Bass Islands Dolomite Keyser Limestone (lower) and Salina Group Keyser Limestone (lower) and Salina Group Big Mountain Shale through Tonoloway Limestone Bass Islands Dolomite Bass Islands Dolomite Bass Islands Dolomite Bass Islands Dolomite Bass Islands Dolomite and Camillus Shale Bass Islands Dolomite and Camillus Shale Bass Islands Dolomite and Camillus Shale Bass Islands Dolomite and Camillus Shale Bass Islands Dolomite through Salina Group Bass Islands Dolomite and Salina Group Bass Islands Dolomite and Salina Group Bass Islands Dolomite and Salina Group Bass Islands Dolomite through Tonoloway Limestone Bass Islands Dolomite through Tonoloway Limestone Bass Islands Dolomite and Camillus Shale Keyser Formation Keyser Formation and Camillus Shale Keyser Limestone (lower) through Wills Creek Formation Camillus Shale Camillus Shale Camillus Shale Camillus Shale Camillus Shale Camillus Shale Camillus Shale Camillus Shale Camillus Shale Camillus Shale Camillus Shale Camillus Shale Camillus Shale Camillus Shale Camillus Shale Camillus Shale Camillus Shale Camillus Shale Syracuse Formation Syracuse Formation Syracuse Formation Syracuse Formation Syracuse Formation Syracuse Formation Syracuse Formation Syracuse Formation Syracuse Formation Syracuse Formation Vernon Formation Vernon Formation Vernon Formation Vernon Formation Vernon Formation Vernon Formation Vernon Formation Vernon Formation Vernon Formation Vernon Formation Vernon Formation Vernon Formation Vernon Formation Vernon Formation Vernon Formation Vernon Formation Vernon Formation and Wills Creek Formation Vernon Formation and Lockport Dolomite Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group Salina Group and Wills Creek Formation Salina Group and Wills Creek Formation Salina Group and Wills Creek Formation Salina Group and Wills Creek Formation Salina Group and McKenzie Limestone Salina Group through McKenzie Limestone Salina Group through McKenzie Limestone Salina Group through McKenzie Limestone Salina Group and McKenzie Limestone Salina Group through McKenzie Limestone Salina Group through McKenzie Limestone Salina Group through McKenzie Limestone Salina Group through McKenzie Limestone Salina Group through Rose Hill Formation Salina Group through Rose Hill Formation Salina Group through Rose Hill Formation Tonoloway Formation Tonoloway Formation Tonoloway Limestone Tonoloway Limestone Tonoloway Limestone Tonoloway Limestone Tonoloway Limestone and Wills Creek Formation Tonoloway Limestone and Wills Creek Formation Tonoloway Limestone and Wills Creek Formation Tonoloway Limestone Tonoloway Limestone through McKenzie Limestone Wills Creek Formation through Rose Hill Formation Wills Creek Formation Wills Creek Formation Wills Creek Formation Wills Creek Formation Wills Creek Formation Wills Creek Formation Wills Creek Formation Wills Creek Formation Wills Creek Formation and McKenzie Limestone Wills Creek Formation and McKenzie Member Wills Creek Formation and McKenzie Limestone Wills Creek Formation and McKenzie Limestone Wills Creek Formation and McKenzie Limestone Wills Creek Formation and McKenzie Limestone Wills Creek Formation and McKenzie Limestone Wills Creek Formation and McKenzie Limestone Wills Creek Formation and McKenzie Limestone McKenzie Limestone Wills Creek Formation through Rose Hill Formation Base of Upper Silurian Salina Group and Wills Creek Formation Wills Creek Formation Eramosa Dolomite Eramosa Dolomite Eramosa Dolomite Top of Lower to Upper Silurian McKenzie Limestone and Lockport Dolomite (or Group) Eramosa Dolomite Lockport Dolomite Lockport Dolomite Lockport Dolomite Lockport Dolomite Lockport Dolomite Lockport Dolomite Lockport Dolomite Lockport Dolomite and Rochester Shale Lockport Dolomite and Rochester Shale McKenzie Member Stratigraphic interval of sample, in approximate ascending order McKenzie Member McKenzie Member McKenzie Limestone McKenzie Limestone McKenzie Limestone McKenzie Limestone McKenzie Limestone McKenzie Limestone McKenzie Member McKenzie Member McKenzie Limestone through Rose Hill Formation McKenzie Limestone through Rose Hill Formation McKenzie Limestone through Rose Hill Formation Base of Lower and Upper Silurian McKenzie Limestone and Lockport Dolomite (or Group) McKenzie Limestone and Keefer Sandstone Rose Hill Formation McKenzie Limestone through Rose Hill Formation Rose Hill Formation Top of Lower Silurian Cabot Head Shale, Rochester Shale, or Rose Hill Formation Rose Hill Formation Rose Hill Formation Rose Hill Formation Rose Hill Formation Rose Hill Formation Rose Hill Formation Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale Rochester Shale and Lower Silurian carbonates and shales, undivided Rochester Shale and Lower Silurian carbonates and shales, undivided Lower Silurian carbonates and shales, undivided Castanea Member of Tuscarora Formation Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale EXPLANATION Cabot Head Shale Cabot Head Shale Cabot Head Shale Locality of sample Cabot Head Shale Cabot Head Shale New York Cabot Head Shale Cabot Head Shale Cabot Head Shale Pennsylvania Cabot Head Shale Cabot Head Shale Ohio Cabot Head Shale Cabot Head Shale Cabot Head Shale West Virginia Cabot Head Shale Cabot Head Shale Cabot Head Shale Stratigraphic boundary Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale Cabot Head Shale 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Total organic carbon (TOC), in weight percent Figure 5. Histogram showing total organic carbon (TOC) values (in weight percent) for Silurian rocks sampled in this study. The probable stratigraphic units that yielded the TOC values are underlined. U.S. Geological Survey Professional Paper 1708–G.11.