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Geology Colloquium
Dr. Ellen HermanBucknell University
Interpreting Flow and Sediment Transport in Karst Springs
Thursday March 1stTalk at 4, refreshments at 345 PM
310 White Hall
Hollows, Wind Gaps, Water Gaps, and Ancient Rivers
GEO 321 Lecture 15
Armoring of HollowsArmoring of Hollows
Topographic InversionW-Shaped HollowsGully Gravure ( Bryan, 1940)
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Dip
Slop
eScar
p Sl
ope
Asym
met
rical
Hog
back
(Hom
oclin
alRi
dge)
Sym
met
rical
Hog
back
Antic
line
Axis
Appr
ox.
WV Rt28/55
North Fork Mtn., N of Seneca Rocks, WV
Area on Next Slide
Spur or “Nose”
Hillslope “Hollow” Boulder Source: Tuscarora SS
“Cliffs”
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Bouldery Hollow
Boulder-Free Nose
Bouldery Hollow Bouldery Hollow
Boulder-Free Nose
Gully Gravure, North Carolina
Image from Bryan, Kirk, 1940, Gully Gravure –– A Method of Slope Retreat: Journal of Geomorphology, v. III, no. 2, p. 89-107.
Gully Gravure, North Carolina
Modified from Bryan, Kirk, 1940, Gully Gravure –– A Method of Slope Retreat: Journal of Geomorphology, v. III, no. 2, p. 89-107.
Z’ Z
Paleo-topography
“W”-Shaped Channel
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Modified from Bryan, Kirk, 1940, Gully Gravure –– A Method of Slope Retreat: Journal of Geomorphology, v. III, no. 2, p. 89-107.
Topographic InversionGully Gravure, North Carolina
Valley Type ClassificationThornbury, 1969
• Antecedent (Predates Structures)• Superposed (Super-imposed)• Consequent (Flows Down Bedding Dip)
–vs. Obsequent (Flows Opposite Dip)• Subsequent (Eroded into Weak Rocks)
New River: 2nd Oldest River in the World???
photo by John Remo
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New River: 2nd Oldest River in the World?
River had to be in place before folding of
resistant rocks that now form ridges
Logic behind the statement: New River, unlike other rivers, cuts almost completely through the structures (Faults, folds, etc.) of the Appalachian Mountains, and therefore it must been in that route before the mountains formed, over 200 million years ago!
River maintained path throughout
uplift!
• Antecedent• Superposed• Consequent• Obsequent• Subsequent
New River: 2nd Oldest River in the World?
Alternative 1:River formed on
old Tertiaryerosion surface
(shown in A), then landscape was
rejuvenated & River was superimposed on folded Appalachians.
Alternative 2: River was
superimposed in segments from
shale- or limestone-dominated valleys.
• Antecedent • Superposed• Consequent• Obsequent• Subsequent
Live Anticline, Breached by Water Gap
Live Folds -Consequent Drainage
Short, N. M., and Blair, R. W., 1986, Geomorphology from Space, NASA daac.gsfc.nasa.gov/DAAC_DOCS/geomorphology/
GEO_2/GEO_PLATE_T-42.HTML
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Homoclinal Ridges, near Rawlings, Wyoming
Short, N. M., and Blair, R. W., 1986, Geomorphology from Space, NASA daac.gsfc.nasa.gov/DAAC_DOCS/geomorphology/
Obsequent(Flows Opposite
Dip)
CR
CV
WT BR
HFIMNF
Antecedent (Predates Structures)Superposed (Super-imposed)Consequent (Flows Down Bedding Dip)
vs. Obsequent (Flows Opposite Dip)Subsequent (Eroded into Weak Rocks)
Seven Bends of the North Fork Shenandoah River
Woodstock, VA •Subsequent
•Eroded into Weak Rocks (Martinsburg Shale)
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Seven Bends, North Fork Shenandoah River, near Woodstock, VA
Subsequent Eroded in Weak
Martinsburg Shale
Seven Bends of the North Fork Shenandoah River
Woodstock, VA •Subsequent
•Eroded into Weak Rocks (Martinsburg Shale)
Passage Ck.Fort Valley, VA
Subs
eque
nt ,
Erod
ed in
Wea
k D
evon
ian
Shal
e
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Compton Gap, Blue Ridge Mtns., Shenandoah N.P.
Wind Gap: Consequent or Old Water Gap Surrounded by Peneplains?
Look at Topo Map near Woodstock Fire Tower
http://terraserver.microsoft.com/
Search for Strasburg, VALook at bends of Shenandoah R.Subsequent Streams, Water Gaps in
Massanutten Mtn. & Fort ValleyWind Gaps in Blue Ridge of VA
e.g. Compton Gap, Jenkins GapHarpers Ferry, WV
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CR
CV
WT BR
HFIMNF
Look at Topo Map
http://terraserver.microsoft.com/
Looked at Erosional terraces on Greenbrier River north of Ronceverte, WV
Depositional Terraces on the Ohio River near Chester and Arroyo, WV
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Dolls Gap, West Virginia• From
http://www.wvexp.com/index.php/Dolls_Gap•
Doll's Gap, or Dolls Gap, forms the famous "saddle" of Gap Mountain in West Virginia's eastern panhandle. A "wind gap," the formation was established long ago by a stream which once crossed the mountain; after years of uplifting, the stream abandoned the pass across the mountains.
Gaps in N Fork Mountain
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12
CR
CV
WT BR
HFIMNF
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LANDSAT Image Courtesy Tim Warner & Duane NellisWVU Remote Sensing Lab
Geologic Overview of Canaan Valleya Billion Years of the Past and 10
Million Years into the Future
J. Steven KiteRobert E. Behling
WVU Geology & Geography
GeologicalMap of Canaan Valley
Cardwell, & others, 1968,
Geologic Map of West
Virginia: WVGES
Source: Kozar, Mark D., 1996, Geohydrology and Ground-Water Quality of Southern Canaan Valley, Tucker County, West Virginia, USGS Water Resources Investigations Report 96-4103, 67 p.
Generalized Cross-Section of the Bedrock Geology Along the Breached Blackwater Anticline, Canaan Valley
PRICE FORMATION
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Source: Kozar, Mark D., 1996, Geohydrology and Ground-Water Quality of Southern Canaan Valley, Tucker County, West Virginia, USGS Water Resources Investigations Report 96-4103, 67 p.
Generalized Cross-Section of the Bedrock Geology Along the Breached Blackwater Anticline, Canaan Valley
Hin
ge
Blackwater Ridge: ~ 10 million Years Ago?
PRICE FORMATION
Geology of
Canaan Valley
Streams Drain
Parallelto Valley
Chestnut Ridge: Analog to “Canaan” Area ~ 10 million Years Ago
Streams Drain Off Ridge Flanks
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Wind Gaps: Relicts of Drainage on Blackwater Ridge?
Blackwater R.
Possible Paleo-Drainage Routes: ~ 10 million Years Ago?
Blackwater River Piracy of Streams Flowing Off Old
Blackwater Ridge
Paleo-Drainage Routes: ~ 10 million Years Ago?
Dry Creek Piracy of
Blackwater Drainage
Blackwater River Piracy of Streams Flowing Off Old
Blackwater Ridge
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Southern Canaan Valley Will Be
Lost to Dry Fork Piracy
Northern Canaan Valley Will Grown as Ridges Retreat
Speculation on the Next 10,000,000
Years in “Canaan Valley”
Risi
ng R
idge
of
Pric
e Sa
ndst
one
Cortl
and
Valle
y
Glad
e Cr
eek
Valle
y
Risi
ng R
idge
of
Pric
e Sa
ndst
one
Cortl
and
Valle
y
Glad
e Cr
eek
Valle
y
May Be Lost to Dry Fork?
Risi
ng R
idge
of
Pric
e Sa
ndst
one
Cortl
and
Valle
y
Glad
e Cr
eek
Valle
y
Geology Colloquium
Dr. Ellen HermanBucknell University
Interpreting Flow and Sediment Transport in Karst Springs
Thursday March 1stTalk at 4, refreshments at 345 PM
310 White Hall
Paleohydrology & Paleoflood Hydrology
•See 2001 Lecture for more slides
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Prediction from Geomorphology & Holocene Stratigraphy
DepositsSlackwater: StageBedload: Tractive Force, Stream Power
PaleosolsInterruption of Stability
LandformsSlackwater Terraces
Tool Kits for the Paleohydrologist
• Vegetation Along Stream • Proxy Records, e.g. Tree Rings• Bedload Competence• Channel Geometry: Plan and Cross-
Section• Slackwater Deposits: Bath-Tub Rings
BedrockAlluvium
FloodplainFloodplainT1T1
T2T2
Channel ShelfDepositional Bar
TERRACE ASSEMBLAGE(oak, sassafras, dogwood,
mt. Laurel, white ash)
FLOODPLAIN FOREST(hackberry, black walnutamerican elm, sycamore)
RIPARIAN SHRUBS(alder, slippery elm,
box elder, red willow)
DEPOSITIONAL BAR(herbaceous vegetation;
willow, sycamore, or cottonwood seedlings)
Eric N. Davis, 2000. Modified from Osterkamp and Hupp, 1984.
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Dendrohydrology
Datable Flood Scar
Tractive Load Size• How to determine what moved.
– flake scars bruises on sheltered surfaces, multiple impact marks, Fe staining (Cheat), imbricated w/ tires, plastics, lumber, etc., aerial photography (BFR)
tau = τ = γ D Sγ = gamma = specific weight of waterD = depthS = gradient (slope)
Critical Tractive Force = tauc = τc = 166 d
d = grain diameter (mm)
Critical Tractive Force: Force Required to Move Particle of diameter = d
Remember?
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D = 0.0001 A1.21 S-0.57 (Knox, 1987)V = 0.065 d0.5 (Williams, 1983)Vc = 0.18 d0.44 (Koster, 1978)Vc = 0.18 d0.49 (Costa, 1983)Q1.5 =0.011 Lm
1.54 (Williams, 1983)λm = 166 Qm
0.46 (Carlston, 1965)τ = 0.030 d1.49 (Williams, 1983)
τ = 0.17 d (Williams, 1983)
ω = 0.079 d1.29 (Williams, 1983)
Symbols (Williams,
1984)
A = intermediate axis of largest clasts, mmd = particle diameter, mmD = competent flow depth, mλm = meander wavelength, mQ1.5 = discharge of 1.5 yr flood, m3/sQm = mean annual discharge, m3/s S = energy slope (approx. = topo. gradient), m/mV = mean flow velocity, m/sVc = threshold (critical) flow velocity, m/s
τc = threshold (critical) tractive force, N/m
τ = bed shear stress, N/mω = stream power/m of width, watts/m2
Floods & Quaternary Stratigraphy
Arid Streams (Most Sensitive: Most Studied)“Pluvials” Wet Episodes (≈ “Glacials”)Vegetation Cover Critical
Holocene Arroyo-Cutting and FillingUnder Drought:Hyper-Arid: Loss of Channel VegetationPromotes Erosion of Channel
Semi-Arid: Loss of Slope VegetationPromotes Erosion of Slopes + Filling of Channels
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http://geochange.er.usgs.gov/sw/impacts/geology/arroyos/
The Arroyo Problem in the Southwestern
United States
Brandon J. VogtU.S. Geological Survey
Tucson 1940
Note Rock
Tucson 1982
Note Rock
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Tucson 1940, 1982 Images From Landscape Changes in the Southwestern United States: Techniques, Long-term Data Sets, and Trendsby Craig D. Allen, Julio L. Betancourt, & Thomas W. SwetnaminSisk, T.D., editor. 1998. Perspectives on the land use history of North America: a context for understanding our changing environment. U.S. Geological Survey, Biological Resources Division, Biological Science Report USGS/BRD/BSR 1998-0003 (Revised September 1999). 104 p.
http://biology.usgs.gov/luhna/chap9.html
Precipitation Style & Floods
Convectional Thunderstorms: Favored by Hot Air Masses (Drought?)
Hurricanes: Favored by Warm SST & ITC North of Equator. Requirements Not Met in No. Hemisphere During “Glacials”
Frontal Precip: Driven By Energy of System (Increases w/ Warmer Oceans), But Circulation Pattern Is Locally More Important
Snow-Melt: Favored by Longer Winters, but Not If It Gets Too Cold (= Too Dry)
Floods & Quaternary Stratigraphy in Eastern USConvectional Thunderstorms: Favor Debris
Flows, Erosion of Gullies & Small Channels; Inefficient Middle to Large Streams
Hurricanes: Favor Debris Flows, Efficient Sed Transport on Small to Middle Streams
Frontal Precip: Efficient Sed Transport in Middle to Large Streams. Low Rainfall Intensity Limits Sediment Delivery by Small Streams
Snow-Melt: Freeze-Thaw Produces Lots of Sediment on Slopes, Inefficient Transport by Small Streams, Erosion by Large Rivers
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Quaternary Fluvial Stratigraphy in Eastern US
Complicated by Base-Level Fluctuations
Sea-Level Changes (Drop w/ Glaciation) e.g. Unglaciated Potomac, James basins
Local Basel Level (Rise w/ Outwash Aggradation) e.g. Glaciated Ohio, Allegheny River & Tribs
Quaternary Fluvial Stratigraphy in Eastern US
Where & When Are Base-Level Fluctuations More Important Than Climate-Driven Sediment Supply?
Unglaciated Rivers in Ohio River Basin (Kanawha, Mon, etc.):Ohio River Outwash Aggradation vs. Upland Sediment Flux (Local Slopes + Tribs)