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.

Lobal affinity of Late Wisconsin tills at St. Marys in southwestern Ontario, Canada

2014 ◽  
Vol 51 (9) ◽  
pp. 837-849 ◽  
Author(s):  
Aleksis Dreimanis ◽  
Paul F. Karrow ◽  
Peter J. Barnett
Keyword(s):  
Three Dimensional ◽  
Lake Huron ◽  
Laurentide Ice Sheet ◽  
Ice Flow ◽  
Subaerial Exposure ◽  
Regional Flow ◽  
New Information ◽  
Bedrock Surface ◽  
Flow Directions ◽  
Subglacial Meltwater

The exposures at the St. Marys Cement Inc. quarry at St. Marys, Ontario, have been studied by geologists since the mid-1950s. This paper summarizes previous and new information collected in 2009, 2010, and 2012 and discusses the record of sediments resting on the bedrock surface that have been exposed during quarry operations. The exposed sediments illustrate the dynamic behavior of the Laurentide Ice Sheet in this area during the Late Wisconsin. Evidence for subglacial meltwater activity, shifting ice-flow directions during till deposition, a local or regional erosion event, possible subaerial exposure, and ice-marginal sedimentation is observed in the sequence of tills and stratified sediments exposed in the quarries. It also highlights how rapid lateral facies changes, complex contact relationships, and steep erosional contacts can prove to be challenging for correlation and extrapolation of subsurface units into three-dimensional stratigraphic models. Fourteen units were identified of which the lower six were deposited during the Nissouri age (Catfish Creek Drift). This included five layers of till deposited by a glacier that alternated from flowing out of the Lake Huron basin to that of a regional flow to the south-southwest. An angular unconformity cuts into these sediments and separates them from a finer-grained sediment sequence (primarily of Port Bruce age) consisting of glaciofluvial gravel, two fine-textured till layers, and rhythmically bedded glaciolacustrine sediments, all overlain by the uppermost till, the Rannoch Till, and Mitchell Moraine ice-marginal fan sediments.

Glacial-Lake Outburst Erosion of the Grand Valley, Michigan, and Impacts on Glacial Lakes in the Lake Michigan Basin

1993 ◽  
Vol 39 (1) ◽  
pp. 36-44 ◽  
Author(s):  
Alan E. Kehew
Keyword(s):  
Lake Level ◽  
Lake Michigan ◽  
Laurentide Ice Sheet ◽  
Glacial Lake ◽  
Michigan Basin ◽  
Lake Agassiz ◽  
Lake Algonquin ◽  
Lake Michigan Lobe ◽  
Possible Cause ◽  
Glacial Lake Algonquin

AbstractGeomorphic and sedimentologic evidence in the Grand Valley, which drained the retreating Saginaw Lobe of the Laurentide Ice Sheet and later acted as a spillway between lakes in the Huron and Erie basins and in the Michigan basin, suggests that at least one drainage event from glacial Lake Saginaw to glacial Lake Chicago was a catastrophic outburst that deeply incised the valley. Analysis of shoreline and outlet geomorphology at the Chicago outlet supports J H Bretz's hypothesis of episodic incision and lake-level change. Shoreline features of each lake level converge to separate outlet sills that decrease in elevation from the oldest to youngest lake phases. This evidence, coupled with the presence of boulder lags and other features consistent with outburst origin, suggests that the outlets were deepened by catastrophic outbursts at least twice. The first incision event is correlated with a linked series of floods that progressed from Huron and Erie basin lakes to glacial Lake Saginaw to glacial Lake Chicago and then to the Mississippi. The second downcutting event occurred after the Two Rivers Advance of the Lake Michigan Lobe. Outbursts from the eastern outlets of glacial Lake Agassiz to glacial Lake Algonquin are a possible cause for this period of downcutting at the Chicago outlets.

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.

Late Glacial landforms of Wollaston Peninsula, Victoria Island, Northwest Territories: product of ice-marginal retreat, surge, and mass stagnation

1988 ◽  
Vol 25 (2) ◽  
pp. 262-279 ◽  
Author(s):  
David R. Sharpe
Keyword(s):  
Northwest Territories ◽  
Large Scale ◽  
Regional Scale ◽  
Late Glacial ◽  
Ground Moraine ◽  
Ice Conditions ◽  
Late Wisconsinan ◽  
Victoria Island ◽  
Glacial Landforms ◽  
Subglacial Meltwater

An analysis of glacial landforms on a regional scale leads to an interpretation of the dynamics of Late Wisconsinan glaciation on Wollaston Peninsula, Victoria Island, Northwest Territories. The glacial record is dominated by four adjacent belts of landforms: (I) ground moraine (till plains and ice-marginal drainage features), (II) hummocky moraine, (III) lateral and shear moraine, and (IV) streamlined landforms. The landform belts are considered as representing four distinct glacial ice conditions or regimes: (1) ice-margin retreat during extending flow of thin, active ice; (2) marginal ice stagnation following compressional flow; (3) a surging ice margin producing massive shear moraines; and (4) large-scale flooding and mass ice stagnation following a surge. These landform belts were arranged in zones by topographically controlled glacial dynamics, the latter two defining a former ice stream.Glaciological inferences can be extended by examining the sediments and processes that produced each landform set. Ground-moraine sediments were produced mainly subglacially from melt out or lodgment of glacial debris. Hummocky moraine resulted from debris flow and meltwater deposition controlled by ice, from resedimentation by sediment gravity flow, and from slump. Compressional shearing stacked thick deposits of drift prior to resedimentation. Simple lateral or end moraines may comprise interbedded sediment gravity flows deposited at static ice margins. Deformed lateral moraines resulted from intense marginal compressive flow that sheared and stacked thick, coarse sediment ridges or plates. This lateral shearing may be attributed to streaming or large ice surges. Drumlin exposures showed undeformed, interbedded, stratified sediments that appear to have accumulated in a subglacial cavity; there is no deformation related to high subglacial stress. Subglacial meltwater floods may have followed glacier surge. The greatly extended and thinner ice mass produced by the surge melted in place as clean (debris-free) ice.

scholarly journals Regional stagnation of the western Keewatin ice sheet and the significance of meltwater corridors and eskers, northern Canada

2021 ◽  
Author(s):  
David Sharpe ◽  
Jerome Lesemann ◽  
Ross Knight ◽  
Bruce Kjarsgaard
Keyword(s):  
Surface Modification ◽  
Land Surface ◽  
Regional Scale ◽  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Field Observations ◽  
Remotely Sensed Data ◽  
Northern Canada ◽  
Significant Events ◽  
Patterns And Processes

The glacial landsystem of western Keewatin region, northern Canada, consists of three significant events. First, was regional emplacement of subglacial sediments, mainly till (a pre-existing landscape). Second, was regional-scale erosion (land surface modification) leading to development of an integrated, anabranched network of meltwater drainage routes producing meltwater corridors. Third, was deposition of an extensive array of eskers, and related forms, within meltwater corridors. Integration of field observations, mapping and remotely-sensed data allow us to link scoured bedrock and till surfaces, truncated drumlins, scour pits, glaciofluvial terraces, boulder lags, and the extensive network of erosional corridors, as part of regional meltwater erosion events. The network of long (~100-200 km), relatively wide (~1-3 km) meltwater corridors record confined subglacial erosion that scoured sediment (and bedrock) prior to glaciofluvial sedimentation (predominately eskers). Despite considerable sediment erosion along corridors, moraines and other ice-marginal deposits are rare on the western Keewatin landscape. The absence of these features is inconsistent with deglacial models relying on step-wise active retreat of the ice-margin. Instead, we propose that deglaciation of the western Keewatin Sector of the Laurentide Ice Sheet (LIS) was controlled by regional thinning and stagnation. These findings raise fundamental questions about deglacial patterns and processes and thus suggest that further evaluation and revision of existing models of deglacial chronology for this sector of the LIS is needed..

scholarly journals Central Himalayan rivers record the topographic signature of erosion by glacial lake outburst floods

2021 ◽  
Author(s):  
Maxwell P. Dahlquist ◽  
A. Joshua West
Keyword(s):  
Regional Scale ◽  
Glacial Lake ◽  
River Channels ◽  
Nepal Himalaya ◽  
River Incision ◽  
Outburst Floods ◽  
Glacial Lake Outburst Floods ◽  
Bedrock Erosion ◽  
River Valleys ◽  
Future Work

Abstract. In steep landscapes, river incision sets the pace of landscape evolution. Transport of coarse sediment controls incision by evacuating material delivered to river channels by landslides. However, large landslide-derived boulders that impede bedrock erosion are immobile even in major runoff-driven floods. Glacial lake outburst floods (GLOFs) mobilize these boulders and drive incision, yet their role in regional-scale erosion is poorly understood, largely because of their rarity. Here, we find a topographic signature consistent with widespread GLOF erosion in the Nepal Himalaya. In rivers with glaciated headwaters that generate GLOFs, valleys stay narrow and relatively free of sediment, with bedrock often exposed to erosion. In turn, tributaries to these valleys are steep, allowing less efficient erosional regimes to keep pace with GLOF-driven incision. Where GLOFs are less frequent, valleys are more alluviated and incision stalls. Our results suggest the extent of headwater glaciation may play an important role in erosion of Himalayan river valleys and deserves more attention in future work.

scholarly journals Hazardous geomorphic processes in the extratropical Andes with a focus on glacial lake outburst floods

2021 ◽  
Author(s):  
◽  
Pablo Iribarren Anacona
Keyword(s):  
Hazard Analysis ◽  
Regional Scale ◽  
Glacial Lake ◽  
Rock Falls ◽  
Flow Models ◽  
Territorial Planning ◽  
Outburst Floods ◽  
Glacial Lake Outburst Floods ◽  
Multi Phase ◽  
Frequency Magnitude

<p>This study examines hazardous processes and events originating from glacier and permafrost areas in the extratropical Andes (Andes of Chile and Argentina) in order to document their frequency, magnitude, dynamics and their geomorphic and societal impacts. Ice-avalanches and rock-falls from permafrost areas, lahars from ice-capped volcanoes and glacial lake outburst floods (GLOFs) have occurred in the extratropical Andes causing ~200 human deaths in the Twentieth Century. However, data about these events is scarce and has not been studied systematically. Thus, a better knowledge of glacier and permafrost hazards in the extratropical Andes is required to better prepare for threats emerging from a rapidly evolving cryosphere.  I carried out a regional-scale review of hazardous processes and events originating in glacier and permafrost areas in the extratropical Andes. This review, developed by means of a bibliographic analysis and the interpretation of satellite images, shows that multi-phase mass movements involving glaciers and permafrost and lahars have caused damage to communities in the extratropical Andes. However, it is noted that GLOFs are one the most common and far reaching hazards and that GLOFs in this region include some of the most voluminous GLOFs in historical time on Earth. Furthermore, GLOF hazard is likely to increase in the future in response to glacier retreat and lake development. To gain insight into the dynamics of GLOFs I create a regional-scale inventory of glacier lakes and associated hazards in the Baker Basin, a 20500 km2 glaciated basin in the Chilean Patagonia. I also simulate and reconstruct moraine- and ice- dammed lake failures in the extratropical Andes using numerical and empirical models.  More than 100 GLOFs have occurred in the extratropical Andes since the Eighteenth Century and at least 16 moraine-dammed lakes have produced GLOFs. In the extratropical Andes most of the failed moraine-dammed lakes were in contact with retreating glaciers and had moderate (> 8°) to steep (>15°) outlet slopes. Ice-dammed lakes also produced GLOFs in the extratropical Andes, damaging communities and highlighting the need for a better understanding of the GLOF dynamics and hazards. Thus, I reconstruct and model GLOFs that occurred in maritime western Patagonia (Engaño Valley) and the high-arid Andes (Manflas Valley) to characterise the GLOF dynamics in these contrasting environments.  Hydraulic modelling and geomorphologic analysis shows that the Engaño River GLOF (46º S) behaved as a Newtonian flow and incorporated tree trunks, from the gently sloping and heavily-forested valley, which increased the GLOF damaging capacity. In contrast, the Manflas GLOF (28º S) descended from a steep valley behaving as a sediment-laden flow, which was capable of moving boulder-size rocks dozens of kilometres from the GLOF source. In both events lack of awareness of the GLOF hazard and a lack of territorial planning accentuated the GLOF damage. These GLOF reconstructions highlight both the difficulties in modelling sediment-laden flows over long distances, and the utility of empirical debris-flow models for regional-scale hazard analysis.  This thesis synthesises and increases our knowledge about the distribution, frequency, magnitude and dynamics of hazardous processes that have occurred in glacier and permafrost areas in the extratropical Andes. This knowledge forms a basis for future assessments of glacier and permafrost related hazards in the Chilean and Argentinean Andes and helps inform strategies and policies to face hazardous geomorphologic and hydrological processes emerging from a rapidly evolving cryosphere.</p>

scholarly journals Regional-scale meltwater erosion and deposition patterns, northern Quebec, Canada

1996 ◽  
Vol 22 ◽  
pp. 85-92 ◽  
Author(s):  
T. A. Brennand ◽  
J. Shaw ◽  
D. R. Sharpe
Keyword(s):  
Regional Scale ◽  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Outburst Flood ◽  
Erosion And Deposition ◽  
Sedimentary Characteristics ◽  
Large Sector ◽  
Glaciofluvial Deposits ◽  
Flow Convergence ◽  
Local Patterns

Glaciofluvial ridges, several hundred kilometres long, are commonly referred to as interlobate moraines because they appear to have formed at the convergence of two distinct ice lobes. Flow convergence is indicated by patterns of striations, streamlined forms and eskers. The so-called interlobate moraines are also thought to have formed asynchronously as the ice margin retreated. By contrast, we argue that the Harricana moraine of northern Quebec, Canada, formed following flow convergence in a regional-scale subglacial outburst flood. Flowlines constructed from streamlined bedforms mapped on the glacial map of Canada, reinterpretation of these streamlined forms as products of meltwater erosion, and field records of erosional marks (S-forms) in bedrock and glaciofluvial deposits to the lee of bedrock highs support this model. The effects of this flow convergence on the ice-sheet topography and drainage controlled the location of the broad conduit in which the Harricana moraine was deposited. Continued flow in this conduit and melting of the conduit walls explain the local patterns of striae, the supply of debris to the conduit, and the morphological and sedimentary characteristics of the moraine itself. From these characteristics, we conclude that the moraine was formed synchronously. This conclusion, if correct, is instructive regarding the deglacial hydrological organization of a large sector of the Laurentide ice sheet.

Economic Decision Making and the Application of Nonparametric Predition Models

2008 ◽  
Vol 11 (06) ◽  
pp. 1089-1096 ◽  
Author(s):  
Emil D. Attanasi ◽  
Tim Coburn ◽  
Philip Freeman
Keyword(s):  
Prediction Models ◽  
Regional Scale ◽  
Economic Models ◽  
Focused Attention ◽  
Michigan Basin ◽  
Energy Prices ◽  
Worked Example ◽  
Model Predictions ◽  
Reduce Risk ◽  
Recoverable Resources

Summary Sustained increases in energy prices have focused attention on gas resources in low-permeability shale or in coals that were previously considered economically marginal. Daily well deliverability is often relatively small, although the estimates of the total volumes of recoverable resources in these settings are often large. Planning and development decisions for extraction of such resources must be areawide because profitable extraction requires optimization of scale economies to minimize costs and reduce risk. For an individual firm, the decision to enter such plays depends on reconnaissance-level estimates of regional recoverable resources and on cost estimates to develop untested areas. This paper shows how simple nonparametric local regression models, used to predict technically recoverable resources at untested sites, can be combined with economic models to compute regional-scale cost functions. The context of the worked example is the Devonian Antrim-shale gas play in the Michigan basin. One finding relates to selection of the resource prediction model to be used with economic models. Models chosen because they can best predict aggregate volume over larger areas (many hundreds of sites) smooth out granularity in the distribution of predicted volumes at individual sites. This loss of detail affects the representation of economic cost functions and may affect economic decisions. Second, because some analysts consider unconventional resources to be ubiquitous, the selection and order of specific drilling sites may, in practice, be determined arbitrarily by extraneous factors. The analysis shows a 15-20% gain in gas volume when these simple models are applied to order drilling prospects strategically rather than to choose drilling locations randomly. Introduction Sustained increases in energy prices have focused attention on the development of marginally economic resources such as natural gas in low-permeability shale or in coal. The daily deliverability of these resources from individual wells is often relatively small, whereas the estimates of the total volume of recoverable resources in these settings are often large. Planning and development decisions for extraction of such resources are, by nature, areawide because profitable extraction requires the optimization of scale economies to minimize costs and reduce risk. For an individual firm, the decision to enter such plays depends on reconnaissance-level estimates of regional recoverable resources and on cost estimates to develop untested areas. This paper demonstrates how simple nonparametric-regression-model predictions of technically recoverable unconventional gas resources at untested sites can be used with economic models to compute, at the regional scale, the costs of developing and producing such resources in partially developed areas. The predictive models are described in the next section. Following this description, the data, prediction results, and the predictive distributions of recoverable gas volumes are discussed. The assumptions and fundamental components of the economic analysis are then presented. The paper also demonstrates the benefits of applying the model predictions in the strategic ordering of drilling prospects and the benefit of updating predictions when the results of new drilling become available. The cost models provide a way to evaluate the economic payoff associated with the application of local prediction models. A worked example, that used data from the Devonian Antrim-shale gas play of the Michigan basin, provides the context for testing the usefulness of the local prediction models at the regional scale and also for strategic drilling decisions. In summary, the analysis shows that these models can be applied usefully to assess the regional economic potential and, at the strategic level, to rank prospects by order of value in partially developed areas.

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