Statistical analysis of till fabric: methodology, local and regional variability (with particular reference to the north Yorkshire till cliffs)

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Abstract
Problems connected with the sampling, interpretation and visual appraisal of till fabrics are discussed. Methods of statistical analysis are reviewed and a methodology for till fabrics presented. Fifty till fabrics from closely controlled sites allow a discussion of within- and between-site variability for this section of the Yorkshire coast. It is suggested that all the glacial deposits are of Newer Drift age. The till sequence can be divided into a basal shale-charged deposit and an upper dark red/brown till. Englacial or sub-glacial water-lain sands are also common and varved clays locally separate till sheets. Results indicate that till fabrics are characterized by low within-site precision, i.e. there is a considerable degree of orientation scatter, although dips are more compact. Between-site variability is moderate and is greater vertically within a deposit than laterally. Rotation of the data allows the typically bimodal distribution to be concentrated and analysed in the most efficient manner. A series of models are proposed for a rational description of fabric types and are linked to fabric genesis. Ice-flow, as revealed by the till fabrics, was north-south except in the vicinity of Robin Hood's Bay where an east–west component predominates. The reason for this difference is discussed. Distinct orientation and dip directions are more likely caused by flow within the till matrix rather than the ice/till contact.

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