DOCSLIB.ORG

Seasonal Reversal of Flood-Tide Dominant Sediment Transport in a Small Oregon Estuary

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Seasonal Reversal of Flood-Tide Dominant Sediment Transport in a Small Oregon Estuary Seasonal reversal of flood-tide dominant sediment transport in a small Oregon estuary SAM BOGGS, JR. Department of Geology, University of Oregon, Eugene, Oregon 97403 CHARLES A. JONES1 Department of Geology, Chadron State College, Chadron, Nebraska 69337 ABSTRACT bathymetry of the estuary was mapped, and salinity, temperature, and current velocity were measured. The Sixes River in southwestern Oregon has a summer discharge of only about 2 m3/sec. During these low-discharge conditions, a PHYSIOGRAPHY AND HYDROGRAPHY flood-dominated system of bottom tidal currents develops in the es- tuary and a deltalike sill, as much as 1.5 m in height, builds across The Sixes River (Fig. 1) is almost 50 km long. The average gra- the mouth of the estuary by upstream progradation. Flood-tide dient of the upper half of the stream is 9 m/km; of the lower half it currents move across this sill at velocities of as much as 90 cm/sec is 0.7 m/km. The estuary is about 3 km long (maximum incursion 15 cm above the bottom, but the velocity of ebb-tide currents usu- of salt water) and ranges in width from about 210 m at the lower ally does not exceed about 40 cm/sec. end to less than 45 m at the upper end (Fig. 2). The gradient within Dispersal patterns of dyed sediment injected at the river mouth the estuary is less than 0.1 m/km. The lowermost part of the es- during low river discharge show that flood-tide currents transport tuary, about 150 m in length, is a narrow channel approximately sand across the sill and up the estuary as far as 0.8 km (about one- 15 m wide. The position of this channel and the angle at which it fourth the length of the estuary) in a single flood-tide phase. During enters the sea shift with the seasons. In summer the channel is ebb tide, the sill impedes movement of salt water along the estuary commonly long and sinuous and empties toward the south. In bottom, producing a sharply stratified two-layer water system. Al- winter the channel is short and straight and is usually oriented per- though tracer experiments show that some fine sand is removed pendicularly to the coast line; however, heavy winds and seas in from the estuary during the ebb phase, primary sedimentary struc- late winter have been observed to displace it to the north. tures and the mineral composition of the sand indicate that Discharge changes significantly from summer to winter. Peak flood-tide dominance of the bottom tidal currents causes a net gain discharge commonly occurs following intense rainstorms from De- of marine sediment in the estuary while the sill is in place. cember to February, although occasional high discharge also oc- River discharge after winter storms may increase to more than curs in November and March. The lowest discharge is from July to 400 m3/sec, and large quantities of detritus, including gravel, are September. Monthly averages of mean daily discharge for the Sixes transported downstream into and through the estuary. High river River at Sixes, Oregon, for the period 1967 to 1970 range from a discharge also causes erosion of the sill, greatly reducing the low of 0.65 m3/sec to a high of almost 112 m3/sec (U.S. Geol. Survey sediment-trapping capacity of the estuary. The finer fluvial detritus, Water Resources Div., 1968, 1969, 1970). The gauging station is together with fine marine sediment deposited during the summer, is approximately 8 km upstream from the mouth of the estuary, and swept from the estuary, leaving it floored largely by gravel. Thus, the hydraulic sediment-trapping mechanisms observed in the es- tuary of the Sixes River appear to be effective only on a seasonal basis under present hydrologic conditions. Key words: sedimenta- tion, sediment transport, fluorescent tracers, bed forms, heavy min- erals, estuaries. INTRODUCTION The estuaries of the small high-gradient streams of southwestern Oregon are typically short, narrow, and shallow, and average stream discharge is low. However, the streams attain high velocities during periods of peak discharge in winter, and at such times they Figure 1. Index transport significant quantities of sand and gravel. In order to map showing loca- evaluate the pattern and magnitude of sediment transport in a tion of Sixes River es- tuary on the southern small estuary, we studied the estuary of the Sixes River. The river is Oregon coast. easily accessible, its hydrologic characteristics have not been exces- sively modified by man, and it is typical of the small coastal streams of southern Oregon and northern California. The study focused on the transport of marine sediment within the estuary and the ability of the estuary to trap and retain sedi- ment from both fluvial and marine sources. Sediment movement was investigated by use of fluorescent tracers (Teleki, 1966; Ingle, 1966; Crickmore, 1967; Kennedy and Kouba, 1970) and by study of sedimentary structures and heavy mineral assemblages. The 'Present address: Bendix Field Engineering Corp., First National Life Building, Suite 104, Austin, Texas 78701. Geological Society of America Bulletin, v. 87, p. 419-426, 13 figs., March 1976, Doc. no. 60311. 419 Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/87/3/419/3433754/i0016-7606-87-3-419.pdf by guest on 24 September 2021 420 BOGGS AND JONES Figure 2. Topographic map of the lower part of the Sixes River estuary (mapped with plane table and alidade). one tributary joins the river below the station; thus, discharge into several deep depressions, the floor of the estuary is 3.0 to 4.5 m the ocean is probably somewhat greater than indicated by these below sea level. Salt water flows upstream during high tide as far as figures. 3 km above the mouth of the estuary. Much of this water returns to The maximum tidal height in the vicinity of the Sixes River is 2.7 the sea as the tide ebbs; however, salt water remains in the depres- m in winter and 2.6 m in summer; minimum tidal height is —0.8 m sions and as a thin bottom layer in the lower part of the estuary (U.S. Dept. of Commerce, 1974). The tidal range is 1.3 to 3.6 m in behind the sill (Reimers, 1973). When the sill is eroded by high winter and 1.6 to 3.4 m in summer. Because of a sill as much as 1.5 river discharge in late autumn or winter, salt-water incursion is in- m in height that partly to totally blocks the mouth of the estuary in hibited, and the salt-water wedge extends only a very short distance summer, tidal fluctuations in the estuary upstream from the sill are into the estuary, except during periods when occasional low river usually less than 1.5 m (Reimers, 1973). Flood-tide velocities of discharge allows temporary invasion of salt water along the bot- almost 85 cm/sec were measured at 15 cm above the stream bed tom. When river discharge is high, the incoming salt water mixes during summer conditions. Ebb-tide velocities in summer com- rapidly with fresh water and is then expelled from the estuary dur- monly do not exceed about 40 cm/sec near the bed in the upper part ing the ebb-tide cycle. of the outflow channel, but winter velocities are much higher (may exceed 200 cm/sec at the water surface). FLUORESCENT TRACER ANALYSIS The sand sill mentioned above forms and persists only during summer when river discharge is low, prograding upstream in del- Summer Experiments talike fashion throughout the summer. During some periods of par- ticularly low river discharge and unusually high tides and high seas, Tracer Injection. Three fluorescent tracer experiments were the landward movement of sand into the outflow channel occurs so carried out during low discharge conditions of the river (summers rapidly that the sill grows into a bar that builds up several metres of 1969, 1971, 1974) to determine the distance of transport of above high-tide level and blocks the mouth of the estuary. Drainage sand-size sediment by flood-tide and ebb-tide currents. In the first of the estuary then takes place by seepage through the bar. With two experiments, approximately 150 to 200 kg of natural sand (30 rising river level in winter or increased discharge during autumn percent quartz, 65 percent other light minerals and rock fragments, freshets, the bar is eroded, and the sand is swept to sea. 5 percent heavy minerals and rock fragments) dyed green and 100 When the sill is in place, the Sixes estuary is stratified into a two- to 150 kg of a heavy sand concentrate (mainly magnetite) dyed layer system (type A estuary of Pritchard, 1955) during ebb tide. pink were used as tracers. Mean grain size of the natural sand was Reimers (1973) indicated that this interface is sharply defined by as much as 10°C difference in temperature and a 25°/oo difference in 1 A table of mean daily discharge for the Sixes River (Appendix Table 1) is available 1 salinity (Fig. 3, Table 1, and Appendix Table l ). Average water as supplementary material 76-6 from Documents Secretary, Geological Society of depth in the estuary during summer is less than 1.5 m; however, in America, 3300 Penrose Place, Boulder, Colorado 80301. Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/87/3/419/3433754/i0016-7606-87-3-419.pdf by guest on 24 September 2021 SEASONAL REVERSAL OF FLOOD-TIDE DOMINANT SEDIMENT TRANSPORT 421 TABLE 1.
Load more

Recommended publications
  • Deciphering the Origin of Cyclical Gravel Front and Shoreline Progradation and Retrogradation in the Stratigraphic Record
    Deciphering the origin of cyclical gravel front and shoreline progradation and retrogradation in the stratigraphic record John J. Armitage1, Peter A. Burgess2, Gary J. Hampson3, and Philip A. Allen3 1Department of Earth Science, Royal Holloway, University of London, Egham, UK; Now at Institut de Physique du Globe de Paris, 1 rue Jussieu, Paris, 75005, France; e-mail: [email protected] 2Department of Earth Science, Royal Holloway, University of London, Egham, UK 3Department of Earth Science and Engineering, Imperial College London, London, UK May 4, 2016 1 1 Abstract 2 Nearly all successions of near-shore strata exhibit cyclical movements of the shoreline, which 3 have commonly been attributed to cyclical oscillations in relative sea level (combining eustasy 4 and subsidence) or, more rarely, to cyclical variations in sediment supply. It has become accepted 5 that cyclical change in sediment delivery from source catchments may lead to cyclical movement 6 of boundaries such as the gravel front, particularly in the proximal segments of sediment routing 7 systems. In order to quantitatively assess how variations in sediment transport as a consequence 8 of change in relative sea-level and surface run-off control stratigraphic architecture, we develop a 9 simple numerical model of sediment transport and explore the sensitivity of moving boundaries 10 within the sediment routing system to change in upstream (sediment flux, precipitation rate) and 11 downstream (sea level) controls. We find that downstream controls impact the shoreline and sand 12 front, while the upstream controls can impact the whole system depending on the amplitude of 13 change in sediment flux and precipitation rate.
    [Show full text]
  • Upward Shallowing Platform Cycles a Response to 2.2 Billion Years of Lowamplitude, Highfrequency Milankovitch Band Sea Level
    PALEOCEANOGRAPHY,VOL. 1, NO. 4, PAGES 403-416, DECEMBER 1986 UPWARD SHALLOWING PLATFORM CYCLES: A RESPONSE TO 2.2 BILLION YEARS OF LOW-AMPLITUDE, HIGH-FREQUENCY (MILANKOVITCH BAND) SEA LEVEL OSCILLATIONS J. P. Grotzinger Lamont-Doherty Geological Observatory, Palisades, New York Abstract. Shallow-water carbonate perhaps influencing global sea level platforms, characterized by sequences of through minor changes related to small- small-scale upward shallowing cycles, are scale continental or alpine glaciation. common in the Phanerozoic and Proterozoic It is possible, then, that Milankovitch stratigraphic record. Proterozoic small- band climatic forcing has occurred for at scale cycles are commonly 1 to 10 m thick, least the last 2.2 billion years of earth have asymmetrically arranged facies, and history. are strikingly similar to Phanerozoic platform cycles. In some platform INTRODUCTION sequences (eg. Rocknest, Wallace, and Helena formations of early to middle The stratigraphic record of geologic Proterozoic age), it can be demonstrated history is characterized by intervals of that the lateral distribution of facies pronounced rhythmic or cyclic arrangement within cycles relates to systematic of facies such that repetitive groups of variations in platform paleogeography and rock units have component facies which topography. In the Rocknest formation, tend to occur in certain order. cycles with intervals of tepees and Sedimentary cyclicity has been documented pisolitic breccia formed on a topographic in many paleoenvironmental settings high (shoal complex) near the shelf edge ranging from fluvial to deep sea, in both rim, and provide evidence for eustatic carbonate- and siliciclastic-dominated falls in sea level at the end of each systems [e.g.
    [Show full text]
  • A Geoarchaeological Perspective on the Challenges and Trajectories of Mississippi Delta Communities
    Geomorphology 360 (2020) 107132 Contents lists available at ScienceDirect Geomorphology journal homepage: www.elsevier.com/locate/geomorph A geoarchaeological perspective on the challenges and trajectories of Mississippi Delta communities Elizabeth L. Chamberlain a,b,c,⁎, Jayur M. Mehta d, Tony Reimann c,JakobWallingac a Department of Earth and Environmental Sciences, Vanderbilt University, Nashville, TN, USA b Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY, USA c Netherlands Centre for Luminescence Dating, Soil Geography and Landscape group, Wageningen University, Wageningen, the Netherlands d Department of Anthropology, Florida State University, Tallahassee, FL, USA article info abstract Article history: Recent geochronology of the Mississippi Delta of coastal Louisiana, USA, provides a high-resolution record of land Received 31 October 2019 growth that facilitates the study of ancient settlement patterns in relation to delta evolution. We use stratigraphy Received in revised form 27 February 2020 and optically stimulated luminescence (OSL) dating to show that two Late Holocene earthen mounds were con- Accepted 27 February 2020 structed several hundred years after the land emerged from open water. This multi-century pause allowed nat- Available online 2 March 2020 ural processes of overbank and crevasse splay deposition to elevate the land surface, reduce flood risk, and foster desirable environmental conditions prior to human occupation. These results are applied to obtain new age con- Keywords: Coupled human-natural systems straints for a large number of at-risk or lost archaeological sites with little-to-no absolute chronology. We use our Mississippi Delta findings to comment on prehistoric, contemporary, and future human-landscape interactions in the Mississippi Optically stimulated luminescence dating Delta and other deltaic environments.
    [Show full text]
  • Article Is Available Engineers, Available At: Online At
    Earth Surf. Dynam., 6, 1155–1168, 2018 https://doi.org/10.5194/esurf-6-1155-2018 © Author(s) 2018. This work is distributed under the Creative Commons Attribution 4.0 License. Measuring subaqueous progradation of the Wax Lake Delta with a model of flow direction divergence John B. Shaw1, Justin D. Estep1,2, Amanda R. Whaling1, Kelly M. Sanks1, and Douglas A. Edmonds3 1Department of Geosciences, University of Arkansas, Fayetteville, 72701, USA 2Department of Geology and Geophysics, Texas A&M University, College Station, 77843, USA 3Department of Earth and Atmospheric Sciences, Indiana University, Bloomington, 47405, USA Correspondence: John B. Shaw ([email protected]) Received: 1 June 2018 – Discussion started: 22 June 2018 Revised: 8 November 2018 – Accepted: 19 November 2018 – Published: 30 November 2018 Abstract. Remotely sensed flow patterns can reveal the location of the subaqueous distal tip of a distributary channel on a prograding river delta. Morphodynamic feedbacks produce distributary channels that become shal- lower over their final reaches before the unchannelized foreset slopes basinward. The flow direction field over this morphology tends to diverge and then converge, providing a diagnostic signature that can be captured in flow or remote sensing data. A total of 21 measurements from the Wax Lake Delta (WLD) in coastal Louisiana and 317 measurements from numerically simulated deltas show that the transition from divergence to convergence occurs in a distribution that is centered just downstream of the channel tip, on average 132 m in the case of the WLD. These data validate an inverse model for remotely estimating subaqueous channel tip location. We apply this model to 33 images of the WLD between its initiation in 1974 and 2016.
    [Show full text]
  • Carbonate Platform Evolution: from a Bioconstructed Platform Margin to a Sand-Shoal System (Devonian, Guilin, South China)
    Sedimentology (2002) 49, 737–764 Carbonate platform evolution: from a bioconstructed platform margin to a sand-shoal system (Devonian, Guilin, South China) DAIZHAO CHEN*, MAURICE E. TUCKER , JINGQUAN ZHU* and MAOSHENG JIANG* *Institute of Geology and Geophysics, Chinese Academy of Sciences, PO Box 9825, Beijing 100029, China (E-mail: [email protected]) Department of Geological Sciences, University of Durham, Durham DH1 3LE, UK (E-mail: [email protected]) ABSTRACT The depositional organization and architecture of the middle–late Devonian Yangdi rimmed carbonate platform margin in the Guilin area of South China were related to oblique, extensional faulting in a strike-slip setting. The platform margin shows two main stages of construction in the late Givetian to Frasnian, with a bioconstructed margin evolving into a sand-shoal system. In the late Givetian, the platform margin was rimmed with microbial buildups composed mainly of cyanobacterial colonies (mostly Renalcis and Epiphyton). These grew upwards and produced an aggradational (locally slightly retrogradational) architecture with steep foreslope clinoforms. Three depositional sequences (S3–S5) are recognized in the upper Givetian strata, which are dominated by extensive microbialites. Metre-scale depositional cyclicity occurs in most facies associations, except in the platform-margin buildups and upper foreslope facies. In the latest Givetian (at the top of sequence S5), relative platform uplift (± subaerial exposure) and associated rapid basin subsidence (probably a block-tilting effect) caused large-scale platform collapse and slope erosion to give local scalloped embayments along the platform margin and the synchronous demise of microbial buildups. Subsequently, sand shoals and banks composed of ooids and peloids and, a little later, stromatoporoid buildups on the palaeohighs, developed along the platform margin, from which abundant loose sediment was transported downslope to form gravity-flow deposits.
    [Show full text]
  • Facies Analysis, Genetic Sequences, and Paleogeography of the Lower Part of the Minturn Formation (Middle Pennsylvanian), Southeastern Eagle Basin, Colorado
    Facies Analysis, Genetic Sequences, and Paleogeography of the Lower Part of the Minturn Formation (Middle Pennsylvanian), Southeastern Eagle Basin, Colorado U.S. GEOLOGICAL SURVEY BULLETIN 1 787-AA ^A2 Chapter AA Facies Analysis, Genetic Sequences, and Paleogeography of the Lower Part of the Minturn Formation (Middle Pennsylvanian), Southeastern Eagle Basin, Colorado By JOHN A. KARACHEWSKI A multidisciplinary approach to research studies of sedimentary rocks and their constituents and the evolution of sedimentary basins, both ancient and modern U.S. GEOLOGICAL SURVEY BULLETIN 1 787 EVOLUTION OF SEDIMENTARY BASINS UINTA AND PICEANCE BASINS U.S. DEPARTMENT OF THE INTERIOR MANUEL LUJAN, JR., Secretary U.S. GEOLOGICAL SURVEY Dallas L. Peck, Director Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government UNITED STATES GOVERNMENT PRINTING OFFICE: 1992 For sale by the Books and Open-File Report Sales U.S. Geological Survey Federal Center Box 25425 Denver, CO 80225 Library of Congress Cataloging-in-Publication Data Karachewski, John A. Facies analysis, genetic sequences, and paleogeography of the lower part of the Minturn Formation (Middle Pennsylvanian), Southeastern Eagle Basin, Colorado/ by John A. Karachewski. p. cm. (U.S. Geological Survey bulletin ; 1787) Evolution of sedimentary basins Uinta and Piceance basins ; ch. AA) Includes bibliographical references. Supt. of Docs, no.: I 19.3:1787 1. Sedimentation and deposition Colorado Eagle County. 2. Geology, Stratigraphic Pennsylvanian. 3. Geology, Stratigraphic Paleozoic. 4. Geology, Stratigraphic Colorado Eagle County. 5. Paleogeography Paleozoic. 6. Minturn Formation sedimentary basins Uinta and Piceance basins ; ch.
    [Show full text]
  • Tracking the Fate of Sediment After an Extreme Flood
    Hydrology Days 2018 Tracking the Fate of Sediment After an Extreme Flood Johanna S. Eidmann1, Sara L. Rathburn1, Ken Huson2 1Department of Geology, Colorado State University 2City of Longmont, CO Abstract. Assessing the ongoing sediment remobilization and deposition following an extreme flood is important for understanding disturbance response and recovery, and for addressing the challenges to water resource management. From September 9-15, 2013, a tropical storm generated over 350 mm of precipitation across the Colorado Front Range. The resulting 200-year flood triggering landslides and extreme channel erosion along North St. Vrain Creek that feeds Ralph Price Reservoir, an important water supply for the Cities of Lyons and Longmont, CO. The flood resulted in 10 m of aggradation upstream of the reservoir, transforming the inlet into an approach channel. Four years after the flood, downstream transport of flood sediment and deposition in the reservoir continues. This research tracks the fate of flood-derived sediment to understand the evolution and progradation of the delta as well as to inform reservoir management practices. Bathymetric DEM differencing from April 2014, April 2016, May 2017 and August 2017 (years 1, 2, 3 and 4 post-flood, respectively) demonstrates a constant rate of delta progradation of ~50 m per year since 2014. Between April 2016 and May 2017, the reservoir level was dropped approximately 10 m during reconstruction at the spillway. Despite the change in base level, year 4 pre-snowmelt runoff measurements indicate that the rate of progradation has remained comparable to the two years following the flood. Assuming that most sediment is transported during snowmelt runoff, year 4 post-snowmelt runoff bathymetry suggests a decline in progradation rate.
    [Show full text]
  • Framework and Evolution of a Transgressed Delta Lobe: the St
    University of New Orleans ScholarWorks@UNO University of New Orleans Theses and Dissertations Dissertations and Theses 5-15-2009 Framework and Evolution of a Transgressed Delta Lobe: The St. Bernard Shoals, Gulf of Mexico Bryan E. Rogers University of New Orleans Follow this and additional works at: https://scholarworks.uno.edu/td Recommended Citation Rogers, Bryan E., "Framework and Evolution of a Transgressed Delta Lobe: The St. Bernard Shoals, Gulf of Mexico" (2009). University of New Orleans Theses and Dissertations. 968. https://scholarworks.uno.edu/td/968 This Thesis is protected by copyright and/or related rights. It has been brought to you by ScholarWorks@UNO with permission from the rights-holder(s). You are free to use this Thesis in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights- holder(s) directly, unless additional rights are indicated by a Creative Commons license in the record and/or on the work itself. This Thesis has been accepted for inclusion in University of New Orleans Theses and Dissertations by an authorized administrator of ScholarWorks@UNO. For more information, please contact [email protected]. Framework and Evolution of a Transgressed Delta Lobe: The St. Bernard Shoals, Gulf of Mexico A Thesis Submitted to the Graduate Faculty of the University of New Orleans in partial fulfillment of the requirements for the degree of Master of Science in Earth and Environmental Sciences Coastal Geology by Bryan E. Rogers B.S. University of New Orleans, 2006 May 2009 Dedication I dedicate this master’s thesis to the late Dr.
    [Show full text]
  • Geomorphology, Hydrology, and Ecology of Great Basin Meadow
    Chapter 2: Controls on Meadow Distribution and Characteristics Dru Germanoski, Jerry R. Miller, and Mark L. Lord Introduction precipitation values are recorded in the central and southern Toiyabe and southern Toquima Mountains (fig. 1.4) and, as eadow complexes are located in distinct geomorphic expected, meadow complexes are abundant in those areas. Mand hydrologic settings that allow groundwater to be In contrast, basins located in sections of mountain ranges at or near the ground surface during at least part of the year. that do not have significant area at high elevation (greater Meadows are manifestations of the subsurface flow system, than approximately 2500 m) and that are characterized by and their distribution is controlled by factors that cause lo- limited annual precipitation contain relatively few meadows. calized zones of groundwater discharge. Knowledge of the For example, much of the Shoshone Range and the north- factors that serve as controls on groundwater discharge and ern and southernmost portions of the Toiyabe, Toquima, and formation of meadow complexes is necessary to understand Monitor Ranges are lower in elevation and receive less pre- why meadows occur where they do and how anthropogenic cipitation. Therefore, meadow complexes are uncommon in activities might affect their persistence and ecological condi- these regions. Analyses of color-enhanced satellite images tion. In this chapter, we examine physical factors that lead to of the region reveal that meadow complexes also are uncom- the formation of meadow complexes in upland watersheds mon in low-elevation mountain ranges in the surrounding of the central Great Basin. We then describe variations in area, including the Pancake Range, Antelope Range, the meadow characteristics across the region and parameters Park Range, and Simpson Park Mountains.
    [Show full text]
  • Dynamic Fluvial Systems and Gravel Progradation in the Himalayan Foreland
    Dynamic fluvial systems and gravel progradation in the Himalayan foreland Nicholas Brozovic´* Department of Earth Sciences, University of Southern California, Los Angeles, California 90089 Douglas W. Burbank†} ABSTRACT Keywords: fold-and-thrust belt, basin analysis, posits are generally marked by a paucity of fossil Siwaliks, Himalaya, magnetostratigraphy. material of known age, making biostratigraphy Although the large-scale stratigraphy of difficult. In such areas without fossils or radio- many terrestrial foreland basins is punctu- INTRODUCTION metrically dateable volcanic rocks, magnetostra- ated by major episodes of gravel prograda- tigraphy can sometimes provide excellent temporal tion, the relationships of such facies to hinter- The evolution of terrestrial foreland basins is control if sufficiently long, continuous strati- land tectonism and climate change are often marked by the reorganization of fluvial systems on graphic sections can be studied (Burbank, 1996). unclear. Structural reentrants provide win- spatial scales of kilometers to thousands of kilo- dows into older and more proximal parts of meters at temporal scales ranging from coseismic GEOLOGIC FRAMEWORK OF THE the foreland than are usually exposed, and to millennia (e.g., Meghraoui et al., 1988; Bur- HIMALAYAN FORELAND thus provide key insights to earlier phases of bank, 1992; Talling et al., 1995; Pivnik and John- foreland evolution. Our magnetostrati- son, 1995). Depositional systems within the fore- India-Asia collision was initiated as early as graphic studies show that, although the ma- land respond to changes in at least five factors: (1) 65 Ma in the westernmost part of the orogen jor lithofacies preserved within the Himachal flexure of the loaded plate, (2) incipient deforma- (Beck et al., 1995).
    [Show full text]
  • Modeling Coastal River, Wetland, and Shoreline Dynamics
    From the River to the Sea: Modeling Coastal River, Wetland, and Shoreline Dynamics by Katherine Murray Ratliff Earth & Ocean Sciences Duke University Date: Approved: A. Brad Murray, Supervisor Marco Marani Peter Haff James Heffernan Dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Earth & Ocean Sciences in the Graduate School of Duke University 2017 Abstract From the River to the Sea: Modeling Coastal River, Wetland, and Shoreline Dynamics by Katherine Murray Ratliff Earth & Ocean Sciences Duke University Date: Approved: A. Brad Murray, Supervisor Marco Marani Peter Haff James Heffernan An abstract of a dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Earth & Ocean Sciences in the Graduate School of Duke University 2017 Copyright c 2017 by Katherine Murray Ratliff All rights reserved except the rights granted by the Creative Commons Attribution-Noncommercial Licence Abstract Complex feedbacks dominate landscape dynamics over large spatial scales (10s { 100s km) and over the long-term (10s { 100s yrs). These interactions and feedbacks are particularly strong at land-water boundaries, such as coastlines, marshes, and rivers. Water, although necessary for life and agriculture, threatens humans and infrastructure during natural disasters (e.g., floods, hurricanes) and through sea-level rise. The goal of this dissertation is to better understand landscape morphodynamics in these settings, and in some cases, to investigate how humans have influenced these landscapes (e.g., through climate or land-use change). In this work, I use innovative numerical models to study the larger-scale emergent interactions and most critical variables of these systems, allowing me to clarify the most important feedbacks and explore large space and time scales.
    [Show full text]
  • Sea-Level Change and Delta Growth, Fraser Delta, British Columbia
    SEA-LEVEL CHANGE AND DELTA GROWTH: FRASER DELTA, BRITISH COLUMBIA Harry F. L. Williams B.Sc (HONS) Plymouth Polytechnic 1980 M.Sc University of ~ritishColumbia 1983 THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in the Department of Geography Harry F. L. Williams 1988 SIMON FRASER UNIVERSITY July 1988 All rights reserved. This work may not be reproduced in whole, or in part, by photocopy or other means, without permission of the author. APPROVAL Name : Harry F. L. ~illiams Degree: Ph. D Geography Title of thesis: Sea-Level Change And Delta Growth: Fraser Delta, British Columbia Examining Committee: Chairman: Dr. L. Evenden Dr. M. C. Roberts Senior Supervisor- Dr. -E. J. Hickin Dr. P~utchinson AD/[ J. L. ~uteinauer Geological Survey of Canada - -. J. D'Auria artment of Chemistjy 1,- - - y,,, D'- D'- External Examiner Department of Geography University of Calgary Date Approved: @/ PARTIAL COPYRIGHT LICENSE I hereby grant to Slmn Fraser University the right to lend my thesis, project or extended essay (the title of which is shown below) to users ot the Simon Fraser University Library, and to make partial or single copies only for such users or in response to a request from the library of any other university, or other educational institution, on its own behalf or for one of its users. I further agree that permission for multiple copying of this work for scholarly purposes may be granted by me or the Dean of Graduate Studies. It is understood that copying or publication of this work for financial gain shall not be allowed without my written permission.
    [Show full text]