Solent group
The Solent Group is a sedimentary group of the Hampshire Basin in southern England . It was deposited in the Upper Eocene and Lower Oligocene .
designation
The Solent group was named after the Solent ( English The Solent), an inlet of the English Channel that separates the north of the Isle of Wight from the mainland ( Hampshire ).
Occurrence
The main distribution area of the Solent group is the northern part of the Isle of Wight. The group is also due on the opposite mainland, its lower section is on the south coast of Hampshire from Milford on Sea to Lepe and inland in the New Forest to Lyndhurst .
stratigraphy
The Solent Group is the uppermost sedimentary group in the Hampshire Basin. After they were deposited, the sea finally withdrew from the Hampshire Basin. The Solent Group concordantly overlays the sediments of the Barton Group ( Becton Sand Formation ).
The Solent group is divided into three formations (from hanging to lying):
The group can reach a maximum thickness of 215 meters in the central part of the former deposit area (for example in the west of the Isle of Wight at Whitecliff Bay), but peripheral areas are usually not much more than 60 meters thick.
The deposited sediments originate mainly from the brackish and freshwater area , only the Colwell Bay member of the lower Headon Hill Formation shows a longer marine incursion in its lower section, as evidenced by stenohaline fossils. Short-term marine conditions are realized several times in the Bouldnor Formation, for example in the Bembridge Oyster Bed , in the Nematura Bed and several times in the Cranmore Member .
In terms of lithology , clays and silts predominate, interrupted by sand inclusions and occasional marl layers . Some limestone bands also occur, particularly in the Bembridge Limestone Formation, a freshwater limestone. The depositional environment consists of behind sand bars nearby lagoons , the rivers flowed. Immediately behind it are lakes located in a coastal plain .
Fossil content
In addition to many bivalves , gastropods , ostracods and various microfossils , the Solent group contains several horizons with rich plant material , including tree trunks and tree stumps up to 5 meters long in their living position. Even fish and reptiles are present. The mammal fauna found is very diversified and documents the effects of the Grande Coupure at the beginning of the Oligocene.
Age
The biostratigraphically determined age of the Solent group ranges between the Lower Pribonian and the Lower Rupelian , ie in the period 36 to 32 million years BP . Their sediments thus document a period of around 4 million years. It should be noted, however, that the sedimentation did not take place continuously because the group is penetrated by numerous gaps in the layer.
literature
- Gale, AS et al .: Correlation of Eocene-Oligocene marine and continental records: orbital cyclicity, magnetostratigraphy and sequence stratigraphy of the Solent Group, Isle of Wight, UK . In: Journal of the Geological Society . tape 163 . London 2006, p. 401-415 .
- Hooker, JJ et al .: Refined correlation of the UK Late Eocene-Early Oligocene Solent Group and of its climate history . In: Koeberl, C. & Montanari, A. (Eds.): GSA Special Paper . tape 452 , 2009, p. 179-196 .