1. Sedimentary Rocks and Depositional Environments
Lab 1

2. Rock Types - Background
Igneous
Metamorphic
Sedimentary
Broken down to form sediments
Sediments – fragments of rock, individual mineral grains (quartz), parts of plants or animals, clay minerals, and other minerals

3. Minerals - Background
Igneous, metamorphic, and sedimentary rocks are made of minerals
Minerals – substances that make up rock; the building blocks of rocks
Example minerals – quartz, potassium feldspar, biotite mica, muscovite mica, calcite

4. Sedimentary Rock Characteristics
Grain size
Rounding
Minerals
Matrix
Color

5. Grain Size The average diameter of the particles
Gravel
> 2 mm
Visible to the unaided eye
Sand
< 2mm,
>1/8 mm
Visible to the unaided eye, feels very gritty
Silt
(mud)
<1/8 mm,
> 1/256 mm
Invisible to the unaided eye, can see with a hand lens, feels gritty
Clay
< 1/256 mm
Cannot be seen without a microscope, feels smooth, dull luster
Pg. 1-2 of lab manual
** Ruler in Back of AGI Manual **

6. Minerals Building blocks of rocks Mineral Hardness Cleavage Color
Distinguishing
Feature
Quartz 7
None
(fractures)
Milky to
Colorless
Hardness and looks
glassy
Potassium feldspar 6
2 to 3 planes
Salmon to Red
Biotite mica
2.5
1 plane
Black to dark brown
Black flakes
Muscovite mica 3
Colorless to light brown
Light colored flakes; shiny
Calcite
3 planes, rhomb
White to Gray
Reacts with acid (HCL)
Pg. 1-3 of lab manual

7. Matrix
Sedimentary rocks are composed of large particles (grains) surrounded by smaller particles
The smaller particles are the matrix
The fill in between larger grains
None—there are almost no open spaces
Some
All
Much

8. Sedimentary Environments
A rock will display certain characteristics depending on the environment in which it was formed
The study of the composition and other characteristics of the sed. rocks can reveal info. about the conditions occurring during deposition (helps determine environment)

9. Sedimentary Environments
Alluvial Fans
River Channels
Glaciers
Swamps
Deltas
Beaches and Barrier
Islands
Dunes
Lagoons
Tidal Flats
Reefs
Continental Shelf, Slope, and Rise
Deep marine environments

10. Refer to Figure 1.1 pg. 1-2

11. Alluvial Fan Rivers in mountainous areas erode and transport sediment
When meets flat plain deposits sediment in fan-like shape
Common rocks: sandstone, conglomerate, breccia, diamicton

12. River Channels Rivers vary in size and energy level
Contain various sediment types (gravel, sand)
Feldspar less common
Common rocks: sandstone, conglomerate

13. Glaciers Not able to sort sediment size
Glacial sediments (till) are mixtures of gravel, sand, silt, and clay
Rock types: diamicton

14. Swamps Lots of organic matter Slow decomposition
Buried and compacted organic matter hardens to form coal
Common rocks: coal, shale

15. Deltas Rivers flow into lakes or oceans
Deposit sediment in a fan-like shape
Mississippi River Delta, Nile Delta
Large areas composed of various environments (channels, swamps, bays)
Common rocks: shale, siltstone, sandstone, coal

16. Beaches and Barrier Islands
Barrier island is like a beach separated from the mainland by a lagoon
Constant wave action separates sand sized grains from others
Sediment has traveled far from source, so well rounded
Common rocks: sandstone

17. Dunes Form adjacent to beaches and barrier islands
Contain non-marine fossils
Common rocks: sandstone

18. Lagoons Behind a barrier island or reef
Barrier island/reef act as breakwaters protecting the lagoon from wave action
Low-energy environment
Fine grain sizes settle and accumulate (silt, mud)
Common rocks: shale, siltstone

19. Tidal Flats
Broad, flat areas that are periodically covered in water when tide rises and dry when tide is low
Variable energy levels
Alternating layers of coarse and fine sediment
Common rocks: siltstone, shale, limestone

20. Reefs
Organisms build large, rocky accumulations by cementing their shells or other structures
Common in tropical regions (warm water)
Calcite precipitates
Common rocks: limestone

21. Continental shelf, slope, and rise
Shallow marine: extend from beach to water depths of 100 m; low energy; fine grains settle; common rocks are sandstone, siltstone, shale
Deep marine: extend down to thousands of meters; low energy; fine grains settle; fossils are rare; common rocks are shale, sandstone

22. Today’s Lab!! List properties of unknown sedimentary rocks
Identify the unknown rock specimens (rock name)
Determine possible depositional environment(s) where the rock formed

23. Rock Names Shale Siltstone Sandstone Conglomerate Breccia Diamicton
Limestone
Coal