CHAPTER 8 SEDIMENTARY ROCK

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CHAPTER 8: SEDIMENTARY ROCK Sedimentary Sedimentary rock rock is is formed formed from from the the weathered weathered and and eroded eroded remains remains of of other other rocks rocks Many of the rock layers in this photograph are composed of sediments that accumulated on the seafloor What evidence would reveal to a geologist that a rock formed in a marine environment? Sedimentary Rock • • Most of Earth’s surface is covered with layers of loose sediment >75% of the land surface is Sedimentary Rock • They reflect physical and chemical characteristics of their source environments and depositional processes Steven Earle Why study sedimentary rocks? Fossiliferous Cambrian Burgess Shale at Mt Planetary nebula remaining Stephen, BC mineral particles and gas after a star • They contain direct and indirect evidence of life and its evolution • They can be interpreted to understand geological history • The are the source of important resources, including metals, building materials and energy Steven Earle explodes Triassic limestone being quarried for cement at Texada Island, BC There are three common types of sediment: Clastic, Chemical, and Biogenic • • CLASTIC SEDIMENTS are broken and eroded pieces of rocks and minerals deposited by water, wind, ice, or some other physical process What is the main mineral in this sandy sediment? What else might be present? Chemical and Biogenic Sediments CHEMICAL SEDIMENTS are produced by inorganic (nonbiological) precipitation of dissolved compounds (e.g., through evaporation) BIOGENIC SEDIMENTS are produced by organic (biological) precipitation of the remains of living organisms Comet exhibiting coma (tail) Change in Sediments • Sediments change as they are transported across Earth’s surface… en route to their depositional environment What are the likely depositional environments of these three types of sediment? Particle Size Reflects Depositional Energy Sorting Particles separated based on grain size Decreasing grain size with increased transport distance and decreased energy level The Sedimentary Cycle • Sediment becomes sedimentary rock during the sedimentary cycle Sediments typically accumulate at rates of less than mm per year How long would it take to accumulate 1000 m of sediment at a rate of 0.2 mm/year? Lithification • Lithification is caused by compaction and cementation The important types of clastic sedimentary rock • Distinguished by: – – – grain size and shape grain type (mineralogy) texture of the grains, matrix and cements Why are they called clastic sedimentary rocks? What is a clast? Types of Sediment • • Specific combinations of texture and composition for each type Determined by sediment’s history: transport energy and distance, weathering intensity, and composition of source rock Important clastic sedimentary rocks conglomerate breccia quartz sandstone What is the textural difference between conglomerate and breccia? What are the compositional differences between quartz sandstone, arkose and lithic sandstone? lithic sandstone siltstone claystone shale arkose Chemical sedimentary rocks Rock salt Gyspum Chert Travertine Biogenic Sedimentary Rock Skeletal limestone Chalk What skeletal limestone, chalk and coquina have in common? Coquina Coal Sedimentary rocks preserve evidence of past environments and ecology Continental depositional environments Wetland, alluvial fan, stream, desert, lake, glacier – which is which? Do all of these environments exist in Canada? Coastal depositional environments Barrier island, carbonate lagoon, beach, tidal wetland, delta – which is which? Do all of these environments exist in Canada? Marine Environments of deposition Primary sedimentary structures record modern and ancient sedimentary processes Ripples Mud Cracks Steven Earle Cross-bedding in eolian sandstones, Zion Canyon, Utah Graded bedding in submarine fan rocks, Steven Earle Gabriola Island ,BC Bedding in fluvial and lacustrine deposits, Horseshoe Canyon, Alberta Choose four depositional environments in this figure For each, describe the texture of the sediments likely to form Consider the beach and glacier If the sediment source for each was Haiti, 2010 granitic mountains, predict the composition of sediments in each there case COPYRIGHT Copyright © 2014 John Wiley & Sons Canada, Ltd All rights reserved Reproduction or translation of this work beyond that permitted by Access Copyright (The Canadian Copyright Licensing Agency) is unlawful Requests for further information should be addressed to the Permissions Department, John Wiley & Sons Canada, Ltd The purchaser may make back-up copies for his or her own use only and not for distribution or resale The author and the publisher assume no responsibility for errors, omissions, or damages caused by the use of these programs or from the use of the information contained herein [...]... quartz sandstone, arkose and lithic sandstone? lithic sandstone siltstone claystone shale arkose Chemical sedimentary rocks Rock salt Gyspum Chert Travertine Biogenic Sedimentary Rock Skeletal limestone Chalk What do skeletal limestone, chalk and coquina have in common? Coquina Coal Sedimentary rocks preserve evidence of past environments and ecology Continental depositional environments Wetland, alluvial... texture of the grains, matrix and cements Why are they called clastic sedimentary rocks? What is a clast? Types of Sediment • • Specific combinations of texture and composition for each type Determined by sediment’s history: transport energy and distance, weathering intensity, and composition of source rock Important clastic sedimentary rocks conglomerate breccia quartz sandstone What is the textural difference... abundant The Sedimentary Cycle • Sediment becomes sedimentary rock during the sedimentary cycle Sediments typically accumulate at rates of less than 1 mm per year How long would it take to accumulate 1000 m of sediment at a rate of 0.2 mm/year? Lithification • Lithification is caused by compaction and cementation The important types of clastic sedimentary rock • Distinguished by: – – – grain size and shape... matter Sedimentary Basins • Dissolved compounds are transported from weathering sites into Sedimentary Basins Sediments evolve during transportation and deposition • • • • Unstable grains (olivine, pyroxene, feldspar, amphibole, and others) become less abundant Stable grains (quartz, clays, muscovite) become more abundant Biogenic sediments accumulate Chemical sediments may become more abundant The Sedimentary. .. – which is which? Do all of these environments exist in Canada? Marine Environments of deposition Primary sedimentary structures record modern and ancient sedimentary processes Ripples Mud Cracks Steven Earle Cross-bedding in eolian sandstones, Zion Canyon, Utah Graded bedding in submarine fan rocks, Steven Earle Gabriola Island ,BC Bedding in fluvial and lacustrine deposits, Horseshoe Canyon, Alberta
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