This document discusses paleocurrent analysis, which is the study of ancient sediment flows. Paleocurrent analysis provides information about the orientation of ancient sedimentary systems and flow directions. It can indicate the direction of rivers, currents, sediment gravity flows, and winds in the past. Paleocurrent indicators include cross-beds, clast imbrication, tool marks, and ripple orientations, which can be analyzed individually or together. Fabric analysis and studying internal and external sedimentary structures are important techniques. The document provides examples of these techniques and how paleocurrent analysis has been applied to study areas in western Maine.

1. Paleocurrent Analysis
By: Jason Choquette

2. Overview
Why is paleocurrent analysis important?
Fabric and why it’s useful
Internal and external structures
How they are related to each other
Liner structures; types and uses
Practial study of paleocurrents in western
Maine and some implications

3. Definition
Paleocurrent- The study of ancient flow
Paleocurrent indicators- oriented
sedimentary structures interpreted to have
been deposited by ancient flows

4. Paleocurrent Indicators Include…
Cross-beds
clast imbrication/fabric
tool marks
groove casts and molds
ripple crest orientation

5. Paleocurrent Analysis….
Provides direct information about the orientation
of the sedimentary systems.
Yields information about the flow directions of
rivers, longshore currents, sediment gravity flows,
and paleowinds
Provides direction of initial dip or paleoslope
Yields clues to the provenance of sediment supply
Aids in determining geologic setting to which it
was placed
Provides info on paleogeography

6. Three Maine flow Indicators
Fabric
External structures
Internal structures

7. Fabrics
Refers to the spatial orientation of material
in which they where deposited.
Includes various material types ranging in size
from large cobbles to micro-fabrics
Fossils
Encompasses other fields lithologies such as
carbonate rocks and volcanic deposits
Imbricated bedding

8. 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.

9. www2.umt.edu/.../hendrix/g432/g432_L12.htm

10. Compton Robert R. Geology in the Field, 1985 p.52

12. Internal and External Structures
e.g cross bedding and ripple marks
Used in unison to map large areas
Both are found in many geologic
environments
Fluvial
Littoral
Marine
Aeolian

14. Some Internal Structures

15. www2.umt.edu/.../hendrix/g432/g432_L12.htm

19. Some External Structures

20. www2.umt.edu/.../hendrix/g432/g432_L12.htm

22. http://www.ualberta.ca/~jwaldron/images/sedCD1024/05.jpg

24. http://www.depauw.edu/acad/geosciences/tcope/SedStruct/HiRes/LinguloidRipples.jpg

25. http://www.coloradocollege.edu/dept/GY/pmyrow/Web%20Photos/Solemarks2.jpg

26. http://www.ulg.ac.be/geolsed/processus/tool.jpg

27. http://www.studiozoic.com/adventures/2004/pct/wa/IMG_4153.jpg

29. Paleocurrent Analysis in Practice
Combining internal and external structures
to develop a…
Detailed map
Paleoslope
Tectonic history

30. Potter, 1977

31. Bradley;Hanson, 2002 p.442

34. References
Lunguloid ripples jpeg from;
http://www.depauw.edu/acad/geosciences/tcope/SedStruct/HiRes/LinguloidRi
pples.jpg
Ripple 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…