PRELIMINARY SEQUENCE AND EVENT STRATIGRAPHIC CORRELATIONS WITHIN THE HELDERBERG GROUP (SILURIAN-DEVONIAN) BETWEEN NEW YORK AND THE CENTRAL APPALACHIAN BASIN James R. Ebert Damon K. Matteson SUNY College at Oneonta

New York: Appalachian Standard Succession Late nineteenth and early twentieth century studies Johnson and Murphy (1969) Helderberg Group Silurian-Devonian –Přídolí-Lochkovian –Predominantly limestone –Some shaly units

Primacy of New York in 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)

A New View of Helderberg Stratigraphy Rickard (1962) - migrating coeval facies Laporte (1969) – spectrum of ramp environments

Rickard’s (1962) migrating coeval facies influences correlations –in the CAB –between NY and the CAB Head (1969, 1972, 1974) Dorobek (1984), Dorobek and Read (1986) Rickard’s Stratigraphy and the Role of the Appalachian Standard Succession

Revised Helderberg Stratigraphy – New York Ebert and Matteson (2003a,b)

Rationale for Revised Stratigraphy Contacts are unconformable Clarifies placement of the S/D boundary based on conodonts

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?

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

Sequence 1: Manlius/Lower Keyser 

Sequence 2: Green Vedder/Big Mountain Shale 

First Transgressive Maximum and Siliciclastic-bearing Units 

Sequence 3: Dayville/U. Manlius/U. Keyser 

Sequence 4: Coeymans/New Creek First Icriodus woschmidti - Silurian/Devonian Boundary HCU is erosional throughout the basin 

Sequence 5: Kalkberg/Corriganville 

? An Undiscovered Unconformity in NY? 

Bald Hill K-bentonites Age of S/D Boundary Ma (Tucker, et. al. 1998) Basin-wide markers (Smith, Berkheiser and Way 1986)

Second Transgressive Maximum 

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 Přídolí 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!