Re-evaluation of the Lower Meguma Supergroup as a Mixed Turbidite-Contourite System: Evidence from Detailed Studies on Liscomb Island, Nova Scotia

The Meguma terrane in eastern Canada is characterized by a thick Cambrian–Ordovician sedimentary succession that is subdivided into the Goldenville and Halifax groups. These units were interpreted to represent turbiditic basin floor and slope deposits, respectively. The Meguma terrane is interpreted to have originated as a lower Paleozoic continental margin on Gondwana, although its original position and underlying basement remain uncertain. Although strata of the Goldenville Group have traditionally been interpreted as largely turbiditic in origin, there are few detailed sedimentological studies, and many of the sedimentary structures present in these strata are not unique to turbidites. The facies observed in the Meguma terrane may also result through reworking and deposition by along-slope bottom currents. This study describes the sedimentology and stratigraphy of a 670 m-thick succession through the upper Goldenville Group in cm-scale detail to reconstruct the physical depositional processes and environments. Significantly, results suggest that strata on Liscomb Island record a turbidite-dominated deep-marine system in which episodic but sustained bottom current activity reworked and redistributed sediment. The scale, repetition, and internal complexity of cross-stratified units exceed what is typically expected from waning turbidity currents alone, and are therefore most consistent with episodic bottom current influence within a mixed depositional system. Reinterpretation of the sedimentary depositional environment has implications for other aspects of Meguma terrane geology.