Thule Fishing Revisited: The Economic Importance of Fish at the Pembroke and Bell Sites,Victoria Island,Nunavut

Geografisk Tidsskrift—Danish Journal of Geography 110(2):261–278, 2010

In a comprehensive overview of evidence for fishing in the Thule period of the eastern North American Arctic, Whitridge (2001) noted that fish bones are either extremely rare or absent in archaeofaunal samples, despite the fact that artifact assemblages typically contain a variety of fishing implements. In this paper, we present new faunal data from two sites on southeastern Victoria Island, Nunavut, which offer a marked contrast to this pattern. The Pembroke site, located just north of Cambridge Bay, is a small Thule site probably occupied during an early migration into the region. The Bell site, located on the Ekalluk River, is a more substantial site, occupied for a much longer duration during the Thule period. These sites are located in areas devoid of many taxa preferred by Thule peoples, which led the sites' occupants to rely on caribou and fish for much of their winter subsistence. At the Bell site, storage of caribou and fish was critical for winter survival. However, the occupants of the Pembroke site appear to have been unable to acquire sufficient stores during the fall, and therefore relied on fishing through the ice during winter to supplement their inadequate stores. Although both sites indicate a more important economic role for fish than has been recorded on any other eastern Arctic Thule winter site, the use of fish at the two sites differs markedly, adding nuance to archaeologically known Thule subsistence patterns.     

Spatial analysis weighting algorithm using Voronoi diagrams

Data layers that represent geographical constraints in a multidimensional GIS model must be appropriately weighted to effectively account for the diversity as well as the functional and spatial interrelationships between the constraints. This paper presents a spatial analysis weighting algorithm (SAWA) using Voronoi diagrams. The basic functions of the SAWA are defined so that the spatialization of weights is done according to two approaches: a global spatialization method based on the statistical distribution of the original data and a contextual approach where neighbourhood defined by Voronoi diagrams is integrated into the weighting functions. Different simulations on artificial and real maps applied to the problem of shortest path optimisation are analysed. The results show that the effective integration of the spatial dimension in a weighting process is not only possible but also improves the optimisation of shortest paths. Research is continuing to improve the contextual phase of the algorithm.     

SOIL VARIATION ON NORTH AND SOUTH SLOPE CATENAS ON A KAME IN SOUTHEAST WISCONSIN

Soils from two catenas on north-and south-facing slopes of a kame were analyzed to determine the effect of lithology, topography, and microclimate on profile development. In loess on the north-facing slope, where microclimate favored CaCO₃ dissolution and clay translocation, pedogenesis was rapid and an A-E-Bt-C profile developed. In contrast, an A-Bt-C profile developed on the south-facing slope. In gravel where limestone/dolostone dissolution was slow, A-C profiles were found and CaCO₃ was depleted to a ≤ 25-cm depth, 20± cm less than reported for similar Michigan soils. Slopewash and runoff are inferred to have caused silt accumulations and greater infiltration at the base of ≥ 20° slopes, resulting in a thicker solum in foot-and toe-slope positions, whereas on slopes of ≤ 7° infiltration and interflow are the dominant processes, resulting in a thicker solum on the transportational midslope. The differences in soil profile development are attributed to sediment facies changes at 25- to 50-cm depth and resulting groundwater movement. [Key words: soil development, soil spatial variability, kame slope catena, Wisconsin.]     

Occurrence and significance of a cold-water carbonate pseudomorph in microbialites from a saline lake

Micron-scale pseudomorphs of calcite after ikaite were discovered in microbialites from Manito Lake, a large hypersaline lake in the Great Plains of western Canada. Although environmental conditions in the lakes of this region (seasonally cold temperatures, high salinities and elevated productivity) suggest that ikaite should be common, this is the first documentation of lacustrine ikaite in Canada and the Great Plains region of North America. The calcite pseudomorphs form a porous dendritic fabric, comprise the interiors of massive shoreline microbialite mounds and pinnacles, and are encased in centimeter-scale, laminated dolomite-aragonite rinds. Because of the limited thermodynamic stability of ikaite at or near freezing temperatures, the psuedomorphs of this mineral provide evidence of an extended cold episode during the first millennium AD. The Manito deposits also show high δ¹³C values, indicating elevated productivity and δ¹⁸O signatures are consistent with precipitation in a cold, somewhat fresher lake than present.     

Trace-element composition and zoning in clinopyroxene- and amphibole-group minerals: Implications for element partitioning and evolution of carbonatites

The present work is a first comprehensive study of the trace-element composition and zoning in clinopyroxene- and amphibole-group minerals from carbonatites, incorporating samples from 14 localities worldwide (Afrikanda, Aley, Alnö, Blue River, Eden Lake, Huayangchuan, Murun, Oka, Ozernaya Varaka, Ozernyi, Paint Lake, Pinghe, Prairie Lake, Turiy Mys). The new electron-microprobe data presented here significantly extend the known compositional range of clinopyroxenes and amphiboles from carbonatites. These data confirm that calcic and sodic clinopyroxenes from carbonatites are not separated by a compositional gap, instead forming an arcuate trend from nearly pure diopside through intermediate aegirine–augite compositions confined to a limited range of CaFeSi₂O₆ contents (15–45 mol%) to aegirine with < 25 mol% of CaMgSi₂O₆ and a negligible proportion of CaFeSi₂O₆. A large set of LA-ICPMS data shows that the clinopyroxenes of different composition are characterized by relatively low levels of Cr, Co and Ni (≤ 40 ppm) and manifold variations in the concentration of trivalent lithophile and some incompatible elements (1–150 ppm Sc, 26–6870 ppm V, 5–550 ppm Sr, 90–2360 ppm Zr, and nil to 150 ppm REE), recorded in some cases within a single crystal. The relative contribution of clinopyroxenes to the whole-rock Rb, Nb, Ta, Th and U budget is negligible. The major-element compositional range of amphiboles spans from alkali- and Al-poor members (tremolite) to Na–Al-rich Mg- or, less commonly, Fe-dominant members (magnesiohastingsite, hastingsite and pargasite), to calcic–sodic, sodic and potassic–sodic compositions intermediate between magnesio-ferrikatophorite, richterite, magnesioriebeckite, ferri-nyböite and (potassic-)magnesio-arfvedsonite. In comparison with the clinopyroxenes, the amphiboles contain similar levels of tetravalent high-field-strength elements (Ti, Zr and Hf) and compatible transition elements (Cr, Co and Ni), but are capable of incorporating much higher concentrations of Sc and incompatible elements (up to 500 ppm Sc, 43 ppm Rb, 1470 ppm Sr, 1230 ppm Ba, 80 ppm Pb, 1070 ppm REE, 140 ppm Y, and 180 ppm Nb). In some carbonatites, amphiboles contribute as much as 25% of the Zr + Hf, 15% of the Sr and 35% of the Rb + Ba whole-rock budget. Both clinopyroxenes and amphiboles may also host a significant share (~ 10%) of the bulk heavy-REE content. Our trace-element data show that the partitioning of REE between clinopyroxene (and, in some samples, amphibole) and the melt is clearly bimodal and requires a revision of the existing models assuming single-site REE partitioning. Clinopyroxenes and amphiboles from carbonatites exhibit a diversity of zoning patterns that cannot be explained exclusively on the basis of crystal chemistry and relative compatibility of different trace-element in these minerals. Paragenetic analysis indicates that in most cases, the observed zoning patterns develop in response to removal of selected trace elements by phases co-precipitating with clinopyroxene and amphibole (especially magnetite, fluorapatite, phlogopite and pyrochlore). With the exception of magnesiohastingsite–richterite sample from Afrikanda, the invariability of trace-element ratios in the majority of zoned clinopyroxene and amphibole crystals implies that fluids are not involved in the development of zoning in these minerals. The implications of the new trace-element data for mineral exploration targeting REE, Nb and other types of carbonatite-hosted rare-metal mineralization are discussed.     

Granitic magmatism,basement ages,and provenance indicators in the Malay Peninsula: Insights from detrital zircon U–Pb and Hf-isotope data

The Malay Peninsula lies on two continental blocks, Sibumasu and East Malaya, which are intruded by granitoids in two provinces: the Main Range and Eastern. Previous models propose that Permian–Triassic granitoids are subduction-related and syn-to post-collisional. We present 752 U–Pb analyses that were carried out on zircons from river sands in the Malay Peninsula; of these, 243 grains were selected for Hf-isotope analyses. Our data suggest a more complex Sibumasu–East Malaya collision history. ¹⁷⁶Hf/¹⁷⁷Hf_i ratios reveal that Permian–Triassic zircons were sourced from three magmatic suites: (a) Permian crustally-derived granitoids, (b) Early-Middle Triassic granitoids with mixed mantle–crust sources, and (c) Late Triassic crustally-derived granitoids. This suggests three Permian–Triassic episodes of magmatism in the Malay Peninsula, two of which occurred in the Eastern Province. Although the exact timing of the Sibumasu–East Malaya collision remains unresolved, current data suggest that it occurred before the Late Triassic, probably in Late Permian–Early Triassic. Our data also indicate that Sibumasu and East Malaya basements are chronologically heterogeneous, but predominantly of Proterozoic age. Some basement may be Neoarchaean but there is no evidence for basement older than 2.8 Ga. Finally, we show that Hf-isotope signatures of Triassic zircons can be used as provenance indicators.     

Uranium and Thorium Concentration and Isotopic Composition in Five Glass (BHVO‐2G,BCR‐2G,NKT‐1G,T1‐G,ATHO‐G) and Two Powder (BHVO‐2, BCR‐2) Reference Materials

Here we report uranium and thorium isotopic ratios and elemental concentrations measured in solid reference materials from the USGS (BHVO‐2G, BCR‐2G, NKT‐1G), as well as those from the MPI‐DING series (T1‐G, ATHO‐G). Specifically created for microanalysis, these naturally‐sourced glasses were fused from rock powders. They cover a range of compositions, elemental concentrations and expected isotopic ratios. The U‐Th isotopic ratios of two powdered source materials (BCR‐2, BHVO‐2) were also characterised. These new measurements via multi‐collector thermal ionisation mass spectrometry and multi‐collector inductively coupled plasma‐mass spectrometry can now be used to assess the relative performance of techniques and facilitate comparison of U‐Th data amongst laboratories in the geoscience community for in situ and bulk analyses.     

A Comparative Study of Five Reference Materials and the Lombard Meteorite for the Determination of the Platinum‐Group Elements and Gold by LA‐ICP‐MS

A range of independently characterised reference materials (RMs) for LA‐ICP‐MS, used for the determination of the platinum‐group elements (PGE) and Au in a sulfide matrix, were analysed and compared: 8b, PGE‐A, NiS‐3, Po727‐T1, Po724‐T and the Lombard meteorite. The newly developed RM NiS‐3 was used as the RM for the calibration of all LA‐ICP‐MS analyses and the measured concentrations of the other RMs compared against their published concentrations. This data were also used to assess the consistency of concentrations calibrated against the different RMs. It was found that Po727‐T1 and 8b produced results that were comparable, within uncertainty, for all elements. Po727‐T1 also produced consistent results with NiS‐3 for all elements. All other RMs showed differences for some elements, especially Ru in Po724‐T, and Os, Ir and Au in PGE‐A. The homogeneity of the PGE and Au in each RM was assessed, by comparing the precision of multiple LA‐ICP‐MS spot analyses with the average uncertainty of the signal. Po724‐T, Po727‐T1 and the Lombard meteorite were found to be homogeneous for all elements, but 8b, PGE‐A and NiS‐3 were heterogeneous for some elements. This is the first direct comparison between a range of independently characterised PGE and Au LA‐ICP‐MS RMs.     

Elevation adjustments of paired natural levees during flooding of the Saskatchewan River

Natural levees control the exchange of water between an alluvial channel and its floodplain, but little is known about the spatial distribution and evolution of levee heights. The summer 2005 flood of the Saskatchewan River (Cumberland Marshes, east‐central Saskatchewan) inundated large areas of floodplain for up to seven weeks, forming prominent new deposits on natural levees along main‐stem channels. Measurements of flood‐deposit thickness and crest heights of 61 levee pairs show that the thickest deposits occur on the lower pre‐flood levee in 80% of the sites, though no clear relationship exists between deposit thickness and magnitude of height difference. Only 16% of the pairs displayed thicker deposits on the higher levee, half of which occurred at sites where relatively clear floodbasin waters re‐entered turbid channels during general flooding. Difference in crest elevation (ΔE) between paired levees is approximately log‐normally distributed, both before and after the flood, though with different mean values. Supplemental observations from tank experiments indicate that during near‐bankfull flows, temporally and spatially variable deposition and erosion occur on levees due to backwater effects associated with nearby channel bars and irregular rises of the channel bed forced by channel extension. During floods, preferential deposition in lows tends to even out crest heights. Copyright © 2009 John Wiley & Sons, Ltd.     

Truncation of the distribution of ground-motion residuals

Recent studies to assess very long-term seismic hazard in the USA and in Europe have highlighted the importance of the upper tail of the ground-motion distribution at the very low annual frequencies of exceedance required by these projects. In particular, the use of an unbounded lognormal distribution to represent the aleatory variability of ground motions leads to very high and potentially unphysical estimates of the expected level of shaking. Current practice in seismic hazard analysis consists of truncating the ground-motion distribution at a fixed number (ε _max) of standard deviations (σ). However, there is a general lack of consensus regarding the truncation level to adopt. This paper investigates whether a physical basis for choosing ε _max can be found, by examining records with large positive residuals from the dataset used to derive one of the ground-motion models of the Next Generation Attenuation (NGA) project. In particular, interpretations of the selected records in terms of causative physical mechanisms are reviewed. This leads to the conclusion that even in well-documented cases, it is not possible to establish a robust correlation between specific physical mechanisms and large values of the residuals, and thus obtain direct physical constraints on ε _max. Alternative approaches based on absolute levels of ground motion and numerical simulations are discussed. However, the choice of ε _max is likely to remain a matter of judgment for the foreseeable future, in view of the large epistemic uncertainties associated with these alternatives. Additional issues arise from the coupling between ε _max and σ, which causes the truncation level in terms of absolute ground motion to be dependent on the predictive equation used. Furthermore, the absolute truncation level implied by ε _max will also be affected if σ is reduced significantly. These factors contribute to rendering a truncation scheme based on a single ε _max value impractical.