6.1/6.2 Guided Notes Hybrid

Weathering, Erosion and Deposition Produces Sediments: small pieces of rock that are moved and deposited by water, wind and gravity

Erosion: removal and transport of sediment Agents of erosion: Wind Moving water Gravity Glaciers

Deposition Sediment settles with the largest grains at the bottom of the layering and the smallest grains at the top

Lithification: Lithos = rock (Greek) Think “lithosphere” = earth’s crust Lithification Definition: The physical and chemical processes that turn sediments into rock Two parts of the process: –Compaction –Cementation

Lithification part 1 COMPACTION The weight forces the sediment grains to get closer and closer together causing physical changes to occur Mud can contain up to 60% water that gets squeezed out Sand does not compact as much as mud does because sand is mostly quartz Grain to grain contact in sand forms a supporting framework that maintains open space between the grains

Lithification part 2 CEMENTATION Minerals like calcite CaCO 3 and iron III oxide Fe 2 O 3 flow through the open spaces left by compaction The minerals linger and cement the grains together forming sedimentary rock

Sedimentary Features: Sedimentary rock tells geologists the history of the area BEDDING: predominant feature of sedimentary rock is the horizontal layering –Feature results from the way water or wind causes the sediment to settle out –Two types of bedding

Bedding Type #1: Graded Bedding Bedding in which heavier and coarser particles are located near the bottom of the sedimentary rock

Bedding Type #2: Cross-Bedding Inclined layers of sediment deposited along a horizontal surface

Ripple Marks Ripple Marks: –Evidence that the sediment was formerly moved by wave action

Fossils The best known feature of sedimentary rock is the propensity to find fossils in it During cementation the animal’s parts (like the shell) can be replaced by minerals and turned to rock which make up a fossil

Types of Sedimentary Rock Clastic / Detrital – made up of solid particles (gravel, sand, silt and clay) derived from preexisting rocks through weathering Chemical – sedimentary rocks that result from inorganic chemical processes or from the chemical activities of organisms

Clastic / Detrital Sedimentary Rocks Coarse-grained –Gravel sized fragments –Types of rock formed: conglomerate (rounded gravel), breccia (angular gravel) –Formed by high-energy flows of water Medium-grained –Sand fragments –Type of rock formed: sandstone –Formed by stream & river channels, beaches, deserts –Importance: due to pore spacing, fluids can move through and thus hold reservoirs of oil, natural gas, and groundwater Fine-grained –Silt and mud fragments –Type of rock formed: siltstone, shale, mudstone –Importance: low porosity resulting in a barrier to movement of groundwater & oil.

Chemical Sedimentary Rock Inorganic Sedimentary Rock –Evaporite – form as a result of crystal grains precipitating our of a supersaturated body of water –Type of rock formed: rock gypsum (made up of the mineral gypsum) & rock salt (made up of the mineral halite)

Chemical Sedimentary Rock Biochemical – form as a result of the chemical processes of organisms; many types of remains of once-living plants and/or animals. –Types of rock formed: limestone, chert, and coal. –Form in shallow-water, swamp, and coastal environments chert coal

Importance of Sedimentary Rock Provide historical timeline for area. Leaves a ‘footprint’ of all that’s come before us. –Past plants and animals –Bedrock –Ancient rivers, lakes and shorelines Provides resources –Oil, natural gas, and coal AKA: fossil fuels –Building materials –Uranium –Phosphate and iron