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Measurement of detrital zircon U-Pb ages has become the method of choice for single crystal--based investigations of provenance for both modern and ancient sediments. Recent studies, however, demonstrated the failure of zircon to record major tectonic events in source terranes, revealing the need for a more robust provenance methodology. A direct comparison between the utility of crystallization ages of detrital zircon and monazite as provenance indicators has been made using modern river alluvium derived from known sources. While detrital zircon does not fully record the multiple coilisional phases that are the hallmark of the Appalachian orogen, detrital monazite accurately records all the major tectonic events. The physical and petrogenetic differences between zircon and monazite are the primary factors for differing detrital age spectra. Zircon, owing to its extreme refractory nature, skews detrital age spectra toward older ages and limits its ability to record low-grade thermotectonic events in orogens. Monazite recrystallizes over a broader range of metamorphic conditions than does zircon. Consequently, monazite has the potential to record metamorphic events that might otherwise be absent from the detrital zircon record, thus providing a more accurate record of source terranes in regions characterized by moderate thermal events. doi: 10.1130/G30265.1

Aluminum (Al) powder is commonly encountered in improvised explosive devices (IEDs) as a metallic fuel due to its availability and low cost. Although available commercially in powder form, amateur bomb‐makers also produce their own Al powder via simple methods found online. In order to provide investigative leads and forensic intelligence, it is important to evaluate not only the composition of homemade devices, but also to distinguish between the various forms of Al powder they contain. To achieve this goal, a method using automated microscopy in combination with statistical techniques has been demonstrated to have the potential to provide source discrimination and investigative leads in source attribution of Al powders in IEDs. The present research refined this method and investigated 59 industrially and amateurly produced Al powder sources with seven subsamples per source using two traditional linear discriminant analyses (LDA), one with a standard data split for training and testing, and another using leave‐one‐out cross‐validation. Averaging the classification accuracies for the two LDA‐based analyses, LDA has the ability to correctly classify 59.26%, 83.35%, and 80.69% of the samples based on their powder source, type, and production method, respectively. This classification accuracy represents a 3407%, 317%, and 61.38% increase in accuracy from random class assignment, respectively. Further, in most instances of incorrect data attribution to a particular source, the subsample has been misidentified with another sample of the same powder type or production method. [ABSTRACT FROM AUTHOR]

There is a serious issue within the forensic science community, which even extends outside of the field. The role of the scientist in the investigation of crime has been increasingly confined to the laboratory, which has been accompanied by the conflation of the terms forensic science and criminalistics. This unfortunate situation has been festering for years. To make matters worse, the era of the proactive, problem‐defining, criminalist (generalist) is waning, and possibly over. Present‐day "criminalists" are treated as little more than reactive, protocol‐constrained, laboratory technicians, with few, if any, consequential crime scene roles. In most cases, these "criminalists" merely respond to routine requests from prosecutors and police. The absence of science at the front end of forensic investigations, i.e., the scene, has resulted in biased, ineffective, inefficient, and/or erroneous outcomes with immediate and long‐term societal impacts. To disentangle this imbroglio, we propose the use of another term, traceology, which has seen limited use worldwide except in the field of archaeology. With respect to criminalistics, this term has been previously proposed by Margot (20–21). Traceology is an historical science, dealing with the examination, analysis, and scientific interpretation of event traces (signs or remnants) of earlier activities. In this commentary, we define and redefine familiar, but ambiguous, terms and concepts with the hope of recapturing the essence of criminalistics (32), which we suggest is best termed traceology. [ABSTRACT FROM AUTHOR]

Aluminum (Al) powders are commonly used in improvised explosive devices as metallic fuels, a component of explosive mixtures. These powders can be obtained readily from industrial‐scale and consumer products, and produced using unsophisticated "kitchen chemistry" techniques. This research demonstrates the potential of automated particle micromorphometry for comparisons between known source and questioned Al powders recovered from IEDs, as well as for insight into the method of Al powder manufacture. Al powder samples were obtained from legitimate manufacturers, and 56 samples were produced "in‐house" from Al‐containing spray paints and ball‐milled Al foils. Transmitted light microscope images of Al powder particles were acquired using an automated stage with automated z‐focus; 17 size and shape parameters were measured for all particles. Approximately 37,000–2,500,000 particles/sample were analyzed using an open‐source statistical package with customized code. Dimensionality reduction was required for processing the large datasets: eight of the 17 measured variables were selected based on inspection of the correlation matrix. Data from four subsamples from each of the 56 samples produced using "in‐house" methods were analyzed using ANOVA to assess the within‐ and between‐sample variation. High within‐sample variation was noted; however, ANOVA and post‐hoc Tukey's honestly significant difference (HSD) tests demonstrated that the between‐sample variation was substantially larger than the within‐sample variation. Each sample could be differentiated from all other samples in the test set. Future experiments will focus on ways to reduce the within‐sample variation, and additional statistical and microanalytical methods to classify sources and confidently constrain the method of Al powder manufacture. [ABSTRACT FROM AUTHOR]

A study was undertaken using nonhuman mammal specimens to better understand environmental influences on postmortem hair root band (PMRB) formation and to see whether PMRBs would occur in nonhuman mammal hairs in a similar fashion to human hairs. Carcasses from surrounding roadways were the primary source of specimens for this study, augmented by donated deceased domestic pets. Sections of pelt from each specimen were placed in controlled environmental conditions while the remainder of the carcass was left in a secure outdoor setting. Hair samples were collected daily from outdoor and control specimens and examined for evidence of PMRBs. Several environmental factors were also recorded on a daily basis. Results demonstrate PMRBs can occur in nonhuman mammal hairs, and they have microscopic characteristics similar to human PMRBs. Factors found to correlate with PMRB formation include postmortem interval, temperature, pH, and the formation and subsequent volatilization of ammonia from the surrounding tissue. [ABSTRACT FROM AUTHOR]

The advent of new procedures for the rapid collection of large amounts of detrital zircon age data has created significant challenges to the representation, quantitative interpretation, and analysis of these results. Principal among these is the development of the most efficient and informative methods to accurately present and quantitatively compare numerous age data from large numbers of samples in a statistically valid, geologically meaningful, and easily assessable manner. Many detrital zircon studies have adopted a subjective-graphic approach to these tasks, primarily through the examination of vertically stacked probability density plots (PDPs). Although this methodology allows for quick visual assessment of changes in zircon age frequencies in space and/or time, it is fundamentally qualitative, and becomes rather impractical as numbers of analyses become large. More quantitative approaches to the comparison of PDPs (e.g., Kolmogorov-Smirnov test and multi-dimensional scaling) have also become more popular, but are rather computationally intense. In order to examine degrees of sameness among detrital zircon age populations in geographic and/or stratigraphic contexts, we develop a "likeness" metric that quantifies the degree of overlap between pairs of PDPs. We compare this metric to several others that have been proposed previously, and then evaluate its usefulness in describing sourceto- sink changes in sample age populations by analyzing data from four published studies of detrital zircon age frequencies. Likeness among 26 Paleozoic samples from the Grand Canyon (southwestern United States) decreases with increasing stratigraphic separation, but stratigraphically contiguous sample likeness exhibits statistically insignificant upsection change. The degree to which these patterns are representative of other stratigraphic successions awaits further evaluation. Likenesses among 15 samples of modern fluvial sand from the Amazon River (South America), 11 stream samples from the French Broad River in the southern Appalachians (eastern United States), and 10 Quaternary coastal sand samples from eastern Australia decrease with increasing distance between samples; as might be expected, greater geographic disjunction results in greater dissimilarity. In contrast, likenesses among spatially contiguous fluvial and littoral sample ages all exhibit trends reflecting a greater down-system increase in likeness. These results suggest that sediment grain ages may exhibit increasing homogenization with transport in both fluvial and littoral systems. The extent to which these source-to-sink changes may characterize lateral variations in other sedimentary systems also awaits additional assessment. Nonetheless, each of these four examples demonstrates that the determination of sample-pair likenesses, and evaluation of their geographic and/or stratigraphic variation, serve to effectively highlight those aspects of differences in detrital zircon age frequencies that ultimately record the histories of geologic and geomorphic processes in both space and time. [ABSTRACT FROM AUTHOR]