Sedimentary architecture of siliciclastic, syntectonic graben and halfgraben fill in Kvalpynten, Edgeøya, Svalbard

An array of ten grabens/ half-grabens and their associated syntectonic basin fill (averaging approx. 700 m across) are exposed along a 9 km cliff section at Kvalpynten, Edgeøya, offering a unique opportunity to study the silisiclastic architecture of listric graben basin fill. The exposures at Kvalpynten provide a unique opportunity to correlate fault-controlled sedimentary architecture on the scale of meters to hundreds of meters with detailed facies relationships, and thus fault-induced differential accommodation with the depositional environments that filled it. The basins developed in the Late Triassic, during the deposition of the Early Carnian to Early Norian deltaic successions of Tchermakfjellet and De Geerdalen formations which is approximately the onshore equivalent to the offshore Snadd Formation. The lowermost part of the ca 400 m high Kvalpynten cliff section reveals a number of NW–SE striking growth faults with 50–100 m offset, which bound basins filled with shale and sandstone wedges. Up section, the growth faults tip out, and are buried by undeformed deltaic deposits. Integrated field studies including sedimentology and structural geology combined with surfaces mapping on a photogrammetric virtual outcrop model allowed incremental reconstruction of the grabens/ half-grabens evolution. Four transgressive surfaces were identified and mapped, allowing correlation of the sandstone packages between each basin. The sequence of faulting has been defined with respect to the mapped flooding surfaces. Faulting clearly occurred in several phases as evident by the syn-kinematic fault’s control on sediments of different ages, and from the occurrence of later forming faults rotating earlier formed fault blocks. In general, early faults defined a relatively symmetrical basin configuration whereas later phases of movement were localized mainly along south-dipping faults. This gave rise to a change to more asymmetric basins and to the formation of asymmetric, composite sedimentary bodies with stacked shoreface and offshore transition deposits. Locally, fault crests were eroded. Our sedimentological observations suggest that tidal processes were dominant during sandstone deposition within the grabens/half-grabens, expressed by the widespread occurrence of tidal bar and tidal flat deposits.