Evaporite palynology: a case study of the Permian (Lopingian) Zechstein Sea

Abstract

Evaporites characterize the Lopingian of Europe but present obstacles for biostratigraphic analysis. Here we present a case study for processing the Lopingian Zechstein Group evaporites of central-western Europe for the recovery of palynomorph assemblages. We demonstrate that full recovery is easily achieved with two main modes of palynomorph preservation observed; palynomorphs are either exceptionally well-preserved and orange-brown in colour, or poorly-preserved, brown-black, opaque and fragmented. The latter are reminiscent of palynomorphs of high thermal maturity. However, we propose that the intact nature of preservation is a result of the rapid growth of near-surface halite crystals, with their darkening a consequence of locally-enhanced heat flux due to the relatively high thermal conductivity of salt. This case study has enabled novel insight into an otherwise undescribed environment, and demonstrates the utility and possibility of extracting palynomorphs from a variety of rock salt types. This method should be applicable to a wide range of ancient evaporite and could also be applied to other Permian evaporite systems, which are used as analogues for extra-terrestrial environments.

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“…The formation of marine evaporite minerals begins with the evaporation of seawater, which leaves behind concentrated solutions of various salts and minerals. As these solutions become increasingly concentrated, they eventually reach a saturation point, at which point the excess minerals begin to crystallize out of solution and form solid mineral deposits [15][16][17][18][19][20]. The rate and extent of evaporation, as well as the initial composition of seawater, are crucial factors determining the types and amounts of minerals that will precipitate out of solution.…”