Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Earth Systems 3209 Unit: 3 Earth’s Materials Reference: Chapters 2, 3, 6, 7; Appendix A & B

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Clastic Sedimentary Rocks Unit 3: Topic 4.3 Focus on...  i  identifying the different sediments that make up different clastic sedimentary rocks.  describing how sediment particle size, sorting and shape can be used to classify clastic sedimentary rocks.

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador  Consist of solid particles which results when physical weathering breaks down rocks. The weathered products include pebbles, sand, silt and clay.  These rocks usually form in water environments such as: rivers, lakes, oceans, but can also form in deserts.  Geologist use particle size to distinguish between clastic sedimentary rocks, as seen in the table below: Clastic Sedimentary Rocks – Particle Size Particle NameSediment NameRock Name Boulders/ Pebbles Gravel RoundConglomerate AngularBreccia Sand Sandstone SiltMudSiltstone ClayMudShale

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador  This figure shows how clastic sediment of various sizes will, after compaction and cementation, form different types of clastic/detrital sedimentary rocks.  The process of sediment turning into rock is called lithification. Sediment – Particle Size

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Current Velocity vs. Particle Size  The greater the current velocity the greater the size of particles transported.  Therefore, as current velocity decreases, the particle size transported decreases.  This correlates with the types of clastic sedimentary rocks that result in a horizontal segment. Transportation of Clastic Sediments

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Size Sorting Size Distribution Sorting Coarse- grained Medium-grained Fine-grained High Velocity Low Velocity Moderate velocity Conglomerate/Brecciasandstoneshale Transportation of Clastic Sediments siltstone

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Sorting  Degree of similarity in particle size.  Clastic sedimentary rocks can be well-sorted or poorly-sorted; however, sorting does not apply to chemical sedimentary rocks. Very poorly-sortedVery well-sortedmoderately sorted Transportation of Clastic Sediments

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Another example: Well-sortedPoorly-sorted Transportation of Clastic Sediments

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador angularintermediaterounded Shape  Degree of roundness Transportation of Clastic Sediments

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador  Particle shape is the distinguishing factor when distinguishing between conglomerate and breccia.  Both contain similar sized particles, ex. pebbles/gravel.  Particle shape is determined by the degree of transportation.  Conglomerate consists of rounded particles and breccia consists of angular particles.  Rounded versus angular is determined by distance of transportation from the source of weathering. Clastic Sedimentary Rocks – Particle Shape

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Rounding Transportation of Clastic Sediments

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Sample Question Using an example, describe the formation of clastic/detrital sedimentary rocks. Answer: Clastic/Detrital: Example: sandstone, shale, conglomerate, etc... Sediment such as pebbles, sand, silt, or clay can be lithified (compacted or cemented) to form solid sedimentary rock.

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Example 1: Explain how particle size is used to classify clastic (detrital) sedimentary rocks Answer: Sediment can be classified according to particle size. The smallest being clay, then silt, then sand, and finally pebbles. Clastic sedimentary rocks are named depending on what size sediments is found in the rock. Refer to the chart below. Particle SizeSediment NameRock Name Boulder & Pebble GravelConglomerate or Breccia Sand Sandstone Silt & Clay MudShale

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Example 2: Which diagram shows a well-sorted sediment? (A) (B) (C) (D) On the basis of which factor are clastic sedimentary rocks classified? (A) density(B) mineral composition (C) particle size(D) sorting

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Your Turn... Take the time and complete the following questions... (Solutions to follow) Question: What would a geologist determine from the section of sedimentary rock below? (A) Feldspar grains are harder than other types of grains. (B) Feldspar grains have traveled a shorter distance than other types of grains. (C) Quartz grains are softer than other types of grains. (D) Quartz grains have traveled a shorter distance than other types of grains.

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Solutions... Question: What would a geologist determine from the section of sedimentary rock below? (A) Feldspar grains are harder than other types of grains. (B) Feldspar grains have traveled a shorter distance than other types of grains. (C) Quartz grains are softer than other types of grains. (D) Quartz grains have traveled a shorter distance than other types of grains.

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Summary... Overview of Points covered:  Clastic sedimentary rocks are made of different types of sediment:  Pebbles/Gravel  Sand  Silt  Clay  Particle size, particle sorting and particle shape are characteristics used when classifying clastic sedimentary rocks.