A late Holocene onset of Aboriginal burning in southeastern Australia

The extent to which Aboriginal Australians used fire to modify their environment has been debated for decades and is generally based on charcoal and pollen records rather than landscape responses to land-use change. Here we investigate the sensitivity of in-situ–produced 10Be, an isotope commonly used in geomorphological contexts, to anthropogenic perturbations in the southeastern Australian Tablelands. Comparing 10Be-derived erosion rates from fluvial sediment (8.7 ± 0.9 mm k.y.–1; 1 standard error, SE; n = 11) and rock outcrops (5.3 ± 1.4 mm k.y.–1; 1 SE; n = 6) confirms that landscape lowering rates integrating over 104–105 yr are consistent with rates previously derived from studies integrating over 104 to >107 yr. We then model an expected 10Be inventory in fluvial sediment if background erosion rates were perturbed by a low-intensity, high-frequency Aboriginal burning regime. When we run the model using the average erosion rate derived from 10Be in fluvial sediment (8.7 mm k.y.–1), measured and modeled 10Be concentrations overlap between ca. 3 ka and 1 ka. Our modeling is consistent with intensified Aboriginal use of fire in the late Holocene, a time when Aboriginal population growth is widely recognized

Combining bulk sediment OSL and meteoric 10 Be fingerprinting techniques to identify gully initiation sites and erosion depths

Deep erosional gullies dissect landscapes around the world. Existing erosion models focus on predicting where gullies might begin to erode, but identifying where existing gullies were initiated and under what conditions is difficult, especially when historical records are unavailable. Here we outline a new approach for fingerprinting alluvium and tracing it back to its source by combining bulk sediment optically stimulated luminescence (bulk OSL) and meteoric 10Be (10Bem) measurements made on gully-derived alluvium samples. In doing so, we identify where gully erosion was initiated and infer the conditions under which such erosion occurred. As both 10Bem and bulk OSL data have distinctive depth profiles in different uneroded and depositional settings, we are able to identify the likely incision depths in potential alluvium source areas. We demonstrate our technique at Birchams Creek in the southeastern Australian Tablelands—a well-studied and recent example of gully incision that exemplifies a regional landscape transition from unchanneled swampy meadow wetlands to gully incision and subsequent wetland burial by post-European settlement alluvium. We find that such historic alluvium was derived from a shallow erosion of valley fill upstream of former swampy meadows and was deposited down the center of the valley. Incision likely followed catchment deforestation and the introduction of livestock, which overgrazed and congregated in valley bottoms in the early 20th century during a period of drought. As a result, severe gully erosion was likely initiated in localized, compacted, and oversteepened reaches of the valley bottom

Regolith production and transport at the Susquehanna Shale Hills Critical Zone Observatory, Part 2: Insights from meteoric 10Be

Regolith-mantled hillslopes are ubiquitous features of most temperate landscapes, and their morphology reflects the climatically, biologically, and tectonically mediated interplay between regolith production and downslope transport. Despite intensive research, few studies have quantified both of these mass fluxes in the same field site. Here we present an analysis of 87 meteoric 10Be measurements from regolith and bedrock within the Susquehanna Shale Hills Critical Zone Observatory (SSHO), in central Pennsylvania. Meteoric 10Be concentrations in bulk regolith samples (n=73) decrease with regolith depth. Comparison of hillslope meteoric 10Be inventories with analyses of rock chip samples (n=14) from a 24 m bedrock core confirms that >80% of the total inventory is retained in the regolith. The systematic downslope increase of meteoric 10Be inventories observed at SSHO is consistent with 10Be accumulation in slowly creeping regolith (∼ 0.2 cm yr-1). Regolith flux inferred from meteoric 10Be varies linearly with topographic gradient (determined from high-resolution light detection and ranging-based topography) along the upper portions of hillslopes at SSHO. However, regolith flux appears to depend on the product of gradient and regolith depth where regolith is thick, near the base of hillslopes. Meteoric 10Be inventories at the north and south ridgetops indicate minimum regolith residence times of 10.5 ± 3.7 and 9.1 ± 2.9 ky, respectively, similar to residence times inferred from U-series isotopes in Ma et al. (2013). The combination of our results with U-series-derived regolith production rates implies that regolith production and erosion rates are similar to within a factor of two on SSHO hillcrests. ©2013. American Geophysical Union. All Rights Reserved

The surface density profile of NGC 6388: a good candidate for harboring an intermediate-mass black hole

We have used a combination of high resolution (HST ACS-HRC, ACS-WFC, and WFPC2) and wide-field (ESO-WFI) observations of the galactic globular cluster NGC 6388 to derive its center of gravity, projected density profile, and central surface brightness profile. While the overall projected profiles are well fit by a King model with intermediate concentration (c=1.8) and sizable core radius (rc=7"), a significant power law (with slope \alpha=-0.2) deviation from a flat core behavior has been detected within the inner 1 arcsecond. These properties suggest the presence of a central intermediate mass black hole. The observed profiles are well reproduced by a multi-mass isotropic, spherical model including a black hole with a mass of ~5.7x10^3 Msol.Comment: ApJ Letter in pres

A new stylolite classification scheme to estimate compaction and local permeability variations

This study was carried out within the framework of DGMK (German Society for Petroleum and Coal Science and Technology) research project 718 “Mineral Vein Dynamics Modeling”, which is funded by the companies ExxonMobil Production Deutschland GmbH, GDF SUEZ E&P Deutschland GmbH, DEA Deutsche Erdoel AG and Wintershall Holding GmbH, within the basic research program of the WEG Wirtschaftsverband Erdoel- und Erdgasgewinnung e.V. We thank the companies for their financial support and their permission to publish these results. This work has received funding from the European Union's Seventh Framework Programme for research, technological development and demonstration under grant agreement no 31688. The Zechstein data were collected with the help of Simon Gast. We thank Jean-Pierre Gratier and an anonymous reviewer for their comments that improved an earlier version of the manuscript.Peer reviewedPostprin

Implementation of Unclassified Controlled Nuclear Information guidelines for fixed-site safeguards and security (FSSS) at Los Alamos National Laboratory

Unclassified Controlled Nuclear Information (UCNI) is one type of sensitive information that DOE employees, including computer users, must now identify and protect. Guidelines to identify information as UCNI are gradually being put in place. The publication of Unclassified Controlled Nuclear Information Topical Guideline for Fixed-Site Safeguards and Security, TG-FSSS-1, is a major step in the development of UCNI guidelines. This DOE published guide cuts across and addresses many different programmatic areas including automated data processing. Our local guideline, Los Alamos National Laboratory Unclassified Controlled Nuclear Information Guideline for Fixed-Site Safeguards and Security, IG-LAFSSS-1, is based on TG-FSSS-1. In this paper, I plan to discuss the background of UCNI, the definition of UCNI, information that qualifies as UCNI, the consequences of information being UCNI, the development of UCNI guidelines, TG-FSSS-1 and IG-LAFSSS-1, the relationship of UCNI to classification, and the implementation of the IG-LAFSSS-1 at Los Alamos

Downscale cascades in tracer transport test cases: an intercomparison of the dynamical cores in the Community Atmosphere Model CAM5

The accurate modeling of cascades to unresolved scales is an important part of the tracer transport component of dynamical cores of weather and climate models. This paper aims to investigate the ability of the advection schemes in the National Center for Atmospheric Research's Community Atmosphere Model version 5 (CAM5) to model this cascade. In order to quantify the effects of the different advection schemes in CAM5, four two-dimensional tracer transport test cases are presented. Three of the tests stretch the tracer below the scale of coarse resolution grids to ensure the downscale cascade of tracer variance. These results are compared with a high resolution reference solution, which is simulated on a resolution fine enough to resolve the tracer during the test. The fourth test has two separate flow cells, and is designed so that any tracer in the western hemisphere should not pass into the eastern hemisphere. This is to test whether the diffusion in transport schemes, often in the form of explicit hyper-diffusion terms or implicit through monotonic limiters, contains unphysical mixing. <br><br> An intercomparison of three of the dynamical cores of the National Center for Atmospheric Research's Community Atmosphere Model version 5 is performed. The results show that the finite-volume (CAM-FV) and spectral element (CAM-SE) dynamical cores model the downscale cascade of tracer variance better than the semi-Lagrangian transport scheme of the Eulerian spectral transform core (CAM-EUL). Each scheme tested produces unphysical mass in the eastern hemisphere of the separate cells test