ISSN:1045-6740    

DOI:10.1002/ppp.3430020202

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractElectrical loggings for permafrost characterization in cryogenic mounds in Nunavik, Québec. Geophysical methods are useful tools to improve the understanding of physical phenomena related to permafrost. Induced polarization logging has not been commonly used yet for permafrost studies. In this study, electrical contact is insured through regularly spaced metallic electrodes vertically inserted in the ground along a multiconductor cable. Thermistors located at the same depths yield a temperature profile in the soil. Both apparent electrical resistivities and apparent electrical chargeabilities are logged. A dipole‐dipole configuration is used. The spacings between the electrodes of a dipole vary from 0.1 to 1 m. Two study areas (Kangiqsualujjuaq in Ungava Bay and Umiujaq in Hudson Bay) in northern Quebec are investigated; they are both located at the tree line and have a mean annual air temperature of about −5.6ºC. The base of permafrost is easily detected through the high contrasts in apparent electrical resistivity and apparent chargeability between frozen and unfrozen soils. Ice‐rich permafrost is characterized by high resistivity values and close to zero chargeability values, while ice‐poor permafrost is characterized by intermediate resistivity and low chargeability values. In unfrozen zones, low apparent resistivity and high apparent chargeability (positive or negative) values are encountered. These guidelines for the interpretation of the logs allow a categorization of different subhorizontal zones in permafrost. Ice‐rich zones do occur near the surface and at the base of permafrost. A low ice content zone is usually sandwiched between these two zones. In this central zone, the growth of ice lenses is limited due to the small intake of water which is damned by the icy zones abov

ISSN:1045-6740    

DOI:10.1002/ppp.3430020203

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractIn situ measurements of solifluction and permafrost creep on several low‐angled slopes near Rea Point, Melville Island, emphasize that there is no clear relationship between the two processes. Solifluction and permafrost creep are essentially independent in time (e.g. early summer versus late summer dominance) and mechanics (e.g. the flow of saturated sediments versus the plastic flow of ice‐rich sediments). Such differences are also likely to alter the relative importance of each of these mass‐wasting processes on a

ISSN:1045-6740    

DOI:10.1002/ppp.3430020204

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe heating of rock by insolation during subzero air temperatures may cause thermal stresses within that rock. The values of Δt may be such that fracturing due to thermal shock may occur. The uneven heating of a rock body may cause buttressing of the heated faces such that thermal stresses are accentuated. Upon removal of the heat source, rapid cooling may occur and values of Δt may be sufficient to cause thermal shock.Replications of these thermal stresses may lead to fatigue and failure. The zone within which these stresses may occur is also one within which freeze‐thaw can take place if water is present. It is suggested that thermally induced fracturing of rock in cold environments may be a significant but underrated process. Thermal results of laboratory simulation experiments are presented during which values of Δt =>500ºC/h occurred for short pe

ISSN:1045-6740    

DOI:10.1002/ppp.3430020205

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractA field experiment at 3,350 m.a.s.l. in the Colorado Alpine was initiated in 1959, to investigate frost sorting. Four plots, of varying grain‐size composition, were used to test whether sorting by freeze‐thaw activity could be related to the percentage of soil particles finer than 0.074 mm and whether there was a characteristic grain size at which lateral and/or vertical sorting could be expected. Re‐examination of the site in 1984 indicated that macrofabrics, microfabrics, soil physical properties and surface clast distributions showed no evidence of large‐scale sorting. Critical conditions for the onset of pore water convection, as a mechanism for the initiation of sorting, could occur in only two of the test soils (A and B), and permeability in the third (C) was too low to allow instability. Soil convection is also unlikely, owing to the coarse, freely drained nature of the tes

ISSN:1045-6740    

DOI:10.1002/ppp.3430020206

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThis paper reviews and discusses the main mechanisms involved in cryoturbation processes and patterned ground. The arguments are based upon field, thermal, moisture and micromorphological data in relation to cryogenic fabric stability and local hydraulic conditions. Differential frost heaving appears to be the main mechanism of cryoturbation, but its action can be helped by cryostatic pressures, by differential swelling and probably also by load casting in poorly drained sites. Differential frost heaving can be emphasized if organics are present. Frost‐susceptibility gradients provide an understanding of the geometry of deformation

ISSN:1045-6740    

DOI:10.1002/ppp.3430020207

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe sedimentology and stratigraphy of a stratified slope deposit in central Pennsylvania together with existing pollen data and global climate simulations are used to develop a model for stratified slope deposition within the context of a waxing and waning Late Wisconsinan periglacial climate. The deposit consists of well‐stratified beds of platy, subangular shale chips ranging in size from very fine to very coarse gravel and is characterized by two facies: a matrix‐supported facies and a clast‐supported facies. Mechanical breakdown of bare, highly fractured shale bedrock by frost shattering and freeze‐thaw activity in a periglacial environment in front of the Late Wisconsinan glacial boundary provided an abundant and continuous sediment supply. Gelifracts were transported from bedrock source areas to depositional sites along valley side‐slopes by sheetwash and debris flow processes, creating an inclined (10º), aggradational surface of low relief. Surface runoff was derived from snow melt and rainfall onto impermeable frozen ground and bedrock surfaces. The cyclic nature and timing of deposition indicate that sediment was produced and transported immediately prior to and after the Late Wisconsinan glacial maximum. The Late Wisconsinan glacial maximum was characterized by permafrost conditions with reduced sediment supply and erosional truncation of the stratified slope deposit. Frost cracks, ice wedges and soil wedges developed on an unconformity within the deposit during the glaci

ISSN:1045-6740    

DOI:10.1002/ppp.3430020208

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

ISSN:1045-6740    

DOI:10.1002/ppp.3430020209

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractAnalyses of the gas composition of bubbles in the massive ice at Ice Mountain, made for the first time, enable one to conclude that the origin of ice is glacial.O2, H2, CO2, N2, He and CH4were determined. Our genetic proof is based on the principally different bio‐ and chemical gas contents in intrasedimental and surface ice. That is why we also deduce the data on the ice of clear genesis: modern glaciers and injection ice.Gas composition seems to be an important criterion of ice genesis and this method should be applied to other massive ice bodies of unknown origi

ISSN:1045-6740    

DOI:10.1002/ppp.3430020210

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

ISSN:1045-6740    

DOI:10.1002/ppp.3430020211

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY