scholarly journals Sculpted Bedrock Forms along the Niagara Escarpment, Niagara Peninsula, Ontario

2007 ◽  
Vol 46 (2) ◽  
pp. 195-207 ◽  
Author(s):  
Keith J. Tinkler ◽  
Ronald E. Stenson
Keyword(s):  
Flow Velocity ◽  
Continuous Spectrum ◽  
Niagara Escarpment ◽  
Site Mapping ◽  
A Site ◽  
Subglacial Meltwater ◽  
Small Obstacle

ABSTRACT Assemblages of subglacial sculpted bedrock forms (p-forms; Dahl, 1965) are identified on resistant units of the Niagara Escarpment in the Niagara Peninsula, and on the Onondaga Escarpment. The scale of the features is much larger than previously recorded for bedrock glacial features in the Peninsula (Feenstra, 1981) and we suggest that there is a continuous spectrum of forms from small obstacle marks with dimensions of a few centimetres, through ridges and furrows measured in tens of metres, to promontories on the order of kilometres. Such assemblages comprise fluted surfaces with a consistent orientation between N40E and N45E, and which show very little variation within a site. Mapping the features has increased our awareness of their extent, and of the problems they pose for mechanisms proposed to explain them. The morphometry of the forms is similar to that described elsewhere, and the irregular edge of the Niagara Escarpment to oncoming flows is thought to be responsible for the prominent features described. The apparent removal of substantial bedrock blocks implies flow velocity well in excess of 3 m/s. Therefore the sculpting of the forms is attributed to fast flowing subglacial meltwater which may have had a discharge of the magnitude of 2.1 x 106 cumecs.

scholarly journals Standortkartierung im Lehr- und Forschungswald der ETH in Sedrun | Site mapping in the ETH Research Forest of Sedrun

2009 ◽  
Vol 160 (2) ◽  
pp. 27-36
Author(s):  
Jacques Doutaz ◽  
Hans-Ulrich Frey ◽  
Harald Bugmann
Keyword(s):  
Classification System ◽  
Sustainable Forest Management ◽  
Structural Characteristics ◽  
Site Classification ◽  
Classification Methods ◽  
Site Type ◽  
Forest Sites ◽  
Site Mapping ◽  
A Site ◽  
Site Types

Phytosociology has advanced in various respects since the fundamental groundwork was laid, which was mainly concerned with developing a classification system of vegetation units. Current site classification methods for forests consider not only floristic aspects, but also pedological, topographic and structural characteristics of forest stands. During the summer of 2007, a site mapping was carried out in the ETH Research Forest near Sedrun (Switzerland). This paper describes the methods employed, and it evaluates the applicability thereof based on case studies. Site mapping is based on expert opinion, and as such it includes a certain degree of generalization and subjectivity in the evaluation of stands and their assignment to a site type. However, we propose that site classification constitutes a suitable tool for describing and characterizing the complexity of forest sites. The accurate description of site types strongly facilitates the interpretation and the applicability of a classification system in decision support for sustainable forest management.

Evidence for catastrophic subglacial meltwater sheetflood events on the Bruce Peninsula, Ontario

1998 ◽  
Vol 35 (10) ◽  
pp. 1180-1202 ◽  
Author(s):  
PSG Kor ◽  
D W Cowell
Keyword(s):  
Regional Scale ◽  
Laurentide Ice Sheet ◽  
Michigan Basin ◽  
Niagara Escarpment ◽  
Outburst Floods ◽  
Unconsolidated Sediment ◽  
Self Similar ◽  
Bedrock Surface ◽  
Subglacial Meltwater ◽  
French River

The Bruce Peninsula, a carbonate bedrock escarpment, lies "downflow" from a sculpted bedrock terrain at the French River. The sculpted forms are attributed to a hypothesis of erosion by regional-scale, subglacial meltwater flooding. This paper presents new data from the Bruce Peninsula that tests the meltwater outburst hypothesis in a downflow direction of the predicted flood path. The bedrock surface of the Bruce Peninsula shows extensive development of sculpted features that bear a striking resemblance to s-forms at the mouth of the French River. They are self-similar and hierarchical in scale, ranging in dimensions from a few centimetres to several kilometres. Remarkable concentrations of potholes are located near the brow of the escarpment. The Bruce Peninsula lacks a pervasive cover of unconsolidated sediment. What little sediment exists has been modified into long, narrow drumlins. The Niagara Escarpment on the peninsula has been back wasted into the edge of the Paleozoic Michigan Basin. Along its east-facing slope, the escarpment is marked by more overdeepened reentrant valleys and intervening promontories than is normal for the rest of the escarpment. Clusters of rounded, percussion-marked boulders of exotic origin are concentrated at the heads of the reentrant valleys. Taken together, these features are inferred to support the hypothesis that subglacial outburst floods beneath the Laurentide ice sheet crossed Georgian Bay and strongly sculpted the Bruce Peninsula. The consistent orientation of the reentrant valleys, aligned with the French River sculpting across the basin to the northeast, and the backwasting of its caprock attest to the power and directional stability of the sheetfloods.

Impact of groundwater on mining and underground space development in the Niagara Escarpment area

1984 ◽  
Vol 21 (1) ◽  
pp. 60-74 ◽  
Author(s):  
R. L. Nadon ◽  
J. E. Gale
Keyword(s):  
Flow System ◽  
Sedimentary Rocks ◽  
Unconfined Aquifer ◽  
Underground Space ◽  
Mining Operations ◽  
Paleozoic Rock ◽  
Niagara Escarpment ◽  
Cap Rock ◽  
A Site ◽  
The Impact

A field, laboratory, and numerical modelling study was undertaken to determine the impact of groundwater on mining activities and underground space development in the Paleozoic rock units of the Niagara Escarpment near Milton, Ontario. Five holes were drilled at a site next to the Dufferin quarry, penetrating the Amabel dolostone, the Reynales dolostone, the Cabot Head shale, the Manitoulin limestone, the Whirlpool sandstone, and the top part of the Queenston shale. Results of hydrogeological field and laboratory tests indicate the presence of an unconfined aquifer with an average hydraulic conductivity of 2 × 10−5 m/s, and a confined sandstone aquifer with a conductivity of 5 × 10−7 m/s separated by a shale and limestone aquitard having a conductivity of less than 10−9 m/s.Numerical model simulations of the groundwater flow system indicate that, for a 2 km2 underground mine located in the dolostone cap rock, the inflow rates range from 8 L/s to over 30 L/s with significant dewatering of the unconfined aquifer occurring within a distance of 1500 m of the mine boundaries. Calculations for a hypothetical mine located in the Whirlpool and Manitoulin Formations gave inflow rates of less than 3 L/s. It is concluded that groundwater conditions will not interfere with mining operations in either the dolostone unit or in the limestone–sandstone unit but could adversely affect subsequent space development in the dolostone unit. Keywords: hydrogeology, groundwater, underground space, aggregate, mining, sedimentary rocks, Niagara Escarpment.

Buried bedrock valleys and glacial and subglacial meltwater erosion in southern Ontario, Canada

2011 ◽  
Vol 48 (5) ◽  
pp. 801-818 ◽  
Author(s):  
Cunhai Gao
Keyword(s):  
Drainage System ◽  
Geological Mapping ◽  
Glacial Erosion ◽  
Diagnostic Features ◽  
Simple Modification ◽  
Southern Ontario ◽  
Georgian Bay ◽  
Niagara Escarpment ◽  
Mechanical Weathering ◽  
Subglacial Meltwater

Morphometric features from a recently compiled bedrock topography map by the Ontario Geological Survey suggest a glacial erosion origin for the buried large bedrock valleys and troughs in southern Ontario. The bedrock valleys at Milverton, Wingham and Mount Forest are tunnel valleys, resulting from subglacial meltwater erosion beneath the Huron ice lobe, probably during or shortly after the Late-Wisconsinan glacial maximum. Diagnostic features for this interpretation include abrupt valley beginning and termination, uneven longitudinal valley profiles and up-slope gradients. The Dundas bedrock valley is the western extension of the Lake Ontario Basin. No comparable bedrock valleys were found to connect it to the Milverton valley for a joint drainage system as previously suggested. The Laurentian bedrock trough is the southeastward extension of the Georgian Bay Basin, both developed along shale bedrock between the Precambrian shield highlands and the Niagara Escarpment, resulting from long-term mechanical weathering associated with Pleistocene glacial erosion. This bedrock low has a floor that exceeds 50 km in width and is 26 m and more below the current water level of Georgian Bay. It could drain Georgian Bay should the drift cover be removed. There is no evidence to suggest that a preglacial river channel, if it existed, is still preserved in the floor of the Laurentian trough as previously suggested. The framework for an intensely glacially sculpted bedrock surface differs from the previous view for simple modification of a preglacial landscape and is, therefore, important in regional subsurface geological mapping and groundwater studies.

C. The Continuous Spectrum of Pulsating Variable Stars

1967 ◽  
Vol 28 ◽  
pp. 177-206
Author(s):  
J. B. Oke ◽  
C. A. Whitney
Keyword(s):  
Continuous Spectrum ◽  
Variable Stars ◽  
Velocity Fields ◽  
The Other ◽  
Line Spectrum ◽  
Direct Information ◽  
Thermodynamic Structure ◽  
Diagnostic Interpretation ◽  
Pulsating Variable Stars ◽  
The Continuum

Pecker:The topic to be considered today is the continuous spectrum of certain stars, whose variability we attribute to a pulsation of some part of their structure. Obviously, this continuous spectrum provides a test of the pulsation theory to the extent that the continuum is completely and accurately observed and that we can analyse it to infer the structure of the star producing it. The continuum is one of the two possible spectral observations; the other is the line spectrum. It is obvious that from studies of the continuum alone, we obtain no direct information on the velocity fields in the star. We obtain information only on the thermodynamic structure of the photospheric layers of these stars–the photospheric layers being defined as those from which the observed continuum directly arises. So the problems arising in a study of the continuum are of two general kinds: completeness of observation, and adequacy of diagnostic interpretation. I will make a few comments on these, then turn the meeting over to Oke and Whitney.

Eels Under Standing Wave Conditions

1982 ◽  
Vol 40 ◽  
pp. 492-495
Author(s):  
O.L. Krivanek ◽  
J. TaftØ
Keyword(s):  
Standing Wave ◽  
Wave Conditions ◽  
Set Up ◽  
A Site ◽  
Complex Crystal

It is well known that a standing electron wavefield can be set up in a crystal such that its intensity peaks at the atomic sites or between the sites or in the case of more complex crystal, at one or another type of a site. The effect is usually referred to as channelling but this term is not entirely appropriate; by analogy with the more established particle channelling, electrons would have to be described as channelling either through the channels or through the channel walls, depending on the diffraction conditions.

Head Size and DNA Content in Bacteriophage T4

1972 ◽  
Vol 30 ◽  
pp. 200-201
Author(s):  
Fred Eiserling ◽  
A. H. Doermann ◽  
Linde Boehner
Keyword(s):  
Electron Microscopy ◽  
Dna Content ◽  
Bacteriophage T4 ◽  
Head Size ◽  
Virus Particles ◽  
Altered Protein ◽  
A Cell ◽  
Bacterial Viruses ◽  
A Site ◽  
Protein Shell

The control of form or shape inheritance can be approached by studying the morphogenesis of bacterial viruses. Shape variants of bacteriophage T4 with altered protein shell (capsid) size and nucleic acid (DNA) content have been found by electron microscopy, and a mutant (E920g in gene 66) controlling head size has been described. This mutant produces short-headed particles which contain 2/3 the normal DNA content and which are non-viable when only one particle infects a cell (Fig. 1).We report here the isolation of a new mutant (191c) which also appears to be in gene 66 but at a site distinct from E920g. The most striking phenotype of the mutant is the production of about 10% of the phage yield as “giant” virus particles, from 3 to 8 times longer than normal phage (Fig. 2).

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