Sedimentary Textures 1

Question 1

Describe aspects of sedimentary texture:

Answer 1

Sediment texture is important to understand the origin of sedimentary deposits, hydraulic conditions of transport and deposition, transport/deposition environment, weathering processes, geotechnical properties, and potential industrial applications (e.g., oil, gas).
Sedimentary texture includes grain size (average grain size and sorting) and grain shape (roundness, form, surface texture).

Question 2

Describe different methods used to measure grain size:

Answer 2

Sieving: Passing sediment through sieves with different mesh sizes.
Sedimentation/Settling: Measuring settling velocity of particles in a fluid.
Thin Section Analysis: Slicing rock thin enough for light to pass through and examining individual grains.
Laser Particle Sizers: Using laser beams to scan particles dispersed in water, measuring size and shape.

Question 3

Explain importance of grain size statistics and describe statistical methods and parameters used:

Answer 3

• Grain size statistics help characterize sediment and can be presented as weight %, volume %, or number %.
• Statistical methods include histograms, frequency curves, cumulative frequency curves (arithmetic or probability), and measures of central tendency (mean, mode, median).
• Sorting, describing the uniformity of grain sizes, is often quantified using the standard deviation (σ).

Question 4

Describe fluid characteristics relevant for sediment transport:

Answer 4

• Viscosity: Related to shear stress and the rate of deformation of a fluid.
• Density: Determines the mass of a fluid per unit volume.
• Flow velocity: Primary control on the ability of a fluid to transport sediment grains, with laminar flow (smooth and slow) and turbulent flow (complex and fast) being common mechanisms for sediment entrainment and transport.