OSL investigations at Hardisty, Alberta, Canada: Sections HD03, HD04 & HD05

This report is concerned with optically stimulated luminescence (OSL) investigations of a number of sediment stratigraphies in the Battle River Valley area, near Hardisty, east-central Alberta. Archaeological investigations in this region, led by Rob Wondrasek, have identified thousands of historical artefacts, including projectile points and lithic fragments indicative of occupation. Ken Munyikwa visited the archaeological sites at Hardisty in June 2014 and January 2015 to sample key units within the sediment stratigraphies for OSL dating. The sediments associated with the artefacts were appraised through five profiles, Hardisty-1 (HD01) to Hardisty-5 (HD05), comprised of 43 field-profiling and 14 dating samples. Profiles HD01 and HD02 were sampled in June 2014; and profiles HD03 through to HD05 in January 2015. The dating questions associated with these materials relate to the age of artefact-bearing horizon, through dating the enclosing sediments above and beneath the archaeological soil, it should be possible to provide terminus post quem (TPQ) and terminus ante quem (TAQ) on the age of the artefacts. The conventional quartz SAR OSL approach was examined as a potential method for providing the depositional ages of the sediment enclosing the artefacts. Luminescence profiling during fieldwork had revealed stratigraphically progressive IRSL and OSL signals, indicating sediment with dating potential. Dose rate estimates from these sediments were assessed using a combination of high resolution gamma spectrometry (HRGS) and thick source beta counting (TSBC), reconciled with each other, water contents and modelled micro-dosimetry. Where appropriate, the external gamma dose rates received at the position of the dating sample were reconstructed from the adjacent bulk gamma spectrometry samples, yielding wet gamma dose rates between 0.42 and 0.54 mGy a-1, which are comparable with those recorded at each sampling position. Equivalent doses were determined by OSL from 16-48 aliquots of quartz per sample (depending on quartz yields) using a single-aliquot-regenerative (SAR) approach. The material exhibited good OSL sensitivity and produced acceptable SAR internal quality control performance. Radial plotting methods revealed some heterogeneity in the equivalent dose distributions of each sample, indicating that each sample enclosed mixed-age materials, reflecting variable bleaching at deposition. The field profiles provide some measure of control on this. Luminescence ages were calculated using standard microdosimetric models, with uncertainties that combined measurement and fitting errors from the SAR analysis, all dose rate evaluation uncertainties, and allowance for the calibration uncertainties of the sources and reference materials. The quartz OSL ages reported here for the sand sequences at HD03 to HD05, contribute to the expanding catalogue of chronological data on the depositional sequences at Hardisty, and further, provide the means to assess the temporal and spatial distribution of artefacts across the site. The sediment chronologies established for each profile are internally and mutually coherent, spanning at HD03 from 7.3 ± 0.3 ka (SUTL2778) to 9.0 ± 0.5 ka (SUTL2780), at HD04 from 7.0 ± 0.3 ka (SUTL2781) to 8.3 ± 0.4 ka (SUTL2782), and at HD05 from 8.3 ± 0.5 ka (SUTL2783) to 9.6 ± 0.6 ka (SUTL2785). The field profile at HD05 reveals some complexity to its depositional history, with notable maxima and inversions in intensities from 150cm depth, potentially reflecting reworking and re-deposition of sediment within this sequence. TAQ for this phase of reworking is provided by the youngest unit examined in the profile, which at 7.5 ± 0.6 ka (SUTL2784), is consistent with the occupational phase recorded in the adjacent sections. The sediment chronologies established in this dating campaign, and in the 2014 campaign, are synchronous suggesting contemporaneous deposition across the site, and presumably, with local knowledge, scope for further age modelling including the use of Bayesian methods to refine the TAQ and TPQ age limits

Luminescence profiling of postglacial eolian dunes in central and northern Alberta using a portable OSL reader

My oral presentation at GEOHYDRO-2011 was at 11:00 am (Tues, Aug 30, 2011) in the session Quaternary Geology, Paleoenvironments and Geomorphology. After my power point presentation (30 slides) the floor was opened for questions. Colleagues who are doing similar geochronological dating work in Canada asked questions which essentially wanted to know about our methodological approaches and how they related to protocols they were using in their labs. In particular they wanted to know about the following: • what methods we use to normalize our samples (weight or irradiation) • what sources we use for irradiating our samples • if we have problems with signal contamination from feldspar when using post –IR blue-OSL stimulation with the portable OSL reader on bulk samples These were very constructive questions and, following my responses, I got some very interesting feedback. We will incorporate some of this feedback as we proceed with our research. Later during the conference I also had the opportunity to talk at great length with colleagues from the University of Quebec at Montreal who also have a luminescence dating lab. The exchanges we had where educative and we plan to continue with the interaction in future.Regular luminescence dating is a lengthy procedure that entails elaborate sample preparation as well as multiple measurements to arrive at an age of a given sample. In practice, not all samples that may appear datable in the field actually yield useful information in the lab. Consequently, because sample luminescence measurement is only carried out near the end of the dating procedure, a significant amount of time and resources could be expended on samples that ultimately produce no useful data. A technique that can be used to discriminate between samples that could potentially yield useful information and those that would not is luminescence profiling (Bishop et al., 2006; Burbidge et al., 2007; Sanderson and Murphy, 2010). Luminescence profiling does not necessarily provide an absolute age. Instead, it enables one to construct a profile that shows a variation of the luminescence signal with depth. The luminescence signal is dependent on variables such as the burial age and luminescence sensitivity of the sediment, as well as the local dose rates and level of bleaching experienced prior to burial. Where the burial age is the main variable, the luminescence profile could be seen as a proxy for the chronostratigraphy and it enables one to identify changes such as significant age differences between successive strata within a given section, or age variations across erosional contacts. Luminescence profiling measurements can be carried out rapidly in the lab or in the field using a portable OSL reader. Analysis can be done on bulk samples, negating the need to perform time consuming mineralogical separations. In this study, a portable OSL reader is employed to construct luminescence profiles of postglacial eolian dunes from selected sites in central and northern Alberta. In places, the dunes are underlain by glaciofluvial sands but it is often difficult to distinguish between the eolian deposits and the glaciofluvial sediments based on their physical appearances alone. Results from the study show that luminescence profiling can differentiate between the two types of deposits because of differences in their depositional ages and this enables the demarcation of the bases of the dunes. The identification of the dune bottom permits appropriately targeted sample collection for regular luminescence dating in order to constrain the timing of the initiation of eolian deposition in the region. Luminescence profiling is also used in this study to identify depositional breaks of extended duration within the eolian sequences. Session: Quaternary Paleoenvironment

The utility of portable optically stimulated luminescence (OSL) readers in providing temporal contexts in clastic depositional systems: opportunities in geomorphology

This outline summarizes a presentation I made on August 28, 2013 at the 8th International Conference on Geomorphology organized by the International Geomorphological Association at the Cite des Sciences et de l’Industrie in Paris, France. The presentation was titled “The utility of portable optically stimulated luminescence (OSL) readers in providing temporal contexts in clastic depositional systems: opportunities in geomorphology” Luminescence readers are devices that are used to detect low levels of light emitted by geological samples when stimulated by heat or another light source. The light from the samples comes from energy that accumulates in mineral grains such as quartz or feldspar as a result of low level radioactivity that occurs naturally in earth materials. This energy accumulates over time as long at the samples are shielded from light. Therefore luminescence signals can be used to measure burial age of the samples. Over the last 5-6 years, portable versions of the regular lab-bound luminescence readers have been developed and while these are simpler devices, they can be used to obtain luminescence signals much more rapidly than with the lab-bound OSL readers. Our presentation in Paris outlined three case studies that we have carried out in Alberta that illustrate the utility of portable OSL in geomorphology, which is the study of the shape of the earth’s surface. In the first study, we used the portable OSL reader to determine relative ages of depositional units in a dune landscape in southern Alberta. In the second study we used the portable reader to demarcate basal sections of wind deposited dunes that overlie glacial sands in central and northern Alberta. In the third study we used the portable reader to differentiate between sedimentary units disrupted by human activity (oil and gas related pipeline work) and those that are still naturally intact. Overall, the three studies illustrate the usefulness of portable OSL readers in providing a better insight with regards to the timing of deposition in young sedimentary systems, especially in those emplaced by wind. Understanding such contexts is central to the study and interpretation of geological processes that take place near the earth’s surface.The recent development ofa functional portable optically stimulated luminescence (POSL) readers has ushered in new opportunities in geomorphology. Although POSL readers do not necessarily provide absolute ages as in regular OSL dating, they can be used to readily acquire luminescence signals from clastic sediments. Such signals can be used to construct luminescence profiles which depict the variation of the luminescence signal with depth within a depositional sequence. Luminescence signals depend on dose rate, sensitivity of the mineral grains, mineralogy, degree of bleaching and burial age of the sediments. When all these parameters apart from burial age are held constant, the luminescence profile can serve as a proxy for the chronostratigraphy. A number of studies we have carried out on the Canadian prairies with a POSL reader developed by the Scottish Universities Environmental Research Centre serves to illustrate the utility of the readers. Their portability means that the device can be carried to the field and analysis can be performed on bulk samples, negating the need for time-intensive mineralogical separations, as is required in regular OSL dating. In one study we used the POSL reader to profile Holocene eolian dune sequences to determine the relative ages of the depositional units as well as ascertain whether any lengthy depositional hiatuses exist within the sequences. In another study we profiled postglacial dunes that overlie glaciofluvial sands in an effort to delineate the interface between the two depositional facies. In a third study we used luminescence profiling to identify eolian dune sands that were still intact from those that had experienced post-depositional mixing. In all three cases, luminescence profiling afforded an enhanced temporal context of the stratigraphy, permitting better sample targeting for regular OSL dating. Overall the studies underscore the breadth of geomorphological settings in which the POSL readers can be used

OSL investigations at Hardisty, Alberta, Canada

This report is concerned with optically stimulated luminescence (OSL) dating investigations of sediments associated with, and enclosing artefacts of First Nations historic significance in the Battle River Valley area, near Hardisty, east central Alberta. The OSL ages reported here provide chronological control to the archaeological investigations at this site, led by Rob Wondrasek, which have identified thousands of historical artefacts, including projectile points and lithic fragments indicative of occupation. The investigations were commissioned by Enbridge, ahead of the construction of the Edmonton-Hardisty Pipeline, and form one part of a historic resources impact assessment study, to characterise the archaeological site, and evaluate/mitigate the impact of the pipeline related excavations. This report describes the background to the investigation, sampling, and luminescence analysis undertaken to generate sediment chronologies for the Hardisty sediment stratigraphies. Ken Munyikwa visited the archaeological investigations at Hardisty in June 2014 to sample key stratigraphic units within the sediment stratigraphies for OSL dating. Samples were collected from two profiles: from strata encompassing the artefact-bearing horizon, and from strata immediately beneath and overlying this horizon, thus providing terminus post quem (TPQ) and terminus ante quem (TAQ) on the age of this unit. Samples were submitted to the luminescence laboratories at SUERC for dating in August 2014. All samples were subjected to laboratory preparation of sand-sized quartz, and purity checked by scanning electron microscopy. Dose rates for the bulk sediment were evaluated using analyses of the uranium, thorium and potassium concentrations obtained by high resolution gamma spectrometry coupled with beta dose rate measurement using thick source beta counting. Equivalent doses were determined by OSL from 64 aliquots of quartz per sample using the quartz single-aliquot-regenerative (SAR) procedure. The material exhibited good OSL sensitivity and produced acceptable SAR internal quality control performance. Dose distributions from the aliquots were examined using radial plotting methods. All samples revealed some heterogeneity in their equivalent dose distribution, reflecting variable bleaching at deposition and indicating that each sample enclosed mixed-age materials. Age estimates were based on the weighted mean estimate of the stored dose, which weights the stored dose estimate towards the lowest population of equivalent doses, potentially representing the better bleached (at deposition) component. The quartz OSL ages reported herein for the sand sequences at Hardisty-1 and Hardisty-2, have provided the first means to assess the temporal distribution of artefacts within the Hardisty profiles, and furthermore provide TPQ and TAQ for the inferred occupational phases. The sediment chronologies established for each profile are internally coherent, spanning at HD-01 from 7.8 ± 0.7 ka (SUTL2692) to 11.7 ± 0.5 ka (SUTL2694), and at HD-02 from 4.5 ± 0.2 ka (SUTL2695) to 8.7 ± 0.5 ka (SUTL2697; Table 4-1). TPQ for the occupation of the Hardisty site is provided by SUTL2697 at 8.7 ± 0.5 ka. TAQ for the occupation of the Hardisty site is provided by SUTL2695 at 4.5 ± 0.2 ka

Further material of the ceratosaurian dinosaur Syntarsus from the Elliot Formation (Early Jurassic) of South Africa

Two further fossils recovered from the Elliot Formation in South Africa are referred to the ceratosaurian genus Syntarsus: a partial pelvis and a well preserved and articulated snout. The pelvic fragment consists of most of the posterior end of the left ilium and sacrum, with a small part of the right ilium attached. The acetabular area and ‘brevis shelf’ of the left ilium are well preserved, as is the ventral surface of the sacrum. These parts show features characteristic of Syntarsus material from Zimbabwe. The snout has the premaxillae, maxillae, nasals and dentaries from both sides preserved, of which only the premaxillae are more or less complete. The premaxilla has four alveoli and the maxilla nine, and the maxilla bears the characteristic dimpling on its lateral surface also seen in Syntarsus material collected in Zimbabwe. The snout also possesses the characteristic small diastema or subnarial gap between the premaxillary and maxillary teeth shown by Syntarsus material from elsewhere. The snout is strongly compressed bilaterally and the jaws are tightly closed, so that the dentary teeth are obscured beneath the upper dentition. This compression has crushed the palatal region, obscuring palatal details.The Council's Research Committe, University of the Witwatersrand; National Science Foundatio

Barriers to Accessing Acute Care for Newly Arrived Refugees

Introduction: Over the past decade, the number of refugees arriving in the United States (U.S.) has increased dramatically. Refugees arrive with unmet health needs and may face barriers when seeking care. However, little is known about how refugees perceive and access care when acutely ill. The goal of this study was to understand barriers to access of acute care by newly arrived refugees, and identify potential improvements from refugees and resettlement agencies.Methods: This was an in-depth, qualitative interview study of refugees and employees from refugee resettlement and post-resettlement agencies in a city in the Northeast U.S. Interviews were audiotaped, transcribed, and coded independently by two investigators. Interviews were conducted until thematic saturation was reached. We analyzed transcripts using a modified grounded theory approach.Results: Interviews were completed with 16 refugees and 12 employees from refugee resettlement/post-resettlement agencies. Participants reported several barriers to accessing acute care including challenges understanding the U.S. healthcare system, difficulty scheduling timely outpatient acute care visits, significant language barriers in all acute care settings, and confusion over the intricacies of health insurance. The novelty and complexity of the U.S. healthcare system drives refugees to resettlement agencies for assistance. Resettlement agency employees express concern with directing refugees to appropriate levels of care and report challenges obtaining timely access to sick visits. While receiving emergency department (ED) care, refugees experience communication barriers due to limitations in consistent interpretation services.Conclusion: Refugees face multiple barriers when accessing acute care. Interventions in the ED, outpatient settings, and in resettlement agencies, have the potential to reduce barriers to care. Examples could include interpretation services that allow for clinic phone scheduling and easier access to interpreter services within the ED. Additionally, extending the Refugee Medical Assistance program may limit gaps in insurance coverage and avoid insurance-related barriers to seeking care

The Last Mile of Broadband: Estimating the Economic Impacts of Connect America Fund Initiative

I use a county-level panel dataset from 2013 to 2019 to assess the impacts of a federal program that provided massive subsidies to facilitate the expansion of broadband infrastructure: The Connect America Fund Phase II Program. This program incentivized telecommunications carriers to provided broadband access to high-cost areas in the United States (typically rural and other underserved communities). I study the impact of this "last mile" of broadband and assessing broadband access on local economic employment outcomes. I find that program funding in a geographic area has a positive effect on weekly wages, and potentially has a positive impact on population development.S.M

Cranial morphology of a primitive dinocephalian from the Madumabisa Mudstone Formation, Zimbabwe

A dissertation submitted to the Faculty of Science, University of Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science.Dinocephalians form an important part of the Upper Permian therapsid faunas of South Africa and Russia, and have also recently been reported from China and Brazil, and even more recently a diverse dinocephalian fauna has been described from Zimbabwe. This thesis reports a new primitive tapinocephalid dinocephalian, NHMB 1556, from the Upper Madumabisa Mudstone Formation in Zimbabwe. NHMB 1556 is considered to be closely related to Avenantia and it possesses primitive tapinocephalid characters, but is more derived than Tapinocaninus, the most primitive tapinocephalid dinocephalian known. NHMB 1556 is distinguished from other tapinocephalines by having a groove on the squamosal below its dorsal contact with the parietal, a low squamosal-parietal suture on the posterior border of the temporal fenestra, a vomer which extends posteroventrally and forms the anterior margin of the interpterygoidal vacuity and basisphenoid, which is semi-circular anteroventrally.AC201