Lab 7 - Sed Rocks

SEDIMENTARY ROCKS Part I : Use your textbook, course notes, and the sedimentary rocks provided by your TA to answer the following questions. 1. What type of energy regime is necessary to transport and deposit the size of sediment found in a conglomerate? Give an example of an environment where such an energy regime occurs.(2 pts) High energy regime is the type of energy regime necessary to transport and deposit sediment found in a conglomerate. An example of an environment where this occurs might be an Aeolian environment 2. What type of energy regime is necessary to transport and deposit the size of sediment found in a shale? Give an example of an environment where such an energy regime occurs. (2 pts) A Low-energy regime is necessary to transport and deposit the size of sediment found in a shale. They typically form in environments where muds, silts, and other sediments were deposited by gentle transporting currents.

3. Why do most sand grains consist of quartz? What happened to the other minerals during the sedimentary rock-forming processes to produce pure quartz sandstone? (2 pt) Quartz is the most important sand-forming mineral because it is resistant to both physical and chemical weathering. Quartz sandstone results from the extreme weathering and sorting of a sediment until everything that can be removed has been removed. 4. Are the quartz grains in the sandstone sample rounded or angular? Are the grains in the arkose (feldspar-rich sandstone) sample rounded or angular? What does the roundness of the grains tell you about the distance from the source to the depositional environment? Why? (2 pts) Quartz grains of sandstone are round. Grains of arkose are angular. Roundness of grain tells us about the maturity of the Sedimentary rock as well as their parent rock distance. The larger the distance of transportation the more rounded the grain will be. It also indicates high maturity. 5. In what depositional environment does limestone form? Name one place on Earth where limestone is being formed at the present. (2 pts) Limestone forms in calm depositional environment like where chemical precipitation is possible mostly in deep seas where animals are present. currently limestone can be found in any deep-sea environments like Caribbean sea, Indian sea. 2

Part II: Using your textbook, course notes, and diagnostic tools (streak plate, hardness kit, hand lens, acid bottle, etc.), fill in the table of the characteristics for the sedimentary rocks provided by your TA. WORD BANK : Evaporite, Quartz Rich Sandstone, Coal, Coquina, Conglomerate, Shale, Arkose Sandstone, Micritic Limestone, Crystalline Limestone (1 pt for each rock) Sample Number Name of Rock Composition (Major Minerals) Grain size Both: Degree of Sorting & Degree of Rounding 1 Arkose Sandstone Feldspar, Quartz Sand angular, poorly sorted 2 Coal illite clay, pyrite, quartz, and calcite Clay Angular well sorted 3 Conglomerate silica, calcite or iron oxide Gravel Poor sorting and poor rounding 4 Coquina Calcite and phosphate sand Rounded well sorted 5 Quartz rich sandstone Quartz, feldspar, silt, clay Sand Rounded well sorted 6 Micritic Limestone Calcite Clay Angular well sorted 7 Shale Feldspar, quartz, mica, pyrite Clay Angular well sorted 8 Crystalline Limestone calcite and aragonite sand Rounded well sorted 9 Evaporite calcite, sand Rounded well 4

dolomite, magnesite, and aragonite sorted 5