402-pp21 - UNIVERSITY OF SOUTH ALABAMA GY 402 Sedimentary Petrology Lecture 21 Carbonate Petrography 2 Non-skeletal Allochems Last Time Carbonate

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Unformatted text preview: UNIVERSITY OF SOUTH ALABAMA GY 402: Sedimentary Petrology Lecture 21: Carbonate Petrography 2: Non-skeletal Allochems Last Time Carbonate Tidal Flats Carbonate classification scheme (with revisions) Tidal flats (carbonate variety) Carbonate staining scheme Carbonate thin section petrography Carbonate Sedimentary Rocks Source: Prothero, D.R. and Schwab, F., 1996. Sedimentary Geology. W.H. Freeman, 575 p. Prothero, Tidal Flat Environments Source:Scholle P.A. and James, N.P. 1995. SEPM Photo CD-1. CD- Tidal Flat Petrography Cryptalgal laminations ppl 3 mm Tidal Flat Petrography ppl xn 1 mm The moral of the story is that you still have to check your thin sections under crossed polars too! Carbonate Staining Combination of potassium ferricyanide and Alizarin red-S Red/Pink: distinguishes CaCO3 from other minerals PPL 5 mm Carbonate Staining Mineral Aragonite Calcite (nonferroan) Calcite (ferroan) Magnesium calcite Dolomite Ferroan Dolomite Geochemistry CaCO3 CaCO3 Ca(Fe2+)CO3 Ca(Mg2+)CO3 CaMg(CO3)2 CaMg(Fe2+)(CO3)2 Stain color Pink to red (brown highlights) Pink to red Purple to blue Pink to red (yellow with Clayton Yellow) Not stained Turquoise Today's Agenda Carbonate Petrography 2 Carbonate "grains" (skeletal versus non-skeletal) Non-skeletal allochems Ooids Peloids Intraclasts Grapestones Carbonate "Grains" Allochems: A collective term introduced by Robert Folk (1959) for a variety of discrete and organized carbonate aggregates (or grains) that serve as the coarser constituents in limestones. This separates the "grains" from fine carbonate matrix ("micrite") and diagenetic cements ("spar"). Carbonate "Grains" Allochems: Come in many different "flavors", but we can group them into two broad divisions, Skeletal the remains of once living beasties (body fossils) Non-Skeletal chemically precipitated or inorganically produced components Non-skeletal Allochems The Great Bahamas Bank Non-skeletal Allochems Non-skeletal Allochems http://strata.geol.sc.edu/Bahamas/pages/035-North-of-Joulters-Key-Ooids-Bahamas.html Non-skeletal Allochems 1 cm http://strata.geol.sc.edu/Bahamas/pages/035-North-of-Joulters-Key-Ooids-Bahamas.html Non-skeletal Allochems Ooids: a concentrically coated, spherical allochem that forms through "inorganic" cementation on the sea floor in a wave agitated environment (0.25 to 2.0 mm) Non-skeletal Allochems Ooids: a concentrically coated, spherical allochem that forms through "inorganic" cementation on the sea floor in a wave agitated environment (0.25 to 2.0 mm) Peloids (or Pellets): a generic allochem composed of carbonate mud (micrite) irrespective of size, shape (but they are usually round to ovoid) or origin (they are commonly fossilized fecal pellets) Non-skeletal Allochems Ooids: a concentrically coated, spherical allochem that forms through "inorganic" cementation on the sea floor in a wave agitated environment (0.25 to 2.0 mm) Peloids (or Pellets): a generic allochem composed of carbonate mud (micrite) irrespective of size, shape (but they are usually round to ovoid) or origin (they are commonly fossilized fecal pellets) Intraclasts: an allochem composed of composite grains (equivalent to a rock fragment in siliciclastic terms; BUT implies on the sea floor cementation) Non-skeletal Allochems Ooids: a concentrically coated, spherical allochem that forms through "inorganic" cementation on the sea floor in a wave agitated environment (0.25 to 2.0 mm) Peloids (or Pellets): a generic allochem composed of carbonate mud (micrite) irrespective of size, shape (but they are usually round to ovoid) or origin (they are commonly fossilized fecal pellets) Intraclasts: an allochem composed of composite grains (equivalent to a rock fragment in siliciclastic terms; BUT implies on the sea floor cementation) Grapestone: another allochem composed of composite grains, but these are restricted to multiply coated groups of ooids (also implies cementation on the sea floor) Non-skeletal Allochems Ooids: a concentrically coated, spherical allochem that forms through "inorganic" cementation on the sea floor in a wave agitated environment (0.25 to 2.0 mm) PPL 1 mm Non-skeletal Allochems Ooids: a concentrically coated, spherical allochem that forms through "inorganic" cementation on the sea floor in a wave agitated environment (0.25 to 2.0 mm) Small nucleus 1 mm PPL 1 mm Non-skeletal Allochems Ooids: a concentrically coated, spherical allochem that forms through "inorganic" cementation on the sea floor in a wave agitated environment (0.25 to 2.0 mm) Large nucleus 1 mm PPL 2 mm Non-skeletal Allochems Peloids (or Pellets): a generic allochem composed of carbonate mud (micrite) irrespective of size, shape (but they are usually round to ovoid) or origin (they are commonly fossilized fecal pellets) PPL 1 mm Non-skeletal Allochems Peloids (or Pellets): a generic allochem composed of carbonate mud (micrite) irrespective of size, shape (but they are usually round to ovoid) or origin (they are commonly fossilized fecal pellets) 0.5 mm PPL 1 mm Non-skeletal Allochems Intraclasts: an allochem composed of composite grains (equivalent to a rock fragment in siliciclastic terms; BUT implies on the sea floor cementation) http://userpage.fu-berlin.de/~voelker http://userpage.fu- PPL 1 mm Non-skeletal Allochems Intraclasts: an allochem composed of composite grains (equivalent to a rock fragment in siliciclastic terms; BUT implies on the sea floor cementation) 1.5 mm PPL http://userpage.fu-berlin.de/~voelker http://userpage.fu- 1 mm Non-skeletal Allochems Grapestone: another allochem composed of composite grains, but these are restricted to multiply coated groups of ooids (also implies cementation on the sea floor) http://userpage.fu-berlin.de/~voelker 1.5 mm PPL 1 mm Non-skeletal Allochems Grapestone: another allochem composed of composite grains, but these are restricted to multiply coated groups of ooids (also implies cementation on the sea floor) 1.5 mm PPL http://www.geo.edu.ro/~sedim/Enciclopedie/C/grapest.jpg http://www.geo.edu.ro/~sedim/Enciclopedie/C/grapest.jpg 1 mm Upcoming Stuff Homework 1) Tidal flat thin sections due Thursday 2) Volcaniclastic discussion re-dues due Thursday 3) St Stephens Quarry re-dues due Friday Lab This Week Tidal flat and evaporite thin sections Next Lecture: Non-skeletal Carbonates ...
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This note was uploaded on 02/05/2012 for the course GLY 402 taught by Professor Staff during the Fall '11 term at S. Alabama.

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