The spatial (nearshore–offshore) distribution of latest Permian phytoplankton from the Yangtze Block, South China

In order to analyze the spatial (paleoecological) distribution of the organic-walled microphytoplankton in the Late Permian, five sections from the Yangtze Block, South China, displaying different sediment facies types (from neritic to offshore paleoenvironments, including basinal facies) have been investigated palynologically. Based on the diversity and relative abundance of acritarch species and genera, the new data from the Permian provide similar patterns as those described from other geological periods: (1) low diversities with 2 to 4 acritarch species occur in nearshore environments, whereas the higher diversities (more than ten acritarch species) appear in the offshore environments; (2) at the generic level, the genera Leiosphaeridia, Reduviasporonites and Micrhystridium are distributed widely, from nearshore facies corresponding to shallow water environments to offshore facies corresponding to deeper water settings, whereas some genera, such as Dictyotidium and Veryhachium, have a narrower distribution, occurring on the continental shelf and towards the basin, indicating open marine environments; (3) the genus Schizosporis only occurs around the Permian–Triassic-Boundary (PTB), when the sea level declined, probably indicating nearshore environments with shallow water settings; (4) at the specific level, the species Micrhystridium breve, displaying short spines, and Leiosphaeridia minutissima are indicative of neritic facies, whereas the other species of Micrhystridium and Veryhachium with longer spines (e.g., Micrhystridium stellatum and Veryhachium hyalodermum) and Leiosphaeridia microgranifera indicate more open marine environments. Big spherical acritarch species (over 80 μm in diameter), such as Dictyotidium reticulatum, indicate shallow water environments; and (5) in the PTB strata, the relative abundance of the enigmatic Reduviasporonites, interpreted by some authors as a fungal spore, is not higher than 14% in every sample, indicating that a ‘spike’ of Reduviasporonites does not occur in the Yangtze area. Reduviasporonites chalastus (40 μm in length) obviously dominates in shelf environments of shallow water, whereas the smaller Reduviasporonites catenulatus (15 μm in length) are more common in deeper water.