The formation of ice-marginal embankments into ice-dammed lakes in the eastern Puget Lowland, Washington, U.S.A., during the late Pleistocene

Large embankments, typically several kilometers in lateral extent and many tens of meters high, choke the mouths of each alpine valley of the central Cascade Range, Washington State, U.S.A., at or near their junctions with the Puget Lowland. They comprise till and bedded gravel, sand, and silt, aggraded into ice-dammed lakes. The embankments lie within the late-Pleistocene Cordilleran ice-sheet limit and so do not mark the location of the ice-maximum terminus. Reconstruction of the subglacial hydraulic potential field indicates that these ice-dammed lakes would have drained subglacially via spillways located near the junction of each alpine valley and the Lowland. Physical processes tended to stabilize the grounding line for each ice tongue close to its respective spillway location. Because sedimentation rates are highest adjacent to the grounding line, subaqueous sedimentation formed a growing embankment there. In some valleys, subsequent subaerial lake drainage or decay of the active-ice dam resulted in late-stage deposition of deltas or valley trains. This analysis of ice-water behavior is based on physical principles that should be generally applicable to any environment where glaciers terminate against ice-dammed bodies of water.     

The latest vertebrates are the earliest

The teeth, or elements, ofconodonts are among the most important Palaeozoic microfossils. Despite this, the biological relationships of conodonts have long remained enigmatic. Recent evidence of their soft anatomy, and of the ultrastructure of the elements, has finally revealed that they are vertebrates. These discoveries push vertebrate origins firmly back into the Cambrian and add a large cohort of specialists to the ranks of the vertebrate palaeontologists.     

Interlobate ice-sheet dynamics during the Last Glacial Maximum at Whitburn Bay, County Durham, England

This research reconstructs ice-sheet processes operating during the Late Devensian in northeast England. The article assesses the lithostratigraphy of the Devensian glacial tills of Whitburn Bay, eastern County Durham, and presents the first detailed analysis of petrological, geochemical and biostratigraphical data to reconstruct lithostratigraphy, provenance and iceflow pathways. Two Devensian tractions tills (the Blackhall and Horden tills) are separated by a boulder pavement, pointing to a switch in ice-bed conditions and the production of a melt-out lag prior to deposition of the upper traction till, the Horden Till. The Blackhall Till contains Magnesian Limestone, Carboniferous Limestone, Whin Sill dolerite and Old Red Sandstone, suggesting a northwesterly source, probably from the Midland Valley and the Southern Uplands. The Horden Till contains erratics and heavy minerals derived from crystalline bedrock sources in the Cheviot Hills and northeast Scotland. Within the Horden Till are numerous sand, clay and gravel-filled canals incised downwards into the diamicton which are attributed to a low-energy, distributed, subglacial canal drainage system. Coupled with hydro-fractures and the boulder pavement, this suggests that a partially decoupled, fast-flowing ice stream deposited the Horden Till. The uphill, landward direction of ice movement indicates that the ice stream was confined in the North Sea Basin, possibly by the presence of Scandinavian Ice.     

NEW 10BE COSMOGENIC AGES FROM THE VIMMERBY MORAINE CONFIRM THE TIMING OF SCANDINAVIAN ICE SHEET DEGLACIATION IN SOUTHERN SWEDEN

The overall pattern of deglaciation of the southern part of the Scandinavian Ice Sheet has been considered established, although details of the chronology and ice sheet dynamics are less well known. Even less is known for the south Swedish Upland because the area was deglaciated mostly by stagnation. Within this area lies the conspicuous Vimmerby moraine, for which we have used the terrestrial cosmogenic nuclide (¹⁰Be) exposure dating technique to derive the exposure age of six glacially transported boulders. The six ¹⁰Be cosmogenic ages are internally consistent, ranging from 14.9 ± 1.5 to 12.4 ± 1.3 ka with a mean of 13.6 ±0.9 ka. Adjusting for the effects of surface erosion, snow burial and glacio-isostatic rebound causes the mean age to increase only by c. 6% to c. 14.4± 0.9 ka. The ¹⁰Be derived age for the Vimmerby moraine is in agreement with previous estimates forthe timing of deglaciation based on radiocarbon dating and varve chronology. This result shows promise for further terrestrial cosmogenic nuclide exposure studies in southern Sweden.     

Evolution of a Lateglacial mountain icecap in northern Scotland

Finlayson, A., Golledge, N., Bradwell, T. & Fabel, D. 2011: Evolution of a Lateglacial mountain icecap in northern Scotland. Boreas, Vol. 40, pp. 536–554. 10.1111/j.1502‐3885.2010.00202.x. ISSN 0300‐9483. Detailed geomorphological mapping of the Beinn Dearg massif, northern Scotland, was conducted to examine the maximum (Younger Dryas) extent, and earlier interstadial evolution, of an icecap that existed during the Lateglacial period (14.7–11.7 cal. ka BP). Landform evidence indicates a plateau icecap configuration during the Younger Dryas. The interpreted age is supported by new cosmogenic exposure ages and previously reported interstadial sediments beyond the icecap margin. The reconstructed Younger Dryas Beinn Dearg icecap covered 176 km². Equilibrium line altitudes (ELAs) of ～570–580 m were calculated for the icecap as a whole. The empirically reconstructed icecap is compared with recent numerical model simulations. The two methods produce an icecap with a similar configuration; however, differences are apparent in the extent of eastern and western outlets (±1–5 km), and in the spatial variation of ELAs. Results suggest that the numerical simulation overestimates the western and underestimates the eastern icecap extent. We attempt to quantify these differences in terms of icecap mass balance and assess their possible causes. Geomorphological evidence for the pre‐Younger Dryas icecap configuration indicates that the Beinn Dearg massif remained an important source during earlier deglaciation. In contrast, the neighbouring Fannich mountains acted as an ‘unzipping’ zone, and were ice‐free on their northern side by the Allerød (Greenland Interstadial 1c to 1a). Deglaciation continued over the western Beinn Dearg plateau, with the possibility that glaciers remained in some central and eastern catchments prior to (Younger Dryas) icecap (re)growth.     

CHANNING COPE AND THE MAKING OF A MIRACLE VINE*

ABSTRACT. The history of kudzu illustrates the fluidity with which people can redefine their cultural relationship with exotic species. Although much of American society views the fast‐growing Asian vine as a pest, this has not always been the case. During the first half of the twentieth century, individual entrepreneurs and government officials touted kudzu as a “miracle vine” and carried out massive planting campaigns across the southeastern United States. This study traces the changing place of kudzu within southern society from its introduction in the late 1800s to the present. Specific attention is devoted to the role that the gentleman farmer, author, and radio personality Channing Cope played in popularizing the cultivation of kudzu. Cope's promotional activities are interpreted as environmental claims making. Analysis focuses on the metaphors he used in persuading the public of kudzu's supposed benefits. Conducting such an examination advances our general understanding of the historical geography of exotics in America and the importance of human agency and cultural representation in the spread of non‐native organisms.     

The crystalline lunar spherules: Their formation and implications for the origin of meteoritic chondrules

Abstract— Crystalline lunar spherules (CLS) from three thin sections of Apollo 14 regolith breccias (14318,6; 14318,48 and 14315,20) have been examined. The objects have been classified and their abundances, size distributions, bulk compositions, and (where possible) plagioclase compositions determined. By number, 64% consist predominantly of very fine-grained equant plagioclase grains but can also contain larger (～50 μm) feldspar crystals (type X), while 22% contain plagioclase lathes in a fine-grained mafic mesostasis (type Y). Plagioclase in both spherule types displays bright yellow cathodoluminescence that is conspicuous among the blue CL of the normal feldspar of the breccias. Type Z spherules (5%) contain feldspar with blue CL and minor amounts of olivine and pyroxene. Type Q spherules (4%) contain feldspar with yellow CL but in a luminescent mesostasis (of quartz or feldspar?). A few spherules are mixtures of type Y and type X textures. Most type X spherules, and a few type Y spherules, have fine-grained opaque rims. Compound objects were also found and consist of two or more CLS that appear to have collided while still plastic or molten. The CLS are thought to be impact spherules that crystallized in free flight, their coarse textures suggesting fairly slow cooling rates (～ <1 °C/s). The abundance of the CLS resembles that of chondrules in the CM chondrite Murchison, and their cumulative size-frequency distributions are very similar to those of the chondrules in several meteorite classes. The bulk compositions of the CLS do not resemble regoliths at any of the Apollo sites, including Apollo 14, or any of the common impact glasses, but they do resemble the bulk compositions of several lunar meteorites and the impact glasses they contain. The Apollo 14 site is located on a region containing Imbrium ejecta, and we suggest that the CLS derive from the Imbrium impact. Ballistic calculations indicate that only impact events of this size on the Moon are capable of producing melt spherules with the required free flight times and slow cooling rates. Smaller impacts produce glassy spherules and agglutinates. As has been pointed out many times, the CLS have many properties in common with meteoritic chondrules. While much remains unclear, difficulties with a nebular origin and new developments in chondrule chronology, studies of asteroid surfaces and impact ejecta behavior, and the present observations indicate that meteoritic chondrules could have formed by impact.     

A preliminary report on the Stanton Harcourt Channel Deposits (Oxfordshire,England): geological context,vertebrate remains and palaeolithic stone artefacts

A summary is given of the geological, faunal and archaeological information obtained during excavations in the Stanton Harcourt Channel Deposits from 1990 to 1995. The channel deposits underlie the ‘cold-climate’ Stanton Harcourt Gravel Member of the Summertown– Radley Terrace Formation. The Channel sediments are attributed to Oxygen Isotope Stage 7, when the Thames was undergoing down-dip migration and eroding the Weymouth Member of the Oxford Clay (Upper Jurassic), the contemporary Jurassic (Corallian) escarpment being near to Stanton Harcourt at that time. Abundant large vertebrate remains have been recovered, mainly from the base of the Channel deposits, where a cobble and boulder bed rests on thin silt or sand horizons or in scour hollows in the clay bedrock. Smaller bones occur throughout the deposits, which are mainly poorly sorted gravels, but especially at erosive horizons. Several palaeolithic artefacts have been found in the same contexts; many of the bones and some of the artefacts appear not to have been transported far. Although the artefacts cannot be linked directly with the bones, a study of them adds to our knowledge of the Middle Pleistocene human settlement of the Upper Thames Valley. It is of interest that mammoth is abundant as part of the interglacial faunal assemblage, and the significance of this is discussed. The environment clearly included substantial areas of open grassland, although there was also some forest in the vicinity. Evidence appears to be accumulating for important faunal and floral differences between particular interglacial events during the British Middle and Late Pleistocene.