Physical Sciences and Mathematics Commons^™

Lithology And Depositional Environments Of A Portion Of The Clays Ferry Formation (Middle And Upper Ordovician) Exposed At Silver Creek, Madison County, Kentucky, Autumn Murray, Walter S. Borowski

EKU Faculty and Staff Scholarship

We measure, describe, and interpret a carbonate stratigraphic section within the Clays Ferry Formation (Middle and Upper Ordovician) cropping out in Madison County, Kentucky (USGS Kirksville 7.5” quadrangle). Outcrops are exposed within the bed of Silver Creek along Ky 876 (Barnes Mill Road) from ~100 m downstream of where a bridge crosses the stream, then upstream and upsection for a distance of ~300 m over several sets of falls until bedrock exposure becomes sporadic to absent. We sampled the stratigraphic section at approximately half-meter intervals, also taking samples at lithology changes. We collected a total 18 samples, all of which …

Lithology And Depositional Environments Of A Portion Of The Clays Ferry Formation (Middle And Upper Ordovician) Exposed At Silver Creek, Madison County, Kentucky, Autumn Murray

EKU Faculty and Staff Scholarship

We measure, describe, and interpret a carbonate stratigraphic section within the Clays Ferry Formation (Middle and Upper Ordovician) cropping out in Madison County, Kentucky (USGS Kirksville 7.5” quadrangle). The total thickness of the measured section is 4.76 m. We sampled the stratigraphic section at approximately half-meter intervals, also taking samples at lithology changes. We collected a total 20 samples, all of which were slabbed, and then selected 12 samples for thin section analysis.

Observed lithologies represent discrete depositional environments. The rocks are dominantly limestones with some carbonate shales deposited in shallow-water depositional environments that are generally open-marine, subtidal with perhaps …

Lithology And Depositional Environments Of A Portion Of The Clays Ferry Formation (Middle And Upper Ordovician) Exposed At Silver Creek, Madison County, Kentucky, Autumn Murray, Walter S. Borowski

EKU Faculty and Staff Scholarship

We measure, describe, and interpret a carbonate stratigraphic section within the Clays Ferry Formation (Middle and Upper Ordovician) cropping out in Madison County, Kentucky (USGS Kirksville 7.5” quadrangle). Outcrops are exposed within the bed of Silver Creek along Ky 876 (Barnes Mill Road) from ~100 m downstream of where a bridge crosses the stream, then upstream and upsection for a distance of ~300 m over several sets of falls until bedrock exposure becomes sporadic to absent. We sampled the stratigraphic section at approximately half-meter intervals, also taking samples at lithology changes. We collected a total 18 samples, all of which …

Changing Depositional Environments In An Upper Ordovician Stratigraphic Sequence, Ashlock Formation, Madison County, Kentucky, Kevin G. Greff, Walter S. Borowski

EKU Faculty and Staff Scholarship

We investigate the sedimentology, stratigraphy, and depositional environments of a 7-meter, Upper Ordovician limestone sequence cropping out in Richmond, Madison County, Kentucky. The stratigraphic section lies within the Ashlock Formation with good lateral exposure stretching along 200 meters of a highway roadcut. We took approximately 20 samples from the measured section, focusing on representative samples and lithologic transitions. We use standard laboratory procedures in slabbing rock samples and making thin sections.

The Ashlock Formation here consists of alternating layers of limey mudstone and limestone (field units A through F). Megafossils - brachiopods, bryozoans, trilobites, gastropods, ostracodes, coralline algae, and bivalves …

Sulfur Geochemistry And Diagenesis In A Gas Hydrate Terrane, Cascadia Margin, Offshore Oregon: Role Of Anaerobic Methane Oxidation, David Deigert, Walter S. Borowski

EKU Faculty and Staff Scholarship

We present sulfide mineral data from south Hydrate Ridge located in a gas hydrate terrane, offshore Oregon. Sulfide sulfur concentration and the isotopic composition of sulfur (d³⁴S) in authigenic sulfide minerals are analyzed from sediment samples collected on Ocean Drilling Project (ODP) Leg 204. Shallow sediment samples (<25 >mbsf) assess the relative importance of anaerobic methane oxidation (AMO) as a biogeochemical process, both here and at the Blake Ridge, another well known gas hydrate terrane offshore southeastern United States. Deep samples (>25 mbsf) are used to evaluate sulfur diagenesis and its controls from early Pleistocene to the …

A Preliminary Study Of Sulfide Mineral Formation In Methane-Rich, Marine Sediments Associated With Anaerobic Methane Oxidation, Cascadia Continental Margin, Offshore Oregon, David Deigert, Walter S. Borowski

EKU Faculty and Staff Scholarship

Within gas hydrate settings, sulfide mineralization in marine sediments is likely controlled by two microbially-mediated, sulfate-depleting processes: anaerobic methane oxidation (AMO) and sulfate reduction. If large amounts of methane are delivered to the sulfate-methane interface (SMI), predominantly by diffusion, larger amounts of solid sulfide sulfur should occur there as dissolved sulfide combines with iron, forming an authigenic precipitate. We measure the amount of diagenetic sulfide sulfur at three locations in the Hydrate Ridge vicinity by extracting the bulk sedimentary sulfide-phase minerals (S^o, FeS, and FeS₂) through chromium reduction, precipitating sulfide sulfur as silver sulfide, and gravimetrically …

A Geologic Record Of Competing Sulfate-Depletion Processes Within Continental-Rise Sediments Overlying Methane Gas Hydrates Of The Blake Ridge Region (Continental Rise, Offshore Southeastern United States), Walter S. Borowski, Kathryn G. Takacs, Matthew K. Thompson

EKU Faculty and Staff Scholarship

Geochemical signals locked within sediments and sedimentary rocks record geochemical processes through geologic time. Sulfide minerals (elemental sulfur, iron monosulfides, and pyrite) are formed within marine sediments as dissolved sulfide is produced by various geochemical processes, which include sulfate reduction and anaerobic methane oxidation (AMO). The concentration and sulfur isotopic composition (d³⁴S) of sulfide minerals gives clues about the relative importance of these competing geochemical processes, and consequently about sedimentation rates and upward methane transport.

Marine sediments of the Blake Ridge(offshore South Carolina and Georgia) contain sulfide minerals that point to AMO as an important diagenetic process both …

A Preliminary Comparison Of The Sulfur Geochemistry Between Two Gas Hydrate Terranes, Michael D. Spicer, Walter S. Borowski

EKU Faculty and Staff Scholarship

We compare the authigenic sulfide mineral geochemistry of two, different gas hydrate terranes: the accretionary wedge of the Cascadia continental margin (offshore Oregon) and the passive margin of the Blake Ridge region (offshore southeastern US). We expect diagenetic processes effecting sulfide mineral formation (elemental sulfur, iron monosulfides, and pyrite) within these sediments to respond to differing geologic conditions at each setting. In both settings, methane diffuses upward from gas hydrates to the methane-sulfate interface (SMI), where it is consumed by reaction with sulfate during anaerobic methane oxidation (AMO). This microbially-mediated, diagenetic process produces an interstitial environment conducive to authigenic sulfide …

A Geologic Record Of Methane Consumption Associated With Methane Gas Hydrates At Blake Ridge Region (Continental Rise, Offshore Southeastern United States), Walter S. Borowski, Kathryn G. Takacs, Matthew K. Thompson

EKU Faculty and Staff Scholarship

Geochemical signals locked within sedimentary rocks are a record of earth processes. Sulfide minerals (elemental sulfur, iron monosulfides, and pyrite) are formed within marine sediments by several different geochemical processes mediated by microbes. Investigating the concentration and sulfur isotopic composition (d³⁴S) of sulfide minerals gives clues about the relative importance of these competing geochemical processes.

Marine sediments of the Blake Ridge(offshore South Carolina and Georgia) contain sulfide minerals that point to anaerobic methane oxidation (AMO) as an important diagenetic process both today and in the recent geological past (Miocene). At the present-day methane-sulfate interface, upward-diffusing methane is consumed …

Sulfide Mineralization In Deep-Water Marine Sediments Related To Methane Transport, Methane Consumption, And Methane Gas Hydrates, Matthew K. Thompson, Walter S. Borowski, Charles K. Paull, William Ussler Iii

EKU Faculty and Staff Scholarship

Patterns of sulfide sulfur concentration and sulfur isotopic composition (d³⁴ S) are perhaps related to upward methane transport, especially in sediments underlain by methane gas hydrate deposits. Increased methane delivery augments the effect of anaerobic methane oxidation (AMO) occurring at the sulfate-methane interface (SMI). Sulfate and methane co-consumption results in production of dissolved sulfide at the interface that is eventually sequestered within sulfide minerals (elemental sulfur, iron monosulfide, pyrite).

We examine the sediments of two piston cores collected over the Blake Ridge gas hydrate deposits (offshore southeastern United States) by extracting total sedimentary sulfide using chromium reduction. We use …

Relative Concentration Of Solid-Phase Sulfide Species In Marine Sediments Overlying Gas Hydrate Deposits: Recognition Of The Role Of Anaerobic Methane Oxidation In Authigenic Sulfide Formation, Matthew K. Thompson, Walter S. Borowski, Charles K. Paull, William Ussler Iii

EKU Faculty and Staff Scholarship

Sulfide mineralization in marine sediments occurs when dissolved sulfide, produced by sulfate reduction processes, combines with dissolved iron to form iron sulfide minerals. Sulfide can be produced by oxidation of organic matter or by anaerobic methane oxidation (AMO), which involves the co-consumption of sulfate and methane. The latter process seems especially important within gas hydrate terrains like that of theBlakeRidge(offshore southeasternUnited States), where appreciable amounts of methane diffuse upward to the base of the sulfate reduction zone, or sulfate-methane interface (SMI).

We examine the sediments of two piston cores collected over the Blake Ridge gas hydrate deposits by sequentially extracting …

Changes In Sulfur Concentration And Sulfur Isotopic Composition Within Authigenic Sulfide Minerals From Sediments Of Miocene Age To The Present, Odp Site 995, Blake Ridge, Offshore Southeastern United States, Kathryn G. Takacs, Walter S. Borowski

EKU Faculty and Staff Scholarship

The Blake Ridge area (offshore southeastern United States) consists of deep-water continental margin sediments overlying deposits of methane gas hydrate. Authigenic sulfide minerals (elemental sulfur, S˚; iron monosulfides, ~FeS; and pyrite, FeS₂) are actively deposited in these sediments due to sulfate reduction and focused anaerobic methane oxidation (AMO) at the sulfate-methane interface (SMI). Sulfide minerals at the present SMI are enriched in ³⁴S relative to those produced by sulfate reduction of organic matter higher in the sulfate reduction zone. ³⁴S enrichments preserved in the sediment column may identify relatively high amounts of AMO and thus record …

Sulfide Mineralization In Deep-Water Marine Sediments Related To Methane Transport, Methane Consumption, And Methane Gas Hydrates, Matthew K. Thompson, Walter S. Borowski, Charles K. Paull, William Ussler Iii

EKU Faculty and Staff Scholarship

Patterns of sulfide sulfur concentration and sulfur isotopic composition (d³⁴ S) are perhaps related to upward methane transport, especially in sediments underlain by methane gas hydrate deposits. Increased methane delivery augments the effect of anaerobic methane oxidation (AMO) occurring at the sulfate-methane interface (SMI). Sulfate and methane co-consumption results in production of dissolved sulfide at the interface that is eventually sequestered within sulfide minerals (elemental sulfur, iron monosulfide, pyrite).

We examine the sediments of two piston cores collected over the Blake Ridge gas hydrate deposits (offshore southeastern United States) by extracting total sedimentary sulfide using chromium reduction. We use …

Sulfide Mineralization In Deep-Water Marine Sediments Related To Methane Transport, Methane Consumption, And Methane Gas Hydrates, Matthew K. Thompson, Walter S. Borowski, Charles K. Paull, William Ussler Iii

EKU Faculty and Staff Scholarship

Patterns of sulfide sulfur concentration and sulfur isotopic composition (d³⁴S) are perhaps related to upward methane transport, especially in sediments underlain by methane gas hydrate deposits. Increased methane delivery augments the affect of anaerobic methane oxidation (AMO) occurring at the sulfate-methane interface (SMI). Sulfate and methane co-consumption results in production of dissolved sulfide at the interface that is eventually sequestered within sulfide minerals (elemental sulfur, iron monosulfide, pyrite).

We examine the sediments of two piston cores collected over the Blake Ridge gas hydrate deposits (offshore southeastern North America) by extracting total sedimentary sulfide using chromium reduction. We use …

Enrichments Of 34s In Sulfide Minerals Of Deep-Water Marine Sediments Of The Blake Ridge, Offshore Southeastern United States, Kathryn G. Takacs, Walter S. Borowski

EKU Faculty and Staff Scholarship

Past research shows that active sulfide mineralization occurs at the base of the sulfate reduction zone (SRZ) in modern, deep-water, continental-margin sediments that overlie methane gas hydrate. These sulfide minerals (elemental sulfur, Sº; iron monosulfides, ~FeS; and pyrite, FeS₂) are enriched in ³⁴S because of sulfate reduction and anaerobic methane oxidation (AMO) processes occurring above and near the sulfate-methane interface (SMI).

The data in this study show that 5 discrete zones of sulfide minerals are preserved in a 703.8-meter sediment column associated with methane gas hydrate. These zones of sulfide minerals are also enriched in ³⁴S. …