7. Sedimentary Environments

Chapter 7 Sedimentary Environments

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Sedimentary environments Sedimentary  environments

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N. Ramos | Geology 11 Principles of Geology

Lecture Notes: Sedimentary Rocks

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Sedimentary environments

Sedimentary facies  A mass of sedimentary rock which can be defined and distinguished from others by its geometry, lithology, sedimentary , .

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N. Ramos | Geology 11 Principles of Geology

Lecture Notes: Sedimentary Rocks

Sedimentary environments

Methods of environmental diagnosis

Lithology Sedimentary stru ctures

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Lecture Notes: Sedimentary Rocks

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moorlandschool.co.uk/earth/earth _science/utah_sandstone.jpg Lecture Notes: Sedimentary Rocks

Streams river, creek, tributary, runnel, lick, rill, river, bayou, rivulet, streamage, wash, gill (occasionally ghyll), gully; beck, bourne, brook, burn, nant, stream, syke, allt (UK); kill, run, branch, fork, prong, falls, crick (USA)

3.bp.blogspot.com/_1BZgZVkngwU/TBzOqaN_L4I/AAAAAAAAAEM/bFeRtsCk9Ac/s1600/STREAM+%282%29.jpg N. Ramos | Geology 11 Principles of Geology

Lecture Notes: Sedimentary Rocks

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Fluvial environments

Stream load

www.sci.uidaho.edu/scripter/geog100/lect/11-rivers/11-09-fluvial-transport.jpg

Competence biggest size of grain that a stream can move Capacity maximum amount of debris that a stream can move N. Ramos | Geology 11 Principles of Geology

Lecture Notes: Sedimentary Rocks

Fluvial environments

Stream f low laminar flow

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turbulent flow

Lecture Notes: Sedimentary Rocks

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Fluvial environments

River channels bedrock c hannel and alluvi al channel

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Lecture Notes: Sedimentary Rocks

Fluvial environments

Knickpoint a sharp change in channel slope, such as a waterfall or lake, resulting from differential rates of erosion above and below the knickpoint

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Lecture Notes: Sedimentary Rocks

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Fluvial environments: Alluvial channels

Straight - have a low sinuosity index - generally lack the typical features of meandering rivers, e.g. point bars Waal River, Netherlands

www.geo.uu.nl/fg/palaeogeography/pictures/results_fluvialstyle/03_Waal.jpg N. Ramos | Geology 11 Principles of Geology

Lecture Notes: Sedimentary Rocks

Fluvial environments: Alluvial channels

Meandering the most stable and efficient channel geometry, formed and maintained by erosion of banks and deposition on point bars Williams River, Alaska

deep, narrow channels

,

few channel islands wattsupwiththat.files.wordpress.com/2009/12/oxbow-lakes1.png N. Ramos | Geology 11 Principles of Geology

Lecture Notes: Sedimentary Rocks

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Fluvial environments: Alluvial channels

Meander parameters

Sinuosity index quantitative measurement of the style of meandering

hydrotopics.files.wordpress.com/2010/10/meandergeometry1.jpg N. Ramos | Geology 11 Principles of Geology

Lecture Notes: Sedimentary Rocks

Fluvial environments: Alluvial channels

Helical f low pattern - develops from the outside of the meander bend towards the inside of the bend - erodes sediment from the outside bend and deposits point bars on the inside bend

Huggett, 2011 N. Ramos | Geology 11 Principles of Geology

Lecture Notes: Sedimentary Rocks

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Fluvial environments: Alluvial channels

Incised m eanders occur when a meandering river on alluvium eats down into the underlying bedrock Goosenecks at San Juan River, USA (UT)

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Lecture Notes: Sedimentary Rocks

Fluvial environments: Alluvial channels

Braided multiple superimposed meandering channels as discharge and sediment load vary seasonally and diurnally, e.g. semiarid and proglacial streams Slims River, Canada

wide, shallow channels , channels

numerous islands www.geo.uu.nl/fg/palaeogeography/pictures/results_fluvialstyle/01_Slims-River.jpg N. Ramos | Geology 11 Principles of Geology

Lecture Notes: Sedimentary Rocks

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Fluvial environments

Drainage network or pattern  Arrangement o f s tr eams i n a dr ainage, w hich o ft en reflect s str uctu ral and/or lithologic control of underlying rocks  Analysi s enables int erpretati on and identi fi cat ion of geologic st ruct ures and rock t ypes in an area

Howard, 1967 www.epa.gov/owow/watershed/wacademy/acad2000/stream/s28.jpg N. Ramos | Geology 11 Principles of Geology

Lecture Notes: Sedimentary Rocks

Fluvial environments: Drainage network 

Dendritic Branching of stream valleys at acute angles without systematic arrangement Determined by random headward erosion underlying material

 homogeneous

→

Common on horizontally bedded sedimentary rocks or massive igneous/metamorphic rocks

courses.missouristate.edu/emantei/creative/WeathStrem/dendri tic.jpg   64.19.142.10/home.moravian.edu/users/phys/mejjg01/geology/ geology%20pages/geo_map_folder/geo_map_images/m_dendri ticA1.jpg N. Ramos | Geology 11 Principles of Geology

Lecture Notes: Sedimentary Rocks

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Fluvial environments: Drainage network 

Trellis Nearly parallel streams that flow into main trunk streams at high angles Subsequent in origin

 channels are etched out of weaker rock

→

Common on tilted sedimentary beds

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Lecture Notes: Sedimentary Rocks

Fluvial environments: Drainage network 

Rectangular  Tributary streams join trunk streams at right angles as a result of subsequent streams adjusting to fault or joint systems Usually formed on jointed/faulted rocks

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Lecture Notes: Sedimentary Rocks

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Fluvial environments: Drainage network 

Radial Consequent streams flowing from a central area in all directions; Streams converging into a central basin/depression form a centripetal drainage pattern Usually developed on high, recently formed land surfaces (e.g., volcanic cones or intrusive domes)

earth.jsc.nasa.gov/sseop/images/EFS/lowres/STS068/STS068 -253-7.jpg

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Lecture Notes: Sedimentary Rocks

Fluvial environments: Drainage network 

 An nular  Streams that follow circular courses due to the erosion of alternating weak and resistant sedimentary rocks of domes

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Lecture Notes: Sedimentary Rocks

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Fluvial environments: Drainage network 

Parallel Streams follow nearly parallel directions Usually controlled by unidirectional regional slope or by parallel to subparallel topographic features

resweb.llu.edu/rford/courses/ESSC500 /fluvial_slides/cuesta2.jpg N. Ramos | Geology 11 Principles of Geology

Lecture Notes: Sedimentary Rocks

Fluvial environments

Floodplain - the surface of low relief adjacent to a stream that becomes the stream bed during flood - features include meander scars, levees, and oxbow lakes

www.uwec.edu/jolhm/EH/Disrude/images/floodplain.gif 

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www.sci.uidaho.edu/scripter/geog100/lect/11-rivers/11-18-riverfloodplain.jpg

Lecture Notes: Sedimentary Rocks

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Fluvial environments

 All uvial fan - low, triangular-shaped deposits built from the accumulation of sediments deposited at the mouth of a valley (i.e., from a mountainous or upland into a larger mainstream valley or lowland) , , the source area, (4) tectonic activity, (5) space available for fan growth Death Valley, USA (CA)

www.windows2universe.org/earth/geology/images/alluvial_fan_lg.jpeg N. Ramos | Geology 11 Principles of Geology

Lecture Notes: Sedimentary Rocks

Fluvial environments

Delta - similar morphology to an alluvial fan but deposition results from sharp reduction in velocity as a stream enters standing water

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www.gly.uga.edu/railsback/1121DeltaTypes.jpeg N. Ramos | Geology 11 Principles of Geology

Lecture Notes: Sedimentary Rocks

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Fluvial environments

Delta lobe switchi ng

64.19.142.12/upload.wikimedia.org/wikipedia/commons/c/c2/Mississippi_Delta_Lobes.jpg N. Ramos | Geology 11 Principles of Geology

Lecture Notes: Sedimentary Rocks

Fluvial environments

Delta - similar morphology to an alluvial fan but deposition results from sharp reduction in velocity as a stream enters standing water Topset beds - horizontal layers of smaller sediment size that form as the main channel of the river shifts elsewhere and the larger particles of the bed load are no longer deposited

load that the river is moving along which consists of larger sediments that roll along the main channel

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Bottomset beds - created from the suspended sediment that settles out of the water as the river flows into the body of water and loses energy N. Ramos | Geology 11 Principles of Geology

Lecture Notes: Sedimentary Rocks

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