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Paleocurrent Analysis
By: Jason Choquette
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OverviewWhy is paleocurrent analysis important?
Fabric and why its useful
Internal and external structures
How they are related to each other
Liner structures; types and uses
Practial study of paleocurrents in westernMaine and some implications
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DefinitionPaleocurrent- The study of ancient flow
Paleocurrent indicators- oriented
sedimentary structures interpreted to have
been deposited by ancient flows
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Paleocurrent Indicators IncludeCross-beds
clast imbrication/fabric
tool marks
groove casts and molds
ripple crest orientation
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Paleocurrent Analysis.Provides direct information about the orientation
of the sedimentary systems.Yields information about the flow directions ofrivers, longshore currents, sediment gravity flows,
and paleowindsProvides direction of initial dip or paleoslope
Yields clues to the provenance of sediment supply
Aids in determining geologic setting to which itwas placed
Provides info on paleogeography
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Three Maine flow IndicatorsFabric
External structures
Internal structures
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FabricsRefers to the spatial orientation of material
in which they where deposited.Includes various material types ranging in size
from large cobbles to micro-fabricsFossils
Encompasses other fields lithologies such as
carbonate rocks and volcanic deposits
Imbricated bedding
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Uses of fabric analysis
Largely used to infer current directions in
sand and gravels.
Reconstruct glacial motion
Primarily used if there is no other flow
indicators or to support other data.
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Compton Robert R. Geology in the Field, 1985 p.52
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Internal and External Structurese.g cross bedding and ripple marks
Used in unison to map large areas
Both are found in many geologic
environmentsFluvial
Littoral
Marine
Aeolian
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Some Internal Structures
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Some External Structures
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http://www.ualberta.ca/~jwaldron/images/sedCD1024/05.jpg
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http://www.depauw.edu/acad/geosciences/tcope/SedStruct/HiRes/LinguloidRipples.jpg
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http://www.coloradocollege.edu/dept/GY/pmyrow/Web%20Photos/Solemarks2.jpg
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https://reader009.{domain}/reader009/html5/0504/5aeb441227c9c/5aeb4
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http://www.studiozoic.com/adventures/2004/pct/wa/IMG_4153.jpg
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Paleocurrent Analysis in PracticeCombining internal and external structures
to develop a
Detailed map
Paleoslope
Tectonic history
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Potter, 1977
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Bradley;Hanson, 2002 p.442
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ReferencesLunguloid ripples jpeg from;
http://www.depauw.edu/acad/geosciences/tcope/SedStruct/HiRes/LinguloidRi
pples.jpgRipple marks
http://www.studiozoic.com/adventures/2004/pct/wa/IMG_4153.jpg
Bradley Dwight C., Hanson Lindley S., Paleocurrent analysis of a deformed
Devonian foreland basin in the Northern Appalachians, Maine, USA.Sedimentary Geology, 148 (2002) p.425- 447
Potter Paul E., Pettijohn Francis J., Paleocurrents and Basin Analysis, second
edition. Springer-Verlag, Berlin Hiedelberg New York, 1977
Lewis D.W. Practical Sedimentology, University of Canterbury NZ. 1984.
Compton Robert R., Geology in the Field. 1985 p. 52, 162-175
Class handout thingy
http://www2.umt.edu/GEOLOGY/faculty/hendrix/g432/g432_L12.htmhttp://www2.umt.edu/GEOLOGY/faculty/hendrix/g432/g432_L12.htmhttp://www.depauw.edu/acad/geosciences/tcope/SedStruct/HiRes/LinguloidRipples.jpghttp://www.depauw.edu/acad/geosciences/tcope/SedStruct/HiRes/LinguloidRipples.jpghttp://www.studiozoic.com/adventures/2004/pct/wa/IMG_4153.jpghttp://www.studiozoic.com/adventures/2004/pct/wa/IMG_4153.jpghttp://www.depauw.edu/acad/geosciences/tcope/SedStruct/HiRes/LinguloidRipples.jpghttp://www.depauw.edu/acad/geosciences/tcope/SedStruct/HiRes/LinguloidRipples.jpg