scholarly journals Is Paleoproterozoic Atmospheric Oxygenation Linked to the Emergence of Continents Above Sea-Level? Evidence from Sulfur and Oxygen Isotopic Signatures in Archean to Proterozoic Sediment-Derived Granitoids

2020 ◽  
Author(s):  
Janne Liebmann ◽  
Christopher J. Spencer ◽  
Claire E. Bucholz ◽  
Christopher L Kirkland ◽  
Laure Martin ◽  
...  
Keyword(s):  
Sea Level ◽  
Isotopic Signatures ◽  
Oxygen Isotopic

Diagenesis of Hunton Group Carbonates (Silurian) West Carney Field, Logan and Lincoln Counties, Oklahoma, U.S.A.

2020 ◽  
Vol 1 ◽  
pp. 30-51
Author(s):  
Cesar Silva ◽  
Brian J. Smith ◽  
Jordan T. Ray ◽  
James R. Derby ◽  
Jay M. Gregg
Keyword(s):  
Sea Level ◽  
Open Space ◽  
Oil Field ◽  
Woodford Shale ◽  
Isotopic Signatures ◽  
Fine Grained ◽  
Carbon And Oxygen Isotope ◽  
Petroleum Generation ◽  
Oxygen Isotopic ◽  
Diagenetic Fluid

The West Carney Hunton Field (WCHF) is an important oil field in central Oklahoma. Deposited during a series of sea-level rises and falls on a shallow shelf, the Cochrane and Clarita Formations (Hunton Group) have undergone a complex series of diagenetic events. The Hunton section of the WCHF comprises dolomitized crinoidal packstones, brachiopod “reefs” and grainstones, thin intervals of fine-grained crinoidal wackestones, and infrequent mudstones that were diagenetically affected by repeated sea-level change. Widespread karst is evidenced by multiple generations of solution-enlarged fractures, vugs, and breccias, which extend through the entire thickness of the Hunton. Karst development likely occurred during sea-level lowstands. Partial to complete dolomitization of Hunton limestones is interpreted to have occurred as a result of convective circulation of normal seawater during sea-level highstands. Open-space-filling calcite cements postdate dolomitization and predate deposition of the overlying siliciclastic section, which comprises the Misener Sandstone and Woodford Shale. Petrographic evaluation and carbon and oxygen isotope values of the calcite cements suggest precipitation by Silurian seawater and mixed seawater and meteoric water. Carbon and oxygen isotopic signatures of dolomite may have been partially reset by dedolomitization that was concurrent with calcite cementation. Fluid inclusions in late diagenetic celestite crystals observed in the Clarita Formation indicate that the WCHF was invaded by saline basinal fluids and petroleum after burial, during later stages of diagenesis. The timing of late diagenetic fluid flow and petroleum generation likely was during the Ouachita orogeny, which was occurring to the south. There is no evidence that late diagenetic fluids significantly altered the dolomite reservoir that formed earlier. The WCHF provides an ancient example of early diagenetic dolomitization by seawater that remains relatively unaltered by later diagenetic events.

Changes of Ionic and Oxygen Isotopic Composition of the Snowpack at the Glacier Austre Okstindbreen, Norway, 1995

1998 ◽  
Vol 29 (1) ◽  
pp. 1-20 ◽  
Author(s):  
Peter Raben ◽  
Wilfred H. Theakstone
Keyword(s):  
Isotopic Composition ◽  
Sea Level ◽  
Oxygen Isotopes ◽  
Oxygen Isotopic Composition ◽  
Isotopic Ratios ◽  
Vertical Variations ◽  
Oxygen Isotopic ◽  
The Difference ◽  
Liquid Precipitation ◽  
Different Altitudes

Marked vertical variations of ions and oxygen isotopes were present in the snowpack at the glacier Austre Okstindbreen during the pre-melting phase in 1995 at sites between 825 m and 1,470 m above sea level. As the first meltwater percolated from the top of the pack, ions were moved to a greater depth, but the isotopic composition remained relatively unchanged. Ions continued to move downwards through the pack during the melting phase, even when there was little surface melting and no addition of liquid precipitation. The at-a-depth correlation between ionic concentrations and isotopic ratios, strong in the pre-melting phase, weakened during melting. In August, concentrations of Na+ and Mg2+ ions in the residual pack were low and vertical variations were slight; 18O enrichment had occurred. The difference of the time at which melting of the snowpack starts at different altitudes influences the input of ions and isotopes to the underlying glacier.

Characteristics and its Environment Implications of Carbon and Oxygen Isotopic of Ordovician Carbonate Rock in Yubei Area

2015 ◽  
Vol 1092-1093 ◽  
pp. 1375-1378
Author(s):  
Qian Zhang ◽  
Wen Hui Huang ◽  
Ya Mei Zhang
Keyword(s):  
Sea Level ◽  
Carbonate Rocks ◽  
Carbonate Rock ◽  
Burial Depth ◽  
Oxygen Stable Isotopes ◽  
Oxygen Isotopic ◽  
Oxygen Stable Isotope ◽  
The Stability ◽  
Diagenetic Environment ◽  
Stable Isotope Data

Based on a large number of carbon and oxygen stable isotope data, researched environment characteristics of Ordovician carbonate rocks in Yubei area, Tarim Basin. According to carbon, oxygen stable isotopes (&13C, &18O) data, combining the diagenetic environment characteristics studied all kinds of geochemical characteristics of rocks in Yubei area. The research results show that: Paleosalinity feature of Ordovician carbonate rocks in this area reflected the carbonate rocks is formed in the stability of the marine environment and basically kept the composition of carbon and oxygen isotopic of the original environment. the paleo temperature characteristics indicate that the diagenetic burial depth was increased first and then decreased, the sea level characteristics indicate that the sedimentary strata by Yingshan period to Lianglitage period corresponds with a rise in sea level.

Climate and Sea Level During Oxygen Isotope Stage 7b: On-Land Evidence from New Zealand

1988 ◽  
Vol 29 (2) ◽  
pp. 176-185 ◽  
Author(s):  
Brad Pillans ◽  
Geoff Holgate ◽  
Matt McGlone
Keyword(s):  
New Zealand ◽  
Oxygen Isotope ◽  
Sea Level ◽  
Northern Hemisphere ◽  
Pollen Analysis ◽  
Deep Sea ◽  
Sea Level Changes ◽  
Oxygen Isotope Stage ◽  
Oxygen Isotopic ◽  
And Sea Level

Strata at Landguard Bluff, near Wanganui, New Zealand preserve a clear record of relative sea-level changes during oxygen-isotope stage 7. Two relative high sea-level stands (during stages 7a about 210,000 yr ago and 7c about 240,000 yr ago) are separated by a relative low sea level (stage 7b) that was at least 32 m lower than present. Pollen analysis of sediment deposited during stage 7b indicates climate at the time was up to 3°C cooler than present. The climate and sea-level evidence from Landguard Bluff are consistent with oxygen-isotopic evidence from deep-sea cores indicating a marked cooling during stage 7, which is closely associated with a summer radiation minimum centered at about 230,000 yr ago in the Northern Hemisphere.

scholarly journals Fault Zone Evolution and Development of a Structural and Hydrological Barrier: The Quartz Breccia in the Kiggavik Area (Nunavut, Canada) and Its Control on Uranium Mineralization

Minerals ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 319 ◽  
Author(s):  
Alexis Grare ◽  
Olivier Lacombe ◽  
Julien Mercadier ◽  
Antonio Benedicto ◽  
Marie Guilcher ◽  
...  
Keyword(s):  
Early Stage ◽  
Field Work ◽  
Uranium Mineralization ◽  
Isotopic Signatures ◽  
Thelon Basin ◽  
Tectonic History ◽  
Evolution And Development ◽  
Major Fault ◽  
History Of ◽  
Oxygen Isotopic

In the Kiggavik area (Nunavut, Canada), major fault zones along, or close to, where uranium deposits are found are often associated with occurrence of thick quartz breccia (QB) bodies. These bodies formed in an early stage (~1750 Ma) of the long-lasting tectonic history of the Archean basement, and of the Proterozoic Thelon basin. The main characteristics of the QB are addressed in this study; through field work, macro and microscopic observations, cathodoluminescence microscopy, trace elements, and oxygen isotopic signatures of the quartz forming the QB. Faults formed earlier during syn- to post-orogenic rifting (1850–1750 Ma) were subsequently reactivated, and underwent cycles of cataclasis, pervasive silicification, hydraulic brecciation, and quartz recrystallization. This was synchronous with the circulation of meteoric fluids mixing with Si-rich magmatic-derived fluids at depth, and were coeval with the emplacement of the Kivalliq igneous suite at 1750 Ma. These processes led to the emplacement of up to 30 m thick QB, which behaved as a mechanically strong, transverse hydraulic barrier that localized later fracturing, and compartmentalized/channelized vertical flow of uranium-bearing fluids after the deposition of the Thelon Basin (post 1750 Ma). The development and locations of QB control the location of uranium mineralization in the Kiggavik area.

scholarly journals Dynamic Antarctic ice sheet during the early to mid-Miocene

2016 ◽  
Vol 113 (13) ◽  
pp. 3459-3464 ◽  
Author(s):  
Edward Gasson ◽  
Robert M. DeConto ◽  
David Pollard ◽  
Richard H. Levy
Keyword(s):  
Sea Level ◽  
Large Scale ◽  
Ross Sea ◽  
Ice Sheet ◽  
Oxygen Isotopic Composition ◽  
Climate Feedbacks ◽  
Ice Shelf ◽  
Antarctic Ice Sheet ◽  
Proxy Records ◽  
Oxygen Isotopic

Geological data indicate that there were major variations in Antarctic ice sheet volume and extent during the early to mid-Miocene. Simulating such large-scale changes is problematic because of a strong hysteresis effect, which results in stability once the ice sheets have reached continental size. A relatively narrow range of atmospheric CO2 concentrations indicated by proxy records exacerbates this problem. Here, we are able to simulate large-scale variability of the early to mid-Miocene Antarctic ice sheet because of three developments in our modeling approach. (i) We use a climate–ice sheet coupling method utilizing a high-resolution atmospheric component to account for ice sheet–climate feedbacks. (ii) The ice sheet model includes recently proposed mechanisms for retreat into deep subglacial basins caused by ice-cliff failure and ice-shelf hydrofracture. (iii) We account for changes in the oxygen isotopic composition of the ice sheet by using isotope-enabled climate and ice sheet models. We compare our modeling results with ice-proximal records emerging from a sedimentological drill core from the Ross Sea (Andrill-2A) that is presented in a companion article. The variability in Antarctic ice volume that we simulate is equivalent to a seawater oxygen isotope signal of 0.52–0.66‰, or a sea level equivalent change of 30–36 m, for a range of atmospheric CO2 between 280 and 500 ppm and a changing astronomical configuration. This result represents a substantial advance in resolving the long-standing model data conflict of Miocene Antarctic ice sheet and sea level variability.

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