Loading AI tools
Geological formation in Scotland From Wikipedia, the free encyclopedia
The Ballagan Formation is a geologic formation in Scotland and England. It preserves fossils dating back to the early part of the Carboniferous period (Tournaisian – early Visean).[1] Its name comes from the "Ballagan Beds" of Ballagan Glen, near Strathblane, which has a good example of this geological formation.[2]
Ballagan Formation | |
---|---|
Stratigraphic range: Tournaisian–Visean | |
![]() Exposure of alternating siltstone and dolomite layers of the Ballagan Formation in the bank of Tarras Water | |
Type | Formation |
Unit of | Inverclyde Group |
Underlies | Clyde Sandstone Formation |
Overlies | Kinnesswood Formation |
Area | Central Lowlands, Northern England |
Thickness | ~900 m |
Lithology | |
Primary | mudstone, cementstone, siltstone |
Other | sandstone |
Location | |
Region | Scotland |
Country | United Kingdom |
Type section | |
Named for | Ballagan Glen |
Named by | Browne, 1980 |
The Ballagan Formation was historically known as the Cementstone Group,[3][4] but more recently it has been placed as the middle formation of the Inverclyde Group.[5] This change was motivated by the recognition that the youngest parts of the Devonian Upper Old Red Sandstone (now known as the Kinnesswood Formation) were geologically continuous with the lowest parts of the Lower Carboniferous Calciferous Sandstone Measures (now known as the Ballagan and Clyde Sandstone formations). This interval of Devonian-Carboniferous overlap was named the Inverclyde Group, and the cementstone-rich "drab beds" in the middle of the group were renamed to the Ballagan Formation.[6] In Lothian, the Ballagan and Clyde Sandstone formations are sometimes known as the Tyninghame Formation.[7]
Many localities of the Ballagan Formation preserve exceptional fossils. The majority of fossiliferous sites are in the Midland Valley (particularly the Scottish Borders and East Lothian), in the southeast corner of Scotland.[5][8]
One of the earliest sites to be studied was the fish bed at Foulden, which hosts many well-preserved fish fossils, notably including endemic actinopterygians (ray-finned fish) and the first complete skeleton of a rhizodont.[9][10] Plants and arthropods also form a significant portion of Foulden fossils.[11][12][13][14] This site and its fish fossils were publicized by E.I. White in 1927,[15] and further excavations were performed by Stan Wood in 1980-1981.[16] The Foulden fish bed was the primary theme for volume 76 of the Transactions of the Royal Society of Edinburgh: Earth Sciences journal, published in 1985.[16][17][18]
Willie's Hole, near Chirnside, is another site known for its high quality of preservation. It was initially recognized for its crustacean fossils, forming "shrimp beds" akin to those observed throughout the later Scottish Carboniferous.[19] Willie's Hole has continued to produce well-preserved fossils of arthropods, fish, and partial tetrapod skeletons.[5][20][21][22]
By far the largest exposures of the Ballagan Formation occur along the coastal end cliffs of Burnmouth.[5][23][24] Tetrapod, fish, and arthropod fragments are common in several layers at Burnmouth, not just in fine-grained overbank deposits[20][22][25][26] but also coarse river channel conglomerates, an unusual mode of preservation.[27][28]
Tetrapod fossils have been found in the vicinity of Tantallon Castle.[5][29] Additional Midland Valley sites include Crumble Edge (along Whiteadder Water),[30] Coldstream,[5][31] Cockburnspath,[32][5] Cove (in Berwickshire),[31] and Whitrope Burn (near Hawick).[33] A few locales in nearby Northumberland, England encompass fossil-bearing outcrops of the Ballagan Formation, such as Berwick-upon-Tweed[34][35] Barrow Scar (near Alwinton),[31] and a borehole core at Norham.[23][24]
Some sites are also found along the west coast of Scotland. Auchenreoch Glen, near Dumbarton, was the collection site for the nearly complete type fossil of Pederpes finneyae, which was the oldest named tetrapod of the Carboniferous upon its discovery.[36] Diverse assemblages of fish teeth and other microfossils have been found at Ayrshire[37][31] and at Hawk's Nib and Mill Hole, on the Isle of Bute.[38]
The Ballagan Formation preserves a plethora of tetrapod, fish, and invertebrate fossils, reconstructing one of the most diverse continental ecosystems known from the Tournaisian stage. A variety of plant megafossils and spores are known from the Ballagan Formation.[11][39][37][40][41]
Seamless Wikipedia browsing. On steroids.
Every time you click a link to Wikipedia, Wiktionary or Wikiquote in your browser's search results, it will show the modern Wikiwand interface.
Wikiwand extension is a five stars, simple, with minimum permission required to keep your browsing private, safe and transparent.