Quaternary denudation of southern Fennoscandia – evidence from the marine realm

Abstract

Throughout the last 1.1 million years repeated glaciations have modified the southern Fennoscandian landscape and the neighbouring continental shelf into their present form. The glacigenic erosion products derived from the Fennoscandian landmasses were transported to the northern North Sea and the SE Nordic Seas continental margin. The prominent sub‐marine Norwegian Channel trough, along the south coast of Norway, was the main transport route for the erosion products between 1.1 and 0.0 Ma. Most of these erosion products were deposited in the North Sea Fan, which reaches a maximum thickness of 1500 m and has nearly 40 000 km3 of sediments. About 90% of the North Sea Fan sediments have been deposited during the last 500 000 years, in a time period when fast‐moving ice streams occupied the Norwegian Channel during each glacial stage. Back‐stripping the sediment volumes in the northern North Sea and SE Nordic Seas sink areas, including the North Sea Fan, to their assumed Fennoscandian source area gives an average vertical erosion of 164 m for the 1.1–0.0 Ma time period. The average 1.1–0.0 Ma erosion rate in the Fennoscandian source area is estimated to be 0.15 mm a−1. We suggest, however, that large variations in erosion rates have existed through time and that the most intense Fennoscandian landscape denudation occurred during the time period of repeated shelf edge ice advances, namely from Marine Isotope Stage 12 (c. 0.5 Ma) onwards.

Denudation of the continental shelf between Britain and France at the glacial–interglacial timescale

“…This may have been due to the distribution of cores, where a bias towards coarser grained sediments was incorporated into the selection of sites. However, on non-subsiding continental shelves, interglacials are periods of relative sedimentary quiescence when compared to glacial stages, thus having less persistence in the sedimentary record ( Hjelstuen et al, 2012 ). Further, there is a greater chance of reworking as successive erosion phases modify the morphological and sedimentary evidence of previous periods, and as a consequence the most recent phase of erosion and deposition is best preserved.…”

Meltwater sediment transport as the dominating process in mid-latitude trough mouth fan formation

“…Sediment transport related to GDFs may have been operating on the North Sea Fan for the last 1.1 Myr, i.e., since the first ice-stream evidence in the Norwegian Channel 33 . The North Sea Fan received terrigenous sediment from hinterland-to-deep-sea sediment-routing systems with a catchment of c. 215,000 km 2 , and comprises a sediment volume of c. 32,000 km 3 34 , 37 . Vertical erosion has been estimated to 164 m based on volume backstripping to the catchment 34 , and has been modelled from 200 to 600 m for the route of the Norwegian Channel Ice Stream 35 .…”

“…The North Sea Fan received terrigenous sediment from hinterland-to-deep-sea sediment-routing systems with a catchment of c. 215,000 km 2 , and comprises a sediment volume of c. 32,000 km 3 34 , 37 . Vertical erosion has been estimated to 164 m based on volume backstripping to the catchment 34 , and has been modelled from 200 to 600 m for the route of the Norwegian Channel Ice Stream 35 . With a total annual output of 1.1 Gt of sediment (equivalent to 8000 m 3 /yr per meter width of ice stream front), the Norwegian Channel Ice Stream was an extremely powerful sediment transport agent in the Late Quaternary 36 , 37 .…”

The last deglaciation of the Norwegian Channel – geomorphology, stratigraphy and radiocarbon dating

“…Nyg ard et al (2005) suggested that the NCIS advanced to the shelf edge during Marine Isotope Stages (MIS) 2, 6, 8, 10 and 12. Furthermore, it has been estimated that close to 50% of the sediments derived from the catchment area of the NCIS through the Quaternary were deposited in the North Sea Fan, located on the continental slope north of the channel (Hjelstuen et al 2012). As such, the Norwegian Channel is the product of multiple glaciations and not merely a Late Weichselian feature.…”