Nearshore Mesozoic basins off Nordland, Norway: Structure, age and sedimentary environment

Abstract

Seismic data acquisition along the Nordland coast (Norway) has resulted in the discovery of two downfaulted sedimentary basins of Mesozoic age in an area of Precambrian–Lower Palaeozoic metamorphic rocks. The Stabbfjorden Basin (informal name) west of Meløya has a sedimentary rock succession that is up to 800 m thick, while the Lyngværfjorden Basin (informal name) northeast of Træna is at least 350 m deep. Microfossil dating of ice-transported erratic blocks thought to be eroded from these basins and found on nearby skerries range in age from Barremian to Triassic. The majority of the samples are of Middle-Late Jurassic age. The sedimentary blocks comprise conglomerates, sandstones, siltstones and mudstones, and frequently contain shells and coal fragments. Lithofacies analyses show that they reflect shallow marine deposition, but it is possible that the oldest samples were deposited in a continental environment. The lithofacies reflect the well-known tectonic phases and sea-level changes that have been reported for the Middle Jurassic–Early Cretaceous in the Nordland offshore region. Vitrinite reflectance measurements show that organic material in the samples can be classified as immature, and the newly discovered basins have no hydrocarbon exploration potential.