Glacial landforms in the upper Forbach drainage basin (northern Black Forest, south-western Germany)

Felix Martin Hofmann, Christopher Hazlett, Mathias Vinnepand, Lukas Gegg

University of Freiburg

Last update: 2 September 2026

Abstract

The aim of the data collection was to reconstruct the chronology and spatial extent of Late Pleistocene glaciation in the south-eastern part of the northern Black Forest, south-west Germany. The mapping was conducted as part of the project 'Chronology of the last glaciation of low mountainous areas in Central Europe' project (funded by the German Research Foundation (DFG), granted to Felix Martin Hofmann (see https://gepris.dfg.de/gepris/projekt/534739108?language=en, last access: 13 June 2025).

As a first step towards a comprehensive glacier reconstruction detailed glacial geomorphological mapping was undertaken following current standards in glacial geomorphology, allowing for the simultaneous selection of suitable targets for dating campaigns. A dedicated mapping campaign was conducted to critically assess and refine previous interpretations of the glacial record in the study region, with the objective of achieving the highest possible accuracy and consistency in the reconstruction.

Dataset description

The acquired data are geodata, digitised from field maps. These geodata represent cirques, moraines, moraine crests, and terraces in the study region:

·        Cirques (ForbachValley_cirques_ETRS89UTM32N.shp)

·        Moraines (ForbachValley_moraines_ETRS89UTM32N.shp)

·        Moraine crests (ForbachValley_moraine_crests_ETRS89UTM32N.shp)

·        Terraces (ForbachValley_terraces_ETRS89UTM32N.shp)

These are provided as ESRI shapefiles which can be easily opened and inspected with common geographical information system (GIS) software, such as QGIS (QGIS Development Team, 2024). Cirques, initial cirques, and moraine crests are represented as polylines, whilst the moraines and terraces are polygons. Note that the coordinate reference system of all geodata is as follows: EPSG 25832: ETRS89 / UTM Zone 32N (https://epsg.io/25832, last access: 6 February 2025).

Data collection began in April 2026 CE, starting with the identification of potential glacial landforms with the aid of derivatives of a high-resolution digital elevation model. Several field campaigns were undertaken to verify the results in the field. Data collection ended in July 2026 CE.

Spatial extent

The minimum and maximum easting and northing (in m; ETRS 1989 UTM Zone 32N) are as follows:

easting_min: 449029

easting_max: 456094

northing_min: 5366334

northing_max: 5371941

Data collection

The mapping of glacial landforms followed the common holistic approach in glacial geomorphology (e.g., Di Costanzo & Hofmann, 2016; Chandler & Lukas, 2017; Hofmann et al., 2020), involving both the interpretation of derivatives of a high-resolution digital elevation model of the study region, the DGM025 (xy-resolution of 0.25 m; vertical accuracy of 0.15 m; LGL, 2021) of LGL, the Baden-Württemberg State Agency for Geoinformation and Land Development, and extensive field surveys. Since red relief image maps (RRIMs) proved to be useful for the mapping of the glacial record in the southern Black Forest (Hofmann & Preusser, 2025) and elsewhere (Köse et al., 2021, 2022; Altınay et al., 2022), a RRIM was established for the whole study region with the QGIS software (QGIS Development Team, 2024). Establishing the RRIM required generating raster files, representing the positive and negative openness (Yokoyama et al., 2002). Note that openness is a measure for the degree of dominance or enclosure of a location on an irregular terrain surface (Yokoyama et al., 2002). These raster files were derived with the relief visualization toolbox (RVT; Kokalj & Somrak, 2019) for QGIS, available at https://rvt-py.readthedocs.io/en/latest/rvtfor_qgis.html (last access: 27 February 2024).

The subsequent calculation of differential openness (Chiba et al., 2008) was based on the following equation:

(positive openness – negative openness)/2

Raster files representing the topographic slope and differential openness were finally blended with the 'multiply' option in QGIS. Candidates for glacial landforms were detected in QGIS.

Potential glacial landforms were then directly targeted during extensive field surveys and marked on print-out versions of the RRIM with superimposed contour lines (1:5000 scale). If available, exposures on ice-marginal landforms were inspected. The geomorphological field maps were finally digitised.

References

QGIS Geographic Information System (Version 3.40.1-Bratislava) (2024). QGIS Development Team, https://www.qgis.org

Open GeoData Portal - DGM025. Landesamt für Geoinformation und Landentwicklung (LGL), (last access: 13 June 2025), https://opengeodata.lgl-bw.de/#/(sidenav:product/4)

Altınay, O.; Sarıkaya, M. A.; Çiner, A.; Žebre, M.; Stepišnik, U.; Yıldırım, C.; Yetemen, Ö.; Wilcken, K. M. (2022): Cosmogenic ³⁶Cl surface exposure dating of glacial landforms on Mt. Barla (SW Turkey). Geomorphology, 416, 108424, https://doi.org/10.1016/j.geomorph.2022.108424

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Di Costanzo, H.; Hofmann, F. (2022): Retreat of the Drac Blanc glacier (Massif of the Ecrins, French Alps). Méditerranée, https://doi.org/10.4000/mediterranee.7796

Hofmann, F. M.; Preusser, F. (2025): Revisiting ice-marginal positions north-east of Feldberg, southern Black Forest, south-west Germany. E&G Quaternary Science Journal, 74, 1-35, https://doi.org/10.5194/egqsj-74-1-2025

Hofmann, F. M.; Rauscher, F.; McCreary, W.; Bischoff, J.-P.; Preusser, F. (2020): Revisiting Late Pleistocene glacier dynamics north-west of the Feldberg, southern Black Forest, Germany. E&G Quaternary Science Journal, 69, 61-87, https://doi.org/10.5194/egqsj-69-61-2020

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