|
The Cowie Formation is a geologic formation in Scotland. It preserves fossils dating back to the Silurian period. == Geological History== The sandstones and mudstones that form the outcrops along the coast from Cowie to Ruthery Head were mostly laid down by braided rivers 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 was identified as the earliest known air-breathing animal in the world. It is celebrated in a display board on the sea-front at Cowie. One unusual feature of these layered sedimentary rocks is that they have been tilted to the south-east 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 south-eastwards for several kilometres, the degree of tilting towards the SE is seen to decrease until the layers are near horizontal and then steepen again as they begin to tilt towards the NW, 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Cowie Formation」の詳細全文を読む スポンサード リンク
|