TheNorthern Harz Boundary Fault[1][2] (German:Harznordrandstörung orHarznordrandverwerfung) is ageological fault where theHarz Block, which consists of rocks formed during thePalaeozoic Era and folded in the course ofHercynian mountain building, borders on theSubhercynian Basin orHarz Foreland. The fault is also known in English as the Harz North Rim Fault[3] or Harznordrand Thrust (Fault).[4]
The northern edge of the Harz is oriented in aHercynian (WNW-ESE) direction and runs from Neuekrug-Hahausen viaLangelsheim,Goslar,Bad Harzburg,Ilsenburg,Wernigerode,Blankenburg,Thale andGernrode to the area ofBallenstedt.
The Northern Harz Boundary Fault forms the southern border of the Northeast German Basin, a part of the Central European Basin. The Subhercynian Basin, also known as the Harz Foreland, is a small sub-basin of the Northeast German Basin. This intracontinental basin that has been subsided since thePermian period was formed from the Hercynian foreland basins and accumulated sediments of the Mesozoic era. The basin was formed by a deformation or bulging of theMoho. In the Cretaceous the basin was squeezed byAlpine orogeny which also uplifted the Harz Block.
The Northern Harz Boundary Fault was activated in theEarly Cretaceous and the Harz was uplifted along the line of thefault. The Harz Block was thrust over the Mesozoic strata of the Subhercynian Basin, steeply tilting itsMesozoic strata. The most intensive phase of uplift occurred in a period of about 2 million years from the middle of theSantonian age to the lowerCampanian. The completion of uplift is shown by the fact that the rocks of theUpper Cretaceous lie at a much shallower angle than those of the Lower Cretaceous, and that, in some places, they overlapdiscordantly. The uplift is still going on today.
Along the western part of the fault, the Harz was lifted by at least 5 to 7 km, which can be estimated from the thickness of theMesozoic rocks deposited in the Harz Foreland anderoded Paleozoic rocks. The Harz was partly thrust over the layers of Mesozoic rock to the north. Here, the Mesozoic strata were tilted steeply (70-80 degrees) or even overturned. A good example is at the Langenberg Quarry, but there are also many other outcrops that show the steeply sloping strata. In these strata, rocks of theJurassic are steeply inclined. Near Blankenburg and Ballenstedt there are rocks lying at steep angles from theCretaceous, which form the so-called Devil's Wall orTeufelsmauer. They include,inter alia, rocks of Heidelberg Sandstone, asilicified quartz sandstone.
Springs rise along the entire fault system, both those with low quantities of minerals as well asmineral water springs. The mineral waters are used, for example, in Bad Harzburg, by the spa industry.