The stratigraphy and sedimentology of the Fundy Group (Triassic) of the St. Martins area, New Brunswick

Abstract

Triassic sediments exposed along the south shore of New Brunswick, near St. Martins, were deposited primarily by a series of alluvial fans prograding eastward from the western margin of the Fundy half graben and are interbedded with fluvial conglomerates deposited by an axially flowing river system. The sediments are divisible into three formations, which are described here formally for the first time. These are, from base to top, the Honeycomb Point, Quaco, and Echo Cove formations. The basal Honeycomb Point Formation consists of approximately 990 m of red beds exposed in several fault blocks. The western outcrops consist of coarse breccias of the proximal fan, the Browns Beach Member, which fines eastward into sheetflood deposits of the mid- to distal fan, the McCumber Point Member. Both units contain eolian sands that indicate paleowind direction from the northeast. These are overlain by fluvial conglomerates of the Quaco Formation, 190–300 m thick, which were deposited by a large, braided river system that flowed north along the axis of the graben. Renewed growth of the alluvial fans led to the deposition of the Echo Cove Formation, 850–1300 m thick, on the conglomerates. The coarsest breccias are found in the westernmost exposures, the Stony Brook Member, and along the coast the formation is divided into the basal redbed unit, the Berry Beach Member, which grades into green beds of the Fownes Head Member, which in turn is overlain by the red beds of the Melvin Beach Member. Pollen recovered from the upper portion of the Fownes Head Member places the unit in the mid-Carnian (and possibly Ladinian).