Scott J Carpenter - Academia.edu (original) (raw)
Papers by Scott J Carpenter
Quaternary Research, 2007
Two stalagmites from Devil's Icebox Cave, central Missouri, display similar δ13C and δ18O val... more Two stalagmites from Devil's Icebox Cave, central Missouri, display similar δ13C and δ18O values and trends during the late Holocene. Positive δ13C excursions at 3.5–2.6 ka and 1.2–0.9 ka are interpreted to reflect drier conditions. These elevated stalagmite δ13C values could have plausibly been driven by increasing C4 plant abundances over the cave or an increased contribution of bedrock carbon, both of which could reflect decreased effective moisture. A lack of corresponding oxygen isotopic anomalies during these intervals suggests that neither mean annual temperature nor the seasonality of precipitation changed concomitantly with dryness. Both of the δ13C excursions identified in our stalagmite record are roughly coincident with dry intervals from a number of sites located across the Great Plains.
Geology, 2007
Stalagmites from Goshute Cave, located in the Great Basin of the western United States, preserve ... more Stalagmites from Goshute Cave, located in the Great Basin of the western United States, preserve ~20,000 yr of millennial-scale oxygen isotopic variability during marine isotope stages 5c and 5b, similar in timing and structure to Dansgaard-Oeschger (D-O) events 23-21 from the Greenland Ice Sheet Project 2 record. That DO interstades 23-21 were of longer duration than many of the later DO events, coupled with the asymmetric shape of the DO oxygen isotope curve, and the direct U-Th dating of the Goshute Cave stalagmites, allows for an improved understanding of the synchroneity of climatic changes between the western continental United States and the North Atlantic. Eastern Pacifi c-atmosphere interactions are a likely mechanism for transmission of millennial-scale climate variability into the Great Basin.
The Harris (Louisa County, SE Iowa) and Big Spring 4 (Clayton County, NE Iowa) drill cores were s... more The Harris (Louisa County, SE Iowa) and Big Spring 4 (Clayton County, NE Iowa) drill cores were sampled for carbon and oxygen isotopic values of carbonate muds as part of a regional study of the chemostratigraphy of Ordovician Galena and Platteville strata in the Upper Mississippi Valley. Both cores show the marked Chatfieldian positive carbon isotope excursion in the Guttenberg Limestone of the Decorah Formation, with peak d 13 C values reaching between+ 1 and+ 2â VPDB. Both cores also show a lower positive carbon ...
AGU Fall Meeting Abstracts, Dec 1, 2004
Linkage between Aptian-Albian marine, atmospheric, and terrestrial carbon reservoirs is shown by ... more Linkage between Aptian-Albian marine, atmospheric, and terrestrial carbon reservoirs is shown by the d13C chemostratigraphy of pedogenic carbonates in the Cretaceous proximal foreland basin fill of eastern Utah. Profiles from sections that accumulated in the foredeep and forebulge have a well-organized structure that we correlate to Aptian positive d13C excursions associated with Oceanic Anoxic Events (OAEs) 1a and 1b, and support the use of pedogenic carbonates for continental-marine ...
Journal of Sedimentary Research, 1993
Nature, 2003
s.d. ¼ 0.000014; E&A (n ¼ 8), mean (2j m) ¼ 0.708008(13), s.d. ¼ 0.000020. A polynomial least-squ... more s.d. ¼ 0.000014; E&A (n ¼ 8), mean (2j m) ¼ 0.708008(13), s.d. ¼ 0.000020. A polynomial least-squares fit to NBS-987 variance during the analysis period was used to drift-compensate measured ratios relative to a baseline of 0.710242. Compensations for these samples ranged from 20.000015 to 0.000009.
Carbonates and Evaporites, 2010
The Upper Jurassic Mozduran Formation with a thickness of 420 m at the type locality is the most ... more The Upper Jurassic Mozduran Formation with a thickness of 420 m at the type locality is the most important gas-bearing reservoir in NE Iran. It is mainly composed of limestone, dolostone with shale and gypsum interbeds that grade into coarser siliciclastics in the easternmost part of the basin. Eight stratigraphic sections were studied in detail in south of the Agh-Darband area. These analyses suggest that four carbonate facies associations and three siliciclastic lithofacies were deposited in shallow marine to shoreline environments, respectively. Cementation, compaction, dissolution, micritization, neomorphism, hematitization, dolomitization and fracturing are diagenetic processes that affected these sediments. Stable isotope variations of d 18 O and d 13 C in carbonate rocks show two different trends. High depletion of d 18 O and low variation of d 13 C probably reflect increasing temperatures during burial diagenesis, while the higher depletion in carbon isotope values with low variations in oxygen isotopes are related to fresh water flushing during meteoric diagenesis. Negative values of carbon isotopes may have also resulted from organic matter alteration during penetration of meteoric water. Fe and Mn enrichment with depletion of d 18 O also supports the contention that alteration associated with higher depletion in carbon isotope values with low variations in oxygen isotopes took place during meteoric diagenesis. The presence of bright luminescence indicates redox conditions during precipitation of calcite cement.
tem is a prominent component of interannual climate variability, and the Southern Oscillation Ind... more tem is a prominent component of interannual climate variability, and the Southern Oscillation Index (SOI) is a primary measure of the state of the ENSO system (1). Here, we present evidence that ENSO-related changes in the terrestrial car-bon cycle can be recorded by stalagmites, thus providing a proxy for past El Niño events. Our analysis of a stalagmite from Belize reveals a strong correlation between the SOI and carbon isotope ratios (13C values), even though the site experiences no discernible local weather effects that are correlated with the SOI. 13C values of this stalagmite must re-flect changes in the over-lying rainforest ecosys-
Carbonate-cemented, fossil-rich concretions are a prominent feature in the clastic, marine rocks ... more Carbonate-cemented, fossil-rich concretions are a prominent feature in the clastic, marine rocks of the Fox Hills Fm., of North Dakota and South Dakota. Preliminary petrographic, paleontologic, chemical and isotopic data from three sandstone concretions suggest initial nucleation at very shallow burial depths (< 1m). Decomposition of organic-rich fecal material produced localized anoxic and alkaline conditions which induced phosphatization, sulfate reduction (pyrite formation) and possibly adipocire (Ca(RCOO)/sub 2/) formation. These processes were responsible for the formation of an unlithified proto-concretion. The elevated pH at the concretion site allowed calcite precipitation while calcareous shell material in the surrounding sediment experience dissolution. Transformation of adipocire (.) produced a ferroan isopachous carbonate cement. Following this, Fascicular-optic and Radiaxial-fibrous calcite, volumetrically the most significant cement was precipitated. RFC represents ...
The carbon isotope record of soil organic matter (SOM) provides a proxy for local vegetation cond... more The carbon isotope record of soil organic matter (SOM) provides a proxy for local vegetation conditions. On well to moderately well drained alluvial fans in the Midwest, C 3 vegetation is favored during cool and/or moist climatic episodes while C 4 vegetation is dominant ...
Geology, 2016
Data Repository Figure 2 (DR2). 18 O w vs. Paleo-Latitude 18 Ow vs. Paleo-Latitude for sample... more Data Repository Figure 2 (DR2). 18 O w vs. Paleo-Latitude 18 Ow vs. Paleo-Latitude for samples measured in this study. For comparison, two typical assumptions of 18 Ow are shown. These are 1) 18 Ow =-1.0‰ (VSMOW) everywhere (solid line), representing an ice-free world (Shackleton and Kennett, 1975); or 2) the ice-free value adjusted to account for the modern meridional gradient in 18 Ow (dashed line) (Zachos et al, 1994), giving-0.4 to-1.1‰ (VSMOW) for the latitude range covering the WIS. The data show much more variability than predicted by either of these traditional assumptions, potentially explaining why early attempts at reconstructing WIS paleotemperatures failed to produce reasonable temperatures when they assumed a constant 18
![Research paper thumbnail of [delta]18O values, 87Sr/86Sr and Sr/Mg ratios of Late Devonian abiotic marine calcite: Implications for the composition of ancient seawater](https://attachments.academia-assets.com/78603413/thumbnails/1.jpg)
](Late Devonian (Frasnian) abiotic marine calcite has been microsampled and analyzed for R'Sr/*6Sr ... more Late Devonian (Frasnian) abiotic marine calcite has been microsampled and analyzed for R'Sr/*6Sr ratios, 6'*0 and d13C values, and minor element concentrations. Portions of marine cement crystals from the Alberta and Canning Basins have escaped diagenetic alteration and preserve original marine S180 values f-4.8%0 + 0.5, PDB), Si3C values (+2.0 to +3.0b, PDB), *'Sr/*6Sr ratios (0.70805 + 3), and Sr/Mg weight ratios (0.04 to 0.05). Marine s7Sr/86Sr ratios are globally consistent and can be correlated within the Alberta Basin, and among the Alberta, Canning, and Williston Basins. Correlation of isotopic and chemical data strengthen the conclusion that marine cements from the Leduc Formation preserve original marine d180 values which are 3 to 4% lower than those of modern marine cements. These low &'8O values are best explained by precipitation from "O-depleted seawater and not by elevated seawater temperature or diagenetic alteration. For comparison with Devonian data, analogous data were collected from Holocene Mg-calcite and aragonite marine cements from Enewetak Atoll, Map Islands. Mgcalcite and aragonite marine cements are in isotopic equilibrium with ambient seawater, and Mg-calcite cements are homogeneous with respect to Sr and Mg contents. Empirically derived homogeneous distribution coefficients for Mg and Sr in modem, abiotic Mg-calcite from Enewetak Atoll are 0.034 and 0.15, respectively. An equation describing the dependence of r>,, on Mg content was based on a ~mpilation of Sr and Mg data from Holocene abiotic marine calcite (& = 3.52 X 10m6 (ppm Mg) + 6.20 X 10s3). Unlike that derived from experimental data, this Sr-Mg relation is consistent over a range of 4 to 20 mol% MgC03 and may represent precipitation phenomena which are minimally controlled by kinetic effects. Comparison of Sr and Mg contents of analogous Devonian and Holocene marine cements suggests that the Mg/Ca ratio of Late Devonian seawater was significantly lower and that the Sr/Ca ratio was significantly higher than that of modem seawater.
Geochim Cosmochim Acta, 1995
Abstracts With Programs Geological Society of America, 2005
Geochim Cosmochim Acta, 1995
Chemostratigraphic analysis of palustrine carbonate beds in the Cedar Mountain Formation of Easte... more Chemostratigraphic analysis of palustrine carbonate beds in the Cedar Mountain Formation of Eastern Utah has yielded carbon and oxygen isotope data that 1) capture a carbon isotopic excursion curve that is believed to coincide with Oceanic Anoxic Event 1b described by existing oceanic core data, which demonstrates a link between marine, atmospheric, and terrestrial carbon reservoirs, and 2) give us a picture of what was happening to the environment during the Aptian and Albian Ages (121-99 Ma) of the Early Cretaceous, a dynamic period of global climate change. Through petrographic and diagenetic analysis of pedogenic calcite precipitated during this time period, we are able to track the change in δ13C isotope compositions of atmospheric CO2 and terrestrial C3 plants. Pedogenic overprinting demonstrated by the brecciated fabrics found throughout all the carbonate rock samples collected, along with intensive microsampling of different forms of calcite, let us follow the progression of...
Palaeogeography, Palaeoclimatology, Palaeoecology, 2004
Five positive carbon isotope excursions are reported from Platteville-Decorah strata in the Upper... more Five positive carbon isotope excursions are reported from Platteville-Decorah strata in the Upper Mississippi Valley. All occur in subtidal carbonate strata, and are recognized in the Mifflin, Grand Detour, Quimbys Mill, Spechts Ferry, and Guttenberg intervals. The positive carbon isotope excursions are developed in a Platteville-Decorah succession in which background d 13 C values increase upward from about À 2x at the base to about 0x Vienna Pee Dee belemnite (VPDB) at the top. A regional north-south d 13 C gradient, with lighter values to the north and heavier values to the south is also noted. Peak excursion d 13 C values of up to + 2.75 are reported from the Quimbys Mill excursion, and up to + 2.6 from the Guttenberg excursion, although there are considerable local changes in the magnitudes of these events. The Quimbys Mill, Spechts Ferry, and Guttenberg carbon isotope excursions occur in units that are bounded by submarine disconformities, and completely starve out in deeper, more offshore areas. Closely spaced chemostratigraphic profiles of these sculpted, pyrite-impregnated hardground surfaces show that they are associated with very abrupt centimeter-scale negative d 13 C shifts of up to several per mil, possibly resulting from the local diagenetic effects of incursions of euxinic bottom waters during marine flooding events.
Quaternary Research, 2007
Two stalagmites from Devil's Icebox Cave, central Missouri, display similar δ13C and δ18O val... more Two stalagmites from Devil's Icebox Cave, central Missouri, display similar δ13C and δ18O values and trends during the late Holocene. Positive δ13C excursions at 3.5–2.6 ka and 1.2–0.9 ka are interpreted to reflect drier conditions. These elevated stalagmite δ13C values could have plausibly been driven by increasing C4 plant abundances over the cave or an increased contribution of bedrock carbon, both of which could reflect decreased effective moisture. A lack of corresponding oxygen isotopic anomalies during these intervals suggests that neither mean annual temperature nor the seasonality of precipitation changed concomitantly with dryness. Both of the δ13C excursions identified in our stalagmite record are roughly coincident with dry intervals from a number of sites located across the Great Plains.
Geology, 2007
Stalagmites from Goshute Cave, located in the Great Basin of the western United States, preserve ... more Stalagmites from Goshute Cave, located in the Great Basin of the western United States, preserve ~20,000 yr of millennial-scale oxygen isotopic variability during marine isotope stages 5c and 5b, similar in timing and structure to Dansgaard-Oeschger (D-O) events 23-21 from the Greenland Ice Sheet Project 2 record. That DO interstades 23-21 were of longer duration than many of the later DO events, coupled with the asymmetric shape of the DO oxygen isotope curve, and the direct U-Th dating of the Goshute Cave stalagmites, allows for an improved understanding of the synchroneity of climatic changes between the western continental United States and the North Atlantic. Eastern Pacifi c-atmosphere interactions are a likely mechanism for transmission of millennial-scale climate variability into the Great Basin.
The Harris (Louisa County, SE Iowa) and Big Spring 4 (Clayton County, NE Iowa) drill cores were s... more The Harris (Louisa County, SE Iowa) and Big Spring 4 (Clayton County, NE Iowa) drill cores were sampled for carbon and oxygen isotopic values of carbonate muds as part of a regional study of the chemostratigraphy of Ordovician Galena and Platteville strata in the Upper Mississippi Valley. Both cores show the marked Chatfieldian positive carbon isotope excursion in the Guttenberg Limestone of the Decorah Formation, with peak d 13 C values reaching between+ 1 and+ 2â VPDB. Both cores also show a lower positive carbon ...
AGU Fall Meeting Abstracts, Dec 1, 2004
Linkage between Aptian-Albian marine, atmospheric, and terrestrial carbon reservoirs is shown by ... more Linkage between Aptian-Albian marine, atmospheric, and terrestrial carbon reservoirs is shown by the d13C chemostratigraphy of pedogenic carbonates in the Cretaceous proximal foreland basin fill of eastern Utah. Profiles from sections that accumulated in the foredeep and forebulge have a well-organized structure that we correlate to Aptian positive d13C excursions associated with Oceanic Anoxic Events (OAEs) 1a and 1b, and support the use of pedogenic carbonates for continental-marine ...
Journal of Sedimentary Research, 1993
Nature, 2003
s.d. ¼ 0.000014; E&A (n ¼ 8), mean (2j m) ¼ 0.708008(13), s.d. ¼ 0.000020. A polynomial least-squ... more s.d. ¼ 0.000014; E&A (n ¼ 8), mean (2j m) ¼ 0.708008(13), s.d. ¼ 0.000020. A polynomial least-squares fit to NBS-987 variance during the analysis period was used to drift-compensate measured ratios relative to a baseline of 0.710242. Compensations for these samples ranged from 20.000015 to 0.000009.
Carbonates and Evaporites, 2010
The Upper Jurassic Mozduran Formation with a thickness of 420 m at the type locality is the most ... more The Upper Jurassic Mozduran Formation with a thickness of 420 m at the type locality is the most important gas-bearing reservoir in NE Iran. It is mainly composed of limestone, dolostone with shale and gypsum interbeds that grade into coarser siliciclastics in the easternmost part of the basin. Eight stratigraphic sections were studied in detail in south of the Agh-Darband area. These analyses suggest that four carbonate facies associations and three siliciclastic lithofacies were deposited in shallow marine to shoreline environments, respectively. Cementation, compaction, dissolution, micritization, neomorphism, hematitization, dolomitization and fracturing are diagenetic processes that affected these sediments. Stable isotope variations of d 18 O and d 13 C in carbonate rocks show two different trends. High depletion of d 18 O and low variation of d 13 C probably reflect increasing temperatures during burial diagenesis, while the higher depletion in carbon isotope values with low variations in oxygen isotopes are related to fresh water flushing during meteoric diagenesis. Negative values of carbon isotopes may have also resulted from organic matter alteration during penetration of meteoric water. Fe and Mn enrichment with depletion of d 18 O also supports the contention that alteration associated with higher depletion in carbon isotope values with low variations in oxygen isotopes took place during meteoric diagenesis. The presence of bright luminescence indicates redox conditions during precipitation of calcite cement.
tem is a prominent component of interannual climate variability, and the Southern Oscillation Ind... more tem is a prominent component of interannual climate variability, and the Southern Oscillation Index (SOI) is a primary measure of the state of the ENSO system (1). Here, we present evidence that ENSO-related changes in the terrestrial car-bon cycle can be recorded by stalagmites, thus providing a proxy for past El Niño events. Our analysis of a stalagmite from Belize reveals a strong correlation between the SOI and carbon isotope ratios (13C values), even though the site experiences no discernible local weather effects that are correlated with the SOI. 13C values of this stalagmite must re-flect changes in the over-lying rainforest ecosys-
Carbonate-cemented, fossil-rich concretions are a prominent feature in the clastic, marine rocks ... more Carbonate-cemented, fossil-rich concretions are a prominent feature in the clastic, marine rocks of the Fox Hills Fm., of North Dakota and South Dakota. Preliminary petrographic, paleontologic, chemical and isotopic data from three sandstone concretions suggest initial nucleation at very shallow burial depths (< 1m). Decomposition of organic-rich fecal material produced localized anoxic and alkaline conditions which induced phosphatization, sulfate reduction (pyrite formation) and possibly adipocire (Ca(RCOO)/sub 2/) formation. These processes were responsible for the formation of an unlithified proto-concretion. The elevated pH at the concretion site allowed calcite precipitation while calcareous shell material in the surrounding sediment experience dissolution. Transformation of adipocire (.) produced a ferroan isopachous carbonate cement. Following this, Fascicular-optic and Radiaxial-fibrous calcite, volumetrically the most significant cement was precipitated. RFC represents ...
The carbon isotope record of soil organic matter (SOM) provides a proxy for local vegetation cond... more The carbon isotope record of soil organic matter (SOM) provides a proxy for local vegetation conditions. On well to moderately well drained alluvial fans in the Midwest, C 3 vegetation is favored during cool and/or moist climatic episodes while C 4 vegetation is dominant ...
Geology, 2016
Data Repository Figure 2 (DR2). 18 O w vs. Paleo-Latitude 18 Ow vs. Paleo-Latitude for sample... more Data Repository Figure 2 (DR2). 18 O w vs. Paleo-Latitude 18 Ow vs. Paleo-Latitude for samples measured in this study. For comparison, two typical assumptions of 18 Ow are shown. These are 1) 18 Ow =-1.0‰ (VSMOW) everywhere (solid line), representing an ice-free world (Shackleton and Kennett, 1975); or 2) the ice-free value adjusted to account for the modern meridional gradient in 18 Ow (dashed line) (Zachos et al, 1994), giving-0.4 to-1.1‰ (VSMOW) for the latitude range covering the WIS. The data show much more variability than predicted by either of these traditional assumptions, potentially explaining why early attempts at reconstructing WIS paleotemperatures failed to produce reasonable temperatures when they assumed a constant 18
Late Devonian (Frasnian) abiotic marine calcite has been microsampled and analyzed for R'Sr/*6Sr ... more Late Devonian (Frasnian) abiotic marine calcite has been microsampled and analyzed for R'Sr/*6Sr ratios, 6'*0 and d13C values, and minor element concentrations. Portions of marine cement crystals from the Alberta and Canning Basins have escaped diagenetic alteration and preserve original marine S180 values f-4.8%0 + 0.5, PDB), Si3C values (+2.0 to +3.0b, PDB), *'Sr/*6Sr ratios (0.70805 + 3), and Sr/Mg weight ratios (0.04 to 0.05). Marine s7Sr/86Sr ratios are globally consistent and can be correlated within the Alberta Basin, and among the Alberta, Canning, and Williston Basins. Correlation of isotopic and chemical data strengthen the conclusion that marine cements from the Leduc Formation preserve original marine d180 values which are 3 to 4% lower than those of modern marine cements. These low &'8O values are best explained by precipitation from "O-depleted seawater and not by elevated seawater temperature or diagenetic alteration. For comparison with Devonian data, analogous data were collected from Holocene Mg-calcite and aragonite marine cements from Enewetak Atoll, Map Islands. Mgcalcite and aragonite marine cements are in isotopic equilibrium with ambient seawater, and Mg-calcite cements are homogeneous with respect to Sr and Mg contents. Empirically derived homogeneous distribution coefficients for Mg and Sr in modem, abiotic Mg-calcite from Enewetak Atoll are 0.034 and 0.15, respectively. An equation describing the dependence of r>,, on Mg content was based on a ~mpilation of Sr and Mg data from Holocene abiotic marine calcite (& = 3.52 X 10m6 (ppm Mg) + 6.20 X 10s3). Unlike that derived from experimental data, this Sr-Mg relation is consistent over a range of 4 to 20 mol% MgC03 and may represent precipitation phenomena which are minimally controlled by kinetic effects. Comparison of Sr and Mg contents of analogous Devonian and Holocene marine cements suggests that the Mg/Ca ratio of Late Devonian seawater was significantly lower and that the Sr/Ca ratio was significantly higher than that of modem seawater.
Geochim Cosmochim Acta, 1995
Abstracts With Programs Geological Society of America, 2005
Geochim Cosmochim Acta, 1995
Chemostratigraphic analysis of palustrine carbonate beds in the Cedar Mountain Formation of Easte... more Chemostratigraphic analysis of palustrine carbonate beds in the Cedar Mountain Formation of Eastern Utah has yielded carbon and oxygen isotope data that 1) capture a carbon isotopic excursion curve that is believed to coincide with Oceanic Anoxic Event 1b described by existing oceanic core data, which demonstrates a link between marine, atmospheric, and terrestrial carbon reservoirs, and 2) give us a picture of what was happening to the environment during the Aptian and Albian Ages (121-99 Ma) of the Early Cretaceous, a dynamic period of global climate change. Through petrographic and diagenetic analysis of pedogenic calcite precipitated during this time period, we are able to track the change in δ13C isotope compositions of atmospheric CO2 and terrestrial C3 plants. Pedogenic overprinting demonstrated by the brecciated fabrics found throughout all the carbonate rock samples collected, along with intensive microsampling of different forms of calcite, let us follow the progression of...
Palaeogeography, Palaeoclimatology, Palaeoecology, 2004
Five positive carbon isotope excursions are reported from Platteville-Decorah strata in the Upper... more Five positive carbon isotope excursions are reported from Platteville-Decorah strata in the Upper Mississippi Valley. All occur in subtidal carbonate strata, and are recognized in the Mifflin, Grand Detour, Quimbys Mill, Spechts Ferry, and Guttenberg intervals. The positive carbon isotope excursions are developed in a Platteville-Decorah succession in which background d 13 C values increase upward from about À 2x at the base to about 0x Vienna Pee Dee belemnite (VPDB) at the top. A regional north-south d 13 C gradient, with lighter values to the north and heavier values to the south is also noted. Peak excursion d 13 C values of up to + 2.75 are reported from the Quimbys Mill excursion, and up to + 2.6 from the Guttenberg excursion, although there are considerable local changes in the magnitudes of these events. The Quimbys Mill, Spechts Ferry, and Guttenberg carbon isotope excursions occur in units that are bounded by submarine disconformities, and completely starve out in deeper, more offshore areas. Closely spaced chemostratigraphic profiles of these sculpted, pyrite-impregnated hardground surfaces show that they are associated with very abrupt centimeter-scale negative d 13 C shifts of up to several per mil, possibly resulting from the local diagenetic effects of incursions of euxinic bottom waters during marine flooding events.