Bourbon and springs in the Inner Bluegrass region of Kentucky · Bourbon and springs in the Inner...

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The Geological Society of AmericaField Guide 27

2012

Bourbon and springs in the Inner Bluegrass region of Kentucky

Ashley M. BartonCory W. Black Eagle

Alan E. FryarDepartment of Earth and Environmental Sciences, University of Kentucky, 101 Slone Building, Lexington,

Kentucky 40506-0053, USA

ABSTRACT

This fi eld trip explores the role of geology in the origins and production of a dis-tinctly 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 karstifi ed 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 tempera-tures (~13–15 °C) facilitated condensation of steam during distillation. We will visit three historically signifi cant 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 Frank-fort was the site of the fi rst 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).

Barton, A.M., Black Eagle, C.W., and Fryar, A.E., 2012, Bourbon and springs in the Inner Bluegrass region of Kentucky, in Sandy, M.R., and Goldman, D., eds., On and around the Cincinnati Arch and Niagara Escarpment: Geological fi eld trips in Ohio and Kentucky for the GSA North-Central Section Meeting, Dayton, Ohio, 2012: Geological Society of America Field Guide 27, p. 19–31, doi:10.1130/2012.0027(02). For permission to copy, contact [email protected]. ©2012 The Geological Society of America. All rights reserved.

INTRODUCTION

Karst terrain, which is formed by the dissolution of soluble bedrock (primarily limestone), is characterized by sinkholes, sinking streams, caves, and springs. Approximately 15% of the contiguous United States (Aley, 1984) and 55% of Kentucky (Currens, 2002) are underlain by soluble rocks. Many communi-ties in karst terrain formed around springs, which provided water for various purposes, including potable use, milling, and cooling. These uses were integral in the development of bourbon whis-key in the Bluegrass region of Kentucky. This chapter reviews

the geologic and hydrologic setting of the Inner Bluegrass and the history of bourbon production. A case study illustrates how the stable isotope oxygen-18 differs among various bourbons and how bourbon becomes systematically enriched in the isotope during aging. Finally, we summarize each fi eld-trip stop.

REGIONAL GEOLOGY

The Bluegrass region of Kentucky (Fig. 1) is bounded to the west and south by the Mississippian Plateau, to the north by the Ohio River, and to the east by the Eastern Kentucky Coal

20 Barton et al.


Field of the Appalachian basin. The Inner Bluegrass is defi ned as the 30% of the Bluegrass region that is underlain by the rela-tively fl at-lying Lexington Limestone (McFarlan, 1943), which is Upper Ordovician in age (Clepper, 2011). The Inner Bluegrass is separated from the Outer Bluegrass by the Bluegrass Hills, for-merly known as the Eden Shale belt. Fertile, residual soils (e.g., phosphatic silt loams) and numerous karst features have formed on the Lexington Limestone (Hendrickson and Krieger, 1964; McDonald et al., 1983; Newell, 1986). In the Inner Bluegrass, the Lexington Limestone rests on the underlying limestones of the High Bridge Group. Above the Lexington Limestone is the Clays Ferry Formation, which is composed of interbedded shales and thin limestone layers. Table 1 shows the generalized stratigraphy of the Lexington Limestone and subjacent and superjacent units.

Most of the Inner Bluegrass consists of a gently rolling, karst landscape dominated by fl uvial landforms. Relief is typi-cally less than 160 ft (50 m) (Thrailkill et al., 1982). The high-

est elevations, at ~1100 ft (330 m) above sea level (asl), occur in the central portion of the area. The lowest elevations, which occur along the Kentucky River in the southern and western extremes of the area, range from 469 to 549 ft (143 to 167 m) asl (McGrain and Currens, 1978). Locally, topography varies according to the rock units exposed at or just below the surface. Topography formed on the Clays Ferry Formation consists of narrow, steep-sided ridges with narrow, V-shaped valleys and dendritic drainage patterns. Thin limestone slabs cover steep slopes formed in shales in many places. In the lower part of the Clays Ferry Formation, more gently to moderately rolling uplands prevail, with small sinkholes and localized underground drainage in the limestone units. The topography formed on the upper part of the Lexington Limestone consists of broad, fl at valleys, while that formed on the lower part tends to consist of rolling to dissected uplands. Sinkholes and well-developed sub-surface drainage (solution conduits) are common. Bench-like

map area

Kentucky

Figure 1. Inner Bluegrass region of Ken-tucky (from Paylor and Currens, 2002).

Bourbon and springs in the Inner Bluegrass region of Kentucky 21


topography is formed on the more resistant shale, bentonite, and limestone layers along hillsides and valleys.

The Kentucky River fl ows along the southern and western edges of the Inner Bluegrass through a deep gorge known as the Palisades, which represents incision by the river of ~330 ft (100 m) below the adjacent land surface (Currens and Paylor, 2009). The topography formed on the High Bridge Group typically consists of cliffs and steep slopes along the Kentucky River and its tributar-ies. Numerous grikes (sub-vertical to vertical joints that have been enhanced by dissolution) occur within the walls of the gorge. The Oregon and Camp Nelson Formations only crop out at the river

and a few meters above it. The Tyrone Formation is exposed in the upper elevations of the cliffs and along the lower elevations of tributaries. The upper few meters of the Tyrone and the over-lying Curdsville Member of the Lexington Limestone form more gentle slopes extending into the uplands. At least three levels of the Kentucky River have been identifi ed near its current location. An age of ~1.5 million years for this stage of the river is suggested by radiometric dating, whereas gravel deposits and terraces indicate both a relatively young stage of the river at the lowest levels of its current valley, as well as an earlier, sub-upland stage of the river before incision into the plateau (Andrews, 2005).

TABLE 1. GENERALIZED STRATIGRAPHY OF THE LEXINGTON LIMESTONE SHOWING APPROXIMATE EQUIVALENCES WITH MAJOR LATE ORDOVICIAN CHRONOSTRATIGRAPHIC UNITS

Upp

er O

rdov

icia

n

Car

adoc

ian

Ede

nian

Clays Ferry Formation

Lexington Limestone

Upper Tongue of the Tanglewood Member

Millersburg Member

Strodes Creek

Millersburg Tongue

of the Tanglewood Member

Cha

tfiel

dian

She

rman

ian

discontinuity

Sulphur Well Member Middle Tongue of the Tanglewood

Member

Devils Hollow Member

Stamping Ground Member

discontinuity

Brannon Member Brannon Tongue of the Tanglewood Member

discontinuity

Perryville Member Lower Tongue of the

Tanglewood Member Grier Member

Kirk

feld

ian

Logana Member

Curdsville Member

Roc

k la

ndia

n

Tur

inia

n S

tage

Trenton-Maquoketa Unconformity

Bla

ckriv

eria

n

High Bridge Group

Tyrone Formation

Oregon Formation

Camp Nelson Limestone

Note: F.R. Ettensohn, Department of Earth and Environmental Sciences, University of Kentucky, personal communication, 2011.

22 Barton et al.


REGIONAL HYDROLOGY

The majority of the Inner Bluegrass is drained by the Ken-tucky River and its tributaries. All surface drainage in the region is ultimately confl uent with the Ohio River. The climate is temperate, with warm, humid summers, moderately cold winters, and no dis-tinct wet or dry seasons. The Kentucky River basin receives 46 in (117 cm) of precipitation on average annually, of which ~18 in (46 cm) contributes to surface water (Andrews, 2005).

Surface and subsurface drainages are integrated through sinkholes, conduit networks, and springs (Fig. 2). Dye-trace stud-ies by numerous workers in the Inner Bluegrass have delineated groundwater drainage basins that discharge at springs, as mapped by Currens et al. (2002, 2003). These basins are typically <6 mi2 (15 km2) in area, but can be as large as 25 mi2 (65 km2) (Thrailkill et al., 1982; Currens et al., 2002, 2003). Dye-trace results sug-gest geologic control of the groundwater basins, with overall fl ow parallel to northwest-southeast oriented linear features and faults (Currens and Paylor, 2009). In the Inner Bluegrass, groundwater basins have developed where fl ow in the reaches of former surface streams has been pirated by conduit development (C.J. Taylor, U.S. Geological Survey, personal communication, 2011).

Thrailkill (1985) characterized fl ow in groundwater basins as dendritic because of the convergence of fl ow paths from recharge through swallets (openings in streambeds), sinkholes, and other locations. A single groundwater basin can underlie more than one surface drainage basin, and the surface and subsurface basin shapes may have little relationship to each other. Conduits under-lying the groundwater basins are nearly horizontal, have gradi-ents approximating those of the surface streams, and are almost at the same level as the springs which drain them, although fl ow from the swallet recharging a conduit tends to have a much

higher gradient. Flow directions in the groundwater basins often have little or no relationship to fl ow in the surface streams above. The potentiometric surface in the Lexington Limestone is rep-resented by the water surface in the larger conduits where fl ow occurs under equilibrium conditions (Thrailkill, 1985). As such, it is very irregular in both lateral and vertical extent.

Although subsurface overfl ows between groundwater basins are known to exist (Currens et al., 2002), interbasin subsurface fl ow generally appears to be limited to small conduits in the epi-karst zone that are shallow and oriented parallel to land surface. Flow follows the topographic slope to emerge at small, high-level springs that tend to be ephemeral. These interbasin areas form part of the catchment areas for large springs draining the groundwater basins. Surface streams and high-level springs are commonly perched on shaly and argillaceous facies within the Millersburg and Brannon Members of the Lexington Limestone (Thrailkill et al., 1982).

In the area of this fi eld trip, Carey and Stickney (2002, 2004a, 2004b, 2005a, 2005b) divided the Lexington Limestone into upper and lower hydrostratigraphic units for the purpose of describing groundwater occurrence. The upper unit was defi ned to consist of the Strodes Creek, Millersburg, Tanglewood Lime-stone, Devils Hollow, Stamping Ground, Sulphur Well, and Bran-non Members. The lower unit included the Grier, Logana, and Curdsville Members. It should be noted that this does not cor-respond to the most current stratigraphic delineation of the Lex-ington Limestone as described in Clepper (2011) and depicted in Table 1. In the upper unit, discharge rates can exceed 100 gallons per min (gpm) (380 L/min) for some large springs and can be 300 gpm (1100 L/min) from wells along large streams (Carey and Stickney, 2002, 2004a, 2004b, 2005a, 2005b). In the lower unit, discharge occurs to numerous springs, and wells can yield

Figure 2. Conceptual block diagram of Inner Bluegrass karst (not to scale) (Currens, 2001).



up to 150 gpm (570 L/min) along large streams (Carey and Stick-ney, 2002, 2004a, 2004b, 2005a, 2005b).

In general, the quality of groundwater in the Bluegrass region depends on its geologic source and varies considerably from place to place (Carey and Stickney, 2002, 2004a, 2004b, 2005a, 2005b). Major-ion chemistry of shallow groundwater and streams originating in the Bluegrass region is a Ca-Mg-HCO

3

type with near-neutral pH, consistent with weathering of car-bonate rocks by meteoric recharge. Total dissolved solids (TDS) range from 200 to 400 mg/L for shallow groundwater and 100–250 mg/L for streams (Hendrickson and Krieger, 1964). In the Inner Bluegrass, groundwater tends to be hard to very hard; the main constituents that negatively affect groundwater for domes-tic use are chloride and hydrogen sulfi de. Saline water (defi ned as TDS > 1000 mg/L) is typically found at depths >100 ft (30 m) below principal valley bottoms in the fi eld-trip area (Carey and Stickney, 2002, 2004a, 2004b, 2005a, 2005b).

BOURBON

History of Bourbon

The development of bourbon whiskey occurred after settlers from the British Isles, who were experienced in distilling grain spirits, encountered corn in eastern North America. The still was invented around 800–1000 CE (Pacult, 2003); distillation was introduced to Europe by the 1100s and to the British Isles by the 1200s (Crowgey, 2008). Production of whiskey evolved in northern Europe because the climate was conducive to the cul-tivation of grains but not grapes (i.e., making beer rather than wine) (Allen, 1998). Popularity of distilled beverages arose in part because water was associated with disease (Murray, 1998). Even the process of charring the oak barrels for bourbon may have begun as a way to sterilize the wood (Crowgey, 2008).

One of the earliest records of a beverage made from fer-mented corn is that of George Thorpe in the Jamestown, Vir-ginia, settlement around 1622 (Carson, 1984; Regan and Regan, 2007). Corn was harvested in what is now Kentucky starting ca. 1774. Prior to 1778, settlers there could claim 400 acres (162 ha) of land if they would build a cabin and plant corn (Regan and Regan, 2007). As summarized by Fryar (2009), whiskey produc-tion emerged in various locations across the Bluegrass region in the 1770s and 1780s. Rye was another grain used to make whis-key; it grew readily and could be used as a cover crop or to feed livestock (Murray, 1998; Crowgey, 2008). Whiskey’s appeal was furthered by the fact that a farmer could earn more than 25 cents per gallon (3.8 L) for whiskey on the frontier, as compared to a mere 10 cents for a bushel (35 L) of corn, which would yield 4–5 gallons (15–19 L) of whiskey (Kroll, 1967).

From the 1790s to the 1830s, technological developments and market forces led to the commercialization of whiskey pro-duction in Kentucky. The limited availability of rum, which was distilled from sugar cane grown in the West Indies, gave corn and rye whiskey a market advantage in the United States (Car-

son, 1984; Crowgey, 2008). Small farmers began to supply grain to larger distillers around 1800, and the range of proportions of grains used in making bourbon was established by 1823 (Regan and Regan, 2007; Crowgey, 2008). James Crow is credited with the standardization of bourbon production in the 1820s and 1830s, examining the science behind brewing and implementing use of thermometers, hydrometers, and saccharimeters (Allen, 1998; Murray, 1998). The mid-1800s brought about the use of a second distillation for purifi cation and increased ethanol content (Pacult, 2003).

Besides the grains used and the aging process, the character of bourbon is often attributed to limestone water (Kroll, 1967; Carson, 1984; Murray, 1998; Pacult, 2003; Regan and Regan, 2007). Shallow groundwater and stream water in the Inner Blue-grass contain suffi cient O

2 to limit dissolved iron, an undesir-

able constituent (Hendrickson and Krieger, 1964; Allen, 1998). The pH of carbonate-buffered water also promotes fermentation (Willkie and Prochaska, 1943; Carson, 1984; Murray, 1998; Pacult, 2003). In addition to the suitable chemistry of groundwa-ter, springs were historically desirable because their temperatures (~13–15 °C) facilitated condensation of steam during distillation (Carson, 1984; Fryar, 2009). However, given the need for rela-tively large volumes of water in industrial-scale processes, the use of springs in bourbon production has waned (Fryar, 2009). For example, Four Roses uses water from the Salt River; Ancient Age and Wild Turkey use water from the Kentucky River; and Bernheim and Early Times use dechlorinated city water (Murray, 1998). Nonetheless, some distilleries still rely on groundwater. Barton uses water from a spring and spring-fed lake; Maker’s Mark also uses a spring-fed lake; and Woodford Reserve uses water from an 80-ft (24-m) well (Murray, 1998).

Bourbon Production

Certain criteria must be met in order for a beverage to be considered bourbon. It must be distilled in the United States and have a grain composition of at least 51% corn. The beverage can-not be artifi cially altered (e.g., by special fi lters or additives), and it must be aged for at least 2 years in new, charred, white oak bar-rels. It cannot be distilled higher than 160 proof (80% alcohol) or put into barrels at higher than 125 proof (62.5% alcohol). Within these strict guidelines, distillers create their own distinct fl avors by using different water sources, altering the proportion and type of grains, using different yeast strains during fermentation, and/or aging their products for differing amounts of time.

To begin making bourbon, corn, rye (or wheat), and malted barley are ground to a fi ne powder and dissolved in water. The mixture is heated (commonly in a steam pressure cooker) to pro-duce sweet mash. After this has cooled, a portion of a previous batch, known as sour mash, is added. Sugars in the mash feed yeast, which produces CO

2 and ethanol (C

2H

5OH). This fer-

menting process typically takes 3 to 5 days. The fermented prod-uct, also known as brewer’s beer, is sent to a beer still, where steam creates an alcohol-rich vapor. This vapor is condensed to

24 Barton et al.


create a low wine, which is passed through a second still to cre-ate high wine (also known as white dog). High wine is placed in new, charred, white oak barrels and put in a warehouse for a minimum of 2 years. During this time, the high wine migrates into the walls of the charred oak barrel, picking up fl avors from the wood. Seasonal variations in temperature aid the migration of the product in and out of the barrel. Water and some ethanol evaporate through the wood into the surrounding air (known as the angels’ share). Loss of water through evaporation increases the proof of the product inside the barrel. After the appropriate time frame, the master distiller will sample products and may choose to mix, or marry, barrels to achieve a certain fl avor pro-fi le for the fi nal product.

Study of Stable Isotopes within Bourbon

Atoms containing the same number of protons but differing numbers of neutrons are called isotopes. There are ~300 stable and 1200 radiogenic isotopes. Stable isotopes have been used to examine a variety of natural processes, including paleocli-matology, elemental cycling (e.g., biomolecules within an eco-system), thermometry, and reaction mechanisms (Sharp, 2007). Stable isotopes of hydrogen (2H) and oxygen (18O) can be used to differentiate between waters from varying sources (Mook, 2006). Stable isotopes can also be used to evaluate food qual-ity and origin, such as dilution of fruit juices or wine with water ( Monsallier-Bitea et al., 2006).

Stable isotope abundances are commonly expressed in delta notation, which compares the rare isotope/common isotope ratio in a sample (sa) to the same ratio in a standard (std). Typically, the rare isotope is heavier (i.e., contains more neutrons). For oxygen, the international standard is Vienna Standard Mean Ocean Water (VSMOW), which has an 18O/16O ratio of 0.0020052. Delta nota-tion is measured in units of per mil (‰) and is calculated using the following formula:

δ18O(‰) = – 1 × 1000

18Osa

16O

sa

18Ostd.

16O

std.

(1)

Because of their differential masses, different stable iso-topes of a given element can be fractionated by natural processes. Knowledge of these fractionations can help in delineating the fate of stable isotopes in the environment. One type of fractionation is known as the equilibrium isotope effect: because molecules of greater relative mass have greater dissociation energies, there is a preference for the heavy isotope to occur in one phase. The kinetic isotope effect is a result of unidirectional processes such as water evaporating from a puddle. Evaporation causes 18O enrichment in surface waters (Mook, 2006) as 16O preferentially partitions to the vapor phase. Progressive depletion of water vapor in 18O as air masses move from the equator toward the poles is an example of

Rayleigh fractionation, which can incorporate both equilibrium and kinetic isotope effects.

We examined fractionation of 18O in bourbon. It was hypoth-esized that products would become depleted in 18O during distil-lation, with high wine being isotopically lighter than low wine, and low wine being isotopically lighter than the source water. We also hypothesized that fi nal products would become progres-sively enriched in 18O during the aging process. Samples were collected at various steps in the bourbon-making process from three distilleries: Wild Turkey and Four Roses (both in Law-renceburg, Kentucky) and Jim Beam (in Clermont, Kentucky). These samples included tap/source water, low wine, high wine, deionized water, steam, cut water, and fi nal products of vary-ing ages. Samples were taken to the University of Kentucky and stored at 4 °C until analysis. In the stable isotope laboratory, exe-tainers were prepped by adding one to two drops of phosphoric acid before fl ushing with a 0.3% CO

2/He mixture. Equilibration

with CO2 was conducted after injection of 1 mL sample prior to

analysis on the isotope-ratio mass spectrometer. The δ18O value obtained for the CO

2 gas was used as a proxy for the δ18O value

of the liquid sample.There was evidence of Rayleigh fractionation in both the

distillation and aging of bourbon. Figure 3 shows that δ18O val-ues decreased through the process from the source water to low wine to high wine. Source water values are similar to a sample of deionized Lexington tap water (−8.0‰ ± 0.1‰; C.S. Romanek,

Sou

rce

wat

er

Low

win

e

Hig

h w

ine

Fin

al p

rodu

ct -20

-18

-16

-14

-12

-10

-8

-6

-4

δ18O

(‰

vs.

VSM

OW

)

Figure 3. δ18O values for water and samples throughout the bourbon-making process at the Wild Turkey, Four Roses, and Jim Beam distilleries.



Department of Earth and Environmental Sciences, University of Kentucky, personal communication, 2011). This supports our hypothesis that lighter isotope fractions are removed from the mixture as water and ethanol evaporate in the stills. The evapora-tion of lighter fractions is also responsible for the heavier δ18O values of fi nal products. As each distiller’s product ages and water is lost through the barrel, the bourbon left in the barrel becomes increasingly enriched in 18O (Fig. 4). Differences in 18O compositions among distilleries at each stage of the process may refl ect the isotopic composition of the grains used (which were not examined in this study), temperatures of distillation, and/or infl uences of the particular yeast strains involved. This may indicate a particular isotope signature for each distillery, which could be of future use for quality control. However, further stud-ies would be needed to evaluate this inference.

FIELD STOPS (Fig. 5)(Note: 1.0 mile = 1.6 km)

Mileage Directions 0.0 Take I 75 S exit 126 for U.S. 62 toward

Georgetown/Cynthiana, Kentucky. 0.4 Slight right onto U.S. 62 W/Cherry Blossom Way. 1.1 Turn right onto Paris Rd./Paris Pike (U.S. 460 W),

continuing to follow Paris Rd. 1.7 Continue onto E. Main St. (U.S. 460 W). 2.3 Turn left onto S. Broadway St. (U.S. 25 S) 2.4 Take 2nd right onto W. College St.

Stop A (Mile 2.5): Royal Spring, Georgetown, Kentucky

Royal Spring (Fig. 6) is the primary water supply for the city of Georgetown (population ~21,000), as well as portions of Sadieville, Stamping Ground, Midway, and Lexington. In 1789, Elijah Craig operated a distillery at Royal Spring (Allen, 1998), which was designated the birthplace of bourbon by Richard Collins in his 1874 History of Kentucky. However, subsequent authors identifi ed evidence of whiskey-making elsewhere in Kentucky between 1776 and 1781 (Regan and Regan, 2007; Crowgey, 2008). Royal Spring emerges from the Grier Member of the Lexington Limestone and sustains a tributary to North Elk-horn Creek. A karst conduit system carries all base fl ow and a large but unmeasured percentage of high fl ow discharge from the Cane Run watershed to Royal Spring, which is located outside the boundary of the Cane Run watershed.

Cane Run is a fourth-order stream that originates in central Fayette County and fl ows north into North Elkhorn Creek in Scott County. The main stem of Cane Run is ~17 mi (27 km) long and drains an area of 45 mi2 (116 km2). The watershed con-sists of 25% urban land, primarily in northeast Lexington, and 75% rural land, including farms, light industry, a quarry, and rural and suburban residences. Discharge from the headwater tributaries of Cane Run is sustained in the dry season by urban runoff and interbasinal, perched springs. However, the middle reach of Cane Run is normally dry and only carries discharge during fl oods. Heavy rainfall causes sudden, large increases of stream fl ow, followed by a brief recession and then a sud-den cessation of discharge. Swallets along the channel of Cane Run govern the partitioning of runoff between surface fl ow and groundwater. When intense rainfall occurs in the dry season, recharge to the conduit is limited by the hydraulic capacity of the conduit because such events may not fi ll it to full pipe fl ow. During the wet season, conduit discharge capacity is close to maximum and surface fl ow extends further downstream, as conceptualized in Figure 7.

Qualitative and quantitative dye traces have been conducted within the Royal Spring basin in order to delineate the basin boundaries (Fig. 8) and determine groundwater travel times. Groundwater velocities ranged from over 1 mi/h (1.6 km/h) dur-ing storm events to less than 0.15 mi/h (0.24 km/h) in dry condi-tions (Paylor and Currens, 2004). Contaminants may travel more slowly, depending upon their sources and whether attenuation occurs in epikarst or within the conduit (e.g., as a consequence of adsorption onto sediment [Reed et al., 2010]). Using two-dimensional, three-dimensional, and time-lapse electrical resis-tivity surveys (with salt injection), Zhu et al. (2011) suggested the location of the main conduit of the Royal Spring groundwater basin beneath the middle reach of Cane Run.

Mileage Directions

2.6 Head east on W. College St.; turn right onto S. Broadway St. (U.S. 25 S); continue as U.S. 25 S becomes Lexington Rd./Georgetown Rd.

Fin

al r

ye w

hisk

ey

Fin

al 1

yea

r

Fin

al 6

yea

r

Fin

al 7

yea

r

Fin

al 8

yea

r

Fin

al 1

0 ye

ar

Fin

al 1

4 ye

ar

Fin

al 1

6 ye

ar

Fin

al 1

9 ye

ar -20

-18

-16

-14

-12

-10

-8

-6

-4

δ18O

(‰

vs.

VSM

OW

)

Figure 4. δ18O values for fi nal products of the Wild Turkey, Four Roses, and Jim Beam distilleries.

26 Barton et al.


Figure 5. Field-trip route map through Inner Bluegrass region (from Google Maps, November 2011).

Figure 6. Royal Spring (photo by A.E. Fryar, April 2009).Figure 7. Conceptual diagram of fl ow along Cane Run (not to scale) (modifi ed from unpublished fi gure, Kentucky Geological Survey).



Figure 8. Inset of mapped karst groundwater basins in Fayette and Scott Counties, Kentucky (from Currens et al., 2002).

28 Barton et al.


13.7 Bear right as U.S. 25 S merges with Newtown Pike (KY 922 S).

14.2 Continue onto Oliver Lewis Way (KY 922 S).14.4 Turn right onto KY 1681 W (Manchester St./Old

Frankfort Pike).15.6 Turn left onto McConnell Springs Rd. and left onto

Cahill Dr.; take the 1st right onto Rebmann Ln.

Stop B (Mile 15.9): McConnell Springs, Lexington, Kentucky

The McConnell Springs site is located in a 26-acre (11-ha) city park within the Wolf Run watershed in Lexington. The springs occur within a karst window, a cave passage unroofed by solution collapse. The Grier, Brannon, and Tanglewood Mem-bers of the Lexington Limestone are exposed on the site. The Grier Member, which is relatively transmissive because of disso-lution along fractures and bedding planes, underlies ~80% of the site. The park contains more than 130 species of plants, includ-ing bur oaks (Quercus macrocarpa) that are thought to remain from pre-settlement grassland savannas more than 250 years ago (Friends of McConnell Springs, 2010).

During the summer of 1775, a party from southwestern Pennsylvania, including William McConnell, surveyed land along the tributaries of Elkhorn Creek with the intent of fi ling land claims with the state of Virginia, of which Kentucky was a part. William McConnell claimed the “sinking springs” that now bear his name (O’Malley, ca. 2006). Legend has it that these pio-neers were camped at the springs when they received word of the Battle of Lexington (Massachusetts) and decided to name the

settlement after it. The actual town was not formed until 1779. Various land uses have occurred around the springs during the past two centuries, including a gunpowder mill, stock farming, commercial bourbon production, and dairying (O’Malley, ca. 2006). Remnants of dry-stone fences are evidence of Irish and Scottish immigrant masons who began working in the 1830s. The city park was created in the 1990s after a failed effort to develop the site as an industrial park. Adjoining land use remains partly industrial; in particular, Vulcan Materials quarries lime-stone from the Tyrone, Oregon, and Camp Nelson Formations more than 435 ft (133 m) beneath the springs. However, because of the presence of bentonite near the top of the Tyrone Forma-tion, the permeability of those units is so low that spring fl ow is not noticeably affected (Currens and Paylor, 2009; Friends of McConnell Springs, 2010).

Blue Hole is the fi rst of two major springs seen in McCo-nnell Springs Park (Figs. 9, 10). The name of this artesian spring is derived from its color, which results from the depth of the orifi ce (>15 ft [4.6 m]). Water discharging at Blue Hole has been traced from swallets and sinkholes as far as 2.5 mi (4.0 km) south and southwest of the spring (Currens et al., 2002; Friends of McConnell Springs, 2010) (Fig. 8). Discharge at Blue Hole is sensitive to rainfall. Water fl ows over the sur-face for tens of feet before sinking; it resurges at the second artesian spring in the park, known as the Boils (Figs. 9, 11). At this location, water is under suffi cient pressure (rising as much as 2 ft [0.6 m] above the spring pool after heavy rains) that it appears to be boiling, even though its temperature is ~56 °F (13 °C). Discharge from the Boils fl ows in a stream chan-nel ~1000 ft (300 m) to the Final Sink, where it disappears

Figure 9. Conceptual block diagram of fl ow at McConnell Springs (not to scale) (modifi ed by S.F. Greb from Friends of McConnell Springs [2010]).



underground and travels ~0.3 mi (0.5 km) to Preston’s Cave. Discharge from Preston’s Cave fl ows to Wolf Run and thence to Town Branch of Elkhorn Creek.

Mileage Directions

16.1 Turn left from Rebmann Ln. onto Cahill Dr., right onto McConnell Springs Rd., then left onto Old Frankfort Pike (KY 1681 W).

30.6 Turn left onto Steele Rd. (KY 1685).33.6 Slight right onto KY 2331/McCracken-Steele Rd./

New Cut Rd.34.4 Turn right onto McCracken Pike (KY 1659 N).35.2 Distillery is on the left (7855 McCracken Pike).

Stop C (Mile 35.2): Woodford Reserve Distillery, Versailles, Kentucky

Woodford Reserve Distillery (Fig. 12) traces its origins to 1797, when Elijah Pepper began making whiskey in Woodford County (Kentucky Distillers’ Association, 2010). Distilling on the current 72-acre (29-ha) site began ca. 1812 using water from Grassy Springs Branch of Glenns Creek (National Park Service, 2008; Kentucky Historical Society, 2011). Elijah’s son Oscar Pepper employed James Crow as master distiller in the 1830s (National Park Service, 2008; Kentucky Historical Society, 2011). Leopold Labrot and James Graham purchased the distillery from the Pepper family in 1878 (Kentucky Bourbon Trail, 2006). The Labrot & Graham Distillery operated until 1941 (Bourbon Central, 2011); Brown-Forman purchased it and reopened it in 1996 (Brown-Format, 2004). As a small-batch distiller, Wood-ford Reserve uses a single, proprietary yeast strain to produce a consistent fl avor profi le. The mash bill (recipe) consists of 72% corn, 18% rye (to which the spicy character of the bourbon is attributed), and 10% malted barley (Woodford Reserve, 2011). Woodford Reserve uses cypress fermentation tanks and triple distills its whiskey in three copper-pot stills (Fig. 13), depicted in the emblem stamped on the ends of its oak barrels.

Mileage Directions

35.2 Continue on McCracken Pike/Glenns Creek Rd./Martin Luther King Dr. (KY 1659 N).

43.9 Turn left onto E. Main St. (U.S. 60 W).44.7 Turn right onto High St. (KY 420).44.9 Bear right onto Holmes St. (KY 2261).46.6 Continue onto Owenton Rd. (U.S. 127 N).46.8 Turn right onto Cove Spring Rd. and take the fi rst

left onto Deadhorse Rd.47.0 Travel to end of Deadhorse Rd.

Figure 10. Blue Hole, McConnell Springs (photo by A.E. Fryar, April 2009).

Figure 11. The Boils, McConnell Springs (photo by A.E. Fryar, April 2009).

Figure 12. Woodford Reserve Distillery (photo by A.E. Fryar, Novem-ber 2008). Warehouse for aging bourbon is at right.

30 Barton et al.


Stop D (Mile 47.0): Cove Spring Park, Frankfort, Kentucky

Cove Spring Park, which is owned by the City of Frank-fort, consists of ~100 acres (40 ha) of meadows, wetlands, and forested ravines within the Kentucky River valley. The park was established in part to preserve Braun’s rock-cress (Arabis per-stellata), an endangered wildfl ower (Frankfort Area Chamber of Commerce, 2011; U.S. Fish and Wildlife Service, 2011). In 1800, settlers impounded Cove Spring to form Frankfort’s water supply, which was distributed through pipes made from cedar logs cut on-site (Frankfort Area Chamber of Commerce, 2011). An overfl ow tower constructed of locally quarried limestone still stands at the site. Clepper (2011) described the stratigraphy of a 280.8-ft (85.6-m) measured section at the site, which extends from the Tyrone Formation along the valley fl oor to the upper tongue of the Tanglewood Member of the Lexington Limestone at the top of the escarpment (Table 1).

Mileage Directions

47.3 From Cove Spring Rd., turn left onto Owenton Rd. and immediately take the ramp onto U.S. 127 S/U.S. 421 N/Wilkinson Blvd.

49.2 Turn right onto U.S. 127 S/W. Frankfort Connector; continue on U.S. 127 S.

67.4 Turn right onto KY 513/Bonds Mill Rd./Hickory Grove Rd.

68.5 Turn right; destination will be on left.

Stop E (Mile 68.5): Four Roses Distillery, Lawrenceburg, Kentucky

In 1888, Paul Jones Jr. trademarked the name Four Roses as a brand of bourbon. The present distillery was built in 1910 in a Spanish mission style unusual for Kentucky. In 1922, the Paul Jones Company purchased the Frankfort Distilling Company, one of six distilleries authorized to produce bourbon for medici-nal purposes during Prohibition (Four Roses, 2011). Frankfort Distilling was sold to Seagram in 1943, which produced Four Roses straight bourbon whiskey (as opposed to blended whiskey) only for export for more than 40 years. In 2002, the distillery was acquired by the Kirin Brewery of Japan, which reintroduced Four Roses straight bourbon to the American market (Four Roses, 2011). Four Roses uses a combination of fi ve yeast strains and two mash bills to produce 10 bourbon recipes, each with its own fl avor profi le. Only one recipe is used in the Single Barrel prod-uct, whereas four recipes are combined to create Small Batch, and up to ten recipes are used to create Yellow Label. One mash bill includes 75% corn and 20% rye, whereas the other includes 60% corn and 35% rye; both include 5% malted barley (Four Roses, 2011). In contrast to Woodford Reserve, which ages its bourbon on-site, Four Roses uses warehouses in Cox’s Creek, Kentucky, approximately a 1 hour drive west of the distillery.

ACKNOWLEDGMENTS

Chuck Taylor, Dorothy Vesper, Jim Currens, Brent Elliott, and Mike Sandy made helpful comments on the manuscript. Terry Hounshell, Steve Greb, and Collie Rulo provided illustra-tions. We appreciate the suggestion of the Cove Spring Park stop by Marta Clepper and the guidance of Chris Romanek in isotopic analyses. Special thanks to Four Roses, Wild Turkey, and Jim Beam distilleries for their participation and help with sample collection.

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