Speleothems and paleoglaciers, , Spotl Christoph, Mangini Augusto,

Ice and speleothems are widely regarded as mutually exclusive as the presence of liquid water is a fundamental prerequisite for speleothem deposition. Here we show that speleothems may form in caves overlain by a glacier, as long as the temperature in the cave is above freezing and the conduits are not completely flooded by melt water. Carbonate dissolution is accomplished via sulfide oxidation and the resultant speleothems show high [delta]13C values approaching and locally exceeding those of the parent host rock (lack of soil-derived biogenic C). The [delta]18O values reflect the isotopic composition of the melt water percolating into the karst fissure network and carry an atmospheric (temperature) signal, which is distinctly lower than those of speleothems formed during periods when soil and vegetation were present above the cave. These `subglacial' speleothems provide a means of identifying and dating the former presence of warm-based paleoglaciers and allow us to place some constraints on paleotemperature changes

The Hydrology of a Glacierised Alpine Karst Castlegaurd Mountain, Alberta, PhD Thesis, 1983, Smart, Charles Christopher

Alpine karst throughout the world has been affected by past glaciation, and yet little is known of the interactions between glacier ice and karst. This dissertation attempts to gain some understanding of the problem through the study of the Castleguard Area, Alberta, where a karst aquifer is presently overlain by temperate glacier ice.
Quantitative fluorometric tracing and hydrometric measurements generated a broad data base on aquifer behaviour. Tracer breakthrough curves were interpreted using a new systematic approach which considers an explicit set of processes likely to affect the particular tracer under the given experimental conditions. Non-linearity in aquifer behaviour and rapid groundwater velocities demonstrated the aquifer to be an extreme conduit type Conduit springs are elements in a vertical hierarchy in which the topmost springs are "overflows" and exhibit greater flow variability than their associated "underflows". A numerical model was developed to simulate a conduit aquifer. It demonstrated that pulse train and recession analysis widely accepted methods of karst aquifer investigation, could be rather misleading when applied to conduit aquifers.
Interactions between ice and groundwater were observed at two scales: regulation water appeared to feed a diffuse percolation system and supraglacial melt passed into subglacial conduits which entered open vadose shafts. Karst is unlikely to be entirely subglacial in origin because of the limited aggressiveness of subglacial waters.
The Castlegaurd karst appeared to have originated preglacially in response to the breaching of impermeable caprock. Glaciation re-ordered the landscape and produced abundant clastic debris which subsequently blocked or obstructed karst conduits. Much of the resulting karst is paragenetic and comparatively immature due to glacial disruption and slow growth rates. Geomorphic and hydrologic interactions between ice and karst depend intimately upon the relationship between the geographic zones of the glacier and the aquifer.

Glacier Caves and Subglacial Water in Nordland, Norway, 1988, Theakstone W.

Drainage Evolution in a Tasmanian Glaciokarst, 1989, Kiernan, Kevin

The intensively glaciated mountains of the Picton Range - Mt. Bobs area in southwestern Tasmania contain prominent karst features that have been developed in carbonate formations of Devonian, Ordovician and possibly Precambrian age. This paper reviews the extent of the karst and glacial features and records the tracing of the underground drainage from the alpine Lake Sydney. Glacial erosion has exposed areas of limestone to karstification and glacial diversion of drainage has played a critical role in the evolution of the present underground drainage patterns. Prior to the late Last Glacial Stage the deflection of marginal meltwaters from the former Farmhouse Creek Glacier against the Burgess - Bobs Saddle led to the development of an underground breach of a major surface drainage divide. Subglacial or submarginal meltwaters associated with a much smaller glacier that developed in the same valley during the late Last Glacial Stage probably played a significant role in the breaching of a minor divide within the Farmhouse Creek catchment. This led to the development of an underground anabranch of Farmhouse Creek that by-passes the glacial Pine Lake. However, it is possible that the latter diversion is entirely Holocene in age and is related to postglacial dilation of the limestone rather than meltwater flows.

Karst features of a glaciated dolomite peninsula, Door County, Wisconsin, 1990, Johnson Scot B. , Stieglitz Ronald D. ,

A geologic investigation of the northern part of Door Peninsula, Wisconsin for a state funded water quality project revealed that karstification of the Silurian aquifer is more extensive than previously believed. Sinkholes and small insurgent features, solution modified crevices, pavements, caves and springs were inventories and mapped. These features are generally smaller and less densely developed than those in most limestone terranes; however, they are important to the geomorphology and water quality of the peninsula.Continental glaciation has strongly influenced both the distribution and the present surface morphology of the karst features. Ice scour has formed a stepped bedrock topography, contributed to pavement formation and may have removed some preglacial features. Deposition has plugged and masked features in places. In addition, subglacial water circulation, and ice loading and unloading may have influenced karst development

Karst Geomorphology and Hydrogeology of the Northeastern Mackenzie Mountains, District of Mackenzie, N.W.T., PhD Thesis, 1995, Hamilton, James P.

This thesis describes the geomorphology and hydrogeology of karst systems in portions of the northeastern Canyon Ranges of the Mackenzie Mountains and the Norman Range of the Franklin Mountains. N.W.T. In the region, mean annual temperatures are -6 to -8°C, total annual precipitation is 325 to 500 mm, and permafrost has a widespread to continuous distribution. The area was glaciated in the Late Wisconsinan by the Laurentide Ice Sheet.
The Canyon Ranges and Norman Range are composed of a sequence of faulted and folded miogeoclinal sedimentary rocks that span the Proterozoic to Eocene. The geology is reviewed with an emphasis on strata that display karst. Included are several dolomite and limestone formations, two of which are interbedded with evaporites in the subsurface. The principal groundwater aquifer is the Lower Devonian Bear Rock Formation. In subcrop, the Bear Rock Formation is dolomite and anhydrite, outcrops are massive calcareous solution breccias. This is the primary karst rock.
The regional distribution and range of karst landforms and drainage systems are described. Detailed mapping is presented from four field sites. These data were collected from aerial photography and ground surveys. The karst has examples of pavement, single and compound dolines, subsidence troughs, polje, sinking streams and lakes. and spring deposits. The main types of depressions are subsidence and collapse dolines. Doline density is highest on the Bear Rock Formation. Surficial karst is absent of less frequent in the zone of continuous permafrost or outside the glacial limit.
At the field sites, water samples were collected at recharge and discharge locations. Samples were analyzed for a full range of ionic constituents and many for natural isotopes. In addition, several springs were monitored continuously for discharge, temperature, and conductivity. Dye tracing established linkages between recharge and discharge at some sites. These data are summarized for each site, as is the role of permafrost in site hydrology.
The relationships between geological structure, topography, ,and groundwater systems are described. Conduit aquifers are present in both dolomite and limestone. These systems are characterized by discharge waters of low hardness and dissolved ion content. Aquifers in the Bear Rock Formation have a fixed flow regime and often have highly mineralized discharge. At the principal field site. there was a time lag of 40 to 60 days between infiltration and discharge in this unit. At a second site, flow through times were on the order of years. Variability in these systems is attributed to bedrock properties and boundary conditions.
Preliminary rates of denudation are calculated from the available hydrochemical data. Total solutional denudation at the primary field site is approximately 45 m³ kmˉ² aˉ¹ (mm kaˉ¹). The majority is attributed to the subsurface dissolution of halite and anhydrite. The predominance of subsurface dissolution is linked to the high frequency of collapse and subsidence dolines and depressions.
The karst features and drainage systems of the northern Mackenzie Mountains date to the Tertiary. Glaciation has had a stimulative effect on karst development through the subglacial degradation of permafrost and the altering of boundary conditions by canyon incision.

Interaction between glacier and karst aquifers: Preliminary results from Hilmarfjellet, South Spitsbergen, 1996, Lauritzen, Steinerik

Statistical evaluation of glacier boreholes as indicators of basal drainage systems, 1996, Smart C. C. ,

Between 1988 and 1992 closely spaced arrays of boreholes were drilled at Small River Glacier, British Columbia. The borehole arrays have been used to investigate the interannual and spatial consistency of patterns of basal hydraulics beneath the glacier. A simple robust classification was devised identifying unconnected, high standing, low standing and dry base water levels in boreholes. Spatial and interannual comparisons were made using a simple nearest neighbour statistic, corrected for differences in frequency of different borehole types and evaluated using Monte Carlo confidence intervals to compensate for array form. Arrays in the lower ablation zone showed spatial and interannual coherence, with three distinct areas characterized by low water pressure, till-associated non-connection and high pressure. There was no indication of a dominant conduit. Slightly higher up-glacier borehole patterns were less coherent, and varied from year to year, probably a result of subglacial karst capturing basal waters at a number of low pressure points at the bed. Therefore both the upper and lower arrays at Small River Glacier appear to encompass unusual drainage conditions. The nearest neighbour analysis provides valuable constraints on more specific interpretation

Hydrogeology of glacial and subglacial karst aquifers: Small River, British Columbia, Canada., 1997, Smart C. C.

The Small River Glacier overlies two active conduit karst aquifers and has been studied to understand the nature of subglacial karst hydrology. Profoundly undersaturated surface meltwaters recharge the karst through moulins focused on the crest of large hummocks. Supraglacial traces reached karst springs faster than extraglacial waters, perhaps a result of paraglacial occlusion of sinks beyond the glacier margin. Glacier-karst flow routes were open channel and maintain very low (atmospheric) water pressures at the glacier bed. Variable divergence of replicate traces demonstrated that hydrogeographic divides were fuzzy and unstable. Divergence occurs through overflow and hydraulic switching rather than changes in the conduit. Subglacial flow followed a complex "submarginal" drainage system to the snout which gave highly anomalous hydraulic characteristics.

Symposium Abstract: The sediments of Illusion Pot, Kingsdale - Evidence for subglacial utilisation of a Karst Conduit in the Yorkshire Dales?, 1998, Murphy P. J. , Smallshire R. , Midgley C.

Bedrock surface roughness and the distribution of subglacially precipitated carbonate deposits: implications for formation at Glacier de Tsanfleuron, Switzerland., 1998, Hubbard B. , Hubbard A.

Glaciokarst of subalpine and alpine zone of the Mala làka Valley, Tatra Mts., Poland, 1999, Gà, Dek Bogdan, Litwin Leszek

The results of the analysis of the location, origin and age of glacial and karst forms in the Mala làka Valley (the Polish Western Tatras) indicate some interactions between the glacier which existed here in Würm and the karst substratum. During the last glacial period, part of the subglacial water drained underground karst systems. This limited the velocity of the glacier slide on the bedrock which, in turn, led to the decrease of glacier erosional force and to the decrease of glacier front. The older karst relief of the valley surface became devastated but the cave systems became rejuvenated.

24 h Tracer Tests on Diurnal Parameter Variability in a Subglacial Karst Conduit: Small River Valley, Canada., 2001, Ross Jh. , Serefiddin F. , Hauns M. , Smart C. C.

Repeated dye tracer tests were undertaken for two complete diurnal discharge cycles at Small River Glacier, British Columbia. The injection site is a well developed glacier moulin. Monitoring was done at a karst spring in a cave entrance 1530 m down valley. The spring is the major outlet of glacial meltwater and also drains karstified glacier forefields. High flow velocities and low dispersivities indicate a very well developed conduit flow system. Discharge and velocity show strong diurnal cycles and are controlled by the amount of meltwater. The relationship of increasing velocity with discharge is approximately linear. Dispersivity values do not show any significant variation under diurnal discharge cycles. These results show the importance of diurnal variation in a transient groundwater system.

Notion and forms of contact karst, 2001, Gams, Ivan

These forms are through valley, blind valley, karst plain, cave with allogenic river, overflow polje, cave on the impermeable rock, subglacial karst and interstratal karst. Emphasized is the role of climate and alluvium for closed basins by comparing Wombeyan cave area in Australia with polje Velo polje in Julian Alps (Slovenia). In the temperate humid alpine climate is intensive mechanical weathering on the steep and bare slopes above Velo polje (1680 m) and steep dry valley rising up to 2200 m. After heavy downpour the periodical brook Velski potok is sinking on the 400 m wide bottom and depositing new sheet of rubble, sand and organic particles. This process lasted since last glacier retreat 9 - 10,000 years ago. Despite age of many hundred million years and confluence of two rivers from surroundings built of igneous rocks on southern corner of 3,6 km2 large isolated Wombeyan marble there prevail gorges, caves and narrow valleys without large alluviated bottoms, and the surface is not levelled. The main reasons for the difference are in this view the semi-arid climate and the absence of alluvium causing larger and longer moist contact of alluvium with limestone basis.

Melting of the glacier base during a small-volume subglacial rhyolite eruption: evidence from Blahnukur, Iceland, 2002, Tuffen H. , Pinkerton H. , Mcgarvie D. W. , Gilbert J. S. ,

Although observations of recent volcanic eruptions beneath Vatnajokull, Iceland have improved the understanding of ice deformation and meltwater drainage, little is known about the processes that Occur at the glacier base. We present observations of the products of a small-volume, effusive subglacial rhyolite eruption at Blahnukur. Torfajokull, Iceland. Lava bodies, typically 7 m long, have unusual conical morphologies and columnar joint orientations that suggest emplacement within cavities melted into the base of a glacier. Cavities appear to have been steep-walled and randomly distributed. These features can be explained by a simple model of conductive heat loss during the ascent of a lava body to the glacier base. The released heat melts a cavity in the overlying ice. The development of vapour-escape pipes in the waterlogged, permeable breccias surrounding the lava allows rapid heat transfer between lava and ice. The formed meltwater percolates into the breccias, recharging the cooling system and leaving a steam-filled cavity. The slow ascent rates of intrusive rhyolitic magma bodies provide ample time for a cavity to be melted in the ice above, even during the final 10 m of ascent to the glacier base. An equilibrium Cavity Size is Calculated at which melting, is balanced by creep closure, This is dependent upon the heat input and the difference between glaciostatic and cavity pressure. The cavity sizes inferred from Blahnukur are consistent with a pressure differential of 2-4 MPa, suggesting that the ice was at least 200 m thick. This is consistent with the volcanic stratigraphy, which indicates that the ice exceeded 350 in in thickness, Although this is the first time that a subglacial cavity system of this type has been reconstructed from an ancient volcanic sequence. it shares many characteristics with the modem fim cave system formed by fumarolic melting within the summit crater of Mount Rainier. Washington, At both localities, it appears that localised heating at the glacier base has resulted in heterogeneous melting patterns. Despite the different theological properties of ice and fim, similar patterns of cavity roof deformation are inferred. The development of low-pressure subglacial cavities in regions of high heat nux may influence the trajectory of rising magma, with manifold implications for eruptive mechanisms and resultant subglacial volcanic landforms. (C) 2002 Elsevier Science B.V. All rights reserved