Provenance of Pliocene sediments and paleoenvironmental changes in the southern North Sea region using Samarium–Neodymium (Sm/Nd) provenance ages and clay mineralogy

Abstract

An 800-m-thick sedimentary succession from the Late Pliocene North Sea has been investigated on the provenance of the sediments and on changes of the source regions related to transport processes and climate changes. The lower Zanclean to Piacenzian part of the succession, from 1250 to 1050 m depth, and the middle Early Gelasian part, from 1100 to 700 m depth, belong to one distributory system with at least two contributing source areas. Provenance ages calculated on basis of Sm/Nd content indicate one old (Archean) and one young (<Proterozoic) source. Sediments with high provenance ages (up to 2 Ga) are fine-grained (clayey to silty), show high illite and kaolinite contents and are derived from the Scandinavian Shield in the northeast. This source acted during cold periods when glacier activity was high and the sediments were transport over a long distance towards the North Sea. Sediments with younger provenance ages (∼1.5 Ga) are coarser-grained (silty to fine sand), smectite-rich and are probably derived from more proximal volcanic areas of the southern continent. During these intervals, contribution of the Scandinavian source diminished by decreasing glacial erosion and the possibility of drainage towards the north into the Barents Sea. During warm intervals, sediments from the southern sources were delivered by enhanced river runoff due to higher precipitation. Fine-grained sediments from the Late Gelasian upper part of the succession, at 700 to 400 m depth, and Pliocene river deposits from the Netherlands onshore area belong partly to the same distributory system as the middle part (1100–700 m). Coarse-grained sediments from the upper part and some of the river deposits show evidence for different source area composition. The shift from warm Pliocene towards cold climate conditions and the intensification of glaciations is expressed by the increase of unweathered illite and a decrease of smectite and kaolinite content.