Calibration of the in situ cosmogenic 14C production rate in New Zealand's Southern Alps     

Irene Schimmelpfennig  Joerg M. Schaefer  Brent M. Goehring  Nathaniel Lifton  Aaron E. Putnam  David J. A. Barrell 《第四纪科学杂志》2012,27(7):671-674

In situ cosmogenic ¹⁴C (in situ ¹⁴C) analysis from quartz‐bearing rocks is a novel isotopic tool useful for quantifying recent surface exposure histories (up to ～25 ka). It is particularly powerful when combined with longer‐lived cosmogenic isotopes such as ¹⁰Be. Recent advances in the extraction of in situ ¹⁴C from quartz now permit the routine application of this method. However, only a few experiments to calibrate the production rate of in situ ¹⁴C in quartz have been published to date. Here, we present a new in situ ¹⁴C production rate estimate derived from a well‐dated debris flow deposit in the Southern Alps, New Zealand, previously used to calibrate ¹⁰Be production rates. For example, based on a geomagnetic implementation of the Lal/Stone scaling scheme we derive a spallogenic production rate of 11.4 ± 0.9 atoms ¹⁴C (g quartz)^?1 a^?1 and a ¹⁴C/¹⁰Be spallogenic production rate ratio of 3.0 ± 0.2. The results are comparable with production rates from previous calibrations in the northern hemisphere. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

How does forest structure affect root reinforcement and susceptibility to shallow landslides?          下载免费PDF全文

Christine Moos  Peter Bebi  Frank Graf  Josias Mattli  Christian Rickli  Massimiliano Schwarz 《地球表面变化过程与地形》2016,41(7):951-960

Forests can decrease the risk of shallow landslides by mechanically reinforcing the soil and positively influencing its water balance. However, little is known about the effect of different forest structures on slope stability. In the study area in St Antönien, Switzerland, we applied statistical prediction models and a physically‐based model for spatial distribution of root reinforcement in order to quantify the influence of forest structure on slope stability. We designed a generalized linear regression model and a random forest model including variables describing forest structure along with terrain parameters for a set of landslide and control points facing similar slope angle and tree coverage. The root distribution measured at regular distances from seven trees in the same study area was used to calibrate a root distribution model. The root reinforcement was calculated as a function of tree dimension and distance from tree with the root bundle model (RBMw). Based on the modelled values of root reinforcement, we introduced a proxy‐variable for root reinforcement of the nearest tree using a gamma distribution. The results of the statistical analysis show that variables related to forest structure significantly influence landslide susceptibility along with terrain parameters. Significant effects were found for gap length, the distance to the nearest trees and the proxy‐variable for root reinforcement of the nearest tree. Gaps longer than 20 m critically increased the susceptibility to landslides. Root reinforcement decreased with increasing distance from trees and is smaller in landslide plots compared to control plots. Furthermore, the influence of forest structure strongly depends on geomorphological and hydrological conditions. Our results enhance the quantitative knowledge about the influence of forest structure on root reinforcement and landslide susceptibility and support existing management recommendations for protection against gravitational natural hazards. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Salt and ice crystallisation in porous sandstones   总被引：1，自引：0，他引：1  

Joerg Ruedrich  Siegfried Siegesmund 《Environmental Geology》2007,52(2):225-249

Salt and ice crystallisation in the pore spaces causes major physical damage to natural building stones. The damaging effect of these processes can be traced back to physically induced stress inside of the rock while crystallizing. The increasing scientific research done during the past century has shown that there are numerous parameters that have an influence on the weathering resulting from these processes. However, the working mechanisms of the stress development within the rock and its material dependency are still subject to discussion. This article gives an overview of salt and ice weathering. Additionally, laboratory results of various sandstones examined are presented. Salt crystallisation tests and freeze/thaw tests were done to obtain information about how crystallisation weathering depends on material characteristics such as pore space, water transportation, and mechanical features. Simultaneous measuring of the length alternating during the salt and ice crystallisation has revealed detailed information on the development of crystal in the pore spaces as well as the development of stress. These findings can help to understand the damaging mechanisms.  相似文献   

Mitigating depletion of a porous geothermal aquifer in the Pannonian sedimentary basin     

Nina Rman  Andrej Lapanje  Joerg Prestor  Michael J. O’Sullivan 《Environmental Earth Sciences》2016,75(8):723

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Gas migration through Opouawe Bank at the Hikurangi margin offshore New Zealand     

Stephanie Koch  Henning Schroeder  Matthias Haeckel  Christian Berndt  Joerg Bialas  Cord Papenberg  Dirk Klaeschen  Andreia Plaza-Faverola 《Geo-Marine Letters》2016,36(3):187-196

This study presents 2D seismic reflection data, seismic velocity analysis, as well as geochemical and isotopic porewater compositions from Opouawe Bank on New Zealand’s Hikurangi subduction margin, providing evidence for essentially pure methane gas seepage. The combination of geochemical information and seismic reflection images is an effective way to investigate the nature of gas migration beneath the seafloor, and to distinguish between water advection and gas ascent. The maximum source depth of the methane that migrates to the seep sites on Opouawe Bank is 1,500–2,100 m below seafloor, generated by low-temperature degradation of organic matter via microbial CO₂ reduction. Seismic velocity analysis enabled identifying a zone of gas accumulation underneath the base of gas hydrate stability (BGHS) below the bank. Besides structurally controlled gas migration along conduits, gas migration also takes place along dipping strata across the BGHS. Gas migration on Opouawe Bank is influenced by anticlinal focusing and by several focusing levels within the gas hydrate stability zone.  相似文献   

First Record of the Belemnite Genus Hibolithes from Late Jurassic–Early Cretaceous Turbidites from Malaysia     

Muhammad MURTAZA  Abdul Hadi Abd RAHMAN  Joerg MUTTERLOSE  Najiatun NAJLA  Mazshurraiezal Bin NASIR 《《地质学报》英文版》2021,95(2):333-341

Discovery of the remains of belemnites referred to the Hibolithes sp. from the Jurassic–Cretaceous Pedawan Formation in Sarawak, on the island of Borneo(Malaysia) comprises four fragments of belemnite rostra. The specimens are characterized by multiple fractures and vein filling. Two fragments measuring about 130 mm are relatively intact, with only part of the alveolar region missing; a third piece represents the middle part of a rostrum, and the fourth specimen is too fragmentary to be assigned to any specific part of the rostrum. Based on specimen characteristics, a Tithonian–Hauterivian age is plausible. The sedimentary succession that yielded the belemnite material comprises thick shale that reflects the Te division of Bouma sequence. The occurrence of a Hibolithes taxon in the uppermost Jurassic to lowermost Cretaceous Pedawan Formation sediments in Borneo reflects a near to global palaeobiogeographic distribution of this genus.  相似文献