Geochemistry and high-resolution chemostratigraphy of the Haynesville Formation, East Texas
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The Upper Jurassic Haynesville Formation of East Texas and Louisiana is an organic-rich calcareous mudrock that is Kimmeridgian in age. It underlies the less calcareous Bossier Shale, and it overlies the Smackover Formation limestone. The Haynesville has low permeability, but a relative high porosity, compared to other mudrock formations. Mudrocks are the most common sedimentary rock and some of the most challenging to study, analyze and understand. Despite having a homogeneous appearance on a macroscopic scale, mudrocks often have high variability in facies and composition on the microscopic scale and elemental level. Many studies and methods have been developed to identify facies and stratigraphic variations in mudrocks. A complete understanding of these variations is valuable to comprehend paleoenvironments, paleoclimate and paleoceanographic conditions. Mudrocks studies are also beneficial to shale exploration because these formations, which have a high hydrocarbon content, can be targeted by oil and gas companies for exploration and production. Geochemical methods, chemostratigraphy in particular, will be used in this thesis to complement core description, petrophysical studies and sedimentological studies. This thesis focuses on acquiring chemostratigraphic data from X-Ray Fluorescence (XRF) and X-Ray Diffraction (XRD) measurements to identify elemental and mineralogical variations in the T. W. George core, from the Haynesville Formation in Harrison County, Texas. The data are linked to core description and are analyzed using Hierarchical Cluster Analysis (HCA) to acquire a better understanding of the paleoceanographic conditions and depositional environments that controlled the sediment deposition of the Haynesville Formation. The Haynesville Formation comprises a Ca-rich lower Haynesville, a more Ca-rich upper Haynesville, and underlies the Si-rich and Ca-poor Bossier. The dominant condition during deposition is anoxic/euxinic in the lower Haynesville becoming dysoxic in the upper Haynesville and more oxygenated in the Bossier Formation. The greenhouse climate of the Late Jurassic led to the deposition of strata yielding petroleum source rocks such as the Haynesville Formation that today have great economic value. Thus, studying the Haynesville has both academic and economic importance.