『Abstract
Stream-sediment and soil geochemical data from the Upper and
lower Coastal Plains of South Carolina (USA) were studied to determine
relationships between soils and stream sediments. From multi-element
associations, characteristic compositions were determined for
both media. Primary associations of elements reflect mineralogy,
including heavy minerals, carbonates and clays, and the effects
of groundwater. The effects of groundwater on element concentrations
are more evident in soils than stream sediments. A “winnowing
index” was created using ratios of Th to Al that revealed differing
erosional and depositional environments. Both soils and stream
sediments from the Upper and Lower Coastal Plains show derivation
from similar materials and subsequent similar multi-element relationships,
but have some distinct differences. In the Lower Coastal Plain,
soils have high values of elements concentrated in heavy minerals
(Ce, Y, Th) that grade into high values of elements concentrated
into finer-grain-size, lower-density materials, primarily comprised
of carbonates and feldspar minerals (Mg, Ca, Na, K, Al). These
gradational trends in mineralogy and geochemistry are inferred
to reflect reworking of materials during marine transgressions
and regressions. Upper Coastal Plain stream-sediment geochemistry
shows a higher winnowing index relative to soil geochemistry.
A comparison of the 4 media (Upper Coastal Plain soils and stream
sediments and Lower Coastal Plain soils and stream sediments)
shows that Upper Coastal Plain stream sediments have a higher
winnowing index and a higher concentration of elements contained
within heavy minerals, whereas Lower Coastal Plain stream sediments
show a strong correlation between elements typically contained
within clays. It is not possible to calculate a functional relationship
between stream sediment-soil compositions for all elements due
to the complex history of weathering, deposition, reworking and
re-deposition. However, depending on the spatial separation of
the stream-sediment and soil samples, some elements are more highly
correlated than others.』
1. Introduction
2. Geology of depositional environments of South Carolina
3. Mineralogy of the coastal plain
4. Geochemical surveys in South Carolina
5. Sampling and analytical methods
6. Multi-element statistical methods applied to stream sediments
and soils
6.1. Spatial variability of stream sediment-soil pairs
6.2. Stream sediment-soil pair distances
6.3. The index of winnowing
6.4. Principal component analysis of stream sediments and soils
of the UCP and LCP
6.5. Linear discriminant analysis of stream sediments and soils
of the UCP and LCP
6.6. Estimation of soil composition based on stream-sediment
composition
7. Summary and conclusions
Acknowledgements
References