COSMOGENIC 10BE-AGES FROM THE STORE KOLDEWEY ISLAND, NE GREENLAND

Earlier work in northeast Greenland has suggested a limited advance of the Greenland Ice Sheet during the Last Glacial Maximum (LGM). However, this concept has recently been challenged by marine geological studies, indicating grounded ice on the continental shelf at this time. New ¹⁰Be‐ages from the Store Koldewey island, northeast Greenland, suggest that unscoured mountain plateaus at the outer coast were covered at least partly by cold‐based ice during the LGM. It is, however, still inconclusive whether this ice was dynamically connected to the Greenland Ice Sheet or not. Regardless of the LGM ice sheet extent, the ¹⁰Be results from Store Koldewey add to a growing body of evidence suggesting considerable antiquity of crystalline unscoured terrain near present and Pleistocene ice sheet margins.     

NOTE ON THE DETAILED ABLATION STUDIES OF 1959 AND 1962 ON THE GREAT ALETSCH GLACIER

Abstract

Stream channel development in response to the eruption of Mount St. Helens on 18 May 1980, resulted in some of the largest sediment yields documented anywhere on earth. Development of new channels on the 2.7 km³ debris-avalanche deposit in the North Fork Toutle River caused net erosion of as much as 1.3 x 10⁵ t km^?2 annually. Development of these channels followed a four-stage sequence of channel initiation, channel incision with relatively constant width-to-depth ratio, channel widening accompanied by aggradation, and channel widening accompanied by scour-and-fill with little change in average channel elevation. These channels remain unstable both in width and elevation. Lahars affected channel and valley morphology on all flanks of the volcano. Steep, upstream reaches generally incised and widened during the first year following the eruption and aggraded during the following three years. Gently sloping downstream reaches aggraded and widened during the first year and incised during the following three years. The most rapid adjustments occurred during the first two winters following the eruption. The principal effect of the blast on channels throughout the 550 km² devastated area was the subsequent rapid delivery of sand- and silt-size sediment eroded from hillslopes. Channels aggraded during early storms of the 1980–1981 winter but incised during later storms the same winter. Subsequent channel enlargement was constrained by logs deposited in channels by the blast and by post-1980 shallow debris slides. Since 1984, instability and sedimentation in laharand blast-affected channels have been within the range of pre-1980 levels.     

Phytoplankton and chlorophyll a relationships with ENSO in Prydz Bay,East Antarctica

The historical data of phytoplankton and chlorophyll a(Chl a)(1990–2002)obtained during the Chinese National Antarctic Research Expedition(CHINARE)in the Prydz Bay have been integrated.The results showed that the temperature,salinity,nutrients,and oxygen of seawater changed when El Nino/La Nina occurred.The variation of biological communities reflected the response of ecosystem to environmental changes.During El Ni?o period,Chl a concentration and phytoplankton community structure changed significantly,and the relative proportion of diatoms increased while dinoflagellates decreased.During La Ni?a period,the proportion of diatoms decreased,but the golden-brown algae and blue-green algae increased significantly.The variation of phytoplankton population directly affected the biodiversity of the bay,which were also quite sensitive to the marine environment changes.Meanwhile,the satellite remote sensing data of 2002–2011(December–March)have been used to study the temporal connection change of Chl a and phytoplankton in the Prydz Bay.We found that there were significant differences in the monthly variation characteristics of satellite remote sensing Chl a and sea surface temperature(SST),which had some links with sea ice melting and El Ni?o/La Ni?a events.We found that the start time of bloom advanced,lagged or synchronized with the changes of the SST,and we also found the occurrence time of phytoplankton bloom corresponded with the sea ice melting inner bay.To some extent,this study will help us understand the relationships between ENSO events and the phytoplankton bloom in the Southern Ocean.     

Rural Self-Reliance in Bondolfi, Zimbabwe: the role of beekeeping

Community-based economic self-reliance has become critical in many African countries because of the severity of prevailing soci-economic and environmental constraints. Concerns over food security have encouraged a re-evaluation of the importance of indigenous technical knowledge. This study examines a rural area in Zimbabwe where members of the local community have established a successful beekeeping association to improve their livelihoods. The history of the initiative, its broader impact on the community and the role played by external facilitation feature in the study.     

Palaeokarst-influenced depositional and diagenetic patterns in Upper Permian carbonates and evaporites, Karstryggen area, central East Greenland

The Karstryggen area of eastern Greenland represents the western edge of sedimentation in the Jameson Land Basin, an arm of the northern Zechstein seaway. Upper Permian strata of this area were deposited as two major sequences. The first marine incursion transgressed largely peneplaned Lower Permian strata and deposited thin, paralic conglomerates, sandstones and shales (the Huledal Formation) followed by a thick package of carbonates and evaporites (the Karstryggen Formation). Although the Karstryggen Formation represents the transgressive maximum of this sequence, it contains only marginal or restricted marine strata, including micritic, stromatolitic and peloidal carbonates and thick, but localized, bedded gypsum deposits. These lithofacies indicate that relatively arid climates prevailed in this basin, as in most of the Zechstein region. A major regression, associated with a change to a more humid climate, terminated Karstryggen sedimentation. Pre-existing evaporites and carbonates underwent diagenetic alteration, including widespread calcitization and dissolution of gypsum. More importantly, topographic relief in excess of 120 m was generated by fluvial drainage systems and karstic sinkholes. A second marine incursion, accompanied by a return to a semi-arid climate, drowned this high relief topography, producing a complex sequence of strata (the Wegener Halvø Formation) in which sedimentation was greatly influenced by the rugged underlying terrain. Marine cemented algal-molluscan grainstones draped pre-existing palaeotopography during the initial stages of flooding. Continued drowning led to differential sedimentation on ‘highs’ and in ‘lows’. Oolitic and bryozoan-brachiopod grainstones formed as shoals on the crests of most prominences, whereas shales, conglomeratic debris flows, evaporites, or oolitic turbidites were deposited in the lows. More restricted sedimentation took place in the westernmost areas which lay closest to the mainland shoreline and were situated to the west of a palaeotopographic ridge. There, oolitic, stromatolitic and evaporitic strata were deposited under hypersaline conditions indicative of a return to more arid climatic conditions. Three subcycles mark smaller scale relative changes of sea level that occurred during deposition of the Wegener Halvø Formation; they are delimited by regional surfaces with moderate relief (5–20 m) developed during subaerial exposure. Widespread diagenetic changes, including leaching of aragonitic grains, dissolution/collapse brecciation of evaporites and meteoric calcite cementation, occurred in association with these smaller scale sequence boundaries, again reflecting climatic oscillations. Relative sea level fluctuations, coupled with regional climate changes, played a dominant role in determining both depositional and diagenetic relations in these strata. These features undoubtedly extend into subsurface parts of this basin as well as into yet unexplored areas of the northern Zechstein Basin and Barents Shelf, and may have economic significance for the localization of hydrocarbons.     

Geochemistry of carbonate cements in the Sag River and Shublik Formations (Triassic/Jurassic), North Slope, Alaska: implications for the geochemical evolution of formation waters

Carbonate cements (calcite, siderite, dolomite, and ankerite) formed throughout the diagenetic history of the Sag River and Shublik Formations. The trace element and isotopic geochemistry of these cements varies as a function of the timing of precipitation. Earliest calcites, formed prior to significant compaction of the sediment, are relatively enriched in Mg (up to 4·4 mol%), and have ⁸⁷Sr/⁸⁶Sr values (mean = 0·707898) compatible with the original marine pore waters. Later calcites are relatively Fe-rich (up to 5·0 mol%) and are characterized by increasing ⁸⁷Sr/⁸⁶Sr values (up to 0·712823) and Sr content with decreasing age. The Fe content of zoned siderite and dolomite/ankerite rhombs increases towards the outside of the rhombs (i.e. increasing Fe content with decreasing age). These geochemical variations appear principally to result from changes in pore-water chemistry during diagenesis. The increase in ⁸⁷Sr/⁸⁶ Sr and Sr content of the cements is most likely due to interaction between pore waters and ⁸⁷ Sr-rich clay and possibly feldspar in Ellesmerian mudrocks (whole rock ⁸⁷Sr/⁸⁶ Sr signatures for the mudrocks are > 0·716). Pore-water Fe²⁺ concentration was probably controlled by diagenetic alterations involving Fe-bearing minerals (e.g. pyrite precipitation). A reconnaissance examination of carbonate cements in the overlying Kingak Shale indicates that similar alterations occurred in the Kingak. The low δ¹⁸ O value of some calcite cements (-11·96% PDB) suggests that an influx of meteoric water may have occurred in the mid-Neocomian, though the low value could also result from an abnormally high geothermal gradient associated with mid-Neocomian rifting.     

Mountain Biking in the Manawatu Region: Participants, Perceptions, and Management Dimensions

The increase in the number of mountain bikers world‐wide has raised a number of issues associated with impacts and appropriate management strategies. Studies in the USA, UK and New Zealand have indicated a growing concern with environmental impacts, demonstrated attitudes of other recreationalists to mountain bikers and identified a number of management issues. This article presents the findings from field research conducted during the southern summer of 1997/8. The research was carried out in association with the Palmerston North City Council (PNCC) and the Manawatu Mountain Bike Club. The aims of the research were to investigate the demographics of mountain bikers and related management issues. Key findings of the field research were that: access to mountain biking opportunities was a problem; information provision was poor; there was conflict between user groups; there was a lack of agreement on whether there should be dedicated or multi‐use tracks. The article discusses how the research findings have been used to assist in the creation of an outdoor recreation and tourism strategy for Palmerston North. A model for managing recreation /tourism activities is also suggested.