contraction cracks are well known proxies of frost action, both in recent and relict environments. A sedimentological analysis was carried out on relict sand wedges from two study sites (Kemeneshát and Mogyoród area) in Hungary, in order to investigate past periglacial processes in the Pannonian Basin. After adequate sample preparation, the grain size distribution of sand wedge infillings (N = 82) was determined, and descriptive statistical analysis was carried out using GRADISTAT software. 470 quartz sand grains were examined by using a scanning electron microscope. Thereby, the roundness of the grains was determined and grain surface microtextures were analysed.The results show that every sample from the Kemeneshát area exhibit poor sorting values and mainly polymodal distributions, while the Mogyoród samples are exclusively unimodal and moderately sorted. SEM investigation reinforces the abovementioned statements with the Krumbein's scale results. Most of the studied grains are angular, which refers to the short transportation time of the sediment. Crystal overgrowth was often found on the grains, which suggests sandstone or metamorphic origin for the infilling material. Intensively weathered grain surfaces mark lots of changes in the palaeotemperature. Fresh, sharp edges, as well as big, unaltered conchoidal fractures and breakage blocks indicate intensive frost weathering processes during the last damaging cycle of the sediment.

The Pannonian Basin was located in the southernmost, disputed limit of permafrost during the Last Glacial Maximum (LGM). In the western part of the basin, over an area of 1,200 km2, more than 150 sites with polygonal patterned ground were surveyed, and 72 sediment samples from forms identified as relict sand wedges were collected. Ten optically stimulated luminescence ages were obtained from the infills, while morphometric analyses were also carried out on satellite images. Our study revealed that the polygonal networks developed in several phases, from 15.01 ± 1.68 to 23.0 ± 1.7 ka. The polygons have an average diameter of 13–23 m and are mainly present on flat surfaces, intruding into the gravelly, alluvial host of the paleo‐Rába. Statistical analyses highlighted the short transportation period of the sandy infill and multiple sediment provenances. This study adds further data to assess the presence of permafrost or deep seasonal frost and to the interpretation of the LGM in the central European periglacial domain.

<p>Thermal contraction cracks are well-known proxies of frost action, both in recent and relict environments. A sedimentological analysis was carried out on relict sand wedges from two study sites (Kemeneshát and Mogyoród area) in Hungary, in order to investigate past periglacial processes in the Pannonian Basin. After adequate sample preparation, the grain size distribution of sand wedge infillings (N=82) was determined, and descriptive statistical analysis was carried out using GRADISTAT software. 470 quartz sand grains were examined using a scanning electron microscope (SEM). Thereby, the roundness of the grains was determined and grain surface microtextures were analysed. The results show that every sample from the Kemeneshát area exhibits poor sorting values and mainly polymodal distributions, while the Mogyoród samples are exclusively unimodal and moderately sorted. SEM investigation reinforces the abovementioned statements with Krumbein’s scale results. Most of the studied grains are angular, which refers to the short transportation time of the sediment. Crystal overgrowth was often found on the grains, which suggests sandstone or metamorphic origin for the infilling material. Intensively weathered grain surfaces mark lots of changes in the paleotemperature. Fresh, sharp edges, as well as big, unaltered conchoidal fractures and breakage blocks, indicate intensive frost weathering processes during the last damaging cycle of the sediment. These results help us to reduce the arising uncertainties in the paleoenvironmental reconstruction of the Pannonian Basin during Late Pleistocene.</p>

<p>The granulometric (particle size and shape) data of sediments provide insights into the processes of grain formation, transport, deposition, and post-depositional alteration mechanisms. Therefore, granulometric proxies are widely used in paleogeographical research.</p><p>A statistically robust, objective, and representative description of the particle size and shape characteristic of a sample can only be achieved with a large number (n>10<sup>4-5</sup>) of observed mineral grains. Automated image analysis techniques meet the above requirements. Not only the size distributions of the scanned particle populations are determined, but also the distributions of different shape (e.g., circularity, convexity, solidity) and other shape-dependent size parameters (e.g., circular equivalent diameter, length, width, circumference, area) of each grain.</p><p>The presented granulometric analyses were based on sediments from the Carpathian Basin (Central Europe): filling material from Pleistocene periglacial sand wedges (Kemeneshát, Mogyoród gravel pit –Danubian Plain), recent wind-blown sand (Nyírség, Danube-Tisza Midland Ridge), fluvial sand from floodplain and transport media (Lower-Tisza Plain and Dráva Plain). The grains were analysed primarily for their circularity, solidity, and convexity properties. Our aim was to identify fingerprints related to the environment and the transport processes (e.g., type, time).</p><p>According to our granulometric results, the Kemeneshát and the Mogyoród site sand wedges can be distinguished. Most samples from Kemeneshát contained fresh, less rounded grains while the other source contained mature, rounded grains. Although, it was also possible to differentiate between the Kemeneshát samples based on the grain shape parameters. Granulometric differences can be detected between the fluvial and eolian sand samples, especially in the case of roundness parameters. Using granulometric proxies, it can be concluded that the filling material of the wedges in the Mogyoród gravel pit is mainly eolian. Therefore, the origin of Kemeneshát samples cannot be clearly identified due to the less mature nature of the grains. Examination of more samples is required to reveal granulometric fingerprints that characterise certain sedimentary environments.</p><p>The application of granulometric proxies on relict and recent sand materials can be used to reconstruct the paleoenvironmental conditions. The method can be a new tool for investigating the origin of different sediments and can extend the interpretation of granulometric data.<br>Support of the National Research, Development and Innovation Office (Hungary) under contract NKFIH FK138692 is gratefully acknowledged.</p>