trilobite Isotelus gigas
Trenton Black River Project
Petrography
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PETROGRAPHY OF THE TRENTON AND BLACK RIVER GROUP CARBONATE ROCKS IN THE APPALACHIAN BASIN

Introduction | Methods | Constituents | Microfacies and Depositional Environments | Diagenesis | Dolomite Textures, Diagenesis, and Porosity |
References | Text Figures | Appendix I [Skeletal (PDF) - Nonskeletal (PDF)] | Appendix II (PDF) |
Appendix III-Figure Captions | Appendix IV-Figure Captions | Appendix V-Figure Captions |
Table 1 - TBR Core and Outcrop Samples (PDF)

MICROFACIES AND DEPOSITIONAL ENVIRONMENTS

All of the principal carbonate rock types occur in the Trenton and Black River Formations of the Appalachian basin. The depositional texture of the original limestones correlate directly to the sedimentary environments of the carbonate ramp on which the various rock types accumulated. Tidal flat and lagoonal limestones mostly consist of mudstone and wackestone, with thin packstone/grainstone deposits that collected within tidal channels. These rocks were deposited in peritidal settings as low-energy, shallowing-upward successions and thick lagoonal successions. Although less common, some grainstones and packstones accumulated as high-energy shallowing upward successions deposited as beach carbonates in the peritidal settings too.

Subtidal deposits include boundstones, grainstones, packstones, wackestones, and mudstones deposited in both shallow and deeper carbonate ramp setting. Rocks that formed above wave base on the shallow ramp include hardground-bounded, amalgamated grainstone, and grainstone-capped high energy shoaling successions. Skeletal packstone/wackestone - mudstone successions, also bound by well-developed hardgrounds, formed on the deeper ramp below fair-weather wavebase. Graded carbonate beds - tempestites and turbidites - accumulated in slope and basin margin environments. These consist of upward-fining grainstone/packstone and wackestone/mudstone couplets separated by siliciclastic shales. The carbonate materials were introduced from the carbonate ramp, while the shales came from the Taconic highlands and volcanic arc along the southeast margin of Laurentia (Pope and Steffens, 2003). to top