Abstract: Applied Quaternary geology and till geochemistry of the Loch Lomond region, Cape Breton Island, Nova Scotia
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Southeastern Cape Breton Island is host to several fonner industrial minerals and base metals mines discovered by traditional prospecting methods but present exploration is hampered by a complex glacial history. Late Wisconsinan ice advances resulted in the deposition of five distinct tills. The basal grey till (LLI) is a compact, fine-grained till found in local depressions. The regional red till contains 10-30% clasts, 20-30% clay, and was deposited by an eastward ice advance (LL2). Northward (LL-3) and southward (LL4) ice flows were responsible for two hybrid tills that fonned in part through inheritance and overprinting. The local stony till was fonned by a southeasterly ice flow event (LL-5) and contains 35-75% angular local clasts and less than 10% clay. The southern half of the study area is dominated by 50 m high bedrock cored till ridges. Inter ridge areas are overlain by organic deposits and glaciofluvial sediments which can provide anomalous geochemical values. Till samples were collected at a 3-5 km spacing and the <0.063 mm fraction was analyzed. Till geochemical patterns are complex as a result of lithological repetition, complex glacial history, and numerous mineralization types. Considered together stratigraphic, geochemical, and till pebble data indicate that all 5 stratigraphic units have surface expression in the study area necessitating a multi-tiered interpretation of the geochemical datasets. The re-evaluated data suggest that the regional red till which is located primarily in the Loch Lomond basin isKeywords:
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Drift prospecting is defined as the application of glacial geologic, geochemical, geophysical and sedimentological techniques to the problem of mineral exploration in areas mantled by glacial overburden. Glacial drift in the Sheffield Lake - Indian Pond area of north central Newfoundland contains local accumulations of massive sulphide float, grading up to 8.2% Cu. Previous investigations by industry have failed to locate the source of the float. -- The objects of this research were to locate the source of the float by means of drift prospecting, to evaluate the applicability of combined exploration techniques to the glaciated terrain of Newfoundland and to resolve the glacial history of the study area. -- Glacial drift thickness in the area, determined by hammer seismic profiling, varies from 5 to 60 feet. An extensive trenching program revealed the presence of two till units. Till fabric analyses indicated local ice flow directions toward 020 for the Lower Red Till, and either 020-045 (low) or 000-315 (high) for the Upper Grey Till. The sulphide float occurs as first-cycle clasts only in the Lower Red Till and, sparsely, as second-cycle clasts in the Upper Grey Till. The two lodgement tills have been differentiated on the basis of colour, stratigraphy, fabric, texture, pebble lithology, clay mineralogy and geochemistry. The two tills provide the first conclusive evidence of multiple glaciation in north central Newfoundland. -- The sulphide float, which generally weighs 1-5 lbs., ranges in composition from weakly pyritized and chloritized (host) andesite to massive phyrite-chalcopyrite. Clasts are concentrated in the Lower Red Till where they form a well-defined dispersion fan with the apex pointing toward the southwest. Anomalous concentrations of Cu, Fe, S, Co, and Zn in the Lower Red Till likewise indicate a southwesterly bedrock source of the micro-float dispersion fan. A target area for further detailed exploration of the bedrock source of the float has been delineated on this basis. -- It was determined that the combination of methods employed was essential for delineating the probable source area and it is recommended that they be employed in any future investigations with similar objectives. Of the methods employed, trenching with a backhoe and geochemical analysis of only a restricted size fraction of till samples were found to be particularly valuable. Cu, Fe, and S were found to be the best geochemical tracer elements, particularly when they were mutually associated.
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The Quaternary stratigraphy of the Babine Lake region is characterized by a Late Wisconsinan succession of advance-phase glaciolacustrine sediments, glaciofluvial deposits, and till. Pollen data from a rare new interglacial site suggest a colder than present Middle Wisconsinan climate. Ice flow during the last glaciation was dominantly southeasterly, but in the Babine Range a regional, westerly ice-flow event occurred. Evidence for westerly flow diminishes eastward of Babine Lake, suggesting that the valley was near the eastward limit of an interior ice divide. Deglacial sediments include ice-marginal debris-flow, glaciofluvial, and glaciolacustrine sediments. Raised-delta elevations indicate that Glacial Lake Babine extended nearly 150 m above present lake level to 850 m asl, and higher, earlier phases may have existed locally. A variety of Holocene deposits cap the Quaternary succession. Glaciation has important implications for exploration in this copper-producing area. Southeasterly glacial dispersal patterns dominate, despite a regionally complex ice-flow history. Highly anomalous concentrations of copper occur in tills down-ice of most known bedrock copper occurrences, and a number of similarly anomalous till sites with no known copper sources have been identified in drift-covered areas. Exploration problems due to the thick and complex surficial cover can be overcome by selective sampling of basal tills, the composition of which clearly reflects the presence of buried mineral deposits. The effectiveness of till geochemistry as a method for locating buried mineralization in the region will be enhanced by careful selection of sample media and by a clear understanding of the glacial history.
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Research Article| November 01, 1983 Till stratigraphy in the St. Lawrence Valley near Malone, New York: Revised glacial history and stratigraphic nomenclature PETER CLARK; PETER CLARK 1Institute of Arctic and Alpine Research and Department of Geological Sciences, University of Colorado, Boulder, Colorado 80309 Search for other works by this author on: GSW Google Scholar P. F. KARROW P. F. KARROW 2Department of Earth Sciences, University of Waterloo, Waterloo, Ontario, Canada N2L3G1 Search for other works by this author on: GSW Google Scholar Author and Article Information PETER CLARK 1Institute of Arctic and Alpine Research and Department of Geological Sciences, University of Colorado, Boulder, Colorado 80309 P. F. KARROW 2Department of Earth Sciences, University of Waterloo, Waterloo, Ontario, Canada N2L3G1 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1983) 94 (11): 1308–1318. https://doi.org/10.1130/0016-7606(1983)94<1308:TSITSL>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation PETER CLARK, P. F. KARROW; Till stratigraphy in the St. Lawrence Valley near Malone, New York: Revised glacial history and stratigraphic nomenclature. GSA Bulletin 1983;; 94 (11): 1308–1318. doi: https://doi.org/10.1130/0016-7606(1983)94<1308:TSITSL>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Compositional parameters are defined for till samples collected from 48 sites in the type areas of the Malone and Fort Covington tills in the St. Lawrence Valley, New York. Till compositional variations are related directly to the influence of the underlying bedrock and are interpreted as facies changes that occur within one extensive till unit. The Fort Covington-Malone drift boundary as previously mapped is disputed. The single till sheet ranges from a gray, silty sand, carbonate-rich facies where underlain by dolostone bedrock in the north to a red, sandy, carbonate-depleted facies where underlain by sandstone and Precambrian metamorphic bedrock to the south. In contrast to previous studies, till fabrics failed to distinguish units and were not useful for correlation.Surface till in the area is correlated with the upper till exposed in St. Lawrence Seaway excavations. The name Fort Covington Till is retained but extended to include surface till in the Adirondack Highlands. The lower till exposed in the Seaway does not outcrop in the area, and the name Malone Till should no longer be used.The surface till may represent glaciation at least throughout the late Wisconsinan. Extension of ice into the Adirondack Highlands is suggested by continuity of the till sheet and by ice flow indicators throughout the Lowlands. Major physiographic elements influenced ice movement in that ice was channeled southward through the Champlain Basin, southwesterly parallel to the St. Lawrence River into the Ontario Basin, and southward into the Adirondacks in a lesser flow strength. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
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Outwash plain
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SUMMARY A study of the vertical and lateral variations in particle size distribution, mineralogy and other petrographic features of tills in East Yorkshire, Lincolnshire and north Norfolk shows that the Devensian glacial succession in eastern England contains only two tills, for which the new names Skipsea and Withernsea Tills are proposed. The “Hessle Till”, recognised as a third member by most previous workers, is shown to be the postglacial (Flandrian) weathering profile on whichever of these two occurs at the surface. South of Flamborough Head, the upper (Withernsea) till occurs on land only in an arcuate area adjoining the coast of south-east Holderness. The Skipsea Till occupies the whole of Holderness, and extends westwards on to the lower dip-slope of the Wolds and southwards to the northern coastal strip of Norfolk, where in its weathered form it has previously been known as the Hunstanton Till. These conclusions agree with those reached by Bisat forty years ago, but hitherto unpublished. The weathering of the tills involves decalcification, the softening and disaggregation of sandstone, shale, igneous and metamorphic erratics, clay alteration and translocation, and the alteration of micas and some heavy minerals in the sand and silt fractions. Reddish brown colours, previously regarded as characteristic of the “Hessle Till”, result from oxidation of pyrite and siderite to depths of approximately 5 m.
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Regional till sampling and stratigraphic studies were completed in southeastern Cape Breton Island, Nova Scotia, in 1990 and 1991 to document the directions and distances that successive ice-flow events have dispersed material and to document regional till geochemical patterns to aid mineral exploration in this heavily drift-covered area. Three major Wisconsinan ice-flow events affected the area: an early eastward flow, followed by a northeastward flow, and finally a southward flow. The shape and magnitude of dispersal trains in the area are the net result of the three ice-flow events, which are variable from north to south. In the north, the northeast ice flow was the dominant erosive and depositional event, producing a large northeast-trending drumlin field. Salmon River porphyry clasts and Pb- and Zn-rich till from the Yava Pb mine were dispersed more than 15 krn to the northeast. In the south, eastward ice flow was the dominant erosive and depositional event, producing large east-trending till ridges. Dispersal in this area is difficult to detect because exotic red silty till in the giant till ridges masks underlying mineralized bedrock and dilutes the locally derived glacial debris. Many precious and base metal anomalies and dispersal trains were identified in the regional till samples, several of which are related to unknown mineralized sources.
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Quaternary geological investigations were initiated in the Patterson Island area, Reindeer Lake (part of 64E-10 and -15), as part of the multidisciplinary, multi-year Peter Lake Domain Project. The Quaternary component of the project involves surficial mapping at 1:50 000 scale, recording ice-flow indicators, and regional till sampling surveys. Multiple ice-flow directions were documented. The dominant ice-flow direction was to the south-southwest (205° to 210°); becoming more southwesterly (215° to 220°) towards the southern boundary of the map area. Two older regional ice flows were recorded: a more southerly (~190°) direction and a west-southwesterly (228° to 240°) one. Rare, faint striae sets trending 154°/332o (two sets) and 295°/115o (one set) were also recorded. Drift cover in the Patterson Lake area is variable. In the northern two thirds, the terrain is dominated by bedrock (approximately 40 to 50 percent) mantled with a thin (less than 2 m), discontinuous drift cover. Thus, the present day landscape is controlled by the bedrock topography with little geomorphic expression of the glacial deposits. Southward, the drift thickens and is more extensive, with bedrock exposure less than 10 percent. Here, the landscape is more subdued and reflects both glacial geomorphic features and bedrock topography. The dominant surficial sediments in the Patterson Island area are till and organic deposits. Sand and gravel deposits are associated with esker systems, minor meltwater drainage channels, stagnant ice hummocky moraines, and glaciolacustrine littoral deposits. Minor glaciolacustrine silts and sands are not sufficiently extensive to differentiate at this map scale. Till occurs primarily as ground moraine veneer (less than 2 m thick) and plain (greater than 2 m thick), hummocky moraine and stagnant ice moraine. Ridged moraine and streamlined forms such as drumlins and crag and tails are less common. Till composition varies with the type of deposit, thickness and source rocks from which it is derived. At least three facies were identified: a silty-sand to sandy till, sandy till and a gravely sand diamicton. Sporadic lacustrine deposits and raised strandlines, such as sand and cobble beaches, terraces and wave-cut notches indicate that Glacial Reindeer Lake and glacial Lake Agassiz extended further north and west than originally thought. Much of the area below ~350 m asl is characterised by exposed outcrop, boulder lags and winnowed till. A large part of the northern half of the area is not very suitable for drift prospecting, as bedrock, ice marginal and wave-reworked deposits dominate the terrain. Drift prospecting techniques are more applicable in the south where the drift cover is more extensive. Interpretation of pending till compositional data will help determine the effectiveness of till sampling in this region.
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Surficial mapping (1:50,000 scale) and sampling of Bhorizon soil, basal till and 100 pebbles at each of 406 sites on a 2 km grid is ongoing in NTS 21 0/7 & 8. Till is analyzed for Au + 33 elements, and selected base metals. A till fabric, 264 pebble counts and 486 striae, groove and roche moutonnee measurements indicate an erosive eastward ice movement followed by northeastward and southeastward flowing ice. Lastly, ice flowed in various directions off the Highlands. This is consistent with other areas mapped to the north and south. Periglacial features, suggest that the highest elevations may have been exposed as nunataks during early stages of deglaciation. Granite-boulder erratics from the Mount Elizabeth Intrusive Complex in the center of the area were transported up to 30 km down-ice in an eastnortheast direction. No Canadian Shield erratics have been found. A Late Wisconsinan homogeneous basal till ( <2 m) throughout the area and erratic pebbles in till on the highest elevations suggest that all of the area was glaciated. Ti11 is locally derived. Till thickness increases to the east, as elevations decrease and topography becomes gently rolling. Ablation till and ablation lag over basal till are found in valleys and topographic depressions. Major rivers and brooks contain glaciofluvial (outwash and ice-contact), and postglacial alluvial deposits. Pre-glacial weathered granite (grus); colluvium and bedrock, dominate in steep valleys and on mountains and ridges.
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