Fig. 5: Regional and local context of our material.

a Lower Cambrian exposures (black) on the Avalon Peninsula, Newfoundland; data from Hutchinson¹¹, Landing and Benus¹³, Landing et al.¹⁵ and King¹⁸. Locality Bacon Cove marked by a star. b Lower Cambrian section at Bacon Cove; ∂¹³C data from King¹⁸. The positive ∂¹³C excursion⁸³ c. 7.0 m above the level with the here described specimens marks the Cambrian Arthropod Radiation Excursion (CARE) in the Smith Point Formation. The level of the oldest occurrence of trilobites on the peninsula lies above an intra-Smith Point Formation s.str.¹¹ unconformity, which is the base of the Brigus Formation s.str.^13,14. This unconformity marks the end of the CARE. It corresponds to the boundary between the Camenella baltica (sub-trilobitic) and Callavia broeggeri zones and is thus a significant biostratigraphic marker^13,14,84. The Bonavista Formation s.str.¹¹, as also the entire Bonavista Group s.str.^13,14, corresponds to the sub-trilobitic lower Cambrian, whereas the overlying Brigus Formation s.str.^13,14 represents the first trilobite-bearing lower Cambrian unit in Newfoundland^13,14,85,86. PDB Pee Dee Belemnite, Fm Formation.