Late Quaternary loess in northeastern Colorado: Part I—Age and paleoclimatic significance

Loess in eastern Colorado covers an estimated 14,000 km2, and is the westernmost part of the North American midcontinent loess province. Stratigraphic studies indicate there were two periods of loess deposition in eastern Colorado during late Quaternary time. The first period spanned ca. 20,000 to 12,000 14C yr B.P. (ca. 20–14 ka) and correlates reasonably well with the culmination and retreat of Pinedale glaciers in the Colorado Front Range during the last glacial maximum. The second period of loess deposition occurred between ca. 11,000 and 9,000 14C yr B.P. This interval may be Holocene or may correlate with a hypothesized Younger Dryas glacial advance in the Colorado Front Range. Sedimentologic, mineralogic, and geochemical data indicate that as many as three sources could have supplied loess in eastern Colorado. These sources include glaciogenic silt (derived from the Colorado Front Range) and two bedrock sources, volcaniclastic silt from the White River Group, and clays from the Pierre Shale. The sediment sources imply a generally westerly paleowind during the last glacial maximum. New carbon isotope data, combined with published faunal data, indicate that the loess was probably deposited on a cool steppe, implying a last glacial maximum July temperature depression, relative to the present, of at least 5–6 °C. Overall, loess deposition in eastern Colorado occurred mostly toward the end of the last glacial maximum, under cooler and drier conditions, with generally westerly winds from more than one source

Isotopic tracers of gold deposition in Paleozoic limestones, Southern Nevada

Strontium isotopic analyses of barren and mineralized Paleozoic carbonate rocks show that hydrothermal fluids added radiogenic strontium ({sup 87}Sr) to the mineralized zones. At Bare Mountain, samples collected from mineralized areas have {delta}{sup 87}Sr{sub t} values ranging from +3.0 to +23.0, whereas unmineralized carbonate rocks have {delta}{sup 87}Sr, values of {minus}0.6 to +2.9. In other ranges, {delta}{sup 87}Sr, values of the unmineralized carbonate rocks are even lower and virtually indistinguishable from primary marine values. This correlation of elevated {delta}{sup 87}Sr{sub t} values with mineralized zones provides a useful technique for assessing the mineral potential of the Paleozoic basement beneath Yucca Mountain, and may find broader use in mineral exploration in the Basin and Range province as a whole

Chronology of Dune Development in the White River Badlands, Northern Great Plains, USA

Aeolian dune field chronologies provide important information on drought history on the Great Plains. The White River Badlands (WRB) dunes are located approximately 60 km north of the Nebraska Sand Hills (NSH), in the western section of the northern Great Plains. Clifftop dunes, sand sheets, and stabilized northwest-southeast trending parabolic dunes are found on upland mesas and buttes, locally called tables. The result of this study is a dune stabilization history determined from samples collected from stratigraphic exposures and dune crests. Thirty-seven OSL ages, from this and previous investigations, show three periods of dune activity: 1) ∼21,000 years ago to 12,000 years ago (a), 2) ∼9 to 6 ka, and 3) post-700 a. Stratigraphic exposures and low-relief dune forms preserve evidence of late Pleistocene and middle Holocene dune development, while high-relief dune crests preserve evidence of late Holocene dune development. Results of 12 OSL ages from the most recent dune activation event indicate that Medieval Climate Anomaly (MCA) droughts and Little Ice Age (LIA) droughts caused dune reactivation on the tables. Dune reactivation was accompanied by other drought-driven geomorphological responses in the WRB, including fluvial incision of the prairie and formation of sod tables. Regional significance of the MCA and LIA droughts is supported by similarities in the aeolian chronologies of the NSH at 700–600 a and some western Great Plains dune fields at 420–210 a. Aerial photographs of the WRB show little activity during the Dust Bowl droughts of the 1930s

Neoproterozoic to early Paleozoic extensional and compressional history of East Laurentian margin sequences: The Moine Supergroup, Scottish Caledonides

Neoproterozoic siliciclastic-dominated sequences are widespread along the eastern margin of Laurentia and are related to rifting associated with the breakout of Laurentia from the supercontinent Rodinia. Detrital zircons from the Moine Supergroup, NW Scotland, yield Archean to early Neoproterozoic U-Pb ages, consistent with derivation from the Grenville-Sveconorwegian orogen and environs and accumulation post–1000 Ma. U-Pb zircon ages for felsic and associated mafic intrusions confirm a widespread pulse of extension-related magmatism at around 870 Ma. Pegmatites yielding U-Pb zircon ages between 830 Ma and 745 Ma constrain a series of deformation and metamorphic pulses related to Knoydartian orogenesis of the host Moinerocks. Additional U-Pb zircon and monazite data, and 40Ar/39Ar ages for pegmatites and host gneisses indicate high-grade metamorphic events at ca. 458–446 Ma and ca. 426 Maduring the Caledonian orogenic cycle.The presence of early Neoproterozoic silici clastic sedimentation and deformation in the Moine and equivalent successions around the North Atlantic and their absence along strike in eastern North America reflect contrasting Laurentian paleogeography during the breakup of Rodinia. The North Atlantic realm occupied an external location on the margin of Laurentia, and this region acted as a locus for accumulation of detritus (Moine Supergroup and equivalents) derived from the Grenville-Sveconorwegian orogenic welt, which developed as a consequence of collisional assembly of Rodinia. Neoproterozoic orogenic activity corresponds with theinferred development of convergent platemargin activity along the periphery of the supercontinent. In contrast in eastern North America, which lay within the internal parts of Rodinia, sedimentation did not commence until the mid-Neoproterozoic (ca. 760 Ma) during initial stages of supercontinent fragmentation. In the North Atlantic region, this time frame corresponds to a second pulse of extension represented by units such as the Dalradian Supergroup, which unconformably overlies the predeformed Moine succession

Balancing, Proportionality, and Constitutional Rights

In the theory and practice of constitutional adjudication, proportionality review plays a crucial role. At a theoretical level, it lies at core of the debate on rights adjudication; in judicial practice, it is a widespread decision-making model characterizing the action of constitutional, supra-national and international courts. Despite its circulation and centrality in contemporary legal discourse, proportionality in rights-adjudication is still extremely controversial. It raises normative questions—concerning its justification and limits—and descriptive questions—regarding its nature and distinctive features. The chapter addresses both orders of questions. Part I centres on the justification of proportionality review, the connection between proportionality, balancing and theories of rights and the critical aspects of this connection. Part II identifies and analyses the different forms of proportionality both in review, as a template for rights-adjudication, and of review, as a way of defining the scope and limits of adjudication

The Influence of International Law on the International Movement of Persons

Many migration theories identify ‘the law’ as a significant constraint on the international movement of persons. While this constraint often operates through national migration legislation, this study examines the influence of international law in shaping contemporary patterns in the international movement of persons at the macro level. The analysis begins with an examination of the long-established power of a State to regulate cross-border movement of persons as an inherent attribute of State sovereignty, together with the accepted limitations on a State’s power to control entry and exit. Yet, international law reaches well beyond the movement of people across borders. The development of international human rights law has been a key constraint on state action in the United Nations era by also regulating the treatment of migrants within a State’s borders. The study considers how international law has responded to current migration issues, including: protection of migrant women and children; suppression of smuggling and trafficking of people; labour migration; and environmental migration. As in other areas of international society, there has been a proliferation of institutions through which international migration law is made and enforced. The most prominent among them are the United Nations High Commissioner for Refugees (UNHCR) and the International Organization for Migration (IOM), but the establishment of other entities with overlapping mandates has given rise to calls for a new international migration regime based on streamlined institutional arrangements. The study concludes that international law is an imperfect framework for regulating the international movement of persons because it has developed in a piecemeal fashion over a long time to deal with issues of concern at particular points in human history. Yet, despite its shortfalls, international law and its associated institutions unquestionably play a most important role in constraining and channeling state authority over the international movement of persons

Model International Mobility Convention

While people are as mobile as they ever were in our globalized world, the movement of people across borders lacks global regulation. This leaves many refugees in protracted displacement and many migrants unprotected in irregular and dire situations. Meanwhile, some states have become concerned that their borders have become irrelevant. International mobility—the movement of individuals across borders for any length of time as visitors, students, tourists, labor migrants, entrepreneurs, long-term residents, asylum seekers, or refugees—has no common definition or legal framework. To address this key gap in international law, and the growing gaps in protection and responsibility that are leaving people vulnerable, the "Model International Mobility Convention" proposes a framework for mobility with the goals of reaffirming the existing rights afforded to mobile people (and the corresponding rights and responsibilities of states) as well as expanding those basic rights where warranted. In 213 articles divided over eight chapters, the Convention establishes both the minimum rights afforded to all people who cross state borders as visitors, and the special rights afforded to tourists, students, migrant workers, investors and residents, forced migrants, refugees, migrant victims of trafficking and migrants caught in countries in crisis. Some of these categories are covered by existing international legal regimes. However, in this Convention these groups are for the first time brought together under a single framework. An essential feature of the Convention is that it is cumulative. This means, for the most part, that the chapters build on and add rights to the set of rights afforded to categories of migrants covered by earlier chapters. The Convention contains not only provisions that afford rights to migrants and, to a lesser extent, States (such as the right to decide who can enter and remain in their territory). It also articulates the responsibilities of migrants vis-à-vis States and the rights and responsibilities of different institutions that do not directly respond to a right held by migrants

Linking collisional and accretionary orogens during Rodinia assembly and breakup: Implications for models of supercontinent cycles

Periodic assembly and dispersal of continental fragments has been a characteristic of the solid Earth for much of its history. Geodynamic drivers of this cyclic activity are inferred to be either top-down processes related to near surface lithospheric stresses at plate boundaries or bottom-up processes related to mantle convection and, in particular, mantle plumes, or some combination of the two. Analysis of the geological history of Rodinian crustal blocks suggests that internal rifting and breakup of the supercontinent were linked to the initiation of subduction and development of accretionary orogens around its periphery. Thus, breakup was a top-down instigated process. The locus of convergence was initially around north-eastern and northern Laurentia in the early Neoproterozoic before extending to outboard of Amazonia and Africa, including Avalonia–Cadomia, and arcs outboard of Siberia and eastern to northern Baltica in the mid-Neoproterozoic (~760 Ma). The duration of subduction around the periphery of Rodinia coincides with the interval of lithospheric extension within the supercontinent, including the opening of the proto-Pacific at ca. 760 Ma and the commencement of rifting in east Laurentia. Final development of passive margin successions around Laurentia, Baltica and Siberia was not completed until the late Neoproterozoic to early Paleozoic (ca. 570–530 Ma), which corresponds with the termination of convergent plate interactions that gave rise to Gondwana and the consequent relocation of subduction zones to the periphery of this supercontinent. The temporal link between external subduction and internal extension suggests that breakup was initiated by a top-down process driven by accretionary tectonics along the periphery of the supercontinent. Plume-related magmatism may be present at specific times and in specific places during breakup but is not the prime driving force. Comparison of the Rodinia record of continental assembly and dispersal with that for Nuna, Gondwana and Pangea suggests grouping into two supercycles in which Nuna and Gondwana underwent only partial or no break-up phase prior to their incorporation into Rodinia and Pangea respectively. It was only after this final phase of assembly that the supercontinents then underwent full dispersal