Download
slide1 n.
Skip this Video
Loading SlideShow in 5 Seconds..
Study Area and Regional Geology PowerPoint Presentation
Download Presentation
Study Area and Regional Geology

Study Area and Regional Geology

114 Vues Download Presentation
Télécharger la présentation

Study Area and Regional Geology

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. Determining the source of saline groundwater from the Mississippi River Valley Alluvial aquiferin southeast ArkansasJustin Paul and Dr. Daniel LarsenDepartment of Earth Sciences; University of MemphisSouth-Central GSA Meeting March 17, 2014

  2. Study Area andRegional Geology Modified from Cox et al. (2013) Modified from Wikipedia

  3. Alluvial Aquifer • Quaternary sands and gravels (Ackerman, 1996) • Capped by silt and clay confining unit (Ackerman, 1996) Modified from Ackerman (1996)

  4. Occurrence of saline groundwater • Chloride condition could be due to evaporative processes in near surface (Kresse and Clark, 2008). • Cannot discount vertical migration of saline fluids along faults (Kresse and Clark, 2008). Modified from Kresse and Clark (2008)

  5. Soils • Mostly clay-rich varieties derived from backswamp deposits (Saucier, 1994) • On the whole, elevated Cl concentrations in backswamps (Kresse and Clark, 2008) Modified from Kresse and Clark (2008)

  6. Sand-blows • Cox et al. (2004&2007) • Tell us multiple things: • Paleoseismicity • Elevated pore pressures Local Faults Area I • Arkansas & Saline River Fault Zones • Area I has same orientation as regional structural grain • Area II is distinctly linear Liquefaction Fields Area II Modified from Cox et al. (2007)

  7. Brines at Depth • Jurassic age formations • Evaporative and shallow marine deposits associated with opening of Gulf of Mexico (Harry and Londono, 2004) • Basinal brines with unusual chemistry (Hanorand McIntosh, 2007) Modified from AR Geological Survey

  8. Geothermal Anomaly at Depth Modified from SMU Geothermal Laboratory Google Earth Application

  9. Hypotheses • Chloride condition due to… 1. Evapotranspiration processes whereby clay-rich soils restrict recharge and concentrate chloride in infiltrating surface water. 2. Injection of chloride-rich fluids from depth into the aquifer through faults during previous earthquakes and still migrating today. 3.Regional rivers recharging relatively chloride-rich water into the alluvial aquifer when river levels are higher than the water-table.

  10. Methods Geochemical and statistical techniques to solve this hydrogeologic problem: • Principle Component Analysis • Spatial Statistical Analysis • Hydrologic Tracer Analysis

  11. Chicot; Very Salty Principle Component Analysis Chicot; Salty Alluvial Aquifer Desha; Dilute • n= 177 • EV-1=91% of variance • Heavy negative weights on Ca, Mg, Na, Cl, SO4 • Dilute end-member • EV-2=4% of variance • Heavy positive weight on Cl • Heavy negative weights on Ca and SO4 Desha; Salty Chicot; Rel. Salty Sparta Aquifer • n= 57 • EV-1=84% of variance • Heavy negative weights on Na and Cl • EV-2=9% of variance • Heavy positive weight on Ca and Cl • Heavy negative weight on Na Both Desha; Dilute

  12. Spatial Analysis • Seeking statistical relationship between location and density of sand-blows to Cl content in groundwater Modified from Kresse and Clark (2008) and Cox et al. (2007)

  13. Hydrologic Tracer Analysis Interpretations

  14. Stable O vs Stable H

  15. Cl content vs 14C age in alluvial groundwaters Chicot ; Very Salty ; Backswamp Desha ; Dilute ; Backswamp Desha ; Salty ; Backswamp

  16. Conclusions • Using geochemistry and statistics to solve a hydrogeological problem • Methods will test vastly different hypotheses • Near-surface evaporative concentration of chloride in recharging groundwater 2. Injection of chloride-rich waters from depth through faults 3. Regional rivers recharging relatively chloride-rich water into the alluvial aquifer • Evidence suggests evap. evolved, pre-modern crustal waters mixing with fresher, younger meteoric waters

  17. Special Thanks • Tim Kresse- data • Geological Society of America- funding • U. of Memphis Dept. of Earth Sciences- support • U. of Arkansas Stable Isotope Lab- support • U. of Miss. Geology & Geo. Engineering Dept.-support • South-Central GSA- travel considerations