Analysis of Sm-Nd isotopes on mudrocks yielded isotopic compositions in the range ?8.2 to ?2.3 (?Nd(1600 Ma)) in subsequence A2 and ?9.8 to ?5.0 (?Nd(1400 Ma)) in subsequence A3. An ?Nd versus time graph illustrates two distinct groupings that plot within known isotopic evolution fields of the Taltson-Thelon Tectonic Zone, and the Great Bear Magmatic Zone. Sediment provenance was strongly influenced by the Paleoproterozoic Forward Orogeny, but there are no significant changes in sedimentary provenance across the A2-A3 sequence boundary. Stable isotope analyses of C and O in the dolomitic East River Formation of subsequence A2 reveal a relatively monotonous signal with an average of ?0.5¡ë ¦Ä13C and ?8.76¡ë ¦Ä18O, which is consistent with global values of other late Paleoproterozoic carbonate successions. Enriched Mn values and depleted Sr values, however, suggest that the East River carbonate rocks experienced some degree of meteoric alteration; it is unknown how much this alteration affected stable isotope compositions.
Based on similarities in sedimentary provenance, age, and sequence stratigraphy, subsequence A2 of the Hornby Bay Group is correlated with the Wernecke Supergroup (Yukon). The latter is interpreted to represent the deep-water distal equivalent of the upper Hornby Bay Group in a westward-deepening basin. Deposition of subsequence A2 is recorded across North America and is mirrored by deep-water sedimentation along the eastern margin of the North Australian craton. The tectonic evolution of subsequence A2 in Laurentia is therefore remarkably similar to that of the North Australian craton up to ¡«1600 Ma, the age of the Forward Orogeny, and this has implications for interpretation of the latest stages of accretion of the supercontinent Nuna.