Fluvial Stratigraphy

A Webinar in the AAPG Education Seriesby

John HolbrookUniversity of Texas at Arlington

GoalProvide some take-aways extracted from a more extensive course.

Longitudinal Profile

River-to-Basin Processes

(Van Wagoner, et al., 1991)

Upstream Controls(e.g., Sed supply, discharge, uplift, etc.)

Downstream Controls (e.g., Sea Level, etc.)

Fluvial and Valley-Fill

Strata

Fluvial Response to Base Level Change

Sea Level

Sea Level Fall

Fluvial Incision

Sea Level Rise

Fluvial Aggradation

Slow

Fast

Progressive Stacking in Sheets?

Upstream Controls?

Complex Reincision?

Fluvial Stratigraphy ComponentsGeomorphology of Fluvial SystemsFluvial FaciesArchitectural HierarchiesSeismic GeomorphologyHeterogeneity and ConnectivityControls on Fluvial StratigraphyCorrelation of Fluvial Strata

Geomorphology of Fluvial SystemsRiver Patterns

anastomosedsinglesinuouschannels

anastomosedbraidedchannels

barassemblage

braidedchannel

Single sinuouschannels

Rakaia River, New Zealand

Madison River, USA

(Bridge & Tye ,2000)(Posamentier and Walker, 2006)

River PatternsHigh Width:Depth

Low Width:Depth

Fluvial Facies

(Posamentier and Walker, 2006)

(Galloway and Hobday, 1983)

cordoba_river_channel_iahmedialibrary.net

Mud Flat

Levee

Point Bar

Overbank fine

Mississippi River “blue muds”

(Holbrook, et al. 2006)

Roman Boat in Old Rhine

Mississippi River bar top

K Dakota Channel fills

Mo River Point Bar with Drape

Peat Core, Rhine Delta Fluvial Environments

Mississippi RiverSplay sand sheet

Fluvial Facies(Cheat Sheet)

Still Waters(Clay, Silty Clay, Peat)

Lazy River(Loams and Heterogeneous )

Swift Current(Sand and Loamy Sand)

BioturbatedNon-

Bioturbated BioturbatedNon-

Bioturbated BioturbatedNon-

Bioturbated

Mud Flat

Levee

Point Bar

Overbank fine

Floodplain Mud Flat Lake Levee/Splay

Active Channel

Splay Channel and Lobe Point Bar and

Thalweg Fill

Bridge and Diemer (1983)

(Holbrook, 2001)

http://www.geol.binghamton.edu/faculty/bridge/R&Pcomputersim.htm

Depositional Units (John Bridge)

Bounding Surfaces (Andrew Miall)

Architectural Hierarchies

Storey

Storey

Erosion SurfaceBedset

Bedset

Channel

Seismic Geomorphology

Fluvial Hierarchies in Seismic Geomorphology

Darmadi et al, 2007

Heterogeneity and Connectivity

(Larue 2006)

(Jordan and Pryor, 1992)

http://www.geol.binghamton.edu/faculty/bridge/R&Pcomputersim.htm

John Bridge

(Bridge and Tye, 2000)

http://en.wikipedia.org/wiki/Oil_platform

Channel Belts as Target Units(Gibling, 2006)

Odds of Hitting Sandy Channel Belt = VariableOdds of Hitting Full Section of Bar Sand within Belt =

3 in 5

http://en.wikipedia.org/wiki/Oil_platform

Channel Area=40%Bar Area = 60%

http://en.wikipedia.org/wiki/Oil_platform

Connections?

Trapped Product?

(Saucier, 1994)

(Jordan and Pryor, 1992)

Controls on Fluvial Stratigraphy

Sea Level

Sea Level Fall

Fluvial Incision

Sea Level Rise

Fluvial Aggradation

Slow

Fast

Longitudinal Profile

River-to-Basin Processes

(Van Wagoner, et al., 1991)

Upstream Controls(e.g., Sed supply, discharge, uplift, etc.)

Downstream Controls (e.g., Sea Level, etc.)

Fluvial and Valley-Fill

Strata

Assumption: Base level, and the related longitudinal profile, is the primary control on aggradation in both upstream and downstream settings.

Downstream vs. Upstream Base Level Controls

Downstream Controls Upstream Controls

Assumption: Base level, and the related longitudinal profile, is the primary control on aggradation in both upstream and downstream settings.

Downstream vs. Upstream Base Level ControlsDownstream Controls

Eustatic (sea level/lake level), morphologic (e.g., tributary junctures), tectonic (e.g., faults)

Upstream ControlsClimate (e.g., sediment supply, discharge), tectonic (e.g., uplift rate)

Assumption: Base level, and the related longitudinal profile, is the primary control on aggradation in both upstream and downstream settings.

Downstream vs. Upstream Base Level ControlsDownstream Controls

Eustatic (sea level/lake level), morphologic (e.g., tributary junctures), tectonic (e.g., faults)

Local effects to lower reaches causing adjustments that propagate and dampen upstream

Upstream ControlsClimate (e.g., sediment supply, discharge), tectonic (e.g., uplift rate)

Broad effects in upstream reaches causing adjustments that propagate and dampen downstream

Assumption: Base level, and the related longitudinal profile, is the primary control on aggradation in both upstream and downstream settings.

Downstream vs. Upstream Base Level ControlsDownstream Controls

Eustatic (sea level/lake level), morphologic (e.g., tributary junctures), tectonic (e.g., faults)

Local effects to lower reaches causing adjustments that propagate and dampen upstream

Generally causes adjustments on the scale of 101 to 102 meters and 104 to 107 years

Upstream ControlsClimate (e.g., sediment supply, discharge), tectonic (e.g., uplift rate)

Broad effects in upstream reaches causing adjustments that propagate and dampen downstream

Generally causes adjustments on the scale of 100 to 101 meters and 101 to 104 years

E.G.,δyb/δt=-Krqa[1+K1qsdc]Sk

(Howard et al., 1994)

The “Graded” Longitudinal ProfileProfile variable because of non-constant upstream controls:

Water Discharge (Qw)Sediment Flux (Qs)

Substrate ErodabilityUplift Rate

Local TectonicsEtc.

River Profile

Anchor pointDownstream base-level control

(e.g., sea level)

?!(Blum et al., 1994)

2500 BP to Modern

Channel TerraceFloodplain

Alluvial Sequences on Colorado River, Central Texas

Sea Level

Base Level Buffers and Buttresses

Determiners of “Graded” Profile ElevationSediment Influx/Transport Capacity =1 (eq. 1)

dz/dt + dqs/dx = 0 (eq. 2)Where:

qs = Sediment Discharge= f(ω, substrate erodability)Sediment Influx = qs delivered at xi = f (drainage basin)

Transport Capacity = qs that can be transported at xi

dz/dt = 0

Variablesz Profile elevationx Stream distancet Timeω=γQwSω Stream Powerγ Specific WeightQw Water DischargeS Slope

Buttress(Sea Level, Cataract,

Lake Level, etc.)

Preservation Space

Lower Buffer ProfileTransport Capacity = MaxSediment Influx = MinUplift Rate = Min

Buffer ZoneInstantaneous

Profile

Upper Buffer ProfileTransport Capacity = MinSediment Influx = MaxUplift Rate = Max

Buffersf(Qw)

Some Effects of Buttress Shift

Down-Profile Buttress Shift

Buttress Rise

Buttress Fall

Σ

Σ

Σ

Unit Thickness=

Unit Thickness=

Unit Thickness=

Correlation of Fluvial Strata

Fluvial-on-Fluvial SB’sSequence Boundaries vs. Settings (Alluvial)

v1 v2 v3 v4

Mesa Rica

(Wellner and Bartek, 2003)

Sequence boundaries as time surfaces?

LST

HST

TST

FSST

(Strong and Paola, 2008)

Sequence boundary formed over 75% of the entire sea level

cycle!!!

Composite Surface

Sequence Boundaries as Topographic Surfaces?

Sequence Boundary

(Holbrook, 1996)

Sequence Boundaries as Unconformities?

(Strong and Paola, 2008)

Fluvial T2

Marine T2

T2 Sequence Boundary

Fluvial T2

T2 Sequence BoundaryMarine T3

See you in December!

Q&Awith

John HolbrookUniversity of Texas at Arlington

AAPG Education Series Courses and Resourcesavailable at

www.aapg.org/education