The Yorkshire Dogger

Abstract

The Lias-Oolite junction in Rosedale and Farndale is defined. The underlying Lias is folded into a pre-Oolite complex of shallow Caledonoid folds, wherein are preserved about 55 square miles of Yeoyilian strata in the Cleveland region. The Rosedale East and Sheriff's Pit ironstones, now exhausted, are included on field evidence with the Yeovilian and not the Dogger. They occur in the troughs of two structural basins of limited extent in the fold complex, while other basins hold ironstones of no economic value. It is unlikely that the depositional basin of the Rosedale ironstones extended far beyond the present limits of the dale. Within Rosedale its distribution was materially reduced by erosion from the crests of minor pre-Dogger folds, pebbles now phosphatised derived from the crests occurring in the base of the Dogger.

A three-fold sub-division of the Dogger is recognized. The Glaisdale Oolite is here of little importance; the lenticular Rosedale Sandstone represents sand trapped in the continued down-warping over Rosedale in early Dogger times. The most widely spread rock group, the Blakey Series, includes the important Black Shales at its base. Marked facies variation is recognized in the sandy upper part, which includes the Ajalon facies, the Green Flag facies, etc., which were earlier incorrectly regarded as in chronological succession.

The Rosedale magnetite-oolite is regarded as a sedimentary deposit underlying the Dogger.

The petrography of the several beds of the Lias-Oolite junction is briefly described.