The Kalkberg is a high mountain located in the Franconian Alb near Weismain in the Upper Franconian district of Lichtenfels (Bavaria). It stands at an elevation of 454 meters above sea level.
Geographical location and description
The Kalkberg rises approximately 138 meters above Weismain and the Weismain Valley funnel in the Weismain-Alb, which is a northern foothill of the Franconian Alb. It slopes down to the west towards the foothills of Kleinziegenfeld Valley and to the east into the Krassach Valley, which is the foothills of the Bärental Valley. The Kalkberg is about 0.7 km dominant compared to the next higher mountain, the Teisenberg. The prominence between the Kalkberg and the Teisenberg has an elevation difference of 18 m. There is also a secondary peak that has an altitude of 450 meters above sea level. In the past, pits in the area of the two peaks indicate that lime marl was extracted to produce building lime. Additionally, a mobile phone mast is located on the mountain's northeast slope.
Geology
Brown Jurassic
Geologically, the mountain is composed of stratified deposits from the Brown Jurassic (Dogger) β to δ. As its name suggests, the mountain predominantly consists of brown rock and soil colors. The rock formations primarily consist of fine-grained light beige, yellow, or brown sandstone and soil-sandstone mixtures, often limonitic, with clay layers.
The upper three Brown Jurassic layers γ, δ, and ε, form an ornate clay layer about 10 m thick, rising from 395 to 405 m above sea level. This layer is visible as a gently rising terrace-like slope, typically 20 to 100 meters wide, with a distinct upper edge separating it from the iron sandstone and the steeply rising White Jurassic formations. Due to the extensive afforestation of this area, it no longer stands out as prominently as it did in past centuries, when it was consisted primarily of fields and meadows. The ornate clay layer appears gray and contains numerous limestone shards from the overlying rock. Due to limited exposure, the tripartite division of the layer can only be discerned occasionally. The lower gamma layer, about two to three meters thick, consists of calcareous sandstone beds and clay interbedded with sand lenses. The middle delta layer, two to four meters thick, is composed of iron-oolite limestones, which are relatively hard limestone balls with brown rind and bluish core. After frost weathering, they are typically only present as fragments. The remaining Brown Jurassic-ε layer, nearly ten meters thick, emerges as light gray, stiffly plastic, calcareous clay. In its unweather state, below the ground surface, it has a semi-solid to solid consistency and contains fossil-rich layers. All three layers are characterized by the presence of large brown iron ooids, which are visible to the naked eye. The youngest layer of the Brown Jurassic, ζ, either did not deposit in the whole Upper Main area or exists only in very small remnants.
White Jurassic
The upper layers of the Kalkberg, as well as its two peaks, represent White Jurassic reefs. The lowest two White Jurassic levels α and β form a uniform stock of approximately 25 meters in thickness throughout the Weismain area, including the Kalkberg. However, these layers are composed of different types of rock. The Alpha Formation, also known as Lower Marl Limestone, consists mainly of marls. On the other hand, the Beta Formation is composed of fine-grained, smooth-crushed bench limestone. It is rich in fossils such as ammonites, belemnites, thin-shelled bivalves, and calcite crystals that have formed within cavities. It is important to note that the common name “Werkkalk” ("factory limestone") used for this layer is misleading in the upper main area since the bank limestones found there are not frost-resistant and therefore not suitable as a material. At the Kalkberg, the alpha and beta levels are located at an altitude of 405 to 430 m above sea level. At the boundaries of the layer, the iron layer silicate glauconite also occurs. Furthermore, the layer is abundant in calcite crystals.
Above the β stage, which is already becoming more flat but still easily distinguishable, the White Jurassic γ layer begins from 430 m above sea level. This layer is also referred to as Upper Marl Limestone and consists of clayey marl. It exhibits a gentle to moderate slope. Occasionally, larger limestone layers can be found within this formation.