Down-stream process transition (f (q ) = 1) · 2020-01-29 · 2) Acr 10-2 103 4 5 Detachment...

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2) A cr 10 -2 10 3 10 4 10 5 Detachment Limited Equilibrium Slope S d = k sd A -d S t = k st A -t Slope Detachment Limited S d >> S t S d << S t Stochastic Down-stream process transition (f (q s ) = 1) 10 6 10 7 10 8 10 -1 Channel Gradient (m/m) { Drainage Area (m Transport Limited Equilibrium Transport Limited Variation

Transcript of Down-stream process transition (f (q ) = 1) · 2020-01-29 · 2) Acr 10-2 103 4 5 Detachment...

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2)

Acr

10-2

103 104 105

Detachment Limited Equilibrium Slope

Sd = ksd A-�d

St = kst A-�t Slope

Detachment Limited Sd >> St

Sd << St Stochastic

Down-stream process transition (f (qs) = 1)

106 107 108

10-1

Cha

nnel

Gra

dien

t (m

/m) {

Drainage Area (m

Transport Limited Equilibrium

Transport Limited

Variation

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Mixed Bedrock-Alluvial Stream (Appalachians, VA)

Concavity Index indistinguishable from detachment-limited bedrock channels

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Available data suggests DL and TL streams have similar concavities

θ = .69

θ = .49

θ = .42

Courtesy of The Geological Society of America. Used with permission.

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King Range Trunk Streams

No Change in Form, Double Steepness

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Tributary Response: Kinematic Wave

U2/U1 ~ 8; Why ks2/ks1 ~ 2?

Sediment Armor in Low Uplift Zone?

Threshold Stress for Erosion?

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Page 11: Down-stream process transition (f (q ) = 1) · 2020-01-29 · 2) Acr 10-2 103 4 5 Detachment Limited Equilibrium Slope Sd = ksd A- d St = kst A- t Slope Detachment Limited Sd >>
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Tectonic Geomorphology

• Intermediate Timescale Patterns and Rates of Deformation

• Bridge between Geodetic and Geologic • 1e3 – 1e6 years • Spatial and Temporal Resolution

• Paleoseismicity / Tsunami Records • Interaction of Climate and Tectonics

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Intermediate Timescale Deformation

Approaches

• Static Landforms as Strain Gauges• Terraces (fill/strath, fans, marine platforms, coral reefs,

moraines, etc)

• Dynamic Topography – Invert for Rock Uplift• Bedrock and Alluvial Channel Networks • Colluvial Channels • Hillslopes • Glacial Cirques and Valleys

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Intermediate Timescale Deformation

Problems

• Local/Regional Patterns and Rates of Rock Uplift• Fault Behavior and Slip Rates

– Kinematics and temporal evolution

• Interaction of Structures – Linkage, rupture across segment boundaries

• Off-Fault Deformation and Distributed Strain • Slip Rates and Paleoseismicity of Blind Thrusts • Role of Lower Crustal and/or Mantle Flow

– Little / no record in upper crustal structures

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Interaction of Climate and Tectonics Problems

• Does Erosion Dictate Rock Uplift Rate / Pattern?

• Nature and Strength of Feedbacks – Uplift – Topography – Climate – Erosion - Uplift

• Do Details of the Erosion Mechanism Matter? – Bedrock Channels; Sediment flux; Debris Flows; Glaciers

• Steady State Orogens – Plausible? Probable? Time to Steady State?

• Impact of Late Cenozoic Climate Change • Controls on Topographic Relief

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Research NeedsErosion Processes and Climate Linkages

• Bedrock Channel Erosion Laws (role lithology, sediment flux, sediment size, debris flows, storms)

• Glacial Erosion Mechanics (glacier flux, ice dynamics, hydrology)

• Landslide Initiation and Inventory (storms, seismic acceleration)

• Extreme Events and Orography (storms, glacier outburst floods, landslide dam-bream floods)

• Controls on River and Terrace Gradient (climate vs. tectonics; channel width)

• Chemical and Physical Weathering Relationship

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Research NeedsChronology

• Cosmogenic Isotope Methodologies » Inheritance, Production Rates, Multiple Systems

• In-Situ / Detrital Thermochronology

• U-Th/He Dating of Young Volcanics

• Relief Evolution » Topography, Denudation Rate, Isotherm Structure and their

Temporal Evolution » Near Surface Thermal Advection

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Tectonic GeomorphologyData Needs

• Development of Chronometers and Centers for Analyses, Digital Compilation/Distribution of Data

• Affordable High-Resolution Satellite Data (ASTER, INSAR)

• High-Resolution DEMs (LIDAR, SRTM, ASTER)• Digital Geologic Maps • Dense Arrays Climate Data (Orography) • Digital Mapping Technologies (e.g., PDA, Laser Range

Finder, GPS Total Station) • GPR – Shallow Structures

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Himalaya Foreland, Nepal Siwalik Hills Anticline

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Modeled Erosion Rates

Courtesy of The Geological Society of America. Used with permission.

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Modeled Erosion Rates

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Sediment Flux Lag Complicates Landscape Response –Transient Shifts from Sediment Covered to Tool Starved Likely

SC

Mix

TS

SC – Sediment Covered TS – Tool starved

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Sediment-flux Models: Required Low-Uplift Zone Conditions for ks2/ks1 = 2

Tool Starved

Sediment Covered

Peak Efficiency

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Generalized Stream-Power Incision Model

Tool Starved

Sediment Covered

Qs > Qc Transport Limited

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2)

Log Gradient

Stream power

Linear decline, n=1

Linear decline, n=2

Beaumont

Parabolic, n=1

Parabolic, n=2

-2.5 -2 -1.5 -1 -0.5 0 5

6

7

8

9

�t = 0

Diagnostic steady-state morphology IF �t < �d

Log

Dra

inag

e Are

a (m

Page 30: Down-stream process transition (f (q ) = 1) · 2020-01-29 · 2) Acr 10-2 103 4 5 Detachment Limited Equilibrium Slope Sd = ksd A- d St = kst A- t Slope Detachment Limited Sd >>

Log Gradient

Stream power

Linear decline, n=1

Linear decline, n=2

Parabolic, n=1

Parabolic, n=2

5 -2.5 -2 -1.5 -1 -0.5 0

6

7

8

9

�t = 0.3

2)

Steady-state morphology non-diagnostic IF �t ~ �d

Log

Dra

inag

e Are

a (m

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Topographic Sensitivity to Uplift Rate Potentially Diagnostic

SC

TS

Mix

SC – Sediment Covered TS – Tool starved