Sedimentary Rocks Copyright © 2008 Joe Marx.

Vocabulary Cementation: minerals fill the spaces between sediments and act as glue. Compaction: sediments are pressurized to become rock. Breccia: sharp rocks (or sediments) cemented together to form one rock Conglomerate: rocks cemented together to form one rock (rounded edges).

Sedimentary Rocks Image courtesy of Wikimedia Commons. Page 3 Topics for This Lecture What is sediment? What are sedimentary rocks? What are the different kinds of sedimentary rock? What are sedimentary structures and how are they produced? In what environments do sedimentary rocks form? ◄ Edge of Athabasca Glacier, Jasper National Park, Alberta, Canada, August, 2006.

Sedimentary Rocks Image courtesy of U.S.Geological Survey. Page 4 What is Sediment? Solid material that accumulates on Earth’s surface, generally forming layers. Four main classes of sediment: –Detritus: Solid fragments of rock or mineral matter that have weathered out of pre-existing rock. –Inorganic precipitates from natural waters. –Shells, often microscopic, that were secreted by plants or animals. –Buried plant remains. Silty and sandy sediment, Canyon Largo, New Mexico. ►

Sedimentary Rocks Image courtesy of U.S.Geological Survey. Page 5 What is Sedimentary Rock? Rock formed, under moderate pressure, from accumulated layers of sediment. There are four main classes of sedimentary rock, corresponding to the four classes of sediment: –Clastic or detrital rock, from detritus. –Chemical rock, from inorganic precipitates. –Biochemical rock, from plant and animal shells. –Organic rock, from plant remains. ◄ Jonesboro Limestone, a chemical rock that occurs within Great Smoky Mountains National Park, Tennessee.

Sedimentary Rocks Image courtesy of U.S.Geological Survey. Page 6 Clastic Sedimentary Rock A clast is an individual mineral grain or rock fragment—one piece of detritus. After chemically and physically weathering out of pre-existing rock, clasts are transported by wind, water, ice or gravity to a site of deposition. Clastic (or detrital) sedimentary rock is composed of compacted and cemented detritus. Limestone breccia, Titus Canyon, Death Valley National Park, California. ►

Sedimentary Rocks Images courtesy of Oxford Earth Sciences Image Store. Page 7 Principal Clastic Rocks Clastic rocks are classified based on mineral content, grain size, and grain shape. Sandstone and shale are the principal clastic rocks. Others include conglomerate and breccia. Sandstone Shale Conglomerate

Sedimentary Rocks Left-hand image courtesy of Oxford Earth Sciences Image Store. Right- hand image courtesy of U.S.Geological Survey. Page 8 Composed primarily of mineral crystals inorganically precipitated from natural water. Principal chemical rocks include limestone deposited in warm or running water, and evaporites, such as rock gypsum and rock salt, left behind when salty water evaporates. Oolitic Limestone Chemical Rock Rock Gypsum

Sedimentary Rocks Images courtesy of Oxford Earth Sciences Image Store. Page 9 Formed from shells—crystalline masses precipitated by living organisms. The principal biochemical rock is biogenic limestone. Fossiliferous LimestoneChalk Biochemical Rock

Sedimentary Rocks Image courtesy of U.S. Geological Survey. Page 10 Formed by the compaction and anaerobic distillation (carbon purification) of plant remains. The principal organic rock is coal. Strip mine, Coalmont district, Jackson County, Colorado, Organic Rock

Sedimentary Rocks Image copyright © Society for Sedimentary Geology, courtesy of Earth Science World Image Bank. Page 11 A distinctive arrangement of grains within a sedimentary rock. Bedding describes the layers ◄ Banded iron formation, Dales Gorge, Western Australia. Sedimentary Structure

Sedimentary Rocks Image courtesy of U.S. Geological Survey. Page 12 The arrangement of sedimentary rock in layers of varying thickness and character. Thin-bedded limestone of the Tomstown Formation, near Rohersville, Maryland. Bedding or Stratification

Sedimentary Rocks Images copyright © Bruce Molnia, Terra Photographics, courtesy of Earth Science World Image Bank. Page 13 Characterized by distinct vertical gradations in grain size, generally from coarse at the base to fine at the top. Produced when grains drop gradually from wind or water currents. Finer grains take longer to settle. Graded Bed ◄ Graded Pleistocene sediments, near Lafayette, Indiana. Graded bedding in turbidites, Delaware Basin, New Mexico. ►

Sedimentary Rocks Left-hand image copyright © Larry Fellows, Arizona Geological Survey. Right-hand image copyright © Bruce Molnia, Terra Photographics. Both courtesy of Earth Science World Image Bank. Page 14 Alternating ridges and hollows produced by the movement of wind or water across a granular surface. Ripple marks in Tertiary sandstone, Point Lobos State Park, California. Ripples on gypsum sand dune, White Sands National Monument, New Mexico. Ripple Marks

Sedimentary Rocks Image copyright © Marli Miller, University of Oregon, courtesy of Earth Science World Image Bank. Page 15 A bed inclined at an angle to the main plane of stratification. Produced as dunes or ripples deposited by a current of wind or water. Cross bedding in the Navajo Sandstone, Zion National Park, Utah. ► Cross Bed

Sedimentary Rocks Left-hand image copyright © Bruce Molnia, Terra Photographics, courtesy of Earth Science World Image Bank. Right-hand image courtesy of U.S. Geological Survey. Page 16 Surface fractures, arranged in rough polygons, caused by the shrinkage of drying clay, silt or mud. ◄ Modern mud cracks in Utah. Ancient mud cracks in Arizona. ► Mud Cracks

Sedimentary Rocks Image courtesy of U.S.Geological Survey. Page 17 The type of locale in which deposition occurs. May be terrestrial or marine. Each sedimentary environment produces a facies, or a set of characteristic sedimentary rocks and structures. Geologists study facies to determine past sedimentary environments. Sedimentary Environment River delta, Puget Sound, Washington. ►

Sedimentary Rocks Images courtesy of U.S. Geological Survey. Page 18 Pit dug into glacial till, Rocky Mountain National Park, Colorado. Meter-square cross section of a slab of Precambrian tillite from India. Glacial Environment

Sedimentary Rocks Right-hand image copyright © Society for Sedimentary Geology, courtesy of Earth Science World Image Bank. Page 19 Big Hunting Creek, Frederick County, Maryland. Enon Conglomerate, road cut near Port Elizabeth, South Africa. Mountain Stream Environment

Sedimentary Rocks Left-hand image copyright © Marli Miller, University of Oregon, courtesy of Earth Science World Image Bank. Right-hand image courtesy of U.S. Geological Survey. Page 20 Black Mountains, Death Valley, California.Conglomerate of carbonate clasts in red siltstone matrix, Leesburg Member of the Bull Run Formation, Loudoun County, Virginia. Mountain Front Environment

Sedimentary Rocks Left-hand image courtesy of National Park Service. Right-hand image courtesy of U.S. Geological Survey. Page 21 Great Sand Dunes National Park, Colorado. Cross bedding in the Navajo Sandstone, Zion National Park, Utah. Sand Dune Environment

Sedimentary Rocks Left-hand image courtesy of National Climatic Data Center. Right-hand image courtesy of Agriculture and Agri-Food Canada. Page 22 Lacustrine shale, British Columbia. ► Farewell Lake, southwest Alaska. Lake or Lacustrine Environment

Sedimentary Rocks Left-hand image copyright © Society for Sedimentary Geology. Right-hand image copyright © Bruce Molnia, Terra Photographics. Both images courtesy of Earth Science World Image Bank. Page 23 Gravel channel fill in bedded fluvial sands, near Mexico, Indiana. Kicking Horse River, near Field, British Columbia. River or Fluvial Environment

Sedimentary Rocks Left-hand image copyright © Society for Sedimentary Geology, courtesy of Earth Science World Image Bank. Right-hand image by Woodrow B. Thompson, used with permission of Page 24 Foreset beds in a glaciomarine delta, Lake Auburn, Maine. Delta deposited by glacial meltwater into Bow Lake, Banff National Park, Alberta, Canada. Delta Environment

Sedimentary Rocks Left-hand image copyright © Society for Sedimentary Geology, courtesy of Earth Science World ImageBank. Page 25 Trench cut into beach overwash deposits, Core Banks, North Carolina. Ancient tidal flat deposits, Summerville Formation, south- eastern Utah. Beach or Tidal Environment

Sedimentary Rocks Left-hand image courtesy of U.S. Geological Survey. Right-hand image copyright © Bruce Molnia, Terra Photographics, courtesy of Earth Science World Image Bank. Page 26 Permian reef limestone, Carlsbad Caverns National Park, New Mexico. ► Healthy modern coral reef, Kerama Islands, near Okinawa. Shallow Marine Environment

Sedimentary Rocks Image copyright © Roger Slatt, University of Oklahoma, courtesy of Earth Science World Image Bank. Page 27 Deep Marine Environment Turbidity Current –Bottom-flowing current, laden with suspended sediment, moving rapidly down a submarine slope. –Produces distinctive patterns of graded bedding. ◄ Turbidite, Santa Paula, California.

Sedimentary Rocks Images courtesy of U.S. Geological Survey. Page 28 Tectonically produced low area in Earth’s crust where thick sediments accumulate. Basins form where the lithosphere has been stretched or where nearby belts of thrusted crust weight it down. Sedimentary Basin

Sedimentary Rocks Image courtesy of U.S. Fish and Wildlife Service. Page 29 Sea level varies over time as continental glaciers and mid-ocean ridges grow and shrink. During a transgression, the sea level rises and the coastline moves inland. During a regression, the sea level drops and the coastline moves seaward. Alternating transgressions and regressions are often recorded in sedimentary basins. Changes of Sea Level Trees killed by sea-level rise, Blackwater National Wildlife Refuge, Maryland. ►