MULTIPLE ORDERS OF RELATIVE SEA-LEVEL CHANGE IN AN EARLIEST CAMBRIAN PASSIVE-MARGIN SUCCESSION, MACKENZIE MOUNTAINS, NORTHWESTERN CANADA

Earliest Cambrian siliciclastic strata in the Mackenzie Mountains (Ing ta, Backbone Ranges, and Vampire Formations) contain deposits of a var iety of shelf, nearshore, and fluvio-deltaic depositional environments , The strata contain a hierarchical succession of sequence-stratigraph ic units. Parasequences, simple depositional sequences (at least eight een), composite sequences (three), and supersequences (one complete an d part of another) have all been recognized within the succession, The se units appear to record the interactions between at least five order s of relative sea level cyclicity and formed on time frames that were broadly consistent with possible eustatic origin, Type-two sequence bo undaries (generally considered rare in siliciclastic settings) appear to be common in this succession, and it is suggested that location on the paleoshelf, as well as sea-level variation, can influence the char acter and interpretation of sequence-stratigraphic units, especially i n isolated successions, while the units most easily recognized and cor related (simple and composite sequences) are the result of third and f ourth-order sea-level cycles, second-order fluctuations seem to have e xerted a significant control on sequence characteristics, The general proximality/distality of the succession is apparently controlled in la rge part by second order oscillations, and the nature and expression o f the sequence boundaries that demarcate the simple sequences are also influenced by sea-level variations of second order, In a similar fash ion, second and third-order sea-level interactions can influence syste ms-tract development within simple sequences and may determine the pre sence or absence of a TST within the simple sequences.