Recent progress in landslide dating

2014 ◽  
Vol 39 (2) ◽  
pp. 168-198 ◽  
Author(s):  
Tomáš Pánek
Keyword(s):  
South America ◽  
Recent Progress ◽  
Age Determination ◽  
Cosmic Ray ◽  
Data Sets ◽  
Mountain Areas ◽  
Scottish Highlands ◽  
Exposure Dating ◽  
Continental Scale ◽  
Dating Methods

Recent progress of dating techniques has greatly improved the age determination of various types of landslides. Since the turn of the 21st century, the number of dated landslides throughout the world has increased several fold and the introduction of modern dating methods (e.g. cosmic ray exposure dating) has enabled the dating of new landslide features and elements. Based on the analysis of >950 dated landslides (of which 734 have been dated since the year 2000), it is clear that the predominant traditional strategies have continued to rely on the radiocarbon method; however, there is a remarkable trend of using cosmic ray exposure techniques for dating both the accumulation (e.g. landslide boulders) and the depletion (e.g. landslide scarps) parts of landslides. Furthermore, an increasing number of slope failures is determined by a multi-dating approach, which enables the verification of particular dating methods. Although coherent regional landslide chronologies are still relatively scarce in comparison with extensive databases of fluvial, glacial and/or eolian landforms, they offer important insights into temporal landslide distribution, long-term landslide behavior and their relationships with paleoenvironmental changes. The most extensive data sets exist for the mountain areas of North America (Pacific Coast Ranges), South America (Andes), Europe (Alps, Scottish Highlands, Norway, Carpathians and Apennines), the Himalaya-Tibet orogeny and the Southern Alps of New Zealand. Dated landslides in the plate interiors are lacking, especially in South America, Africa and Australia. Despite the fact that some dating results are well correlated with major regional and continental-scale changes in the seismic activity, moisture abundance, glacier regimes and vegetation patterns, some of these results contradict previously established straightforward hypotheses. This indicates the rather complex chronological behavior of landslides, reflecting both intrinsic (e.g. gradual stress relaxation within a rock mass) and external factors, including high-magnitude earthquakes or heavy rainfalls.

scholarly journals Measurements of Cosmogenic 14C Produced by Spallation in High-Altitude Rocks

Radiocarbon ◽  
1992 ◽  
Vol 34 (3) ◽  
pp. 737-744 ◽  
Author(s):  
A. J. T. Jull ◽  
Amy E. Wilson ◽  
George S. Burr ◽  
Laurence J. Toolin ◽  
Douglas J. Donahue
Keyword(s):  
Mass Spectrometry ◽  
High Altitude ◽  
Accelerator Mass Spectrometry ◽  
Cosmic Ray ◽  
Exposure Dating ◽  
The Past ◽  
Dating Methods ◽  
Ray Effects ◽  
Cosmic Ray Effects ◽  
Higher Sensitivity

The production of radioisotopes at the Earth's surface by cosmic-ray effects has been discussed for many years. Only in the past few years, with the higher sensitivity provided by accelerator mass spectrometry (AMS) in detecting 10Be, 26A1 and 36Cl, have the radioisotopes produced in this way been measured. We report here our measurements of cosmogenic 14C in terrestrial rocks at high altitude, and comparisons to other exposure-dating methods.

Glacier Change and Paleoclimate Applications of Cosmogenic-Nuclide Exposure Dating

2020 ◽  
Vol 48 (1) ◽  
pp. 21-48 ◽  
Author(s):  
Greg Balco
Keyword(s):  
Climate Changes ◽  
Cosmic Ray ◽  
Glacier Change ◽  
Valuable Insight ◽  
Mountain Areas ◽  
Data Set ◽  
Mountain Glaciers ◽  
Exposure Dating ◽  
Geologic Record ◽  
Globally Distributed

Surface exposure dating using cosmic-ray-produced nuclides has been applied to determine the age of thousands of landforms produced by alpine glaciers in mountain areas worldwide. These data are potentially an extensive, easily accessible, and globally distributed paleoclimate record. In particular, exposure-dated glacier chronologies are commonly applied to study the dynamics of massive, abrupt climate changes characteristic of the transition between the Last Glacial Maximum and the present interglacial climate. This article reviews developments in exposure dating from the perspective of whether this goal is achievable and concludes that ( a) individual exposure-dated landforms cannot, in general, be associated with millennial-scale climate events at high confidence, but ( b) dating uncertainties appear to be geographically and temporally unbiased, so the data set as a whole can be used to gain valuable insight into regional and global paleoclimate dynamics. Future applications of exposure-age chronologies of glacier change should move away from reliance on individual dated landforms and toward synoptic analysis of the global data set. ▪  Mountain glaciers worldwide leave a geologic record of their past advances and retreats, which reflect past climate changes. ▪  Geochemical dating methods based on cosmic-ray-produced nuclides have been used to date these deposits at thousands of sites worldwide. ▪  This data set is potentially an extensive, accessible, and globally distributed paleoclimate record.

A deterministic approach toward isostatic gravity residuals—A case study from South America

Geophysics ◽  
1996 ◽  
Vol 61 (4) ◽  
pp. 1022-1033 ◽  
Author(s):  
David A. Chapin
Keyword(s):  
South America ◽  
Gravity Data ◽  
Crustal Thickness ◽  
Crustal Thickening ◽  
Density Contrast ◽  
Data Sets ◽  
Topographic Effects ◽  
Continental Scale ◽  
Free Air ◽  
Free Air Gravity

A new deterministic method for correcting isostatic effects in gravity data sets overcomes the deficiencies of empirically based methods. This technique produces a superior gravity image for South America and has application to other continental‐scale gravity data sets. The basis for the correction is the Airy‐Heiskanen isostatic model, which assumes that surface topography is supported by crustal thickening. The three key parameters, (1) the crustal thickness at sea‐level, (2) the surface reduction density, and (3) the density contrast between the crust and the mantle, are determined directly from the elevation, free‐air gravity, and Bouguer gravity data sets. The surface density parameter of 2.60 g/cc is determined using a new fractal technique. This technique assumes that the topography is fractal. The best value for density is that which minimizes the fractal component caused by topographic effects. The new value is substantially different than the 2.67 g/cc density assumed by many previous workers for most continental‐scale data sets. The crust/mantle density contrast parameter of 0.45 g/cc is determined by comparison between the densities determined from crossplots of the Bouguer values versus elevation. The crustal thickness parameter of 30 km is determined using a spectral method applied to the free‐air gravity. The results of this work are not only an isostatic residual map, but a methodology that cross checks the data for quality control. The final isostatic residual map can be used with confidence for basin evaluation throughout the continent of South America. Basins at high elevations, like the eastern foreland basins of the Andes and the Altiplano Basin, are imaged better by using this method.

scholarly journals Synergistic roles of climate warming and human occupation in Patagonian megafaunal extinctions during the Last Deglaciation

2016 ◽  
Vol 2 (6) ◽  
pp. e1501682 ◽  
Author(s):  
Jessica L. Metcalf ◽  
Chris Turney ◽  
Ross Barnett ◽  
Fabiana Martin ◽  
Sarah C. Bray ◽  
...  
Keyword(s):  
Climate Change ◽  
South America ◽  
Climate Warming ◽  
Human Impacts ◽  
Detailed Comparison ◽  
Data Sets ◽  
Last Deglaciation ◽  
Human Presence ◽  
Continental Scale ◽  
Radiocarbon Data

The causes of Late Pleistocene megafaunal extinctions (60,000 to 11,650 years ago, hereafter 60 to 11.65 ka) remain contentious, with major phases coinciding with both human arrival and climate change around the world. The Americas provide a unique opportunity to disentangle these factors as human colonization took place over a narrow time frame (~15 to 14.6 ka) but during contrasting temperature trends across each continent. Unfortunately, limited data sets in South America have so far precluded detailed comparison. We analyze genetic and radiocarbon data from 89 and 71 Patagonian megafaunal bones, respectively, more than doubling the high-quality Pleistocene megafaunal radiocarbon data sets from the region. We identify a narrow megafaunal extinction phase 12,280 ± 110 years ago, some 1 to 3 thousand years after initial human presence in the area. Although humans arrived immediately prior to a cold phase, the Antarctic Cold Reversal stadial, megafaunal extinctions did not occur until the stadial finished and the subsequent warming phase commenced some 1 to 3 thousand years later. The increased resolution provided by the Patagonian material reveals that the sequence of climate and extinction events in North and South America were temporally inverted, but in both cases, megafaunal extinctions did not occur until human presence and climate warming coincided. Overall, metapopulation processes involving subpopulation connectivity on a continental scale appear to have been critical for megafaunal species survival of both climate change and human impacts.

scholarly journals Modeling the statistical distributions of cosmogenic exposure dates from moraines

2009 ◽  
Vol 2 (2) ◽  
pp. 1407-1446 ◽  
Author(s):  
P. J. Applegate ◽  
N. M. Urban ◽  
K. Keller ◽  
R. B. Alley
Keyword(s):  
Cosmic Rays ◽  
Numerical Models ◽  
Cosmic Ray ◽  
Companion Paper ◽  
Data Sets ◽  
Skewed Distributions ◽  
Exposure Dating ◽  
Long Tails ◽  
The Mean ◽  
Geomorphic Processes

Abstract. Cosmogenic exposure dating provides a method for estimating the ages of glacial moraines deposited in the last ~105 years. Cosmic rays break atoms in surface rocks at predictable rates. Thus, the ages of moraines are directly related to the concentrations of cosmic ray-produced nuclides in rocks on the moraine surfaces, under ideal circumstances. However, many geomorphic processes may interfere with cosmogenic exposure dating. Because of these processes, boulders sometimes arrive at the moraines with preexisting concentrations of cosmogenic nuclides, or else the boulders are partly shielded from cosmic rays following deposition. Many methods for estimating moraine ages from cosmogenic exposure dates exist in the literature, but we cannot assess the appropriateness of these methods without knowing the parent distribution from which the dates were drawn on each moraine. Here, we make two contributions. First, we describe numerical models of two geomorphic processes, moraine degradation and inheritance, and their effects on cosmogenic exposure dating. Second, we assess the robustness of various simple methods for estimating the ages of moraines from collections of cosmogenic exposure dates. Our models estimate the probability distributions of cosmogenic exposure dates that we would obtain from moraine boulders with specified geomorphic histories, using Monte Carlo methods. We expand on pioneering modeling efforts to address this problem by placing these models into a common framework. We also evaluate the sensitivity of the models to changes in their input parameters. The sensitivity tests show that moraine degradation consistently produces left-skewed distributions of exposure dates; that is, the distributions have long tails toward the young end of the distribution. In contrast, inheritance produces right-skewed distributions that have long tails toward the old side of the distribution. Given representative distributions from these two models, we can determine which methods of estimating moraine ages are most successful in recovering the correct age for test cases where this value is known. The mean is a poor estimator of moraine age for data sets drawn from skewed parent distributions, and excluding outliers before calculating the mean does not improve this mismatch. The extreme estimators (youngest date and oldest date) perform well under specific circumstances, but fail in other cases. We suggest a simple estimator that uses the skewnesses of individual data sets to determine whether the youngest date, mean, or oldest date will provide the best estimate of moraine age. Although this method is perhaps the most globally robust of the estimators we tested, it sometimes fails spectacularly. The failure of simple methods to provide accurate estimates of moraine age points toward a need for more sophisticated statistical treatments. We present improved methods for estimating moraine ages in a companion paper.

scholarly journals An Algorithm for the Removal of Cosmic Ray Artifacts in Spectral Data Sets

2019 ◽  
Vol 73 (8) ◽  
pp. 893-901
Author(s):  
Sinead J. Barton ◽  
Bryan M. Hennelly
Keyword(s):  
Cosmic Ray ◽  
Data Sets ◽  
Biological Cells ◽  
Statistical Classification ◽  
Signal To Noise ◽  
Multivariate Statistical ◽  
Data Set ◽  
Artefact Removal ◽  
Single Capture ◽  
Acquisition Method

Cosmic ray artifacts may be present in all photo-electric readout systems. In spectroscopy, they present as random unidirectional sharp spikes that distort spectra and may have an affect on post-processing, possibly affecting the results of multivariate statistical classification. A number of methods have previously been proposed to remove cosmic ray artifacts from spectra but the goal of removing the artifacts while making no other change to the underlying spectrum is challenging. One of the most successful and commonly applied methods for the removal of comic ray artifacts involves the capture of two sequential spectra that are compared in order to identify spikes. The disadvantage of this approach is that at least two recordings are necessary, which may be problematic for dynamically changing spectra, and which can reduce the signal-to-noise (S/N) ratio when compared with a single recording of equivalent duration due to the inclusion of two instances of read noise. In this paper, a cosmic ray artefact removal algorithm is proposed that works in a similar way to the double acquisition method but requires only a single capture, so long as a data set of similar spectra is available. The method employs normalized covariance in order to identify a similar spectrum in the data set, from which a direct comparison reveals the presence of cosmic ray artifacts, which are then replaced with the corresponding values from the matching spectrum. The advantage of the proposed method over the double acquisition method is investigated in the context of the S/N ratio and is applied to various data sets of Raman spectra recorded from biological cells.

scholarly journals Ice thinning on nunataks during the glacial to interglacial transition in the Antarctic Peninsula region according to Cosmic-Ray Exposure dating: Evidence and uncertainties

2021 ◽  
Vol 264 ◽  
pp. 107029
Author(s):  
José M. Fernández-Fernández ◽  
Marc Oliva ◽  
David Palacios ◽  
Julia Garcia-Oteyza ◽  
Francisco J. Navarro ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Cosmic Ray ◽  
Exposure Dating ◽  
The Antarctic

scholarly journals Toward continental hydrologic–hydrodynamic modeling in South America

2018 ◽  
Vol 22 (9) ◽  
pp. 4815-4842 ◽  
Author(s):  
Vinícius A. Siqueira ◽  
Rodrigo C. D. Paiva ◽  
Ayan S. Fleischmann ◽  
Fernando M. Fan ◽  
Anderson L. Ruhoff ◽  
...  
Keyword(s):  
South America ◽  
Land Surface ◽  
River Discharge ◽  
Hydrological Modeling ◽  
Water Levels ◽  
Scale Model ◽  
Global Models ◽  
Discharge Data ◽  
Continental Scale ◽  
Terrestrial Water

Abstract. Providing reliable estimates of streamflow and hydrological fluxes is a major challenge for water resources management over national and transnational basins in South America. Global hydrological models and land surface models are a possible solution to simulate the terrestrial water cycle at the continental scale, but issues about parameterization and limitations in representing lowland river systems can place constraints on these models to meet local needs. In an attempt to overcome such limitations, we extended a regional, fully coupled hydrologic–hydrodynamic model (MGB; Modelo hidrológico de Grandes Bacias) to the continental domain of South America and assessed its performance using daily river discharge, water levels from independent sources (in situ, satellite altimetry), estimates of terrestrial water storage (TWS) and evapotranspiration (ET) from remote sensing and other available global datasets. In addition, river discharge was compared with outputs from global models acquired through the eartH2Observe project (HTESSEL/CaMa-Flood, LISFLOOD and WaterGAP3), providing the first cross-scale assessment (regional/continental  ×  global models) that makes use of spatially distributed, daily discharge data. A satisfactory representation of discharge and water levels was obtained (Nash–Sutcliffe efficiency, NSE > 0.6 in 55 % of the cases) and the continental model was able to capture patterns of seasonality and magnitude of TWS and ET, especially over the largest basins of South America. After the comparison with global models, we found that it is possible to obtain considerable improvement on daily river discharge, even by using current global forcing data, just by combining parameterization and better routing physics based on regional experience. Issues about the potential sources of errors related to both global- and continental-scale modeling are discussed, as well as future directions for improving large-scale model applications in this continent. We hope that our study provides important insights to reduce the gap between global and regional hydrological modeling communities.

scholarly journals The hidden anatomy of paranasal sinuses reveals biogeographically distinct morphotypes in the nine-banded armadillo (Dasypus novemcinctus)

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3593 ◽  
Author(s):  
Guillaume Billet ◽  
Lionel Hautier ◽  
Benoit de Thoisy ◽  
Frédéric Delsuc
Keyword(s):  
South America ◽  
Paranasal Sinuses ◽  
Morphological Diversity ◽  
Distinct Species ◽  
Molecular Data ◽  
Morphological Data ◽  
Diagnostic Feature ◽  
Guiana Shield ◽  
Diagnostic Features ◽  
Continental Scale

BackgroundWith their Pan-American distribution, long-nosed armadillos (genusDasypus) constitute an understudied model for Neotropical biogeography. This genus currently comprises seven recognized species, the nine-banded armadillo (D. novemcinctus) having the widest distribution ranging from Northern Argentina to the South-Eastern US. With their broad diversity of habitats, nine-banded armadillos provide a useful model to explore the effects of climatic and biogeographic events on morphological diversity at a continental scale.MethodsBased on a sample of 136 skulls ofDasypusspp. belonging to six species, including 112 specimens identified asD. novemcinctus, we studied the diversity and pattern of variation of paranasal cavities, which were reconstructed virtually using µCT-scanning or observed through bone transparency.ResultsOur qualitative analyses of paranasal sinuses and recesses successfully retrieved a taxonomic differentiation between the traditional speciesD. kappleri,D. pilosusandD. novemcinctusbut failed to recover diagnostic features between the disputed and morphologically similarD. septemcinctusandD. hybridus. Most interestingly, the high variation detected in our large sample ofD. novemcinctusshowed a clear geographical patterning, with the recognition of three well-separated morphotypes: one ranging from North and Central America and parts of northern South America west of the Andes, one distributed across the Amazonian Basin and central South America, and one restricted to the Guiana Shield.DiscussionThe question as to whether these paranasal morphotypes may represent previously unrecognized species is to be evaluated through a thorough revision of theDasypusspecies complex integrating molecular and morphological data. Remarkably, our recognition of a distinct morphotype in the Guiana Shield area is congruent with the recent discovery of a divergent mitogenomic lineage in French Guiana. The inflation of the second medialmost pair of caudal frontal sinuses constitutes an unexpected morphological diagnostic feature for this potentially distinct species. Our results demonstrate the benefits of studying overlooked internal morphological structures in supposedly cryptic species revealed by molecular data. It also illustrates the under-exploited potential of the highly variable paranasal sinuses of armadillos for systematic studies.

scholarly journals Age determination of common bottlenose dolphins (Tursiops truncatus) using dental radiography pulp:tooth area ratio measurements

PLoS ONE ◽  
2020 ◽  
Vol 15 (11) ◽  
pp. e0242273
Author(s):  
Jean M. Herrman ◽  
Jeanine S. Morey ◽  
Ryan Takeshita ◽  
Sylvain De Guise ◽  
Randall S. Wells ◽  
...  
Keyword(s):  
Life Histories ◽  
Marine Mammals ◽  
Bottlenose Dolphins ◽  
Age Determination ◽  
Area Ratio ◽  
Dental Radiography ◽  
Ratio Method ◽  
Data Sets ◽  
Photo Identification ◽  
Development And Validation

Age is an important parameter to better understand wildlife populations, and is especially relevant for interpreting data for fecundity, health, and survival assessments. Estimating ages for marine mammals presents a particular challenge due to the environment they inhabit: accessibility is limited and, when temporarily restrained for assessment, the window of opportunity for data collection is relatively short. For wild dolphins, researchers have described a variety of age-determination techniques, but the gold-standard relies upon photo-identification to establish individual observational life histories from birth. However, there are few populations with such long-term data sets, therefore alternative techniques for age estimation are required for individual animals without a known birth period. While there are a variety of methods to estimate ages, each involves some combination of drawbacks, including a lack of precision across all ages, weeks-to-months of analysis time, logistical concerns for field applications, and/or novel techniques still in early development and validation. Here, we describe a non-invasive field technique to determine the age of small cetaceans using periapical dental radiography and subsequent measurement of pulp:tooth area ratios. The technique has been successfully applied for bottlenose dolphins briefly restrained during capture-release heath assessments in various locations in the Gulf of Mexico. Based on our comparisons of dental radiography data to life history ages, the pulp:tooth area ratio method can reliably provide same-day estimates for ages of dolphins up to about 10 years old.

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