Out-of-phase Holocene terraces in part of the North Saskatchewan River basin, Alberta

1988 ◽  
Vol 25 (3) ◽  
pp. 454-464 ◽  
Author(s):  
Bruce Rains ◽  
James Welch
Keyword(s):  
River Valley ◽  
Alluvial Terrace ◽  
Base Level ◽  
The North ◽  
Alluvial Sediment ◽  
Main River ◽  
Alluvial Terraces ◽  
Local Base ◽  
Geochronological Evidence ◽  
Small Tributary

This study focuses on alluvial terraces in part of the North Saskatchewan River valley, near Edmonton, and in the small tributary valleys of Whitemud and Strawberry creeks. The characteristic terrace morphologies and alluvial sediment sequences are briefly described, but most importantly, the deposits are radiocarbon dated for many sites. Twenty-seven new 14C dates on bone, wood, charcoal, and shell materials, along with previously reported dates, provide the chronological framework for the study. Occurrences of the Mazama ash marker bed in terrace alluvium offer additional geochronological evidence. The small tributary valleys have clearly developed in an out-of-phase manner relative to the main river valley, which acts as their local base level. Despite the comparatively abundant geochronological evidence described here, the explanation of alluvial terrace development, in terms of predominant causal factors, remains tantalizingly elusive.

Eocene paleo-physiography and drainage directions, southern Interior Plateau, British Columbia

2005 ◽  
Vol 42 (2) ◽  
pp. 215-230 ◽  
Author(s):  
Selina Tribe
Keyword(s):  
British Columbia ◽  
Middle Eocene ◽  
Regional Scale ◽  
River Valley ◽  
Coast Mountains ◽  
Base Level ◽  
The North ◽  
Bedrock Geology ◽  
River Valleys ◽  
Early Cenozoic

A map of reconstructed Eocene physiography and drainage directions is presented for the southern Interior Plateau region, British Columbia south of 53°N. Eocene landforms are inferred from the distribution and depositional paleoenvironment of Eocene rocks and from crosscutting relationships between regional-scale geomorphology and bedrock geology of known age. Eocene drainage directions are inferred from physiography, relief, and base level elevations of the sub-Eocene unconformity and the documented distribution, provenance, and paleocurrents of early Cenozoic fluvial sediments. The Eocene landscape of the southern Interior Plateau resembled its modern counterpart, with highlands, plains, and deeply incised drainages, except regional drainage was to the north. An anabranching valley system trending west and northwest from Quesnel and Shuswap Highlands, across the Cariboo Plateau to the Fraser River valley, contained north-flowing streams from Eocene to early Quaternary time. Other valleys dating back at least to Middle Eocene time include the North Thompson valley south of Clearwater, Thompson valley from Kamloops to Spences Bridge, the valley containing Nicola Lake, Bridge River valley, and Okanagan Lake valley. During the early Cenozoic, highlands existed where the Coast Mountains are today. Southward drainage along the modern Fraser, Chilcotin, and Thompson River valleys was established after the Late Miocene.

scholarly journals Bedrock gorge incision via anthropogenic meander cutoff

Geology ◽  
2021 ◽  
Author(s):  
Adrian M. Bender
Keyword(s):  
Gradual Transition ◽  
Historical Records ◽  
Erosion Rates ◽  
Base Level ◽  
The North ◽  
Shaping Process ◽  
North Fork ◽  
Formation Experiment ◽  
Level Lowering ◽  
Local Base

Bedrock river-gorge incision represents a fundamental landscape-shaping process, but a dearth of observational data at >10 yr timescales impedes understanding of gorge formation. I quantify 102 yr rates and processes of gorge incision using historical records, field observations, and topographic and image analysis of a human-caused bedrock meander cutoff along the North Fork Fortymile River in Alaska (USA). Miners cut off the meander in 1900 CE, abruptly lowering local base level by 6 m and forcing narrowing and steepening of the channel across a knickpoint that rapidly incised upstream. Tectonic quiescence, consistent rock erosivity, and low millennial erosion rates provide ideal boundary conditions for this 102 yr gorge-formation experiment. Initial fast knickpoint propagation (23 m/yr; 1900–1903 CE) slowed (4 m/yr; 1903–1981 CE) to diffusion (1981–2019 CE) as knickpoint slope decreased, yielding an ~350-m-long, 6-m-deep gorge within the pre–1900 CE channel. Today, diffusion dominates incision of a 500-m-long knickzone upstream of the gorge, where sediment transport likely limits ongoing adjustments to the anthropogenic cutoff. Results elucidate channel width, slope, discharge, and sediment dynamics consistent with a gradual transition from detachment- to transport-limited incision in fluvial adjustment to local base-level lowering.

Forces driving late Pleistocene (ca. 77–12 ka) landscape evolution in the Cimarron River valley, southwestern Kansas

2015 ◽  
Vol 84 (1) ◽  
pp. 106-117 ◽  
Author(s):  
Anthony L. Layzell ◽  
Rolfe D. Mandel ◽  
Greg A. Ludvigson ◽  
Tammy M. Rittenour ◽  
Jon J. Smith
Keyword(s):  
Late Pleistocene ◽  
Landscape Evolution ◽  
Soil Formation ◽  
River Valley ◽  
High Plains ◽  
Level Control ◽  
Base Level ◽  
Dry Conditions ◽  
Cimarron River ◽  
Local Base

This study presents stratigraphic, geomorphic, and paleoenvironmental (δ13C) data that provide insight into the late Pleistocene landscape evolution of the Cimarron River valley in the High Plains of southwestern Kansas. Two distinct valley fills (T-1 and T-2) were investigated. Three soils occur in the T-2 fill and five in the T-1 fill, all indicating periods of landscape stability or slow sedimentation. Of particular interest are two cumulic soils dating to ca. 48–28 and 13–12.5 ka. δ13C values are consistent with regional paleoenvironmental proxy data that indicate the prevalence of warm, dry conditions at these times. The Cimarron River is interpreted to have responded to these climatic changes and to local base level control. Specifically, aggradation occurred during cool, wet periods and slow sedimentation with cumulic soil formation occurred under warmer, drier climates. Significant valley incision (~ 25 m) by ca. 28 ka likely resulted from a lowering of local base level caused by deep-seated dissolution of Permian evaporite deposits.

Alluvial Terracing in a Falling-stage Braidplain: the Lower Cretaceous Cadomin Formation, West-central Alberta, Canada

2019 ◽  
Vol 89 (8) ◽  
pp. 701-727 ◽  
Author(s):  
Michael F. Johnson ◽  
Robert W. Dalrymple
Keyword(s):  
Lower Cretaceous ◽  
Sediment Supply ◽  
Alluvial Deposits ◽  
Western Canada Sedimentary Basin ◽  
Exceptional Preservation ◽  
Base Level ◽  
The North ◽  
West Central ◽  
Alluvial Terraces ◽  
Canada Sedimentary Basin

Abstract The Lower Cretaceous Cadomin Formation in the Western Canada Sedimentary Basin is a thin, regionally extensive, conglomeratic fluvial deposit that accumulated over many million years on the sub-Cretaceous unconformity. Based on a dataset of approximately 50 cores and 750 wireline well logs from west-central Alberta, detailed isopach mapping of the overlying deposits reveals the presence of a complex, terraced paleo-topography on the top of the Cadomin Formation, consisting of six terrace levels in the study area. These terraces flank a series of north–south valleys that feed into a larger east–west valley to the north of the study area. This larger valley is also bordered by terraces that step downward to the north. The gradients of the north–south valley thalwegs are steeper than the flanking terraces, indicating that each terrace is diachronous and was most likely formed by the headward migration of knickpoints generated by episodic incision of the trunk valley. This paleo-topography formed during a prolonged period of falling base level caused by unroofing of the adjacent orogen. Thus, the Cadomin Formation represents a falling-stage systems tract. The deposits underlying each terrace consist mainly of channel-thalweg and braid-bar deposits. Preservation of full channel-bar successions in many terraces is consistent with terrace abandonment as incision resumed following a period of mild aggradation. Terrace abandonment is also indicated by the presence of a capping layer of wind-blown silt. Pedogenic alteration of this loessite is greatest on the highest terraces and extends to considerable depths, indicating the existence of a significant hiatus at the top of the Cadomin Formation. This surface, which lies above falling-stage deposits, should be used as the sequence boundary, if the sequence boundary is thought to coincide with the time of lowest base level. This surface, although its formation was diachronous, represents a real landscape surface, unlike the composite erosion surface beneath the Cadomin Formation (i.e., the sub-Cretaceous unconformity). The alternation of incision and aggradation that generated the terraces was probably the result of allogenic fluctuations in sediment supply caused by climate cycles, as was the case for analogous Quaternary terrace staircases. Downstepping alluvial terraces are a viable mechanism for the progradation of alluvial gravels long distances from a mountain belt during periods of basin uplift, and may explain the relatively thin, but areally extensive, alluvial sandstone and conglomerate sheets that are common at major unconformities in the stratigraphic record. We suggest that signs of subtle terracing may have been overlooked in similar sheet-like alluvial deposits elsewhere, although they can be removed by erosion during shoreline transgression or by later fluvial-channel migration. In the case of the Cadomin Formation, the exceptional preservation of the terraces is likely due to a combination of the difficulty of eroding the conglomerate and indurated loessite cap, and of the low-energy nature of floodplain sedimentation in the overlying Gething Formation.

River erosion and bank stabilization — North Saskatchewan River, Edmonton, Alberta

1979 ◽  
Vol 16 (3) ◽  
pp. 567-576 ◽  
Author(s):  
S. Thomson ◽  
D. L. Townsend
Keyword(s):  
River Valley ◽  
Past Century ◽  
Lateral Migration ◽  
Base Level ◽  
The North ◽  
River Terraces ◽  
Land Survey ◽  
Bank Stabilization ◽  
River Migration ◽  
Erosion Protection

The postglacial geology of the North Saskatchewan River valley in Edmonton is reviewed. Using radiocarbon dating by others, limited land survey, and aerial photography measurement, it is inferred that the river valley was quickly formed after glaciation during a period of rapid downcutting. Over the last 8000 years, the rate of vertical downcutting has been about 25 times slower than it was during the initial 5000 years following deglaciation. As the river reached its base level, lateral river migration occurred and erosion against the low-lying river terraces has been substantial. It is inferred that over the past century the lateral migration is probably at the rate of at least 30 m/century.Low-level erosion protection berms are required to stabilize the toe of a variety of landslides; however, they do not completely eliminate the causes of upper slope movement. The engineering considerations underlying the construction of four protective works are discussed and overall costs are presented.

Sources of Chlorophenolic Compounds to the Fraser River Estuary

1988 ◽  
Vol 23 (1) ◽  
pp. 55-68 ◽  
Author(s):  
J. H. Carey ◽  
J. H. Hart
Keyword(s):  
River Flow ◽  
River Estuary ◽  
Low Flow ◽  
Fraser River ◽  
Pulp Mills ◽  
Flow Conditions ◽  
Downstream Site ◽  
Upstream Site ◽  
The North ◽  
Main River

Abstract The identity and concentrations of chlorophenolic compounds in the Fraser River estuary were determined under conditions of high and low river flow at three sites: a site upstream from the trifurcation and at downstream sites for each main river arm. Major chlorophenolics present under both flow regimes were 2,4,6-trichlorophenol (2,4,6-TCP), 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP), pentachlorophenol (PCP), tetrachloroguaiacol (TeCG) and a compound tentatively identified as 3,4,5-trichloroguaiacol (3,4,5-TCG). Under high flow conditions, concentrations of the guaiacols were higher than any of the Chlorophenols and concentrations of all five chlorophenolics appeared to correlate. Under low flow conditions, concentrations of chloroguaiacols were higher than Chlorophenols at the upstream site and at the downstream site on the Main Arm, whereas at the downstream site on the North Arm, concentrations of 2,3,4,6-TeCP and PCP were higher than the chloroguaiacols in some samples. Overall, the results indicate that pulp mills upstream from the estuary are important sources of chlorophenolics to the estuary under all flow conditions. Additional episodic inputs of 2,3,4,6-TeCP and PCP from lumber mills occur along the North Arm. When these inputs occur, they can cause the concentrations of Chlorophenols in the North Arm to exceed provisional objectives. If chloroguaiacols are included as part of the objective, concentrations of total chlorophenolics in water entering the estuary can approach and exceed these objectives, especially under low flow conditions.

scholarly journals Temporal and spatial variation of NPP and its response to climatic factors in main river valleys on the southern slope of Qilian Mountains

2019 ◽  
Vol 131 ◽  
pp. 01044
Author(s):  
Rong-rong Yang ◽  
Guang-chao Cao ◽  
Sheng-kui Cao ◽  
Yao Lan ◽  
Zhuo Zhang ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Climatic Factors ◽  
Growing Season ◽  
Qilian Mountains ◽  
River Valley ◽  
Distribution Characteristics ◽  
Southern Slope ◽  
Qilian Mountain ◽  
Main River ◽  
River Valleys

Based on the NPP products of MODIS data, the spatial and temporal distribution characteristics of grassland NPP and its response to climatic factors in the vegetation growing season of the main river valleys in the southern slope of Qilian Mountains from 2000 to 2016 were carried out by correlation analysis and spatial interpolation. The research further provides a scientific basis for the quality evaluation of grassland ecosystems on the southern slope of Qilian Mountain and the rational use of grassland resources along the river. The results show that: (1) With the increasing distance of buffers on both sides of the river, the NPP of grassland in each year shows the characteristics of “single-peak” distribution, which is increased first and then decreased; (2) the NPP of grassland in the main river valley of the southern slope of Qilian Mountain The spatial distribution characteristics show a trend of increasing from northwest to southeast. (3) The spatial distribution of NPP and air temperature in the main river valleys of the southern slope of Qilian Mountains is gradually increasing from northwest to southeast, but the spatial distribution correlation coefficient of NPP and precipitation in the river valley grassland of vegetation growing season basically shows a trendof decreasing from northwest to southeast.

The late Wisconsinan olistostrome of the lower Coppermine River valley, Northwest Territories

1986 ◽  
Vol 23 (11) ◽  
pp. 1700-1708 ◽  
Author(s):  
Denis A. St-Onge ◽  
Jean Lajoie
Keyword(s):  
Debris Flows ◽  
Late Quaternary ◽  
Fine Sand ◽  
Coarse Sand ◽  
Coarse Fraction ◽  
River Valley ◽  
Glacial Lake ◽  
The North ◽  
Geologic Record ◽  
Coppermine River

The late Quaternary olistostrome exposed in the lower Coppermine River valley fills a paleovalley that ranges in apparent width from 150 to 400 m and was cut into Precambrian bedrock before the last glaciation. The olistostrome is here named the Sleigh Creek Formation. The coarse fraction of the formation is matrix supported; beds are massive or reversely graded and have sharp, nonerosive contacts. These characteristics suggest deposition of the coarse fraction by debris flows. The olistostrome sequence is bracketed by, and wedged into, a marine rhythmite sequence, which indicates that deposition occurred in a marine environment.About 10 500 years BP glacier ice in the Coronation Gulf lowland dammed the valley to the south, which was occupied by glacial Lake Coppermine. Sediments accumulated in this lake in a 30 m thick, coarsening upward sequence ranging from glaciolacustrine rhythmites of silt and fine sand at the base to coarse sand alluvium, and deltaic gravels at the top. As the Coronation Gulf lowlands became ice free, the Coppermine River reoccupied its former drainage course to the north. The steep south to north gradient and rapid downcutting by the river through the glacial lake sediments produced unstable slope conditions. The resulting debris flows filled a bedrock valley network below the postglacial sea level, forming the diamicton sequence.The interpretation of the Sleigh Creek Formation raises questions concerning silimar diamicton deposits usually defined as "flowtills." More generally, the results of this study indicate that care must be used when attempting paleogeographic reconstructions of "glaciogenic" deposits in marine sequences in any part of the geologic record.

scholarly journals Pałac czy dwór? Na Czechowie czy na Czechówce? Glossa do rozważań o krajobrazie kulturowym północno-zachodniej części historycznego Lublina

2019 ◽  
Vol 67 (4) ◽  
pp. 165
Author(s):  
Jacek Chachaj
Keyword(s):  
18Th Century ◽  
River Valley ◽  
Previous Article ◽  
Precise Location ◽  
Architectural Analysis ◽  
The North ◽  
Modern Era ◽  
North Western

The article is a response to the publication of M. Dudkiewicz, W. Durlak and M. Dąbski concerning a non-existent object called a manor or palace that existed in the modern era in the north-western part of Lublin on the edge of a plateau extending northwards from the Czechówka river valley. Since the previous article contains substantive factual errors, this text also attempts to show the ownership changes of the area where the manor existed, and specify its more precise location. The postulate for further research remains primarily the architectural analysis of the building, which in the second half of the 18th century was in an advanced state of decay.

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