CHAPTER 6.3 SEDIMENTARY ROCKS

SEDIMENTARY ROCKS 95% OF EARTHS CRUST IS IGNEOUS ROCK, AND 4-5% IS SEDIMENTARY AND METAMORPHIC ROCK SEDIMENTS – ANY SUBSTANCE THAT SETTLES OUT OF A FLUID Created by weathering and erosion WEATHERING – THE PROCESS BY WHICH ROCKS ARE BROKEN UP INTO FRAGMENTS MECHANICAL, CHEMICAL AND BIOLOGICAL EROSION – THE REMOVAL AND TRANSPORT OF EARTH MATERIALS BY NATURAL AGENTS LITHIFICATION – PROCESS BY WHICH MATERIALS BECOME ROCK

ORIGIN OF SEDIMENTS: 1. CLASTIC – ROCK FRAGMENTS FORMED BY WEATHERING/EROSION OF EXISTING ROCK DEFINED BY SIZE - SMALLEST TO LARGEST CLAY, SILT, SAND, GRAVEL Clastic sediments are often sorted by water action before pressure and mineral cements turn them into rock.

LITHIFICATION OF CLASTICS: a.) CEMENTATION DISSOLVED MINERALS THAT BIND PARTICLES TOGETHER SILICA – FROM QUARTZ. GRAY OR WHITE LIME – FROM CALCITE. GRAY OR WHITE IRON – VARIOUS IRON MINERALS RED, BROWN, YELLOW b.) COMPACTION – PRESSURE OF OVERLYING MATERIALS LITHIFY DEPOSITS

1. A river moves sediment into a lake. 2. Particles are sorted by size. The largest gravels are the first to be deposited, followed by sands, and then silt and clay. Sands and Gravels Sands Silt and Clay 3. Over time, the sediments are buried, compacted, and may be cemented. Conglomerate Sandstone Shale

CLASTIC SEDIMENTARY ROCKS: CONGLOMERATE – CEMENTED MIXTURE OF ALL SIZES OF CLASTIC MATERIALS. LARGEST PEBBLES (QUARTZ) SANDSTONE – CEMENTED QUARTZ / FELDSPAR GRAINS SILTSTONE – SILT SIZED PARTICLES SHALE – COMPACTED SILT OR CLAY. OFTEN OCCUR IN FLAT SHEET LIKE LAYERS.

SANDSTONE CONGLOMERATE

SILTSTONE SHALE

2. CHEMICAL SEDIMENTARY ROCKS – SEDIMENTS THAT FORM FROM EVAPORATION OR PRECIPITATES LIMESTONE – CHEMICAL DEPOSITION OF CALCITE ROCK SALT – EVAPORATIVE DEPOSITION OF HALITE ROCK GYPSUM – EVAPORATIVE DEPOSITION OF GYPSUM

LIMESTONE ROCK GYPSUM ROCK SALT

3. ORGANIC – SEDIMENTS FORMED FROM THE REMAINS OF PLANTS AND ANIMALS COQUINA – LIMESTONE FORMED BY THE CALCUIM REMAINS OF MARINE ANIMALS SHELL LIMESTONE – SHELLS CEMENTED BY LIME OR CLAY MATRIX BITUMINOUS COAL – COMPACTION OF PLANT MATERIAL

COQUINA

SHELL LIMESTONE

BITUMINOUS COAL

SEDIMENTARY ROCK FEATURES: STRATIFICATION – THE DEPOSITION OF SEDIMENTS INTO IN BEDS GIVES A LAYERED APPEARANCE

BEDDING PLANE – THE LINE THAT SEPARATES ROCK LAYERS BEDDING PLANE – THE LINE THAT SEPARATES ROCK LAYERS. ORIGINALLY DEPOSITED IN NEARLY HORIZONTAL POSITION.

CROSS BEDDING – BEDS ARE DEPOSITED IN INCLINED LAYERS CROSS BEDDING – BEDS ARE DEPOSITED IN INCLINED LAYERS. COMMON IN WIND OR DELTAIC DEPOSITS.

FOSSILS – THE REMAINS OR IMPRESSIONS OF PLANTS OR ANIMALS IN ROCK

RIPPLE MARKS – FEATURES FORMED BY THE ACTION OF WIND OR WATER CURRENTS. MUD CRACKS – DEVELOP WHEN DEPOSITS WITH HIGH % OF CLAY DRY AND CONTRACT. CONCRETION – ROUND OR EGG SHAPED BODIES FOUND IN LIMESTONE OR SHALEBEDS.