Joints and related structures have been used to diagnose components of the Mesozoic and Cenozoic structural history of central eastern England from South Humberside southwards to Norfolk. New data on joint orientation, spacing, geometry, and architecture have been collected from suitable lithologies, mainly the Lincolnshire Limestone Formation (Bajocian, Middle Jurassic) and the Chalk Group (Cenomanian, Upper Cretaceous). Field observations have provided an extensive data base on the nature, occurrence and character of joints. These data have been supplemented by observations from previous studies on exposures no longer available. Orientation data have been subjected to a rigorous statistical analysis procedure. This has involved plotting on equal area nets, determination of eigenvectors and associated distribution analysis, cluster analysis of the predominant two dimensional components to identify joint sets, and individual characterisation of separate sets in close conjunction with field observations. The cluster analysis technique has been newly designed for this study. Strength testing has been conducted on samples of the Chalk Group. Consistent sets of joints are recognised over most of the region striking roughly NW and NE. These joints are present in both Jurassic and Cretaceous units. Both sets, however, change in geometry and architecture from bimodal in the south (Norfolk) to unimodal in the north (South Humberside). A degree of variation in architecture, geometry, and character also seen between the different lithologies observed. Spacing statistics also vary from exponential in the south to more normal in the north. Within this, the NE joint set is more notably exponential than the NW joint set. Corresponding variations are also seen in the results of statistical and distribution analyses. The literature on brittle failure has been critically reviewed, to guide interpretation of the geometries observed. The two main sets are interpreted as being inclined and parallel joints, based particularly on the absence of surface fractographic features and joint geometries. It is considered from geometric criteria that these joints formed coevally.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:599520 |
| Date | January 1997 |
| Creators | Goodwin, A. M. |
| Publisher | University of Cambridge |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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