ISUASPHAERA ISUA (PFLUG) REVISITED

Abstract

Spherical objects, identified as microfossils and named Isuasphaera isua (Pflug), were reported in 1978 from a chert in the 3.7-3.8Ga Isua Greenstone Belt (IGB). Soon afterwards the biological nature of these objects was questioned on a number of grounds by several authors.Following renewed, recent claims for biogenicity, the locality has been revisited and the host-rock (metamorphosed chert) to the putative microfossils re-examined. Extreme stretching deformation of the metachert cannot possibly have preserved syn-depositional spherical objects. We conclude that the objects (whether biological or not) are entirely post-tectonic and probably result from pre-Quaternary weathering.