Sedimentology of Arctic Fiords Experiment (SAFE): Project Introduction

The Geological Survey of Canada's project SAFE (Sedimentology of Arctic Fiords Experiment) was initiated in 1981 and is being carried out in a series of fiords situated along the east coast of Baffin Island. SAFE emphasizes the study of the Quaternary history and modern processes of arctic fiord environments. Project participants are interested in evaluating the significance of the comparatively rapid process rates and of the high-resolution sedimentary records that typify these settings. The key objectives of SAFE include: 1. To understand sandur development and the character of the resultant facies. 2. To understand the time-dependent influences of rivers, tides, waves, wind and deep-water renewal on fiord circulation and sedimentation patterns. 3. To use the geological record of raised marine deposits in establishing late Quaternary history within and between fiords. Following a reconnaissance of 10 fiords along the east coast of Baffin Island in 1982, 3 were selected for detailed study during the 1983 field season (Cambridge, Itirbilung, McBeth). The 1982 and 1983 investigations utilized the oceanographic research vessel CSS Hudson as an operations base. During both surveys, core sampling, CTD profiling, geophysical mapping and other heavy work were carried out from the Hudson up to the 100 m isobath. The shallow water operation was supported by two launches outfitted with equipment to carry the oceanographic and geological programs into nearshore uncharted areas. Field parties were landed to study raised marine deposits and glacial features. The 1983 survey was preceded by a helicopter-supported program that succeeded in mooring and recovering several strings of current meters and sediment traps near the heads of Cambridge and Itirbilung fiords.Key words: sediments, Quaternary, fiord, arctic, Baffin Island, inner shelfMots clés: sédiments, Quaternaire, fjord, Arctique, île de Baffin, zone interne du plateau continenta

Suspended Sediment Character and Distribution in McBeth Fiord, Baffin Island

Sediment concentration, particle-particle morphology and size data are used to identify the processes that control the distribution and dynamics of suspended sediment during the open water season in the McBeth Fiord, Baffin Island. Dominant processes include hemipelagic sedimentation below river plumes and sediment resuspension by wind-driven waves, internal waves and bottom currents, including those related to deep-water renewal. Suspended particles are composed of unflocculated mineral grains, planktonic detritus - such as from diatoms, radiolarian and dinoflagellates - and large particles of marine snow composed of mucoid stringers, fecal pellets, floccules, agglomerates and resuspended clay clasts. Strong offshore winds are capable of temporarily removing the surface seasonal layer in the fiord. That in turn may initiate the autumn cycle of deep-water exchange. Replacement of deep water within McBeth Fiord by water from the Baffin Shelf can also introduce shelf sediment to the fiord and cause the resuspension of sediment covering the outer sill complex. Alternatively, strong onshore winds can push the surface layer to the head of the fiord and significantly increase the surface layer volume of the inner fiord. Internal wave trains associated with such a surface layer surge and travelling in a landward direction can impact on the front of the delta situated at the head of the fiord and initiate resuspension of bottom sediments.Key words: Arctic,fiord, McBeth Fiord, suspended sediment, oceanography, wind events, resuspensionRÉSUMÉ. On se sert de données sur la concentration des sédiments, et la morphologie de particule à particule ainsi que sur la taille pour identifier les processus assurant la répartition et la dynamique des sédiments en suspension durant la saison d’eau libre dans le fjord McBeth de l'île de Baffin. Les processus dominants comprennent une sédimentation hémipélagiqsuoeu s les panaches des cours d’eau et la remise en suspension des sédiments par les vagues poussées par le vent, les vagues internes et cleosu rants de fond, y compris ceux reliés au renouvellement de l’eau profonde. Les particules en suspension se composent de granules minéraux nofnlo culés, de détritus planctoniques tels que ceux provenant de diatomées, radiolaires et péridiniens, ainsi que de grosses particules de neige marine composé de filaments mucoïdes, de boulettes fécales, de flocules, d’agglomérats et de clastes argileux remis en suspension. Des vents forts venant des terres peuvent enlever temporairement la couche de surface saisonnitre dans le fjord, ce qui peut alors déclencher le cycle automnal de l’échange d’eau profonde. Le remplacement de l’eau profonde dans le fjord McBeth par de l’eau venant de la plateforme de Baffin peut aussi amener des sédiments de la plateforme dans le fjord et causer une remise en suspension des sédiments couvrant l’ensemble du seuil externe. D’un autre côté, des vents forts venant du large peuvent pousser la couche de surface vers la tête du fjord et causer une importante augmentationdu volume de cette couche dans l’intérieur du fjord. Des séries de vagues internes associées une telle poussée de la couche de surface et voyageant en direction des terres peuvent venir s’écraser sur le front du delta situé à la tête du fjord et causeru ne remise en suspension des sédiments defond.Mots clés: Arctique, fjord, fjord McBeth, sédiments en suspension, ockanographie, événements éoliens, remise en suspensio

Basin-scale land use impacts on world deltas: Human vs natural forcings

A new global database of 86 deltas and river basins was analyzed to investigate the relative importance of deforestation and land use changes versus natural forcings in determining long-term total delta size. Results show that mean river flow and shelf slope were the most important variables, whereas population density and sediment load had a much lower importance. Deforestation and other variables related to land-use generally had a very small effect, but were more influential in a subset comprising Mediterranean and Black Sea deltas. As most deltas have developed over thousands of years, the much shorter-lived anthropogenic signals from deforestation and other landscape perturbations have had only secondary impact on the total area of deltas. Also, delta progradation is strongly influenced on sand deposition, whereas anthropogenic impacts on sediment load have more often impacted mostly the finer sediment being deposited offshore (prodelta deposits) or in the deltaic plain. These data disproves the hypothesis that delta size and growth is strongly influenced by human forcings, particularly for larger deltas, since Holocene delta building is mainly determined by natural forces. However, humans are influencing the geomorphology of deltas, particularly over the last century when the Anthropocene nature of deltas has become manifest. A more precise terminology is proposed to clarify concepts such as “human-made”, “human-engineered” or “human-influenced” deltas.info:eu-repo/semantics/acceptedVersio

Evolution of a Holocene delta driven by episodic sediment delivery and coseismic deformation, Puget Sound, Washington, USA

This paper is not subject to U.S. copyright. The definitive version was published in Sedimentology 53 (2006): 1211-1228, doi:10.1111/j.1365-3091.2006.00809.x.Episodic, large-volume pulses of volcaniclastic sediment and coseismic subsidence of the coast have influenced the development of a late Holocene delta at southern Puget Sound. Multibeam bathymetry, ground-penetrating radar (GPR) and vibracores were used to investigate the morphologic and stratigraphic evolution of the Nisqually River delta. Two fluvial–deltaic facies are recognized on the basis of GPR data and sedimentary characteristics in cores, which suggest partial emplacement from sediment-rich floods that originated on Mount Rainier. Facies S consists of stacked, sheet-like deposits of andesitic sand up to 4 m thick that are continuous across the entire width of the delta. Flat-lying, highly reflective surfaces separate the sand sheets and comprise important facies boundaries. Beds of massive, pumice- and charcoal-rich sand overlie one of the buried surfaces. Organic-rich material from that surface, beneath the massive sand, yielded a radiocarbon age that is time-correlative with a series of known eruptive events that generated lahars in the upper Nisqually River valley. Facies CF consists of linear sandbodies or palaeochannels incised into facies S on the lower delta plain. Radiocarbon ages of wood fragments in the sandy channel-fill deposits also correlate in time to lahar deposits in upstream areas. Intrusive, sand-filled dikes and sills indicate liquefaction caused by post-depositional ground shaking related to earthquakes. Continued progradation of the delta into Puget Sound is currently balanced by tidal-current reworking, which redistributes sediment into large fields of ebb- and flood-oriented bedforms.This study was supported by the Coastal and Marine Geology Program, and the Earthquake Hazards Program of the U.S. Geological Survey

Recent deforestation causes rapid increase in river sediment load in the Colombian Andes

Human induced soil erosion reduces soil productivity; compromises freshwater ecosystem services, and drives geomorphic and ecological change in rivers and their floodplains. The Andes of Colombia have witnessed severe changes in land-cover and forest loss during the last three decades with the period 2000 and 2010 being the highest on record. We address the following: (1) what are the cumulative impacts of tropical forest loss on soil erosion? and (2) what effects has deforestation had on sediment production, availability, and the transport capacity of Andean rivers? Models and observations are combined to estimate the amount of sediment liberated from the landscape by deforestation within a major Andean basin, the Magdalena. We use a scaling model BQART that combines natural and human forces, like basin area, relief, temperature, runoff, lithology, and sediment trapping and soil erosion induced by humans. Model adjustments in terms of land cover change were used to establish the anthropogenic-deforestation factor for each of the sub-basins. Deforestation patterns across 1980-2010 were obtained from satellite imagery. Models were employed to simulate scenarios with and without human impacts. We estimate that, 9% of the sediment load in the Magdalena River basin is due to deforestation; 482 Mt of sediments was produced due to forest clearance over the last three decades. Erosion rates within the Magdalena drainage basin have increased 33% between 1972 and 2010; increasing the river's sediment load by 44 Mt y-1. Much of the river catchment (79%) is under severe erosional conditions due in part to the clearance of more than 70% natural forest between 1980 and 2010. © 2015 Elsevier Ltd. All rights reserved

Modeling suspended sediment discharge from the Waipaoa River system, New Zealand: The last 3000 years

HydroTrend, a hydrologic-transport model, is used to simulate the water and suspended sediment discharge of the Waipaoa River system over the last 3 Kyr, a time period in which a well-documented sequence of natural events and anthropogenic activities that profoundly impacted drainage basin processes occurred. Comparisons between observed and simulated data show that the model output replicates the frequency and distribution of flow events and the suspended sediment concentration-discharge relationship, and the long-term trends in suspended sediment discharge are consistent with the sediment record preserved on the middle shelf. Water discharge tracks precipitation, and average annual discharge may have been up to 20% higher and 6% lower at different times in the past. Suspended sediment discharge changed from 2.3 ± 4.5 to 14.9 ± 8.7 Mt yr?1 during the Anthropocene, increasing by 140% after Polynesian arrival, by 350% after European colonization, and by 660% after the catchment headwaters were deforested.Applied GeologyCivil Engineering and Geoscience

Marine hyperpycnal flows : initiation, behavior and related deposits. A review

Marine and Petroleum Geology, v. 20, n. 6-8, p. 861-882, 2003. http://dx.doi.org/10.1016/j.marpetgeo.2003.01.003International audienc