The Late Ordovician Biogeochemical Carbon Cycle

The isotopic composition of the carbonate carbon (δ13Ccarb) is one of the best tools for understanding the biogeochemical carbon cycle through Earth history. δ13Ccarb is also used to chemostratigraphically correlate coeval strata. This dissertation has three main foci that all utilize δ13Ccarb as the common data type. The geologic interval investigated was the Late Ordovician (458-444 Ma) with emphasis on the Guttenberg δ13C excursion, a globally correlated, positive ~3 / event that is ~400 kyr in duration. In the first topic we evaluate post-depositional alteration (i.e., diagenesis) of δ13Ccarb signals. In the second topic, we make reconstructions of sea level change using lithostratigraphic and δ13Ccarb chemostratigraphic correlations. In the third topic, we use box models to constrain the source of the Guttenberg δ13Ccarb excursion

Using S Isotopes to Identify the Source of Gypsum in Mammoth Cave

Many of the dry passages of the cave are lined with gypsum (CaSO4�2H2O) crystals, an evaporite mineral. However, the source of the sulfur in these gypsum deposits is poorly constrained with possible sources including pyrite, sedimentary gypsum/anhydrite, and carbonate associated sulfate (“CAS”, SO42- substituted for CO3 2- in the calcite crystal lattice). The two most abundant forms of sulfur in the bedrock above and around Mammoth Cave are pyrite (FeSs) and CAS. These phases commonly have very different isotopic signatures (δ34S)* and the δ34S values of these phases can be compared to the δ34S of the gypsum to aid in identifying the source of the sulfur. Isolation of sulfur from pyrite and CAS is currently ongoing. Results from 110 gypsum crystals, 4 rocks in strata from within the caves, and 15 rocks from strata overlying the caves reveal some distinct patterns. 1) Gypsum crystals show relatively small scatter (~5‰) for samples from a single location (e.g. a 30 m2 room). 2) A significant correlation between δ34Sgypsum and elevation suggests a variable δ34Ssource over vertical distances of a few meters. 3) Microsampling of sulfur along the growth axes of single gypsum crystals shows a constant δ34S values suggesting no change in δ34S of the S source during its growth. Because the growth period of these crystals may be on the order of thousands of years, these results suggest a constant sulfate for long intervals. The relationship to δ34S of samples in a given room and elevation suggests that the source of gypsum sulfur is local, arising from lateral, rather than vertical, fluid fl ow, an important insight into the transport pathways of water in a karstic system. Sampling of pyrite and CAS is currently ongoing. *δ34S = [(34S/32Ssample)/(34S/32Sstandard)-1(x)1,000‰ where 34S and 32S are the molar ratios of each S isotope given in “per mil” (‰), equivalent to parts per thousand

A Geologic Play Book for Utica Shale Appalachian Basin Exploration

This “Geologic Play Book for Utica Shale Appalachian Basin Exploration” (hereafter referred to as the “Utica Shale Play Book Study” or simply “Study”) represents the results of a two-year research effort by workers in five different states with the financial support of fifteen oil and gas industry partners. The Study was made possible through a coordinated effort between the Appalachian Basin Oil & Natural Gas Research Consortium (AONGRC) and the West Virginia University Shale Research, Education, Policy and Economic Development Center