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Sedimentary Rocks and Depositional Environments Lab 1.

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Presentation on theme: "Sedimentary Rocks and Depositional Environments Lab 1."— Presentation transcript:

1 Sedimentary Rocks and Depositional Environments Lab 1

2 Rock Types - Background Igneous Igneous Metamorphic Metamorphic Sedimentary Sedimentary Broken down to form sediments 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 Igneous, metamorphic, and sedimentary rocks are made of minerals Minerals – substances that make up rock; the building blocks of rocks Minerals – substances that make up rock; the building blocks of rocks Example minerals – quartz, potassium feldspar, biotite mica, muscovite mica, calcite Example minerals – quartz, potassium feldspar, biotite mica, muscovite mica, calcite

4 Sedimentary Rock Characteristics Grain size Grain size Rounding Rounding Minerals Minerals Matrix Matrix Color Color

5 Grain Size The average diameter of the particles 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(mud) < 1/256 mm Cannot be seen without a microscope, feels smooth, dull luster ** Ruler in Back of AGI Manual ** ** Ruler in Back of AGI Manual ** Pg. 1-2 of lab manual

6 Minerals Building blocks of rocks Building blocks of rocks MineralHardnessCleavageColorDistinguishingFeature Quartz7None(fractures) Milky to Colorless Hardness and looks glassy Potassium feldspar 6 2 to 3 planes Salmon to Red Color Biotite mica plane Black to dark brown Black flakes Muscovite mica 3 1 plane Colorless to light brown Light colored flakes; shiny Calcite3 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 Sedimentary rocks are composed of large particles (grains) surrounded by smaller particles The smaller particles are the matrix The smaller particles are the matrix The fill in between larger grains The fill in between larger grains Much None—there are almost no open spaces All Some

8 Sedimentary Environments A rock will display certain characteristics depending on the environment in which it was formed 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) 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 Alluvial Fans River Channels River Channels Glaciers Glaciers Swamps Swamps Deltas Deltas Beaches and Barrier Beaches and BarrierIslands Dunes Dunes Lagoons Lagoons Tidal Flats Tidal Flats Reefs Reefs Continental Shelf, Slope, and Rise Continental Shelf, Slope, and Rise Deep marine environments Deep marine environments

10 Refer to Figure 1.1 pg. 1-2

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

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

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

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

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

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

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

18 Lagoons Behind a barrier island or reef Behind a barrier island or reef Barrier island/reef act as breakwaters protecting the lagoon from wave action Barrier island/reef act as breakwaters protecting the lagoon from wave action Low-energy environment Low-energy environment Fine grain sizes settle and accumulate (silt, mud) Fine grain sizes settle and accumulate (silt, mud) Common rocks: shale, siltstone 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 Broad, flat areas that are periodically covered in water when tide rises and dry when tide is low Variable energy levels Variable energy levels Alternating layers of coarse and fine sediment Alternating layers of coarse and fine sediment Common rocks: siltstone, shale, limestone Common rocks: siltstone, shale, limestone

20 Reefs Organisms build large, rocky accumulations by cementing their shells or other structures Organisms build large, rocky accumulations by cementing their shells or other structures Common in tropical regions (warm water) Common in tropical regions (warm water) Calcite precipitates Calcite precipitates Common rocks: limestone 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 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 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 List properties of unknown sedimentary rocks Identify the unknown rock specimens (rock name) Identify the unknown rock specimens (rock name) Determine possible depositional environment(s) where the rock formed Determine possible depositional environment(s) where the rock formed

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


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