Abstract

Acritarchs and Tasmanitids are described from three horizons in the Mian-wali Formation (Scythian) and two horizons in the Tredian Formation (Anisian) of the Salt and Surghar Ranges of West Pakistan. 35 species of acritarchs are recognized from the four lower horizons. Small acanthomorphs and polygonomorphs predominate: larger acanthomorphs and polygonomorphs, sphaeromorphs, netromorphs and herkomorphs are also present. Six new species are proposed: Micrhystridium balmei, M. gregarium, M. jekhowskyi, M. kummelii, M. teichertii and Veryhachium triqueter. Small Tasmanitids are present at one horizon in the Mianwali Formation and at a horizon otherwise barren of marine fossils in the Tredian Formation.

The stratigraphical and paleoecological significance of these assemblages is discussed. It is considered that the Permian and Triassic assemblages are sufficiently different to be distinguished by their acritarch content, but that ecological conditions (especially depth and water turbulence) have influenced the character of these assemblages too profoundly for them to serve as a suitable standard for international correlation.