Cowie Formation
{{Short description|Geological formation in Scotland}}
{{Use dmy dates|date=April 2022}}
{{Infobox rockunit
| name = Cowie Formation
| image = Shoreline near Cowie - geograph.org.uk - 1724573.jpg
| caption = Shoreline near Cowie
| type = Formation
| age = late Wenlock to early Ludlow or Lochkovian
| period = Silurian
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| region = Scotland
| country = United Kingdom
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The Cowie Formation is geological formation located on the Highland Boundary Fault between the fishing village of Cowie and Ruthery Head, in Aberdeenshire, Scotland.{{Cite web |title=Earth Science Outdoors Teachers' Guide, Cowie, Stonehaven, Aberdeenshire |url=https://www.geowalks.co.uk/eso/CowieTeachersGuide-v4.pdf |access-date=30 December 2022 |website=geowalks.co.uk |publisher=Scottish Earth Science Education Forum |publication-date=23 October 2009}} Age of this formation is controversial, that was originally estimated at the Middle Silurian, Wenlock to Ludlow, but zircon geochronology shows the Early Devonian, Lochkovian instead.{{Cite journal |last1=Suarez |first1=Stephanie E. |last2=Brookfield |first2=Michael E. |last3=Catlos |first3=Elizabeth J. |last4=Stöckli |first4=Daniel F. |date=2017-06-28 |title=A U-Pb zircon age constraint on the oldest-recorded air-breathing land animal |journal=PLOS ONE |volume=12 |issue=6 |pages=e0179262 |doi=10.1371/journal.pone.0179262 |issn=1932-6203 |pmc=5489152 |pmid=28658320 |doi-access=free }} In study published in 2023, according to spore microfossils and additional zircon data, the Middle Silurian, late Wenlock age is suggested again.{{Cite journal |last=Wellman |first=Charles H. |last2=Lopes |first2=Gilda |last3=McKellar |first3=Zoë |last4=Hartley |first4=Adrian |date=2023-10-24 |title=Age of the basal ‘Lower Old Red Sandstone’ Stonehaven Group of Scotland: The oldest reported air-breathing land animal is Silurian (late Wenlock) in age |url=https://www.lyellcollection.org/doi/10.1144/jgs2023-138 |journal=Journal of the Geological Society |language=en |doi=10.1144/jgs2023-138 |issn=0016-7649|doi-access=free |hdl=2164/22754 |hdl-access=free }} However, in 2024 it is considered as unsustainable because this conclusion is based on adjacent structurally separated block with different stratigraphy and sedimentology to the block with fossil productive Fish Bed.{{Cite journal |last=Brookfield |first=M. E. |last2=Catlos |first2=E. J. |last3=Garza |first3=H. |date=2024-07-07 |title=The oldest ‘millipede’-plant association? Age, paleoenvironments and sources of the Silurian lake sediments at Kerrera, Argyll and Bute, Scotland |url=https://www.tandfonline.com/doi/full/10.1080/08912963.2024.2367554 |journal=Historical Biology |language=en |pages=1–13 |doi=10.1080/08912963.2024.2367554 |issn=0891-2963|url-access=subscription }} This formation preserves fossils, including a millipedes such as Pneumodesmus and Cowiedesmus that were discovered by Mike Newman in 2001,{{Cite web |date=2004-01-26 |title=One big step for Scottish millipedes |url=http://www.theguardian.com/uk/2004/jan/26/science.highereducation1 |access-date=2022-12-30 |website=the Guardian |language=en}} and some agnathan like Cowielepis.{{Cite journal |last=Blom |first=Henning |date=2008 |title=A New Anaspid Fish from the Middle Silurian Cowie Harbour Fish Bed of Stonehaven, Scotland |url=https://www.jstor.org/stable/20490987 |journal=Journal of Vertebrate Paleontology |volume=28 |issue=3 |pages=594–600 |jstor=20490987 |issn=0272-4634}}
Geological History
The sandstones and mudstones that form the outcrops along the coast were mostly laid down by braided rivers crossing a semi-arid, low-relief landscape.
One particularly exciting find was made here in 2003 when a fragment of a fossil millipede was identified as the earliest known air-breathing animal in the world. It is celebrated in a display board on the seafront at Cowie.
One unusual feature of these layered sedimentary rocks is that they are tilted to the southeast at a very steep angle and therefore are seen edge on in the outcrops on the foreshore and is formally known as the Strathmore Syncline. When these layers are followed southeast for several kilometers, the degree of tilting towards the southeast is seen to decrease until the layers are almost horizontal and then steepen again as they begin to tilt towards the northwest, thus defining a broad U-shaped fold in the rock strata known as a syncline.
The tilting of the strata took place when two regions of the Earth's lithosphere (the relatively rigid outer layer of the planet, which includes the crust and uppermost Mantle) were subjected to strong compressive forces over a long period. This took place between about 500 and 400 million years ago when two plates were in collision, bringing together the ancient continents of Avalonia and Laurentia. One consequence of this collision was the buckling of the thick deposits of sedimentary rocks that had, at that time, recently accumulated in this northern part of the Midland Valley.
Paleobiota
According to these references{{Cite journal |last=Westoll |first=T. S. |date=1947 |title=XIII.—A New Cephalaspid Fish from the Downtonian of Scotland, with Notes on the Structure and Classification of Ostracoderms |url=https://www.cambridge.org/core/journals/earth-and-environmental-science-transactions-of-royal-society-of-edinburgh/article/abs/xiiia-new-cephalaspid-fish-from-the-downtonian-of-scotland-with-notes-on-the-structure-and-classification-of-ostracoderms/AB5FBA3707A9C422F4ED0E3589D5827C |journal=Earth and Environmental Science Transactions of the Royal Society of Edinburgh |language=en |volume=61 |issue=2 |pages=341–357 |doi=10.1017/S0080456800004786 |issn=2053-5945|url-access=subscription }}{{cite journal |last=Størmer |first=Leif |year=1935 |title=Dictyocaris, Salter, a large crustacean from the Upper Silurian and Downtonian |url=https://njg.geologi.no/images/NJG_articles/NGT_15_267-298.pdf |journal=Extract Norsk Geol. Tisskr |volume=15 |pages=267–298}}{{Cite journal |last1=Wilson |first1=Heather M. |last2=Anderson |first2=Lyall I. |date=2004 |title=Morphology and taxonomy of Paleozoic millipedes (Diplopoda: Chilognatha: Archipolypoda) from Scotland |url=https://www.cambridge.org/core/journals/journal-of-paleontology/article/abs/morphology-and-taxonomy-of-paleozoic-millipedes-diplopoda-chilognatha-archipolypoda-from-scotland/1F7B935D32BB541D12F453F583399DE0 |journal=Journal of Paleontology |language=en |volume=78 |issue=1 |pages=169–184 |doi=10.1666/0022-3360(2004)078<0169:MATOPM>2.0.CO;2 |issn=0022-3360|url-access=subscription }} otherwise noted.
{{paleobiota-key-compact}}
= Vertebrates =
| class="wikitable sortable" style="background:white; width:100%;"
! colspan="4" align="center" |Vertebrates |
| Genus
!Species !Notes !Images |
|---|
| Cowielepis
|C. ritchiei |An anaspid. |
| Hemicyclaspis
|Indeterminate, once described as "Hemiteleaspis heintzi" |An osteostracan. |
| Phialaspis
|P. sp. | rowspan="2" |Traquairaspidiform. | |
| Traquairaspis
|T. campbelli |
= Aquatic arthropods =
| class="wikitable sortable" style="background:white; width:100%;"
! colspan="4" align="center" |Aquatic arthropods |
| Genus
!Species !Notes !Images |
|---|
| Ceratiocaris
|C. sp. |A phyllocarid. | |
| Dictyocaris
|D. slimoni |Most common fossils from this site, considered as phyllocarid, while genus itself at least from other sites is identified as algae instead.{{Cite journal |last=Lamsdell |first=James C. |date=2020-09-01 |title=A chasmataspidid affinity for the putative xiphosuran Kiaeria Størmer, 1934 |url=https://doi.org/10.1007/s12542-019-00493-8 |journal=PalZ |language=en |volume=94 |issue=3 |pages=449–453 |doi=10.1007/s12542-019-00493-8 |issn=1867-6812|url-access=subscription }} | |
| Nanahughmilleria
|N. norvegica | rowspan="3" |Eurypterids. |
| Pterygotus
|P. sp. | |
| Indeterminate
|Hughmilleria sp., cf. H. (?) lata | |
= Terrestrial arthropods =
| class="wikitable sortable" style="background:white; width:100%;"
! colspan="4" align="center" |Terrestrial arthropods |
| Genus
!Species !Notes !Images |
|---|
| Albadesmus
|A. almondi | rowspan="5" |Millipedes. | |
| Archidesmus
|A. sp. | |
| Cowiedesmus
|C. eroticopodus | |
| Pneumodesmus
|P. newmani |
| Indeterminate
|cf. Kampecaris sp. | |
See also
{{Portal|Earth sciences|Scotland|Paleontology}}
References
{{Reflist}}
- {{cite web|title= Fossilworks: Gateway to the Paleobiology Database|author= ((Various Contributors to the Paleobiology Database))|url= https://www.fossilworks.org|access-date= 17 December 2021}}
Category:Geologic formations of Scotland
Category:Silurian System of Europe
Category:Silurian southern paleotropical deposits
Category:Devonian southern paleotropical deposits
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{{Silurian-stub}}{{Devonian-stub}}{{Scotland-stub}}