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21.
TORE O. VORREN GEOFFREY D. CORNER JENÖ NAGY 《Boreas: An International Journal of Quaternary Research》1981,10(4):477-484.
The following stratigraphy was found at Slettaelva, near Troms (from bottom to top): greenish basal till (unit A), laminated c lay (unit B), fossitiferous basal till (Unit C). Unit A probably derives from an early Weichselin local glaciation, Unit B comprises lacustrine sediments which were apparently deposited in an early Weichselian tundra-like enivironment, Unit C, which contains reworked fossils of moulluscs, palynomorphs and foraminifera, was deposited by a continenntal ice shcet. Amino acid ratios of Mya truncata and plaaeontological evidence indicate that unit Ccontains a mixed fossil assemblage, probably of Eemian and Weichselian interstadial age. 相似文献
22.
RICHARD G. RICHELS THOMAS F. RUTHERFORD GEOFFREY J. BLANFORD LEON CLARKE 《Climate Policy》2013,13(5):409-428
It is becoming increasingly clear that economically efficient climate policies are unlikely to be implemented in the near term. Therefore an analysis is warranted that considers the implications of certain suboptimal transition policies. This analysis constructs a transition scenario based on realistic assumptions about the current trends in policy-making. The transition is examined in the context of varying assumptions about the stringency of the target and the availability of low- or no-carbon energy technologies in the future. In addition to evaluating the effects of suboptimal policies, the transitional analysis offers new insights about the intrinsic uncertainty regarding both the appropriate stabilization target and technology. 相似文献
23.
GEOFFREY S. P. THOMAS A. JOHN SUMMERS 《Boreas: An International Journal of Quaternary Research》1984,13(1):5-12
A series of large-scale glacio-dynamic structures exposed in 10 km of coastal cliff cut through the Screen Hills kame-morainc, Co. Wexford. Ireland, is descrihed. The structures range from simple ovcrfolds to complex multiple thrusts, have a consistent structural trend, and result from marginal deformation by an ice-sheet moving from the NE. The relationship between the structures and other, gcomorphic and stratigraphic components is resolved into a simple model of repeated ice-marginal oscillation during a phase of overall glacial retreat. 相似文献
24.
The evidence for the extent and timing of Weichselian glaciation in Arctic regions shows that: (1) there were no major marine ice domes in the Arctic at 18,000 B.P. but that glaciers were relatively limited in extent; (2) there were no extensive ice shelves at 18,000 B.P. as envisaged by Hughes, Denton & Grosswald(1977); (3) the major periods of glacier expansion were between 125,000 and 80,000 B.P., just prior to 45,000 B.P., and between 11,000 and 8,000 B.P., and thus that glacier fluctuations at the southern margins of the Laurentide and Fennoscandian ice sheets were out of phase with those in the Arctic which advanced during southern interstadials. Phases of glacier advance in the Atlantic sector of the Arctic can be identified in deep sea cores by the peaks in concentration of iceberg-dropped detritus and an increase in sedimentation rates, which are highest when sub-polar water penetrates to the north. The key to the temporal pattern of Arctic glaciation and its association with oceanic changes is given by the intimate association of present-day Arctic glacierisation with the two major low pressure troughs which penetrate the Arctic in the Atlantic sector and in Baffin Bay. The chronology of glaciation in the Atlantic sector is associated with the activity of these troughs and the related oceanic circulation. Cooling of the Arctic due to reduction in solar radiation at the end of the last interglacial, when the pack ice lay north of 75d?N in the Atlantic, produced ideal conditions for Arctic glacier growth, with moisture transported by a strong cyclonic flux into a cooling Arctic from a strong North Atlantic Drift current. A positive feedback loop involving ocean and atmospheric circulation and pack ice, caused movement of the polar front to the south, thus slowly cutting off the supply of moisture to the Arctic. Further cooling at 75,000 B.P. caused a rapid extension of the polar front south of 45d?N, effectively cut off the northward movement of surface currents on the North Atlantic, and produced a strong zonal oceanic and atmospheric circulation which starved Arctic glaciers of nourishment and caused their retreat, and initiated rapid build up of the Fennoscandian and Laurentide ice sheets. Subsequent extensions of Arctic glaciers were associated with limited northward movement of sub-polar water and associated Atlantic depressions. The expansion of glaciers within the Arctic between 11,000 and 8,000 B.P. was associated with the first and diachronous penetration of moisture into a still cool Arctic during decay of the two great ice sheets. 相似文献
25.
ABSTRACT. The purchase and subsequent demolition of Cheshire, Ohio‐located in the shadow of the General James M. Gavin Power Plant‐has attracted national attention. According to a New York Times report, “the deal … is believed to be the first by a company to dissolve an entire town.” In this article we consider historical precedents for the case, explore the thirty‐year history of community‐plant relations in Cheshire, and recount the series of incidents that ultimately led to the town's sale. We discuss the impact that the town's sale has had on the local community and the larger implications of American Electric Power's actions. 相似文献
26.
Glacial history of the Spitsbergen archipelago and the problem of a Barents Shelf ice sheet 总被引：2，自引：0，他引：2
The popular concept of a Late Weichselian ice sheet covering the Barents Shelf and confluent with the Scandinavian and Russian ice sheets is based primarily on the 6500 B.P. isobase which rises to the east over Spitsbergen, and to the west over Franz Joseph Land. Analysis of uplift curves from the Spitsbergen archipelago shows, however, that the strongest early Holocene uplift occurs over northeastern Spitsbergen and eastern Nordaustlandet, falling both to east and west, and that the centre of uplift migrates to the southeast during the Holocene. Direct evidence of glacier fluctuation indicates an important Billefjorden Stage of glaciation at about 11,000 to 10,000 B.P., part of whose extent can be defined by moraines and by abrupt changes in the marine limit. The dominant ice masses of the Billefjorden Stage seem to have formed over eastern Spitsbergen, Edgeøya, Barentsøya and southern Hinlopenstretet, and it is the decay of this ice mass which is primarily responsible for the pattern of early Holocene uplift. Stratigraphic evidence suggests the absence of an important glacial event at 18,000–20,000 B.P., but an important phase of Spitsbergen-centred glaciation at about 40,000 B.P., and a glacial phase at 80,000–120,000 B.P. It is suggested that many raised beach sequences outside the Billefjorden readvance show an upper sequence related to deglaciation at about 40,000 B.P., and a lower, Holocene sequence related to decay of the Billefjorden ice. The anomalous pattern of late Holocene uplift may be related to restrained rebound produced by regeneration of ice on the main islands of the archipelago and unrestrained rebound on Hopen and Kong Karls Land, which were incapable of sustaining large ice masses of their own. A pattern of LateGlacial climatic circulation which may have produced ice masses on the east coast of Spitsbergen, west coast of Novaya Zemlya and north coast of Russia is suggested. It is also suggested that this pattern of glaciation produced features which have been wrongly interpreted as evidence of a Barents ice sheet. 相似文献
27.
GEOFFREY RUSSELL COOPE JENS BÖCHER 《Boreas: An International Journal of Quaternary Research》2000,29(1):26-34
The freshwater sediments exposed on the cliffs at Nørre Lyngby northern Jutland has long been a classical locality for the study of Danish Quaternary geology, palaeontology and archaeology. These deposits date from the latter part of the Allerød period (i.e. G I-1). Samples for insect analysis have been taken from both the northern and southern exposures of these deposits. Ninety-five- taxa of Coleoptera (beetles) were obtained, of which 69 could be named to species. Of the latter, 23 are not found living in Denmark today. Most of these are still living in northern Fennoscandia but one species is now confined to Mongolia. These assemblages have enabled a detailed picture of the local environment to be reconstructed, showing that the basin-like profile of the deposits represents a section through a channel with slowly moving water. It has been possible to quantify the thermal climate of the time using the Mutual Climatic Range method indicating that mean July temperatures were about 10°C and mean January temperatures were about – 12°C. These figures are considered in the context of Lateglacial climatic reconstructions obtained from coleopteran assemblages elsewhere in northwestern Europe. 相似文献
28.
GEOFFREY LEMDAHL 《Boreas: An International Journal of Quaternary Research》1988,17(2):265-266
An insect fauna in a peat layer from Lake Bysjön, South Sweden, 14 C-dated to 11,200 ± 100 B. P. is described. The recorded insects indicate that the peat is of terrestrial origin and that it was formed in a subarctic environment. 相似文献
29.
GEOFFREY L. BUCKLEY 《Geographical review》1998,88(2):175-198
ABSTRACT. The physical environment of the George's Creek Valley in western Maryland was altered dramatically during the late nineteenth and early twentieth centuries, as coal mining and associated activities expanded and intensified. Although mineral extraction was the chief agent of change, forest and water resources were also affected by other industrial and commercial activities, as well as by the region's growing population. Examining the environmental alteration that took place in the valley, this work also considers attitudes and motivations that contributed to the transformation. 相似文献
30.