Mesozoic geology of UK 1. Overview 2. Global tectonics 3. Sea level changes 4. Triassic geology 5. Jurassic geology 6. Cretaceous geology 7. Overview

1. Overview Mesozoic Cretaceous Jurassic Triassic 65 Ma 144 Ma 213 Ma 248 Ma Mass extinctions High sea levels Breakup of Pangaea

2. Global tectonics Cretaceous Jurassic Triassic Tethys Ocean Pangaea Tethys Ocean Tethys Ocean Central Atlantic North Atlantic North Sea rift North Sea rift Laurentia Gondwana Variscan mountains

3. Sea level changes Global sea level rise to +300m Local isostatic (tectonic) sea level falls North Sea North Atlantic Slow spread Fast spread Hot aesthenosphere Thermal dome Spreading ridge

4. Triassic geology Late Triassic Rhaetic ‘Tea Green Marls’ Middle Triassic Keuper Marl ‘Whiff of the Sea’ Early Triassic Bunter Sandstone Arid, terrestrial, coarse.

Late Jurassic Shelf seas cover UK. No coarse clastic supply High sea levels = high marine productivity = oil Middle Jurassic Thermal doming in North Sea. Deltas develop = oil reservoirs. Isostatic sea level fall Early Jurassic Liassic clay and lime Low clastic supply, tectonically quiet. 5. Jurassic geology

6. Cretaceous geology Late Cretaceous Chalk - highest sea level in Phanerozoic. No clastic input Phytoplankton blooms provide lime and silica Middle Cretaceous Greensand - major eustatic marine transgression North Sea and ‘Atlantic’ connect Early Cretaceous Wealden - thermal doming in Atlantic Isostatic fall in sea level Deltas and swamps in S. England

7. Overview A. Pangaea breaks up via Central and North Atlantic Tethys Ocean North Sea (failed rift) B. Eustatic sea level rise from fast rates of ridge spreading Isostatic sea level fall from thermal doming close to UK C. Clastic supply wanes, Calcareous sedimentation increases D. Begins and ends with mass extinction