DOCSLIB.ORG

The Null Hypothesis: Globally Steady Rates of Erosion, Weathering Fluxes and Shelf Sediment Accumulation During Late Cenozoic Mountain Uplift and Glaciation

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Null Hypothesis: Globally Steady Rates of Erosion, Weathering Fluxes and Shelf Sediment Accumulation During Late Cenozoic Mountain Uplift and Glaciation doi: 10.1111/ter.12185 Debate Article The null hypothesis: globally steady rates of erosion, weathering fluxes and shelf sediment accumulation during Late Cenozoic mountain uplift and glaciation Jane K. Willenbring and Douglas J. Jerolmack Department of Earth and Environmental Science, University of Pennsylvania, 240 South 33rd Street, Philadelphia, PA 19104-6316, USA ABSTRACT At the largest time and space scales, the pace of erosion and over the last 10 Ma and support the null hypothesis – that glo- chemical weathering is determined by tectonic uplift rates. bal rates of landscape change have remained constant over this Deviations from equilibrium arise from the transient response time period, despite global climate change and mountain build- of landscape denudation to climatic and tectonic perturbations. ing events. This work undermines the hypothesis that increased We posit that the constraint of mass balance, however, makes weathering due to mountain building or climate change was it unlikely that such disequilibrium persists at the global scale the primary agent for a decrease in global temperatures. over millions of years, as has been proposed for late Cenozoic erosion. We synthesize weathering fluxes, global sedimentation Terra Nova, 28: 11–18, 2016 rates, sediment yields and tectonic motions to show a remarkable constancy in the pace of Earth-surface evolution FORUM: The Editors of Terra Nova invite readers to contribute to a discussion of this topic on our forum at https://terranova- debates.wordpress.com/ (Berner, 1991; Berner and Caldeira, rates (Herman et al., 2013). Introduction 1997; Maher and Chamberlain, 2014) Researchers have attempted to cau- The evolution of the Earth’s surface and physical erosion (which causes sally link these trends to global cool- occurs through the erosion of rock unloading that can induce a tectonic ing with two related hypotheses. In and redistribution of mass. This is response; Montgomery, 1994; Whip- the first, rapid erosion associated ultimately driven by energy from two ple, 2009). In order to unravel these with Himalayan uplift acted to drive sources: tectonics, which contributes feedbacks and linkages, many Cenozoic cooling by reducing CO2 to erosion indirectly through uplift; researchers have turned to global levels through increased silicate and climate, which influences erosion datasets of the relevant parameters. weathering (Raymo and Ruddiman, and weathering via temperature and Of particular interest has been the 1992). The second reverses the arrow precipitation. Global changes in tec- late Cenozoic period, when a global of causality: in this case it is argued tonic motions or climate might be cooling trend, of unknown origin, climatic cooling and glacial-intergla- expected to produce global changes began at 50 Ma and culminated in cial swings acted to increase denuda- in the rate of landscape evolution; continental glaciations during the last tion rates, perhaps even inducing however, feedbacks among climate, 2–3 Ma in Eurasia and North and enhanced mountain uplift (Molnar tectonics and geomorphology may South America (Ruddiman, 2010). and England, 1990; Zhang et al., enhance or obscure the relation Global rates of tectonic motion have 2001; Molnar, 2004). between ‘signal’ and ‘response’. For been either constant over this inter- The climatic cooling trend of the example, although the engine for val, as determined from ages of crust late Cenozoic is not in dispute. We plate tectonics is mantle convection, (Fig. 1; Rowley, 2002, 2013), or challenge the premise that global researchers have proposed that rates decreasing, as determined from slab rates of landscape denudation have of tectonic uplift may depend and flux models that incorporate the changed, however, on both concep- feedback on global climate through geometry of the subduction zone tual and empirical grounds. There silicate weathering (which draws (Van Der Meer et al., 2014). Obser- are numerous possibilities for feed- down CO2 and leads to cooling) vations also point to an apparent backs and linkages among climate, increase (c.f. Sadler, 1981) in land- tectonics, erosion and weathering. scape denudation over the same time However, mass balance places a con- Correspondence: Dr. Jane Kathryn Wil- period, as indicated by global sedi- straint on the magnitude and persis- lenbring, Department of Earth and Envi- ment accumulation curves from the tence of denudation rates. Enhanced ronmental Science, University of world’s oceans and sedimentary weathering and erosion reduces Pennsylvania, 240 South 33rd Street, basins (Hay et al., 1988; Molnar, slopes and grows valleys, which act Philadelphia, PA 19104-6316, USA. Tel.: 2004) and, more recently, a global to decrease denudation back towards +001 215 746-8197; e-mail: erosion@sas. compilation of mountain erosion being in balance with tectonic uplift upenn.edu © 2015 John Wiley & Sons Ltd 11 Steady rates of erosion for the last 10 Ma • J. K. Willenbring and D. J. Jerolmack Terra Nova, Vol 28, No. 1, 11–18 ............................................................................................................................................................. Crust production these results for understanding feed- production (km mean rate of crust mean rate backs between climate and geomor- ) phology are discussed. –1 27 3.2 26 3.0 Evidence from geochemical 2 25 2.8 year proxies –1 rate (mm year rate mean half-spreading mean half-spreading 0 ) Recent proxies suggest stabilization 0246810 of atmospheric CO2 at near-modern Age (My) levels since the late Oligocene, despite continued global cooling Fig. 1 Rates of tectonic forcing over the last 10 Ma are steady. Figure adapted (Beerling and Royer, 2011; Fig. 2A). from Rowley (2002, 2013) and data digitized from Rowley (2002; Fig. 4). This stationary greenhouse gas com- position implies nearly constant chemical weathering over the last (Whipple et al., 1999). As with many ple question of how climate impacts 10–20 Ma, unless there were signifi- problems, it is an issue of scale. landscape probably has as many cant changes in the organic carbon Large regions of the globe may sus- answers as there are landscapes. cycle (Pagani et al., 2009) that some- tain denudation rates that are far The simplest, that is, null, hypoth- how compensated for changes in from being in equilibrium with tec- esis is that global rates of erosion, weathering. Several recent hypotheses tonics, but for only limited periods weathering and sediment accumula- attempting to relate global cooling to of time. Alternatively, at-a-point tion have been constant over the the Northern Hemisphere glaciation rates of denudation may be much time interval in question. This con- have therefore abandoned increased larger than tectonic rates over long stancy is expected from the mass weathering fluxes as a cause (Knies periods of time, but are compensated conservation constraint, given that et al., 2014; Woodard et al., 2014). by lower rates elsewhere. To make global rates of tectonic motion have Other proxies brought to bear on this the case for sustained and enhanced not varied over the late Cenozoic issue have ambiguities that limit our denudation rates globally over sev- (Rowley, 2002, 2013). Ultimately, the interpretive ability. In the past, the eral millions of years, one needs to long time-scales needed to affect glo- rising late Cenozoic 87Sr/86Sr record demonstrate that: (1) erosion and bal heat production, and the correla- was thought to be an indicator of weathering rates are somehow decou- tion of mantle viscosity to mantle increased continental weathering pled from tectonics at the largest temperature, preclude any global (Raymo et al., 1988; Capo and scales; and (2) there is a convincing changes in tectonic rates. We do not DePaolo, 1990). However, this record and causal relation between climate have sufficient knowledge of the has been shown to be sensitive to the and denudation rates at the global mechanisms of weathering, erosion, isotopic ratio of the sedimentary scale. Regarding (1), while numerous geodynamics and climate to address source area (Richter et al., 1992) and studies have reported disequilibrium competing hypotheses from a theo- to the proportion of physical to between erosion and tectonics over retical/modelling perspective. Rather, chemical weathering (Derry and shorter timescales, models and data we must rely on empirical findings, France-Lanord, 1996). Similarly, Nd show a convergence of the two over which fall into three main categories. and Pb isotopes indicate only a timescales greater than 106 years The first approach is finding a geo- change in weathering style or source, (Koppes and Montgomery, 2009; chemical proxy that indirectly not a total weathering flux (Willen- Whipple, 2009), although transience records processes such as the flux of bring and von Blanckenburg, 2010a). may also persist for millions of years erosion or weathering products to Two proxies that are thought to (Willenbring et al., 2013). Further, the oceans and integrates over large describe the total weathering flux are for studies that infer denudation areas (continents, ocean basins or the 10Be/9Be ratio and the d7Li from basin-integrating (i.e. spatially global). The second approach is mea- record. 10Be/9Be systematics are rela- averaging) sediment yields, global suring erosion or weathering rates tively simple, thus may finally con- rates do not show any significant (or total denudation rate) in as many strain the flux of weathering trend over timescales longer than
Load more

Recommended publications
  • The Rock Cycle Compressed and Cemented to Form What the Original Rocks on Earth Were Like
    | The Rock Cycle compressed and cemented to form what the original rocks on Earth were like. sedimentary rock, such as sandstone. IMMG has some excellent examples of Soluble material can be precipitated from these extraterrestrial visitors in our The continual set of processes affecting water to form sedimentary rocks such as meteorite exhibit. rocks is called the rock cycle. All existing limestone and gypsum. Sedimentary rocks rocks on Earth have been changed over can also be exposed at the surface and Various examples of the three different time by various geologic processes. Earth undergo erosion, providing materials for types of rocks are listed below. Specimens was formed about 4.6 billion years ago, and future sedimentary rocks. of some of these rocks can be found the oldest known rock unit is found in throughout the museum. Canada, dated at just over 4 billion years If sedimentary rocks become buried deep old. This rock material was altered by heat within the crust, they can be subjected to How many can you find? and pressure into the metamorphic rock high heat and pressure along with physical gneiss. stresses such as compression or extension, Igneous which transforms them into metamorphic rocks such as schist or gneiss Originally all of Earth’s crustal rocks had Basalt Gabbro Diorite an igneous origin. They start as semi- (“metamorphic” simply means “changed molten magma in the upper mantle and form”). Sometimes igneous rocks can be Rhyolite Syenite Andesite either rise to the surface as extrusive lava metamorphosed by similar processes (like Granite Granodiorite Obsidian (like basalt) in volcanoes and oceanic rifts, granite into gneiss).
    [Show full text]
  • Final Report Analysis of Sediment Cores from the West Bay Diversion Receiving Area
    Final Report Analysis of Sediment Cores from the West Bay Diversion Receiving Area Alexander S. Kolker Louisiana Universities Marine Consortium 1. Introduction A. The setting. The Mississippi River Delta has one of the highest rate of land loss of any system on Earth. Present day rates of land loss average about 62 km2 yr‐1, and exceeded 100 km2 yr‐1 during the 1970s (Barras et al., 2003; Day et al., 2007). The causes of this land loss are numerous and a partial list includes high rates of subsidence, reduced sediment deposition, changes in the tidal prism of the delta's coastal bays, global sea level rise, hurricane impacts, salt water intrusion, canal construction, invasive species, and biogeochemical changes that are unfavorable for plant growth (Barras, 2006; Darby and Turner, 2008; Day et al., 2007; Fitzgerald et al., 2004; Gagliano et al., 1981; Kolker et al., 2010; Reed, 2002; Tornqvist et al., 2008). These drivers of wetland loss exist on a landscape that naturally experiences cycles of land gain and loss that result from changes in the course of the Mississippi River and occur on time scales decades to millennia (Coleman, 1988; Roberts, 1997; Tornqvist et al., 1996; Wells and Coleman, 1987). One potentially powerful way to restore the Mississippi River Delta is to partially divert the flow of the Mississippi River, thereby allow sediments and freshwater to enter the coastal landscape in a manner that mimics natural land‐building processes (Day et al., 2007; LACPRA, 2007; LADNR, 1998). Several natural and semi‐natural diversions provide strong evidence of the potential for river diversions to build land.
    [Show full text]
  • Tectonic Control on 10Be-Derived Erosion Rates in the Garhwal Himalaya, India Dirk Scherler,1,2 Bodo Bookhagen,3 and Manfred R
    JOURNAL OF GEOPHYSICAL RESEARCH: EARTH SURFACE, VOL. 119, 1–23, doi:10.1002/2013JF002955, 2014 Tectonic control on 10Be-derived erosion rates in the Garhwal Himalaya, India Dirk Scherler,1,2 Bodo Bookhagen,3 and Manfred R. Strecker 1 Received 28 August 2013; revised 13 November 2013; accepted 26 November 2013. [1] Erosion in the Himalaya is responsible for one of the greatest mass redistributions on Earth and has fueled models of feedback loops between climate and tectonics. Although the general trends of erosion across the Himalaya are reasonably well known, the relative importance of factors controlling erosion is less well constrained. Here we present 25 10Be-derived catchment-averaged erosion rates from the Yamuna catchment in the Garhwal Himalaya, 1 northern India. Tributary erosion rates range between ~0.1 and 0.5 mm yrÀ in the Lesser 1 Himalaya and ~1 and 2 mm yrÀ in the High Himalaya, despite uniform hillslope angles. The erosion-rate data correlate with catchment-averaged values of 5 km radius relief, channel steepness indices, and specific stream power but to varying degrees of nonlinearity. Similar nonlinear relationships and coefficients of determination suggest that topographic steepness is the major control on the spatial variability of erosion and that twofold to threefold differences in annual runoff are of minor importance in this area. Instead, the spatial distribution of erosion in the study area is consistent with a tectonic model in which the rock uplift pattern is largely controlled by the shortening rate and the geometry of the Main Himalayan Thrust fault (MHT). Our data support a shallow dip of the MHT underneath the Lesser Himalaya, followed by a midcrustal ramp underneath the High Himalaya, as indicated by geophysical data.
    [Show full text]
  • Uplift Rate Transients at Subduction Margins Due to Earthquake Clustering
    Originally published as: Mouslopoulou, V., Oncken, O., Hainzl, S., Nicol, A. (2016): Uplift rate transients at subduction margins due to earthquake clustering. - Tectonics, 35, 10, pp. 2370—2384. DOI: http://doi.org/10.1002/2016TC004248 PUBLICATIONS Tectonics RESEARCH ARTICLE Uplift rate transients at subduction margins due 10.1002/2016TC004248 to earthquake clustering Key Points: Vasiliki Mouslopoulou1, Onno Oncken1, Sebastian Hainzl1, and Andrew Nicol2 • Transient uplift rates along fore-arc settings due to earthquake clustering 1German Research Centre for Geosciences, GFZ Helmholtz Centre Potsdam, Potsdam, Germany, 2Department of Geological • Earthquakes nucleate mostly on upper plate splay faults and less on the plate Sciences, University of Canterbury, Christchurch, New Zealand interface • Late Quaternary paleoshorelines may provide seismic hazard information Abstract Coastal uplift is common in continental fore-arc systems, with elevated paleoshorelines along seismically quiet subduction indicating that uplift rates can vary dramatically over time on individual margins. The origins of these margins changes in uplift rates are examined using a global data set of paleoshorelines together with 2-D numerical models of subduction systems. Empirical paleoshoreline data (N = 282) from eight subduction margins Supporting Information: indicate that uplift rates are generally not steady state and varied by up to a factor of 20 during the late • Supporting Information S1 ≤ fi • Table S1 Quaternary ( 125 ka). On many subduction margins uplift rates increase to the present day, a nding which • Supporting Information S2 we attribute to sampling bias toward those locations where Holocene uplift rates have been highest (with respect to other global margins which have undergone fast subsidence or no vertical motion—e.g., a Correspondence to: property akin to the so-called Sadler effect).
    [Show full text]
  • The Stratigraphy Machine Andrew D
    The Stratigraphy Machine Andrew D. Miall, University of Toronto John H. Holbrook, Texas Christian University Summary The stratigraphic record is constructed by multiple geological processes acting over time scales as short as a few seconds to as long as hundreds of millions of years. The probability of preservation of the products of high-frequency processes is very low. The full range of depositional and removal processes constitutes what may be termed a “Stratigraphy Machine.” Sedimentation rates and time scales Peter Sadler (1981) generated a graph that has long puzzled geologists – he Figure 1. Sadler’s (1981) relationship explained demonstrated that sedimentation rates in terms of the range of geological processes vary inversely with the duration of the that generate the sedimentary record. The elapsed time over which these rates are numbers in the boxes refer to a proposed measured, from the temporary flood-plain “Sedimentation Rate Scale” (Miall, 2015). deposits beside a river to the complete fill of a major sedimentary basin. This relationship has been referred to as the “Sadler effect.” Lengthy sections representing long time periods include a large number of sedimentary breaks. In fact, Ager (1973) remarked that the sedimentary record is “more gap than record.” However, it has taken the maturation of sedimentology and stratigraphy to provide a complete explanation of the Sadler effect. The science of stratigraphy has been revolutionized over the last fifty years. The emergence of sequence stratigraphy as the standard method for documentation and analysis, the increased sophistication of facies analysis and other sedimentological methods of documentation and interpretation, and the increasing accuracy and precision of the Geological Time Scale, have enabled ever more refined interpretations of geological processes.
    [Show full text]
  • Channel Morphology and Bedrock River Incision: Theory, Experiments, and Application to the Eastern Himalaya
    Channel morphology and bedrock river incision: Theory, experiments, and application to the eastern Himalaya Noah J. Finnegan A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy University of Washington 2007 Program Authorized to Offer Degree: Department of Earth and Space Sciences University of Washington Graduate School This is to certify that I have examined this copy of a doctoral dissertation by Noah J. Finnegan and have found that it is complete and satisfactory in all respects, and that any and all revisions required by the final examining committee have been made. Co-Chairs of the Supervisory Committee: ___________________________________________________________ Bernard Hallet ___________________________________________________________ David R. Montgomery Reading Committee: ____________________________________________________________ Bernard Hallet ____________________________________________________________ David R. Montgomery ____________________________________________________________ Gerard Roe Date:________________________ In presenting this dissertation in partial fulfillment of the requirements for the doctoral degree at the University of Washington, I agree that the Library shall make its copies freely available for inspection. I further agree that extensive copying of the dissertation is allowable only for scholarly purposes, consistent with “fair use” as prescribed in the U.S. Copyright Law. Requests for copying or reproduction of this dissertation may be referred
    [Show full text]
  • Exhumation Processes
    Exhumation processes UWE RING1, MARK T. BRANDON2, SEAN D. WILLETT3 & GORDON S. LISTER4 1Institut fur Geowissenschaften,Johannes Gutenberg-Universitiit,55099 Mainz, Germany 2Department of Geology and Geophysics, Yale University, New Haven, CT 06520, USA 3Department of Geosciences, Pennsylvania State University, University Park, PA I 6802, USA Present address: Department of Geological Sciences, University of Washington, Seattle, WA 98125, USA 4Department of Earth Sciences, Monash University, Clayton, Victoria VIC 3168,Australia Abstract: Deep-seated metamorphic rocks are commonly found in the interior of many divergent and convergent orogens. Plate tectonics can account for high-pressure meta­ morphism by subduction and crustal thickening, but the return of these metamorphosed crustal rocks back to the surface is a more complicated problem. In particular, we seek to know how various processes, such as normal faulting, ductile thinning, and erosion, con­ tribute to the exhumation of metamorphic rocks, and what evidence can be used to distin­ guish between these different exhumation processes. In this paper, we provide a selective overview of the issues associated with the exhuma­ tion problem. We start with a discussion of the terms exhumation, denudation and erosion, and follow with a summary of relevant tectonic parameters. Then, we review the charac­ teristics of exhumation in differenttectonic settings. For instance, continental rifts, such as the severely extended Basin-and-Range province, appear to exhume only middle and upper crustal rocks, whereas continental collision zones expose rocks from 125 km and greater. Mantle rocks are locally exhumed in oceanic rifts and transform zones, probably due to the relatively thin crust associated with oceanic lithosphere.
    [Show full text]
  • Taters Versus Sliders: Evidence for A
    Member Recognition Issue VOL. 31, NO. 7 | J U LY 2 021 ’Taters versus Sliders: Evidence for a Long-Lived History of Strike-Slip Displacement along the Canadian Arctic Transform System (CATS) EXPAND YOUR LIBRARY with GSA E-books The GSA Store offers hundreds of e-books, most of which are only $9.99. These include: • popular field guides and maps; Special Paper 413 • out-of-print books on prominent topics; and Earth and • discontinued series, such as Engineering How GeologistsMind: Think Geology Case Histories, Reviews in and Learn about the Earth Engineering Geology, and the Decade of North American Geology. Each book is available as a PDF, including plates and supplemental material. Popular topics include ophiolites, the Hell Creek Formation, mass extinctions, and plates and plumes. edited by Cathryn A. Manduca and David W. Mogk Shop now at https://rock.geosociety.org/store/. JULY 2021 | VOLUME 31, NUMBER 7 SCIENCE 4 ’Taters versus Sliders: Evidence for a Long- Lived History of Strike Slip Displacement along the Canadian Arctic Transform System (CATS) GSA TODAY (ISSN 1052-5173 USPS 0456-530) prints news and information for more than 22,000 GSA member readers William C. McClelland et al. and subscribing libraries, with 11 monthly issues (March- April is a combined issue). GSA TODAY is published by The Geological Society of America® Inc. (GSA) with offices at Cover: Geologists studying structures along the Petersen Bay 3300 Penrose Place, Boulder, Colorado, USA, and a mail- fault, a segment of the Canadian Arctic transform system (CATS), ing address of P.O. Box 9140, Boulder, CO 80301-9140, USA.
    [Show full text]
  • Sedimentological Constraints on the Initial Uplift of the West Bogda Mountains in Mid-Permian
    www.nature.com/scientificreports OPEN Sedimentological constraints on the initial uplift of the West Bogda Mountains in Mid-Permian Received: 14 August 2017 Jian Wang1,2, Ying-chang Cao1,2, Xin-tong Wang1, Ke-yu Liu1,3, Zhu-kun Wang1 & Qi-song Xu1 Accepted: 9 January 2018 The Late Paleozoic is considered to be an important stage in the evolution of the Central Asian Orogenic Published: xx xx xxxx Belt (CAOB). The Bogda Mountains, a northeastern branch of the Tianshan Mountains, record the complete Paleozoic history of the Tianshan orogenic belt. The tectonic and sedimentary evolution of the west Bogda area and the timing of initial uplift of the West Bogda Mountains were investigated based on detailed sedimentological study of outcrops, including lithology, sedimentary structures, rock and isotopic compositions and paleocurrent directions. At the end of the Early Permian, the West Bogda Trough was closed and an island arc was formed. The sedimentary and subsidence center of the Middle Permian inherited that of the Early Permian. The west Bogda area became an inherited catchment area, and developed a widespread shallow, deep and then shallow lacustrine succession during the Mid- Permian. At the end of the Mid-Permian, strong intracontinental collision caused the initial uplift of the West Bogda Mountains. Sedimentological evidence further confrmed that the West Bogda Mountains was a rift basin in the Carboniferous-Early Permian, and subsequently entered the Late Paleozoic large- scale intracontinental orogeny in the region. The Central Asia Orogenic Belt (CAOB) is the largest accretionary orogen on Earth, which was formed by the amalgamation of multiple micro-continents, island arcs and accretionary wedges1–5.
    [Show full text]
  • Climate, Tectonics, and the Morphology of the Andes
    Climate, tectonics, and the morphology of the Andes David R. Montgomery Greg Balco Sean D. Willett Department of Geological Sciences, University of Washington, Seattle 98195-1310, USA ABSTRACT Large-scale topographic analyses show that hemisphere-scale climate variations are a ®rst-order control on the morphology of the Andes. Zonal atmospheric circulation in the Southern Hemisphere creates strong latitudinal precipitation gradients that, when incor- porated in a generalized index of erosion intensity, predict strong gradients in erosion rates both along and across the Andes. Cross-range asymmetry, width, hypsometry, and maximum elevation re¯ect gradients in both the erosion index and the relative dominance of ¯uvial, glacial, and tectonic processes, and show that major morphologic features cor- relate with climatic regimes. Latitudinal gradients in inferred crustal thickening and struc- tural shortening correspond to variations in predicted erosion potential, indicating that, like tectonics, nonuniform erosion due to large-scale climate patterns is a ®rst-order con- trol on the topographic evolution of the Andes. Keywords: geomorphology, erosion, tectonics, climate, Andes. INTRODUCTION we argue for the ®rst-order importance of earthquake cycle. Some studies have attribut- The presence or absence of mountain rang- large-scale climate zonations and resulting dif- ed local variations in structural, metamorphic, es at the global scale is determined by the lo- ferences in geomorphic processes to the mor- and geomorphic characteristics of the central cation and type of plate boundaries. Other fac- phology of mountain ranges. Andes to erosion (Gephart, 1994; Masek et al., tors become important in the evolution of 1994; Horton, 1999), but none has considered individual mountain systems.
    [Show full text]
  • Shelf Sedimentation on a Tectonically Active Margin: a Modern Sediment Budget for Poverty Continental Shelf, New Zealand
    ARTICLE IN PRESS MARGO-04425; No of Pages 13 Marine Geology xxx (2009) xxx–xxx Contents lists available at ScienceDirect Marine Geology journal homepage: www.elsevier.com/locate/margeo Shelf sedimentation on a tectonically active margin: A modern sediment budget for Poverty continental shelf, New Zealand Andrea J. Miller, Steven A. Kuehl ⁎ Virginia Institute of Marine Science, 1208 Greate Road, P.O. Box 1346, Gloucester Point, VA 23062, USA article info abstract Available online xxxx The combination of high sediment yields and the prevalence of tectonically controlled accommodation on collision margins such as that adjacent to the Waipaoa River, NZ, create the potential for these areas to Keywords: contain high-resolution records of natural and anthropogenic signals. This study describes modern (100-yr) Waipaoa River sedimentation patterns off the Waipaoa and quantifies a sediment budget for the continental shelf, which is continental margin compared to long-term Holocene trends. 210Pb and 239,240Pu geochronologies reveal three main shelf shelf sedimentation depocenters. Two of these depocenters are located in subsiding synclinal basins on the mid-shelf, landward 210Pb geochronology 239,240Pu geochronology of the actively deforming Ariel and Lachlan anticlines. The depocenters exhibit accumulation rates ranging −1 210 fi sediment budget from 0.75 to 1.5cmyr and display both steady-state and non-steady-state Pb activity pro les. Textural characteristics of the non-steady-state cores indicate the possible preservation of flood event layers. The third depocenter is located near the shelf break and has accumulation rates as high as 1.0cmyr−1. The inner shelf and central mid-shelf are characterized by low, uniform 210Pb activity profiles and low accumulation rates, indicating that sediment is bypassing the inner shelf region and being deposited on the mid- to outer shelf.
    [Show full text]
  • Extension Rates Impact on Endorheic Drainage Longevity and Regional Sediment Discharge
    Extension rates impact on endorheic drainage longevity and regional sediment discharge Michael A. Berry1 Jolante van Wijk1, Daniel García-Castellanos2, Daniel Cadol1, Erica Emry1 1- New Mexico Tech; Socorro, NM 2- Instituto de Ciencias de la Tierra Jaume Almera (ICTJA-CSIC), Barcelona, Spain Tectonic and climate drivers exert co-equal forces on the evolution of tectonic sedimen- tary basins. The Rio Grande rift and its drainages provide a backdrop for discussing which drivers drive the transition from endorheic or closed drainage basins to exorheic or open, through-going drainage basins, with both climatic and tectonic drivers being pro- posed by researchers. With a dearth of regional scale extensional landscape modeling studies to draw from, we explore the impact of tectonic extension on endorheic-exorheic transitions and regional sediment and water discharge in both a “dry” and “wet” runoff regimes. We show that holding climate-induced runoff constant, that greater extensional rates correspond to a longer period of sedimentation capture, tectonically induced gradi- ents significantly increases sedimentation long after tectonic activity has terminated, and that developing an endorheic basin is very difficult in high runoff regimes. Implementation of FastScape into reusable software components Benoît Bovy (1) and Jean Braun (1) (1) GFZ Potsdam, Germany We present ongoing work on the development of open-source software around FastScape, a name used to designate a set of efficient algorithms for solving common problems in landscape evolution modelling. The software suite is divided into components that can be reused in many different contexts including experi- mentation, model coupling and direct integration within various scientific software ecosystems.
    [Show full text]