112lect1 - GY 112 Lecture Notes D. Haywick (2006) 1 GY 112...

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GY 112 Lecture Notes D. Haywick (2006) 1 GY 112 Lecture Notes Rock Review Lecture Goals : A) Recap of rock types B) Recap of the rock cycle C) Sedimentary rocks: their role in earth history Textbook reference: Levin 7 th edition (2003), Chapter 2 ; Levin 8 th edition (2006), Chapter 4 (For those of you who have already completed GY 111, you will find your lecture and lab notes of use for this part of GY 112) A) Recap of rock types To cut to the chase, there are 3 main divisions of rocks, but in GY 112, the sedimentary rocks are by far the most important. The reason? They are commonly fossiliferous (meaning that they host fossils). First off, here are the 3 main rock divisions: Igneous (formed from molten rock) Sedimentary (formed from particulate material) Metamorphic (alteration of parent rocks through heat, pressure and fluids) Each of these rock groups have subdivisions. As I said earlier, it is the sedimentary rocks that are the most important group in GY 112. Let’s start with them: Sedimentary rocks are classified according to two different parameters: 1) Grain size (see chart to left) and composition . The grain size refers to the size of the particles that make up the rocks. These are the “things” that were initially deposited before the sediment became “ lithified” , which just means conversion into “rock”. There are 4 major size divisions of sediment that you need to remember: 1) gravel (the largest division; grains 2.0 mm), 2) sand (grains <2.00 mm but 0.63 mm), 3) silt (grains <0.63 mm but 0.004 mm) and clay (grains 0.004 mm). Obviously, you can’t see the really small silt and clay grains. Sedimentologists (those really cool and wonderful scientists like Dr. Haywick that study sedimentary rocks), frequently have to use microscopes and scanning electron microscopes to study the smallest sedimentary particles.
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GY 112 Lecture Notes D. Haywick (2006) 2 As far as composition is concerned, sedimentary rocks are classified into four sub- divisions: 1) Clastic (also known as siliciclastic); rocks contained particles rich in silica-rich minerals such as quartz, feldspar and clay minerals. Examples include quartz arenite 1 sandstone, arkose sandstone, greywacke sandstone, shale, claystone, siltstone and mudstone. 2) Bioclastic; rocks containing remains of once living creatures (aka beasties). Examples include limestone (carbonate shells and skeletal elements), chalk (microscopic carbonate shells and body parts) and biogenic chert (microscopic silica body parts). 3)
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This note was uploaded on 02/04/2012 for the course GLY 112 taught by Professor Haywick during the Spring '12 term at S. Alabama.

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112lect1 - GY 112 Lecture Notes D. Haywick (2006) 1 GY 112...

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