Fluvial environments - Environmental Sedimentology - page 82

Table 3.3 Fingerprinting techniques used in fluvial sediment provenance studies, and selected references.

Fingerprinting technique Method Reference

Radionuclides (e.g. 7 Be,
137 Cs, 210 Pb, 226 Ra)
Mineral magnetism

Measurement of concentration of radionuclide and
comparison with a background concentration
Mineral magnetic parameters (e.g. susceptibility,
frequency-dependent susceptibility, isothermal
remanence magnetization) measured, statistical analysis
Mineral abundances determined by X-ray diffraction
(XRD)
Heavy minerals separated, abundances determined by
point counting
Clay minerals separated; abundances determined by
XRD and analysis of results
Determination of geochemical composition and
statistical analysis (e.g. multivariate, principal
components analysis)
Macro- or microscopic determination of grain size,
statistical analysis

Peart & Walling 1986

Walling et al. 1979

Sediment mineralogy Woodward et al. 1992

Heavy mineralogy Singh et al. 2004

Clay mineralogy Wood 1978

Major and trace element
geochemistry

Lewin & Wolfenden 1978;
Passmore & Macklin 1994;
Collins et al. 1997
Knox 1987 Grain size and shape

during erosion and transport and which can,
on a statistical basis, effectively differentiate
between the various sources, are used for source
apportionment (Foster & Walling 1994). Once
suitable tracers are established, their values, or
'fingerprints' for potential source materials are
compared with the corresponding tracer values
for the 'unknown' sediment samples. It has been
increasingly recognized that no single diagnostic
tracer is capable of discriminating a range of
sources, so multiple tracer studies using several
fingerprints are now normally used (e.g. Walling
et al. 1993). Over the past several decades, a
wide range of physical and chemical fingerprint-
ing techniques have been developed and used
to great effect in determining the provenance of
fine-grained suspended and alluvial sediment.
The main techniques used are summarized in
Table 3.3.

are all controlled by climate, topography and
land-use. Areas with steep slopes, cold temper-
atures and high amounts of rainfall (such as the
Himalayan mountain range) have high sediment
supplies, whereas lowland areas with warmer
temperatures tend to have relatively lower sedi-
ments loads (which are dominated by clay-rich
materials) and higher dissolved element loads.
Sediment transport in rivers is mainly unidir-
ectional, following the dominant flow path, but
it can be influenced by turbulence and secondary
flows (Sear et al. 2000). The transport of indi-
vidual sediment particles occurs by entrainment,
transport and deposition (Hassan & Church
1992; Sear et al. 2000). A large number of fac-
tors influence sediment transport and deposition
in river systems. Among these are climate and
season (Boyden et al. 1979; Macklin 1996), site
geomorphology (Macklin 1996), streamflow
and suspended sediment concentrations (Yeats
& Bewers 1982; Kratzer 1999), water depth,
flow dynamics, bed surface structure and grain
size and texture (Eyre & McConchie 1993;
Macklin 1996). Anthropogenic disturbances,
such as channelization, damming and dredging
for navigation, also play a role in sediment
transport and deposition.
Although sediment can be mobilized and trans-
ported during normal flow conditions, floods

3.2.2 Controls on sediment supply, transport and
accumulation

The natural sediment load in rivers is supplied
by physical and biochemical weathering, which
are in turn controlled by (i) the geochemistry,
mineralogy and structure of the eroding rocks and
soils, (ii) precipitation, (iii) temperature and (iv)
vegetation cover (Bridge 2003). Ultimately, these