Alum Shale Formation
Stratigraphic range: Cambrian-Ordovician

Type| Geological formation
Thickness| up to 160 m
Lithology
Primary| Black shale
Other| Shale, oil shale
Location
Country| Sweden, Denmark, Norway

The Alum Shale Formation (also known as alum schist and alum slate) is a formation of black shale of Miaolingian (Middle Cambrian) to Tremadocian (Lower Ordovician) in age found predominantly in southern Scandinavia.[1][2] It is shale or clay slate containing pyrite. Decomposition of pyrite by weathering forms sulfuric acid, which acts on potash and alumina constituents to form alum, which often occurs as efflorescences on the rock outcrop.

As the formation contains kerogen originated from algae, it is also classified as marinite-type oil shale. At the same time it is rich in aromatic hydrocarbon attributed to post-depositional irradiation damage to saturated hydrocarbons, induced by uranium concentration in the shale.[3] Alum shale also contains enhanced levels of radium as a result of uranium decay.[4] Between 1950 and 1989, Sweden used alum shale for the uranium production.[5]

8502 specimens of trilobite-agnostoid fauna were found in the Furongian strata of this formation in Bornholm, Denmark. Most of them are disarticulated sclerites. Described gerena include Ctenopyge, Eurycare, Leptoplastus, Olenus, Parabolina, Peltura, Protopeltura, Sphaerophthalmus, Lotagnostus and Triangulopyge.[6]

## See also

* Orsten, a lagerstätte in the Alum Shale Formation

## References

1. ↑ Nielsen A.T. & Schovsbo N.H. (2007). "Cambrian to basal Ordovician lithostratigraphy in southern Scandinavia". Bulletin of the Geological Society of Denmark 53: 82–84. http://2dgf.dk/xpdf/bull53-1-47-92.pdf.
2. ↑ Zhengfu Zhao, Nicolas R. Thibault, Tais W. Dahl, Niels H. Schovsbo, Aske L. Sørensen, Christian M. Ø. Rasmussen, Arne T. Nielsen (13 April 2022). "Synchronizing rock clocks in the late Cambrian". Nature 13 (1990): 1990. doi:10.1038/s41467-022-29651-4. PMID 35418121. Bibcode: 2022NatCo..13.1990Z.
3. ↑ Peters, Kenneth E.; Walters, Clifford C.; Moldowan, J. Michael (2005). The biomarker guide. Cambridge University Press. p. 777. ISBN 978-0-521-83762-0. https://books.google.com/books?id=qk8anEDZykwC&q=alum+shale&pg=PA777. Retrieved 2009-05-30.
4. ↑ Stranden, E.; Strand, T. (1988). "Radon in an Alum Shale Rich Norwegian Area". Radiation Protection Dosimetry (Oxford University Press) 24 (1–4): 367–370. doi:10.1093/oxfordjournals.rpd.a080304.
5. ↑ Dyni, John R. (2006). "Geology and resources of some world oil shale deposits. Scientific Investigations Report 2005–5294". United States Department of the Interior, United States Geological Survey. http://pubs.usgs.gov/sir/2005/5294/pdf/sir5294_508.pdf. Retrieved 2009-05-30.
6. ↑ Arne Thorshøj Nielsen, Line Frigaard Andersen (2021). "Furongian (upper Cambrian) trilobites and agnostoids from the Alum Shale Formation of Bornholm, Denmark: revised taxonomy and biostratigraphy". Bulletin of the Geological Society of Denmark 69: 123–213. doi:10.37570/bgsd-2021-69-08. ISSN 2245-7070. https://2dgf.dk/xpdf/bull69-123-213.pdf.

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Geology of Fennoscandia

Paleosurfaces|

* Borsu surface
* Hardangervidda
* Muddus plains
* Paleic surface
* Ostrobothnian Plain
* South Småland peneplain
* 300 m peneplain
* 200 m peneplain
* Strandflat
* Sub-Cambrian peneplain
* Sub-Mesozoic hilly relief

Sedimentary cover|

| Moraines|

* Billingen terminal moraine
* Pulju moraine
* Rogen moraine
* Salpausselkä
* Sevetti moraine
* Skövde terminal moraine
* Trollgarden
* Veiki moraine

|

Sedimentary rock|

* Alum Shale Formation
* Hedmark Group
* Jotnian sedimentary rock
* Reusch's Moraine
* Visingsö Group

Structures|

| Faults and shear zones|

* Burträsk Fault
* Iapetus Suture
* Lainio Fault
* Nordfjord-Sogn Detachment
* Pärvie Fault
* Protogine Zone
* Sorgenfrei-Tornquist Zone
* South Finland Shear Zone

|

Large impact craters|

* Dellen
* Gardnos crater
* Granby crater
* Hummeln structure
* Lappajärvi
* Lockne crater
* Lumparn
* Mien
* Ritland crater
* Siljan Ring
* Sääksjärvi
* Söderfjärden
* Suvasvesi
* Tvären

Morphostrucures|

* Central Swedish lowland
* Gulf of Bothnia rift
* Lake Inari graben
* Lake Ladoga graben
* Lofoten horst
* Muhos Graben
* Norrland terrain
* Omberg horst
* Oslo Graben
* Scandinavian Mountains
* Scanian horsts
* South Swedish Dome
* Vättern graben
* White Sea Rift System

Lesser igneous provinces|

* Alnö Complex
* Central Skåne Volcanic Province
* Fen Complex
* Kattsund-Koster dyke swarm
* Kola Alkaline Province
* Norra Kärr
* Rapakivi granites
* Särna Alkaline Complex
* Satakunta dyke swarms

Provinces and orogens|

* Belomorian Province
* Blekinge-Bornholm Province
* Kola Province
* Scandinavian Caledonides
* Svecofennian Province
* Sveconorwegian Province
* Transscandinavian Igneous Belt
* Timanide Orogen
* Western Gneiss Region

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