UNIVERSITY OF SOUTH ALABAMA
GY 402: Sedimentary Petrology
Lecture 5:
Bedform Development (Flume Studies)
Instructor: Dr. Douglas W. Haywick
Today’s Lecture
1. What’s a flume?
2. Traction induced bed forms (sedimentary structures)
3. Flow regime
Flume Studies
A flume is an elongated plastic or glass tank through
which a water current flows. Sediment is placed at the
bottom of the flume and moves down current as bed load.
Flume Studies
A flume is an elongated plastic or glass tank through
which a water current flows. Sediment is placed at the
bottom of the flume and moves down current as bed load.
Recall what this is
Sediment loads
Sediment moving along the base of a channel* that
mostly stays in contact with the substrate is called…
Current
* A channel here is defined as a moving column of water that is confined
to a narrow pathway
Sediment loads
Sediment moving along the base of a channel that
mostly stays in contact with the substrate is called…
Current
Bed load
Sediment loads
Sediment moving along the base of a channel that
mostly stays in contact with the substrate is called…
Current
Bed load
saltation
rolling
sliding
Types of bed load transport (traction)
Flume Studies
Flumes come in different sizes; from a few cm long to a
few hundred metres long.
Flume Studies
small
Flume Studies
small
Flume Studies
Big
Flume Studies
Big
Flume Studies
Flume Studies
Sand (bed load)
Sediment
movement
results in
bed forms
(sedimentary
structures)
Flume Studies
Increasing current velocity under controlled situations
(fixed water depth, constrained grain size) yields the
following structures:
Flume Studies
Increasing current velocity under controlled situations
(fixed water depth, constrained grain size) yields the
following structures:
Plan lamination (lower)
Flume Studies
Increasing current velocity under controlled situations
(fixed water depth, constrained grain size) yields the
following structures:
Plan lamination (lower)
Small current ripples
Flume Studies
Increasing current velocity under controlled situations
(fixed water depth, constrained grain size) yields the
following structures:
Plan lamination (lower)
Small current ripples
Large current ripples (dunes)
Flume Studies
Increasing current velocity under controlled situations
(fixed water depth, constrained grain size) yields the
following structures:
Plan lamination (lower)
Small current ripples
Large current ripples (dunes)
Plan lamination (upper)
Flume Studies
Increasing current velocity under controlled situations
(fixed water depth, constrained grain size) yields the
following structures:
Plan lamination (lower)
Small current ripples
Large current ripples (dunes)
Plan lamination (upper)
Antidunes
Flume Studies
Increasing current velocity under controlled situations
(fixed water depth, constrained grain size) yields the
following structures:
Plan lamination (lower)
Small current ripples
Large current ripples (dunes)
Plan lamination (upper)
Antidunes
Increasing
water velocity
Flume Studies
A do it yourself recipe to make your own flume
Flume Studies
Take one large tank….
The best flumes are capable of passing a consistent current from one end to the next.
Water is recycled through a recirculation pump
Sediment/water movement is monitored through the glass sides of the flume
Flume Studies
Add water….
Flume Studies
Add sediment….
Flume Studies
current
Add a current….
Flume Studies
current
Add a current….
…. Observe!
Flume Studies: 1) lower plan lamination
very slow currents (or none at all) U = very low
Flume Studies: 1) lower plan lamination
very slow currents (or none at all) U = very low
Flat bed, containing finely laminated* parallel
sedimentary structures
Flume Studies: 1) lower plan lamination
laminations versus bedding; it’s all a matter of scale:
Flume Studies: 1) lower plan lamination
laminations versus bedding; it’s all a matter of scale:
laminations: parallel layers less than 1 cm apart:
thick (1cm-5mm spacing);
medium (5mm-1mm spacing);
thin (<1mm spacing)
Flume Studies: 1) lower plan lamination
laminations versus bedding; it’s all a matter of scale:
bedding: parallel layers more than 1 cm apart:
thick (> 50 cm spacing);
medium (10 to 50 cm spacing);
thin (1cm-10 cm spacing)
Flume Studies: 2) small current ripples
slow currents:
Something wonderful happens….
U = low
Flume Studies: 2) small current ripples
Laminations start to fade…
Flume Studies: 2) small current ripples
Flat bed, passes gradually into a “rippled” bed form
Flume Studies: 2) small current ripples
Asymmetrical
Flume Studies: 2) small current ripples
Asymmetrical
Flume Studies: 2) small current ripples
Asymmetrical
Flume Studies: 2) small current ripples
Lee side slopes range from 20-34o
Flume Studies: 2) small current ripples
ripple height: 3 to 5 cm
Flume Studies: 2) small current ripples
ripple wavelength: 4 to 40 cm
Flume Studies: 2) small current ripples
ripple wavelength: 4 to 40 cm
Ripple index (height to wavelength ratio): 10 to 40
Flume Studies: 2) summary ripple morphology
From Collinson, J.D. and Thompson, D.B. 1982. Sedimentary Structures. George Allen & Unwin, 194p.
Flume Studies: 2) small current ripples
Ripples migrate down current
Flume Studies: 2) small current ripples
Ripples migrate down current
Flume Studies: 2) small current ripples
Ripples migrate down current
Flume Studies: 2) small current ripples
current
Net result is that an inclined lamination (marking the
former lee side of the ripple) develops
Flume Studies: 2) small current ripples
current
Net result is that an inclined lamination (marking the
former lee side of the ripple) develops
= cross stratification
Flume Studies: 2) small current ripples
Flume Studies: 2) small current ripples
?
Flume Studies: 2) small current ripples
Flume Studies: 2) small current ripples
Dune
fraction
Bypass
fraction
Flume Studies: 2) small current ripples
Big quartz
Small quartz
Heavy minerals
Which grains become
part of the dune
fraction; which ones
are part of the bypass
fraction?
Flume Studies: 2) small current ripples
Big quartz
Small quartz
Heavy minerals
Heavy and larger grains
usually become part of the
dune fraction; smaller and
lighter grains become part
of the bypass fraction
Flume Studies: 2) small current ripples
Migration direction
Flume Studies: 2) small current ripples
Migration direction
ripple cosets
Flume Studies: 2) small current ripples
Migration direction
steep angle
shallow angle
Flume Studies: 2) small current ripples
Migration direction
steep angle
depositional “up”
shallow angle
Flume Studies: 2) small current ripples
Video of ripple
migration in a
flume (Bird’ eye
view)
59 cm
38 cm
Click image to start
The movie was compiled
from 1161 video images
collected at the rate of 1 per
minute for a duration of
approximately 19 hours.
Source: USGS Coastal & Marine Geology Web page (http://walrus.wr.usgs.gov/seds/).
Flume Studies: 2) small current ripples
Computer
animation of
ripple migration
Click image to start
Source: USGS Coastal & Marine Geology Web page (http://walrus.wr.usgs.gov/seds/).
Flume Studies: current ripple crest morphology
increasing velocity (or decreasing water depth)
straight
sinuous
linguiodal
From Collinson, J.D. and Thompson, D.B. 1982. Sedimentary Structures. George Allen & Unwin, 194p.
Flume Studies: 3) large current ripples
Moderate currents
U = moderate
Flume Studies: 3) large current ripples
Moderate currents
U = moderate
Small current ripples gradually pass into larger ones
Flume Studies: 3) large current ripples
Lee side angle: 10 to 34o
Ripple height: >5cm (commonly exceeds 10’s of m)
Wavelength: 60 cm to 100’s of m
Note: also known as megaripples and dunes
Flume Studies: 4) upper plan lamination
High currents;
U = fast
Flume Studies: 4) upper plan lamination
High currents;
U = fast
Something wonderful happens again! Large current
ripples start to fade and….
Flume Studies: 4) upper plan lamination
…. plan lamination forms again
Flume Studies: 4) upper plan lamination
This form of plan lamination forms only during very fast
currents; sediment is literally streaming along the
substrate.
Flume Studies: 5) antidunes
Very high currents;
U = very fast
Flume Studies: 5) antidunes
Very high currents;
U = very fast
Upper plan lamination fades and is replaced by….
Flume Studies: 5) antidunes
Very high currents;
U = very fast
Upper plan lamination fades and is replaced by….
…. antidunes
summary of structures
From Collinson, J.D. and Thompson, D.B. 1982. Sedimentary Structures. George Allen & Unwin, 194p.
Flume Studies
Plan lamination (lower)
Small current ripples
Large current ripples (dunes)
Plan lamination (upper)
Antidunes
Chutes & pools (erosion)
From Collinson, J.D. and Thompson, D.B. 1982. Sedimentary Structures. George Allen & Unwin, 194p.
Increasing velocity
Flume Studies
Flume Studies and Flow Regime
From Collinson, J.D. and Thompson, D.B. 1982. Sedimentary Structures. George Allen & Unwin, 194p.
Flume Studies and Flow Regime
Lower
From Collinson, J.D. and Thompson, D.B. 1982. Sedimentary Structures. George Allen & Unwin, 194p.
Flume Studies and Flow Regime
Upper
From Collinson, J.D. and Thompson, D.B. 1982. Sedimentary Structures. George Allen & Unwin, 194p.
From Collinson, J.D. and Thompson, D.B. 1982. Sedimentary Structures.
George Allen & Unwin, 194p.
Current velocity (cm/s)
Modified Hjustrom’s diagram
Grain size (mm)
From Collinson, J.D. and Thompson, D.B. 1982. Sedimentary Structures.
George Allen & Unwin, 194p.
Water depth (cm)
Water depth as a variable
Upcoming Stuff
Homework
1) Writing Assignment 2-redo (Hypothesis and methods: Due Thursday)
Today’s Lab
Grain size analysis
Online:
Lecture 6: More Sedimentary Structures
Thursday:
Lecture 7: Sedimentary Sections
More!
GY 402: Sedimentary Petrology
Lecture 5: Bedforms
Instructor: Dr. Doug Haywick
dhaywick@southalabama.edu
This is a free open access lecture, but not for commercial purposed.
For personal use only.