Dating, correlation and stratigraphy of the Triassic sediments in the West Shetlands area

Abstract

Abstract Very thick sequences, up to 25 000 ft, of Permo-Triassic sediment are preserved within the Papa and East Solan Basins, in the West Shetlands area. The active margin of this Permo-Triassic basin lay along the West Shetland Spine Fault. Due to severe erosional truncation, the position of the westerly passive margin cannot be delineated. The Triassic basin fill, referred to the Papa Group, has been proven by drilling to be at least 8000 ft thick. A combination of palynological, log and sedimentological analyses have allowed the succession to be informally subdivided into lithostratigraphic units. The oldest, of earliest Triassic age, is the Otter Bank Shale Formation deposited in a coastal/alluvial plain setting. This is gradationally succeeded by the coarse-grained Otter Bank Sandstone Formation comprising sediments derived from the interdigitation of sheetflood, braidplain and aeolian environments of deposition. These represent the initial erosional products derived from the uplifted, rifted basin margin. This major phase of Early Triassic rifting is believed to have taken place during the Scythian. The succeeding Foula Sandstone Formation marks the establishment of predominantly axial braidplain systems, deposited during a period of intermittent but waning tectonic influence during Middle to Late Triassic times. The Papa Group is referred to the New Red Sandstone Supergroup.