Please read the power point I have posted for this chapter, read chapter 7 from

Question

Please read the power point I have posted for this chapter, read chapter 7 from your textbook and answer the following: 1- Explain how changes in water velocity will determine which particle size of sediment is deposited. 2- Why would the release of carbon sequestered in carbonates and organic sedimentary rocks be a concern? 3- What information can evaporites provide about the past environment of deposition? 4- Explain how deposits of mud and sand are lithified. 5- Compare and Contrast: - Conglomerate and Breccia - Quartz Sand and Arkose Sand

Explanation / Answer

1. Changes in water velocity in erosion and deposition of different sizes of sediments are correlated in hjulstorms curve. In which it is said that coarse particles are not even uplifted due to their high specific gravity so slight decrease in velocity deposits them, sand and coarse silt particles are deposited when velocities reach very less orders and finally suspended fine silt and clay are deposited in almost still water when velocity is similar to zero.

2. Carbonate rocks are composed of Calcite which reacts with bicarbonate and acids from the rain and release calcium and carbon too. This reaction is exothermic and produces lot of heat. This leached calcium goes into streams and oceans further.

3.As evaporites are formed by the successive evaporation of water, Calcite forms at initial and when volume of water reduces gypsum and anhydrites are formed and when water reduces to 20 percent of its original volume halite is formed. And also type of evaporites determines the Ca, Mg and bicarbonate concentration of water of evaporates. Ca and magnesium are in equal amounts above mentioned sequence will be formed. If ca is greater than Mg then those water forms mirabilite, to a minerals.

4.lithification involves compaction and cementation processes. Compaction decreases porosity by compressing the sand or mud and cementation is by precipitation of fluids in the pores which binds grain particles to each other. In mud as they are cohesive only compaction takes place i.e. Due to stress and pressure mud get lithified. But sand undergoes compaction first and the cementation takes place. Commonly ferrugenous and carbonate cements.

5.conglomerate are rounded grain particles formed a rock but breccia have class with angular fragments cemented together to for rock. Quartz sand have more than 90 percent of quartz and arkose sand have quartz less percentage like below 35 percent and feldpar and lithic fragments are present of which feldpar dominates the composition  

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