Geomorphology of the Sub-Antarctic Australian Territory of Heard Island-McDonald Island     

KEVIN KIERNAN  ANNE McCONNELL 《The Australian geographer》1999,30(2):159-195

The geomorphology of Heard Island-McDonald Island is primarily the product of close interplay between volcanism, glaciation, and vigorous marine processes in a stormy sub-Antarctic environment. The dominant landform is the strato-volcano Big Ben (2745m), which is the highest mountain on Australian territory outside Antarctica. Other volcanic landforms include scoria cones, domes, open vertical volcanic conduits, lava flows and lava tubes. Volcanic activity is ongoing from the summit of Big Ben, and from Samarang Hill on McDonald Island. Early, but unproven, glacial sediments may exist within the Late Miocene - Early Pliocene Drygalski Formation, which forms a 300m high plateau along the northern coast of Heard Island. Growth of the present glaciers, some of which reach sea level, has been a response to progressive growth of the volcanoes. A variety of erosional and depositional glacial landforms is present, including major lateral moraines and extensive hummocky moraines. Vigorous longshore drift and an abundant sediment supply have produced a large spit at the downdrift end of the island, and formed bars from reworked glacigenic sediment that now impound proglacial estuarine lagoons, some of which have grown rapidly over recent decades as tidewater glaciers have retreated. Integrated study of the volcanic, glacial and coastal sequences offers the possibility of constructing a well-dated record of climate change. Research into the geomorphology, surficial sediments, and contemporary geomorphological processes, including glaciofluvial sediment flux, is also important as an aid to environmental management on land, and to management of the adjacent marine environment.  相似文献   

MAPPING WISCONSIN     

ANNE KELLY KNOWLES 《Geographical review》2000,90(2):277-284

WISCONSIN'S PAST AND PRESENT: A Historical Atlas. By The Wisconsin Cartographers ' Guild , xv and 125 pp.; maps, ills. THE ATLAS OF ETHNIC DIVERSITY IN WISCONSIN. By Kazimierz J. Zaniewski and Carol J. Rosen CULTURAL MAP OF WISCONSIN: A Cartographic Portrait of the State. By David Woodward , Robert C. Ostergren , Onno Brouwer , Steven Hoelscher , and Joshua Hane .  相似文献   

Simulation of atmospheric CO₂ over Europe and western Siberia using the regional scale model REMO     

ANNE CHEVILLARD  UTE KARSTENS  PHILIPPE CIAIS  SÉBASTIEN LAFONT  MARTIN HEIMANN 《Tellus. Series B, Chemical and physical meteorology》2002,54(5):872-894

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Holocene vegetation and climate history on a continental-oceanic transect in northern Fennoscandia based on pollen and plant macrofossils     

ANNE E. BJUNE  H. J. B. BIRKS  HEIKKI SEPPÄ 《Boreas: An International Journal of Quaternary Research》2004,33(3):211-223

Changes in tree-line, mean July temperature (T _jul ) and mean annual precipitation (P _ann ) for the last 10 200 cal. yr BP are reconstructed on the basis of pollen and plant macrofossils preserved in lake sediments from two sites near the present-day tree-line in Troms, northern Norway. Quantitative climate reconstructions are performed using pollen-climate transfer functions based on WA-PLS regression. Early Holocene Betula pubescens forests were gradually replaced by Pinus sylvestris at Dalmutladdo (355 m a.s.l.) starting about 7000 cal. yr BP. The local presence of pine woodland at that time is supported by finds of stomata and plant macrofossils and by high pollen accumulation rates. Until about 4000 cal. yr BP the P. sylvestris tree-line was 250-300 m higher than today, suggesting T _jul about 2.0°C higher than at present. The later part of the Holocene has a cooler and moister climate and an increasing development of mires and fern-rich vegetation, as shown by increases of Sphagnum and fern spores and the re-establishment of B. pubescens woodland. The reconstructed T _jul from the two sites shows similar trends to previously published data, with T _jul 1-2°C warmer between 9500 cal. yr BP and 2000 cal. yr BP T _jul . Maximum T _jul values occur between 8500 and 4500 cal. yr BP, after which there is a gradual decrease in T _jul .  相似文献   

Chronology and paleoenvironments during the late Weichselian deglaciation of the southwest Iceland shelf     

ANNE JENNINGS  JAMES SYVITSKI  LINDA GERSON  KARL GRÖNVOLD  ÁSLAUG GEIRSDÓTTIR  JÓRUNN HARDARDÓTTIR  JOHN ANDREWS  SVEINUNG HAGEN 《Boreas: An International Journal of Quaternary Research》2000,29(3):163-183

Foraminifera, sedimentology, and tephra geochemistry in core 93030-006 LCF from the southwestern Iceland shelf were used to reconstruct paleoenvironments between 12.7 and 9.4 ¹⁴C ka BP. Seismic-reflection profiles place the core in glacial-marine and marine sediments within one meter of the underlying glacial till. Foraminifers in the earliest glacial-marine sediments provide a record of ice-distal conditions and immigration of slope species onto the shelf in association with warm Atlantic water. Meltwater increased during the Allerød under a weakened Atlantic water influence. Arctic conditions began by 11.14 ₁₄C ka BP with an abrupt increase in meltwater and near exclusion of boreal fauna from the shelf. Meltwater diminished in the early Younger Dryas, coinciding with sea-surface cooling between 11.14 and 10.5 ¹⁴C ka BP. A slight warming recorded in the uppermost glacial-marine sediments was interrupted by an inferred jökulhlaup event emanating from glacier ice on the Western Volcanic Zone. Retreat of the ice margin from the sea sometime between c. 10.3 and 9.94 ¹⁴C ka BP coincided with this event. The onset of postglacial marine sedimentation occurred along with increasing evidence of Atlantic water c. 9.94 ¹⁴C ka BP and was interrupted by a short-lived Pre-boreal cooling of the Irminger Current c. 9.91 ¹⁴C ka BP. Conditions similar to those today were established by 9.7 ¹⁴C ka BP.  相似文献   

Numerical simulations of sea and land breezes at high latitudes     

SIGBJØRN GRØNÅS  ANNE DAGRUN SANDVIK 《地球，A辑:动力气象学与海洋学》1998,50(4):468-489

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The bluestone enigma     

GRAHAM & JUDITH JENKINS 《Geology Today》1992,8(4):126-127

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Use of radon for evaluation of atmospheric transport models: sensitivity to emissions     

MOHAN L. GUPTA  ANNE R. DOUGLASS  S. RANDOLPH KAWA  STEVEN PAWSON 《Tellus. Series B, Chemical and physical meteorology》2004,56(5):404-412

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Aerosol particle formation events and analysis of high growth rates observed above a subarctic wetland–forest mosaic     

BIRGITTA SVENNINGSSON  ALMUT ARNETH  SEAN HAYWARD  THOMAS HOLST  REAS MASSLING  ERIK SWIETLICKI  ANNE HIRSIKKO  HEIKKI JUNNINEN  ILONA RIIPINEN  MARKO VANA  MIIKKA DAL MASO  TAREQ HUSSEIN  MARKKU KULMALA 《Tellus. Series B, Chemical and physical meteorology》2008,60(3):353-364

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Depth and controls of Ca-rhodochrosite precipitation in bioturbated sediments of the Eastern Equatorial Pacific, ODP Leg 201, Site 1226 and DSDP Leg 68, Site 503     

PATRICK MEISTER†  STEFANO M. BERNASCONI  IVANO W. AIELLO‡  CRISÓGONO VASCONCELOS  JUDITH A. MCKENZIE 《Sedimentology》2009,56(5):1552-1568

The occurrence of early diagenetic Ca‐rhodochrosite [(Mn,Ca)CO₃] is reported in association with ‘griotte’‐type nodular limestones from basinal settings in the geological record; however, without the comparison of analogous modern examples, the controls on precipitation remain speculative. Here the findings of four layers of primary Ca‐rich rhodochrosite recovered from a modern deep‐sea setting in the Eastern Equatorial Pacific, from bioturbated sediments 300 m below sea floor, are reported (Ocean Drilling Program, Leg 201, Site 1226). The mineralogy is similar to cements in burrows recovered during Deep Sea Drilling Project Leg 68 at Eastern Equatorial Pacific Site 503 and from Ca‐rhodochrosite laminae in sediments of the central Baltic Sea. Petrographic relationships and constant oxygen isotopic compositions in the Ca‐rhodochrosite around 5‰ at all depths indicate a shallow burial depth of formation. The onset of 1‰ heavier oxygen isotope composition of Ca‐rhodochrosite at Site 503, about 30 m below the Pliocene/Pleistocene boundary, further suggests that precipitation occurs in the range of 30 m below sea floor. The approximate depth of formation allowed an approximate empirical fractionation factor for marine Ca‐rhodochrosite to be constrained that strongly differs from previously published theoretical values. Based on the approximate precipitation depth, authigenic Ca‐rhodochrosite forms within the SO₄^2?‐reduction zone. Moderately negative δ¹³C values (around ?3‰) and total organic carbon lower than 2 wt% indicate a relatively low contribution of CO₃^2? from organic C mineralization within the expanded redox zonation in the Eastern Equatorial Pacific. It is suggested that the alkalinity is increased by a rise in pH at focused sites of Mn‐reduction coupled with S^2? oxidation. High concentrations of Mn‐oxide can accumulate in layers or burrows because of Mn‐cycling in suboxic sediments as suggested for the Baltic Sea Ca‐rhodochrosites. This study demonstrates how early diagenetic precipitates document biogeochemical processes from past diagenetic systems.  相似文献