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Title: The stratigraphy and coral fauna of the Ilfracombe beds in North Devon
Author: Holwill, Frederick James Winsor
Awarding Body: University of London
Current Institution: Imperial College London
Date of Award: 1965
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Early work relating to the Ilfracombe Beds of North Devon is reviewed and it is shown that many problems remain unsolved, for example, the age of the beds, the stratigraphical succession, and the structure. The coastline between Combe Martin and Ilfracombe has been mapped on the scale of 50 ins = 1 mile, and it is found that there are only two important limestone developments, each about 30 feet thick; the lower is the Jenny Start Limestone, which is of Upper Givetian age, and the higher is the David's Stone Limestone of Lower Frasnian age. There are two other thin, but mappable, limestone horizons, each between 2-5 feet thick; these are the Rillage Limestone (about 200 feet below the Jenny Start Limestone), and the Combe Martin Beach Limestone (lying between the two main ones). N.W.-S.E. dextral tear faults, probably of Tertiary age, and E-W normal and reverse strike faults, probably related to an early orogeny, displace the strata. The faults, combined with the very intense folding, have resulted in numerous repetitions and occasional omissions in the local successions. The full succession between the Hangman Beds and the top of the Ilfracombe Beds is summarized in tabular form. The second part of this thesis is a detailed study of the coral fauna, including a complete morphological study and revision of the genus Metriophyllum. 51 species of corals belonging to 23 genera are figured and described. Of these 20 are new species and many are recorded for the first time in North Devon. The coral fauna establishes the age of the main limestones with moderate certainty, but the intervening beds are unfossiliferous and it is, therefore, impossible to draw absolute boundaries.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available