A sedimentary provenance study of modern river sands from northern Fennoscandia and its insight into the source of Mesozoic successions deposited on the southwest Barents Shelf.

A series of sedimentary provenance techniques were applied to 20 modern sand samples collected from twelve major river catchments in northern Fennoscandia. This was carried out in order to evaluate the extent to which Mesozoic successions deposited on the southwest Barents Shelf were sourced from northern Fennoscandia.

One of the most distinctive provenance signatures in northern Fennoscandia occurs in samples from the Tana River, which crosses the Lapland Granulite Belt (LGB). Downstream of exposures of the LGB, modern sands are dominated by rutile with c. 1.9 Ga U-Pb ages and a chemistry indicating crystallization at c. 850 °C from a pelitic protolith. A detrital rutile signature similar to that in the Tana River is replicated in the Late Triassic – Early Jurassic Realgrunnen Subgroup deposited in the vicinity of the Nordkapp Basin, and indicates a common origin from the LGB. The Realgrunnen Subgroup deposited in the Hammerfest Basin has strikingly different provenance pattern. Here, rutiles have mostly c. 430-515 Ma ages and crystallised at c. 650 °C from a pelitic protolith. The similarity of this pattern to rutile data from the modern Målselva River indicates a source from Caledonian allochthons affected by Palaeozoic amphibolite-facies metamorphism.

Models depicting rejuvenation of a Fennoscandian sedimentary source region and Late Triassic drainage reorganisation are supported by these data. The rutile technique provides one of the clearest mechanisms for tracing the dispersal of Fennoscandian-derived sediment across the Barents Shelf.

Despite these contrasting rutile signatures, the Nordkapp Basin and Hammerfest Basin samples yielded remarkably similar zircon U-Pb age patterns. Their zircon age spectra are dominated by 1.0 Ga – 1.7 Ga grains. This age range does not correspond with widespread igneous or metamorphic events in northern Fennoscandia and so these zircons were probably recycled from sedimentary units.

A statistical assessment of the multi-proxy modern sand dataset, through INSCAL and Procrustes analysis, helps to identify the Barents Sea Group as a source of recycled detrital zircon and hence can account for the mismatch of zircon and rutile patterns in some of the Mesozoic offshore samples. It also shows how readily sedimentary reworking, uneven erosion and fertility can affect and bias the various sedimentary provenance signals.