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Readings from Sediments & Basins: (8:1-67)
Sedimentary Geology Geos 240 – Chapter 8 Depositional Environments Part 5 Shallow Carbonates & Evaporites Dr. Tark Hamilton Readings from Sediments & Basins: (8:1-67) Camosun College
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Bahamas Platform & Fringing Reefs
. La Habana
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Transgression & Optimal Carbonate Factory
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Continental Shelf Eastern Nicaragua
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Florida Keys: Shallow Back Reef – Lagoon – Mangrove Swamps
20 km
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The Great Barrier Reef: Cretaceous through Recent! Queensland OZ
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Lateral Progradation Bahamas Bank
Reflection Seismic Section & Interpretation
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Cross Section of Redwater Reef, Dev. NW of Edmonton flexed later
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Devonian Reef, Gyrfalcon Bluff, Banks Is
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Devonian Crinoid Reef, Princess Royal Is
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Fossiliferous Producing Dev Kee Scarp Reef Norman Wells
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Devonian Coral Reef, Norman Wells NWT
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Dev. Reef: Dolomite/Stromotoporoid Norman Wells
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Ordovician Bioherm, Niagara Falls
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Devonian Reef: Dolomitized Stromotoporoid Cairns Formation, Grassi Lakes Reef, Canmore
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Devonian Reef: Dolomitized Stromotoporoid Cairns Formation, Grassi Lakes Reef, Canmore
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Devonian Reef: Dolomitized Stromotoporoid Cairns Formation, Grassi Lakes Reef, Canmore
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Proterozoic Stromatolites, Dismal Lakes NWT
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Silurian Stromatolites, Somerset Island NWT
Supertenuous Drape Tidal Scour Algal Mound Buildup
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Sabkha DepositionalModel, Persian Gulf Arid Tidal Coast
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Ancient Tidal Limestone Facies
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Mississippian Lisburne Limestone Tidal Crossbeds Diagenetic Chert
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Ordovician Intraclast Dolomite Breccia, Somerset Is. NWT
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Silurian Ripples & Flasers Dolomites, Somerset Is. NWT
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The New Conservative Ordovician Burrow Mottled Limestone Ottawa
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Ordovician Tyndall Stone, Burrow Mottled Dolomite, Red River Fm Manitoba
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Ripups & Scours Silurian Dolomites, Somerset Is. NWT
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Transgressive Phase Rising System Tract
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Seds can come from Out of plane Regressive Phase
Falling System Tract
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C-Ord. Cow Head Turbidites, NF
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C-Ord. Cow Head Debris Flow, NF
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C-Ord. Cow Head Deformed Clast
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Anhydrite, Shale, Detrital Carbonates
Exhumed Carboniferous Facies Transition Sverdrup Basin, Ellesmere Island Sverdrup Basin Rim Bioclastic Debrites Anhydrite, Shale, Detrital Carbonates
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Evaporites & Evaporite Basins
Geographically Enclosed Water Bodies Tropics +/- 30° Latitude, descending dry air Sabkhas, Playas, Salinas, Salt Lakes Incipient Rift Basins – Triassic Margins of Atlantic Restricted Back Reef Basins: Carb’s + Anhydrite Evaporated Cratonic/Epicontinental Seas: Devonian of Alberta, Sask., Michigan & Zechstein Perm/Penn of North Sea Basin Often alternate climatically with humid clastics
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Usiglio’s Experiment: Evaporation of Sea Water & Sequence of Salts
s.g. = 1.035 Calcite Anhydrite Halite Bitterns
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Development of Evaporite Basin
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Development of Evaporite Basin
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Evaporite Minerals Dominant Evaporite Minerals include: Carbonates, Chlorides, Sulphates, Borates & Nitrates Marine systems dominantly produce Carbonates, Chlorides & Sulphates Arid Terrestrial Systems produce unusual diagenetic minerals in pore spaces and beds of Borates & Nitrates additional to the Carbonates, Chlorides & Sulphates. Additional to the unusual Continental anion Chemistry, salts of metals form some unusual brine minerals, Cu, Ni, Zn, Pb, Ag and even (NH4)+ ! Salts precipitate in inverse order depending on their solubility. (solubility in strong/odd brines is empirical) Salts in vadose zone porosity are important in soils
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Textures in Resedimented Evaporites, Italy Messinian (~5Ma) Mediterranean Basin
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Evaporite Minerals Carbonates: Mineral Formula Calcite CaCO3
Dolomite CaMg (CO3 )2 Siderite FeCO3 Natrite Na2CO3 & Natron•6(H2O) Trona Na3(CO3)(HCO3)•2(H2O) (Green River, WY; Lake Magadi, Kenya)
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Carbonate Minerals Trona Natrite
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Sandstone with Cubic Halite Casts Jurassic, Utah
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Evaporite Minerals Chlorides: Mineral Formula Halite NaCl Sylvite KCl
Carnallite KMgCl3 · 6H2O
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Chloride Minerals Sylvite Halite Hopper Crystals Carnallite Halite
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Cyclic & Crossbedded Devonian Halite, Goderich ON
Q1) Cyclic evaporation and minor recharge. Q2) Brine is denser and has more momentum than typical sea water. Pure Halite has a S.G. of 2.07, lighter than calcite or quartz. As a result, lower current velocities might produce X-bedded halites just as shallow but also in deeper, quieter water than carbonate shoals or siliciclastic bars. In what kind of Basin would “Cyclic Halite” beds form? In what sort of flow regime would Halite X-beds form?
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Evaporite Minerals Sulphates: Mineral Formula Anhydrite CaSO4
Gypsum CaSO4· 2H2O Langbeinite K2Mg2(SO4)3 Polyhalite K2Ca2Mg(SO4)4 · 2H2O Kieserite MgSO4· H2O Kainite KMg(SO4)Cl · 3H2O
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Interbedded Gypsum & Calcsiltite, Silurian Somerset Island
? Solutional Collapse
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Interbedded Anhydrite & Shale Ellesmere Island
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Sulphate Minerals Polyhalite Langbeinite Kieserite Kainite
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Evaporite Minerals Nitrates: Mineral Formula Niter KNO3
Nitratine NaNO3· 2H2O Nitrocalcite Ca(NO3)2 · 4H2O Nitrobarite Ba(NO3)2 Gerhardtite Cu2(NO3)(OH)3 Some of these were done from memory so you may wish to check Mindat.org
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Nitrate Minerals Niter Nitratine Nitrobarite Gerhardtite Nitrocalcite
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Borax Mines Death Valley CA
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Evaporite Minerals Borates: Mineral Formula Boracite Mg3[ClB7O13 ]
Borax Na2[B4O7]2 · 10H2O Colemanite Ca[B3O4(OH)3] · 3H2O HydroBoracite CaMg [B3O4(OH)3]2 · 3H2O Larderellite (NH4 )B5O6(OH)4 Tincalconite Na2[B4O7] · 5H2O Ulexite NaCa[B5O6(OH)6]· 5H2O Some of these were done from memory so you may wish to check Mindat.org
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Borate Minerals Boracite Colemanite Hydroboracite Borax Larderellite
Ulexite Tincalconite
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Salar de Atacama, Antofagasta Chile
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The End: Chapter 8 Part 5!
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