GEOL 1001 Chapter : Chapter 6 Notes
Chapter 6
Learning Objectives:
1) How do we make the 4 types of sedimentary rocks?
2) How to use structures to understand depositional environment?
I. Sedimentary Rocks
A. Background Information
- format surface
- make up about 8% volume of crust
B. Types of Sedimentary Rocks
a. Clastic Sedimentary Rocks
- cementation of loose particles
- loose particles of rocks that are cemented together to make a larger rock
- loose particles called “clasts” or clastic” or “grains”
- 5 steps to make classic sedimentary rocks:
1) Weathering => disintegration of bedrock
2) Erosion => removal of disintegrated bedrock; by water, ice, gravity
3) Transportation => path the sediment moves; gravity, water, ice moves particles
4) Deposition => sediment settles out of solution; water velocity drops, ice melts
5) Lithification => burial/compaction, cementation (with quartz, feldspar, hematite)
- examples include sandstone, breccia, shale, and conglomerates
b. Biogenic Sedimentary Rocks
- growth of shell masses
c. Organic Sedimentary Rocks
- accumulation of alteration of organic matter
d. Water Sedimentary Rocks
- precipitate from a water solution
C. Classifying Sedimentary Rocks
a. Clastic Sedimentary Rocks
- classified by grain size and texture
- clast size => boulder, cobble, pebble, sand, silt, clay (largest to smallest)
- sand is the lowest visible size
- grain is classified by coarse to fine
- clast composition => rock fragment of minerals (secondary descriptor)
Ex: clasts or granite, clasts of quartz
- angularity of clasts => corners on grains or clasts
- can be angular, sub-angular, sub-rounded, or rounded (closest to farthest
from source)
- tells us how far the particle traveled
- sorting => how different grain sizes are within rocks
- cementation => silica-cemented (Quartz), Feldspar, Hematite
b. Rock Names
- coarse grained, larger than sand sized; have two different names:
Breccia (angular clasts, close to source) and Conglomerate (rounded
grains, far from source)
- sand-sized grains => sandstones (beached, sand-dunes, rivers)
Document Summary
Loose particles of rocks that are cemented together to make a larger rock. Loose particles called clasts or clastic or grains . Examples include sandstone, breccia, shale, and conglomerates: clastic sedimentary rocks, biogenic sedimentary rocks. Growth of shell masses: organic sedimentary rocks, water sedimentary rocks. Learning objectives: how do we make the 4 types of sedimentary rocks, how to use structures to understand depositional environment, sedimentary rocks, background information. Make up about 8% volume of crust: types of sedimentary rocks, classifying sedimentary rocks, clastic sedimentary rocks, rock names. Clast size => boulder, cobble, pebble, sand, silt, clay (largest to smallest) Grain is classified by coarse to fine. Clast composition => rock fragment of minerals (secondary descriptor) Angularity of clasts => corners on grains or clasts. Can be angular, sub-angular, sub-rounded, or rounded (closest to farthest from source) Tells us how far the particle traveled. Sorting => how different grain sizes are within rocks.
