Otterton Ledge
| Otterton Ledge | ||
 Outcrop of the Otter sandstone immediately east of the mouth of the Otter. |
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| Geographical location | ||
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| Coordinates | 50 ° 37 '48 " N , 3 ° 18' 17" W | |
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English Channel Otter |
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Otterton Ledge (also Otterton Point ) is a headland at the mouth of Otter in the English Channel , east of Budleigh Salterton in the county of Devon on the south coast of England .
location
The Otterton Ledge headland is about eighteen kilometers southeast of the city of Exeter and seven kilometers east of Exmouth , immediately east of the mouth of the Otter in the English Channel. To the west of the estuary is the scree beach of Budleigh Salterton. The otter estuary, a swampy landscape with reed beds, has been declared a nature reserve ( Site of Special Scientific Interest ).
geology
Otterton Ledge is part of the Jurassic Coast that stretches from Orcombe Point to Old Harry Rocks at Studland Bay . This 155 kilometer stretch of coastline was the first landscape in England to be declared a UNESCO World Heritage Site.
The rock layers of the Jurassic Coast are slightly tilted to the east. The geologically oldest rocks are therefore in the westernmost section of this coastal geotope . The mean age of the rocks gradually decreases towards the east. The natural outcrops along the coast form a largely continuous sequence, ranging from deposits of the Triassic , through those of the Jura to those of the Cretaceous period, and represents a geological period totaling around 185 million years. The storage room that received the sediment series from the Jurassic Coast at that time is the so-called Wessex Basin .
Since Otterton Ledge is relatively close to the western end of the Jurassic Coast, the older rocks are here in the sequence of this world natural heritage. These are red sandstones that are part of the Otter Sandstone Formation , which in turn is part of the Sherwood Sandstone Group . The sandstones were deposited in the Middle Triassic ( Anisium ) in a river plain under dry climatic conditions. The corresponding Triassic river system is referred to in the geological literature as the Budleighensis river system . The grains of sand contained in the otter sandstone were taken from the Budleighensis rivers e.g. Sometimes transported to the Wessex basin from a distance of 400 km from the area of today's Massif Central and ultimately deposited here.
Similar to the geologically older sandstones at Straight Point, a surf platform has formed in the relatively erosion-resistant sandstones of Otterton Ledge, which is located in front of the headland to the south.
The cliff at Otterton Ledge is part of the type profile of the otter sandstone.
The beach at Otterton Ledge and west of the Otter Estuary consists mainly of quartzite pebbles, which come from the conglomerates of the Budleigh Salterton Pebble Bed Formation, which stand in the cliff west of Budleigh Salterton, but not at Otterton Ledge. These conglomerates, which are of early Triassic age, were also deposited by the Budleighensis Rivers. However, the gradient was much steeper and the rivers had a significantly higher flow speed than when the otter sandstone was deposited.
paleontology
Fossil finds in the otter sandstone show that the banks of the Budleighensis rivers were made up of plants and that numerous vertebrates , mostly reptiles , also lived there. In the rocks of Otterton Ledge there are layers of fossil plant roots, so-called rhizo concretions . It is not about fossilization of roots, but rather calcareous crusts that formed in the soil around the roots of the plants during their lifetime. The limestone crusts, which only develop when there is a high rate of evaporation, testify to the warm, dry climate in which these plants grew.
The famous British evolutionary biologist Thomas Henry Huxley described the upper jaw of a rhynchosaur from the sandstone near Otterton Ledge in 1869 , which is now part of the genus Fodonyx .
Estuary of the Otter
The estuary of the Otter River, including the fertile lowland along the lower reaches, forms a mosaic of salt marshes , reed beds, swampy meadows and marshland . A wide variety of migratory birds, wild fowl and waders as well as butterflies and dragonflies live here. In addition to a wide variety of fish, the mullet also occurs in small schools , although it is a saltwater fish.
The reason for the formation of the marshland in the mouth area of the Otter are the pebbles weathered from the cliff that form the beach in front of Budleigh Salterton. A few centuries ago, the mouth of the Otter was a wide, navigable estuary . Otterton, about five kilometers upstream from today's estuary, was a seaport at that time. Due to strong storms and the associated strong waves and currents, however, more and more of the beach pebbles were shifted from the area of the outcrops of the Budleigh-Salterton conglomerates to the east in front of the exit of the estuary and increasingly sealed it off from the open sea . Therefore, today the river makes a sharp bend to the east before it finally reaches the English Channel. The estuary silted up more and more through the rubble barrier and the current state gradually developed.
The estuary is not open to the public, but there are footpaths on both the west and east sides and there are viewing platforms.
See also
Web links
- Ian West: Budleigh Salterton, Littleham Cove and Straight Point, Devon: Geology of the Wessex Coast. 2012 (richly illustrated online excursion guide)
Individual evidence
- ^ Dorset and East Devon Coast . UNESCO World Heritage Center. 2001. Retrieved October 19, 2010.
- ↑ a b Shane Tyrrell, Peter DW Haughton, A. Kate Souders, J. Stephen Daly, Patrick M. Shannon: Large-scale, linked drainage systems in the NW European Triassic: insights from the Pb isotopic composition of detrital K-feldspar . In: Journal of the Geological Society . tape 169 , no. 3 , 2012, p. 279-295 , doi : 10.1144 / 0016-76492011-104 .
- ↑ Data sheet of the Otter Sandstone Formation in the online encyclopedia of named rock units of the British Geological Survey
- ↑ Data sheet for the Otterton Point Fossillokality in the Paleobiology Database