Sedimentary Facies & Sea Level
Sedimentary Facies
and
Sea Level Changes
Sedimentary Facies & Sea Level
Sedimentary Facies:
• general appearance or aspects
of a rock (composition & texture).
Sedimentary Facies & Sea Level
Sedimentary Facies:
• original environment of
deposition can be determined.
• used to describe vertical and
lateral variations in strata.
Sedimentary Facies & Sea Level
Sedimentary Facies:
• facies transform laterally by
gradual changes in their properties
into different, adjacent facies.
Sedimentary Facies & Sea Level
Two types of facies
1). Lithofacies:
distinguishing characteristics are
. . . lithologic
Sedimentary Facies & Sea Level
sandstone
facies
shale facies
Sedimentary Facies & Sea Level
Two types of facies
1). Lithofacies:
can be degree
of difference
limestone
sandstone
vs.
vs.
fine grained
limestone
coarse,
well sorted
sandstone
Sedimentary Facies & Sea Level
Two types of facies
2). Biofacies:
differences in biological (fossil)
composition.
Sedimentary Facies & Sea Level
Two types of facies
2). Biofacies:
• can have different adjacent
biofacies in the same lithology
• can be sensitive to small
environmental differences
Sedimentary Facies & Sea Level
Mississippi Delta
Foraminifera facies
Sedimentary Facies & Sea Level
Changes in sea level
Sedimentary Facies & Sea Level
Transgression:
• Advance of sea over the land
Regression:
• Retreat of the sea from the land
Sedimentary Facies & Sea Level
Idealized gradation:
• Near shore = coarse sediment
- to -
• Off shore = fine sediment
- yielding to -
• Shelf carbonate deposition
Sedimentary Facies & Sea Level
Idealized gradation:
continent
near
shore
off
shore
Sedimentary Facies & Sea Level
No sea level change:
continent
near
shore
off
shore
http://www.uh.edu/~jbutler/physical/transreg.gif
sediment through time
Sedimentary Facies & Sea Level
Sea level change: cross section
“the beach”
Sea level at Time A:
Sedimentary Facies & Sea Level
“the beach”
Sea level at Time B:
Sedimentary Facies & Sea Level
Transgression
• facies shift on-shore
• resulting rock unit (sandstone)
varies in age laterally
Sedimentary Facies & Sea Level
Transgression
• facies shift on-shore
• resulting rock unit (sandstone)
varies
in
age
laterally
“the beach”
“the beach”
Shift from
Time A to Time B:
Sedimentary Facies & Sea Level
Stand in one spot
during a transgression:
Time A: on the beach
(sandstone)
Sedimentary Facies & Sea Level
Stand in one spot
during a transgression:
Time B: underwater
(finer sediment)
Sedimentary Facies & Sea Level
Regression:
• facies shift off-shore
Sedimentary Facies & Sea Level
Regression:
• facies shift off-shore
“the beach”
Time A
“the beach”
Time B
Sedimentary Facies & Sea Level
Regression:
• in one place, facies become
more “onshore” (= coarser)
up section
course
Ss
Slt
fine
Ls
Sedimentary Facies & Sea Level
Regression
erosion
• In a vertical column,
Conglomerate
facies become
progressively more
"on shore" (coarser)
up section.
Sandstone
Siltstone
Limestone
Sedimentary Facies & Sea Level
Regression
erosion
“land”
Conglomerate
• In a vertical column,
facies become
“beach”
progressively more
"on shore" (coarser)
up section.
Sandstone
Siltstone
“deep”
Limestone
Sedimentary Facies & Sea Level
Transgression
• In a vertical column,
facies become
progressively more
”off shore" (finer)
Limestone
Siltstone
Sandstone
Conglomerate
up section.
erosion
Sedimentary Facies & Sea Level
Transgression
• In a vertical column,
“deep”
Siltstone
facies become
progressively more
“beach”
”off shore" (finer)
up section.
Limestone
Sandstone
Conglomerate
“land”
erosion
Sedimentary Facies & Sea Level
Walther’s Law
• A vertical sequence represents
facies that were once laterally
continuous
vertical
sequence
Limestone
Siltstone
Sandstone
Sedimentary Facies & Sea Level
Walther’s Law
• A vertical sequence represents
facies that were once laterally
continuous
vertical
sequence
Limestone
Siltstone
Sandstone
Lateral Distribution
Walther’s Law
• A vertical sequence
Ss
represents facies that
Sh
were once laterally
Ls
continuous
Walther’s Law
• A vertical sequence
Ss
represents facies that
Sh
were once laterally
Ls
continuous
“beach”
“deep”
Sedimentary Facies & Sea Level
Walther’s Law
• The relative sequence is more
important than absolute
completeness.
vertical
sequence-1
vertical
sequence-2
Limestone
unconformity
Sandstone
Siltstone
Sedimentary Facies & Sea Level
Walther’s Law
• The relative sequence is more
important than absolute
completeness.
vertical
sequence-1
“deep”
Limestone
“beach”
Sandstone
vertical
sequence-2
“land”
unconformity
Siltstone
“intermediate”
Transgression
Regression
Sedimentary Facies & Sea Level
What cause a Transgression?
• Tectonic subsidence
(sinking)
• Rise in sea level
• Erosion of shore line
Sedimentary Facies & Sea Level
What cause a Regression?
• Tectonic uplift
• Drop in sea level
• Over supply of sediment
Sedimentary Facies & Sea Level
Eustatic sea level change
(world wide) - causes?
1. Continental Glaciation
more ice = lower sea level
(max. 200 meter change)
http://www.shiftingbaselines.org/blog/archives/000430.html
1 meter rise
http://www.shiftingbaselines.org/blog/archives/000430.html
2 meter rise
http://www.shiftingbaselines.org/blog/archives/000430.html
6 meter rise
30 meter rise
100 meter rise
link to: USGS
Sedimentary Facies & Sea Level
Eustatic sea level change
(world wide)
- causes?
2. Plate Tectonics
fast spreading rate
= high sea level
slow = low sea level
(affects the shape of ocean basins)
Sedimentary Facies & Sea Level
Local sea level change
• transgression in one place
while regression in another
• local mountain uplift
or crustal subsidence
• very rapid influx of sediment
or erosion.