Editing Minden (section)

== Geology, mineral deposits and their use ==
[[File:Erzgrube Porta - Lore Haeverstaedt.jpg|thumb|Historical minecart as memorial to the ore mining in Häverstädt]]
The Wiehen Hills [[escarpment]] extends more than {{convert|100|km}} from west of Osnabrück to the Porta Westfalica gap and is continued in the Weser Hills range. The escarpment forming horizons incline gently flattening to the north; they are of [[jurassic]] age, overlayed by [[cretaceous]] sediments that form the hill of Bölhorst, and [[tertiary]] layers further to the north. The underground basis is of palaeozoic material from [[Devonian]] to [[Permian]]. A new{{when? |date=September 2024}} described [[genus]] of dinosaur, the [[Wiehenvenator]], was found in the Wiehen Hills near Haddenhausen, popularly referred to as the "Monster of Minden".<ref>{{cite web | last1 = Black | first1 = Riley | title = Paleo Profile: The Monster of Minden | url = https://blogs.scientificamerican.com/laelaps/paleo-profile-the-monster-of-minden/ |website=Scientific American | access-date = 7 February 2024}}</ref>

The Porta sandstone ({{lang|de|Portasandstein}}) of the Wiehen Hills has been used as building material for centuries and is seen in many public and private buildings in Minden and the region. Another valuable material is iron ore, that was being mined until the first half of the 20th century. Mining relics remain: e.g. the ''Potts Park'', an amusement park in Dützen, on a former ore mine.{{cn|date=March 2024}}

The Bölhorst hill {{convert|2|km}} north of the Wiehen Hills is formed by horizons of [[Lower Cretaceous]] age and, in geological sense, is the western extension of the eastward [[Bückeberg]] in the Schaumburg district. In both elevations the hard coal containing [[Berriasian]] layers reach near to the surface. By reason of the correspondence of the [[Bückeberg Formation]] to the [[Wealden Group]], the type of coal found here was named {{lang|de|Wealdenkohle}} in German. Mining in the [[Minden Coalfield]] started in the 17th century during the Swedish occupation and ended in the late 19th century.{{sfn|Nordsiek |1979|p=119}} Another coal mine in the eastern quarter of Meißen worked from 1878 to 1958.{{sfn|Nordsiek |1979|p=129–130}}

A source of 10-percentage brine with its origin in the deep [[Zechstein]] series was pumped in the Bölhorst mine and once used for [[balneotherapy]].{{cn|date=March 2024}}

The last [[Terrain|relief]]-forming age was the [[pleistocene]]. During the [[Saalian glaciation]] the whole region was ice-covered, now verified by [[glacial erratic]] rocks from Scandinavia placed for decoration in the town.{{cn|date=March 2024}} The Bastau depression, a late-Saalian Weser bed, became a marshy peat-covered area; the [[peat]] is completely exhausted for its use in firing. In the time of [[Weichselian glaciation]] the glacier did not reach this region. In the [[periglacial]] climate of that time fine material ([[silt]]) was blown and accumulated north of the Wiehen Hills as well as north of the Bastau depression in either small west–east stripes of [[loess]].

In the Weser depression, Weichselian [[gravel]] deposits are found and used in gravel pits.