A REEVALUATION OF OPHIOMORPHA BURROWS IN THE WEALDEN GROUP (LOWER CRETACEOUS) OF SOUTHERN ENGLAND

Attribution of burrows in the Wealden Group of southern England to Oph iomorpha is rejected. The burrows are essentially cylindrical, unlined and with a meniscate fill. Any outer knobbly appearance is due to dia genetic poikilotopic cementation or to differential weathering of a mu dchip-sand fill. The variable nature of meniscare fill reflects passag e of the producer through the thin-bedded, alternating sand-mud sedime nts or along sand-mud interfaces. The burrows are assigned to Beaconit es, though, since the identity of this ichnotaxon has been questioned, reference is also made to Taenidium. Two ichnoassociations are recogn ized: (1) a Beaconites antarcticus-Scoyenia (or Taenidium-Scoyenia) as sociation (Weald Clay) of a marginal lacustrine situation with fluvial input, and (2) a Beaconites barretti-Planolites (or Taenidium-Planoli tes) association of the fluvial (lacustrine delta) of the Lee Ness San dstone (Ashdown Formation). The Wealden burrows offer no inherent indi cations of palaeosalinity, and inferences made on supposed occurrences of Ophiomorpha in the Wealden Group must be reassessed. Other occurre nces of Ophiomorpha in non-marine facies are questioned. (C) 1995 Acad emic Press Limited.