From Daniels et al. 2019: https://doi.org/10.1144/sp494-2019-140
This geological cross section from Daniels et al. (2019) demonstrates how the Permian rocks built-up layer by layer, cycle by cycle along the Durham coast.
- The Raisby and Ford Formations are limestones which formed in deeper water and onlap the shallow reefs at the edge of the Zechstein Sea during the development of Zechstein cycle Z1 and sea-level rise.
- Sea-level then falls resulting in the sea drying out and the Hartlepool anyhydrite forming. Still Zechstein cycle 1 (Z1).
- Sea-level then falls resulting in the sea drying out and the Hartlepool anyhydrite forming. Still Zechstein cycle 1 (Z1).
- The Roker Formation forms when sea-level then goes up again at the start of Zechstein cycle 2 (Z2). This deposits deeper water limestones and shallow reef limestones
- Z2 finishes when sea-level falls again to deposit the Fordon Evaporites.
- Z2 finishes when sea-level falls again to deposit the Fordon Evaporites.
The Permian stratigraphy along the coast is often disturbed by dissolution and collapse.
- This is because the evaporites/anyhydites dissolve slowly over time. As this happens open voids develop in between the limestone layers and eventually the rocks above collapse down into the voids.
- This disturbs the layer cake stratigraphy and produces collapse breccias which look like piles of rubble!
