Erosion rates of the New Zealand Southern Alps reflect long-term tectonics and transient climate

2021 ◽  
Author(s):  
Duna Roda-Boluda ◽  
Taylor Schildgen ◽  
Hella Wittmann-Oelze ◽  
Stefanie Tofelde ◽  
Aaron Bufe ◽  
...  
Keyword(s):  
New Zealand ◽  
Strike Slip ◽  
Southern Alps ◽  
Fault System ◽  
Tectonic Deformation ◽  
Seismic Cycle ◽  
Erosion Rates ◽  
Alpine Fault ◽  
Oblique Convergence

<p>The Southern Alps of New Zealand are the expression of the oblique convergence between the Pacific and Australian plates, which move at a relative velocity of nearly 40 mm/yr. This convergence is accommodated by the range-bounding Alpine Fault, with a strike-slip component of ~30-40 mm/yr, and a shortening component normal to the fault of ~8-10 mm/yr. While strike-slip rates seem to be fairly constant along the Alpine Fault, throw rates appear to vary considerably, and whether the locus of maximum exhumation is located near the fault, at the main drainage divide, or part-way between, is still debated. These uncertainties stem from very limited data characterizing vertical deformation rates along and across the Southern Alps. Thermochronology has constrained the Southern Alps exhumation history since the Miocene, but Quaternary exhumation is hard to resolve precisely due to the very high exhumation rates. Likewise, GPS surveys estimate a vertical uplift of ~5 mm/yr, but integrate only over ~10 yr timescales and are restricted to one transect across the range.</p><p>To obtain insights into the Quaternary distribution and rates of exhumation of the western Southern Alps, we use new <sup>10</sup>Be catchment-averaged erosion rates from 20 catchments along the western side of the range. Catchment-averaged erosion rates span an order of magnitude, between ~0.8 and >10 mm/yr, but we find that erosion rates of >10 mm/yr, a value often quoted in the literature as representative for the entire range, are very localized. Moreover, erosion rates decrease sharply north of the intersection with the Marlborough Fault System, suggesting substantial slip partitioning. These <sup>10</sup>Be catchment-averaged erosion rates integrate, on average, over the last ~300 yrs. Considering that the last earthquake on the Alpine Fault was in 1717, these rates are representative of inter-seismic erosion. Lake sedimentation rates and coseismic landslide modelling suggest that long-term (~10<sup>3</sup> yrs) erosion rates over a full seismic cycle could be ~40% greater than our inter-seismic erosion rates. If we assume steady state topography, such a scaling of our <sup>10</sup>Be erosion rate estimates can be used to estimate rock uplift rates in the Southern Alps. Finally, we find that erosion, and hence potentially exhumation, does not seem to be localized at a particular distance from the fault, as some tectonic and provenance studies have suggested. Instead, we find that superimposed on the primary tectonic control, there is an elevation/temperature control on erosion rates, which is probably transient and related to frost-cracking and glacial retreat.</p><p>Our results highlight the potential for <sup>10</sup>Be catchment-averaged erosion rates to provide insights into the magnitude and distribution of tectonic deformation rates, and the limitations that arise from transient erosion controls related to the seismic cycle and climate-modulated surface processes.</p><p> </p><p> </p>

Landscape Records 25 Million Years of Tectonic Evolution at an Oblique Convergent Margin, Marlborough Fault System, New Zealand

2021 ◽  
Author(s):  
Alison Duvall ◽  
Phaedra Upton ◽  
Camille Collett ◽  
Sarah Harbert ◽  
Seth Williams ◽  
...  
Keyword(s):  
New Zealand ◽  
Active Faults ◽  
Plate Boundary ◽  
Strike Slip ◽  
Fault System ◽  
Erosion Rates ◽  
Plate Collision ◽  
Drainage Patterns ◽  
Landscape Response ◽  
Oblique Convergent

<p>The landscape at the NE end of the South Island, New Zealand, records oblique plate collision over the last 25 million years. Using low-temperature thermochronology, geomorphic analyses, and cosmogenic <sup>10</sup>Be data, we document the landscape response to tectonics over long (10<sup>6</sup>) and short (10<sup>2</sup> – 10<sup>3</sup>) timescales in the Marlborough Fault System (MFS) and related Kaikōura Mountains. Our results indicate two broad stages of landscape evolution that reflect a changing plate boundary through time. In the eastern MFS, Miocene folding above blind thrust faults generated prominent Kaikōura Mountain peaks and formed major transverse rivers early in the plate collision history. By the Pliocene, rotation of the plate boundary led to a transition to dextral strike-slip faulting and widespread uplift that led to cycles of river channel offset, deflection and capture of tributaries draining across active faults, and headward erosion and captures by major transverse rivers within the western MFS. Despite clear evidence of recent rearrangement of the western MFS drainage network, rivers in this region still flow parallel to older faults, rather than along orthogonal traces of younger, active strike-slip faults. Such drainage patterns emphasize the importance of river entrenchment, showing that once rivers establish themselves along a structural grain, their capture or avulsion becomes difficult, even when exposed to new weakening and tectonic strain. Over short timescales (hundreds to thousands of years), apparent catchment-wide average erosion rates derived from <sup>10</sup>Be data show an increase from SW to NE, along strike of the Seaward Kaikōura Range. These rates mirror spatial increases in elevation, slope, channel steepness, and coseismic landslides, demonstrating that both landscape and geochronology patterns are consistent with an increase in rock uplift rate toward a subduction front that is presently locked on its southern end. Remarkably, the form of the topography, hillslopes, and rivers across much of the MFS appears to faithfully record the complex and changing tectonic history of a long-lived, oblique convergent plate boundary.</p>

Surface erosion assessment in the South-Canterbury downlands, New Zealand using 137Cs distribution

Soil Research ◽  
1995 ◽  
Vol 33 (5) ◽  
pp. 787 ◽  
Author(s):  
LR Basher ◽  
KM Matthews ◽  
L Zhi
Keyword(s):  
New Zealand ◽  
Mean Value ◽  
Slope Position ◽  
Surface Erosion ◽  
The South ◽  
Erosion And Deposition ◽  
Erosion Rates ◽  
Land Use Types ◽  
Radionuclide Tracer

Redistribution of the radionuclide tracer 137Cs was used to examine the pattern of erosion and deposition at two sites with contrasting long-term land uses (pasture and cropping) in the South Canterbury downlands, New Zealand. There were clear differences between the two land use types in variation in 137Cs concentrations and areal activity, erosion rates and topsoil depth variability. Erosion and deposition have resulted in greater variability and lower mean levels of 137Cs areal activity under cropping (46.3 mBq cm-2) than pasture (55.0 mBq cm-2). At the cropping site, erosion and deposition roughly balanced with the mean value over all sampling sites, suggesting no net soil loss, but considerable redistribution of soil within paddocks. At the pasture site results suggested slight net deposition. There was evidence for both sheet/rill and wind erosion being important in soil redistribution. While there was no difference in mean topsoil depth between pasture and cropping, there were significant differences with slope position. At the pasture site, there was little variation of topsoil depth with slope position, except for swales which tended to be deeper, whereas at the cropping site there was considerable variation in topsoil depth with slope position. Topsoil depth was a poor indicator of erosion status.

scholarly journals Simulation of past variability in seasonal snow in the Southern Alps, New Zealand

1995 ◽  
Vol 21 ◽  
pp. 377-382 ◽  
Author(s):  
B.B. Fitzharris ◽  
C.E. Garr
Keyword(s):  
New Zealand ◽  
Southern Alps ◽  
Model Output ◽  
Total Water ◽  
Seasonal Snow ◽  
Temperature And Precipitation ◽  
Major River ◽  
River Catchments ◽  
Snow Deposition

There are no systematic measurements of seasonal snow in the Southern Alps, New Zealand, so little information is available as to its past variability. To rectify this, a conceptual model is developed that calculates seasonal snow deposition, ablation and accumulation. The model is based on daily temperature and precipitation data from long-established climate stations about the Southern Alps. Output is given as daily specific net balance of snow at five elevation bands from 1000 to 2200 m and as total water stored as seasonal snow over several major river catchments. Model output is in general agreement when tested against the few historical observations of snow and is tuned to the long-term water balance. A chronology of seasonal snow is reconstructed from 1931 to 1993. Area-averaged annual maxima average 366 mm. They show no trend, but large inter-annual variability from less than 200 to over 650 mm w.e. Seasonal snow can peak at any time between September and January.

scholarly journals Climatic effects on rapid chemical and physical denudation rates measured with cosmogenic nuclides in the Ōhau catchment, New Zealand

2021 ◽  
Author(s):  
◽  
Maia Bellingham
Keyword(s):  
Carbon Dioxide ◽  
New Zealand ◽  
Chemical Weathering ◽  
Southern Alps ◽  
Grain Sizes ◽  
Denudation Rates ◽  
Climate Stability ◽  
Mountain Landscapes ◽  
Carbon Dioxide Cycling

<p>Understanding how active mountain landscapes contribute to carbon dioxide cycling and influences on long-term climate stability requires measurement of weathering fluxes from these landscapes. The few measured chemical weathering rates in the Southern Alps are an order of magnitude greater than in the rest of the world. Rapid tectonic uplift coupled with extreme orographic precipitation is driving exceptionally fast chemical and physical denudation. These rates suggest that weathering in landscapes such as the Southern Alps could play a significant role in carbon dioxide cycling. However, the relative importance of climate and tectonics driving these fast rates remains poorly understood.   To address this gap, in situ ¹⁰Be derived catchment-averaged denudation rates were measured in the Ōhau catchment, Canterbury, New Zealand. Denudation rates in the Dobson Valley within the Ōhau catchment, varied from 474 – 7,570 m Myr⁻¹, aside from one sub-catchment in the upper Dobson Valley that had a denudation rate of 12,142 m Myr⁻¹. The Dobson and Hopkins Rivers had denudation rates of 1,660 and 4,400 m Myr⁻¹ respectively, in these catchments. Dobson Valley denudation rates show a moderate correlation with mean annual precipitation (R²=0.459). This correlation supports a similar trend identified at local and regional scales, and at high rates of precipitation this may be an important driver of erosion and weathering.   Sampling of four grain sizes (0.125 to > 8 mm) at one site in the Dobson Valley resulted in variability in ¹⁰Be concentrations up to a factor of 2.5, which may be a result of each grain size recording different erosional processes. These observations demonstrate the importance of assessing potential variability and the need to sample consistent grain sizes across catchments.   Chemical depletion fractions measured within soil pits in the upper Dobson Valley indicate chemical weathering contributes 30% of total denudation, and that physical erosion is driving rapid total denudation. Chemical weathering appears to surpass any proposed weathering speed limit and suggests total weathering may not be limited by weathering kinetics. This research adds to the paucity of research in New Zealand, and for the first time presents ¹⁰Be derived denudation rates from the eastern Southern Alps, with estimates of the long-term weathering flux. High weathering fluxes in the Southern Alps uphold the hypothesis that mountain landscapes play an important role in carbon dioxide cycling and long-term climate stability.</p>

Abrupt strike-slip fault to subduction transition: The Alpine Fault-Puysegur Trench connection, New Zealand

Tectonics ◽  
2000 ◽  
Vol 19 (4) ◽  
pp. 688-706 ◽  
Author(s):  
Jean-Frédéric Lebrun ◽  
Geoffroy Lamarche ◽  
Jean-Yves Collot ◽  
Jean Delteil
Keyword(s):  
New Zealand ◽  
Strike Slip ◽  
Strike Slip Fault ◽  
Alpine Fault

scholarly journals Coseismic landsliding estimates for an Alpine Fault earthquake and the consequences for erosion of the Southern Alps, New Zealand

Geomorphology ◽  
2016 ◽  
Vol 263 ◽  
pp. 71-86 ◽  
Author(s):  
T.R. Robinson ◽  
T.R.H. Davies ◽  
T.M. Wilson ◽  
C. Orchiston
Keyword(s):  
New Zealand ◽  
Southern Alps ◽  
Alpine Fault

scholarly journals Triple junction kinematics accounts for the 2016 Mw7.8 Kaikoura earthquake rupture complexity

2019 ◽  
Vol 116 (52) ◽  
pp. 26367-26375 ◽  
Author(s):  
Xuhua Shi ◽  
Paul Tapponnier ◽  
Teng Wang ◽  
Shengji Wei ◽  
Yu Wang ◽  
...  
Keyword(s):  
New Zealand ◽  
Triple Junction ◽  
Large Scale ◽  
Strike Slip ◽  
Plate Motion ◽  
Fault System ◽  
Coseismic Deformation ◽  
Coseismic Slip ◽  
Slab Geometry ◽  
Kaikoura Earthquake

The 2016, moment magnitude (Mw) 7.8, Kaikoura earthquake generated the most complex surface ruptures ever observed. Although likely linked with kinematic changes in central New Zealand, the driving mechanisms of such complexity remain unclear. Here, we propose an interpretation accounting for the most puzzling aspects of the 2016 rupture. We examine the partitioning of plate motion and coseismic slip during the 2016 event in and around Kaikoura and the large-scale fault kinematics, volcanism, seismicity, and slab geometry in the broader Tonga–Kermadec region. We find that the plate motion partitioning near Kaikoura is comparable to the coseismic partitioning between strike-slip motion on the Kekerengu fault and subperpendicular thrusting along the offshore West–Hikurangi megathrust. Together with measured slip rates and paleoseismological results along the Hope, Kekerengu, and Wairarapa faults, this observation suggests that the West–Hikurangi thrust and Kekerengu faults bound the southernmost tip of the Tonga–Kermadec sliver plate. The narrow region, around Kaikoura, where the 3 fastest-slipping faults of New Zealand meet, thus hosts a fault–fault–trench (FFT) triple junction, which accounts for the particularly convoluted 2016 coseismic deformation. That triple junction appears to have migrated southward since the birth of the sliver plate (around 5 to 7 million years ago). This likely drove southward stepping of strike-slip shear within the Marlborough fault system and propagation of volcanism in the North Island. Hence, on a multimillennial time scale, the apparently distributed faulting across southern New Zealand may reflect classic plate-tectonic triple-junction migration rather than diffuse deformation of the continental lithosphere.

scholarly journals First evidence of active transpressive surface faulting at the front of the eastern Southern Alps, northeastern Italy. Insight on the 1511 earthquake seismotectonics

2018 ◽  
Author(s):  
Emanuela Falcucci ◽  
Maria Eliana Poli ◽  
Fabrizio Galadini ◽  
Giancarlo Scardia ◽  
Giovanni Paiero ◽  
...  
Keyword(s):  
Strike Slip ◽  
Southern Alps ◽  
Strike Slip Fault ◽  
Fault System ◽  
The Past ◽  
Fold And Thrust Belt ◽  
Northeastern Italy ◽  
Dextral Strike Slip Fault ◽  
Seismic Lines ◽  
Dextral Strike Slip

Abstract. We investigated the eastern corner of northeastern Italy, where the NW-SE trending dextral strike-slip fault systems of western Slovenia intersects the south-verging fold and thrust belt of the eastern Southern Alps . The area suffered the largest earthquakes of the region, among which are the 1511 (Mw 6.3) event and the two major shocks of the 1976 seismic sequence, with Mw = 6.4 and 6.1 respectively. The Colle Villano thrust and the Borgo Faris-Cividale strike-slip fault have been first analyzed by interpreting industrial seismic lines and then by performing morpho-tectonic and paleoseismological analyses. These different datasets indicate that the two structures define an active, coherent transpressive fault system that activated twice in the past two millennia, with the last event occurring around the 15th–17th century. The chronological information, and the location of the investigated fault system suggest its activation during the 1511 earthquake.

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