A SeqStrat 1
SS
SS
GDE
gross depositional environment
causes of transgression and regression
transgression-rise in sea level causes coastline to shift landwards
regression-Stationary sea level, with adequate sediment supply, causes coastline to shift basinwards. Fall in sea level also causes regression, but with more abrupt upwards increase in grain size.
Milankovitch cycles
Eccentricity 100ka (orbit ovalness)
Obliquity 41ka (axis tilt magnitude)
Precession 22ka (axis tilt direction)
(alpahabetical)
defiition of 'sequence'
A genetically-related package of sediments bounded at its top and base by unconformities
4 factors influencing sequence development
sediment supply
subsidence
eustacy
climate
sigmoids
clinoforms
offlap break
.
bottomset/topset
.
transgressive vs. retrogradational
transgressive=shore line moving landwards
retrogradational=shore line moving landwards during continused sedimentation
aggradational
.
terminology
both progradational
Seismic reflector boundaries
truncation
toplap
downlap
onlap
apparent truncation
.
labels
.
incised valley associated with which systems tract
lowstand
which systems tract?
lowstand
which systems tract?
lowstand
which systems tract?
transgressive
which systems tract?
transgressive
which systems tract?
highstand
which systems tract
highstand
MFS
maximum flooding surface
between which systems tracts does the MFS lie
transgressive and highstand
three main systems tracts
lowstand transgressive and highstand
idealised systems tract diagram
.
Two subsets of sequence boundary
Type 1
Type 2
How are the two subsets of systems boundaries differentiated?
whether sea lvel drops below the level of the offlap (shelf) break
offlap break
shelf break
type 1 sequence boundary definition
(4 defining factors)
A regional surface characterized by subaerial exposure and concurrent subaerial erosion associated with stream incision, a basinward shift in facies, a downward shift in coastal onlap to the offlap break (i.e. to the depositional shoreline), and onlap of overlying strata
type 1 sequence boundary diagram
.
parasequence
sub-sequence
well log responce of type 1 boundary
.
well log responce of parasequence
.
Type 2 sequence boundary definition
A regional surface marked by subaerial exposure and a downward shift in coastal onlap landward of the offlap (depositional shoreline) break
issue observing any subaerial erosion by stream rejuvenation (incision)
Note that seismic resolution is frequently insufficient to resolve it
type 1 vs. type 2 coastal shift?
type 1:downward shift in coastal onlap to the offlap (depositional shoreline) break
type 2: downward shift in coastal onlap landward of the offlap (depositional shoreline) break
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Cartes-fiches
GDE
gross depositional environment
causes of transgression and regression
transgression-rise in sea level causes coastline to shift landwards
regression-Stationary sea level, with adequate sediment supply, causes coastline to shift basinwards. Fall in sea level also causes regression, but with more abrupt upwards increase in grain size.
Milankovitch cycles
Eccentricity 100ka (orbit ovalness)
Obliquity 41ka (axis tilt magnitude)
Precession 22ka (axis tilt direction)
(alpahabetical)
defiition of 'sequence'
A genetically-related package of sediments bounded at its top and base by unconformities
4 factors influencing sequence development
sediment supply
subsidence
eustacy
climate
sigmoids
clinoforms
offlap break
.
bottomset/topset
.
transgressive vs. retrogradational
transgressive=shore line moving landwards
retrogradational=shore line moving landwards during continused sedimentation
aggradational
.
terminology
both progradational
Seismic reflector boundaries
truncation
toplap
downlap
onlap
apparent truncation
.
labels
.
incised valley associated with which systems tract
lowstand
which systems tract?
lowstand
which systems tract?
lowstand
which systems tract?
transgressive
which systems tract?
transgressive
which systems tract?
highstand
which systems tract
highstand
MFS
maximum flooding surface
between which systems tracts does the MFS lie
transgressive and highstand
three main systems tracts
lowstand transgressive and highstand
idealised systems tract diagram
.
Two subsets of sequence boundary
Type 1
Type 2
How are the two subsets of systems boundaries differentiated?
whether sea lvel drops below the level of the offlap (shelf) break
offlap break
shelf break
type 1 sequence boundary definition
(4 defining factors)
A regional surface characterized by subaerial exposure and concurrent subaerial erosion associated with stream incision, a basinward shift in facies, a downward shift in coastal onlap to the offlap break (i.e. to the depositional shoreline), and onlap of overlying strata
type 1 sequence boundary diagram
.
parasequence
sub-sequence
well log responce of type 1 boundary
.
well log responce of parasequence
.
Type 2 sequence boundary definition
A regional surface marked by subaerial exposure and a downward shift in coastal onlap landward of the offlap (depositional shoreline) break
issue observing any subaerial erosion by stream rejuvenation (incision)
Note that seismic resolution is frequently insufficient to resolve it
type 1 vs. type 2 coastal shift?
type 1:downward shift in coastal onlap to the offlap (depositional shoreline) break
type 2: downward shift in coastal onlap landward of the offlap (depositional shoreline) break
