Soom Shale

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title: "Soom Shale" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["soom-shale", "geologic-formations-of-south-africa", "ordovician-system-of-africa", "hirnantian", "shale-formations", "paleontology-in-south-africa"] description: "Late Ordovician lagerstatte formation in South Africa" topic_path: "philosophy" source: "https://en.wikipedia.org/wiki/Soom_Shale" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Late Ordovician lagerstatte formation in South Africa ::

::data[format=table title="Infobox rockunit"]

Field	Value
name	Soom Shale
image	Soom Shale.jpg
caption	Typical lithological features of the Soom shale, note the frequent beds of white quartz
period	Hirnantian
age	Hirnantian
unitof	Cederberg Formation, Table Mountain Group
lithology	Shale
thickness	10 -
overlies	Pakhuis Tillite
underlies	Disa Siltstone
region	Western Cape
country	South Africa
coordinates
paleocoordinates
map	{{Location map+
relief	1
width	250
float	center
lat_deg	-33.0
lon_deg	19.0
mark	Dark Green 004040 pog.svg
marksize	12
::

| name = Soom Shale | image = Soom Shale.jpg | caption = Typical lithological features of the Soom shale, note the frequent beds of white quartz | period = Hirnantian | age = Hirnantian | unitof = Cederberg Formation, Table Mountain Group | lithology = Shale | thickness = 10 - | overlies = Pakhuis Tillite | underlies = Disa Siltstone | region = Western Cape | country = South Africa | coordinates = | paleocoordinates = | map = {{Location map+ | South Africa | relief = 1 | width = 250 | float = center | places = | lat_deg = -33.0 | lon_deg = 19.0 | mark = Dark Green 004040 pog.svg | marksize = 12

The Soom Shale is a member of the Late Ordovician (Hirnantian) Cederberg Formation (Table Mountain Group) in South Africa, renowned for its remarkable preservation of soft-tissue in fossil material. Deposited in still waters, the unit lacks bioturbation, perhaps indicating anoxic conditions.

It overlies the Pakhuis tillite and is overlain by the Disa Siltstone.

It contains typical Ordovician microfossils, such as chitinozoa, acritarchs and spores, and its shelly fauna is also typical of this time period.

Its macrofauna comprises pelagic organisms that sank rapidly to a barren sea floor. These include brachiopods, eurypterids, conodonts, nektaspids, trilobites, a lobopodian and orthoconic cephalopods.

Environment of formation

The environment of deposition is considered to be anoxic and occasionally euxinic cold bottom waters, as indicated by the lack of bioturbation and most epibenthic fauna, besides a small amount of transiently colonizing brachiopods during temporary oxic conditions. It was deposited in the immediate aftermath of the Hirnantian glaciation, the most likely primary cause of the Late Ordovician mass extinction.

Preservation

The preservation of fossils in the Soom Shale is the opposite of that of normal fossil deposits. Things that in typical preservation conditions are not preserved in the fossil record like soft tissue are preserved in exquisite detail. While hard parts (exoskeleton, etc.) that are normally preserved in the fossil record are demineralized, and are therefore by comparison poorly preserved, usually being preserved in the form of a mould. There is almost no taphonomic distortion, with little evidence of transport, current alignment and no evidence of scavenging. The process of preservation for soft tissues is under debate, but possibly could involve replacement by aluminosilicates, but this could just be an artifact of diagenesis and metamorphism.

Biota

::data[format=table]

Genus	Type of organism	Images
Promissum	Conodont	[[File:Promissum_NT_small.jpg
Notiodella	Conodont
Onychopterella	Eurypterid	[[File:Onychopterella augusti restoration.png
Soomaspis	Liwiid Nektaspid	[[File:Soomaspis_drawing.pdf
Keurbos	Enigmatic euarthropod	[[File:Holotype Specimen of Keurbos susanae.jpg
Mucronaspis	Dalmanitid Trilobite
Soomicaris	Archaeostracan Phyllocarid
Myodoprimigenia	Myodocope Ostracod
Palaeoglossa	Obolid Brachiopod
Trematis	Trematid Brachiopod
Kosoidea	Discinid Brachiopod
Plectothyrella	Rhynchonellid Brachiopod
Siphonacis	Incertae sedis
Undescribed Agnathan	Jawless Fish
Undescribed Lobopodian	Lobopodian
::

References

References

1. (1999). "Orthoconic cephalopods and associated fauna from the late Ordovician Soom Shale Lagerstatte, South Africa". Palaeontology.
2. (2001). "Palaeobiology II".
3. (2009). "Brachiopoda from the Soom Shale Lagerstätte (Upper Ordovician, South Africa)". Journal of Paleontology.
4. (2013). "A 17-element conodont apparatus from the Soom Shale Lagerstätte (Upper Ordovician), South Africa". Palaeontology.
5. (May 2009). "AN ORDOVICIAN LOBOPODIAN FROM THE SOOM SHALE LAGERSTÄTTE, SOUTH AFRICA". Palaeontology.
6. (2017). "The late Ordovician Soom Shale Lagerstätte: an extraordinary post-glacial fossil and sedimentary record". Journal of the Geological Society.
7. Gabbott, Sarah E.. (2025). "A new euarthropod from the Soom Shale (Ordovician) Konservat-Lagerstätte, South Africa, with exceptional preservation of the connective endoskeleton and myoanatomy". Papers in Palaeontology.

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