28 Paleozoic Events and Processes: Sedimentary Geology, Paleontology, and Geochemistry

The focus of this session is short- to long-term geologic, paleobiologic, and geochemical events and processes, recorded in Paleozoic sedimentary rocks.

Monday, 23 March 2026
3:25 PM - 5:30 PM
CCC, Room 27

Stratigraphy of the Port Jervis Formation Interval in Southeastern New York and Northwestern New Jersey

Paper number: 28-2
Program: Technical Sessions
Time: 3:50 PM – 4:10 PM

Authors

Abstract

The boundary between the Helderberg and Tristates groups within the Lower Devonian of NYS is marked nearly everywhere by a major unconformity located at the Tippecanoe and Sauk megasequence boundary. This stratigraphic contact has long been regarded as a possible location of the boundary between the Lochkovian and Pragian stages of the Early Devonian within this region. Determination of the exact placement of this stage level boundary has been difficult within the standard NY Devonian succession due to the unconformable nature of this stratigraphic contact along with a paucity of useful biostratigraphic taxa. Futhermore, the nature and timing of the transition between the Helderberg and Tristates Evolutionary-Ecological subunits has also been poorly understood for the same reasons. It has been hypothesized that the strata of this interval in southeastern NY/northwestern NJ may show continuous deposition across the Helderberg-Tristates group boundary, but few investigations have taken place in this region to date.

Recent study of strata across the Helderberg/Tristates boundary in SE-NY/NW-NJ has revealed the following findings: 1) there is no evidence for a major unconformity in SE-NY/NW-NJ through this stratigraphic interval; 2) a key index fossil for this interval is the brachiopod Nanothyris subglobosa, occurring across carbonate and siliciclastic facies and seemingly restricted to uppermost Helderberg Group strata; 3) carbonate facies in slightly deeper-water settings are preserved near Port Jervis in SE-NY/NW-NJ while shallower-water siliciclastic facies dominate to the north near Kingston, NY; 4) the Port Jervis Formation of SE-NY/NW-NJ is lithologically more similar to strata of the Helderberg Group below than to strata of the Tristates Group above; 5) the Port Jervis interval of SE-NY/NW-NJ is likely equivalent to strata heretofore assigned to the uppermost Port Ewen Formation in the Kingston, NY, region to the north and the Central Valley Sandstone in the Skunnemunk Outlier to the northeast; 6) conodonts have been recovered from Port Jervis strata in NW-NJ that are of Pragian age; 7) a more precise identification of the location of the major unconformity within these strata as occurring at the base of the Glenerie Formation near Kingston, NY; 8) uppermost Helderberg Gp. strata are missing north of Kingston, NY.

 

Geological Society of America Abstracts with Programs. Vol. 58, No. 2

doi: 10.1130/abs/2026NE-411341

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