Clay Fingerprinting to Evaluate Provenance: Case Study from a Marine Setting Offshore in the North Sea

Zeelmaekers, Edwin¹; Vandenberghe, Noël; and Srodon, Jan
¹[email protected]

Provenance studies based on the sediment mineralogy typically have suffered from a too low resolution of the applied mineral analysis methods to deliver conclusive results. This has changed with recent advances in quantitative (clay) mineral analysis, as demonstrated by the successful application of clay fingerprinting methods in unraveling the provenance of recent muddy sediments in the North Sea near the Belgian coast. The provenance of these deposits has significant economic importance as annually >10Mt needs to be dredged to maintain shipping lanes. Based on hydrodynamic models the leading hypotheses sourced them either from The English Channel or from erosion of Eocene deposits subcropping on the seafloor.

In the presented study a detailed mineralogical fingerprint of the bulk rock and clay mineralogy of the mud deposits was compared to those of the potential source areas (>300 samples). Systematic sampling of Suspended Particulate Matter (SPM) in The Channel and beach sediments from the English and French coasts; and the stratigraphic interval representing in the subcropping Eocene sediments clearly demonstrated that they can be excluded as major sources for the mud deposits based on clear differences in their qualitative and quantitative clay mineral composition. However, very similar mineral assemblages were found in the nearby Scheldt river system and its estuary: overbank sediments and SPM exhibited the same qualitative composition, but with higher proportions of smectite.

To better understand the relationship between the mud deposits and the Scheldt river system the provenance study was expanded from only examining present-day spatial relationships to also include the study of temporal variability of clay mineral assemblages in the Belgian coastal area throughout the Quaternary. For all of the interglacial deposits and the Weichselian cover sands it was found that their clay mineralogy was distinctly different from the mud deposits, except for sediments from the previous interglacial (Eemian) and Holocene salt marsh deposits. These results demonstrated that the same clay mineral assemblages have been present in the area since the creation of the Paleo-Scheldt river in the Elster ice age. Both the Paleo-Scheldt and the present-day Scheldt erode similar deposits, hereby explaining the similarity observed between the mud deposits and sediments currently transported in the river.

AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013