THE PERMIAN SEQUENCE OF SOUTH-EAST DURHAM AND NORTH-EAST YORKSHIRE

Abstract

Introduction Professor Hollingworth has indicated the light in which we must view any regional or local sequence of which evaporites form a part. It is for me to discuss in general terms the geological setting of the evaporites in this particular area of Durham and Yorkshire. They occur mainly in the Magnesian Limestone formation of the Permian and in the overlying Permo-Triassic Marls. The general relationships of the various members of the sequence can be seen from the following stratigraphical table :— | | Approx. thickness in Ft. | |:--------------------------------------------------------------------------------------------------------------------------------------- | ------------------------ | | Upper Magnesian Limestone | 300–400 | | Hartlepool and Roker Dolomites. | | | Concretionary Limestones. | | | Flexible Limestones, dolomitic. | | | Middle Magnesian Limestone | 300 | | Dolomitic bryozoan and shelly reefs, with bedded but often highly brecciated dolomite replacing it on both eastern and western flanks. | | | Lower Magnesian Limestone | 200 | | Bedded dolomite and limestone. | | | Marl Slate | 0–12 | | Flaggy dolomite with fish, plants, and shell remains. | | | Yellow Sands | 0–180 | | Unconsolidated, false-bedded, round-grained sand. | | NORTH OF THE DARLINGTON FAULT Surfaces of unconformity are found at a number of different horizons in the sequence, one of the most marked being at the base of the Middle Limestone. | | Approx. thickness in Ft. | |:------------------------------------------------------------------------------------------------------- | ------------------------ | | Permo-Triassic Marls | 300–350 | | Upper Anhydrite | 10 | | Marl | 20 | | Main Salt | 100 | | Main Anhydrite | 45 | | Upper Magnesian Limestone | 75 | | Lower salt | 60 | | Lower Anhydrite | | Lower Magnesian Limestone: with much anhydrite in some areas | 600–700 | | Basement Beds, sometimes conglomeratic and with a development of the Marl Slate, especially in the west | Very variable | SOUTH OF THE DARLINGTON FAULT Definite correlation between these ...