VASCULAR PLANTS OF MOUNTAIN TALUS SLOPES,MT. RAE AREA,ALBERTA, CANADA

The vascular flora of talus slopes in the Mt. Rae area, Canadian Rocky Mountain Front Ranges, is discussed in the context of edaphic and geomorphic conditions. Thirteen talus slopes were sampled systematically for the presence of vegetation, and vascular plants were identified to the species level. Such talus slopes are generally considered relatively sterile and too unstable for the development of distinctive flora. The presence of vegetation is usually taken as an indicator of slope stability. A total of 77 species with boreal and arctic affinities was identified. Most plants display growth forms suitable to the unstable and xeric talus substrate with Schroeter's Schuttstrecker and Schuttdecker forms being most common. Although areal coverage by plants is sparse, a large number of species with morphological characteristics suitable for the talus environment suggests that the presence of plants should not be regarded as an absolute indicator of slope stability. Rather, these plants may represent a long-term equilibrium assemblage characteristic of active talus slopes in a mountain environment.     

Zooplankton distribution and abundance in saline lakes of Alberta and Saskatchewan,Canada

Zooplankton collections were made during 1985, 1986, 1988 and 1989 from 17 lakes in Saskatchewan and 3 in Alberta. Salinity ranged from 2.8 to 269 g L⁻¹ (total filtrable residue). A total of 35 species was present in four taxa: Anostraca (3 species), Cladocera (11), Copepoda (7) and Rotifera (14). Species richness was greatest at salinities <7 g L⁻¹ (15–16 species). Lakes with salinities between 7 and 100 g L⁻¹ generally had 6–8 zooplankton species, while the most saline lakes (>100 g L⁻¹) had 2–5 species. The largest concentrations of zooplankton occurred at <30 g L⁻¹, but some species (Brachionus plicatilis, Hexarthra polyodonta, Artemia franciscana, Diaptomus connexus) were abundant at salinities >50 g L⁻¹. Eurysaline species included the rotifersAsplanchna girodi (3–111 g L⁻¹),Brachionus plicatilis (13–146) andKeratella quadrata (2.8–103).Artemia franciscana (33–269—but absent from Big Quill Lake, 49–82),Daphnia similis (3–104).D. connexus (9–82),Diacyclops thomasi (3–72), andCletocamptus albuquerquensis (17 to 126—but never abundant in the plankton). About half the species were restricted to hyposaline waters (3–20 g L⁻¹), but some (Hexarthra fennica, Moina hutchinsoni, Hexarthra polyodonta) occurred only at intermediate salinities. The latter two species were also only present at high pH values (>9.2). There was a trend of decreasing species richness with increasing salinity. TWINSPAN classification of 94 lake samples (six parameters) based on zooplankton species abundances yielded a dendrogram with 14 ‘indicator’ species characteristic of seven lake groups related partly to a salinity gradient, but with other environmental factors such as water column depth, pH, Secchi disk transparency, water temperature and month sampled also influenced lake separation. *** DIRECT SUPPORT *** A02GG004 00002     

Late-glacial vegetation and environment on the eastern slope foothills of the Rocky Mountains, Alberta, Canada

Stratigraphic pollen analysis done on sediment cores from two sites in the upper North Saskatchewan drainage basin of the eastern slopes foothills of the Rocky Mountains in west central Alberta, Canada combined with sedimentological data provide a local vegetational and environmental history. Radiocarbon AMS dates provide a chronology back to 17960 BP. Reconstruction and interpretation of the local pollen zones includes reevaluation of steppe and grassland as analogs for full- and late-glacial vegetation. Regional vegetation from c. 17960 to 16 100 BP is interpreted as an extremely cold semi-arid Artemisia steppe, the vegetation c. 16 100 to 11 900 BP as an Artemisia-Betula shrubland, and the vegetation c. 11 900–10 200 BP as a Picea woodland, in an environment characterized by consistently arid and windy conditions. This reconstruction emphasizes the significance of aridity, as opposed to simply low temperatures, as the critical factor in determining the late Quaternary vegetation of Alberta.This is the 18th in a series of papers published in this special AMQUA issue. These papers were presented at the 1994 meeting of the American Quaternary Association held 19–22 June, 1994, at the University of Minnesota, Minneapolis, Minnesota, USA. Dr Linda C. K. Shane served as guest editor for these papers.     

Geographers in the U.S. Government in Washington,DC, during World War II

Geographers in Washington, DC, during World War II and the agencies in which they worked are recalled through the naming of geographers engaged in wartime work during this seminal period in the development of the geography profession in the United States. The five agencies then employing the largest number of geographers were the Research and Analysis Branch of the Office of Strategic Services, the Topographic Branch of the Military Intelligence Division of the War Department, the Board of Economic Warfare (later the Foreign Economic Administration), the Board on Geographic Names, and the Office of the Geographer, Department of State. The impacts of this period on individual geographers, the professional organization of geographers, cartography, higher education, and the government are suggested.     

Geographers in the U.S. Government in Washington,DC, during World War II

Geographers in Washington, DC, during World War II and the agencies in which they worked are recalled through the naming of geographers engaged in wartime work during this seminal period in the development of the geography profession in the United States. The five agencies then employing the largest number of geographers were the Research and Analysis Branch of the Office of Strategic Services, the Topographic Branch of the Military Intelligence Division of the War Department, the Board of Economic Warfare (later the Foreign Economic Administration), the Board on Geographic Names, and the Office of the Geographer, Department of State. The impacts of this period on individual geographers, the professional organization of geographers, cartography, higher education, and the government are suggested.     

Tectonic loading, sedimentation, and sea-level changes in the foreland basin of north-west Alberta and north-east British Columbia, Canada

By calculating mass accumulation rates for foreland basin sediments, the changing capacity of the basin can be monitored through time. It has often been assumed that there was a direct link between foreland basin sedimentation and tectonic deformation and lithospheric loading in the adjacent orogenic belt. The results of this study suggest that tectonic deformation is most likely associated with the changing capacity of the basin and the rate at which sediments accumulate within it, However, there appears to be no relation between tectonic deformation and the lithology of sediment which accumulates in the foreland basin. Instead, eustatic sea-level fluctuations appear to have significant control, through their impact on water depth, on the lithology of sediments accumulating in the foreland basin. These relations are evidenced by mass accumulation rates calculated for foreland basin strata in north-west Alberta and north-east British Columbia, Canada.     

Lithospheric flexure as a control on stratal geometry and fades distribution in Upper Cretaceous rocks of the Alberta foreland basin

Facies distributions, stratal geometry and regional erosional bevelling surfaces in Upper Cretaceous (Cenomanian-Santonian) strata of the Alberta foreland basin are interpreted in terms of high-frequency (probably eustatic) relative changes in sea level, superimposed on longer-term basin-floor warping, related to episodic tectonic loading. Thick marine shales correspond to periods of rapid subsidence whereas thin but extensive strandplain sandstones record rapid progradation during slow subsidence. Westward-thickening wedges of coastal plain strata were deposited during initial downwarping of a near-horizontal strandplain, prior to marine transgression. Surfaces of erosional bevelling beneath which between 40 and >160m of strata have been removed extend at least 300 km from the present deformation front and are interpreted to reflect forebulge uplift in the east. Uplift appears to have lagged about 0.25-0.5 Myr behind the onset of accelerated loading. Thin marine sandstones which grade westward into mudstone are interpreted as material winnowed from the crest of the rising forebulge. Subsidence and/or westward migration of the forebulge allowed the sea to flood westward across the eastern flank of the eroded forebulge. The transgressive shoreface cut asymmetric notches which were later blanketed by marine shales which lap out from east to west. The two unconformities which embody the largest erosional vacuity are veneered locally with oolitic ironstone which accumulated in a shallow, sediment-starved setting on the crest of the forebulge. The consistent pattern of erosional bevelling and lap-out of transgressive shales might be interpreted as evidence that the forebulge migrated towards the thrust load over a period of <1 Myr.