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The Geology of Kentucky


Notes The Geology of Kentucky Kentucky Is Divided Into 6 Distinct Regions Bluegrass Region The Eastern Kentucky Coal Field The Knobs Region The Jackson Purchase or ... – PowerPoint PPT presentation

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Title: The Geology of Kentucky

The Geology of Kentucky
  • Notes

Kentucky Is Divided Into 6 Distinct Regions
  • Bluegrass Region
  • The Eastern Kentucky Coal Field
  • The Knobs Region
  • The Jackson Purchase or Mississippi Embayment
  • The Mississippian Plateau or Pennyroyal Region
  • The Western Kentucky Coal Field

(No Transcript)
Bluegrass Region
  • Characteristics of this region are gently rolling
    hills and rich, fertile soils, which are perfect
    for raising horses.
  • Layers of Ordovician aged limestone has been
    pushed up along the crest of a region called
    Cincinnati Arch.
  • The rolling hills are caused by the weathering of
    these thick beds of limestone which is
    characteristic of Kentucky.

Eastern Kentucky Coal Field
  • Is dominated by forested hills and deeply cut
    V-shaped valleys.
  • In southeastern Kentucky the highest elevation in
    the State, (before mining), was Black Mountain
    in Harlan County 4,145 feet.
  • Pine Mountain another important feature is best
    described as a 125-mile long ridge that extends
    from Jellico, Tennessee to Elkhorn City,
  • It is 3,200 feet high in Letcher County and is a
    direct result of the Pine Mountain Thrust Fault.
  • Appalachian Mountains built for the last time
    during end of Paleozoic era, block of Earth's
    crust was pushed up and over Southeastern

The Eastern Kentucky Coal Field
  • This region is formed from resistant
    Pennsylvanian-age sandstone and conglomerates in
    the form of an escarpment.
  • An escarpment is a ridge of gently tipped rock
    strata with long, gradual slope on one side and a
    steep scarp or cliff on the other.
  • The sandstones weather and are eroded along the
  • Results in cliffs, steep-walled gorges, rock
    shelters, waterfalls, natural bridges and arches,
    the most scenic areas in Kentucky.

Knobs Region
  • It is the region bordering the Bluegrass. It
    consists of hundreds of isolated, steep sloping,
    cone-shaped hills.
  • The hills are monadnocks or erosional remnants
    that were originally continuous with the
    Mississippian Plateau, but were separated by
    stream erosion.
  • Hills composed Mississippian-age Borden
    Formation shales, which are less resistant to
    erosion than the overlying limestones and

Jackson Purchase or Mississippi Embayment
  • Cretaceous and Tertiary Quaternary sediments
    occur at the surface.
  • These deposits are unconsolidated (not cemented)
    sediment instead of rock.
  • Are easily eroded, so, this part of Kentucky is
    flat with numerous lakes, ponds swamps.
  • Local relief is less than 100 feet, and the
    lowest spot in the State, at only 260 feet above
    sea level, is found here.

Jackson Purchase or Mississippi Embayment
  • Is underlain by faults of the New Madrid Fault
    Zone, the most active earthquake zone in the
    central United States.
  • The strongest earthquakes in the history of the
    United States occurred during the winter of
    1811-1812 were caused by movements along the New
    Madrid faults in Missouri and extreme western

Mississippian Plateau /Pennyroyal Region
  • Consists of limestone bedrock.
  • Characterized by tens of thousands of sink holes,
    sinking streams, streamless valleys, springs, and
  • Karst is used to define this type of terrain.
  • Region dominated by thick deposits of
    Mississippian-age limestones.
  • Terrain occurs because limestone bedrock in the
    eastern and southern parts are soluble (i.e. will
    dissolve) by waters moving through the ground.

  • This type of region contains some of the largest
    caves in the world.
  • The Mammoth Cave-Flint Ridge cave system is the
    longest cave in the world.
  • Carter Caves State Park, in Carter County, is
    very well known.
  • All of theses systems are formed in
    Mississippian-age limestones in the Mississippian
    Plateau Region.

Western Kentucky Coal Field
  • Smaller than eastern coal field.
  • It is the southern edge of a larger geologic
    feature called the Illinois Basin, includes
    Indiana Illinois coal fields.
  • An outcrop of Pennsylvanian age strata, defines
    the limits of the Western Kentucky Coal Fields.

Geology of Kentucky
  • Pennsylvanian aged strata occur in Kentucky in 2
    areas. Both shown as dark blue on the geologic
    maps we will use.
  • The Pennsylvanian age in Kentucky is composed of
    inter-bedded shale, sandstone, conglomerates, and
    coals. Thin limestone beds may also occur.
  • Coal is Kentucky's leading mineral commodity.
  • Because of the coal-bearing Pennsylvanian strata,
    we are among the top three states in the Nation
    in annual coal production (160 to 180 million
    tons annually).

  • All of Kentucky was covered by sediments of
    Pennsylvanian age at one time but, erosion has
    completely removed them from all areas but the
    coal fields now.
  • Pennsylvanian Period, often called the Coal Age,
    was a time of alternating land and sea.
  • When the sea was out, the low coastal plains were
    covered with luxuriant forests of seed ferns,
    ferns, scale trees, and dense vegetation.
  • During heavy rain, this dense vegetation fell to
    the forest floor to form (peat).
  • This peat later became (millions of years) the

  • When sea level rose, and it did periodically, it
    covered the peat created large inland muddy
  • During these times, (many thousands of years),
    many types of marine (sea-dwelling) invertebrates
    and vertebrates lived in the shallow seas that
    would become Kentucky.
  • Now Pennsylvanian marine fossils are found in
    Kentucky like Corals (Cnidarians), brachiopods,
    trilobites, snails (gastropods), clams
    (pelecypods), squid-like animals (cephalopods),
    crinoids (Echinoderms), fish teeth (Pisces), and
    microscopic animals.

  • Mississippian-age strata shown in light blue on
    the geologic map, are dominated by limestones,
    shales, and sandstones.
  • A thick sequence of limestone can contain
    numerous oil reservoirs beneath the surface.
  • Then the same limestone is quarried where it
    occurs at the surface. Reed quarry in western
    Kentucky, produces more limestone than any other
    quarry in the United States.

  • The limestone also contains large cave systems,
    including the Mammoth Cave-Flint Ridge cave
    system, and Carter Caves.
  • Mississippian rocks are exposed at the surface in
    the Mississippian Plateau (Pennyroyal) and occur
    below the surface in both of the coal fields.
  • Mississippian rocks are absent in the Blue Grass
    Region and in most of the Knobs.

  • During most of the Mississippian, Kentucky was
    covered by shallow tropical seas, but some very
    low lands may have been visible at times in
    central Kentucky.
  • Periodically, during the later part of the
    Mississippian, tidal deltas and low coastal
    plains covered large parts of Kentucky.

  • During alternating times the sea would come in
    and cover the region.
  • At this time thick limestones were created in
    these shallow seas.
  • Through the following millennia many caves were
    developed in these limestones.
  • So this area is now known as one of the world's
    most famous karst topographical areas.

Mississippian Fossils
  • Mississippian fossils in Kentucky are very
    similar to Pennsylvanian age fossils.
  • Also, some new life forms appeared like Crinoids
    blastoids forms of echinoderms.
  • When there was visible land in the form of low
    coastal plains, land plants animals thrived. So
    their fossils are present.
  • Since this area was a shallow sea we can also
    find amphibians. These were non-existent in the
    state until one was found in western Kentucky.

  • Devonian aged strata shown in red.
  • Devonian strata consists of limestones and
    dolostones and a thick deposit of dark gray to
    black shale.
  • The limestones are mined in the Louisville area
    and sometimes contain abundant fossils.
  • The thick, dark gray to black shales are the
    dominant Devonian strata in many areas of
  • The color of the shales comes from trapped
    organic material.

  • Late in the Devonian, organic muds were deposited
    in a shallow sea that covered most of the eastern
    United States.
  • When these organic-rich sediments were buried
    deeper beneath the surface, pressure and
    temperature converted some of the organic
    material in the rock to liquid and gaseous forms.
  • The liquid form is called oil.
  • The gaseous form is natural gas.

  • Eastern Kentucky has the largest gas field in the
    state and is estimated to contain billions of
    cubic feet of gas. (Big Sandy Gas Field).
  • The oil found in Kentucky started out in Devonian
    shales, but due to gravity migrated to other rock

Silurian Strata
  • The Ordovician rocks are surrounded by a ring of
    Silurian strata, shown in red.
  • These rocks out crop in the Knobs Region and
    consist mainly of limestones and dolostones.
  • In the Big Sinking-Irvine area, these rocks dip
    beneath the surface, and because they are very
    porous they form natural reservoirs for oil.
  • The Silurian rock strata pinches out to the south
    in Boyle, Casey, Lincoln, Montgomery Counties.

Silurian Strata
  • At this point, where Silurian strata are missing,
    Devonian tend to take their place and lie over
    Ordovician rocks.
  • This is called an unconformity because a large
    segment of geologic time is missing from the rock

Silurian Fossils
  • Silurian strata almost completely surrounds the
    Blue Grass Region in the form of the Knobs.
  • In the Blue Grass Silurian rock strata does not
    exist but, occur below the surface in other parts
    of Kentucky.
  • A shallow tropical sea covered Kentucky during
    most of the Silurian which allowed for the
    formation of thin beds of limestone.
  • All Silurian rocks found in Kentucky are marine
    (sea-dwelling) so all the fossils are the

Ordovician Strata
  • The Bluegrass Region of the State is composed of
    limestones and shales from the Ordovician Period,
    and are colored pink on the geologic map.
  • The Ordovician strata lies buried beneath the
  • The oldest rocks at the surface in Kentucky are
    limestones from the Late Ordovician Period
    (approximately 450 million years ago).

Ordovician Strata
  • These rock strata are exposed along the Palisades
    of the Kentucky River (for example, near Camp
    Nelson, in Jessamine County.
  • Ordovician limestones are quarried from Covington
    to Danville for use in construction.
  • Some of the limestones also produce natural
    spring water that is bottled and sold for
    drinking water.

Ordovician Strata
  • The city of Lexington was founded at McConnell
    Springs (pictured previously), which flows from
    Ordovician limestones.
  • The oldest rocks exposed at the surface in
    Kentucky are Ordovician and are exposed in the
    Blue Grass Region.
  • Rocks deposited during the first half of the
    Ordovician Period occur entirely below the
    surface throughout Kentucky.
  • Some of these deep rocks contain oil, so some oil
    wells have been drilled down to them.

Ordovician Strata
  • During most of the Ordovician, Kentucky was
    covered by shallow tropical seas.
  • Accordingly, the fossils found in Kentucky's
    Ordovician rocks are marine (sea-dwelling)
  • All common Ordovician fossils found in Kentucky
    are virtually the same as Pennsylvanian except
    sponges (Porifera) now makes an appearance.

Strata of Cretaceous Age
  • In western Kentucky, in Jackson Purchase Land
    Between the Lakes, older rocks are not overlain
    by Pennsylvanian rocks.
  • However, are overlain by Cretaceous (140 to 65
    million years ago) strata shown in green on the
    geologic map.
  • This relationship is another unconformity.

Strata of Cretaceous Age
  • Cretaceous strata on the map are the only areas
    in Kentucky where dinosaur bones might be found,
    although none yet.
  • The Cretaceous Period was the last period in the
    Age of Dinosaurs.
  • Much of the Cretaceous strata in Kentucky are
    unconsolidated sediments (i.e., they are not
    rocks yet).

Strata of Cretaceous Age
  • Sediment grains (e.g., sand, silt) have not been
    cemented together to form rock in many cases.
  • Some areas contain a low-grade form of coal
    called lignite (some peat still present), but it
    is not currently economic to mine.
  • The most common fossils are coalified tree limbs,
    but no dinosaurs yet.

Neogene and Paleogene (Tertiary) Age Strata
  • Paleogene and Neogene (65 to 1.6 million years
    ago) rocks sediments were deposited after the
    dinosaur extinction, during the Cenozoic Era.
    Shown in green.
  • Tertiary sediments in Kentucky include many
    deposits of ball clay, which can be used for
    ceramics and enameling.
  • KY is the 2nd largest producer of ball clay.
  • Common fossils are coalified limbs, logs, and
    stumps of lignite rank, few others

Neogene and Paleogene (Tertiary) Age Strata
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