Calcite spheres and ellipsoids, up to 0.4 mm in diameter, occur abundantly in Pliocene and possible Upper Miocene shelf sediments in the Dome Gulf et al. Ukalerk C-50 well, drilled in the Beaufort Sea. Similar structures were recovered from coeval strata in the Imperial IOE et al. Isserk E-27 well and from slightly younger strata in the Dome Hunt Nektoralik K-59 and Hunt Dome Kopanoar M-13 wells. They consist of fibrous and platy calcite enclosing grains of barite, quartz, feldspar, clay minerals, and, very rarely, ferro-manganese minerals. The quartz, feldspar, and clay minerals are predominantly detrital with some authigenic overgrowths on the quartz and feldspar. The spheres and ellipsoids are interpreted to have formed during early diagenesis as micronodules, probably at, or near to, the sediment–water interface. However, a faecal pelletoidal origin cannot be totally ruled out.