permian
Throughout the Permian there was the assemblage of the supercontinent of Pangea; where London was in a position approximately 10°N of the equator gradually drift northwards, and was typically part of a dry, hot climate, especially towards the end on the period. The Permian lasted from 290Mya to 251Mya, and ended with the largest mass extinction that is known to have occurred.
During the beginning of the Permian, the world was still under the influence of the glacial period that began in the Carboniferous and combined with the reduced plate tectonics (meaning that the spreading centre volume was not present) it resulted in global sea levels being the lowest known, possibly up to100m lower than today.
During the beginning of the Permian, the world was still under the influence of the glacial period that began in the Carboniferous and combined with the reduced plate tectonics (meaning that the spreading centre volume was not present) it resulted in global sea levels being the lowest known, possibly up to100m lower than today.
As Pangea assembled, it affected the climate of the whole world drastically. One big continent with two large mountain zones meant that saturated marine air masses couldn’t reach the inner land, and created a very arid climate with hot temperatures. In Britain the geology from the Permian is mainly from terrestrial sources, with rocks such as red Aeolian sandstones, breccia’s and conglomerates deposited, which outcrop in today in the Vale of Eden, East Ireland, Cheshire basins and to the east of the Pennines from Sunderland to Nottingham. Previously in the Carboniferous there was significant periods of mountain buildings, so the erosion of these mountains created the sediments of sand that were deposited in the lowlands and basins. This shows that even though the climate was arid and dry with Aeolian deposition dominating, there were also an abundance of flash floods and alluvial fans that deposited the conglomerates. The red staining in the terrestrial rocks comes from the oxidation in the atmosphere that is occuring in many deserts today, it has been likened that the climate was very like that of the Death Valley, USA today.
Towards the end of the Permian sea levels began to rise again due to the probably deglaciation in Gondwanaland’s South Pole. This caused low-lying areas to flood, which meant Northern Britain (along with parts of the North Sea, Germany and Demark) to become part of a tropical sea. This sea, known as the Zechstein Sea, has depositions of approximately 5 sedimentary cycles which would correlate to the relative changes in sea level as the continents adjusted to isostatic uplift and sea levels changes during the glaciations. Within these cycles were depositions of dolomite limestones, showing seas were rich with life as they contain fossils of stromatalites, bivalves and bryozoans. As the this cycle continued the Zechstein Sea evolved into a hyper-saline sea as evaporation dominated and sea levels relatively fell, depositing large volumes of evaporates (thickest layers up to 1000m), these deposits can be found in East Yorkshire and Durham. To get layers of evaporates so thick there must have been replenishment of sea water, which also accounts for the presence of potassium salts in the evaporates.
Towards the end of the Permian, climatic conditions became too extreme for many species of life to survive and 95% of all species dies out in the largest mass extinction known. It is very difficult to fully document the extense of this extinction by solely looking at the climate in Britian due to the poor record of fossils in the geology from the era, but it is thought the extinction occured more due to a combination of events that made it difficult for life to be as diverse. Such events thought to have contributed to the extinction is the occurence of the Large Igneous Province of the Siberian Traps, anoxia in the oceans and the supercontinent of Pangea affecting weather patterns, overall causing extremely climatic changes. This marked the end of the Palaeozoic Era.