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Sedimentary Geology Geos 240 – Chapter 3-2 Sedimentary Petrology-2. Dr. Tark Hamilton Camosun College. QFL + Grain Size Prism. Provenance. Q. F. L. Dolostone Breccia. Sandstone. Provenance from Clasts & Accessory Minerals.
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Sedimentary GeologyGeos 240 – Chapter 3-2Sedimentary Petrology-2 Dr. Tark Hamilton Camosun College
Provenance Q F L
Dolostone Breccia Sandstone
Provenance from Clasts & Accessory Minerals • Conglomerates & coarse grained lithic sands afford provenance & tectonic setting to be interpreted from lithic clasts: granitic, regional metamorphics, volcanics, second cycle sediments… • Even fine sands and silts contain rare accessory minerals which are heavy, hard & chemically resistant like: zircon, baddeleyite, monazite, apatite, garnet, tourmaline, hornblende, epidote, topaz, corundum, ilmenite, native gold. These are concentrated using heavy liquids, panning or centrifugation. Zircons can even be dated. Mapping of past drainages has been accomplished for many units in the Phanerozoic section of Western Canada because of unique assemblages from each upstream shield terrane. Zirconium and titanium could be economically recovered from tar sands tailings.
Deep sea micro- & nannofossil ooze & cold carbonate vent mounds*Diagenetic carbonate cements from sub- & anaerobic bacterial processes Bio-&
The Biochemistry of Carbonates • Photo/chemosynthesis life makes hydrocarbons or carbohydrates • atmospheric carbon dioxide and water • in the presence of energy (sunlight, chemical bonds) • And enzymes or mineral substrates to catalyze reactions • Prokaryotes: Archea, Eubacteria or Eukaryotes, Plant life • 6CO2(g) + 6H2O (l) C6 H12O6 (aq) or cellulose • Some Archea (methanogens), since 4 Ga, don’t require oxygen • CO2(g) + 2H2(g) CH4 (g) or • Aerobic or anaerobic metabolism of organic molecules (food/fuel source) regenerates carbon dioxide with or without free oxygen: • CH2O (aq) + O2(g) H2CO3(aq) HCO3–(aq) + H+(aq) aerobic • CH4(aq)+ SO4‑2(aq)=> S‑2(aq)+ H+(aq) + HCO3‑(aq) + H2O(l) anoxic • Add dissolved Ca+2 and Fe+2 to make Calcite and Pyrite • Inorganic carbonate precipitation happens in evaporties and hydrothermal settings but even there closer examination usually seems to involve archaea
Limestone Components • Foraminifera • Micrite • Sparry Cemented Calcarenite
The “Godfather” of Carbonate Geology Robert Lewis (Luigi) Folk San Salvador, Bahamas June 2008 Age ~73 (Upper Holocene) (The logo on the dirty ball cap is an ad for a local backhoe company in Austin Texas)
LRMudSilty MudSandy MudMuddy Silt/SandBreccia/ Conglomerate Field Lab