Geology Along the Martha Layne Collins Bluegrass Parkway Daniel I. Carey, Martin C. Noger, and Donald C. Haney The oldest rocks exposed at the surface in Kentucky, the 450-million-year-old Camp Nelson Limestone formed in the Ordovician Period, can be seen at the Kentucky River Palisades. Martha Layne Collins Woodford Bluegrass Parkway Anderson Nelson Mercer Kentucky Geological Survey Hardin Washington James C. Cobb, State Geologist and Director SPECIAL PUBLICATION 11 Series XII, 2011 UNIVERSITY OF KENTUCKY, LEXINGTON 2 Terrain Along the Bluegrass Parkway While travelling the Bluegrass Parkway, you will see a variety of terrain. Where natural landforms (lay of the land) differ significantly from one area to another, this generally indicates that each landform is underlain by a different type of rock. These different areas are known as physiographic regions. The major physiographic regions crossed by the Bluegrass Parkway are the Pennyroyal, Muldraugh's Hill, Knobs, Outer Bluegrass, Bluegrass Hills, and Inner Bluegrass. Figure 1 shows all physiographic regions in Kentucky, as well as the location of the Bluegrass Parkway. As you drive east along the parkway to mile 3.5, you are in the Pennyroyal Region. The Pennyroyal is an upland underlain 90°W 89°W 88°W 87°W 86°W 85°W 84°W 83°W 82°W by limestone and characterized by complex underground drain- 39°N 39°N age systems marked by sinkholes and caves; the limestone Inner Bluegrass Bluegrass Hills weathers to form thick, reddish residual soils. Most of the lime- Outer Bluegrass stones in this area were deposited in an ancient sea that was Knobs Martha Layne Collins similar to Florida Bay. Mississippian Plateau Bluegrass Parkway Eastern Kentucky Coal Field The Knobs are from mile 3.5 to 13.0. The area is a narrow Western Kentucky Coal Field belt of ridges and conical hills, many of which are capped by Jackson Purchase 38°N 38°N resistant siltstone and limestone. These hills are generally Kentucky River separated by broad, shale-floored valleys that are underlain Muldraughs Hill Esca rpment Palis ades by siltstone and silty shale. The Outer Bluegrass is from mile 13.0 to 42.0, and is 015 30 60 Miles characterized by rolling uplands underlain by interbedded limestone, shaly limestone, and shale. Esca rpment The Bluegrass Hills, underlain by impervious and easily 37°N Cumberla nd 37°N Dripping eroded shales, is defined by steep-sided hills and narrow Spr ings valleys that extend from mile 42.0 to 54.0. The rich soils and gently rolling terrain of the Inner Blue- grass are underlain by interbedded limestone, dolomite, and 90°W 89°W 88°W 87°W 86°W 85°W 84°W 83°W 82°W shale stretching from mile 54.0 to the end of the parkway. All the rocks underlying the parkway formed while Kentucky was Figure 1. Physiographic regions in Kentucky and location of the Bluegrass Parkway. beneath ancient shallow seas near the equator. Roadlog and Strip Maps Geologic units are shown approximately 0.5 mile on either side of the highway. 36 Mile marker Stream Figure 2 shows the symbols used on all the strip maps. The construction of these ! continuous strip maps was facilitated by the availability of detailed 1:24,000-scale U (up) Observation point Geologic fault (1 inch on the map equals 24,000 inches or 2,000 feet on the ground) geologic # D (down) data in digital form for the entire state; the digital data were converted from geologic quadrangle maps published by the U.S. Geological Survey in a joint project with the 18 Photo location Concealed geologic fault Kentucky Geological Survey from 1960 to 1978. The parkway's area is covered by 14 of these maps. Figure 3 shows the 7.5-minute quadrangles the parkway County line Lakes, ponds passes through. The roadlog covers the entire extent of the Bluegrass Parkway. All descriptions Railroad Mapped sinkholes of rock strata and geologic features are referenced to the highway mile markers that are located at 1-mile intervals along the shoulder of the highway. Mile-marker numbers Abandoned railroad Artificial fill are the same on both sides of the highway. Some of the roadcuts identified during a survey in the 1990's, particularly into shale, may now be revegetated. The descriptions U.S. or Ky. highway are nonetheless retained in order to identify what now lies beneath the overgrowth. Figure 2. Symbols used on the strip maps. 3 Stratigraphy Figure 3. Index of 7.5-minute A stratigraphic column (Fig. 4) is a generalized graphic representation of the rock layers geologic quadrangles maps present at the earth's surface. Figure 4 shows the rock units exposed along the Bluegrass covering the Bluegrass Parkway. Parkway, and indicates the units’ geologic ages. To make it easier to study and describe these stratigraphic units, geologists have subdivided them into groups, formations, members, and beds. A group is a major stratigraphic unit containing two or more formations. A formation is a unit of rock that has characteristic and distinctive rock types and layering that are mappable. A member is a subdivision of a formation that is distinguishable from adjacent parts of the formation. A bed is a rock unit lower in rank than a member, which has a distinctive lithology (for example, a coal bed). The abbreviations used on geologic maps to designate specific rock units are indicated in parentheses after the unit name in Figure 4. Geologic Time Scale Unit Description Geologic Time Scale Unit Description silt, clay, sand, and gravel limestone, dolomite, Present Alluvium (Qal) 440 million years ago Drakes Formation (Od) and shale 2 million years ago Terrace deposits (Qtf) sand Saluda Dolomite (Ods) shaly dolomite Nearly 300 million years of the geologic Bardstown Member (Odb), nodular-bedded record are absent in Kentucky, either from nondeposition or erosion, including Drakes Formation limestone and shale the Jurassic, Triassic, Permian, and part Rowland Member (Odr), greenish-gray, dolomitic of the Pennsylvanian Periods Drakes Formation limestone and shale 325 million years ago St. Louis Limestone (Msl) cherty limestone Ashlock Formation (Oa) limestone and shale nodular-bedded Salem Limestone (Ms) shaly limestone Grant Lake Limestone (Ogl) limestone and shale Harrodsburg Gilbert Member (Oag), crossbedded limestone micrograined limestone Limestone (Mhb) Ashlock Formation Calloway Creek interbedded limestone and Borden Formation (Mb) shale and siltstone Limestone (Occ) shale, limestone dominant Mississippian dolomitic siltstone Muldraugh Member (Mbm), interbedded limestone Clays Ferry Formation (Ocf) Borden Formation dolomitic limestone and shale Nancy Member (Mbn), greenish-gray shale Upper part of the crossbedded limestone Borden Formation Lexington Limestone (Olu) nodular-bedded limestone New Providence Member greenish-gray shale Millersburg Member (Olm) , nodular-bedded lime- (Mbnp), Borden Formation Lexington Limestone stone and shale New Albany Shale (Dna) carbonaceous shale Tanglewood Member No. 3 clastic limestone (Olt3), Lexington Limestone cross-bedded limestone 355 million years ago Sellersburg Limestone (Dsb) limestone Ordovician Sulphur Well Member (Ols), nodular-bedded limestone Lexington Limestone New Albany Shale and carbonaceous shale Tanglewood Member No. 2 nodular-bedded lime- Devonian Beechwood Limestone (Dnsb) limestone (Olt2), Lexington Limestone stone and shale 415 million years ago Louisville Limestone (Slv) dolomitic limestone Brannon Member (Olb), interbedded limestone Louisville Limestone, Lexington Limestone and shale Tanglewood Member No. 1 Waldron Shale, and limestone, shale, dolomite crossbedded limestone Laurel Dolomite (Slwl) (Olt1), Lexington Limestone Grier Limestone Member (Olg), Waldron Shale (Sw) clay shale nodular-bedded limestone Silurian Lexington Limestone Lower part of the crossbedded limestone Laurel Dolomite (Sl) dolomite Lexington Limestone (Ollr) nodular-bedded limestone 440 million years ago interbedded shale limestone, limestone and Osgood Formation (So) Tyrone Limestone and and dolomite shale, cherty shale 480 million years ago Oregon Formation (Oto) Brassfield Dolomite (Sb) dolomite dolomite Figure 4. Generalized stratigraphic column. Geology Along the Martha Layne Collins 4 Bluegrass Parkway: Miles 0.0–12.9 Mile 12.4: Louisville Limestone (Slv), Waldron Shale Mile 10.5, 10.7, 10.9: (Sw), Laurel Thin, laminar layers of Dolomite (Sl) greenish-gray New Providence shale. 5 733 Beech Fork RQ !# #(! Mile 10.5, 10.7, 10.9: New Providence # Member (Mbnp) of the Borden 1256 UV Dnsb !12 2 Formation. 6 # (!5#!11 #(! 3 Rolling # 10 Mile 2.3: Salem Limestone (Ms); shaly Fork ! Mile 3.2: Dolomitic siltstone and limestone of limestone. The Salem in most of Kentucky is !9 too shaly for commercial use. To the north in the Muldraugh Member (Mbm) of the Borden Indiana, the formation has less shale, so it is Formation. The sediments that form the # Muldraugh were deposited on a downslope UV1500 # quarried extensively there. RQ52 !8 Nelson (right to left), resulting in rolling beds. UV1048 Geologic Map Index Mile 3.5: Landscape changes to the east from RQ583 County an upland area of complex sinkholes and thick L32 Lebanon Junction # Mb residual soils underlain by soluble limestones to Younger Creek7 L33 Cravens Qala ! Hardin a belt of cone-shaped hills and narrow ridges County M31 Elizabethtown underlain by shales and siltstones. This change M32 Nelsonville marks the boundary between the Mississippian Mbm !6 Plateaus and the Knobs. Mhb Mile 7.2, 8.3: Greenish-gray (!4 shale of the New Providence # UV1046 !5 Member (Mbnp) of the UV1036 !3 (!#3 # !4 6 (!1#(!2 Borden Formation. !2# Ms Mile 0.0 ¨¦§65 UV1500 !1 !#0 Msl ± Buffalo Creek UV1031 Mile 11.4: Closeup of the New Mile 11.4: The New Albany Shale (Dna) Albany Shale (Dna) reveals was formed in low-oxygen (anaerobic) seas the fissile (almost paper-thin that preserved the organic matter in the layers) weathering and pyrite 4 sediments. In some areas, the black shales (yellow) formation. Photo by contain enough organic matter to burn, Mile 2.1: Brandon Nuttall, Kentucky Mile 5.3: Silty shale containing glauconite and are a potential source of oil.