SEDIMENTARY ROCKS BEGIN

Transcription

1 SEDIMENTARY ROCKS BEGIN

2 WHAT IS A SEDIMENTARY ROCK? A sedimentary rock is a rock that formed from the compaction and cementation of sediments.

3 BUT, WHAT IS A SEDIMENT? Sediments are fragments of rock that have been broken down as a result of weathering (wind, ice, running water, etc.)

4 SEDIMENTS ARE CLASSIFIED ACCORDING TO THEIR SIZE. CLAY SILT SAND PEBBLE COBBLE BOULDER

5 SEDIMENT NAMES AND SIZES CAN BE FOUND ON INORGANIC LAND-DERIVED SEDIM TEXTURE GRAIN SIZE COMPOSITION CO Clastic (fragmental) Pebbles, cobbles, and/or boulders embedded in sand, silt, and/or clay Sand (0.006 to 0.2 cm) Silt ( to cm) Clay (less than cm) Scheme for Sedimentary Rock Mostly quartz, feldspar, and clay minerals; may contain fragments of other rocks and minerals Rounded Angular f Fine to co Very fine Compact easily CHEMICALLY AND/OR ORGANICALLY FORME TEXTURE GRAIN SIZE COMPOSITION COM PAGE 7 OF THE ESRT Crystalline Crystalline or bioclastic Bioclastic Fine to coarse crystals Microscopic to very coarse Halite Gypsum Dolomite Calcite Carbon Crysta chemi precip and ev Precipitate origin or ce fragments Compacte plant rem Scheme for Metamorphic Rock

6 Relationship of Transported Particle Size to Water Velocity Boulders Cobbles Pebbles...AND ON Sand Silt Clay PAGE 6 OF THE ESRT STREAM VELOCITY (cm/s)

7 Sediments are constantly being dropped off all over the Earth. This process is known as deposition.

8 Clastic sedimentary rocks are composed of sediments which have been compacted by the weight of water or other sediments, and cemented, or glued together.

9 Scheme for Sedimentary Rock Identification INORGANIC LAND-DERIVED SEDIMENTARY ROCKS TEXTURE GRAIN SIZE COMPOSITION COMMENTS ROCK NAME MAP SYMBOL Clastic (fragmental) Pebbles, cobbles, and/or boulders embedded in sand, silt, and/or clay Sand (0.006 to 0.2 cm) Silt ( to cm) Clay (less than cm) Mostly quartz, feldspar, and clay minerals; may contain fragments of other rocks and minerals Rounded fragments Angular fragments Fine to coarse Very fine grain Compact; may split easily Conglomerate Breccia Sandstone Siltstone Shale CHEMICALLY AND/OR ORGANICALLY FORMED SEDIMENTARY ROCKS TEXTURE GRAIN SIZE COMPOSITION COMMENTS ROCK NAME MAP SYMBOL Crystalline Fine to coarse crystals Halite Gypsum Dolomite Crystals from chemical precipitates and evaporites Rock salt Rock gypsum Dolostone Crystalline or bioclastic Bioclastic Microscopic to very coarse Calcite Carbon Precipitates of biologic origin or cemented shell fragments Compacted plant remains Limestone Bituminous coal Scheme for Metamorphic Rock Identification

10 Scheme for Sedimentary Rock Identification INORGANIC LAND-DERIVED SEDIMENTARY ROCKS TEXTURE GRAIN SIZE COMPOSITION COMMENTS ROCK NAME MAP SYMBOL Clastic (fragmental) Pebbles, cobbles, and/or boulders embedded in sand, silt, and/or clay Sand (0.006 to 0.2 cm) Silt ( to cm) Clay (less than cm) Mostly quartz, feldspar, and clay minerals; may contain fragments of other rocks and minerals Rounded fragments Angular fragments Fine to coarse Very fine grain Compact; may split easily Conglomerate Breccia Sandstone Siltstone Shale CHEMICALLY AND/OR ORGANICALLY FORMED SEDIMENTARY ROCKS TEXTURE GRAIN SIZE COMPOSITION COMMENTS ROCK NAME MAP SYMBOL Notice how they are classified Halite Rock salt Fine Crystals from to Crystalline chemical coarse Gypsum precipitates Rock gypsum according to the size of the crystals and evaporites Dolomite Dolostone Crystalline sediments or making Precipitates of biologic them up. Calcite origin or cemented shell Limestone bioclastic Microscopic to fragments very coarse Bioclastic Compacted Carbon plant remains Bituminous coal Scheme for Metamorphic Rock Identification

11 Conglomerate is composed of rounded sediments of all different sizes.

12 Breccia is composed of angular sediments of all different sizes.

13 Sandstone is composed of sand-sized sediments and may display layering.

14 Siltstone is composed of silt-sized sediments.

15 Shale is composed of clay-sized sediments and often contains fossils.

16 Sedimentary rocks may form in other ways, besides compaction and cementation of sediments.

17 Some are said to be crystalline, forming from evaporation or precipitation.

18 Scheme for Sedimentary Rock Identification INORGANIC LAND-DERIVED SEDIMENTARY ROCKS TEXTURE GRAIN SIZE COMPOSITION COMMENTS ROCK NAME MAP SYMBOL Clastic (fragmental) Pebbles, cobbles, and/or boulders embedded in sand, silt, and/or clay Sand (0.006 to 0.2 cm) Silt ( to cm) Clay (less than cm) Mostly quartz, feldspar, and clay minerals; may contain fragments of other rocks and minerals Rounded fragments Angular fragments Fine to coarse Very fine grain Compact; may split easily Conglomerate Breccia Sandstone Siltstone Shale CHEMICALLY AND/OR ORGANICALLY FORMED SEDIMENTARY ROCKS TEXTURE GRAIN SIZE COMPOSITION COMMENTS ROCK NAME MAP SYMBOL Crystalline Fine to coarse crystals Halite Gypsum Dolomite Crystals from chemical precipitates and evaporites Rock salt Rock gypsum Dolostone Crystalline or bioclastic Bioclastic Microscopic to very coarse Calcite Carbon Precipitates of biologic origin or cemented shell fragments Compacted plant remains Limestone Bituminous coal Scheme for Metamorphic Rock Identification

19 An evaporite, like Rock Salt, forms when minerals dissolved in water are left behind as crystals when the water evaporates.

20 This area was once covered by a shallow, salty sea. Over time, the water evaporated, leaving the salt behind. This is how the sedimentary evaporite, Rock Salt forms.

21 The third, and final, type of sedimentary rocks are organic in nature.

22 These rocks form as a result of processes that involve living organisms.

23 Scheme for Sedimentary Rock Identification INORGANIC LAND-DERIVED SEDIMENTARY ROCKS TEXTURE GRAIN SIZE COMPOSITION COMMENTS ROCK NAME MAP SYMBOL Clastic (fragmental) Pebbles, cobbles, and/or boulders embedded in sand, silt, and/or clay Sand (0.006 to 0.2 cm) Silt ( to cm) Clay (less than cm) Mostly quartz, feldspar, and clay minerals; may contain fragments of other rocks and minerals Rounded fragments Angular fragments Fine to coarse Very fine grain Compact; may split easily Conglomerate Breccia Sandstone Siltstone Shale CHEMICALLY AND/OR ORGANICALLY FORMED SEDIMENTARY ROCKS TEXTURE GRAIN SIZE COMPOSITION COMMENTS ROCK NAME MAP SYMBOL Crystalline Fine to coarse crystals Halite Gypsum Dolomite Crystals from chemical precipitates and evaporites Rock salt Rock gypsum Dolostone Crystalline or bioclastic Bioclastic Microscopic to very coarse Calcite Carbon Precipitates of biologic origin or cemented shell fragments Compacted plant remains Limestone Bituminous coal Scheme for Metamorphic Rock Identification

24 Bituminous Coal forms from the decomposition and compaction of plant remains over thousands of years.

25 Some forms of Limestone, like this coquina, form from the compaction and cementation of shells.

26 Sedimentary rocks are the only type of rocks that may contain fossils, or evidence of past life.

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