402-pp12 - UNIVERSITY OF SOUTH ALABAMA GY 402: Sedimentary...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: UNIVERSITY OF SOUTH ALABAMA GY 402: Sedimentary Petrology Lecture 12: Mature Siliciclastic Environments Last Time 1. Recap major types of sediment & sedimentary rock 2. Recap important grain parameters 3. Cement versus matrix 4. Mature sediment/sedimentary rocks Major Sedimentary Rock Types Siliciclastic Volcaniclastic Carbonates (evaporites/chemical, non-skeletal, skeletal) Siliciclastic Sedimentary Rocks Q "Mature" rocks (mineralogically stable) Enriched in quartz and clay minerals F R Source: Blatt, H., Middleton, G and Murray, R., 1980: Origin of Sedimentary Rocks. Prentice Hill, 782 p. Blatt, Rocks. Important Parameters Grain rounding Immature Increasing transport distance Mature Important Parameters Grain sorting Low energy increasing energy of deposition High energy Important Parameters Grain size High energy Decreasing energy of deposition Low energy Mature Siliciclastic Petrography Quartz-rich (quartz arenites) Generally well rounded grains Poorly sorted to well sorted Gravel to clay sized grains XN 250 :m Matrix versus Cement Matrix: fine-grained* material deposited simultaneously with larger particles. Generally appears as darker-coloured detritus between grains Cement: a chemical precipitate between grains formed from pore-water long after deposition. Matrix versus Cement Matrix Heterogeneous Chemically impure Drapes over grains* Predates cements Generally dark in color* Cement Homogeneous Chemically pure Lines pores* Specific fabrics Multiphased Zoned * Can be confusing Hand specimens Mature siliciclastic sandstones (quartz arenite) Liesengang banding, clay and iron oxide cement Quartz and chalcedony cement 4 cm Limonite cement Thin-section Photomicrographs Quartz (overgrowth) cement ppl xn Quartz overgrowth cement 125 :m Today's Agenda 1. Factors promoting beach development 2. Beach profiles 3. Beach facies & sedimentary sections Factors controlling beach development Factors controlling beach development Steady supply of sand to the shoreline, by river, delta or longshore drift Factors controlling beach development Steady supply of sand to the shoreline, by river, delta or longshore drift Wave dominated setting (medium to high wave energy is best; low tidal energy necessary) Factors controlling beach development Steady supply of sand to the shoreline, by river, delta or longshore drift Wave dominated setting (medium to high wave energy is best; low tidal energy necessary) Stable, low gradient coastal plan and continental shelf gradient Factors controlling beach development Steady supply of sand to the shoreline, by river, delta or longshore drift Wave dominated setting (medium to high wave energy is best; low tidal energy necessary) Stable, low gradient coastal plan and continental shelf gradient 32,000 km of shoreline meet these requirements; best studied beaches are along the US eastern and Gulf coasts Wave action Wind Orbicular motion From Komar, P.D., 1998. Beach Processes and Sedimentation. Prentice Hall, New Jersey, 544p. Komar, Wave action Wave base From Komar, P.D., 1998. Beach Processes and Sedimentation. Prentice Hall, New Jersey, 544p. Komar, Overall beach dynamics From Walker, R.G. and James, N.P. (1992). Facies Models: Response to Sea Level Change. Geological Association of Canada, 409p. Response Canada, Longshore drift From Walker, R.G. and James, N.P. (1992). Facies Models: Response to Sea Level Change. Geological Association of Canada, Response Canada, 409p. Overall beach dynamics From Blatt, H, Middleton, G. and Murray, R., 1980. Origin of Sedimentary Rocks. Prentice Hill, 782 p. Blatt, Rocks. Hydrodynamic zones Sedimentary Facies From Komar, P.D., 1998. Beach Processes and Sedimentation. Prentice Hall, New Jersey, 544p. Komar, Beach Facies From Walker, R.G. and James, N.P. (1992). Facies Models: Response to Sea Level Change. Geological Response Association of Canada, 409p. , Canada Beach Facies Response From Walker, R.G. and James, N.P. (1992). Facies Models: Respons e to Canada, Sea Level Change. Geological Association of Canada , 409p. Facies distribution on beaches is a ballet between shoreline advance (progradation) and retreat. Beach change = construction-destruction Response From Walker, R.G. and James, N.P. (1992). Facies Models: Respons e to Canada, Sea Level Change. Geological Association of Canada , 409p. Beach Facies Galveston Island; a prograding beach Beach Facies & Structures From Walker, R.G. and James, N.P. (1992). Facies Models: Response to Sea Level Change. Response Geological Association of Canada, 409p. Canada, Beach Facies From Walker, R.G. and James, N.P. (1992). Facies Models: Response to Sea Response Level Change. Geological Association of Canada, 409p. Canada, Sea level as a control on beach development From Walker, R.G. and James, N.P. (1992). Facies Models: Response to Sea Level Change. Geological Association of Response Canada, 409p. , Canada Upcoming Stuff Homework 1) Grain size reports (due Thursday) 2) Mature Thin Section lab (due Thursday) Today's Lab Mature Thin Sections Next Lecture: Immature Siliciclastic Sediments Mid term (take home) exam issued (due Thursday March 10) ...
View Full Document

Ask a homework question - tutors are online