KASSINELLA-CHRISTIANIA ASSOCIATIONS IN THE EARLY ASHGILL FOLIOMENA BRACHIOPOD FAUNA OF SOUTH CHINA

A new ecological unit within the well-documented late Ordovician brach iopod Foliomena fauna is defined on the basis of assemblages from Nort hern Guizhou and southern Sidhuan, Southwest China. The Kassinella-Chr istiania Association, from the lower Ashgill Linhsiang and Chientsaoko u formations, is dominated by the eponymous genera together with speci es of mainly Dedzetina, Sericoidea and Kozlowskites; Foliomena is rare or absent To date, the Foliomena fauna has been documented only from deep-water environments; however, the new association apparently occup ied shallower depths, probably in lowermost Benthic Assemblage Zone 3 and uppermost Benthic Assemblage Zone 4, presumably at the shallow end of the depth range of the Foliomena fauna. The incursion of the Folio mena fauna into relatively shallow-water environments may have been en couraged by abnormally low oxygen levels and sparse nutrients together with persistent soft substrates across this part of the Yangtze Platf orm during the early Ashgill.