Changhsingian (Late Permian) calcareous algae and foraminifers from Shuicheng, western Guizhou, South China and their paleoenvironmental significance
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Abstract:
Three species in three genera of calcareous algae, including Gymnocodium bellerophontis, Permocalculus sp., and Tauridium kurdistanensis and ten species in eight genera of foraminifers, including two species in two genera of fusulinids, are identified from Well K576 near Shuicheng, western Guizhou, South China. The foraminifers mainly consist of Reichelina sp. indet., Nankinella sp., Pachyphloia schwageri, Pachyphloia sp., Geinitzina sp., Nestellorella sp. indet., Howchinella sp., Hemigordius aff. saranensis, Hemigordius sp., and Midiella sp. indet. The fossil fauna is divided into seven assemblages: Foraminifer-Calcareous alga-Ostracod, Foraminifer-Brachiopod-Ostracod, Ostracod-Bivalve-Gastropod, Foraminifer-Calcareous alga-Bivalve, Foraminifer-Brachiopod-Ostracod, Foraminifer-Calcareous alga-Bivalve, and Ostracod assemblages. Based on sequence stratigraphy of the study area, characteristics of the vertical sedimentary sequence, and analysis of log data, the palaoenvironment of the deposits that yield the Foraminifer-Calcareous alga-Ostracod assemblage (SQ3-3) and Foraminifer-Brachiopod-Ostracod assemblage (SQ3-4) is a delta front. The strata that yields the Ostracod-Bivalve-Gastropod assemblage (SQ4-1) was deposited on a tidal flat. The paleoenvironment of the Foraminifer-Calcareous alga-Bivalve (SQ4-2), the Foraminifer-Brachiopod-Ostracod (SQ4-3), and the Foraminifer-Calcareous alga-Bivalve (SQ4-3) assemblages is a lagoon. The strata that yields the Ostracoda assemblage (SQ4-3) was deposited on a sand flat. A low-energy, calm, and warm nearshore delta and barrier lagoon depositional systems were generally developed during the Changhsingian in Shuicheng area of western Guizhou. In addition, analysis of the fossil assemblages indicates that biodiversity increases significantly when both foraminifers and calcareous algae are present in the lagoon environment.
