Carbonate-Sulfate Intertidalites of the Windsor Group (Middle Carboniferous) Maritime Provinces, Canada

Abstract

During the Carboniferous, very thick postorogenic, mainly continental, red beds derived from intrabasinal horsts, accumulated in a complex rift-valley system called the Fundy Basin. During the Middle Carboniferous, generally hypersaline seas flooded perhaps a dozen times into the tortuously interconnected, intrabasinal grabens. Laterally, the resultant marine carbonates grade through nodular sulfate into increasingly coarser red beds, as well as lavas at basin margins. Red beds constitute approximately 80 percent of the Middle Carboniferous Windsor Group. Vertically, each carbonate blanket shows mainly offlap successions from shallow water through intertidal to supratidal environments. During the Late Carboniferous Maritime Disturbance, the assemblage was severely folded, faulted, locally metamorphosed, and intruded. Red beds flowed plastically or were metamorphosed locally to slate; carbonate units were folded and faulted; sulfates show spectacular metamorphic fabrics when not protected by adjacent carbonates.