Glacier Lobes Research Articles

Paleomagnetism and its Relationship to Till Deposition

Field observations and theoretical studies on temperate glaciers suggest that there is a layer of water at the ice–sediment interface. If this condition existed under continental glaciers it is reasonable to assume that rock and mineral particles were released from the base of the ice through a water or slurry medium.In order to test this hypothesis, samples of clay till from Port Alma, Ontario, were tested and shown to have a strong component of detrital remanent magnetization (DRM) which resists alternating field demagnetization. The possibility that the remanence alignment was caused by glacier movement has been ruled out by anisotropy of magnetic susceptibility measurements. Thus the results demonstrate that a water or slurry layer existed at the base of continental glaciers at the time of till deposition. The basal water layer may explain the very rapid advance of the glacier lobes through the basins of the Great Lakes. The paleomagnetic data and available radiocarbon dates suggest that the till at Port Alma was deposited in a relatively short period of about 100 to 400 yr. The potential usefulness of DRM in clay-rich tills for stratigraphic studies is being further investigated.

Periodic Surge Origin of Folded Medial Moraines on Bering Piedmont Glacier, Alaska

Abstract The vast Bering piedmont glacier, which has large folds in the medial moraines in its terminal lobe, recently experienced two surges with a combined ice displacement of as much as 13 km. Vertical aerial photographs taken before and after the surges disclose the direction and magnitude of ice flow in various parts of the piedmont lobe. The ice moved toward the terminus and expanded in a normal, radial pattern with no evidence of unusual shearing that would result in the formation of large folds. Many surging glaciers display repeated lateral displacements in their medial moraines which result from periodic surging of the main glacier past non-surging tributaries. Moraines of Bering Glacier display small periodic irregularities of this nature. The large “accordion” folds in the moraines in the piedmont lobe are judged to be due to the combined effects of compressive flow and lateral or transverse expansion of these previously formed irregularities. The initially small pre-existing perturbations in the moraines are simply spread laterally and shortened radially into large folds as the ice spreads out. A very large debris band composed of repeatedly folded medial moraines extends across the center of the Bering Glacier lobe. These remarkable folds are thought to result from the deformation of surge-related irregularities in medial moraines as they pass through the zone of intensive shear near the glacier’s margin.

Periodic Surge Origin of Folded Medial Moraines on Bering Piedmont Glacier, Alaska

AbstractThe vast Bering piedmont glacier, which has large folds in the medial moraines in its terminal lobe, recently experienced two surges with a combined ice displacement of as much as 13 km. Vertical aerial photographs taken before and after the surges disclose the direction and magnitude of ice flow in various parts of the piedmont lobe. The ice moved toward the terminus and expanded in a normal, radial pattern with no evidence of unusual shearing that would result in the formation of large folds. Many surging glaciers display repeated lateral displacements in their medial moraines which result from periodic surging of the main glacier past non-surging tributaries. Moraines of Bering Glacier display small periodic irregularities of this nature. The large “accordion” folds in the moraines in the piedmont lobe are judged to be due to the combined effects of compressive flow and lateral or transverse expansion of these previously formed irregularities. The initially small pre-existing perturbations in the moraines are simply spread laterally and shortened radially into large folds as the ice spreads out.A very large debris band composed of repeatedly folded medial moraines extends across the center of the Bering Glacier lobe. These remarkable folds are thought to result from the deformation of surge-related irregularities in medial moraines as they pass through the zone of intensive shear near the glacier’s margin.

Ice margin features in the Julianehåb District, South Greenland

The present report deals with the extension of the ice margin deposits in the Julianehåb district, South Greenland. An attempt is made to establish a Holocene chronology for the ice margin deposits within the region on the basis of their association with raised marine shorelines, combined with a determination of fluctuations of the glaciation limits of the individual stages in Holocene times. As the Narssarssuaq region in the north-eastern part of the district contains numerous extensive ice deposits, this region is treated in more detail than the other localities within the district. On the basis outlined above, it is attempted to establish a relative chronology for the ice margin deposits in the Narssarssuaq region. The remaining deposits within the district are then tentatively incorporated in the chronological scheme for the Narssarssuaq region. After the deglaciation of the district during the last phases of the Wisconsin, four periods of stagnation or readvance of the glacier lobes and the ice caps (four "stages") seem to have given rise to the formation of ice deposits. The earliest of these stages is the Niaqornakasik stage (older Dryas??), succeeded by the Tunugdliarfik stage (probably younger Dryas), the Narssarssuaq stage (probably Roman time), and the maximum extension of the ice in historie times (ca. 1750-1900 A.D.). The variation in the volume of the ice coverings (the inland ice and the Julianehåb ice cap) during the period from the Tunugdliarfik stage to the present day is studied. The superficial conditions of the ice covering above an altitude of ca. 1,700 m do not seem to have altered much since the Tunugdliarfik stage. Finally, deposits from former ice-dammed lakes in the Narssarssuaq region are treated. All the deposits from such lakes found here seem to show that all the lakes at the glacier front had a maximum height of the water level of 120-150 m. This is in accordance with J.W. Glen's theory of subglacial outbursts of ice-dammed lakes.

Glacial geology of Grand Coulee Dam, Washington

Research Article| May 01, 1939 Glacial geology of Grand Coulee Dam, Washington RICHARD FOSTER FLINT; RICHARD FOSTER FLINT Search for other works by this author on: GSW Google Scholar WILLIAM H. IRWIN WILLIAM H. IRWIN Search for other works by this author on: GSW Google Scholar Author and Article Information RICHARD FOSTER FLINT WILLIAM H. IRWIN Publisher: Geological Society of America Received: 23 Dec 1938 First Online: 02 Mar 2017 Online Issn: 1943-2674 Print Issn: 0016-7606 © 1939 Geological Society of America GSA Bulletin (1939) 50 (5): 661–680. https://doi.org/10.1130/GSAB-50-661 Article history Received: 23 Dec 1938 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation RICHARD FOSTER FLINT, WILLIAM H. IRWIN; Glacial geology of Grand Coulee Dam, Washington. GSA Bulletin 1939;; 50 (5): 661–680. doi: https://doi.org/10.1130/GSAB-50-661 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Sections of the fill in Columbia canyon near Grand Coulee Dam, together with the stratigraphy and morphology of related features downstream, record the expansion and later shrinkage of the Okanogan glacier lobe during the last glaciation. Three stratigraphic zones are recognized: (1) A Basal Sequence of lacustrine fines inter-bedded with fluvial sediments, recording oscillatory ponding of the Columbia River as the glacier dammed it downstream. At first the lake was shallow and drained west around the ice margin. Later it was more effectively dammed, deepened, and forced to discharge south through Grand Coulee. (2) A Till Zone, recording the arrival of ice, with fluctuations, at Grand Coulee Dam during the glacial climax. (3) Later deposits stratigraphically (but not everywhere vertically) overlying the Till Zone, recording oscillatory deglaciation accompanied by transition from lacustrine to fluvial conditions.The San Poil glacier lobe entered the lake-filled Columbia canyon at Keller Ferry, 15 miles upstream from Grand Coulee Dam, and contributed sediment to the lake. The maximum of this lobe appears to have been approximately contemporaneous with the maximum of the neighboring Okanogan lobe.While residual ice was still present locally in Columbia canyon downstream, drain-age abandoned Grand Coulee and resumed its former (and present) course. Thereafter, grading of the long profile of Columbia River proceeded both by erosion of the lake fill and by deposition in depressions partly of ice-block origin and was marked by at least one delay recorded by a particularly conspicuous stream terrace. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.