Jarðsaga 1 - Saga lífs og lands – Ólafur Ingólfsson Sedimentary Rocks and Sedimentary Environments Sedimentary Rocks are the Principal Repository for Information About the Earth’s Past Environment Earth’s history largely read from sedimentary strata

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Erosion Sedimentary Sediment Rocks

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Sedimentary Rocks Clastic Rocks (molaberg) • Made of Fragmentary Material • Deposited by – Water (Most Common) –Wind Chemical-Biological –Glacial Action Sedimentary Rocks –Gravity •Evaporation •Precipitation • Biogenic Sediments Sedimentary Rocks

Clastic Rock – composed of fragments of preexisting rocks.

Nonclastic Rock – composed of chemical precipitates or biogenic matter. Sediment Sizes and Clastic Rock Types

Rock Type Sediment Grain Size Shale Clay less than 0.001 mm Siltstone Silt .001-0.1 mm Sandstone Sand .01-1 mm Conglomerate Gravel 1mm +

Sedimentary rocks made of silt- and clay-sized particles are collectively called mudrocks, and are the most abundant sedimentary rocks. Clastic Sediment Size Some Special Clastic Rock Types

• Arkose Feldspar-Rich • Breccia Angular Fragments • Graywacke Angular, Immature Sandstone Classification of Clastic Sedimentary Rocks Major types of sandstone based on mineral/rock content Quartzite Arkose Lithic Sandstone Greywacke Chemical-Biological Sediments

Evaporites -Water Alteration After Soluble Deposition •Halite • Limestone ⇨ Dolomite •Gypsum Biogenic Sediments • Calcite • Limestone - Shells, Precipitates Reefs, Etc. •Gypsum Organic Remains • Limestone •Coal • Iron Formations • Petroleum Biogenic Sediments Terestrial Sediments - mainly plant matter Marine Sediments -mainly carbonates Corals - Large components of reefs. Bivalves, Gastropods (sníglar), Foraminifers (götungar) - Whole or partial skeletons form sand and gravels. Algae, Crinoids (sælilja), Echinoderms (skrápdýr), Bryozoans (mosadýr) - disintergrate to form some sand particles and lime mud. Diatoms (kísilþörungar), Radiolaria (geislungar) – Bedded chert SiO2 Conglomerate (völuberg) Sandstone Coal

Shale (leirskífur) Limestone (kalksteinn) Arkose

Some major types of sedimentary rocks Limestone Gypsum

Environmental Clues in Sedimentary Rocks • Grain Size - Power of Transport Medium • Grading - Often Due to Floods • Rounding } Transport, Reworking • Sorting • Cross-bedding - Wind, Wave or Current Action Features in sedimentary rocks

Sand grains show evidence of transport fossil fish

ripple marks formed by Mud cracks wind or wave action Bedding or Stratification • Almost Always Present in Sedimentary Rocks • Originally Horizontal • Tilting by Earth Forces Later • Variations in Conditions of Deposition • Size of Beds (Thickness) – Usually 1-100 cm – Can Range From Microscopic to 50m • Sedimentary rocks commonly show layering that form as sediment is deposited Sedimentary – Stratification (lagskifting) structures – cross bedding (skálögun) – graded bedding (lóðgreining) Cross bedding is wind wind Migration of the dune formed by the migration of windward leeward sand waves (ripple marks or dunes) by sand particles travelling up the windward face and depositing down the leeward face Graded bedding

• Graded bedding can be produced by turbidity currents, which can travel up to 100 As the current slows km/hr the coarse grains are – currents can be started by deposited first,followed landslide or earthquake down the by successively finer- continental slope grained sediments – deposition based on density (gravity) and settling velocity Environmental Clues in Sedimentary Rocks

• Fossils – Salt Water - Corals, Echinoderms (skrápdýr) – Fresh Water - Insects, Amphibians – Terrestrial - Leaves, Land Animals • Color And Chemistry – Red Beds - Often Terrestrial – Black Shale - Oxygen Poor, Often Deep Water – Evaporites – Arid Climates Each kind of sedimentary environment on Earth’s surface is characterized by particular kinds of sediment and patterns of bedding

• Sediments are deposited in a variety of places. • Each is characterized by a combination of the kind and amount of water, the local topography, and the biological activity. • These in turn are related to plate tectonic setting and climate. • Although sediment can be deposited anywhere, large accumulations of sediment are not, being found in only a handful of environments. Common Sedimentary Environments:

Non-marine environments Stream sediments, Lake sediments, Glacial (ice deposited) sediments, Eolian (wind deposited) sediments

Continental Shelf sediments Estuarine sediments, Deltaic sediments, Beach sediments, Carbonate shelf sediments, Marine evaporite sediments

Continental slope and rise sediments Turbidites, Deep Sea Fans, Sediment drifts

Deep Sea Sediments Deep -Sea oozes, Land-derived sediments Major sedimentary environments

fluvial alluvial tidal • Sedimentary fan beach flat environments dunes glacier delta barrier lake island encompass the physical, chemical, and biological Shallow marine conditions in areas deep marine organic reef where sediment is organic deposited. These reef comprise three distinct groups: 1) continental, • weathering - physical and chemical • transportation - wind, water, and ice 2) shoreline –sorting (transitional), • deposition 3) marine Sedimentary Environments

Shoreline Environments Deltaic Continental (land-based) Tidal flat Environments Beach Alluvial Marine Environments Desert Continental shelf Lake Continental slope Glacial Organic reefs Deep-sea Continental sedimentary environments – Classification Chart

Alluvial Fan Fluvial Lacustrine Dunes

Rock type Breccia, Conglomerate, Siltstone, Quartz arenite conglomerate, sandstone, shale,limestone (sandstone) or arkose siltstone, shale or evaporites gypsum Composition Terrigenous Terrigenous Terrigenous, Terrigenous or carbonate, or evaporite evaporite Grain Size Clay to gravel Clay to gravel Clay to silt or Sand (Fining upward) sand (Coarsening upward) Grain Shape Angular Rounded to ----- Rounded angular Sorting Poor Variable Variable Good Sedimentary Cross-bedding Asymmetrical Symmetrical Cross-bedding and graded ripples,cross- ripples, Structures bedding bedding,graded lamination, bedding,tool cross-bedding, marks graded bedding (http://www.dc.peachnet.edu/~pgore/geology/historical_lab/environmentchart.htm) Transitional sedimentary environments

BARRIER LAGOON TIDAL FLAT DELTA BEACH Rock Type Sandstone, Quartz Siltstone, Siltstone, shale, calcilutite, siltstone, arenite, shale, dolostone or gypsum shale, coal coquina limestone Composition Terrigenous Terrigenous Terrigenousc Terrigenous, carbonate, or or carbonate arbonate, or evaporite evaporite Grain Size Clay to sand Sand Clay to silt Clay to silt Grain Shape --- Rounded to ------angular Sorting Poor Good Poor Variable Inorganic Cross- Cross- Lamination, Lamination, mudcracks, ripples, Sedimentary bedding, bedding, ripples, cross-bedding Structures graded symmetrical cross- bedding ripples bedding Organic or Trails, Tracks, Trails, Stromatolites, trails, tracks, Biogenic burrows trails, burrows burrows Sedimentary burrows Structures Fossils Plant Marine shells Marine shells Marine shells fragments, shells Marine sedimentary environments

CONTINENTAL CONTINENTAL SLOPE AND REEF SHELF RISE Rock Type Fossiliferous Sandstone, shale, Litharenite, siltstone, and shale limestone siltstone, (or limestone) fossiliferous limestone, oolitic limestone Composition Carbonate Terrigenous or Terrigenous or carbonate carbonate Grain Size Variable, Clay to sand Clay to sand framework, few to no grains Grain Shape ------Sorting --- Poor to good Poor Inorganic --- Lamination, cross- Graded bedding, cross-bedding, Sedimentary bedding lamination, flute marks, tool Structures marks (turbidites) Organic or --- Trails, burrows Trails, burrows Biogenic Sedimentary Structures Fossils Corals, marine Marine shells Marine shells, rare plant shells fragments • Continental glaciers greatly modify the entire landscape they cover. Flowing ice Continental removes and transports soil and bedrock, glacier and transports it long distances. Supraglacial debris system

outwash proglacial plain subglacial till lake plucking abrasion

moraine

iceberg

Surface tilts towards glacier dropstones

Isostatic subsidence Glacial landforms and sediments Glacial till Glacial varves •Geological fingerprinting of continental scale glaciations is very important in

Moraine terrain Esker paleogeographical reconstructions –

•Distribution of glacial tills used early on to argue for Continental Drift drumlin outwash plain The glacial environment • Glaciers generally create poorly sorted Margins of a valley Ancient glacial sediments sedimentary glacier in Canada (diamictite) in Utah rocks The delta environment • Deltas (óseyri) form a variety of rock types, depending on the environment of Minor delta in the Ancient delta deposit Great Bear Lake, Canada in the Colorado Plateau deposition. Deltas

• The history of the Mississippi delta involves repeated switching of the main channel. Previous deltas are numbered (1-6) by age from oldest to youngest. River systems and tectonics

• The evolution of the major rivers of the world is influenced directly and indirectly by plate tectonics. The fluvial environment • Rivers are the major channels by which erosional debris is transported from the continents to the oceans. • River deposits are characterized by channels of sand or gravel. • River deposits are typically graded due to channel migration and a decrease in flow energy

Point bar deposits in Ancient stream channel a meandering river in Utah River systems

• Running water is by far the most important agent of erosion. Other agents, such as groundwater, glaciers, and wind, are locally dominant but affect only limited parts of the Earth’s surface.

The evolution of stream meanders The major features of a floodplain

• In the lower parts of the drainage system, the gradient of a river is very low. As a result the velocity of the river is reduced and deposition of much of the sediment load occurs, to create – Floodplains (flæðiland) – alluvial valleys (árdalir) – Deltas (óseyrar) – alluvial fans (árkeilur) Alluvial Fans

Modern alluvial fan Ancient alluvial fan in Death Valley, CA deposit in Utah The eolian (wind) environment

• Wind is a very effective sorting agent separating mud, silt, and Modern sand dunes Ancient dune deposits gravel from sand in the Sahara Desert in Zion National Park The desert environment Deserts should more correctly be called arid regions. Arid and semi- arid regions characteristically receive less than 50-100 mm of precipitation/year, and often the amount of evaporation is greater than the amount of rainfall. One-third of the earth's land mass is arid to semiarid (either desert or semidesert). Locations of deserts have changed throughout geologic time as the result of continental drift and the uplifting of mountain ranges. Modern desert regions are centered between 15 and 30 degrees north and south of the equator and in the Polar regions Sorting by Wind

Enormous loess deposits, composed of long-transported aeolian silt, common on continents – China Wetlands environments

It is no accident that river valleys and their floodplains have been the focus of human civilisations for over 6,000 years. This simply reflects the key role that water and wetlands have played throughout the development of life on planet Earth. The beach and lagoon environments

A modern beach An ancient beach •Much sediment on the Atlantic coast deposit in Utah accumulates in zones where land meets the sea; the type of sedimentary rock formed is dependent on the energy of the fluid environment.

A lagoon along USA Ancient lagoon deposits Atlantic coast in eastern Wyoming Shoreline systems

• Shorelines are dynamic systems involving the energy of waves and currents. • Wind-generated waves provide most of the energy for erosion, transportation and deposition of sediment. • Waves approaching a shore are bent, or refracted, so that energy is concentrated on headlands and dispersed in bays Output to Input from rivers backshore dunes Deposition Output to beaches Input from cliff erosion along coasts

Output to deep water

Output to spits and bars

• Sediment transported along the shore is deposited in areas of low wave energy, A barrier island can form by and results in various landforms the migration of a spit – beaches –spits – barrier islands The tidal flat and reef environment

• Tidal flats (leirur) Modern tidal flat in Ancient tidal flat the Gulf of California deposit in Utah are alternately covered with shallow water and exposed to air. • Organic reefs are solid structures of calcium carbonate constructed of shells and secretions An organic reef on Ancient Devonian reef of organisms. Moorea near Tahiti in Australia • Reefs form a unique coastal feature since they are biological in origin. • Modern reefs are built by a complex community of coral, algae, sponges and other marine invertibrates • most reefs grow in warm, clear, shallow waters in tropical regions

Volcanic island surrounded by a fringing reef

Reef mounds are The global distribution of modern visible through the coral reefs Community of shallow waters in the organisms in a reef lagoon Types of reefs

A fringe reefs first begins to • Fringing reefs grow along the coast of a newly- (jaðar-) formed volcanic • Barrier reefs island (hindrunar-) • platform reefs As the island subsides, the reef (pall-) grows upward and develops a barrier • atolls (hringey) - separating the ring structured lagoon from open water reef. • Darwin was first to Further propose how an subsidence completely atoll might have submerges the formed, in 1842 on island while the reefs continues to the voyage of the grow Beagle. The shallow and deep marine environment

• Shallow marine The shallow marine Ancient shallow marine environments border environment in the sediments in Kansas most land area, Bahamas forming sandstones, shales, and limestones. • Deep ocean sediments are derived from turbidites and the constant rain of carbonate and silica Seismic reflection of Ancient turbidites on deep sea fans off the the southern coast of from shallow oceans. Indian coast France Shallow-marine and continental shelf environment

Open continental shelves display a variety of physical conditions and therefore produce a variety of sedimentary deposits. • Tidal currents and wave motion produce sandy bottoms • On more quiet shelves, muddy sands accumulate Very important environment for development of life! sand mud Sea expands over the land (transgression) shoreline lime Stratigraphic sequences - example of a transgression- regression cycle

Sea moves back from the land (regression)

Exposure of a transgressive regressive cycle Interpretation of ancient sedimentary environments Barier Alluvial Shallow fan River island Lagoon marine Delta

Conglomerate Coal Sandstone Shale Limestone • Sedimentary rocks are products of the hydrologic system and interaction with Earth’s crust. • They provide a record of changing surface environments. • Plate tectonics has a profound influence on the origin of sedimentary rocks. • Each tectonic setting produces a distinctive sequence of sedimentary rocks. Stratigraphical mapping - The purpose of stratigraphical mapping is to get a sense of the physical and petrographic properties of rocks and interpret in terms of geological events or environments - Lithostratigraphy: Describes and defines units of rocks on the basis of lithological characteristics.

Unit boundaries, textures (samsetning), structures (bygging), fossils Additional reading, some good web-sites, references used when prepating this lecture:

Stanley: Earth System History, chapter 5. http://www.virtual-geology.info/FILTER/intro.html#templates http://gpc.edu/~pgore/geology/historical_lab/environmentchart.htm http://www.es.ucsc.edu/~jsr/EART10/Lectures/HTML/lecture.05.html http://www.bhc.edu/academics/science/harwoodr/Geol101/study/sediment.htm http://www.amateurgeologist.com/content/glossary/rock/sedimentary.html#sedimentary http://www.homepage.montana.edu/~esci111/RockCycle-1/sedimentary.htm#clastic http://csmres.jmu.edu/geollab/Fichter/SedRx/SedEnvir.html#sedenvir http://www.uwgb.edu/dutchs/EarthSC202PowerPoint/5 http://www.uic.edu/classes/geol/eaes350/1 http://www.surrey.ac.uk/eng/InfoPoint/downloads/civ/SE1122/1 http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Sedrocks/Sedrocks1.html