Late Miocene marine fossil-rich, rock-fall, avalanche, mud-flow and debris-flow deposits adjoining and near the western margin of the Tawhero Basin, outer forearc North Island, New Zealand

1999 ◽  
Vol 90 (3) ◽  
pp. 189-201
Author(s):  
G. Neef
Keyword(s):  
New Zealand ◽  
Debris Flow ◽  
Fault Zone ◽  
Late Miocene ◽  
Pacific Plate ◽  
Rock Fall ◽  
Forearc Basin ◽  
Western Margin ◽  
Mud Flow

AbstractA late Miocene marine, massive fossil-rich, rock-fall/avalanche deposit, >42 m thick (base unexposed) and mud-flow and debris-flow deposits, commonly 0.2–4 m thick, are present adjoining and near to either margin of a 12 km long segment of the NE-trending Waihoki Fault/fault zone, near Pongaroa, North Wairarapa, North Island, New Zealand. The Waihoki Fault/fault zone lies in the outboard part of the onland part of the forearc. It forms the western margin of the Tawhero Basin, a forearc basin overlying a subducting Pacific plate, during 6.6–25 Ma. The basin had a partly dextral transpression history (especially in the Late Miocene) but the amount of dextral displacement along the Waihoki Fault/fault zone is unknown. It is likely that lightly indurated fossil-rich, rock-fall, mud-flow and debris-flow deposits were derived from the tops of fault slivers that were pushed upwards along the Waihoki Fault/fault zone during dextral faulting to reach the neritic zone.

scholarly journals Debris flow-slide initiation mechanisms in fill slopes, Wellington, New Zealand

Landslides ◽  
2021 ◽  
Author(s):  
J. M. Carey ◽  
B. Cosgrove ◽  
K. Norton ◽  
C. I. Massey ◽  
D. N. Petley ◽  
...  
Keyword(s):  
New Zealand ◽  
Debris Flow ◽  
Flow Slide

scholarly journals Back-calculation of the 2017 Piz Cengalo-Bondo landslide cascade with r.avaflow

2019 ◽  
Author(s):  
Martin Mergili ◽  
Michel Jaboyedoff ◽  
José Pullarello ◽  
Shiva P. Pudasaini
Keyword(s):  
Debris Flow ◽  
Flow Model ◽  
Rock Avalanche ◽  
Simulation Software ◽  
Process Models ◽  
Rock Fall ◽  
Model Parameters ◽  
Rock Slide ◽  
Glacier Ice ◽  
Initial Rock

Abstract. In the morning of 23 August 2017, around 3 million m3 of granitoid rock broke off from the east face of Piz Cengalo, SE Switzerland. The initial rock slide-rock fall entrained 0.6 million m3 of a glacier and continued as a rock(-ice) avalanche, before evolving into a channelized debris flow that reached the village of Bondo at a distance of 6.5 km after a couple of minutes. Subsequent debris flow surges followed in the next hours and days. The event resulted in eight fatalities along its path and severely damaged Bondo. The most likely candidates for the water causing the transformation of the rock avalanche into a long-runout debris flow are the entrained glacier ice and water originating from the debris beneath the rock avalanche. In the present work we try to reconstruct conceptually and numerically the cascade from the initial rock slide-rock fall to the first debris flow surge and thereby consider two scenarios in terms of qualitative conceptual process models: (i) entrainment of most of the glacier ice by the frontal part of the initial rock slide-rock fall and/or injection of water from the basal sediments due to sudden rise in pore pressure, leading to a frontal debris flow, with the rear part largely remaining dry and depositing mid-valley; and (ii) most of the entrained glacier ice remaining beneath/behind the frontal rock avalanche, and developing into an avalanching flow of ice and water, part of which overtops and partially entrains the rock avalanche deposit, resulting in a debris flow. Both scenarios can be numerically reproduced with the two-phase mass flow model implemented with the simulation software r.avaflow, based on plausible assumptions of the model parameters. However, these simulation results do not allow to conclude on which of the two scenarios is the more likely one. Future work will be directed towards the application of a three-phase flow model (rock, ice, fluid) including phase transitions, in order to better represent the melting of glacier ice, and a more appropriate consideration of deposition of debris flow material along the channel.

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