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  • 1
    In: Sedimentology, Wiley, Vol. 65, No. 3 ( 2018-04), p. 877-896
    Abstract: A Froude‐scaled physical model of a proximal gravel‐bed braided river was used to connect the river morphological characteristics, and sedimentary processes and forms, to deposit geometry. High resolution continuous three‐dimensional topographic data were acquired from sequential photogrammetric digital elevation models paired with grain‐size surface maps derived from image analysis of textural properties of the surface. From these data, the full three‐dimensional development of the braided river deposit and grain‐size sorting patterns was compiled over an experimental time period of 41 h during which the model river reworked a large portion of the braided channel. The minimum surface of the deposit is developed progressively over time by erosion, migration and avulsion of channels, and by local scour at channel confluences. The maximum surface of the deposit is formed by amalgamation of braid bar surfaces and has less overall relief than the minimum surface. Confluence scour constitutes about 5% of the area of the minimum surface. Migration of individual confluences is limited to distances of the order of the width and length of the confluence, so that confluences do not form laterally extensive deposits and basal surfaces. Maximum and minimum surfaces have very similar grain‐size distributions, and there is no extensive basal coarse layer. Deposit maximum thickness is strongly associated with large channel confluences which occur as deeper areas along the main channel belt and make up a large proportion of the thickest portions of the deposit.
    Type of Medium: Online Resource
    ISSN: 0037-0746 , 1365-3091
    URL: Issue
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2018
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  • 2
    In: Sedimentology, Wiley, Vol. 66, No. 3 ( 2019-04), p. 963-982
    Abstract: This study presents a micromorphological analysis of liquefaction features (dykes, sills and sand blows) associated with the 2010 to 2011 Canterbury Earthquakes Sequence, dykes of an earlier generation of liquefaction (palaeoliquefaction) and hosting soil. The aim of this research was to determine whether diagnostic features existed that would allow robust identification of liquefaction features and discrimination of different generations of liquefaction features in thin sections. This study serves to enhance the tools available to support palaeoliquefaction studies and earthquake hazard assessment. Similarities were found in the sedimentary fabric between all forms and ages of liquefaction features distinct from hosting soil. Palaeoliquefaction features could also be distinguished on the basis of microscopic pedogenic characteristics. Liquefaction and palaeoliquefaction were investigated in two distinctive sedimentary settings: the floodplain of the Halswell River, and coastal sand dunes near or in Christchurch. Analysis was carried out on thin sections prepared from resin‐impregnated blocks of soil sediment hosting the liquefaction features. The fabric of modern liquefaction features in the alluvial and coastal system is similar, both showing a single grain micro‐structure, with moderate to well‐sorted grains with many simple packing voids and planar voids. In both environments it was possible to see evidence of fluidization such as water escape structures, cutans and silt caps. The palaeoliquefaction fabric can be distinguished from the modern liquefaction fabric by the presence of textural pedogenic features in the form of silt coating of grains, infilling of planar voids, coating and hypocoating of voids and excrement pedofeatures. The results presented in this manuscript demonstrated how thin section analysis can be a valuable tool to corroborate field identification of liquefaction features, and to discriminate between features of different relative ages where stratigraphic evidence is equivocal.
    Type of Medium: Online Resource
    ISSN: 0037-0746 , 1365-3091
    URL: Issue
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2019
    detail.hit.zdb_id: 2020955-1
    detail.hit.zdb_id: 206889-8
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  • 3
    In: Sedimentology, Wiley, Vol. 65, No. 5 ( 2018-08), p. 1777-1799
    Abstract: Sequences of lake sediments often form long and continuous records that may be sensitive recorders of seismic shaking. A multi‐proxy analysis of Lake Bohinj sediments associated with a well‐constrained chronology was conducted to reconstruct Holocene seismic activity in the Julian Alps (Slovenia). A seismic reflection survey and sedimentological analyses identified 29 homogenite‐type deposits related to mass‐wasting deposits. The most recent homogenites can be linked to historical regional earthquakes (i.e. 1348  ad , 1511  ad and 1690  ad ) with strong epicentral intensity [greater than ‘damaging’ ( VIII ) on the Medvedev–Sponheuer–Karnik scale]. The correlation between the historical earthquake data set and the homogenites identified in a core isolated from local stream inputs, allows interpretation of all similar deposits as earthquake related. This work extends the earthquake chronicle of the last 6600 years in this area with a total of 29 events recorded. The early Holocene sedimentary record is disturbed by a seismic event (6617 ± 94 cal yr  bp ) that reworked previously deposited sediment and led to a thick sediment deposit identified in the seismic survey. The period between 3500 cal yr  bp and 2000 cal yr  bp is characterized by a major destabilization in the watershed by human activities that led to increases in erosion and sedimentation rates. This change increased the lake's sensitivity to recording an earthquake (earthquake‐sensitivity threshold index) with the occurrence of 72 turbidite‐type deposits over this period. The high turbidite frequency identified could be the consequence of this change in lake earthquake sensitivity and thus these turbidites could be triggered by earthquake shaking, as other origins are discarded. This study illustrates why it is not acceptable to propose a return period for seismic activity recorded in lake sediment if the sedimentation rate varies significantly.
    Type of Medium: Online Resource
    ISSN: 0037-0746 , 1365-3091
    URL: Issue
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2018
    detail.hit.zdb_id: 2020955-1
    detail.hit.zdb_id: 206889-8
    SSG: 13
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  • 4
    Online Resource
    Online Resource
    Wiley ; 2015
    In:  Sedimentology Vol. 62, No. 3 ( 2015-04), p. 845-866
    In: Sedimentology, Wiley, Vol. 62, No. 3 ( 2015-04), p. 845-866
    Abstract: Small vertically oriented traction carpets are reported from the collapsed sandy fills of 100 m deep Devonian limestone sinkholes underlying the Lower Cretaceous Athabasca oil sands deposit in north‐eastern Alberta, Western Canada. Dissolution of 100 m of underlying halite salt beds caused cataclysmic collapse of the sinkhole floors and water saturated sinkhole sand fills to descend very rapidly. Turbulent currents flushed upper sinkhole fills of friable sandstone blocks and disaggregated sand and quartz pebble for tens of metres. Laminar deposits with inverse grading accumulated as many as six to eight curvilinear entrained pebble streaks, 10 to 30 cm long, vertically impinged against the sides of descending collapse blocks. These deposits were initiated as vertically oriented early stage traction carpets that interlocked fine sand grains and inversely graded overlying pebbles entrained below the dilute overlying turbulent flows. Vortexes that flushed these sinkhole fills and induced these depositional processes may have lasted only seconds before the very rapid descents abruptly halted. Some of the fabrics were suspended vertically in‐place and preserved from unlocking and obliteration. These small fabrics provide insight into the instability and ephemeral character of the transition from strong gravity‐driven grain falls to very early stages of traction carpet formation. These short‐lived deposits of very thin sand layers resulted from sufficient incipient frictional freezing that grain interlocking overcame, however briefly, the strong gravity drives of the vertical falls that would have otherwise dispersed grains and obliterated any organized fabric patterns. Tenuous frictionally locked grains were also suspended at the centres of hyperbolic grain fall flows that briefly developed between turbulent flow eddies, some of which were fortuitously preserved. Some of these suspended grain locking zones passed downward onto the relatively more stable surfaces of the rapidly descending block surfaces. The morphogenesis of these early stage traction carpets differ from more fully developed deposits elsewhere because of their short‐lived transport, dynamic instability and vertical orientation.
    Type of Medium: Online Resource
    ISSN: 0037-0746 , 1365-3091
    URL: Issue
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2015
    detail.hit.zdb_id: 2020955-1
    detail.hit.zdb_id: 206889-8
    SSG: 13
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  • 5
    Online Resource
    Online Resource
    Wiley ; 2018
    In:  Sedimentology Vol. 65, No. 4 ( 2018-06), p. 1378-1389
    In: Sedimentology, Wiley, Vol. 65, No. 4 ( 2018-06), p. 1378-1389
    Abstract: Models relating sediment supply to catchment properties are important in order to use the geological record to deduce landscape evolution and interplay between tectonics and climate. Water discharge ( Q w ) is an important factor in the widely used ‘ BQART ’ model, which relates sediment load to a set of measurable catchment parameters. Although many of the factors in this equation may be independently estimated with some degree of certainty in ancient systems, water discharge ( Q w ) certainly cannot. An analysis of a world database of modern catchments with 1255 entries shows that the commonly applied equation relating catchment area ( A ) to water discharge ( Q w  = 0·075A 0·8 ) does not predict water discharge from catchment area well in many cases ( R 2  = 0·5 and an error spanning about three orders of magnitude). This is because the method does not incorporate the effect of arid and wet climate on river water discharge. The inclusion of climate data into such estimations is an opportunity to refine these estimates, because generalized estimates of palaeoclimate can often be deduced on the basis of sedimentological data such as palaeosol types, mineralogy and palaeohydraulics. This paper investigates how the relationship between catchment area and river discharge varies with four runoff categories (arid, semi‐arid, humid and wet), which are recognizable in the geological record, and modifies the coefficient and exponent of the above‐mentioned equation according to these classes. This modified model yields improved results in relating discharge to catchment area ( R 2  = 0·95 and error spanning one order of magnitude) when core, outcrop or regional palaeoclimate reconstruction data are available in non‐arid systems. Arid systems have an inherently variable water discharge, and catchment area is less important as a control due to downstream losses. The model here is sufficient for many geological applications and makes it possible to include variations in catchment humidity in mass‐flux estimates in ancient settings.
    Type of Medium: Online Resource
    ISSN: 0037-0746 , 1365-3091
    URL: Issue
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2018
    detail.hit.zdb_id: 2020955-1
    detail.hit.zdb_id: 206889-8
    SSG: 13
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  • 6
    Online Resource
    Online Resource
    Springer Science and Business Media LLC ; 2015
    In:  Bulletin of Volcanology Vol. 77, No. 8 ( 2015-8)
    In: Bulletin of Volcanology, Springer Science and Business Media LLC, Vol. 77, No. 8 ( 2015-8)
    Type of Medium: Online Resource
    ISSN: 0258-8900 , 1432-0819
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2015
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    detail.hit.zdb_id: 1458483-9
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  • 7
    Online Resource
    Online Resource
    Elsevier BV ; 2009
    In:  Sedimentary Geology Vol. 220, No. 3-4 ( 2009-10), p. 135-
    In: Sedimentary Geology, Elsevier BV, Vol. 220, No. 3-4 ( 2009-10), p. 135-
    Type of Medium: Online Resource
    ISSN: 0037-0738
    RVK:
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2009
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    detail.hit.zdb_id: 2012818-6
    SSG: 13
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  • 8
    Online Resource
    Online Resource
    Elsevier BV ; 2010
    In:  Journal of Hydrology Vol. 388, No. 3-4 ( 2010-07), p. 399-413
    In: Journal of Hydrology, Elsevier BV, Vol. 388, No. 3-4 ( 2010-07), p. 399-413
    Type of Medium: Online Resource
    ISSN: 0022-1694
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2010
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    detail.hit.zdb_id: 1473173-3
    SSG: 13
    SSG: 14
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  • 9
    In: Geomorphology, Elsevier BV, Vol. 65, No. 1-2 ( 2005-2), p. 49-70
    Type of Medium: Online Resource
    ISSN: 0169-555X
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2005
    detail.hit.zdb_id: 2001554-9
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  • 10
    Online Resource
    Online Resource
    American Geophysical Union (AGU) ; 2007
    In:  Eos, Transactions American Geophysical Union Vol. 88, No. 43 ( 2007-10-23), p. 441-442
    In: Eos, Transactions American Geophysical Union, American Geophysical Union (AGU), Vol. 88, No. 43 ( 2007-10-23), p. 441-442
    Abstract: Lahars, an Indonesian word referring to a volcanic mudflow carrying up to 80 percent solid material by weight, are highly lethal, having caused more than 30,000 deaths since the late 1700s. Although they are a major hazard, particularly in the developing world where population growth and settlement of river terraces in volcanic areas are increasing societal vulnerability, their study is hindered by their unpredictable timing, capricious travel paths, dramatic changes in flow behavior as they erode and deposit sediment [ Pierson and Scott , 1985], and the fact that these high‐energy flows are dangerous to observers and measuring equipment. A unique opportunity to capture a complete data set on a single, discrete lahar event was presented following the 1995–1996 eruptions of Mount Ruapehu in the central North Island of New Zealand (Figure 1). This activity expelled the water in the summit Crater Lake, generating a series of eruption‐ and later rain‐triggered lahars [ Cronin et al. , 1997], and deposited about 8 meters of tephra (volcanic ash and rock fragments ranging from pebbles to carsized blocks) over its former overflow channel. On 18 March 2007, this fragile tephra dam, which had been impounding extra water in the refilling lake basin, failed, releasing 1.3 million cubic meters of water in less than 90 minutes and generating the largest lahar at Ruapehu in 100 years.
    Type of Medium: Online Resource
    ISSN: 0096-3941 , 2324-9250
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2007
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