QRC members lead and participate in a wide range of disciplinary and interdisciplinary research projects from the study of past earth climates and glaciations to shifts in the geographic distributions and evolution of vegetation and faunal communities, to the evolution and dispersals of the genus Homo and the increasing scales of human modification of earth environments through the Holocene. QRC provides a venue for meeting and collaborating with scholars across Quaternary disciplines. We are also fortunate to be able to provide seed funding and small grants for member research projects. We are especially happy to support grad student and junior scholar research activities, much of which leads to larger, external funding from agencies like the National Science Foundation.
Applications of an in-situ optical surface exposure dating technique on glacial erratic quartzites from the Columbia Basin and Scotland
Abstract: Optically stimulated luminescence (OSL) depth profiling utilizes an OSL-at-depth signal to extrapolate an exposure age from a rock’s surface. The method offers the ability to date a variety of both geologically and archaeologically significant rock, artifact, and building surfaces exposed up to the last 100,000 years using only a few centimeters of the sample subsurface. However, poorly generalized techniques are commonly used for determining bleaching and attenuation variables for the OSL depth profiling equation, most commonly the use of a non in-situ proximal rock sample to derive bleaching and attenuation parameters. These tend to produce inconsistent ages among similarly sourced samples. This proposal tests a modified technique aiming to correct depth profiling method practices. First, a new depth profiling procedure using controlled exposure experiments will be tested on quartzite rocks with the aim of reliably determining bleaching and attenuation variables directly from the rock surface of interest. Upon success of in-lab testing, the procedure will be applied to quartzite rock surfaces of known ages at Lane Mountain Quarry (Valley, Washington) and from studied deglaciation surfaces in northwest Scotland to ensure that accurate variables and dates are derivable. Further, surfaces from erratic quartzites from the Foothills Erratics Train in Alberta, important for the issue of the initial settlement of the Americas, will be dated using the procedure and compared to independent dating sources. To address potential inconsistencies found between ages from using the new procedure, longitudinal core profiles of OSL intensity will be imaged to identify varied zones of luminescence bleaching. Depth profiling calculations can then be altered to accommodate for piecewise attenuation-depth properties and refine procedural accuracy.
Addressing Rock Artifact Erosion in Mount Diablo State Park, California
Abstract: Artifact bearing sandstone surfaces located in Mount Diablo State Park, California face vandalization and surface degradation from graffiti, foot traffic, grazing, and other anthropogenic influences in addition to broader, longer term effects from Holocene scale microclimatic and environmental changes in the region. Artifacts in the park are currently protected under vandalization clauses, yet a surface stability study may assist in the development of and support toward more effective protection efforts by providing a clearer understanding of the erosive mechanisms altering artifact surfaces. Thus, it is desired from the Mount Diablo community to conduct a quantified, millennial scale study of artifact surface stability. This project attempts to address this desire by selecting four non-artifact sandstone surfaces from two artifact bearing campground sites in the park and analyzing their surface stability histories using a combination of multidisciplinary procedures. Optically stimulated luminescence (OSL) depth profiling will be conducted on extracted rock cores from the sandstone surfaces to produce calculated steady-state centennial to millennial scale surface erosion rates and provide relative surface stability histories of the same scale using luminescence depth curves that document variations in surface luminescence though time. Steady-state erosion rates from sandstone surfaces will also be calculated with 10Be surface data using CRONUS, and then compared with OSL results to identify potential differences with each measurement’s interactions to surface variables (lichens, moss, mineralogy, etc.). Millennial scale probabilistic rock surface spalling analyses also using 10Be data will be incorporated in the analysis to determine possible sequences of surface re-zeroing events that may influence CRONUS and OSL data. Indications of artifact surface erosion influenced by local climatic changes and/or anthropogenic landscape alterations will be analyzed by connecting trends in luminescence attenuation, cosmogenic spalling, and erosion data to distinct historical and prehistorical variations in regional vegetation cover. To make these comparisons, pollen-derived landscape reconstruction algorithms (LRAs) that document regional Holocene vegetative cover through time will be conducted in the Mount Diablo region using pollen sampled from five regionally spaced soil cores within the region. Additional comparisons to historical data and geomorphic observations will also be made to observe direct anthropogenic influences on artifact surface erosion and the landscape. Through comparing millennial scale artifact surface erosion stability data to environmental, climatic and anthropogenic histories in the Mount Diablo region, primary agents and sequences of artifact erosion can be identified from our procedures, providing analytical support for park agendas that aim to mitigate identified erosive factors. The success of this analysis in Mount Diablo can justify the method’s use at other rock artifact bearing sites.
Assessing Rock Surface Erosion Using Cosmogenic Isotopes and Optically Simulated Luminescence Depth Profiling in Petroglyph Contexts
Abstract: Petroglyphs, rock images created by the anthropogenic removal of material on a rock surface, are subjected to various natural and anthropogenic conditions that cause them to degrade over time and eventually disappear. Accurate quantification of the erosive impacts on petroglyph surfaces and identifying and understanding the environmental factors of erosion can be essential for planning preservation strategies.
A multidisciplinary scientific analysis utilizing geochemical and paleoenvironmental analysis methods at petroglyph bearing sites will be conducted at Henry W. Coe State Park, located in the Diablo Range of Northern California, to assess the history of and factors contributing to rock surface erosion. This analysis will primarily focus on utilizing concentrations of cosmogenic isotope 10Be from rock surface samples in proximity to petroglyphs to establish proximal rock erosion rates to petroglyph surfaces. Using the data, erosion episodicity (whether spallated, gradual, etc.) may also be determined via applied modeling. Cosmogenic erosion data will be co-analyzed with optically simulated luminescence (OSL) depth profiling analyses on similar/same rock surfaces to decipher any unique environmental settings that may impact each method’s results. Providing a cosmogenic-OSL dual analysis also helps introduce cosmogenic isotopes to archaeological study in a way that easily relates cosmogenic isotopic methods to OSL, making it easier to understand and incorporate cosmogenic isotopes in future archaeological work. The same can be said for Earth scientists interested in rock erosion analyses yet are less familiar with OSL, which is an underutilized tool in the Earth Sciences yet hosts great potential for surface process study. No samples directly from petroglyph surfaces will be taken. Additional paleoenvironmental analyses of the petroglyph region will also be carried out, utilizing a multitude of methods such as palynology, rock-vegetation interaction analyses, Landscape Reconstruction Algorithms (LRA), and other relevant paleoenvironmental methods that will be uniquely applicable to the site. Once gathered, a comparative analysis utilizing the quantitative erosion data and paleoenvironmental records will then be conducted to provide a better understanding of the erosive history of petroglyph surfaces and help identify the environmental factors affecting erosion rates. This knowledge may offer needed data for communities and parks wanting to optimize the preservation of their material heritage.
Termite geoarchaelogy at Madjedbebe, Northern Australia
Abstract: Madjedbebe (Northern Territory, Australia) is an important location for understanding human evolution. We recently presented new ages of 65 ka for human occupation at Madjedbebe (Clarkson, et al. 2017). These new ages have significance for the arrival humans in Australia, the dispersal of modern humans out of Africa, and the subsequent interactions of modern humans with Neanderthals and Denisovans. However, many factors can influence the relationship between the archaeological material and the dated samples. This project is a geoarchaeological study to improve our understanding of archaeological site formation processes at this important site. We will use three-dimensional shape and size statistics to study the larger size fraction of the sedimentary deposit – cobbles – to test previously posited hypotheses about the role of termites in formation of the deposit at Madjedbebe.
Abstract: Petroglyphs, rock images created by the anthropogenic removal of material on a rock surface, are subjected to various natural and anthropogenic conditions that cause them to degrade over time and eventually disappear. Accurate quantification of the erosive impacts on petroglyph surfaces and identifying and understanding the environmental factors of erosion can be essential for planning preservation strategies.