Asymmetric Valley Research Articles

Localities visited on Excursions during the Nordic Symposium on Frozen Ground Morphology

Johnsson, G.: Localities visited on Excursions during the Nordic Symposium on Frozen Ground Morphology. Geografisk Tidskrift 82: 99–103. Copenhagen, October 15, 1982. The localities showing periglacial phenomena of various kinds that were demonstreated on September 7, 8 and 10 during the frozen ground symposia are described in this report with text and illustrations. The objects demonstrated were, i.a., periglacial valleys formed chiefly through gelifluction, an ice-wedge cast with infilling of lime, large ice-wedge casts of the most common type in south Sweden, lateglacial aeolian sand underlain by wind eroded stones and boulders, fossil periglacial ground surfaces with overlying sand with small ice-wedge casts and asymmetrical periglacial valleys.

The Hudson Shelf Valley: Its role in shelf sediment transport

The Hudson Shelf Valley was deeply incised by Pleistocene lowstands of the sea. During the Holocene transgression, fluvial, estuarine, and estuary-mouth depositional environments were displaced landward, and sedimentation in these environments partially filled the valley. Holocene sediment thickness in the seaward half of the valley is about the same as on the shelf to either side, but in the landward half of the valley, 22 m of sediment is present versus 5–10 m on the adjacent shelf. Sediment volume calculations in the upper shelf valley show that there is about three times the infill volume east of the thalweg as compared to the infill to the west. This configuration indicates that the valley has served as a sediment trap and records the westward migration of the thalweg during the Holocene. Most of the infill was the result of littoral drift which transported sand westward along the south shore of Long Island during the Holocene transgression. Modern sediment transport, as calculated from currentmeter observations and inferred from bedform observations, is mainly south westward, along the regional trend of the isobaths and across the shelf valley. Therefore, infill on the eastern side of the shelf valley is continuing at present. Observations of the regional distribution of sediment types indicate that the asymmetrical valley fill is part of a pattern of bottom response to flow. The former drainage divides on both sides of the shelf valley are surfaced by coarse lag deposits on slopes facing northeast, into the direction from which the major storm flows come, while the down-current sides are mantled with fine sand.

Micrometeorological study of an urban valley

Winds, temperatures, and carbon monoxide concentrations were measured in a cross-section of the North Saskatchewan River Valley in central Edmonton on a clear October evening with cross-valley winds. The evolution of a complex asymmetrical valley inversion with vertical temperature gradients up to 12C (100 m)−1 on the north-facing slope and 6C (100 m)−1 on the south-facing slope is described. The inversion is accompanied by downslope winds of about 0.4 m s−1 and a reversal from upvalley to downvalley winds. Carbon monoxide concentrations on the south-facing slope exhibit a well-defined evening maximum and an immediate response to the reversal from upslope to downslope winds.

Marine terrace deformation, san diego county, California

Abstract The NW—SE trending southern California coastline between the Palos Verdes Peninsula and San Diego roughly parallels the southern part and off-shore extension of the dominantly right-lateral, strike-slip, Newport—Inglewood fault zone. Emergent marine terraces between Newport Bay and San Diego record general uplift and gentle warping on the northeast side of the fault zone throughout Pleistocene time. Marine terraces on Soledad Mt. and Point Loma record local differential uplift (maximum 0.17 m/ka) during middle to late Pleistocene time on the southwest side of the fault (Rose Canyon fault) near San Diego. The broad Linda Vista Mesa (elev. 70–120 m) in the central part of coastal San Diego County, previously thought to be a single, relatively undeformed marine terrace of Plio—Pleistocene age, is a series of marine terraces and associated beach ridges most likely formed during sea-level highstands throughout Pleistocene time. The elevations of the terraces in this sequence gradually increase northwestward to the vicinity of San Onofre, indicating minor differential uplift along the central and northern San Diego coast during Pleistocene time. The highest, oldest terraces in the sequence are obliterated by erosional dissection to the northwest where uplift is greatest. Broad, closely spaced (vertically) terraces with extensive beach ridges were the dominant Pleistocene coastal landforms in central San Diego County where the coastal slope is less than 1% and uplift is lowest. The beach ridges die out to the northwest as the broad low terraces grade laterally into narrower, higher, and more widely spaced (vertically) terraces on the high bluffs above San Onofre where the coastal slope is 20–30% and uplift is greatest. At San Onofre the terraces slope progressively more steeply toward the ocean with increasing elevation, indicating continuous southwest tilt accompanying uplift from middle to late Pleistocene time. This southwest tilt is also recorded in the asymmetrical valleys of major local streams where strath terraces occur only on the northeast side of NW—SE-trending valley segments. The deformational pattern (progressively greater uplift to the northwest with slight southwest tilt) recorded in the marine and strath terraces of central and northern coastal San Diego County conforms well with the historic pattern derived by others from geodetic data. It is not known how much of the Santa Ana structural block (between the Newport—Inglewood and the Elsinore fault zones) is affected by this deformational pattern.

Maximum likelihood estimation of multivariate non-linear functional relationships

The results of Dolby (1972) and Dolby and Feeeman (1975) on the estimation of an explicit non-linear functional relationship are examined for the multivariate case with Σknown up to a multiplicative constant. It is shown that in both univariate and multivariate situations the method of scoring for parameters is susceptible to major errors whenever the non-linearity implies asymmetric peaks or valleys and the data is relatively ”noisy”. Amendments to this method are proposed and demonstrated.

THE TECTONIC DISPLACEMENT OF TERRACES IN THE SOUTHERN PART OF THE TONAMI PLAIN, TOYAMA PREFECTURE

The Takashozu fault system, running NE-SW direction, is located at the northwestern foot of the Takashozu Mountains, Toyama Prefecture, and separates the Tonami Plain from the high mountains. Along the fault line, several kinds of fault topographies have developed, such as terminal facets, kern cols, kern buts and valleys flowing parallel to the strike of the fault. At Inami and Akasobu, the Miocene andesitic rock has thrusted up from south to north onto the terrace gravels of the middle and upper Pleistocene ages. The Takashozu fault has dislocated vertically the several levels of terrace surfaces here and there along the fault line. The higher the terraces are, the larger the amount of displacement is. In the drainage basin of the Sho River, it is inferred that not only Pleistocene terraces but also Holocene terrace gravel beds have been cut by the fault activities. In the southwestern part of the Tonami Plain, the gradient of the terrace surface is steeper in the older terraces. The valley dissecting the higher terrace surfaces shows an asymmetric form, i.e., the valley walls of the northern side are generally steeper than those of the southern side. It would be considered that the principal factor forming this asymmetric valley topography is the continuous upheaval of the mountains located to the south of the plain.

A note on asymmetric valleys in the central Mackenzie River catchment, Canada

A note on asymmetric valleys in the central Mackenzie River catchment, Canada

Soil Temperatures in the Active Layer, Beaufort Plain

Reports on summer 1968 fieldwork in this region of northwest Banks Island, where the some 200-ft thick, probably late Tertiary Beaufort Formation outcrops as unconsolidated sands and gravel with shale units. This plain is gently undulating and fluvially dissected, with many asymmetric valleys having steeper slopes oriented to the southwest. The scant summer precipitation, temperature (T) and wind data are tabulated and discussed in connection with soil T measured on slopes of varying orientations. Absolute T values in the Beaufort materials are high relative to analogous arctic regions. The asymmetry of the valleys appears to be closely related to the distinctive microclimates on differently oriented slopes, as controlled by angle and azimuth of the sun and prevailing northwest winds.

Nuclear octupole deformation and the mechanism of fission

Tbe stability of nuclei against an octupole deformation was calculated. It was found that the interaction of levels of opposite parity makes the nuclei in certain regions very soft to octupole deformation. The negative parity collective states in heavy nuclei and in the rare-earth region can be interpreted as octupole vibrations. The predicted A-dependence of the energy of these states agrees well with experimental data. For very elongated shapes, which are of interest in fission, it was found that stable octupole deformation occurs. The potential surface of the fission barrier would therefore possess two asymmetric valleys. There is a linear ralationship between the mass ratio of the fission fragments and the degree of octupole deformation at the saddle point. The occurrence of symmetric fission in the lighter elements is explained. The influence of the octupole deformation on the fission barrier also provides a basis for understanding the variation in fission threshold. The experimental data agree with the calculated values. The peak to valley ratio in the mass distribu tion was calculated, with the assumption of statistical equilibrium at the saddle point. Good agreement was found for excitation energies below 10 Mev. For higher energies a symmetric component appeared which rosemore » with increasing energy. (auth)« less

Some aspects of the drift deposits and geomorphology of south-east Hertfordshire

During the field work of a soil survey of 3rd Edition Sheet 239 (Hertford) it became evident that the origins and distribution of the drifts of south-east Hertford-shire offered a number of problems that have been incompletely solved. In this account further data on the lithology and mineralogical composition of the deposits are presented and their chronology and derivation are discussed. Attention is drawn to the distribution of asymmetric valleys in this and neighbouring areas, and their origin is discussed.

INTRAVALLEY VARIATION IN SLOPE ANGLES RELATED TO MICROCLIMATE AND EROSIONAL ENVIRONMENT

East- or west-trending stream valleys that have erosional slopes have been reported to be (1) asymmetrical with the north-facing slopes steeper, (2) asymmetrical with the south-facing slopes steeper, and (3) symmetrical, with both sides of equal mean slope angle. A series of measurements of angles of erosional slopes, taken in three east-trending, low-gradient valleys in the Laramie Range, Wyoming, shows that north-facing slopes there tend to be 4.4° steeper than opposed south-facing slopes; slope angle is further affected by nearness to the channel. In valleys that have channel gradients greater than 6° and greatly differing vegetation density across the valley, measurements of slope angles definitely show valley symmetry. The interpretation given is that unless the channel has been maintained against the base of the north-facing slope by greater slope wash from the south-facing slope, vegetation differences and resulting rates of slope erosion alone do not produce asymmetric valleys. Valley asymmetry that results from a variety of basic causes can be attributed to a single mechanism, asymmetric lateral corrosion by the stream. Difference in frost action on north-and south-facing valley sides is rejected as a cause of valley asymmetry in the areas studied because (1) the asymmetry is opposite that reported in tundra regions elsewhere, and (2) the degree of asymmetry in two widely separated areas does not reflect differences in the degree of frost activity in the two areas.

Asymmetrical Valleys of the Chiltern Hills

Asymmetrical Valleys of the Chiltern Hills

Les formations du Quaternaire ancien de la Boutonne superieure (Deux-Sevres)

Abstract Bedded Quaternary slope deposits in the upper Boutonne region, Deux-Sevres, France, show evidence of two successive stages of frost action. Depending on the orientation of the beds, solifluction has produced either asymmetric valleys (west bank gentle, east bank steep) or valleys "en berceau" (very gently sloping sides and flat bottoms). The Boutonne valley itself is filled with periglacial deposits as yet hardly affected by recent, preponderantly chemical, erosion.

Asymmetric Valleys and Climatic Boundaries

Asymmetric Valleys and Climatic Boundaries