Gregory S. Springer

Cave sedimentation, genesis, and erosional history in the Cheat River Canyon, West Virginia

A model of cave sedimentation and genesis is used to gain greater resolution and accuracy in the calculation of an incision rate for Cheat River, West Virginia. Maze caves along the river and their primary sediments were created and deposited beneath base level. Single conduit caves are largely unrelated to base level and their sediments are derived from overlying strata. A magnetostratigraphic record is reported for cave sediments within the canyon. The magnetostratigraphy of each sample is plotted versus elevation relative to base level and depositional environment (vadose or phreatic). The resulting chart accurately depicts the range of error associated with using cave sediments as indicators of previous base-level positions. This technique can be applied within any future studies using cave sediments for deriving incision rates of rivers. The calculated incision rate of Cheat River within the study area is between 56.0 and 63.2 mm/k.y.

River-derived slackwater sediments in caves along Cheat River, West Virginia

Abstract The November 1985 Cheat River flood produced overbank, slackwater deposits in caves of the Cheat River canyon. The deposits include loamy silt, loamy sand to very fine sand, and flotsam. Sediments deposited by the November 1985 flood lie within 1 m of the established high water mark and are good indicators of peak stage. Prehistoric overbank, slackwater deposits are present in one cave. These sediments are inferred to be ≥400,000 years old and are, therefore, unrelated to the modern Cheat River. Overbank slackwater deposits are poorly preserved in the examined caves, because cave streams actively remove sediments and the warm, moist environment of the caves fosters decay of woody flotsam. Deposits of the 1985 flood are projected to survive at most a few centuries. In contrast, slackwater sediments inferred to be ≥400,000 years old are preserved within a cave shielded from significant runoff and biogenic activity.

Empirical and theoretical investigations of sculpted forms in Buckeye Creek Cave, West Virginia

Sculpted forms play important roles in channel erosion, but the controls on their growth or appearance are uncertain. Empirical evidence from sculpted forms eroded into limestones within Buckeye Creek Cave, West Virginia, shows that types of sculpture morphology are determined by the types of flow or vortex structures present within sculptures during floods. Small hemispherical sculptures maintain constant form as they enlarge and occupy fixed locations on channel walls because of their association with joints, styolites, and bedding planes. Taking advantage of the systematic growth and stability of the sculptures, a geometrical model of sculpture growth is presented that relates the effects of sculpture size, form, and wall retreat to the relative erosion efficiencies and excesses required for sculpture growth. Numerical results obtained from the theoretical model reveal that small sculptures must erode more efficiently than large sculptures or they will be removed by wall retreat and that erosion rates must increase exponentially with increasing concavity. Relative to channel erosion, small sculptures must possess very high interior erosion rates where nearby surfaces are rapidly eroding. Therefore, small sculptures are unlikely to form or persist on rapidly eroding surfaces, and the rate of incision is an important control on the evolution of sculpted forms.

Sediment budgets for two mountainous basins affected by a catastrophic storm: Blue Ridge Mountains, Virginia

On June 27th, 1995, a catastrophic storm generated thousands of slope failures in mountainous portions of Madison County, VA, USA. Within a 129-km2 area, 16-h rainfall totals reached 775 mm. Using direct field measurements, sediment budgets were constructed for two drainage basins impacted by the event, Teal and Jenkins Hollows. Lengthwise distributions of channel erosion and deposition were examined by taking measurements within incremental 30-m-long channel segments. Comparison of sediment budgets reveals that the two hollows responded very differently to the storm event. These differences are largely due to differences in soil types, failure volumes, and natures of the resulting flows. Within Jenkins Hollow, the kinetic energy of a 4200-m3, liquefied slope failure scoured the channel of virtually all sediment and vegetation and resulted in a sediment retention rate of 5%. In contrast, slope failures that reached the central channel of Teal Hollow failed to generate a large flow track and erosion features are coupled with deposition features. The sediment retention rate in Teal Hollow was 27%. Single storm denudation rates for the basins exceed the regional 1 ka area-normalized denudation rate of 25.5 mm ka−1; denudation was 27 mm in Teal Hollow and >38 mm in Jenkins Hollow. Following catastrophic events, considerable attention has been paid to those channels dramatically modified by debris flows. The high denudation rate for Teal Hollow, attributed to liquefaction of fine-grained soils easily transported as washload, suggests that extremely high denudation rates are possible even in low-order mountainous basins that appear relatively undisturbed by catastrophic storms.

Testing for reach-scale adjustments of hydraulic variables to soluble and insoluble strata: Buckeye Creek and Greenbrier River, West Virginia

Abstract An open question exists as to whether channel geometries and hydraulics are adjusted in bedrock streams with stable, concave profiles in a manner analogous to alluvial rivers. As a test of this problem, a comparison was undertaken of channel geometries and hydraulics among reaches with substrates that are of high mechanical resistance, but of variable chemical resistance. Reaches were selected from Buckeye Creek and Greenbrier River, West Virginia, USA because these streams flow over sandstones, limestones, and shales. The limestones have Selby rock resistance scores similar to those of the sandstones. A total of 13 reaches consisting of between 6 and 26 cross sections were surveyed in the streams. HEC-RAS was used to estimate unit stream power ( ω ) and shear stress ( τ ) for each reach. The reaches were selected to evaluate the null hypothesis that that ω and τ are equal atop soluble versus insoluble bedrock. Hypothesis tests consisted of paired t -tests and simultaneous, multiple comparisons. Geomorphic setting was included for Greenbrier River because previous studies have suggested that bedrock streams are intimately coupled with hillslopes. Holding geomorphic setting constant, three separate comparisons of ω and τ reveal that these variables are lowest atop soluble substrates in Greenbrier River (significance ≤0.05) and that changes in ω and τ are mediated by changes in channel geometry. Similarly, headwater reaches of Buckeye Creek developed atop shale and sandstone boulders are statistically distinguishable from downstream reaches wherein corrosion of limestone is the primary means of incision. However, comparisons in each stream reveal that channel geometries, ω and τ , are not strictly controlled by bed solubility. For constant substrate solubility along the Greenbrier River, ω and τ are consistently higher where a bedrock cutbank is present or coarse, insoluble sediment enters the channel. The latter is also associated with locally high values of ω and τ in Buckeye Creek. Assuming that incision by corrosion requires lower values of ω and τ because the channel need not be adjusted for block detachment and tool acceleration, we posit that the statistically lower values of ω and τ are tentative evidence in favor of differential geometric and hydraulic adjustments to substrate resistance. We observe that these adjustments are not made independent of geomorphic setting.

Multiproxy evidence from caves of Native Americans altering the overlying landscape during the late Holocene of east-central North America

We compare environmental changes recorded in stalagmites and alluvium from the mountainous Buckeye Creek basin of West Virginia, USA to a nearby, independent archaeological record of Native American presences in the forested watershed. A climatic record constructed from stable isotopic (δ18O calc and δ13Ccalc) and trace metal (Sr/Ca) ratios in stalagmitic calcite is consistent with regional palynology during much of the Holocene. The stalagmite δ13Ccalc and Sr/Ca values track aridity associated with North Atlantic Ocean (NAO) ice-rafting events during solar minima. However, the δ13Ccalc record diverges sharply from the Sr/Ca record at ~2100 (calendar) years BP, which maintains the same relationship with ice rafting in the NAO. A dramatic and sustained enrichment in δ13Ccalc values (>1‰) without a corresponding shift in Sr/Ca values, suggests a systemic change in above-cave vegetation and soil carbon. This hypothesis is corroborated by a record of the stable isotopic composition of bulk organic carbon (δ 13Corg) in alluvial silts. Cultural artefacts record Native American presences in the watershed during the late Holocene and archaeologists place peak Native American presence as having occurred between 750 and 550 years BP, nearly contemporaneous with peaks in δ13Ccalc , δ13Corg, and relative charcoal abundances documented herein. Notably, values of the three environmental proxies decrease after Native Americans abandoned the watershed. The available evidence is consistent with Native Americans having made significant changes to the area’s ecosystem and soils prior to the arrival of Euro-colonial peoples at ~225 years BP. Our findings highlight the active roles native peoples had in shaping the North American “wilderness” described prior to its destruction by early European settlers.

Long-term changes in precipitation recorded by magnetic minerals in speleothems

Speleothems are important paleoclimate archives. Researchers typically compile measurements of stable isotopic ratios dated using high precision U-Th radiometric techniques to reconstruct regional and global climate. Magnetic material incorporated within speleothems can provide an independent means of connecting large-scale climatic changes with their impact on more localized processes in soils overlying cave systems. Under certain environmental conditions, pedogenic processes can produce magnetite nanoparticles. Enhancement of pedogenic magnetite in soil profiles depends strongly on local precipitation. Pedogenic magnetite can be subsequently transferred via drip-waters into underlying cave-systems and incorporated into speleothems as they grow. Here, we employ high-resolution magnetic methods to analyze a well-dated stalagmite from Buckeye Creek Cave, West Virginia (USA), and find that changes in magnetite concentration follow both changes in stable isotopes measured in the same stalagmite and global climate proxies. We interpret the changes in magnetite concentration as reflecting variations in local pedogenic processes, controlled by changes in regional precipitation. This record demonstrates how magnetic measurements on speleothems can constrain interpretations of speleothem climate proxies.

Bedrock Channel Incision along the Upper Río Chagres Basin, Panama

Examination of various types of bedrock channel segments throughout the upper Rio Chagres network indicates the influences of lithology, rock-mass strength, jointing, and resistance to weathering on channel geometry. Bedrock channel segments throughout the upper Rio the Chagres basin take the form of step-pool sequences, pool-riffle sequences, and knickpoints and gorges. Mafic lithologies in the catchment have the greatest rock-mass strength and the longest exposures along the active channel, and are more likely to exert a strong local control on channel geometry. The longest continuous exposure of resistant rocks in the middle and lower portions of the upper Rio Chagres occurs in the Dos Cascadas reach, where upstream migration of two knickpoints has created a gorge. Surface textures (e.g., the presence of potholes) and erosion mechanisms of individual rock units in the Dos Cascadas reach correlate strongly with fracture spacing and rock hardness.

Clastic Sediments in Caves

Abstract This article focuses on the natures, origins, and significances of clastic (detrital) sediments in caves. Clastic sediments are fragments of preexisting rocks that have been transported and redeposited. Streams transport large quantities of clastic sediments through caves, including stream gravels and mud, but clastic sediments also move as gravity flows by slumping and sliding. Sedimentology and stratigraphy offer the means to understand the origins and transport mechanisms behind individual clastic deposits. Together, the two methodologies consider layering within deposits and grain sizes, sorting, mineralogies, geochemistries, and sedimentary structures. Facies are recognized where those variables include diagnostic properties tied to particular depositional processes or driving forces. As is shown using examples, stratigraphy and facies analysis make it possible to reconstruct cave or landscape histories, including system responses to disturbances such as climate change and land use. Notably, system responses typically reflect changes in sediment supply, hydraulic gradients, or obstructions. These factors are recorded in passage morphologies, which should always be considered when studying clastic sediments in caves and examples are cited.

East central North America climates during marine isotope stages 3–5

Long-term, high-resolution stalagmite carbon and oxygen isotope records from eastern North America (ENA) provide a midlatitude history of relative changes in moisture availability and climate states during the last interglacial and glacial inception (127.7 to 41.6 ka before present). The West Virginia carbon record shows low-amplitude variability at orbital time scales, superimposed on a long-term asymmetric pattern similar to global sea level changes. Relative moisture availability peaked at ~114 ka, and following a brief dry interval at ~96 ka, moisture availability gradually decreased. The almost linear change in moisture availability over ENA may reflect gradual changes in midlatitude zonal circulation as the polar cell and Laurentide Ice Sheet expanded or decreased. In contrast, our oxygen record is precession modulated and in phase with spring insolation, perhaps due to changes in precipitation seasonality. The separate pacings by eccentricity (carbon) and precession (oxygen) expose an underlying complexity that will be a challenge to explain.