Eemian fossil caves and other karst structures in Cretaceous chalk and succeeding Quaternary sediments covering the salt structure Krempe-Lägerdorf (SW Schleswig-Holstein, North Germany)
Grube, Alf; Grube, Friedrich; Rickert, Björn-H.; Strahl, Jaqueline
published: Jun 1, 2017
published online: Jul 31, 2017
ArtNo. ESP171016802004, Price: 29.00 €
Enhanced activity of karstification recorded in the overburden of salt structures Krempe-Lägerdorf and Quickborn in recent years led to actual research during geological surveying. Fossil cave formations in the Heidestrasse chalk quarry in Lägerdorf with a volume of up to 30,000 m3 have been documented in the Cretaceous chalk. The cave infill of an actual documented fossil hollow was composed of organic gravelly sands, tills, clays, silts, strongly weathered organic muds and crystalline erratics with more than 0.5 m in diameter. This intense karstification within the chalk probably took place during the Eemian Interglacial. Eemian karst cavities in the overburden were found several times in the Münsterdorf Geest, anyhow most forms seem to be of Holocene age. Strong karstification can occur in areas with extensive cohesive cover with till and clay, if small-scale access areas of groundwater to the chalk and a corresponding mechanical pre-stressing of the chalk (tectonics, glaciotectonics etc.) are present. In Heidestrasse, a karstification occurs to a depth of 60 m below ground in the form of fluviokarst. In the Saturn chalk quarry a relationship between a cohesive cover on the chalk made of extensive Saalian till and Holocene organic muds and a reduced karstification could be documented. The latter confirms a significant karstification of the chalk surface during the Holocene. Forecasting of a vulnerability to formation of sinkholes is difficult due to a complicated composition of the overburden and groundwater movements. In addition, the sensibility to karstification of the chalk can locally be increased by (neo-)tectonic, glacigenic, glaciotectonic and periglacial processes. Glaciotectonics as a potential factor in areas of stronger karstification of the western Münsterdorf Geest should be considered to a greater extend in future studies.