Sedimentary Rocks

1. Sedimentary Rocks Deposited on or Near Surface of Earth by Mechanical or Chemical Processes

2. What Rocks Tell Us

3. Types of Sedimentary Rock • Clastic (terrigenous or detrital) • Conglomerate or Breccia • Sandstone • Siltstone • Shale • Chemical/biochemical • Evaporites • Carbonate sedimentary rocks (limestones and dolostone) • Siliceous sedimentary rocks • Organic (coals) • Other - ironstones

4. Sedimentary Rocks are the Principal Repository for Information About the Earth’s Past Environment Depositional environments in ancient sediments are recognized using a combination of sedimentary facies, sedimentary structures and fossils

5. Environmental Clues in Sedimentary Rocks • Grain Size - Power of Transport Medium • Grading - Often Due to Floods • Rounding • Sorting • Cross-bedding - Wind, Wave or Current Action } Transport, Reworking

6. Environmental Clues in Sedimentary Rocks • Fossils • Salt Water - Corals, Echinoderms • Fresh Water - Insects, Amphibians • Terrestrial - Leaves, Land Animals • Color And Chemistry • Red Beds - Often Terrestrial • Black Shale - Oxygen Poor, Often Deep Water • Evaporites – Arid Climates

8. Clastic Rocks Made of Fragmentary Material Deposited by Water (Most Common) Wind Glacial Action Gravity Biochemical Sedimentary Rocks Evaporation Precipitation Biogenic Sediments Sedimentary Rocks

9. Clasts (larger pieces, such as sand or gravel) • Clasts and matrix (labelled),and iron oxide cement (reddish brown color)

10. Gravel: Grain size greater than 2 mm • If rounded clasts = conglomerate • If angular clasts = breccia Terrigenous (also called detrital or clastic) • Terrigenous sedimentary rocks are classified according to their texture (grain size): Gravel: Grain size greater than 2 mm 1. If rounded clasts = conglomerate 2. If angular clasts = breccia

11. Sandstones • Conglomerates • Breccia Rounded fragments Angular fragments

12. CLASTIC ROCKS • Formed from broken rock fragments weathered and eroded by river, glacier, wind and sea waves. These clastic sediments are found deposited on floodplains, beaches, in desert and on the sea floors. (mudstone) Clastic rocks solidify • Clastic rocks are classified on the basis of the grain size: conglomerate, sandstone, shale etc.

13. Clastic Rocks Classified by: • Grain Size • Grain Composition • Texture

14. Degree of roundness helps in knowing the distance of transportation (method of erosion) • Angular clasts- short distance transport from the source • Rounded clasts- long distance transport

15. Sediment Sizes and Clastic Rock Types Sedimentary rocks made of silt- and clay-sized particles are collectively called mudrocks, and are the most abundant sedimentary rocks.

16. Bedding or Stratification • Almost Always Present in Sedimentary Rocks • Originally Horizontal • Tilting by Earth Forces Later • Variations in Conditions of Deposition • Size of Beds (Thickness) • Usually 1-100 Cm • Can Range From Microscopic to 50m

17. GRADED BEDDING Fine gravelly lithounit Medium-coarse sandy lithounit (cross stratified)

18. Laminated layers of fine silt and clay Cross-stratified sst. Paleo-flow from right to left

19. Ripple marks

20. Mud cracks Biogenic structures Foot prints

21. Alteration Limestone - Dolomite Plagioclase – Albite Recrystallization Limestone Diagenesis • Compaction • + • Cementing • Quartz • Calcite • Iron Oxide • Clay • Glauconite • Feldspar Diagenesis is any chemical, physical, or biological change undergone by a sediment after its initial deposition and during and after its lithification.

22. CementationClastic particles ranging from silt-size to boulder-size may be deposited on the sea floor.  As they are buried, ion-laden sea water may deposit minerals in the porespaces between the grains, thus effectivelycementing them together.  By this process the sediments become rocks such as siltstone, sandstone and conglomerate. CompactionClastic particles smaller than silt, such as mud are deposited on the sea floor.  As they are buried, the weight of overlying sediments presses downward on the mud particles and compacts them, resulting in the formation of rocks such as claystone,mudstone or shale.

23. TYPES OF SEDIMENTARY ROCKS Clastic rocks Chemical & Organic rocks • Sandstones • Conglomerates • Breccia • Shale/mudstones Carbonate rocks Organic rocks Form due to decomposition of organic remains under temperature and pressure eg. Coal/Lignite etc. Form basically from CaCO3 – both by chemical leaching and by organic source (biochemical) eg. Limestone; dolomite Evaporites rocks These rocks are formed due to evaporation of saline water (sea water) eg. Gypsum, Halit (rock salt)

24. Evaporites -Water Soluble Halite Gypsum Calcite Precipitates Example: Ca(sol'n) + SO4 (Sol'n) = CaSO4 Gypsum Limestone Iron Formations Alteration After Deposition Dolomite Biogenic Sediments Limestone - Shells, Reefs, Etc. Organic Remains Coal Petroleum Chemical Sediments

25. Gypsum EVAPORITIC ROCKS These rocks are formed within the a depositional basin from chemical substances dissolved in the seawater or lake water. Halite (NaCl) CaSO4.2H20

26. Economic importance of Evaporites • SALT:other then daily use of salt for cooking, it is used • For production of Paper, • Soap • Detergents • Antiseptics • As chemical for dyeing etc. • GYPSUM:is used for plaster and in manufacturing construction materials.

27. Biogenic Sediments • Chalk: which is made up of foraminefera is very fine grained Non-Clastic Sedimentary Particles IBroken fragments of calcite,   mostly from algae.Shallow  sub tidal sediments from the Yucatan, Holocene.   Chalk Largest fragments are about  1 mm in length.

28. Biogenic Sediments Non-Clastic Sedimentary Particles Broken shell fragments of calcite frombivalve molluscs.  These shell fragments accumulated on a beach and are cemented together.  This rock  is almost100 percent shell fragments,and is therefore called a coquina.Largest fragments about 2 cm in length.

29. CARBONATE ROCKS • Limestone: It is a non-clastic rock formed either chemically or due to precipitation of calcite (CaCO3) from organisms usually (shell).  These remains will result in formation of a limestone. • Limestones formed by chemical precipitation are usually fine grained, whereas, in case of organic limestone the grain size vary depending upon the type of organism responsible for the formation • Fossiliferous Limestone: which medium to coarse grained, as it is formed out of cementation of Shells.

30. COALS: Organic Remains • Coals are carbon-rich rocks that are composed of the altered remains of woody plant debris. • The two principal types of coals are: • lignite (brown coal): composed • of loosely bound (friable) organic • detritus, including some clearly • recognizable plant remains • bituminous coal: highly compacted • black coal composed of • recrystallized carbon

31. Coal Seams, Utah

32. Coal Formation • Delta, continental environments • Carbonized Woody Material • Often fossilized trees, leaves present

33. Plant Fragments Are Often Visible in Coal

34. Characteristics and names of some common clastic sedimentary rocks. Particle Size Rock Name Rock Characteristics mud(see below) Shale smooth feel, layered appearance   mud (mud sized particles: < 0.063 mm) Mudstone  smooth feel, massive to layer silt(silt sized particles:0.063 - 0.004 mm) Siltstone slightly gritty feel, may have layered appearance sand(sand-sized particles:0.0625-2.0 mm) Sandstone rough gritty feel, constituent grains clearly visible, including quartz, feldspar, other minerals, and rock fragments.  granules, pebbles, cobbles, boulders (granule to bouldersized particles:2 mm - > 256 mm) Conglomerate large rounded fragments composed of older rock materials granules, pebbles, cobbles, boulders (granule to boulder sized particles:2 mm - > 256 mm) Breccia large angularfragments composed of older rock materials

35. Characteristics of common non-clastic sedimentary rocks that will not react with dilute HCl. Grain size Rock Name Rock Characteristics very fine grained:can't see constituent particles with naked eye Chert   hard, scratches glass, typically white, green, or red; tends to haveconchoidal fracture  variable grain size Rock Gypsum  soft, can be scratched with fingernail; may be translucent or opaque

36. Characteristics of common non-clastic sedimentary rocks that will react with dilute HCl. Grain Size Rock Name Rock Characteristics very fine grained, can't make out particles with naked eye  Chalk Pure white, powdery, light-weight, will write on sidewalks or walls  variable in grain size Limestone  dense and soft, with a crystalline or dull (earthy) luster medium grained, particles commonly visible with naked eye Coquina fragments of fossils, usually shells of invertebrates variable in grain size Fossil Limestone dense and soft, may be crystalline or dull, with visible fossils, such as snail or clam shells or other taxa 

37. Sedimentary Rock Review Of  Sedimentary ProcessesThis chart is a review of the various steps  involved in the formation of sedimentary rocks that have been discussed above.

39. Landforms Associated with Sedimentary Rocks Mesa • Flat-topped hill capped with hard rock Cuesta • Gently-tilted layer of hard rock: Door Peninsula • The gentle upper slope, on top of the layer is called the dip slope Hogback • A sharp ridge of hard rock, edge of a steeply-dipping layer

40. Mesas, Utah

41. Grandfather Bluff, Wisconsin

42. Cuestas, Wyoming

43. A Hogback, Wyoming

44. Flatirons, Boulder, Colorado

45. Garden of the Gods, Colorado