Wellheim Formation | |
---|---|
Stratigraphic range: upper Cenomanian to lower Turonian [1] | |
![]() Siliceous earth quarrying of the Wellheim Formation near Neuburg | |
Type | Geological formation |
Unit of | Danubian Cretaceous Group |
Sub-units | basal marine sandstone, Neuburg Kieselerde Member, Homsand facies [2] |
Underlies | Upper Freshwater Molasse Formation or Pleistocene loams |
Overlies | Schutzfels Formation or Upper Jurassic limestone |
Area | southern Franconian Jura, Upper Bavaria [1] |
Thickness | up to 130 metres (430 ft) |
Lithology | |
Primary | spiculitic silt, fine and medium sands, fine-grained silica (Kieselerde) [1] |
Other | silicified conglomerate |
Location | |
Country | Germany |
Extent | 200 km2 (77 sq mi) |
Type section | |
Named for | Wellheim |
Named by | B. Niebuhr, T. Pürner, and M. Wilmsen |
Location | open pit mines near Wellheim, Germany |
Year defined | 2009 |
Country | Germany |
The Wellheim Formation is a geological formation in southern Germany deposited during the Cenomanian to earliest Turonian stages of the Upper Cretaceous.
The Formation is subdivided into three member units: unnamed basal marine sandstone, the Neuburg Kieselerde Member, and an upper silicified conglomerate (Homsand facies).
[2]
Geographically, this formation is located in the central southernmost part of the
Franconian Jura, on the left bank of the
Danube, roughly between the towns of
Wellheim and
Neuburg in
Bavaria.
The formation is commercially quarried for siliceous earth, which has a variety of applications.
The formation infills karstic voids found in Upper Jurassic limestones. Its upper contact is with either Miocene Upper Freshwater Molasse clays and marls or Pleistocene glacial deposits [3] while the lower contact is with the Jurassic limestones, or the Lower Cretaceous Schutzfels Formation, a terrestrial unit which also infills the karstic terrain.
The Wellheim Formation was formed in a quiet water environment
[4] by deposition of
pelagic sediments into a number of submerged karsts in the
ocean floor over several million years.
[5] Wilmsen et al (2010) identified the primary sediment composition as sandy and
spiculitic sediments, with notably little
terrigenous input.
[4]
It has since been classified as an
Opoka type marine deposit, a term that is primarily used to refer to Upper Cretaceous sponge spicule rich siliceous limestones found in Poland and western Ukraine.
[6]
Lüttig (2007) called the scientific view of the formation of the Neuburg Kieselerde Member "contested" [a] [7] however that position has not been supported by subsequent authors.
The Wellheim Formation is fossiliferous with the Neuburg Kieselerde Member having one of the most diverse invertebrate assemblages in the Danubian Cretaceous Group. [8] Schneider et al. (2013) mapped fossil yielding localities associated with this member in a rough triangle between Wellheim, Rennertshofen and Neuburg. [9]
It was deposited between about 93 to 98 million years ago during the
Cenomanian, the lowest stage of the
Upper Cretaceous.
The
index fossil associated with these
sediments is
Inoceramus crippsi, a wing-shaped (
pteriomorph) salt-water
bivalve.
[10]
Mining of Neuburg Kieselerde Member sediments takes place at an industrial scale around Neuburg an der Donau. The products are marketed under the umbrella term siliceous earth ( German: Kieselerde). The sediment is used as a filler material, [11] [12] [13] an abrasive and polishing medium, [14] a paint and varnish additive [15] and as a nutritional supplement. [16] [17]
It is generally composed of silicic acid (80 percent by weight or less) and kaolinite. [18]
In 2015, 55,000 tons of the purified material were produced. This required the open-pit mining of 120,000 tons of raw siliceous earth. [19]
The producer has claimed a non-biogenic, mineral origin for their product, [18] while most other sources assert a biogenic origin for the material. [b] [8] Substances called siliceous earths are usually defined as having a biogenic origin, [20] with material of a similar composition usually being termed diatomaceous earth.
The producer also has repeatedly claimed a unique "one-of-a-kind worldwide" status of their product, [21] [22] but Lüttig refuted this in 2007 for the material that is produced, saying that several similar material deposits are known, naming Heiligenhafen Kieselgestein as an example. On the other hand he agreed that the very special formation circumstances could indeed be called unique. [7]
It has historically been used for the production of glass, [23] ceramics [17] and color pigments like ultramarine.
Wellheim Formation | |
---|---|
Stratigraphic range: upper Cenomanian to lower Turonian [1] | |
![]() Siliceous earth quarrying of the Wellheim Formation near Neuburg | |
Type | Geological formation |
Unit of | Danubian Cretaceous Group |
Sub-units | basal marine sandstone, Neuburg Kieselerde Member, Homsand facies [2] |
Underlies | Upper Freshwater Molasse Formation or Pleistocene loams |
Overlies | Schutzfels Formation or Upper Jurassic limestone |
Area | southern Franconian Jura, Upper Bavaria [1] |
Thickness | up to 130 metres (430 ft) |
Lithology | |
Primary | spiculitic silt, fine and medium sands, fine-grained silica (Kieselerde) [1] |
Other | silicified conglomerate |
Location | |
Country | Germany |
Extent | 200 km2 (77 sq mi) |
Type section | |
Named for | Wellheim |
Named by | B. Niebuhr, T. Pürner, and M. Wilmsen |
Location | open pit mines near Wellheim, Germany |
Year defined | 2009 |
Country | Germany |
The Wellheim Formation is a geological formation in southern Germany deposited during the Cenomanian to earliest Turonian stages of the Upper Cretaceous.
The Formation is subdivided into three member units: unnamed basal marine sandstone, the Neuburg Kieselerde Member, and an upper silicified conglomerate (Homsand facies).
[2]
Geographically, this formation is located in the central southernmost part of the
Franconian Jura, on the left bank of the
Danube, roughly between the towns of
Wellheim and
Neuburg in
Bavaria.
The formation is commercially quarried for siliceous earth, which has a variety of applications.
The formation infills karstic voids found in Upper Jurassic limestones. Its upper contact is with either Miocene Upper Freshwater Molasse clays and marls or Pleistocene glacial deposits [3] while the lower contact is with the Jurassic limestones, or the Lower Cretaceous Schutzfels Formation, a terrestrial unit which also infills the karstic terrain.
The Wellheim Formation was formed in a quiet water environment
[4] by deposition of
pelagic sediments into a number of submerged karsts in the
ocean floor over several million years.
[5] Wilmsen et al (2010) identified the primary sediment composition as sandy and
spiculitic sediments, with notably little
terrigenous input.
[4]
It has since been classified as an
Opoka type marine deposit, a term that is primarily used to refer to Upper Cretaceous sponge spicule rich siliceous limestones found in Poland and western Ukraine.
[6]
Lüttig (2007) called the scientific view of the formation of the Neuburg Kieselerde Member "contested" [a] [7] however that position has not been supported by subsequent authors.
The Wellheim Formation is fossiliferous with the Neuburg Kieselerde Member having one of the most diverse invertebrate assemblages in the Danubian Cretaceous Group. [8] Schneider et al. (2013) mapped fossil yielding localities associated with this member in a rough triangle between Wellheim, Rennertshofen and Neuburg. [9]
It was deposited between about 93 to 98 million years ago during the
Cenomanian, the lowest stage of the
Upper Cretaceous.
The
index fossil associated with these
sediments is
Inoceramus crippsi, a wing-shaped (
pteriomorph) salt-water
bivalve.
[10]
Mining of Neuburg Kieselerde Member sediments takes place at an industrial scale around Neuburg an der Donau. The products are marketed under the umbrella term siliceous earth ( German: Kieselerde). The sediment is used as a filler material, [11] [12] [13] an abrasive and polishing medium, [14] a paint and varnish additive [15] and as a nutritional supplement. [16] [17]
It is generally composed of silicic acid (80 percent by weight or less) and kaolinite. [18]
In 2015, 55,000 tons of the purified material were produced. This required the open-pit mining of 120,000 tons of raw siliceous earth. [19]
The producer has claimed a non-biogenic, mineral origin for their product, [18] while most other sources assert a biogenic origin for the material. [b] [8] Substances called siliceous earths are usually defined as having a biogenic origin, [20] with material of a similar composition usually being termed diatomaceous earth.
The producer also has repeatedly claimed a unique "one-of-a-kind worldwide" status of their product, [21] [22] but Lüttig refuted this in 2007 for the material that is produced, saying that several similar material deposits are known, naming Heiligenhafen Kieselgestein as an example. On the other hand he agreed that the very special formation circumstances could indeed be called unique. [7]
It has historically been used for the production of glass, [23] ceramics [17] and color pigments like ultramarine.