The Cowie Formation is a mid-

Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago (Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozoi ...

period

geological formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics (lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock expo ...

located on the Highland Boundary Fault between the fishing village of Cowie and Ruthery Head, in

Aberdeenshire Aberdeenshire ( sco, Aiberdeenshire; gd, Siorrachd Obar Dheathain) is one of the 32 council areas of Scotland. It takes its name from the County of Aberdeen which has substantially different boundaries. The Aberdeenshire Council area incl ...

Scotland Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a border with England to the southeast and is otherwise surrounded by the Atlantic Ocean to th ...

. This formation preserves

fossils A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

, including a 420 million-year-old millipede ('' Cowiedesmus'') that was discovered by Mike Newman in 2001.

Geological History

The

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates ...

s and mudstones that form the outcrops along the coast were mostly laid down by

braided river A braided river, or braided channel, consists of a network of river channels separated by small, often temporary, islands called braid bars or, in English usage, '' aits'' or ''eyots''. Braided streams tend to occur in rivers with high sedime ...

s crossing a semi-arid, low-relief landscape. Rare fossils contained in one particular layer near Cowie Harbour indicate that these rocks are over 428 million years old and belong to the mid-Silurian period. One particularly exciting find was made here in 2003 when a fragment of a fossil

millipede Millipedes are a group of arthropods that are characterised by having two pairs of jointed legs on most body segments; they are known scientifically as the class Diplopoda, the name derived from this feature. Each double-legged segment is a re ...

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 A lithosphere () is the rigid, outermost rocky shell of a terrestrial planet or natural satellite. On Earth, it is composed of the crust and the portion of the upper mantle that behaves elastically on time scales of up to thousands of years ...

(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 Avalonia was a microcontinent in the Paleozoic era. Crustal fragments of this former microcontinent underlie south-west Great Britain, southern Ireland, and the eastern coast of North America. It is the source of many of the older rocks of We ...

and

Laurentia Laurentia or the North American Craton is a large continental craton that forms the ancient geological core of North America. Many times in its past, Laurentia has been a separate continent, as it is now in the form of North America, althoug ...

. 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.

References

* Geologic formations of Scotland Silurian System of Europe Silurian Scotland Silurian southern paleotropical deposits Devonian southern paleotropical deposits {{Scotland-stub

Geological History

See also

References