Southeast Laurentia: Late Ordovician Tippicanoe Inundation and the Taconian Orogeny

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Southeast Laurentia Late Ordovician Tippecanoe
Inundation and the Taconian Orogeny
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Paleogeography during Late Ordovician Time (460
m.y.a.)
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Paleoenvironment and Paleoclimate

• Present east-central U.S. was located 20-25 S
  latitude
• The study area was located within a subtropical
  trade-wind belt in which the prevailing
  paleowinds approached Laurentia from the
  east-southeast
• Sedimentation affected by the frequency and
  magnitude of storms and upwelling from the Sebree
  Trough

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Late Ordovician paleogeography and regional
current directions
Brachiopod shells
Bryozoan twigs
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Epeiric Platform Sedimentation
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• Extensive areas of negligible topography
• Low orders of slopes (lt1 ft/mile)
• Extreme shallowness (lt75-10 m) of water
• Restrictive circulation
• Quiet, low energy environments most of the time
• Dominant storm sedimentation process would have
  been storms

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Late Ordovician Paleoenvironments and Tectonics
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Galena-Trenton-Lexington Shelves

• Sites of shallow, epeiric sedimentation
• Reflect carbonate buildup on reactivated basement
  structures
• These faults caused the platforms to be upthrown,
  enhancing carbonate sedimentation

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Tanglewood Shoal

• Far-field tectonic forces resulted in the growth
  of a high-energy shoal complex on horst blocks in
  central Kentucky
• The shoal produced high energy calcarenites and
  calcirudites
• Similar to the Bahama Banks of today
• Sediments influenced by storms and wind-wave
  action

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Tanglewood Buildup Relative to Basement Structures
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  Environmental reconstruction across an
approximately 70-km expanse of the Tanglewood
buildup showing probable structural control on
buildup development
W
E
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Bahama Banks of Today
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Sulphur Well Member

• Tempestite sedimentation
• Sheet of reworked shells
• Parallel to low angle laminae
• Wave-ripple laminae
• Mud cap

Generalized trends in vertical and lateral
variation of ideal tempestite
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A typical Sulphur Well deposit from the
lenticular calcarenite facies as seen in the
field, showing irregular to lenticular bedding of
limestones separated by shale partings.
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Mud cap (missing)
Wave-ripple laminae
Parallel to low angle laminae
Up
Sheet of reworked shells

  Cross-sectional view of a tempestite. Basal
part contains compacted rip-up clasts of shale.
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Sebree Trough
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Sebree Trough

• Narrow, deep channel that drew in cold, anoxic
  waters from the Ouachita Sea causing corrosion
  and sediment starvation in the trough and
  extensive carbonate production on the flanks due
  to upwelling onto structural highs
• Upwelling increased sedimentation to due high
  abundances of fauna receiving nutrients from the
  trough
• Aligned with preexisting basement structures
• Connected the Ouachita Sea in southern Laurentia
  with the shallow platform regions to the north

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Clays Ferry/Point Pleasant/Kope Formations

• Abrupt regional deepening of the shelves due to
  subsidence accompanying Taconic relaxation
  allowed finer, deeper water carbonates and muds
  that covered the entire area in later Ordovician
  (late Edenian) time

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Stratigraphic Relationshi
Tanglewood
Sulphur Well
Clays Ferry, Kope, Point Pleasant
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CF
SW
CF Tongue
T
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Conclusions

• Trough-platform development was the result of
  far-field tectonic responses and epeiric sea
  inundation
• The platforms resided in subtropical environments
  in which sediment dispersion was influenced
  through regional/local tectonics, depth, storms,
  and upwelling
• Rapid deepening of the southeastern Laurentian
  shelf in late Edenian time caused fine-grained
  limestones and shales to blanket the platforms
  and fill up the trough which smoothed out
  topography
• Resultant Taconic relaxation caused widespread
  epeiric sea sedimentation once again
• These interpretations can assist in the
  understanding additional carbonate ramps in
  tectonically active foreland basins