• During the Late Silurian and Early Devonian, the Royal Creek area lay at the margin of a deep-water embayment. The transition from shallow to deep water was relatively abrupt, with very thick shallow-water (including intertidal and shallow subtidal), sparsely fossiliferous carbonates accumulating on the large platform immediately to the east, southeast, and south of the study area, and deep-water, graptolite-rich shales and calcareous shales of the Road River Group accumulating in a northwest-facing trough that joined to the Blackstone River and Richardson troughs (Lenz, 1972 ; Norford, 1997 ). In the transitional zone, perhaps no more than one kilometer in width, brachiopods flourished, and trilobites, bryozoans, corals and gastropods were relatively common (Lenz, 1977a, 1977b, 1982 ). Sea-level fluctuations through this time period are evidenced in the area by tongues of the deeper water facies trangressing over the shallower-water carbonates, alternating with tongues of the latter facies prograding over deeper water facies. During times of shallow-water deposits prograding over deeper water facies, coupled with a relatively steep slope margin (still visible in a few localities), benthic organisms found themselves in a very unstable environment and, perhaps triggered by earth tremors, cascaded into deeper waters. As a result, the most richly fossiliferous carbonates are predominantly debris-flow deposits, in which shallower and deeper dwelling benthic faunas within any debris-flow bed are entirely intermixed. (From Blodgett, Frýda & Lenz 2001.)