Using ³⁶Cl exposure dating to date mass movement and assess land stability on the Nicholas Range, Tasmania

Detailed mapping of dolerite slope deposits overlying sedimentary Triassic rocks on the northern slopes of the Nicholas Range in northeastern Tasmania has revealed an extensive mass movement complex. Landforms north of the summit plateau of the Nicholas Range include the following: (1) a cliff of dolerite columns with associated scree slopes at its base; (2) a topple landscape consisting of several topples that have fallen in a north-easterly direction; (3) a ripple landscape consisting of a series of long boulder ridges aligned approximately east-west. Exposure dates were obtained for three large boulders (collapsed dolerite columns) from a ridge within the ripple landscape. The two youngest dates gave a mean age of 52.1 ± 1.9 ka using36Cl. This is the estimated age for collapse of the dated columns from the cliff face c. 750 m to the south. Boulder ages and landscape morphology indicate that the ripple landscape developed by physical and chemical degradation and concurrent northern displacement of topples over a slip plane formed at the contact between dolerite colluvium and underlying Triassic sedimentary rocks. There is no evidence of movement today, other than localised debris flows associated with knickpoints in streams, and it is deduced that movement on the slip plane occurred under a cooler climate than that prevailing today, possibly under the influence of melting of winter snow during the last glacial cycle. As there is no evidence of significant recent mass movement and forests in the area are likely to have experienced many stand-destroying forest fires in the Holocene, forest harvest is not considered to pose a risk to landscape stability

Production of 21 Ne in depth-profiled olivine from a 54 Ma basalt sequence, Eastern Highlands (37° S), Australia

In this study we investigate the cosmogenic neon component in olivine samples from a vertical profile in order to quantify muogenic 21Ne production in this mineral. Samples were collected from an 11 m thick Eocene basalt profile in the Eastern Highlands of southeastern Australia. An eruption age of 54.15 ± 0.36 Ma (2σ) was determined from 40Ar/39Ar step-heating experiments (n = 6) on three whole-rock samples. A 36Cl profile on the section indicated an apparent steady state erosion rate of 4.7 ± 0.5 m Ma−1. The eruption age was used to calculate in situ produced radiogenic 4He and nucleogenic 3He and 21Ne concentrations in olivine. Olivine mineral separates (n = 4), extracted from the upper two metres of the studied profile, reveal cosmogenic 21Ne concentrations that attenuate exponentially with depth. However, olivine (Fo68) extracted from below 2 m does not contain discernible 21Ne aside from magmatic and nucleogenic components, with the exception of one sample that apparently contained equal proportions of nucleogenic and muogenic neon. Modelling results suggest a muogenic neon sea-level high-latitude production rate of 0.02 ± 0.04 to 0.9 ± 1.3 atoms g−1 a−1 (1σ), or <2.5% of spallogenic cosmogenic 21Ne production at Earth’s surface. These data support a key implicit assumption in the literature that accumulation of muogenic 21Ne in olivine in surface samples is likely to be negligible/minimal compared to spallogenic 21Ne

Geospatial simulations of airborne ice-penetrating radar surveying reveal elevation under-measurement bias for ice-sheet bed topography

© The Author(s), 2020. Published by Cambridge University Press. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/).Airborne radio-echo sounding (RES) surveys are widely used to measure ice-sheet bed topography. Measuring bed topography as accurately and widely as possible is of critical importance to modelling ice dynamics and hence to constraining better future ice response to climate change. Measurement accuracy of RES surveys is influenced both by the geometry of bed topography and the survey design. Here we develop a novel approach for simulating RES surveys over glaciated terrain, to quantify the sensitivity of derived bed elevation to topographic geometry. Furthermore, we investigate how measurement errors influence the quantification of glacial valley geometry. We find a negative bias across RES measurements, where off-nadir return measurement error is typically -1.8 ± 11.6 m. Topographic highlands are under-measured an order of magnitude more than lowlands. Consequently, valley depth and cross-sectional area are largely under-estimated. While overall estimates of ice thickness are likely too high, we find large glacier valley cross-sectional area to be under-estimated by -2.8 ± 18.1%. Therefore, estimates of ice flux through large outlet glaciers are likely too low when this effect is not taken into account. Additionally, bed mismeasurements potentially impact our appreciation of outlet-glacier stability.Peer reviewedFinal Published versio

Topographic variation in soil erosion and accumulation determined with meteoric ¹⁰Be:Soil erosion and accumulation determined with meteoric 10Be

Understanding natural soil redistribution processes is essential for measuring the anthropogenic impact on landscapes. Although meteoric beryllium-10 (10Be) has been used to determine erosion processes within the Pleistocene and Holocene, fewer studies have used the isotope to investigate the transport and accumulation of the resulting sediment. Here we use meteoric 10Be in hilltop and valley site soil profiles to determine sediment erosion and deposition processes in the Christina River Basin (Pennsylvania, USA). The data indicate natural erosion rates of 14 to 21 mm 10−3yr and soil ages of 26 000 to 57 000 years in hilltop sites. Furthermore, valley sites indicate an alteration in sediment supply due to climate change (from the Pleistocene to the Holocene) within the last 60 000 years and sediment deposition of at least 0.5-2 m during the Wisconsinan glaciation. The change in soil erosion rate was most likely induced by changes in geomorphic processes; probably solifluction and slope wash during the cold period, when ice advanced into the mid latitudes of North America. This study shows the value of using meteoric10Be to determine sediment accumulation within the Quaternary and quantifies major soil redistribution occurred under natural conditions in this region

Health Professional Training and Capacity Strengthening Through International Academic Partnerships: The First Five Years of the Human Resources for Health Program in Rwanda

Abstract Background: The Rwanda Human Resources for Health Program (HRH Program) is a 7-year (2012-2019) health professional training initiative led by the Government of Rwanda with the goals of training a large, diverse, and competent health workforce and strengthening the capacity of academic institutions in Rwanda. Methods: The data for this organizational case study was collected through official reports from the Rwanda Ministry of Health (MoH) and 22 participating US academic institutions, databases from the MoH and the College of Medicine and Health Sciences (CMHS) in Rwanda, and surveys completed by the co-authors. Results: In the first 5 years of the HRH Program, a consortium of US academic institutions has deployed an average of 99 visiting faculty per year to support 22 training programs, which are on track to graduate almost 4600 students by 2019. The HRH Program has also built capacity within the CMHS by promoting the recruitment of Rwandan faculty and the establishment of additional partnerships and collaborations with the US academic institutions. Conclusion: The milestones achieved by the HRH Program have been substantial although some challenges persist. These challenges include adequately supporting the visiting faculty; pairing them with Rwandan faculty (twinning); ensuring strong communication and coordination among stakeholders; addressing mismatches in priorities between donors and implementers; the execution of a sustainability strategy; and the decision by one of the donors not to renew funding beyond March 2017. Over the next 2 academic years, it is critical for the sustainability of the 22 training programs supported by the HRH Program that the health-related Schools at the CMHS significantly scale up recruitment of new Rwandan faculty. The HRH Program can serve as a model for other training initiatives implemented in countries affected by a severe shortage of health professionals

Holocene hydrologic variability in temperate southeastern Australia: An example from Lake George, New South Wales

Lake George is one of the largest freshwater lakes in Australia when full, and provides one of the most complete records of Quaternary sedimentation in the southeastern part of the continent. The lake is currently ephemeral, but sediments within the basin preserve evidence of multiple permanent and dry lake conditions in the past. We present an optically stimulated luminescence (OSL) chronology of recent lake shoreline sediments in order to reconstruct Holocene hydrologic variability at Lake George, providing past climatic context for the presently ephemeral lake conditions. The OSL chronology indicates three distinct periods of permanent lake conditions up to 15-18 m depth over the Holocene period, at approximately 10-8, 6-2.4 and 0.7-0.3 ka, with lower lake levels occurring in between those events. There appears to be a trend towards lake regression over this period despite relatively recent high lake levels. The chronology is broadly synchronous with comparable records of Holocene climatic variability across southeastern Australia. We also investigate the intrinsic luminescence characteristics of different sediment types as diagnostic tools, but these appear not to be appropriate in this context or form