The Philip M. Smith Graduate Research Grant for Cave and Karst Research

2021 Grants

Bryce K. Belanger ($2,750)
Department of Earth and Environmental Sciences
Vanderbilt University

Reconstructing mid-Holocene hydroclimate conditions in the Rocky Mountains, USA: Implications for seasonality and monsoon influence during past warm periods

Abstract: Examining patterns of precipitation and drought during warm periods in Earth’s past is critical in the effort to predict future climate changes due to human-induced global warming. Precisely-dated, high-resolution speleothem records provide the opportunity to examine the driving factors of these hydroclimate shifts. The mid-Holocene (6,000 years before present) was ~0.7C warmer than the pre-Industrial (Marcott et al. 2013; Kaufman et al., 2020), yet models and proxies disagree as to what effect this warming had on precipitation regimes throughout the western United States. In the Rocky Mountains, evidence suggests that winters were drier, but the extended influence of the North American Monsoon may have increased summer rainfall. Previously developed paleoclimate records from this region are seasonally biased, and therefore do not provide the opportunity to assess competing moisture sources on an annual timescale. To this end, I will produce a multi-proxy, semiquantitative record of past precipitation from Titan Cave, Wyoming using trace element, stable isotope (𝛿𝛿18O and 𝛿𝛿13C) and novel proxy (𝛿𝛿44Ca and Δ17O) techniques. This multi-proxy approach will allow for the reconstruction of precipitation amount, source location, and possible seasonal influences, providing a holistic view of climate change during a time considered to be an effective analog for near-future 21st century warming (Burke et al., 2018). The record developed from Titan Cave has the potential to be the best-dated, continuous, semi-quantitative record of past climate during a period of warming that bears important similarities to the 21st century.

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Rachel Bosch ($1,300)
Department of Geology
University of Cincinnati

Speleothem and charcoal dating to constrain the pace of denudation of the Sinkhole Plain, Central Kentucky Karst

Abstract: We propose to date sediments and speleothems to relate geochronology of the Mammoth Cave System to landscape evolution of the Sinkhole Plain, Kentucky, USA. Previous geochronology studies have focused on Mammoth Cave, dating the earliest incision events to ~3.25 Ma. Before that period, drainage likely consisted of stream networks over clastic bedrock. During early karstification in this region, caves developed in the Girkin limestone (elevation >250 m ASL) in the area that is now ~10 km south of the Green River and ~30 km east of the Barren River. We hypothesize that this occurred about 1–10 Ma before the development of the oldest passages in Mammoth Cave, and that the paleo cave system was part of a karst drainage feeding the Barren River to the west. In this work, we will use uranium series cosmogenic dating of speleothems from Crystal Onyx Cave, a relict passage in Prewitts Knob, and radiocarbon dating of charcoal from Little Sinking Creek on the Sinkhole Plain. These analyses will provide dates to determine the abandonment age of Crystal Onyx Cave and provide indication of the average modern rate of Sinkhole plain erosion, supplementing cosmogenic dating in progress. These results will place the development of Crystal Onyx Cave and the denudation of the Sinkhole Plain in the context of the Mammoth Cave System geochronology. This has implications for revealing timescales of the evolution of karst systems as well as the interaction of hydrological flow paths in karst areas with the transience of drainage networks.

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Andrew Oberhelman ($3,000)
Department of Geological Sciences
University of Florida

Organic carbon and methane dynamics in a carbonate karst aquifer

Abstract: Methane (CH4) is a potent greenhouse gas and a common solute in groundwater, yet the magnitude, range, and atmospheric flux of groundwater CH4 remain poorly understood, particularly in carbonate karst aquifers (CKA) where hydrology permits the rapid exchange of water and solutes between surface and subsurface. Availability of exchangeable electrons (redox potential) plays an important role in cycling of CH4 and in other processes critical to groundwater quality. Quantity and bioavailability of organic carbon (OC), also poorly understood in CKAs, can greatly influence redox potential. Four research questions are proposed to clarify linkages between CH4 cycling, OC dynamics, and hydrology in CKAs: (1) how do hydrologic conditions impact the quantity and bioavailability of dissolved OC in groundwater and spring effluent, (2) how do relative variations in OC quantity and bioavailability alter CH4 dynamics, (3) what is the magnitude and range of CH4 concentrations in discharging waters, and (4) to what extent does groundwater act as a CH4 sink or source? These questions will be explored by investigating OC and CH4 dynamics in the Upper Floridan Aquifer (UFA), which is an ideal system due to its numerous springs and a well-studied sinking stream system. Comparisons of hydrologic characteristics including flow conditions and groundwater residence time in the UFA with the cycling of CH4 and OC will reflect how changing hydrologic conditions influence CKA redox processes. Results will help elucidate controls on variations in CKA redox conditions, aid management of water quality related to redox variations, and refine global CH4 budgets.


Page last updated or validated on November 12, 2021