Humberside Geologist no 8
published 1991
In the past the numerous small chalk exposures seen along the sloping sides in some of the dales of the Yorkshire Wolds have received little attention from geologists, as a result the stratigraphy of these areas is poorly known and has not been previously described. Thixendale provides a classic succession for study and a suggested stratigraphical sequence is here proposed, based on the measurements taken of the brief exposures along the sides of the dale.
During June 1989 Mike Home and Lynden Emery decided to undertake the very difficult and laborious task of measuring the chalk succession in Thixendale by following the path down the side of the dale and picking out any visible signs of chalk, flints and marls which could be recorded between grassed-over sections.
Arising from this work a fragmented picture of the sequence emerged, showing a remarkable section of over 40 metres of chalk with numerous bands of flint, but lacking in essential marl marker horizons, mostly obscured due to the over- grown nature of some parts of the exposure. Only one single marl was exposed which fortunately provided a clue and helped in working out the succession.
The prominence of some of the major flint bands has provided the main marker horizons, which coupled with the knowledge of diagnostic fossils collected in the area previously (by F. Whitham), and the known horizons of related marl bands, has enabled the writer to erect a proposed first stratigraphic succession for this area of the Yorkshire Dales. The sequence at Thixendale appears to correlate in most respects with the composite succession of Wood & Smith (1978), and is based on the original fieldwork of the joint authors Mike Horne and Lynden Emery.
The stratigraphical position of the only visible marl band (Figure 1.) is provisionally placed at the North Ormsby Marl level as it occurs above three closely spaced semi and tabular flints, notably the Triple Tabular Flints (both horizons named by Wood & Smith(1978). The three Kiplingcotes Flints and the underlying Kiplingcotes Marls (also named by the latter authors), are well exposed in a small pit in the upper part of the dale about 700 metres along a track opposite Gills Farm near Fridaythorpe north of the A 166 (O.S. SE 846593), where typical species of Echinocorys gravesi occur and are found at a similar horizon at Enthorpe. This level also correlates with the higher flint bands noted by the joint authors and shown in the upper part of the section in Figure 1. A previous exposure close to the road junction at Thixendale village yielded a primitive early species of Echinocorys, of a type known to occur just below the Ravendale Flint. These two exposures provide the linking evidence for the lower and higher parts of the sequence in the dale, additionally, recent work on the single marl sample by Mike Horne suggests a Turonian dating for the microfaunas.
Tentative relative positions for the main marker marls are depicted in the proposed succession for Thixendale and future work in this area by members of the society may reveal the exact positions of the elusive marls and either support or discount this hypothesis.
References.
Wood, C.J. & Smith, E.G. 1978. Lithostratigraphical classification of the chalk in North Yorkshire, Humberside and Lincolnshire, Proceedings of the Yorkshire Geological Society 42, 263-287.
Wright, C.W. & Wright, E.V. 1942. The Chalk of the Yorkshire Wolds Proceedings of the Geologist's Association, London 53, 112-127.
copyright Hull Geological Society 2021