Associated Physical and Biogenic Structures in Environmental Subdivision of a Cambrian Tidal Sand Body

Abstract

The Cambrian Chickies Quartzite was produced by a migrating mosaic of subtidal channels, intertidal flats and tidal flat ponds. These tidal zone subenvironments are interpreted from assemblages of physical and biogenic structures, each of which has unique hydrodynamic implications. The highest flow regimes and most persistent currents occur in channels represented by non-burrowed tangentially cross-stratified dune deposits. The range of flow conditions on the intertidal sand flat is represented by burrowed sandstones containing a sequence of physical structures from tangential to avalanche cross-stratification to lower flat bed. The high-energy low flat deposits contain closely spaced Scolithus burrow forms. Lower-energy high flat deposits contain Monocraterion burrow tops in conjunction with widely spaced Scolithus dwelling tubes. Quiet water ponds in abandoned channels on the intertidal flat are represented by lenses of non-burrowed gray clay immediately overlying channel deposits.