Abstract This field trip explores the role of geology in the origins and production of a distinctly American distilled spirit. Bourbon whiskey originated in the late 1700s and early 1800s in the Bluegrass region of north-central Kentucky. The Inner Bluegrass is marked by fertile, residual soils developed on karstified Ordovician limestones. Corn was grown, ground, fermented, and distilled to yield a high-value product that would not spoil. The chemistry of limestone water (dilute calcium-bicarbonate type with near-neutral pH) limits dissolved iron and promotes fermentation. Many farms and settlements were located near perennial springs, whose relatively cool temperatures (~13–15 °C) facilitated condensation of steam during distillation. We will visit three historically significant springs. Royal Spring in Georgetown was an early site of whiskey production and is one of the few springs in Kentucky still used for municipal water supply. McConnell Springs was the purported site of Lexington’s founding and occupies a karst window in which distilleries once operated. Cove Spring in Frankfort was the site of the first public water supply west of the Allegheny Mountains. We will also tour two distilleries: Woodford Reserve (among the oldest and smallest in the state, and a National Historic Landmark) and Four Roses (listed on the National Register of Historic Places).

The chemostratigraphic (δ 13 C carb ) record of the Lexington Limestone in central Kentucky is a high-resolution record in Chatfieldian and lower Edenian strata. Parts of the Lexington Limestone in this region reflect an anomalous structurally controlled carbonate buildup with complex facies relationships. Chemostratigraphic analysis of buildup and off-buildup composite sections, which exemplify the Lexington facies mosaic, reveals an overall decreasing trend in 13 C compositions throughout the formation and into the overlying Clays Ferry Formation. Superimposed on this trend are four locally correlative excursions. The most significant excursion is found within the Logana Member. The Guttenberg excursion is locally expressed as two prominent δ 13 C peaks (maxima +2.58‰). The excursion is important because of its stratigraphic position above the regional and globally correlated Millbrig K-bentonite, which allows for correlation with chronostratigraphically equivalent successions. The ubiquity of the Guttenberg excursion has been recognized throughout the eastern and central United States and the Baltic region. Additional excursions have been detected and are common in other sections, showing that the chemostratigraphic record of the Lexington Limestone is similar in buildup and off-buildup sections, even across complex lithofacies boundaries. The similarity of the record across complex facies, moreover, suggests that these localized excursions are “events,” which can be used to constrain correlations and augment known facies relationships. Furthermore, the overall chemostratigraphic trend in the Lexington Limestone appears similar to published δ 13 C values from equivalent strata in Baltoscandia, emphasizing the global correlative value of chemostratigraphic trends in Upper Ordovician strata.