Late Pleistocene glacial history of Jameson Land, central East Greenland, derived from cosmogenic 10Be and 26Al exposure dating

Previous work has presented contrasting views of the last glaciation on Jameson Land, central East Greenland, and still there is debate about whether the area was: (i) ice-free, (ii) covered with a local non-erosive ice cap(s), or (iii) overridden by the Greenland Ice Sheet during the Last Glacial Maximum (LGM). Here, we use cosmogenic exposure ages from erratics to reconcile these contrasting views. A total of 43 erratics resting on weathered sandstone and on sediment-covered surfaces were sampled from four areas on interior Jameson Land; they give ¹⁰Be ages between 10.9 and 269.1 kyr. Eight erratics on weathered sandstone and till-covered surfaces cluster around ∼70 kyr, whereas ¹⁰Be ages from erratics on glaciofluvial landforms are substantially younger and range between 10.9 and 47.2 kyr. Deflation is thought to be an important process on the sediment-covered surfaces and the youngest exposure ages are suggested to result from exhumation. The older (>70 kyr) samples have discordant ²⁶Al and ¹⁰Be data and are interpreted to have been deposited by the Greenland Ice Sheet several glacial cycles ago. The younger exposure ages (≤70 kyr) are interpreted to represent deposition by the ice sheet during the Late Saalian and by an advance from the local Liverpool Land ice cap in the Early Weichselian. The exposure ages younger than Saalian are explained by periods of shielding by non-erosive ice during the Weichselian glaciation. Our work supports previous studies in that the Saalian Ice Sheet advance was the last to deposit thick sediment sequences and western erratics on interior Jameson Land. However, instead of Jameson Land being ice-free throughout the Weichselian, we document that local ice with limited erosion potential covered and shielded large areas for substantial periods of the last glacial cycle.     

CAPTAIN BRITAIN AND THE NARRATION OF NATION*

Captain Britain Weekly (1976–1977) was the first comic book specially created for the British market by New York‐based Marvel Comics. The title character was created as an analogue to Captain America, the legendary American nationalist hero of the so‐named comic book, but with key differences meant to resonate in the British context. I utilize visual and textual discourse analysis to study the narrative and imagery used to introduce this character to British comics fans, and I discuss readers' letters to the editor to evaluate audience response to the character and story lines. Attention is drawn to the hero's origin, which fuses science and magic to construct a paradoxically primordial, yet modern, British identity. Villains in these story lines provide hints about “un‐British” behavior and provide lessons for young readers, with direct moral connections to, and contrasts with, the narratives found in Captain America.     

Anhydrous Partial Melting of a Fertile and Depleted Peridotite from 2 to 30 kb and Application to Basalt Petrogenesis

Reversal experiments have been performed to check the methodof Jaques & Green (1980) to determine equilibrium partialmelts from peridotite compositions. Reversals of the Jaques& Green (1980) calculated equilibrium partial melt (CEPM)compositions have been carried out in two ways: (1) By runningCEPM compositions at original P and T conditions and testingfor multiple saturation in residual phases of the original experiments.(2) By sandwich/mixed experiments using the CEPM compositionplus peridotite (either Hawaiian pyrolite or Tinaquillo lherzolite). The glass (liquid) compositions from the first series of experimentsshow that the CEPM compositions of Jaques & Green (1980)are too olivine-rich. The glass (liquid) compositions from thesecond series of experiments define new olivine+orthopyroxene?clinopyroxenecotectics in a molecular normative tetrahedron. The new cotecticsplot towards the Qz apex of the tetrahedron, away from the cotecticsdefined by the CEPM compositions of Jaques & Green (1980).Partial melt compositions have also been determined at 20 and30 kb, using both the sandwich technique and the approach bymodal analysis and mass balance. The results of the experimental study are used to evaluate thepetrogenesis of mid-ocean ridge basalts, Hawaiian tholentesand primary magmas in intraoceanic convergent margin settings.     

WHEN THE URBAN FRINGE IS NOT SUBURBAN*

Research on the history of suburbs tends to either disregard the fringe of urban development or locate it beyond the city limits. In this article I argue that compounding fringe and suburban development misrepresents the real differences between the two. I then examine the metropolitan regions of three major U.S. cities‐Baltimore, Buffalo, and Saint Louis in 1880 for evidence of how they differed. A consistent difference emerged between the residents of the suburban districts of a city and those of the presumed location of the fringe.     

Late Quaternary palaeoenvironment of northern Guatemala: evidence from deep drill cores and seismic stratigraphy of Lake Petén Itzá

Long sediment cores were collected in spring 2006 from Lake Petén Itzá, northern Guatemala, in water depths ranging from 30 to 150 m, as part of an International Continental Scientific Drilling Program project. The sediment records from deep water consist mainly of alternating clay, gypsum and carbonate units and, in at least two drill sites, extend back >200 kyr. Most of the lithostratigraphic units are traceable throughout the basin along seismic reflections that serve as seismic stratigraphic boundaries and suggest that the lithostratigraphy can be used to infer regional palaeoenvironmental changes. A revised seismic stratigraphy was established on the basis of integrated lithological and seismic reflection data from the basin. From ca 200 to ca 85 ka, sediments are dominated by carbonate‐clay silt, often interbedded with sandy turbidites, indicating a sediment regime dominated by detrital sedimentation in a relatively humid climate. At ca 85 ka, an exposure horizon consisting of gravels, coarse sand and terrestrial gastropods marks a lake lowstand or partial basin desiccation, indicating dry climate conditions. From ca 85 to ca 48 ka, transgressive carbonate‐clay sediments, overlain by deep‐water clays, suggest a lake level rise and subsequent stabilization at high stage. From ca 48 ka to present, the lithology is characterized by alternating clay and gypsum units. Gypsum deposition correlates with Heinrich Events (i.e. dry climate), whereas clay units coincide with more humid interstadials.     

Supporting evidence from the New York drumlin field that elongate subglacial bedforms indicate fast ice flow

Although drumlins and other subglacial bedforms are well-studied features, controls on their formation and morphometry have remained elusive. Of current interest is the hypothesis that elongate bedforms (length:width ratios ≥ 10) indicate fast ice flow, and perhaps the location of past ice streams. This hypothesis is explored by analysing drumlins from the New York State drumlin field. A subset of 548 drumlins between Oneida Lake and Lake Ontario was digitized using 10-m grid cell digital elevation data. Because bedform elongation is greatest along the axis of a reconstructed lobe and increases down flowline, elongate bedforms are best explained by fast ice flow. The swath of elongate bedforms between lakes Ontario and Oneida, the boundaries of which do not coincide with topography, may signify the location of an ice stream during deglaciation.