402-pp19 - UNIVERSITY OF SOUTH ALABAMA GY 402 Sedimentary...

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Unformatted text preview: UNIVERSITY OF SOUTH ALABAMA GY 402: Sedimentary Petrology Lecture 19: Deltas Last Time 2) Volcaniclastic Sedimentary Rocks Origin of volcaniclastic sedimentary rocks Classification of volcaniclastic sed. rocks Thin section petrography Volcaniclastic sedimentary rocks Air fall coarse fine Volcaniclastic sedimentary rocks tephra ignimbrite tephra ignimbrite Volcaniclastic Petrography Carozzi, Source: Carozzi , A.V., 1993. Sedimentary Petrology. Prentice Hill, 263p. Today's Agenda Deltas Deltas defined Classification of Deltas Deltaic Sedimentology Deltas Delta: siliciclastic depositional environments formed at the point where rivers meet bodies of water http://www.tulane.edu/~sanelson/images/delta.gif http://www.tulane.edu/~sanelson/images/delta.gif Deltas The first depositional environment described in the historical record Greeks (Anthony) when visiting the Egyptians (Cleopatra) noticed that the Nile flowed over a broad triangular shaped area before it flowed into the Mediterranean Sea. http://www.sas.upenn.edu/earth/assets/images/photos/GRLFig1.jpg Deltas This area resembled the Greek letter (delta) http://www.sas.upenn.edu/earth/assets/images/photos/GRLFig1.jpg Deltas Deltas come in several different morphologies that are controlled by the interaction between 3 major processes: 1) Wave Energy 2) Tidal Energy 3) River Input http://clasticdetritus.com/category/delta/ http://clasticdetritus.com/category/delta/ Deltas The balance between the 3 processes is unique for each delta. End member deltas are characterized by distinct morphologies. Delta Morphology River-dominated Wave-dominated Tide-dominated http://www.geology.pitt.edu/ http://www.geology.pitt.edu/ Deltas http://w3.salemstate.edu/~lhanson/gls214/gls214_deltas.html http://www.sas.upenn.edu/earth/assets/images/photos/GRLFig1.jpg Deltaic Processes When sediment-laden river water flows into the sea, it floats because freshwater is less dense than seawater. Deltaic Processes When sediment-laden river water flows into the sea, it floats because freshwater is less dense than seawater. Deltaic Processes However, sediment, being denser, still settles out of the water column. Coarse stuff (sand) is deposited close to the shoreline. Fine stuff (mud) is deposited further seaward Fining Deltaic Processes The result is a fan-shaped, laterally-fining deposit... Deltaic Processes ... that is characterized by a broad coarsening-upward signature. Walker, R.G., 1979. Facies Models, Geoscience Canada Reprint Series 211 p., Deltaic Facies Deltas consist of several key facies Prodelta Distributary Mouth Bar Channel Levees Crevasse Splays Flood Plain Walker, R.G., 1979. Facies Models, Geoscience Canada Reprint Series 211 p., Deltaic Facies Deltas consist of several key facies Prodelta Distributary Mouth Bar Channel Levees Crevasse Splays Flood Plain Walker, R.G., 1979. Facies Models, Geoscience Canada Reprint Series 211 p., Deltaic Facies Distributary Mouth Bar http://clasticdetritus.com/category/delta/ http://clasticdetritus.com/category/delta/ Walker, R.G., 1979. Facies Models, Geoscience Canada Reprint Series 211 p., Deltaic Facies Flood plain http://clasticdetritus.com/category/delta/ http://clasticdetritus.com/category/delta/ Chalk Board Walker, R.G., 1979. Facies Models, Geoscience Canada Reprint Series 211 p., Delta Facies One of the coolest things about deltas is that centers of deposition (active delta lobes), periodically shift http://www.uwgb.edu/DutchS/graphic0/geomorph/missdlt.gif Delta Facies Resulting is rapid shifts in facies distribution http://www.geology.pitt.edu/ http://www.geology.pitt.edu/ Delta Facies Another excellent petroleum exploration target! http://www.geology.pitt.edu/ http://www.geology.pitt.edu/ Delta Sections Upper delta plain http://www.geology.pitt.edu/ Delta Sections Lower delta plain section (coarsening-upward) http://www.geology.pitt.edu/ http://www.geology.pitt.edu/ Delta Sections Lower delta plain section (with crevasse splay) http://www.geology.pitt.edu/ http://www.geology.pitt.edu/ Delta Sections End member classifications Walker, R.G., 1979. Facies Models, Geoscience Canada Reprint Series 211 p., GY 305 Plug Wire line (electric) logs are used by the petroleum companies to distinguish subsurface lithology Spontaneous potential (self potential); most useful as a basic tool to distinguish lithology (sandstone versus shale) Including fining-upward and coarsening-upward sequences http://www.spwla.org/library_info/glossary/reference/glosss/images/glsp85f1.gif http://www.spwla.org/library_info/glossary/reference/glosss/images/glsp85f1.gif GY 305 Plug Wire line (electric) logs are used by the petroleum companies to distinguish subsurface lithology Spontaneous potential (self potential); most useful as a basic tool to distinguish lithology (sandstone versus shale) Including fining-upward and coarsening-upward sequences http://www.gomr.mms.gov/images_opt/graphics/re/sp.gif http://www.gomr.mms.gov/images_opt/graphics/re/sp.gif Delta Model http://www.geology.pitt.edu/ http://www.geology.pitt.edu/ Delta Model http://www.geology.pitt.edu/ http://www.geology.pitt.edu/ Upcoming Stuff Homework 1) Volcaniclastic thin section lab due Today 2) Cementation discussion re-dues due Today 3) Moscow Landing references re-dues due Tomorrow Lab This Week Volcaniclastics lab Next Lecture: Evaporites and Tidal Flat Carbonates ...
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