Morphology, Mineralogy, and Hydrology of Soils in the Triassic Culpeper Basin of Maryland
Morphology, Mineralogy, and Hydrology of Soils in the Triassic Culpeper Basin of Maryland
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Date
1992
Authors
Elless, Mark Peter
Advisor
Rabenhorst, Martin C.
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Abstract
Soils derived from red parent materials are problematic
in terms of morphologically assessing their hydrology
because these parent materials are known to retard the
development of redoximorphic features within their sola.
This retardation phenomena may lead to misinterpretations of
these soils for both agricultural and engineering purposes.
Such soils occur within the Triassic Culpeper Basin of
Maryland. Eleven pedons along two topohydrosequences within
this basin were therefore investigated to determine the
interrelationships between the soil morphology, mineralogy,
and hydrology, particularly as these pertain to the
development of redoximorphic features in these soils. These
soils are derived from dusky red (SYR 4/4) parent materials
which retard the development of redoximorphic features.
Morphological descriptions of each pedon were made and the
water table was monitored in both open boreholes and slotted
PVC pipes at staggered depths. Bulk samples of each horizon
were collected for mineralogical and chemical analyses.
Results indicate that hematite is the only iron oxide in the
underlying red shales and sandstones of this basin. The
hematite in the soils is then inherited during pedogenesis
and is responsible for the red hues exhibited throughout the
profiles of the better-drained pedons and in the lower sola
of the more poorly-drained pedons. Results of parent
material uniformity indicate the presence of either loess,
colluvium, alluvium, or mixtures of these materials with
residuum within the upper sola of these same pedons.
Residual, or principally residually-derived, soils remain
predominantly red throughout their profile, independent of
hydrology. Soils formed from non-uniform parent materials
exhibit yellower hues, particularly within their upper sola.
Thus, the pedogenic yellowing of these pedons may be due to
either the incorporation of more easily altered foreign
material than that derived from weathering of the red
residual parent materials or to the presence of a
seasonally-high water table in the upper sola of these
pedons. Even though redoximorphic features are created
through redox processes, the nature of the parent materials
appears to mediate their degree of development. This study
suggests that the degree of parent material uniformity be
assessed prior to any judgment on the drainage classes of
similar soils.