trilobite Isotelus gigas
Trenton Black River Project
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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)

FIGURES AND APPENDICIES:

Appendix 3 Figure Captions.

(Click on thumbnail image for an expanded view.)

Dolomite textures in the Trenton and Black River carbonate rocks of the Appalachian basin.
(Click on thumbnail image for an expanded view.)

Figure A3-1. Type I planar-p dolomite.
All of the illustrated dolomites are matrix-selective and occur in subtidal carbonate facies. These dolomites are not associated with fractures, faults, or rock alteration by hydrothermal basinal brine. They probably formed through burial dolomitization at a local scale via compaction-driven fluid flow.
FIGURE A3-1 A. Planar-p dolomite replacing bioturbated, fossiliferous pelmicrite. A. Planar-p dolomite replacing bioturbated, fossiliferous pelmicrite. The dolomite crystals are polymodal, ranging in size from 40 to 200 m in diameter. The crystals have planar boundaries and are porphyrotopic, floating in the limestone matrix they replaced. Most dolomite crystals are cloudy due to inclusions, and some indistinct zoning is evident in most crystals. The matrix is peloidal micrite that we interpret as marine cement. Note the incipient solution seams, outlined by micron-size pyrite crystals, which impart a somewhat lenticular habit to the limestone. Some of the planar-p dolomite is partially dissolved along these seams indicating the dolomite formed before chemical compaction. Black River Formation, Power Oil Company #9634 well (Sandhill well), Wood County, WV, 9906 ft.
FIGURE A3-1 B. Finely to medium crystalline, polymodal, planar-p dolomite replacing decimicron-size neomorphic calcite crystals. B. Finely to medium crystalline, polymodal, planar-p dolomite replacing decimicron-size neomorphic calcite crystals. The dolomite crystals are cloudy due to abundant inclusions, and predate fractures in the rock. . Black River Formation, Power Oil Company #9634 well (Sandhill well), Wood County, WV, 10,162 ft.
FIGURE A3-1 C. Polymodal, planar-p dolomite replacing matrix in a sparse biopelmicrite in the Black River Formation. Outcrop sample from Union Furnace, Huntingdon County, PA. C. Polymodal, planar-p dolomite replacing matrix in a sparse biopelmicrite in the Black River Formation. Outcrop sample from Union Furnace, Huntingdon County, PA.

Figure A3-2. Type I planar-p and planar-e dolomite.

All of the illustrated dolomites are matrix-selective and occur in subtidal carbonate facies. These dolomites are not associated with fractures, faults, or rock alteration by hydrothermal basinal brine. They probably formed through burial dolomitization at a local scale via compaction-driven fluid flow.

FIGURE A3-2 A. Polymodal planar-e dolomite replacing bioturbated, fossiliferous pelmicrite adjacent to stylolites. A. Polymodal planar-e dolomite replacing bioturbated, fossiliferous pelmicrite adjacent to stylolites. The dolomite crystals are 2 to 100 m in diameter. Note the abundant inclusions in the dolomite crystals. This planar-e dolomite resembles the planar-p textures shown in the last three photomicrographs above, but the euhedral dolomite now forms a mosaic that almost entirely replaces limestone matrix. Note, however, the planar-p dolomite replacing limestone away from the solution seam. Chemical compaction might have concentrated the planar dolomite crystals along the solution seams. Black River Formation, Power Oil Company #9634 well (Sandhill well), Wood County, WV, 10,162 ft.
FIGURE A3-2 B. Higher magnification view of the planar-e dolomite in Figure A3-2 A. B. Higher magnification view of the planar-e dolomite in Figure A3-2 A. Note that some of the dolomite floats within the insoluble material of the seam, and is partially dissolved along it too. Dolomitization predates chemical compaction.
FIGURE A3-2 C. Laminae of brown planar-e dolomite interbedded with thicker beds of skeletal limestone (wackestone and packstone) in the Black River Formation exposed at the Union Furnace outcrop in central PA. C. Laminae of brown planar-e dolomite interbedded with thicker beds of skeletal limestone (wackestone and packstone) in the Black River Formation exposed at the Union Furnace outcrop in central PA.
FIGURE A3-2 D. Thin section photomicrograph of matrix-selective, polymodal planar-e dolomite replacing micrite in one of the brown laminae shown previously in Figure A3-2C above. D. Thin section photomicrograph of matrix-selective, polymodal planar-e dolomite replacing micrite in one of the brown laminae shown previously in Figure A3-2C above.
Figure A3-3. Type I planar-e and planar-s dolomites.
FIGURE A3-3 A. Thin section photomicrograph of decimicron- to centimicron-size polymodal, planar-e to planar-s dolomite replacing peloidal calcite cement in a grainstone. A. Thin section photomicrograph of decimicron- to centimicron-size polymodal, planar-e to planar-s dolomite replacing peloidal calcite cement in a grainstone. Trenton Formation, Melben Oil Company Emma McKnight #1 well, Mercer County, PA, 6845.2 ft. This dolomite is matrix-selective and occurs in a subtidal carbonate ramp facies. This dolomite is not associated with fractures, faults, or rock alteration by hydrothermal basinal brine.
  B. Micron- and decimicron-size polymodal planar-e to planar-s dolomite in laminated peritidal carbonates. 1 and 2 are stromatolites exposed in the basal Black River Formation at Union Furnace in Huntingdon County, PA in which the dolomite replaced the original limestone. 3 and 4 show respective core and backscattered electron SEM photographs of probable peritidal stromatolites in the Ohio #2854 well, Delaware County, Ohio (Trenton Formation, 2901 ft.). These planar dolomites probably formed through reflux and/or mixing zone dolomitization.
FIGURE A3-3 B-1. Micron- and decimicron-size polymodal planar-e to planar-s dolomite in laminated peritidal carbonates. 1. FIGURE A3-3 B-2. Stromatolites. Micron- and decimicron-size polymodal planar-e to planar-s dolomite in laminated peritidal carbonates. 2. FIGURE A3-3 B-3. Core and backscattered electron SEM photographs of probable peritidal stromatolites in the Ohio #2854 well, Delaware County, Ohio (Trenton Formation, 2901 ft.). 3. FIGURE A3-3 B-4. Core and backscattered electron SEM photographs of probable peritidal stromatolites in the Ohio #2854 well, Delaware County, Ohio (Trenton Formation, 2901 ft.). 4.
FIGURE A3-3 C. A hydrothermal dolomitization front in the Black River Formation. C. A hydrothermal dolomitization front in the Black River Formation. Polymodal decimicron-size planar-e dolomite partially replaces pelmicrite. Intercrystalline porosity in the dolomite is filled by bitumen. This planar dolomite fabric occurs in a zone near the top of a faulted and fractured subsurface interval altered by hydrothermal dolomitization. The dolomite formed through rock alteration by saline basinal brines (the dolomite 18O = -9 permil, Smith, 2005, personal communication). Black River Formation, Dominion Exploration and Production Company Bayles #1 well, Bradford County, PA, 12,425 ft.
FIGURE A3-3 D. Core and backscattered electron SEM photographs of probable peritidal stromatolites in the Ohio #2854 well, Delaware County, Ohio (Trenton Formation, 2901 ft.) D. Polymodal decimicron- and centimicron-size planar-e to planar-s dolomite completely replacing pelmicrite. The apparent intercrystalline porosity is filled with bitumen. This planar fabric is associated with fracturing, faulting, and hydrothermal dolomitization. Black River Formation, Dominion Exploration and Production Company Bayles #1 well, Bradford County, PA, 12,425 ft.
FIGURE A3-3 E. Hydrothermal decimicron- to centimicron-size polymodal planar-s dolomite. E. Hydrothermal decimicron- to centimicron-size polymodal planar-s dolomite. Bitumen fills intercrystalline void space. Also note the cutting composed of centimicron-size planar-s dolomite in the upper left corner of the photograph. Black River Formation, Dominion Exploration and Production Company Bayles #1 well, Bradford County, PA, 12,425 ft.
Figure A3-4. Type I planar-c dolomite.
FIGURE A3-4 A. SEM photomicrograph of polymodal (60 m to 300 m crystals) planar-c dolomite lining and partially filling a small vug in the Trenton Limestone. Prudential 1A well, Marion County, OH, 2013.5 ft. A. SEM photomicrograph of polymodal (60 m to 300 m crystals) planar-c dolomite lining and partially filling a small vug in the Trenton Limestone. Prudential 1A well, Marion County, OH, 2013.5 ft.
FIGURE A3-B. Higher magnification view of planar-c dolomite shown in Figure A3-4A. This dolomite is in the upper right corner of the vug. The cross on the crystal just right of the center of the SEM photo shows the spot of the EDS analysis presented next in Figure A3-4C. B. Higher magnification view of planar-c dolomite shown in Figure A3-4A. This dolomite is in the upper right corner of the vug. The cross on the crystal just right of the center of the SEM photo shows the spot of the EDS analysis presented next in Figure A3-4C.
FIGURE A3-C. EDS spectra of the planar-c dolomite shown in Figure A3-4B. The dolomite is not stoichiometric, having an excess of Ca (Ca = 17.77%, Mg = 11.50 %), and it is ferroan (Fe = 3.53 wt.%), indicating formation from saline basinal fluid (see Allan and Wiggins, 1993). C. EDS spectra of the planar-c dolomite shown in Figure A3-4B. The dolomite is not stoichiometric, having an excess of Ca (Ca = 17.77%, Mg = 11.50 %), and it is ferroan (Fe = 3.53 wt.%), indicating formation from saline basinal fluid (see Allan and Wiggins, 1993).
FIGURE A3-4 D. SEM photomicrograph of polymodal decimicron- to centimicron-size planar-c dolomite lining a medium vug in the Trenton Formation. The Fe concentration of this dolomite is 8.98 wt.%, indicating saline basinal brine as the dolomitizing fluid. Prudential 1A well, Marion County, OH, 1855 ft. D. SEM photomicrograph of polymodal decimicron- to centimicron-size planar-c dolomite lining a medium vug in the Trenton Formation. The Fe concentration of this dolomite is 8.98 wt.%, indicating saline basinal brine as the dolomitizing fluid. Prudential 1A well, Marion County, OH, 1855 ft.
Figure A3-5. Type II planar-s to nonplanar (transitional) dolomites.
FIGURE A3-5 A. Planar-s to nonplanar (transitional) dolomite replacing a peloidal or oolitic limestone. A. Planar-s to nonplanar (transitional) dolomite replacing a peloidal or oolitic limestone. Compare the ghosts of the peloids or ooids in this dolomite with the peloids (micritized ooids and grains) in the limestone cutting from the same sample shown in Figure A3-5B. Black River Formation, Dominion Exploration and Production Company Bayles #1 well, Bradford County, PA, 12,425 ft.
FIGURE A3-5 B. Peloidal limestone (pelsparite) cutting from 12,425 ft. in the Bayles #1 well, Bradford County, PA. B. Peloidal limestone (pelsparite) cutting from 12,425 ft. in the Bayles #1 well, Bradford County, PA. The peloids, possibly micritized ooids, are cemented by calcite spar. Compare with the dolomite in Figure A3-5A.
FIGURE A3-5 C. Polymodal decimicron- to centimicron-size planar-s to nonplanar-a (transitional) dolomite in the Black River Formation, CNR Gray #1 well, Steuben County, NY, 7793 ft. C. Polymodal decimicron- to centimicron-size planar-s to nonplanar-a (transitional) dolomite in the Black River Formation, CNR Gray #1 well, Steuben County, NY, 7793 ft.
FIGURE A3-5 D. Polymodal decimicron- to centimicron-size planar-s to nonplanar-a (transitional) dolomite in the Black River Formation, CNR Gray #1 well, Steuben County, NY, 7793 ft. D. Polymodal decimicron- to centimicron-size planar-s to nonplanar-a (transitional) dolomite in the Black River Formation, CNR Gray #1 well, Steuben County, NY, 7793 ft.
Figure A3-6. Type II nonplanar-a dolomite textures.

All of the illustrated dolostones show fabric obliteration, and are fault and fracture-related, hydrothermal, nonplanar dolomites.

FIGURE A3-6 A. Unimodal, medium crystalline nonplanar-a dolomite (Black River Formation, Columbia Natural Resources Gray 24468 well, Steuben County, NY, 7796 ft.) A. Unimodal, medium crystalline nonplanar-a dolomite (Black River Formation, Columbia Natural Resources Gray 24468 well, Steuben County, NY, 7796 ft.).
FIGURE A3-6 B. Higher magnification view of nonplanar-a dolomite shown in Figure A3-6A. Note the tightly interlocked crystal fabric and consequent lack of intercrystalline pore space. B. Higher magnification view of nonplanar-a dolomite shown in Figure A3-6A. Note the tightly interlocked crystal fabric and consequent lack of intercrystalline pore space.
FIGURE A3-6 C. Backscattered SEM photomicrograph of nonplanar-a dolomite texture. C. Backscattered SEM photomicrograph of nonplanar-a dolomite texture. This sample is from the same well core as those shown in Figure A3-6A and B, but is from a slightly deeper interval at 7799.9 ft. The predominant medium gray is nonplanar-a dolomite, which is not stoichiometric (Ca = 23.54 wt.%, Mg = 11.87 wt.%) and is ferroan (Fe = 2.17 wt.%). The white material is a chloride (Cl = 20.35 wt.%) with notable sodium and potassium (Na = 7.10 wt.%, K = 6.30 wt.%). The material does not appear in thin sections, probably due to high solubility in water and loss during preparation of the slide. It does appear as a dark, reddish, compact and granular mass in the hand samples of the core. The material might be an admixture of halite and sylvite, or a precipitate in the core that formed through evaporation of a residual K-Na-Cl brine.
FIGURE A3-6 D. EDS spectra of the nonplanar-a dolomite in Figure A3-6C. D. EDS spectra of the nonplanar-a dolomite in Figure A3-6C.
Figure A3-7. Nonplanar (saddle) dolomite textures.
FIGURE A3-7 A. Nonplanar (saddle) dolomite cement partially filling a small vug in the Trenton Formation (OH 3479, Anderson well, Hancock Co., OH, 1337.8 ft.). A. Nonplanar (saddle) dolomite cement partially filling a small vug in the Trenton Formation (OH 3479, Anderson well, Hancock Co., OH, 1337.8 ft.). Note the diagnostic spearhead crystal shape, mottled salt and pepper appearance (due to inclusions), and sweeping extinction under crossed polars.
FIGURE A3-7 B. NBackscattered SEM photomicrograph of nonplanar (saddle) dolomite cement filling a small vug in the Trenton Formation. B. Backscattered SEM photomicrograph of nonplanar (saddle) dolomite cement filling a small vug in the Trenton Formation. This is the same sample shown in Figure A3-7A. The saddle dolomite crystals exhibit the same spearhead shape observed in thin section, and curved crystal faces are easier to see in this three dimensional view.
FIGURE A3-7 C. High magnification SEM view of nonplanar (saddle) dolomite filling a small vug in the same Ohio sample shown in Figure A3-7A and B. C. High magnification SEM view of nonplanar (saddle) dolomite filling a small vug in the same Ohio sample shown in Figure A3-7A and B. The cross on the crystal in the upper center of the photograph is the spot of the EDS analysis shown in Figure A3-7D. The saddle dolomite is not stoichiometric, with calcium excess (Ca = 17.05 wt.%, Mg = 12.68 wt.%), and it is nonferroan (Fe = 1.01 wt.%).
FIGURE A3-7 D. EDS spectra of nonplanar (saddle) dolomite shown in Figure A3-7C. D. EDS spectra of nonplanar (saddle) dolomite shown in Figure A3-7C.
FIGURE A3-7 E. Pore-filling nonplanar (saddle) dolomite with oil staining in the Trenton Limestone. Note the curved crystal faces. (OH 2549 core, Wood Co., OH, 1168.25 ft.). E. Pore-filling nonplanar (saddle) dolomite with oil staining in the Trenton Limestone. Note the curved crystal faces. (OH 2549 core, Wood Co., OH, 1168.25 ft.).
FIGURE A3-7 F. Nonplanar (saddle) dolomite lining a large vug in the Black River Formation. (Whiteman #1 well, Steuben Co., NY, 9531 ft.). F. Nonplanar (saddle) dolomite lining a large vug in the Black River Formation. (Whiteman #1 well, Steuben Co., NY, 9531 ft.).
FIGURE A3-7 G. Backscattered SEM view of the same sample shown in Figure A3-7F. Nonplanar (saddle) dolomite cement lines a large vug. Note the bitumen coatings on some of the dolomite. G. Backscattered SEM view of the same sample shown in Figure A3-7F. Nonplanar (saddle) dolomite cement lines a large vug. Note the bitumen coatings on some of the dolomite.
FIGURE A3-7 H. Nonplanar (saddle) dolomite cement completely fills a small vug in the same sample shown in Figures A3-7F and G. H. Nonplanar (saddle) dolomite cement completely fills a small vug in the same sample shown in Figures A3-7F and G.
Figure A3-8. Limestone replacement textures.

Mimetic and non-mimetic replacement of original crinoid bioclasts (originally composed of high-magnesium calcite) by planar-s to nonplanar-a dolomite. All examples from the Trenton Formation, OH 3479, Anderson well, Hancock Co., OH, 1337.8 ft.

FIGURE A3-8 A. Core sample of vuggy crinoid/bryozoan dolograinstone with mimetically replaced crinoid visible near the top center of the photograph. A. Core sample of vuggy crinoid/bryozoan dolograinstone with mimetically replaced crinoid visible near the top center of the photograph. A fabric selective intraparticle pore occurs in the crinoid's central lumen. Vague circular rinds and halos around some mesopores suggest they are non-mimetically replaced allochems.
FIGURE A3-8 B. Thin section photomicrograph of a mimetically replaced crinoid in the same sample shown in (1). B. Thin section photomicrograph of a mimetically replaced crinoid in the same sample shown in (1). Planar-s to nonplanar-a dolomite replaced the original crinoid grain. Note chert replacing the dolomitized crinoid in the upper left corner of the fossil.
Figure A3-9. Hybrid dolomite fabrics.
FIGURE A3-9 A. A small pocket of polymodal, decimicron-sized planar-s dolomite surrounded by coarser (centimicron- to millimeter-sized) planar and nonplanar dolomite. A. A small pocket of polymodal, decimicron-sized planar-s dolomite surrounded by coarser (centimicron- to millimeter-sized) planar and nonplanar dolomite. Centimicron-sized planar-s to nonplanar-a dolomite surrounds the finer crystalline planar-s dolomite. Centimicron-sized planar-e and centimicron- to millimeter-sized saddle dolomite both partially fill large mesopores and medium vugs. Nonplanar (saddle) dolomite also mimically replaces a large echinoderm fragment (lower left) in this former skeletal grainstone. Trenton Formation, Strayer #1 well, (OH 3478 core), Allen County, OH, 1211.25 ft.
FIGURE A3-9 B. Higher magnification view of the pocket of decimicron-sized planar-s dolomite shown in Figure A3-9A. B. Higher magnification view of the pocket of decimicron-sized planar-s dolomite shown in Figure A3-9A.
FIGURE A3-9 C. Contact between decimicron-sized planar-s dolomite (right) and centimicron-sized nonplanar (saddle) dolomite (left). C. Contact between decimicron-sized planar-s dolomite (right) and centimicron-sized nonplanar (saddle) dolomite (left). Trenton Formation, Strayer #1 well, (OH 3478 core), Allen County, OH, 1211.25 ft.
FIGURE A3-9 D. Same thin section photomicrograph as Figure A3-9C, but with white index card inserted beneath the thin section. D. Same thin section photomicrograph as Figure A3-9C, but with white index card inserted beneath the thin section. Note the ghosts of the decimicron-sized planar-s dolomite (identical to the same dolomite texture on the right) within the saddle dolomite. This suggests that the saddle dolomite is a neomorphic recrystallization product of the earlier diagenetic planar-s dolomite.
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