Chronology and processes of late Quaternary hillslope sedimentation in the eastern South Island, New Zealand

Borella, Josh W.; Quigley, Mark; Sohbati, Reza; Almond, Peter C.; Gravley, Darren M.; Murray, Andrew

doi:10.1002/jqs.2905

Cited by 6 publications

(14 citation statements)

References 72 publications

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“…CES rockfalls were characterized by boulder-size distribution, runout distance (the distance a rock travels down a slope from its source), sourcearea dimensions, and boulder-production rates over a range of triggering peak ground accelerations (Massey et al, 2012a(Massey et al, -e, 2014(Massey et al, , 2017Quigley and Mackey, 2014;Quigley et al, 2016). Subsequent field investigations revealed an abundance of pre-CES rockfall deposits in CES rockfall areas (Townsend and Rosser, 2012;Mackey and Quigley, 2014;Borella et al, observations support the reported lithologic descriptions for the two study locales. The inferred strike and dip for lava flows nearest to the study sites indicates a shallow inclination in a predominantly northerly direction for measurements nearest the Rapaki and Purau study sites (Hampton and Cole, 2009).…”

Section: Introductionsupporting

confidence: 63%

Geologic and geomorphic controls on rockfall hazard: how well do past rockfalls predict future distributions?

Borella¹,

Quigley²,

Krauss³

et al. 2019

Preprint

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Abstract. To evaluate the geospatial hazard relationships between recent (contemporary) rockfalls and their prehistoric predecessors, we compare the locations, physical characteristics, and lithologies of rockfall boulders deposited during the 2010–2011 Canterbury earthquake sequence (CES) (n = 185) with those deposited prior to the CES (n = 1093). Population ratios of pre-CES to CES boulders at two study sites vary spatially from 5:1 to 8.5:1. This is interpreted to reflect (i) variations in CES rockfall flux due to intra- and inter-event spatial differences in ground motions (e.g. directionality) and associated variations in source cliff responses, (ii) possible variations in the triggering mechanism(s), frequency, flux, record duration, boulder size distributions, and post-depositional mobilization of pre-CES rockfalls relative to CES rockfalls, and (iii) geological variations in the source cliffs of CES and pre-CES rockfalls. On interfluves, CES boulders traveled approximately 100 to 250 m further downslope than prehistoric (pre-CES) boulders, interpreted to reflect reduced resistance to CES rockfall transport due to preceding anthropogenic hillslope de-vegetation. Volcanic breccia boulders are more dimensionally equant, rounded, larger, and traveled further downslope than coherent lava boulders, illustrating clear geological control on rockfall hazard. In valley bottoms, the furthest-traveled pre-CES boulders are situated further downslope than CES boulders due to (i) remobilization of pre-CES boulders by post-depositional processes such as debris flows, and (ii) reduction of CES boulder velocities and travel distances by collisional impacts with pre-CES boulders. A considered earth-systems approach is required when using preserved distributions of rockfall deposits to predict the severity and extents of future rockfall events.

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Section: Introductionsupporting

confidence: 63%

Geologic and geomorphic controls on rockfall hazard: how well do past rockfalls predict future distributions?

Borella¹,

Quigley²,

Krauss³

et al. 2019

Preprint

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“…a) (Griffiths, ; Almond et al ., ), and cosmogenic 3 He dating of palaeorockfall boulders overlying the in situ loess (Mackey and Quigley, ). In situ loess at the Rapaki Study Site has been correlated to the Birdlings Flat loess (Borella et al ., , b). Intercalated volcanic ash within the Birdling's Flat loess (Fig.…”

Section: Site Description and Geological Contextmentioning

confidence: 97%

“…The palaeorockfall boulders identified on the same slope (Fig. b,c) have the same morphology, lithology and similar spatial distribution (except for maximum run‐out distance, see Borella et al, ) as modern boulders and imply that similar earthquakes are likely to have been responsible for past rockfall activity (Mackey and Quigley, ; Borella et al ., , b).…”

Section: Site Description and Geological Contextmentioning

confidence: 99%

“…c) have been distinguished on the basis of textural, compositional and grain‐size variations (Borella et al ., , b). A palaeosol has been identified at the top of the in situ loess and the top of the most recent colluvium contains an A‐horizon (Borella et al ., , b). The planar hillslope is dissected by numerous rills and channels (Fig.…”

Section: Site Description and Geological Contextmentioning

confidence: 99%

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Optical dating of loessic hillslope sediments constrains timing of prehistoric rockfalls, Christchurch, New Zealand

Sohbati

Borella

Murray

et al. 2016

J Quaternary Science

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Developing a robust chronology for mass-movement events is of crucial importance to understanding triggering mechanisms and assessing hazards. We constrain the emplacement time of four palaeorockfall boulders near Christchurch, New Zealand, using optically stimulated luminescence (OSL) of quartz and infrared stimulated luminescence dating (IRSL) of K-feldspar from colluvial loess deposits underlying and upslope of individual boulders. The quartz OSL and K-feldspar pIRIR 290 ages are all consistent with the stratigraphy and in excellent agreement with each other, indicating that all the boulders that overlie the in-situ loess and oldest loess colluvium unit must have been emplaced < 13 ka ago. A comparison of luminescence ages with cosmogenic 3 He surface-exposure ages from the surfaces of each boulder shows that two out of four boulders contain pre-deposition 3 He inheritance.Overall, the optical ages are consistent with both a prehistoric rockfall event at ~8-6 ka and a possible preceding event at ~14-13 ka, although the temporal resolution of the time of emplacement of individual boulders is ca. 3-5 ka. This resolution is not limited by age uncertainties but rather by the stratigraphy. This study is the first to show a successful application of luminescence dating to New

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“…Data availability. The research data can be publicly accessed at https://doi.org/10.5061/dryad.9km1t86(Borella et al, 2019).www.nat-hazards-earth-syst-sci.net/19/2249/2019/ Nat. Hazards Earth Syst.…”

mentioning

confidence: 99%

Geologic and geomorphic controls on rockfall hazard: how well do past rockfalls predict future distributions?

Borella

Quigley

Krauss

et al. 2019

Nat. Hazards Earth Syst. Sci.

Self Cite

View full text Add to dashboard Cite

Abstract. To evaluate the geospatial hazard relationships between recent (contemporary) rockfalls and their prehistoric predecessors, we compare the locations, physical characteristics, and lithologies of rockfall boulders deposited during the 2010–2011 Canterbury earthquake sequence (CES) (n=185) with those deposited prior to the CES (n=1093). Population ratios of pre-CES to CES boulders at two study sites vary spatially from ∼5:1 to 8.5:1. This is interpreted to reflect (i) variations in CES rockfall flux due to intra- and inter-event spatial differences in ground motions (e.g., directionality) and associated variations in source cliff responses; (ii) possible variations in the triggering mechanism(s), frequency, flux, record duration, boulder size distributions, and post-depositional mobilization of pre-CES rockfalls relative to CES rockfalls; and (iii) geological variations in the source cliffs of CES and pre-CES rockfalls. On interfluves, CES boulders traveled approximately 100 to 250 m further downslope than prehistoric (pre-CES) boulders. This is interpreted to reflect reduced resistance to CES rockfall transport due to preceding anthropogenic hillslope de-vegetation. Volcanic breccia boulders are more dimensionally equant and rounded, are larger, and traveled further downslope than coherent lava boulders, illustrating clear geological control on rockfall hazard. In valley bottoms, the furthest-traveled pre-CES boulders are situated further downslope than CES boulders due to (i) remobilization of pre-CES boulders by post-depositional processes such as debris flows and (ii) reduction of CES boulder velocities and travel distances by collisional impacts with pre-CES boulders. A considered earth-systems approach is required when using preserved distributions of rockfall deposits to predict the severity and extents of future rockfall events.

show abstract

Chronology and processes of late Quaternary hillslope sedimentation in the eastern South Island, New Zealand

Cited by 6 publications

References 72 publications

Geologic and geomorphic controls on rockfall hazard: how well do past rockfalls predict future distributions?

Geologic and geomorphic controls on rockfall hazard: how well do past rockfalls predict future distributions?

Optical dating of loessic hillslope sediments constrains timing of prehistoric rockfalls, Christchurch, New Zealand

Geologic and geomorphic controls on rockfall hazard: how well do past rockfalls predict future distributions?

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