On the age of the Hungry Hollow Formation

Abstract

In the paper by J. Keith Rigby (1991) in the January issue of the Journal, the Hungry Hollow Formation of southwestern Ontario is correlated with the basal Ludlowvillian Centerfield Limestone of New York. The new species of heteractinid sponge described in the paper was thus considered to be older than the designated type species of his new genus Gondekia, which is from the middle Ludlowvillian Wanakah Shale. The correlation was referred to as that of Rickard (1984) and was consistent with others going back several decades. It was also included in subsequent correlations based on conodont biostratigraphy (Johnson et al., 1985; Sparling, 1985) that are otherwise largely at odds with Rickard's conclusions. However, Brett and Baird (1985) provided convincing evidence that the Centerfield is a regressive unit between shales representing deeper water sedimentation, whereas the Hungry Hollow appears to be the basal unit of a transgressive sequence of strata and thus unlikely to be of the same age. Evidence for this was supplied by Landing and Brett (1987), who described a previously unrecognized disconformity beneath the Hungry Hollow and noted its regional significance. They also reported finding a single specimen of the conodont Polygnathus timorensis in the Hungry Hollow. This is the guide fossil for the Lower varcus Subzone, to which the Centerfield has been assigned, so placement of both units in at least the same conodont subzone was justified at that time.