402-pp4 - UNIVERSITY OF SOUTH ALABAMA GY 402: Sedimentary...

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Unformatted text preview: UNIVERSITY OF SOUTH ALABAMA GY 402: Sedimentary Petrology Lecture 4: Fluid Flow and Sediment Entrainment Last Time 1. 2. 3. 4. Why bother with sedimentary classification? Siliciclastic sedimentary rock schemes Volcaniclastic sedimentary rock schemes Carbonate rock schemes Sedimentary Rock Classification Particle type specific 1. Siliciclastic sedimentary rocks (Quartz, Feldspars, Clays, Lithic Fragments, Micas, etc.) 2. Shales and Mudstones (grain to "matrix" content) 3. Volcaniclastic sedimentary rocks (vitric fragments and ash, phenocrysts, lithics ) 4. Carbonate sedimentary rocks (skeletal grains, non-skeletal grains and matrix) 5. Organic sedimentary rocks (kerogen content, coal grade etc.) Siliciclastic Sedimentary Rocks (Arenites) Source: Blatt, H., Middleton, G and Murray, R., 1980: Origin of Sedimentary Rocks. Prentice Hill, 782 p. Blatt, Rocks. Volcaniclastic Sedimentary Rocks Source: Carozzi, A.V., 1993. Sedimentary Petrology. Prentice Hill, 263p. Carbonate Sedimentary Rocks Source: Prothero, D.R. and Schwab, F., 1996. Sedimentary Geology. W.H. Freeman, 575 p. Prothero, Today's Agenda 1. 2. 3. 4. 5. Six modes of sediment movement Real simple fluid dynamics (ideal conditions) Initiation of sediment movement Nasty mathematical relationships (Shield's Diagram) Useful empirical relationships (Hjulstrom's Diagram) Sediment Motion Sediment Motion Rest (no movement) Roll Slide Saltation ("bouncing") Suspension Mass flow (viscous flow) What is Viscosity? (from Collinson, J.D. and Thompson, D.B. 1982. Sedimentary Structures. George Allen and Unwin 194p) Collinson, Allen Modes of Viscous Flow (from Collinson, J.D. and Thompson, D.B. 1982. Sedimentary Structures. George Allen and Unwin 194p) Collinson, Allen Real Fluid Flow (from Collinson, J.D. and Thompson, D.B. 1982. Sedimentary Structures. George Allen and Unwin 194p) Collinson, Allen Real Fluid Flow (from Collinson, J.D. and Thompson, D.B. 1982. Sedimentary Structures. George Allen and Unwin 194p) Collinson, Allen Real Fluid Flow (from Collinson, J.D. and Thompson, D.B. 1982. Sedimentary Structures. George Allen and Unwin 194p) Collinson, Allen Collinson, Allen (from Collinson , J.D. and Thompson, D.B. 1982. Sedimentary Structures. George A llen and Unwin 194p) Real Fluid Flow This cartoon is critical and is the basis for grain size analysis! Collinson, Allen (from Collinson , J.D. and Thompson, D.B. 1982. Sedimentary Structures. George A llen and Unwin 194p) Real Fluid Flow Enter Stoke's Law This cartoon is critical and is the basis for grain size analysis! Stoke's Law Vg = gd2(F-D) 18: Stoke's Law Vg = gd2(F-D) 18: g = gravitational constant (9.8 m/s2) Stoke's Law Vg = gd2(F-D) 18: g = gravitational constant (9.8 m/s2) d = particle size diameter (mm) Stoke's Law Vg = gd2(F-D) 18: g = gravitational constant (9.8 m/s2) d = particle size diameter (mm) F = grain density (g/cm3) Stoke's Law Vg = gd2(F-D) 18: g = gravitational constant (9.8 m/s2) d = particle size diameter (mm) F = grain density (g/cm3) D = fluid density Stoke's Law Vg = gd2(F-D) 18: g = gravitational constant (9.8 m/s2) d = particle size diameter (mm) F = grain density (g/cm3) D = fluid density : = dynamic fluid viscosity Stoke's Law Vg = gd2(F-D) 18: g = gravitational constant (9.8 m/s2) d = particle size diameter (mm) F = grain density (g/cm3) D = fluid density : = dynamic fluid viscosity Vg = settling velocity Stoke's Law Vg = gd2(F-D) 18: Stoke's Law Vg = gd2(F-D) 18: g is a constant Stoke's Law Vg = gd2(F-D) 18: g is a constant F = grain density (not a true constant, but...) Stoke's Law Vg = gd2(F-D) 18: g is a constant F = grain density (not a true constant, but...) D = fluid density (not a true constant, but...) Stoke's Law Vg = gd2(F-D) 18: g is a constant F = grain density (not a true constant, but...) D = fluid density (not a true constant, but...) : = dynamic fluid viscosity (not a true constant, but...) Stoke's Law Vg . kd2 Vg is proportional to grain size Stoke's Law Vg . kd2 Vg is proportional to grain size or, alternatively, grain size is proportional to settling velocity Stoke's Law (Graphic Representation) 103 102 log Vg (cm/s) 101 100 . Vg kd 2 al) ide ( 10-1 10-2 10-4 10-3 10-2 10-1 100 101 102 103 log d (mm) Actual settling characteristics 103 102 log Vg (cm/s) observed) Reality ( 101 100 10-1 10-2 10-4 10-3 10-2 10-1 100 101 102 103 log d (mm) Impact Law (Graphic Representation) 103 102 log Vg (cm/s) 101 100 10-1 10-2 Vg = q 1.33F-D D 10-4 10-3 10-2 10-1 100 101 102 103 log d (mm) Impact Law (Graphic Representation) 103 102 log Vg (cm/s) 101 100 The result of turbulence and grain interaction as large grains fall through a fluid 10-1 10-2 Vg = q 1.33F-D D 10-4 10-3 10-2 10-1 100 101 102 103 log d (mm) Impact Law (Graphic Representation) 103 102 log Vg (cm/s) 101 100 10-1 10-2 Vg = q 1.33F-D D 10-4 10-3 10-2 10-1 100 101 102 103 log d (mm) Impact Law (Graphic Representation) 103 102 log Vg (cm/s) 101 100 10-1 10-2 Vg = q 1.33F-D D 10-4 10-3 10-2 10-1 100 101 102 103 log d (mm) Impact Law (Graphic Representation) 103 102 log Vg (cm/s) ) observed Reality ( 101 100 10-1 10-2 10-4 10-3 10-2 10-1 100 101 102 103 log d (mm) Composite curves (Stoke's + Impact) 103 102 log Vg (cm/s) w Impact La 101 100 Sto k aw sL e' 10-1 10-2 10-4 10-3 10-2 10-1 100 101 102 103 log d (mm) Composite curves (Stoke's + Impact) 103 102 log Vg (cm/s) w Impact La 101 100 Sto k aw sL e' 10-1 10-2 Laminar flow 10-4 10-3 10-2 10-1 100 Turbulent flow 101 102 103 log d (mm) Composite curves (Stoke's + Impact) 103 102 log Vg (cm/s) ) observed Reality ( 101 100 10-1 10-2 10-4 10-3 10-2 10-1 100 101 102 103 log d (mm) Settling Curve (Graphic Representation) 103 102 log Vg (cm/s) 101 100 10-1 Settling Curve 10-2 (AKA Rubey's Curve) 10-4 10-3 10-2 10-1 100 101 102 103 log d (mm) Grain Size Analysis Grain Size Analysis At 23 oC, all sand and gravel will fall at least 10 cm in 4 minutes, 28 seconds Grain Size Analysis At 23 oC, all silt, sand and gravel will fall at least 7.5 cm in 5 hours, 43 minutes Grain Size Analysis Sand and gravel are determined via sieving sand fractions: vc, c, m, f, vf, gravel fractions: not routinely done Grain Size Analysis Sand and gravel are determined via sieving sand fractions: vc, c, m, f, vf, gravel fractions: not routinely done Analysis done using simple excel spread sheet (will be available on departmental computers and/or e-mailed to you) Grain Size Analysis Grain Size Analysis Grain Size Analysis Grain Size Analysis wt% retained per sieve 20.00 15.00 25.00 35.00 30.00 40.00 10.00 5.00 0.00 gravel vc sand c sand m sand grain size f sand vf sand coarse silt fine silt clay Grain Size Analysis Real Fluid Flow & "Entrainment" Sorry, but we have to talk a bit about physics (and about how airplanes fly) Real Fluid Flow & "entrainment" Entrainment is synonomous with: "initiation of grain movement" (from Blatt, H, Middleton, G. and Murray, R., 1980. Origin of Sedimentary Rocks. Prentice Hill, 782 p) Blatt, Rocks. Sediment Entrainment Shear Velocity (from Blatt, H, Middleton, G. and Murray, R., 1980. Origin of Sedimentary Rocks. Prentice Hill, 782 p) Blatt, Rocks. Sediment Entrainment (Shield's Diagram) (from Blatt, H, Middleton, G. and Murray, R., 1980. Origin of Sedimentary Rocks. Prentice Hill, 782 p) Blatt, Rocks. Sediment Entrainment (Hjulstom's Diagram) (from Blatt, H, Middleton, G. and Murray, R., 1980. Origin of Sedimentary Rocks. Prentice Hill, 782 p) Blatt, Rocks. Sediment Entrainment (Hjulstom-Sundborg Diagram) (from Collinson, J.D. and Thompson, D.B. 1982. Sedimentary Structures. George Allen and Unwin 194p) Collinson, Allen Sediment Entrainment (Hjulstom-Sundborg Diagram) (from Collinson, J.D. and Thompson, D.B. 1982. Sedimentary Structures. George Allen and Unwin 194p) Collinson, Allen Sediment Entrainment (Hjulstom-Sundborg Diagram) Entrainment Deposition (from Collinson, J.D. and Thompson, D.B. 1982. Sedimentary Structures. George Allen and Unwin 194p) Collinson, Allen Sediment Entrainment (Hjulstom-Sundborg Diagram) Traction Suspension Deposition (from Collinson, J.D. and Thompson, D.B. 1982. Sedimentary Structures. George Allen and Unwin 194p) Collinson, Allen Sediment Entrainment (Hjulstom-Sundborg Diagram) Grain size = a (from Collinson, J.D. and Thompson, D.B. 1982. Sedimentary Structures. George Allen and Unwin 194p) Collinson, Allen Sediment Entrainment (Hjulstom-Sundborg Diagram) Entrainment = ae Grain size = a (from Collinson, J.D. and Thompson, D.B. 1982. Sedimentary Structures. George Allen and Unwin 194p) Collinson, Allen Sediment Entrainment (Hjulstom-Sundborg Diagram) Entrainment = ae Entrainment velocity = Vae Grain size = a (from Collinson, J.D. and Thompson, D.B. 1982. Sedimentary Structures. George Allen and Unwin 194p) Collinson, Allen Sediment Entrainment (Hjulstom-Sundborg Diagram) Suspension = as Grain size = a (from Collinson, J.D. and Thompson, D.B. 1982. Sedimentary Structures. George Allen and Unwin 194p) Collinson, Allen Sediment Entrainment (Hjulstom-Sundborg Diagram) Suspension velocity = Vas Suspension = as Grain size = a (from Collinson, J.D. and Thompson, D.B. 1982. Sedimentary Structures. George Allen and Unwin 194p) Collinson, Allen Sediment Entrainment (Hjulstom-Sundborg Diagram) Settling = ad Settling velocity = Vad Grain size = a (from Collinson, J.D. and Thompson, D.B. 1982. Sedimentary Structures. George Allen and Unwin 194p) Collinson, Allen Upcoming Stuff Homework 1) Writing Assignment 2 (Grain Size hypothesis/methods): Due Today 2) Writing Assignment 1-redo (Paper Structure): Due Today 3) Grain Size Analysis: schedule your column run Today's Lab Grain Size Analysis Next Lecture: Bedform Development ...
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