- Slides: 35
A. Formation: 1. Sedimentary rocks form from the COMPACTION & CEMENTATION of rock fragments/sediments 2. Lithification: the changing of sediments into sedimentary rock
3. Sedimentary rocks are similar to the sediments from which they form (ie. Sandstone is made up of sand)
B. CLASTIC 1. Form when rock fragments & sediment are carried & deposited by GRAVITY, WIND, GLACIERS, & RUNNING WATER
Clastic Rock Formation
Most sediment is carried by Running Water 2. The farther water carries sediment, the ROUNDER & SMOOTHER the sediment becomes 3. When a stream slows down, it drops the LARGEST particles first, & the SMALLEST last (HORIZONTAL SORTING)
Observe how sediments are deposited
So…. • If you are far out from shore, would you expect the grain size of the rocks to be large or small? • What about if you are close to the shore?
That means…. 4. Rocks formed closer to shore will be made up of bigger fragments than rocks formed farther away from the shore
Conglomerate – large sediments that are rounded (have been transported by a stream!) Breccia – very large sediments that are angular, most likely deposited by gravity
C. CRYSTALLINE 1. Formed when dissolved minerals in seawater are deposited (seawater evaporates, leaving the minerals behind to crystalize) 2. Also known as CHEMICAL
Salt “Mines” - Rock Salt is being formed as the salt water evaporates from the sea.
“Devil’s Golf Course” – millions of years ago this was a sea of salt water. It has been evaporating over time… …and has formed “pockets” of chemical limestone, rock salt, and rock gypsum!
D. BIOCLASTIC 1. Formed from the remains of plants & animals that are compacted – Fossil Limestone – formed when shell remains of marine organisms are cemented in fragments • Shells are made of CALCITE which reacts with acid
2. Coal Formation
a. Long ago, huge trees grew in the warm, humid swamps. b. Trees died and decomposed into what is called PEAT c. Peat was buried under layers of mud. d. Pressure increased, slowly changing the plant remains into coal. Coal – note distinct layering of peat
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STRATIFICATION 1. STRATIFICATION (layering): Layers of sediments that have SIMILARLY colored minerals and are typically sandstones or siltstones
2. Fossils – actual remains, imprints from plants or animals, or preserved traces from living things
bells & whistles for sedimentary rock identification! • Stratification • Fossils • Fragments of materials cemented together • Ripple marks • Mud cracks
Angel’s Landing, Zion Nat’l Park, Utah – note rock layers
Red Sandstone, Utah – note distinct LAYERING of sediments (sand)
Horseshoe Bend, Utah
Grand Canyon Nat’l Park, Arizona – sedimentary rock formation at its best! The canyons were formed by the Colorado River cutting into the rock layers over time!
Fossils • The remains, impression or any other evidence of a plant or animal preserved in rock. • Fossilization
Brachiopod fossils in limestone Trilobite fossils – over 250 MILLION years old!!! Imprint of a leaf
Mud Cracks and Ripples • Ripple Marks: A sand pattern formed by the action of winds, streams, waves or currents; preserved when sand becomes sandstone • Mud Cracks: Develop when deposits of wet clay dry and contract. The cracks are filled with sediments and fossilize when the clay becomes shale
Ripple Marks in the Shale from running water as the rock was forming
Video Watch the video and jot down 3 notes about it in your notes https: //www. youtube. com/watch? v=e. Ou Ps. Jw. Yu 9 I If the video doesn’t show, search for Geologist Kitchen Clastic Sedimentary Rocks