Geology Colloquium Dr. Ellen Herman Bucknell University Interpreting Flow and Sediment Transport in Karst Springs Thursday March 1st Talk at 4, refreshments at 345 PM 310 White Hall Hollows, Wind Gaps, Water Gaps, and Ancient Rivers GEO 321 Lecture 15 Armoring of Hollows Topographic Inversion W-Shaped Hollows Gully Gravure ( Bryan, 1940) 1 WV Rt 28/55 Symmetrical Hogback Anticline Axis Approx. Scarp Slope Asymmetrical Hogback (Homoclinal Ridge) N of Seneca Rocks, WV North Fork Mtn., Dip Slope Area on Next Slide S p u H r i o l l r s l “ o N p o e s “H e ” o l l ow ” Boulder Source: Tuscarora SS “Cliffs” 2 Bouldery Hollow Boulder-Free Nose low ery Hol Bould Nose r-Free Boulde Bouldery Hollow 3 Gully Gravure, North Carolina Bryan, Kirk, 1940, Gully Gravure –– A Method of Z Paleo- Image from topography Slope Retreat: Journal of Geomorphology, v. III, no. 2, p. 89-107. “W”-ShapedChannel Gully Gravure, North Carolina Z’ Bryan, Kirk, 1940, Gully Gravure –– A Method of Modified from Slope Retreat: Journal of Geomorphology, v. III, no. 2, p. 89-107. Topographic Inversion 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. Valley Type Classification Thornbury, 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 4 New River: 2nd Oldest River in the World? 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! • Antecedent River maintained • Superposed path throughout • Consequent uplift! • Obsequent • Subsequent River had to be in place before folding of resistant rocks that now form ridges Alternative 1: River formed on old Tertiary erosion surface (shown in A), then landscape was rejuvenated & River was superimposed on folded Appalachians. • Antecedent New River: • Superposed 2nd Oldest • Consequent River in the • Obsequent World? • Subsequent Alternative 2: River was superimposed in segments from shale- or limestone- dominated valleys. 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 5 Homoclinal Ridges, near Rawlings, Wyoming Obsequent (Flows Opposite Dip) Short, N. M., and Blair, R. W., 1986, Geomorphology from Space, NASA daac.gsfc.nasa.gov/DAAC_DOCS/geomorphology/ Antecedent (Predates Structures) Superposed (Super-imposed) Consequent (Flows Down Bedding Dip) vs. Obsequent (Flows Opposite Dip) Subsequent (Eroded into Weak Rocks) CR HF NF IM CV WT BR Seven Bends of the North Fork Shenandoah River Woodstock, VA •Subsequent •Eroded into Weak Rocks (Martinsburg Shale) 6 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 Subsequent , Eroded in Weak Devonian Shale Devonian in Weak Eroded Subsequent , 7 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, VA Look at bends of Shenandoah R. Subsequent Streams, Water Gaps in Massanutten Mtn. & Fort Valley Wind Gaps in Blue Ridge of VA e.g. Compton Gap, Jenkins Gap Harpers Ferry, WV 8 CR HF NF IM CV WT BR 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 9 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 10 11 CR HF NF IM CV WT BR 12 Geologic Overview of Canaan Valley a Billion Years of the Past and 10 Million Years into the Future J. Steven Kite Robert E. Behling WVU Geology & Geography LANDSAT Image Courtesy Tim Warner & Duane Nellis WVU Remote Sensing Lab Geological Map of Canaan Valley Cardwell, & others, 1968, Geologic Map of West Virginia: WVGES Generalized Cross- Section of the Bedrock Source: Kozar, Mark D., 1996, Geohydrology and Ground-Water Geology Along the Quality of Southern Canaan Valley, Breached Blackwater Tucker County, West Virginia, USGS Anticline, Canaan Valley Water Resources Investigations Report 96-4103, 67 p. PRICE FORMATION 13 Blackwater Ridge: ~ 10 million Years Ago? e g n i H Generalized Cross- Section of the Bedrock Source: Kozar, Mark D., 1996, Geohydrology and Ground-Water Geology Along the Quality of Southern Canaan Valley, Breached Blackwater Tucker County, West Virginia, USGS Anticline, Canaan Valley Water Resources Investigations Report 96-4103, 67 p. PRICE FORMATION Geology of Canaan Valley Streams Drain Parallel to Valley Chestnut Ridge: Analog to “Canaan” Area ~ 10 million Years Ago Streams Drain Off Ridge Flanks 14 Wind Gaps: Relicts of Drainage on Blackwater Ridge? Blac kw at er 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? Blackwater River Piracy of Streams Flowing Off Old Blackwater Ridge Dry Creek Piracy of Blackwater Drainage 15 Speculation on the YearsNext in “Canaan 10,000,000 Valley” Southern Canaan Lost toValley Dry Fork Will Be Geology Colloquium Canaan Valley Will Grown asNorthern Cortland Valley Ridges Retreat Interpreting Flow and Sediment Piracy Rising Ridge of Price Sandstone Dr. Ellen Herman Transport in KarstBucknell Springs University Glade Creek Valley Talk at 4, refreshments at 345 PM May Be Lost to Dry Fork? Thursday March 1st 310 White Hall Paleoflood Hydrology Paleohydrology & •See 2001 Lecture for more slides 16 Prediction from Geomorphology & Holocene Stratigraphy Deposits Slackwater: Stage Bedload: Tractive Force, Stream Power Paleosols Interruption of Stability Landforms Slackwater 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 RIPARIAN SHRUBS (alder, slippery elm, TERRACE ASSEMBLAGE box elder, red willow) (oak, sassafras, dogwood, mt. Laurel, white ash) FLOODPLAIN FOREST DEPOSITIONAL BAR (hackberry, black walnut (herbaceous vegetation; american elm, sycamore) willow, sycamore, or cottonwood seedlings) T2 T2 T1 T1 Floodplain Floodplain Alluvium Bedrock Depositional Bar Channel Shelf Eric N. Davis, 2000. Modified from Osterkamp and Hupp, 1984. 17 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) r? be tau = τ = γ D S em em R γ = gamma = specific weight of water D = depth S = gradient (slope) Critical Tractive Force = tauc = τc = 166 d d = grain diameter (mm) Critical Tractive Force: Force Required to Move Particle of diameter = d 18 D = 0.0001 A1.21 S-0.57 (Knox, 1987) V = 0.065 d0.5 (Williams, 1983) 0.44 Vc = 0.18 d (Koster, 1978) 0.49 Vc = 0.18 d (Costa, 1983) 1.54 Q1.5 =0.011 Lm (Williams, 1983) 0.46 λm = 166 Qm (Carlston, 1965) τ = 0.030 d1.49 (Williams, 1983) τ = 0.17 d (Williams, 1983) ω = 0.079 d1.29 (Williams, 1983) A = intermediate axis of largest clasts, mm d = particle diameter, mm D = competent flow depth, m Symbols λm = meander wavelength, m (Williams, 3 1984) Q1.5 = discharge of 1.5 yr flood, m /s 3 Qm = mean annual discharge, m /s S = energy slope (approx. = topo. gradient), m/m V = mean flow velocity, m/s Vc = threshold (critical) flow velocity, m/s τc = threshold (critical) tractive force, N/m τ = bed shear stress, N/m ω = 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 Filling Under Drought: Hyper-Arid: Loss of Channel Vegetation Promotes Erosion of Channel Semi-Arid: Loss of Slope Vegetation Promotes Erosion of Slopes + Filling of Channels 19 The Arroyo Problem in the Southwestern United States Brandon J. Vogt U.S. Geological Survey http://geochange.er.usgs.gov/ sw/impacts/geology/arroyos/ Tucson 1940 Note Rock Tucson 1982 Note Rock 20 Tucson 1940, 1982 Images From Landscape Changes in the Southwestern United States: Techniques, Long-term Data Sets, and Trends by Craig D. Allen, Julio L. Betancourt, & Thomas W. Swetnam in Sisk, 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 US Convectional 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.