Abstract The end-Triassic mass extinction (ETME) was one of the most severe biotic crises of the Phanerozoic, driven by environmental changes linked to Central Atlantic Magmatic Province volcanism. While the ETME is a well-studied event, its expression in organic-walled phytoplankton, particularly acritarchs, remains relatively unexplored. Palynological analysis of the Prees 2 borehole, NW England (West Midlands), spanning from the upper Rhaetian to the lower Sinemurian, reveals exceptionally diverse aquatic palynomorph assemblages. The aquatic palynological assemblages, in the context of ammonite, miospore and lithostratigraphic data, show how phytoplankton communities responded to stress and subsequent stabilization. In the upper Rhaetian, the dominance of xerophytic coniferous pollen reflects warm, semi-arid palaeoenvironmental conditions, while euryhaline palynomorphs are in a nearshore environment. Subsequent phases show increased terrestrial humidity as evidenced by the palynoflora, coinciding with reduced aquatic diversity in an assemblage adapted to low-oxygen conditions. The base of the Hettangian is marked by sustained Cheirolepidiaceae dominance and a transition from short-spined Micrhystridid occurrences (reflecting low-oxygen conditions) progressing to an increased aquatic morphological diversity phase. This latter phase includes alterations in acritarch assemblages and the proliferation of dinoflagellate cysts, indicating a shift from a proximal shallow-water to a shelf palaeoenvironmental setting. Our findings demonstrate that acritarchs are valuable indicators of palaeoenvironmental change, capturing transient ‘bloom’ phases linked to post-extinction instability and offering new insights into Early Jurassic palaeoecology and recovery following the ETME.
Rosin et al. (Thu,) studied this question.
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