Geological overview map of the Federal Republic of Germany 1:200,000 (GÜK200) - CC 7910 Freiburg - North

Sheet Freiburg-Nord shows the southern Upper Rhine Graben with its two flanks: the Vosges in the west and the Black Forest in the east. The Black Forest, on the eastern flank of the Upper Rhine Graben, is made up of Variscan granite, gneisses and anatexites. The Variscan folding metamorphosed Precambrian sedimentary rocks; in addition, granitic plutonic rock plutons penetrated in the Upper Carboniferous. Permian rhyolites (quartz porphyries), which can be found in several places in the central and northern Black Forest, are interpreted as ignimbrites. To the north and east, the crystalline rocks of the Black Forest dip beneath the Permo-Mesozoic overburden. A small part of the Northern Vosges is cut on the western edge of the map sheet. The mountain range, which is also Variscan in character, is very similar to the Black Forest in terms of structure and rock composition, but larger deposits of Paleozoic sediments have been preserved. In addition to granite, diorite and paragneiss, the map section also includes Cambrian to Silurian slate and debris sediments from the Rotliegend. The Upper Rhine Graben runs through the sheet from south-southwest to north-northeast. The graben structure is filled with Tertiary sediments. However, the Tertiary is only occasionally visible under the Quaternary cover layer of loess and drifting sands, fluvial or glacifluvial deposits, weathering and alluvial loam. The graben edge area is formed by the outer marginal faults, where the main vertical displacement of the graben structure took place, and fault fields with staggered faults of lower fault height. In the so-called foothill zones, the basement and Permo-Mesozoic cover have sunk in tiers towards the interior of the graben and have thus been preserved, protected from erosion. On the western edge of the Upper Rhine Graben, the fault area of ​​Ribeauvillé, south of the Vosges, and the fault area of ​​Zabern, in the northwest corner of the map sheet, are cut. The Emmendingen-Lahr foothills and the Freiburg Bay are recorded on the eastern edge of the Graben. The formation of rifts in the Tertiary was accompanied by increased volcanism, which culminated in the production of olivine-nephelinite melts in the volcanic area of ​​the Kaiserstuhl. The now heavily eroded volcanic ruins of Miocene volcanic rocks and tuffs are encased and partially covered by Pleistocene loess. In addition to the legend, which provides information about the age, genesis and petrography of the units shown, a tectonic overview map clarifies the major geological units in the map section. A geological section provides additional insight into the structure of the underground. The west-east profile crosses the Upper Rhine Graben with the Kaiserstuhl and the Freiburg Bay as well as the crystalline rocks of the Black Forest.