Deposition and diagenesis

(2 days total for listed modules)

Messinian gypsum, Sicily

Deposition and diagenesis

Evaporite beds are deposited and then altered, with characteristic textures indicating the original hydrological setting and ocean chemistry, as well as the various diagenetic fluids crossflows experienced during burial, re-equilibration and uplift.

        Code #    Topic

  • 1000.01    Evaporation vs. cryogenesis
  • 1000.02    Depositional textures
  • 1000.03    Diagenetic textures
  • 1000.04    Gypsum and anhydrite
  • 1000.05    Halite and trona
  • 1000.06    Saline clay authigenesis

Cane Creek pans, Utah

Brine Evolution

Every evaporite sequence mineralogy and daughter product is controlled by brine evolution pathways. This evolution is preserved in brine inclusion chemistries and typical isotopic signatures (S, O, C, Cl). Marine evaporite series are controlled by changes in ionic proportions of seawater over time.

         Code #    Topic

  • 1025.01     Marine, nonmarine & climate
  • 1025.02     Inclusion chemistries
  • 1025.03     Isotopic signatures
  • 1025.04     Surface & nearsurface brines
  • 1025.05     Subsurface & metamorphic brines

 

Basins over time, eustasy & tectonics

For large-scale evaporite geosystems, the present offers a limited sampling of broader evaporite associations in the past. This reflects the limited climatic and tectonic spectrum seen in today’s evaporites. Past systems were more significant with a much wider range of depositional settings.

         Code #     Topic

  • 1050.00     Eustasy, greenhouse and icehouse
  • 1050.01      Continental (lacustrine) basins
  • 1050.02      Marine-margin (platform) basins
  • 1050.03      Ancient basinwide systems
  • 1050.04      Plate tectonic controls
  • 1050.05      Basin evolution across time

Vanished evaporites

Once deposited, evaporite units are susceptible to alteration and dissolution. Karst and breccia are reliable indicators of this process, along with nodules and replacement textures. Often unrecognized, there are widespread sub-surface indicators of former evaporites where thick sequences of stratabound and halokinetic salt once were.

 

         Code #    Topic

  • 1075.01      How and where salts dissolve
  • 1075.01      Saline karst, present & past
  • 1075.02      Breccias, which are the salty ones?
  • 1075.03      Nodules & evaporite pseudomorphs
  • 1075.04      Indicators of fluid pathways
  • 1075.05      Burial salts come and go.

 

Naica gypsum, Mexico

 

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