Microfossils from Oolites and Pisolites of the Upper Proterozoic Eleonore Bay Group, Central East Greenland

Abstract

Silicified oolites and pisolites from Bed 18 of the Upper Proterozoic (about 700-800 Ma) Limestone-Dolomite "Series" of the Eleonore Bay Group, central East Greenland, contain a diverse suite of organically preserved microfossils that is, for the most part, unlike assemblages previously described from Proterozoic cherts and shales. Three principal assemblages occur in these rocks: 1) a clast-bound assemblage found in detrital carbonate grains (now silicified) that served as nuclei for ooid and pisoid growth, as well as in uncoated mud and mat clasts that were carried into the zone of ooid and pisoid deposition; 2) an epilithic and interstitial assemblage consisting of microorganisms that occured on top of and between grains; and 3) a euendolithic assemblage composed of microbes that actively bored into coated grains. The Upper Proterozoic euendolithic assemblage closely resembles a community of euendolithic cyanobacteria found today in shallow marine ooid sands of the Bahama Banks. Thirteen species are described, of which eight are new, five representing new genera: <i>Eohyella dichotoma</i> n. sp., <i>Eohyella endoatracta</i> n. sp., <i>Eohyella rectoclad</i> n. sp., <i>Thylacocausticus globorum</i> n. gen. and sp., <i>Cunicularius halleri</i> n. gen. and sp., <i>Graviglomus incrustus</i> n. gen. and sp., <i>Perulagranum obovatum</i> n. gen. and sp., and <i>Parenchymodiscus endolithicus</i> n. gen. and sp.