Evolution of valley depth and width Evolution of valley depth and - - PowerPoint PPT Presentation

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Mar 20, 2024 336 likes •497 views

Evolution of valley depth and width Evolution of valley depth and width Evolution of valley depth and width Evolution of valley depth and width during base- -level fluctuations level fluctuations during base during base- -level fluctuations

SLIDE 1

Evolution of valley depth and width Evolution of valley depth and width during base during base-

level fluctuations

level fluctuations

Nikki Strong, Ben Sheets, Michael Nikki Strong, Ben Sheets, Michael Kelberer Kelberer, , Wonsuck Wonsuck Kim, Chris Paola Kim, Chris Paola

Evolution of valley depth and width Evolution of valley depth and width during base during base-

level fluctuations

level fluctuations

Nikki Strong, Ben Sheets, Michael Nikki Strong, Ben Sheets, Michael Kelberer Kelberer, , Wonsuck Wonsuck Kim, Chris Paola Kim, Chris Paola

St. Anthony Falls Laboratory
St. Anthony Falls Laboratory

National Center for Earth surface Dynamics National Center for Earth surface Dynamics Department of Geology and Geophysics Department of Geology and Geophysics University of Minnesota University of Minnesota

SLIDE 2

1 1 Experimental Set Experimental Set-

up 2 2 Experimental parameters Experimental parameters 3 3 General observations General observations 4 4 Temporal and spatial valley evolution Temporal and spatial valley evolution 5 5 Conclusions Conclusions

SLIDE 3

Experimental set Experimental set-

up

Plan view Plan view

~ 3 m ~ 3 m ~ 5 m ~ 5 m

flow flow

SLIDE 4

flow flow

Subsidence Subsidence

SLIDE 5

pressurized water reservoir to water supply solenoid valve stainless steel cone to gravel recycling transport surface gravel basement rubber membrane experimental deposit

“ “Jurassic Tank Jurassic Tank ” ” Mechanics Mechanics

SLIDE 6

Basin Elevation Basin Elevation Data Data

topography topography laser laser sonar sonar

SLIDE 7

100 200 300

Rapid Superimposed Slow time (hrs) time (hrs) Base level (mm) Base level (mm)

SLIDE 8

Basin topography Basin topography

beginning beginning

f cycle
f cycle

valley valley end of base end of base level fall level fall end of base end of base level rise level rise

Slow cycle Slow cycle Rapid cycle Rapid cycle

SLIDE 9

Basin Basin Isopachs Isopachs

Slow cycle Slow cycle Rapid cycle Rapid cycle

fall fall rise rise

flow flow

(mm) 200

SLIDE 10

100 200 300

Rapid Superimposed Slow time (hrs) time (hrs) Base level (mm) Base level (mm)

SLIDE 11

incised valley versus autogenic incision

maximum elevation Minimum elevation Channel depth

Quantitative definition of an incised valley

Max elev – min elev > 2 channel depth

SLIDE 12

Evolution of valley width with time Evolution of valley width with time

SLIDE 13

Synoptic Synoptic vs vs stratigraphic stratigraphic valley depth valley depth

0 1000 2000 3000

elevation (mm)

Synoptic high Synoptic low Stratigraphic low

x (mm)

Synoptic valley depth Stratigraphic valley depth

SLIDE 14

Conclusions

1. Valley formation during rapid cycle only
2. Autogenic incision interacted with the externally imposed base-level

change to produce multiple discrete down-cutting episodes, despite continuous base-level fall.

3. During the rapid cycle, downstream deposition during the fall helped

widen the valley downstream, producing a tapered planform comparable to that found in many natural estuaries.

4. During the rapid cycle base level rise produced continued

valley widening.

5. Synoptic valley depth decreased downstream due to deposition;

stratigraphic valley depth increased downstream