CONVOLUTE LAMINATION AND OTHER STRUCTURES FROM THE LOWER COAL MEASURES OF YORKSHIRE

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Abstract
SUMMARY: Several deformational sedimentary structures are recorded from the non‐marine sandstones of the Lower Coal Measures of Yorkshire. Some of these structures may be termed convolute lamination and for others the term corrugated lamination is proposed. The scope and synonyms of convolute lamination are discussed and both terms are defined and illustrated. The essential difference between convolute lamination and corrugated lamination is the absence of an overall anticline‐syncline morphology in the latter. Rupture of lamination through most of the thickness of the deformed horizons give rise to rupture structures.A petrological investigation of the sediments showed slight variations in both grain size and mineralogy within individually deformed horizons. The structures are considered to be the result of load casting, caused by heterogeneity of the sediment, and/or thixotropic behaviour.