Strontium Variations in a Speleothem from Crevice Cave, Missouri: Potential for High Resolution Paleoclimate Reconstruction

Title:
Strontium Variations in a Speleothem from Crevice Cave, Missouri: Potential for High Resolution Paleoclimate Reconstruction
Authors:
Oster, Jessica
Abstract:
Speleothems are capable of providing high-resolution terrestrial paleoclimate records, through proxies that include carbon and oxygen isotopes, luminescence banding, and variations in elemental concentrations. Here I present an investigation of magnesium and strontium variations in a calcite stalagmite from Crevice Cave, Missouri. Using an electron microprobe, researchers at the University of Minnesota and I were able to produce quantitative, high resolution line transects and qualitative map analyses across optical banding in the stalagmite. The alternating light and dark optical bands are visible using transmitted light on a petrographic microscope. My measurement of these bands and U/Th dating of the stalagmite completed by Jeff Dorale indicate that the bands are either or seasonal or annual scale. Our quantitative line transect shows that the variations in strontium concentration are of the same scale as the optical banding. The strontium record is in phase with the optical banding, with peaks generally associated with the light portion of the band and troughs with the darker portion. Magnesium concentration also varies regularly, yet on a different scale. Our microprobe analyses have uncovered extraordinarily high strontium concentrations (~20,OOO ppm) in this particular speleothem from Crevice Cave. However, analysis by X-ray diffraction reveals a calcite mineralogy, with no measurable aragonite or strontianite. We have also found large amounts of strontium in other Crevice Cave stalagmites through ICP-MS analyses. The extraordinary amounts of strontium present in Crevice Cave speleothems most likely originate from celestite and strontianite deposits located in the lower portion of the Joachim Formation in which Crevice Cave has formed. Variations in dissolution of these minerals likely led to variations in strontium concentration of Crevice Cave groundwater, and subsequently to the stronitum variations measured in the stalagmite. The solubility product (Ksp) of celestite can be affected by several environmental factors. Using the equation for Ksp as a function of temperature presented by Reardon and Armstrong (1987), I was able to rule out variations in temperature above Crevice Cave as a cause for the strontium variations in the stalagmite. Celestite dissolution is also controlled by the reaction occurring at the mineral-water interface. Therefore, as more celestite will dissolve with longer contact with groundwater, changes in groundwater residence time above the cave are likely responsible for the measured strontium variations. Another possible cause for the strontium variations is changes in groundwater flow routes due to events of large groundwater infiltration. These events could force groundwater down less traveled paths, thus exposing it to larger or less dissolved populations of strontium-rich minerals.
Citation:
Oster, Jessica. “Strontium Variations in a Speleothem from Crevice Cave, Missouri: Potential for High Resolution Paleoclimate Reconstruction.” Honors thesis, Oberlin College, Spring 2003.
Type:
Thesis
Degree Level:
Bachelor of Arts
Discipline:
Geology
Degree Year:
2003
Notes:
CLICK THE LINK BELOW TO REQUEST THIS THESIS
Additional Links:
http://www.oberlinlibstaff.com/testform.2.html
PERMANENT LINK:
http://hdl.handle.net/11282/581215

Full metadata record

DC FieldValue Language
dc.contributor.authorOster, Jessicaen
dc.date.accessioned2015-10-26T13:39:30Zen
dc.date.available2015-10-26T13:39:30Zen
dc.date.issued1905-06-25en
dc.identifier.citationOster, Jessica. “Strontium Variations in a Speleothem from Crevice Cave, Missouri: Potential for High Resolution Paleoclimate Reconstruction.” Honors thesis, Oberlin College, Spring 2003.en
dc.identifier.urihttp://hdl.handle.net/11282/581215en
dc.description.abstractSpeleothems are capable of providing high-resolution terrestrial paleoclimate records, through proxies that include carbon and oxygen isotopes, luminescence banding, and variations in elemental concentrations. Here I present an investigation of magnesium and strontium variations in a calcite stalagmite from Crevice Cave, Missouri. Using an electron microprobe, researchers at the University of Minnesota and I were able to produce quantitative, high resolution line transects and qualitative map analyses across optical banding in the stalagmite. The alternating light and dark optical bands are visible using transmitted light on a petrographic microscope. My measurement of these bands and U/Th dating of the stalagmite completed by Jeff Dorale indicate that the bands are either or seasonal or annual scale. Our quantitative line transect shows that the variations in strontium concentration are of the same scale as the optical banding. The strontium record is in phase with the optical banding, with peaks generally associated with the light portion of the band and troughs with the darker portion. Magnesium concentration also varies regularly, yet on a different scale. Our microprobe analyses have uncovered extraordinarily high strontium concentrations (~20,OOO ppm) in this particular speleothem from Crevice Cave. However, analysis by X-ray diffraction reveals a calcite mineralogy, with no measurable aragonite or strontianite. We have also found large amounts of strontium in other Crevice Cave stalagmites through ICP-MS analyses. The extraordinary amounts of strontium present in Crevice Cave speleothems most likely originate from celestite and strontianite deposits located in the lower portion of the Joachim Formation in which Crevice Cave has formed. Variations in dissolution of these minerals likely led to variations in strontium concentration of Crevice Cave groundwater, and subsequently to the stronitum variations measured in the stalagmite. The solubility product (Ksp) of celestite can be affected by several environmental factors. Using the equation for Ksp as a function of temperature presented by Reardon and Armstrong (1987), I was able to rule out variations in temperature above Crevice Cave as a cause for the strontium variations in the stalagmite. Celestite dissolution is also controlled by the reaction occurring at the mineral-water interface. Therefore, as more celestite will dissolve with longer contact with groundwater, changes in groundwater residence time above the cave are likely responsible for the measured strontium variations. Another possible cause for the strontium variations is changes in groundwater flow routes due to events of large groundwater infiltration. These events could force groundwater down less traveled paths, thus exposing it to larger or less dissolved populations of strontium-rich minerals.en
dc.relation.urlhttp://www.oberlinlibstaff.com/testform.2.htmlen
dc.titleStrontium Variations in a Speleothem from Crevice Cave, Missouri: Potential for High Resolution Paleoclimate Reconstructionen
dc.typeThesisen
thesis.degree.levelBachelor of Artsen
thesis.degree.disciplineGeologyen
thesis.degree.year2003en
dc.description.notesCLICK THE LINK BELOW TO REQUEST THIS THESISen
All Items in The Five Colleges of Ohio Digital Repository are protected by copyright, with all rights reserved, unless otherwise indicated.