The source of the marine waters of the Zechstein Sea.
The late Permian East Irish Sea Basin equivalent of the Zechstein Sea is called the Bakevillia Sea because the biota found there originated from the Boreal Sea to the north of Pangea. Likewise Peryt et al. (2012) in their analysis of the biota for the Werra Cycle of the Southern Permian Basin of Europe established that the original Zechstein Sea basin flood was with cold Boreal seawater and that the Zechstein Sea was originally temperate to cool.
Why the temperate/cool waters of the initial Zechstein Limestone basin in its central locations became warm, remains enigmatic (Peryt et al., 2012).
Can anyone provide me with field evidence that the second Zechstein Sea cycle biota was Tethys Ocean in origin derived from warm waters flooding in from the east?
Hypothesis: Is it possible for a dual source origin of the Zechstein Sea marine waters? Cold low-salinity low-density Boreal Sea water derived from the north stratified above warm high-salinity high-density Tethyian water derived from the east?
Peryt, T.M., Raczyński, P., Peryt, D. and Chłódek, K., 2012. Upper Permian reef complex in the basinal facies of the Zechstein Limestone (Ca1), western Poland. Geological Journal, 47(5), pp.537-552
Dear Phillip, a good question.
I cannot answer it, but I may be able to shed some light on it.
I studied, but never published, my fieldwork in Manchester UK on the Manchester Marls exposed in huge strike temporary exposures on the Eccles-Salford cutting section of the M602 motorway. The strike section was in the thick uppermost Manchester Marls which are dull red monotenous marls (mudstones) devoid of shelly fauna. Instead, careful examination showed them to be playa lake deposits with numerous subaerial emergent surfaces proved by dessication cracks. Of interest was that 20 to 100% of the volume of the desiccated surfaces was bioturbated, but not by truly aquatic invertebrates but by semi-terrestrial to terrestrial invertebrates that had tunnelled and backfilled their chaotic burrows by tiny mudtone chips, with no sign of water deformation. In addition, in spite of days of searching no evidence of pseudomorphs of rock salt were found, indicating that the rock unit was non-marine and freshwater very low salinity. The informal MS name for the unit is the Eccles Mudstone and it was found to extend on top of the normal marine Zechstein Manchester Marls between Stockport and Warrington in temporary exposures and boreholes. On one occasion an large diameter cored water borehole in the Eccles Mudstone contained reptile footprints. I conclude that this was a freshwater lake in a depression vacated by the Zechstein marine incursion and clearly non-saline.
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