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

Instant luminescence chronologies? High resolution luminescence profiles using a portable luminescence reader

Establishing a robust chronology is fundamental to most palaeoenvironmental studies. However, the number and positioning of dated points is critical. Using a portable luminescence reader, it is possible to rapidly generate high resolution down core relative age profiles. Profiles of portable luminescence data from two coastal dunes were evaluated and compared with the results of particle size analysis, stratigraphy, and an independent historical chronology. Results show that, even in young samples, portable luminescence data is dominated by an age related signal which in homogeneous sediment need not be corrected for moisture, feldspar content changes or grain size. Profiles therefore provide relative chronologies from which accumulation phases can be established, and from which better targeted sampling and comparison to other sites could be undertaken. Even though they do not provide instant absolute chronologies, field-based portable luminescence profiling of Late Quaternary sites hold much potential to improve the resultant chronologies

Temporal Constraints for the Late Wisconsinan Deglaciation of Western Canada Using Eolian Dune Luminescence Chronologies From Alberta

The Laurentide Ice Sheet (LIS) covered most of Canada during the Last Glacial Maximum. Sometime after 20 cal. ka BP, the LIS began to recede from western Canada and, by 11 cal. ka BP, it had retreated from most of the province of Alberta. Due to the scarcity of datable contemporaneous organic materials, the precise timing of the retreat of the ice sheet from the region remains poorly constrained so that the chronology of the sequential positions of the ice sheet margin between 20 and 11 cal. ka BP is largely tentative. In this study, we use luminescence dating of postglacial eolian deposits, sourced primarily from glaciolacustrine and deltaic sediments in central and northern Alberta, to provide an updated chronology for the retreat of the LIS from the region. We examine 14 new and 13 previously published quartz optically stimulated luminescence (OSL) ages, as well as 19 previously published K-feldspar infrared stimulated luminescence ages. The chronologies are used to constrain successive regional ice sheet margin positions that are geomorphically recognizable across the region between 16 and 11 ka (calendar years). These data suggest that the LIS may have retreated from central Alberta earlier than portrayed in radiocarbon derived deglaciation models. We propose that the OSL chronology from postglacial dunes constrains the deglaciation of the region more accurately because luminescence dating does not rely on the development of vegetation to produce material for dating. Implications for the revised chronology include an improved timing of the emergence of an ice-free corridor that may have been used for Paleoindian migration into the Americas as well as enhanced age constraints on when meltwater drainage routes to the Arctic became open in relationship to the Younger Dryas. The chronology could also provide improved constraints for geophysical models that reconstruct regional isostatic rebound which followed deglaciation

Constraining the chronology of the Late Wisconsinan retreat of the Laurentide Ice Sheet from western Canada using luminescence ages from postglacial aeolian dune sequences

Optically stimulated luminescence (OSL) dating of quartz extracts from postglacial aeolian dunes from central Alberta in western Canada points to a landscape that was free of ice as early as 15 ka. Data from profiles where multiple ages have been obtained indicate an increase in depositional age with depth, suggesting that older aeolian sands underlie the dated sequences. The OSL ages present plausible minimum age constraints for the retreat of the Laurentide Ice Sheet (LIS) towards the end of the Late Wisconsinan glaciation. Previous reconstructions of the LIS recession have relied on radiocarbon chronologies, despite the scarcity of contemporaneous radiocarbon-bearing material for large parts of western Canada. While the OSL chronology may be deemed concordant with ice sheet margin retreat models determined using radiocarbon data, there appears to be a systematic lag in the radiocarbon ages which may reflect that aeolian activity is initiated prior to the proliferation of organic material. The OSL chronology reported in this study does not preclude the emergence of a wide deglacial corridor between the LIS and the Cordilleran Ice Sheet by 15 ka or earlier. The possibility of such a passage would resuscitate the notion of an ice-free corridor that appeared early enough to afford the first peoples of the Americas a navigable inland migratory passage from Beringia to south of the North American ice sheets. More broadly, the corridor would also have allowed genetic exchanges between the Beringian refugium and the American middle and low latitudes

Temporal constraints for Holocene geomorphic evolution at an archeological site near Hardisty, east-central Alberta: hunter gatherer interactions with the landscape on the northern Plains

Extended terrestrial geomorphic sequences that host well-dated depositional evidence of early to mid-Holocene human interactions with the physical landscape are relatively scarce on the northern Plains. The paucity of such records hampers studies that aim to examine human adaptations to environmental changes in the region during the Hypsithermal (ca. 9,000–4,500 years ago). Where deposits occur, the absence of well-preserved contemporaneous organic material for radiocarbon dating highlights the need for alternative chronometers. In this study, we present new absolute chronologies from three archaeological sites in an eolian dune landscape in east-central Alberta that we determined using optically stimulated luminescence dating. The results show that between ca. 11,000–2,000 years ago, the local landscape evolved through recurrent episodes of instability, interspersed with periods of soil development. The findings allow us to provide new insights on Holocene landscape evolution in the area and examine adaptations humans made to cope with the Hypsithermal environment, as evidenced by archaeological materials associated with hunting and camping

Temporal constraints for Holocene geomorphic evolution at an archeological site near Hardisty, east-central Alberta: hunter gatherer interactions with the landscape on the northern Plains

No abstract available

Progress made in FEC transformation of cassava

In cassava friable embryogenic callus (FEC) has been used to obtain transgenic plants using particle bombardment, electroporation, and Agrobacterium tumefaciens. FEC cultures have been obtained in 6 of the 10 tested genotypes. In all genotypes FEC could be regenerated into plants, however the efficiency differed between the genotypes. Almost all plants regenerated from 6 months old FEC cultures of TMS604444, Adira 4, Thai 5 and M7 were morphological similar to control plants. However, in R60 and R90 a large number of plants were not identical to control plants. Older FEC lines of TMS60444 have a reduced ability to regenerate plants and the plants show somaclonal variation. Somaclonal variation is observed in the same extend in transgenic and non-transgenic plants. The origin of this variation is both genetic and epigenetic. Luciferase based selection is less efficient in producing transgenic lines than chemical selection. Furthermore Agrobacterium tumefaciens mediated transformation is much more efficient than particle bombardment with respect to the production of transgenic lines. A tentative model is introduced which best describes the effect of different selection regimes on the time period required to produce transgenic plants. Kanamycin and stringent luciferase selection required a shorter period of time than selection based on hygromycin, phosphinothricin or non-stringent luciferase. However, a more significant reduction of time was obtained if young instead of old FEC lines of genotype TMS60444 were used for genetic modification. In accordance to the model these young FEC lines of TMS60444 produced transgenic plants within 4 months with both Agrobacterium tumefaciens combined with kanamycin selection and particle bombardment combined with stringent luciferase selection