Whetstone is a tributary of Buck Creek located within the Dykes Quadrangle
in eastern Pulaski County. Buck Creek has been an important factor in the
geomorphic development of karst in Pulaski County. From its headwaters at
the edge of the Mississippian Plateau near Muldraughs Hill (the escarpment
separating the Mississippian rocks from the Devonian and Ordovician strata
of the Bluegrass) at Hall's Gap, Buck Creek flows south for 99 miles across
the Mississippian Plateau, through the Cumberland Escarpment near Shopville,
Kentucky, and through a deep valley in the Cumberland Plateau to discharge
on the Cumberland River. The Cumberland Escarpment is a widespread geologic
and topographic feature that separates the Cumberland Plateau to the east
from the Mississippian Plateau to the west. The plateau surface is covered
by near horizontal Pennsylvanian clastics underlain by Mississippian carbonates.
These units have a slight regional dip to the southeast of 1 to 2 degrees.
This escarpment is highly karstified, and karst development is present in
the Mississippian limestones along the entire length of Buck Creek. Deep
tributary valleys draining into Buck Creek are incised in the Cumberland
Plateau, and numerous karst aquifers of significant size have developed
in these valleys such as: Sinking Valley, Wells Cave, Farmers System, Richardson
Cave/Long Hollow, Hail System, and Coral Cave.
Whetstone Valley is an incised valley typical of those located in the region.
It is about 8 miles in length and drops approximately 500 feet of elevation
before discharging at Buck Creek. The upstream half of the drainage is subdivided
into two "prongs", Langford Prong and Snell Prong. Langford Prong
drains the larger surface area of the two. The bulk of the valley is oriented
roughly parallel to the strike of the rocks. Three miles from the headwaters,
the stream sinks into the uppermost limestone unit through small swallets
in the streambed, becoming a dry streambed for the remainder of its length
during normal flow conditions. The water in the valley is carried from these
swallets through the karst aquifer to a resurgence spring on the banks of
Buck Creek. In peak flow and flood events, the karst conduits become flooded
and Whetstone Creek becomes a raging torrent overflowing its banks. The
water is carried downstream flooding other swallets and enters the karst
aquifer at the Upper Sinks. A few hundred feet downstream and about 25 feet
higher in elevation is the Lower Sinks, which rarely sees water. It is a
rare flood event that overflows these sinks as noted by the presence of
significant vegetation and lack of channel deposits further down-valley.
All water from the valley resurges at the spring and the overflow conduit
located proximal to the spring.
Four limestone units are responsible for the development of karst in the
region. The lowermost is the St. Louis Limestone (Msl), a light-gray, fine
grained, thin bedded limestone This limestone is only exposed in the lower
bluffs and bed of Buck Creek. The Ste. Genevieve Limestone (Mmg) lies above
the St. Louis and is a very light-gray limestone with numerous chert beds
and nodules. This unit composes the floor of Whetstone Valley and contains
most of the active stream passages. Above the Ste. Genevieve lies the Kidder
Limestone (Mmk), a light-gray, variable bedding, oolitic to crystalline,
fossiliferous limestone. The Ste. Genevieve and the Kidder limestones are
collectively called the Monteagle Limestone. The Kidder limestone forms
the lower parts of the valley wall. It contains mostly older upper level
passages underneath the ridges and domepit complexes. The Hartselle Shale
(Mha) is a thin, soft, green layer of shale that ranges from six inches
to a foot thick. Above the Hartselle Shale lies the Bangor Limestone (Mba),
a dark-gray, medium-grained limestone. It contains many domepit complexes
in the sides of the ridge. Above these limestone units lie the Pennington
Formation, the upper most Mississippian age unit composed of mostly shale
with interbedded lenses of silt, sand, and limestone. Numerous sandstones
and shales of the Pennsylvanian age, including the Lee Formation, create
an effective caprock prohibiting downward dissolution in the surrounding
ridges. Within these Pennsylvanian strata are several coal beds that have
been extensively mined in the region.
For the first segment of the valley's history it was a non-karstic stream
eroding through the Pennsylvanian sandstones and shales. Immediately upon
breaching the caprock, karst development began to occur. Throughout its
geomorphic development, karst in Whetstone has been "Cumberland Style"
(Sasowsky, 1994). Phreatic passages represent the master drains for the
valley located near or below water table and tend to follow a combination
of surface topography and strike. Vadose conduits form above the water table
from either sinkpoints or vertical shafts and carry water to the base level
phreatic conduits. These vadose conduits follow combinations of the dip
and jointing or fracturing of the rock. A high percentage of conduits in
Whetstone valley are oriented along the strike (60°-240°) with secondary
peaks at the dip angle (150°) and a set of orthonormal joints (110°-290°;
and 20°-200°).
When karst development initiated, phreatic passages began to develop, underdraining
Whetstone Creek and resurging at springs along the former channel of Buck
Creek. As uneven erosion occurred in the valley, sinkpoints developed, which
fed short high-gradient vadose cave passages, dropping in elevation rapidly
along the dip and along joints feeding the developing phreatic conduits.
Valley enlargement was aided by vertical shaft development (Brucker, Hess,
and White, 1972). Truncation of old passages and creation of new ones occurred
as Whetstone Creek continued to downcut an incised valley. Passages that
developed underneath ridges were truncated by valley enlargement and remained
as segments of dry upper paleo-flow levels of the cave. This phreatic paleo-conduit
system can be seen in the trunk passages of both Little-Hargis and Saltpetre
pit caves; this system represents a stable period in valley downcutting
(White, 1988). This system of conduits was subsequently filled with sediment
during flood events.
A larger area of karstification developed during a period of increased erosion,
and another level of strike-oriented phreatic conduits formed. This new
phreatic conduit system is seen in the Hyper Hydraulic Highway of the Sinks
Cave. Renewed erosion also caused the development of a series of vadose
passages that feed the current phreatic conduits. These vadose conduits
have, in locations, been pirated through segments of the paleo-conduit system
and have reworked the sediments in these locations. This can be best seen
in the trunk conduit of Little-Hargis. The flow from the Waterfall Section
of the cave has been pirated and now flows up-valley through the phreatic
paleo-conduit.
The collapse within Grand Chasm of the Sinks Cave segmented the Hyper Hydraulic
Highway and has promoted the development of a system of floodwater diversion
routes as described by Palmer (1975). Using similar logic, the more recent
formation of the Upper Sinks entrance could have again segmented HHH and
another floodwater diversion maze could be forming upstream of this. The
upstream continuation of HHH could be found during the exploration of die
Höhle. It is possible that yet another sink entrance is in its infancy
where several swallets are located upstream from die Höhle.
