ABSTRACT: Do eskers provide local and regional provenance signals for mineral exploration?

CGRG Bibliography of Canadian Geomorphology
Search Results

Author :

Date :

Title :

Publication :

Issue :

Page(s) :

Abstract

Large esker systems have a tree-shaped tributary character similar to fluvial systems and can exceed several hundred kilometres in length. This, among other things, has led to the suggestion that such eskers form "synchronously" within a dendritic system of meltwater stream conduits (R-channels) beneath stagnant or sluggish ice. Perhaps guided by this, some workers in mineral exploration have adopted the viewpoint that eskers act as regional pathfinder vectors that record provenance signals from far up-esker. This may be a questionable assumption. A synthesis of data from available studies (a modest number) reveals that eskers in fact have relatively short clastic dispersal trains--typically less than several tens of kilometres--for gravel and (possibly) coarse sand fractions (i.e., bedload). These short dispersal trains are, apparently, best explained if the long, tree-shaped eskers formed time-transgressively in short segments as the ice back-stepped, in a fashion perhaps somewhat analogous to the transgressive infilling of incised fluvial valleys. If these data are representative, which remains to be tested in most parts of northern Canada, bedload in eskers may typically record a relatively proximal provenance signal, one that sampled adjacent and underlying till and bedrock. Esker bedload samples may therefore in some cases be well suited for property-scale investigations. In contrast to gravel, eskerine dispersal of finer sand and mud is less clearly documented. Because finer particles are more susceptible to traveling in suspension, these fractions should be transported farther down the R-channel before they are deposited. Their provenance may therefore be a more powerful test of the shape and length of esker R-channel networks than that of the bedload population. If investigations reveal that finer grain sizes are in fact regional vectors, eskers could potentially serve the dual function of providing both local and regional provenance information. These and other ideas will be tested over the course of a new multi-year project on glacial sediment dispersal, one whose basic objective is to develop scientifically rigorous, yet easy- to-understand, sampling protocols and conceptual models to help guide mineral exploration in Canada. DE: 0726 Ice sheetsDE: 0766 Thermodynamics (1011, 3611, 8411)DE: 0776 Glaciology (1621, 1827, 1863)DE: 1824 Geomorphology: general (1625)DE: 1862 Sediment transport (4558)SC: Geological Association of Canada [GA]MN: 2009 Joint Assembly

Bibliography of Canadian Geomorphology