1. Sediment/Rock Classification Sediments/rocks classified according to grain size & composition. Sediments/rocks classified according to grain size & composition. What is size? What is size? Several scales proposed Several scales proposed Udden-Wentworth is geometric (1,2,4,8,16) Krumbein = phi scale; phi=-log2S Present data graphically The greater the distance of transport the smaller the grain size. The greater the distance of transport the smaller the grain size. Caution. Grain size may reflect what is available to be transported Caution. Grain size may reflect what is available to be transported Gravel Sand Silt Clay

2. Grain Rounding Roundness = curvature of corners of grains Roundness = curvature of corners of grains Have angular to well-rounded Have angular to well-rounded The rounder the grain, the greater the distance of transport The rounder the grain, the greater the distance of transport Rounded quartz grains imply many cycles of uplift, erosion, deposition Rounded quartz grains imply many cycles of uplift, erosion, deposition Beach and desert better rounded than river/glacial seds Beach and desert better rounded than river/glacial seds Large grains round fastest Large grains round fastest

3. Grain Sorting Measure of grain size distribution Measure of grain size distribution Indicate effectiveness of depositional medium in separating grains of diff sizes Sorting depends on such factors as depositional mechanism, rk type Sorting depends on such factors as depositional mechanism, rk type Poor sorting usually means limited transport Poor sorting usually means limited transport Better sorting usually means greater distance of transport Better sorting usually means greater distance of transport Rivers are good examples Rivers are good examples Used to distinguish seds of dif. env. Used to distinguish seds of dif. env.

4. Fabric Fabric/grain alignment Fabric/grain alignment –may indicate bedding Results from grain transport--e.g. wind, water Results from grain transport--e.g. wind, water Lack of grain alignment also important Lack of grain alignment also important

5. Matrix Is finer material between grains Is finer material between grains grains floating in matrix = matrix supported grains floating in matrix = matrix supported grains in contact = framework/grain-supported grains in contact = framework/grain-supported Lack of Matrix Lack of Matrix probably removed by wind/water currents probably removed by wind/water currents Presence of matrix Presence of matrix reflects transport medium reflects transport medium e.g. debris flow e.g. debris flow

6. Textural Maturity Immature = lots of matrix, poor sorting, angular grains Immature = lots of matrix, poor sorting, angular grains Mature = little matrix, mod-good sorting, well rounded Mature = little matrix, mod-good sorting, well rounded Supermature = no matrix, v. good sorting, well rounded Supermature = no matrix, v. good sorting, well rounded Provides clue to depositional process Provides clue to depositional process persistent currents = more mature seds persistent currents = more mature seds immature seds = fluvial and glacial immature seds = fluvial and glacial more mature = desert, beach, shallow marine more mature = desert, beach, shallow marine

7. Compositional Maturity Compositionally mature = predominantly quartz Compositionally mature = predominantly quartz Unstable minerals removed during transport Unstable minerals removed during transport B. Compositionally immature = labile constituents and quartz B. Compositionally immature = labile constituents and quartz

8. Cement Holds rock together--lithifies Holds rock together--lithifies could be clay, silica, calcium carbonate could be clay, silica, calcium carbonate clay looks like mud clay looks like mud quartz usually clear to white, harder than calcite quartz usually clear to white, harder than calcite calcite calcite

9. Depositional Environments and Grain Size Low energy environments such as lakes and deep oceans consist of muds/clay Low energy environments such as lakes and deep oceans consist of muds/clay High energy environments such as rivers and beaches consist mostly of gravel and sand High energy environments such as rivers and beaches consist mostly of gravel and sand

10. Sedimentary Environments & Transporting Agents

11. Color of Mudrocks: Green-oygenated environment Black-Organic-rich, low oxygen

12. Southern California Shelf

13. SEDIMENT DISTRIBUTION