An Overview and Review

Netherlands Journal of Geosciences — Geologie en Mijnbouw |95 – 1 | 23–107 | 2016 doi:10.1017/njg.2015.32 Review The mineralogy of suspended matter, fresh and Cenozoic sediments in the fluvio-deltaic Rhine–Meuse–Scheldt–Ems area, the Netherlands: An overview and review J. Griffioen1,∗,G.Klaver2 &W.E.Westerhoff3 1 TNO Geological Survey of the Netherlands, P.O. Box 80 015, 3508 TA Utrecht, the Netherlands and Copernicus Institute of Sustainable Development, Utrecht University, P.O. Box 80 115, 3508 TC Utrecht, the Netherlands 2 Formerly BRGM, Laboratories Division, 3 av. C. Guillemin, BP36009, 45060 Orleans, France; Le Studium, CNRS, Orleans, France; TNO Geological Survey of the Netherlands, P.O. Box 80 015, 3508 TA Utrecht, the Netherlands 3 TNO Geological Survey of the Netherlands, P.O. Box 80 015, 3508 TA Utrecht, the Netherlands ∗ Corresponding author. Email: jasper.griffi[email protected] Manuscript received: 18 March 2015, accepted: 13 October 2015 Abstract Minerals are the building blocks of clastic sediments and play an important role with respect to the physico-chemical properties of the sediment and the lithostratigraphy of sediments. This paper aims to provide an overview of the mineralogy (including solid organic matter) of sediments as well as suspended matter as found in the Netherlands (and some parts of Belgium). The work is based on a review of the scientific literature published over more than 100 years. Cenozoic sediments are addressed together with suspended matter and recent sediments of the surface water systems because they form a geoscientific continuum from material subject to transport via recently settled to aged material. Most attention is paid to heavy minerals, clay minerals, feldspars, Ca carbonates, reactive Fe minerals (oxides, siderite, sulphides, glauconite) and solid organic matter because they represent the dominant minerals and their properties form a main issue in subsurface and water management. When possible and relevant, the amounts, provenance, relationship with grain size distribution, early diagenesis and palaeohydrological evolution are described. Tables with statistical data about the mineral contents and isotopic composition of carbonates and organic matter are presented as overviews. The review on the mineralogy of Dutch fluvial and marine environments is more extensive than that for the other sedimentary environments because the first two have been studied much more intensively than the others and they also form the larger part of the Dutch deposits. The focus is on the natural background mineralogy of Dutch sediments, but this is hard for recent sediments, largely because the massive hydraulic infrastructure present in the Netherlands has probably also affected the mineralogy and geochemistry of sediments deposited in recent centuries. Many findings are summarised, several of which lead to more general insights for the Dutch situation. Ca carbonates in sediments often have several provenances and thus must be considered as mixtures. Dolomite is commonly present in addition to calcite. The importance of biotite as weatherable mica is unclear. Weathering of heavy minerals plays some role but it is unclear in which way it affects the heavy mineral associations. Clays are usually dominated by illite, smectite and their interstratified variant, while kaolinite is usually below 20% and chlorite below 5%. Vermiculite is a minor constituent in fluvial clays and its illitisation presumably happens during early diagenesis in the marine environment. Opaque Fe hydroxides can be present in addition to Fe oxyhydroxide coatings and both will play a role in redox chemistry as reactive Fe minerals. Feldspars in marine sediments must be present but they have not been properly studied. The genesis of rattle stones and carbonate concretions has not been completely elucidated. The fraction of terrigeneous organic matter in estuarine and coastal marine sediments is substantial. The available data and information are spread irregularly over the country and the reviewed information discussed in this paper is derived from relatively small-scale studies dealing with a limited amount of analysed samples. Much information is available from the Scheldt estuaries in the southwestern part of the Netherlands partly due to the severe contamination of the Western Scheldt in recent decades. C Netherlands Journal of Geosciences Foundation 2016 23 Downloaded from https://www.cambridge.org/core. IP address: 170.106.40.219, on 02 Oct 2021 at 07:13:36, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/njg.2015.32 Netherlands Journal of Geosciences — Geologie en Mijnbouw 1 Introduction From the foregoing it is clear that insight into the mineralogical composition of sediments is of general relevance. Mineral grains are the building blocks of clastic sediments. The This being the case, it is surprising that there has been no mixture of minerals together with organic matter influences the overview of the mineralogical composition of sediments in the pore water composition, the soil’s pedological evolution and fer- Netherlands. A wealth of information is available on the geol- tility, the fate of pollutants in the subsurface, the porosity and ogy of the Netherlands, and several books present geological permeability as geohydrological properties and the geomechan- overviews of the country (De Mulder et al., 2003; Wong et al., ical strength of the subsurface. More specifically, mineralogi- 2007 are the most recent and extensive ones). However, these cal composition plays an important role in sediment reactivity kinds of texts address the mineralogy in a qualitative and re- (Van Gaans et al., 2011), greatly influencing surface complex- stricted way, focusing on distinguishing and grouping heavy ation and ion exchange of cations and anions, sorption of or- minerals for stratigraphical reasons. This paper therefore aims ganic substances, denitrification and other redox reactions, as to provide an overview of the mineralogy and organic geochem- well as the weathering processes. Insight into this reactivity is istry of sediments as well as suspended matter as found in the needed for environmental management issues such as drainage- Netherlands (and some parts of Belgium), based on an exten- induced oxidation, aquifer storage and recovery, natural at- sive review of the scientific literature of more than a century. tenuation of pollutants, leaching of nutrients from farmland, We address suspended matter, recent sediments of the surface reactive transport and secondary mobilisation of trace metals, water systems and Cenozoic sediments because they form a and transfer of pollutants or nutrients from aquatic sediments geoscientific continuum: recent marine and fluvial sediments to the water column or vice versa. Additionally, the reactivity as well as suspended matter are the present-day analogues of of sediment influences the pH and redox state of the sub- the geological sediments. Most attention is paid to the follow- surface and hence the stability of the subsurface, man-made ing groups of minerals, with an indication of their relevance: constructions and buried materials (examples being the corro- heavy minerals as indicators of provenance etc., clay miner- sion of steel constructions and the stability of archaeological als for their contribution to the sorption capacity and impact heritage). on geohydrological and geomechanical properties, feldspars as The mineralogy of sediments is also used to stratigraphi- major, weatherable Al silicates, Ca carbonates as reactive, pH- cally classify sediments and to characterise their provenance. buffering minerals, reactive Fe minerals (oxides, carbonates, Heavy minerals (i.e. having a specific density exceeding 2.85 sulphides, glauconite) for their overall reactive behaviour, and kg/dm3; Boggs, 2009) are traditionally used for this purpose, solid organic matter for its redox-controlling and sorptive ca- but this is labour-intensive and is nowadays rarely applied in pacities. The review has been limited to the Cenozoic sediments the Netherlands. The clay mineralogy may also be used as a because there is little literature on older sediments for which palaeogeographical tool to characterise past climatological con- integration is less needed (an exception being the Rotliegend ditions and the provenance of sediments (Tebbens et al., 1998; Sandstone, which is the most important natural gas reservoir Thiry, 2000; Zeelmaekers, 2011). The nature of quartz, mica and rock in the Netherlands and has therefore been intensively feldspar grains also assists in the visual recognition of different studied; Gaupp & Okkerman, 2011). The sediments are predom- kinds of sediments: the presence or absence of multicoloured inantly clastic; organic or chemical sediments play a minor role quartz and of mica are important criteria when visually clas- in the Cenozoic records of the Netherlands. sifying Dutch fluvial and other sediments stratigraphically (De Fig. 1 presents a map of the Netherlands with all geographi- Mulder et al., 2003). Other criteria often used are the presence cal names used in this paper. Section 2 presents a brief overview of glauconite, shells or, more generally, Ca carbonate (using of the geology and geography of the Netherlands. The review the effervescence test). method is described in section 3, together with several method- More abstractly, sediments and suspended matter are ological analytical approaches that have been applied by re-

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