ABSTRACT

Geological mapping in the Espanola-Willisville area reveals a Huronian succession as follows, in ascending order: Mississagi, Bruce, Espanola, Serpent, Gowganda, and Lorrain Formations, and banded chert-like siltstone. The bulk of the strata are arenaceous: medium- to fine-grained, submature, subarkose to arkose; some are calcareous (Espanola Formation). The Bruce and Gowganda Formations are essentially pebbly conglomeratic muddy sandstone in which the "matrix" generally is fine-grained subarkosic wacke, locally lithic. Paleocurrent study based on cross-bedding azimuths and dimensional fabric of phenoclasts suggests that the sediment transport for all the Huronian formations in this area was persistently from the north-northeast and north-northwest quadrant. However, variance values f r cross-bedding azimuths commonly show a well marked variation at different sampling levels, from 'exposure', 'sector' to 'formation'.

Most arenaceous rock types are coastal plain fluvial deposits probably laid down by a system of migrating, meandering rivers. The supermature quartzarenite of the upper part of Lorrain represents deposition in the turbulent shore zone. The Bruce, like the Gowganda Formation, may well be of glacial origin.