PRELIMINARY%20SEQUENCE%20AND%20EVENT%20STRATIGRAPHIC%20CORRELATIONS%20WITHIN%20THE%20HELDERBERG%20GROUP%20(SILURIAN-DEVONIAN)%20BETWEEN%20NEW%20YORK%20AND%20THE%20CENTRAL%20APPALACHIAN%20BASIN

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PRELIMINARY SEQUENCE AND EVENT STRATIGRAPHIC
CORRELATIONS WITHIN THE HELDERBERG GROUP
(SILURIAN-DEVONIAN) BETWEENNEW YORK AND THE
CENTRAL APPALACHIAN BASIN

• James R. Ebert
• Damon K. Matteson
• SUNY College at Oneonta

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New York Appalachian Standard Succession

• Late nineteenth and early twentieth century
  studies
• Johnson and Murphy (1969)
• Helderberg Group
• Silurian-Devonian
• Prídolí-Lochkovian
• Predominantly limestone
• Some shaly units

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Primacy of New Yorkin the Early Literature

• Early Twentieth Century Stratigraphy and
  Correlations to New York based on
• General lithologic similarities
• Faunal similarities
• Names from New York applied from New Jersey to
  Virginia the Central Appalachian Basin (CAB)

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A New View of Helderberg Stratigraphy

• Rickard (1962) - migrating coeval facies
• Laporte (1969) spectrum of ramp environments

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Rickards Stratigraphy and the Role of the
Appalachian Standard Succession

• Rickards (1962) migrating coeval facies
  influences correlations
• in the CAB
• between NY and the CAB
• Head (1969, 1972, 1974)
• Dorobek (1984), Dorobek and Read (1986)

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Revised Helderberg Stratigraphy New YorkEbert
and Matteson (2003a,b)
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Rationale for Revised Stratigraphy

• Contacts are unconformable
• Clarifies placement of the S/D boundary based on
  conodonts

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New Questions in a Classic Setting

• How does the presence of unconformities in NY
  affect correlations within the CAB and between NY
  and the CAB?
• Are these unconformities widespread? Can they be
  recognized in the CAB and used as a framework for
  correlation?
• What are the relative roles of eustatic and
  tectonic processes in producing the
  unconformities?
• Can basin-wide revision of Helderberg
  stratigraphy provide new insights on global sea
  level change around the S/D boundary?

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Framework for Stratigraphic Correlations

• Working model of early correlations
• Examination of contacts
• Evidence of erosion
• Evidence of sediment starvation
• Biostratigraphic data FAD Icriodus woschmidti
• Unique faunal occurrences - Scyphocrinites
• Recognition of events and marker beds
• Distinctive facies/lithologies - two
• Episodes of siliciclastic influx
• Trangressive maxima - two
• Bald Hill K-bentonites

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Sequence 1 Manlius/Lower Keyser
?
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Sequence 2Green Vedder/Big Mountain Shale
?
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First Transgressive Maximum and
Siliciclastic-bearing Units
?
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Sequence 3 Dayville/U. Manlius/U. Keyser
?
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Sequence 4 Coeymans/New Creek
?
First Icriodus woschmidti - Silurian/Devonian
Boundary HCU is erosional throughout the basin
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Sequence 5 Kalkberg/Corriganville
?
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An Undiscovered Unconformity in NY?
?
?
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Bald Hill K-bentonites
Basin-wide markers (Smith, Berkheiser and Way
1986)
Age of S/D Boundary - 418 Ma (Tucker, et. al.
1998)
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Second Transgressive Maximum
?
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Conclusions

• NY unconformities can be traced into CAB
• Most unconformities in NY are erosional
• Most in the CAB are marked by sediment starvation
• Minelot Falls/Tonoloway-Keyser Unconformity and
  Howe Cave Unconformity are erosional throughout
  basin
• A Prídolí transgressive maximum is now recognized
• Sequence and event stratigraphic correlations
  between NY and the CAB are similar to those
  proposed in the early twentieth century
• Correlations are preliminary much more work
  needs to be done!

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