. Bulletin of the Essex Institute. Essex Institute; Natural history; genealogy. SOME GLACIAL WASH-PLAINS. 79. lins, eskers, kames and terraces, in the classification of glacial deposits. So far as glacial drainage repeats the conditions exist- ing in ordinary streams and rivers, we should expect to find, at the mouths of rivers and streams discharging from the ice, alluvial deposits corresponding in all essential re- spects to deltas with lobate and multilobate margins, to alluvial cones and fans, and to confluent cones and fans. The examination of the region here described has revealed exampl
. Bulletin of the Essex Institute. Essex Institute; Natural history; genealogy. SOME GLACIAL WASH-PLAINS. 79. lins, eskers, kames and terraces, in the classification of glacial deposits. So far as glacial drainage repeats the conditions exist- ing in ordinary streams and rivers, we should expect to find, at the mouths of rivers and streams discharging from the ice, alluvial deposits corresponding in all essential re- spects to deltas with lobate and multilobate margins, to alluvial cones and fans, and to confluent cones and fans. The examination of the region here described has revealed examples analogous to most of these types, differing only in the respect that the deposits were built against or in the presence of an ice formation instead of a rock formation and that, by the melt- ing of the ice, anomalies in the to- pography have been introduced which separate the group, often widely, from those deposits of non-glacial origin. The following classes of glacial stream deposits are here recognized under the head of extraglacial wash : Wash-plains, comprising gently slop- ing areas of gravel and sand deposited along the ice front. They are divisible into kinds dependent on their relations to frontal moraines, the ice-margin, and to the ice-margin and eskers. From their relations to frontal moraines there arise over- wash-plains banked up against the outer edge of the frontal moraine. From their relation to the ice-margin alone there arise : a. Frontal moraine terraces, with an ice-contact slope, charged with till and boulders, a true morainal deposit. b. Frontal terraces, like the preceding but lacking the till-coating along the ice contact. /Mile Fig. 1. Contour map of the Say les vil le esker-fan (area left white) in Rhode Isl- and. Horizontally ruled areas, swamps; black areas, ponds; dotted areas marginal terraces of sand and gravel. (Topography from Providence atlas sheet, U. S. Geological Survey.). Please note that these images are extracted from scanned page i
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