Objective:
This exercise is to improve your ability understand the technical literature.
Resources:
Menzies, John, 1990, Sand intraclasts within a diamicton melange, southern Niagara Peninsula, Ontario, Canada, J. of Quat. Science 5 (3), p. 189- 206.
Amark, M, 1986, Glacial tectonics and deposition of stratified drift during formation of tills beneath and active glacier: example from Skane, southern Sweden, Boreas, 15, 155-171.
Background:
We can not be experts on everything. Often we must try to understand some geologic feature without having seen one ourselves. In this case we must depend on descriptions from the technical literature. In essence we must look it up. This approach has limitations because we must depend on our ability to understand what some expert has said about this unknown feature. This lab will give you the chance to read about sand interclasts and decide if such a thing exists in an outcrop. If you can handle sand interclasts you can handle any sedimentary feature.
Sand bodies within "tills" are a problem. First they change the strength of the till locally and second they are very good paths for groundwater flow. To understand the distribution of sand bodies we must first understand how they got into the till in the first place. For the sake of this lab we will consider two ways. First are sand interclasts as described by Menzies (1990). These are inclusions resulting from disruption of an underlying sand bed. The deformation processes make these things into balls and since they have limited extent, they are less of a problem for ground water issues. Second sand lens represent old channels where running water flowed under (or in some cases inside) the glacier. This channel cuts through the diamicton. These are more problematic for ground water issues because they have a ribbon distribution that can collect water from a large area. However since they can form in the subglacial setting they may be deformed. Amark (1986) provides some examples.
Although in the real world sand bodies can get into tills in more ways (that we know if) deciding between these two makes for good practice.
Methods:
To decide which type of sand body one has at hand one must carefully study the sand body and its surrounding material. We pick some exposures along a stream bed in Caldwell Park (Fig. 1). The specific site in the park may vary according to where the sand bodies crop out.
Working Definitions:
Sand body - any sand rich body with surrounded by a diamicton matrix.
Sand interclast - a sand body that was emplaced into the till as the result of deformation.
Sand lens - a sand body emplaced into the till as a small stream flowed.
Problem:
Ralph Smith of Smith Co. Inc. wants to donate enough money for Caldwell Park to build a small lake on one of the terraces. However he has heard about the presence of sand bodies and hopes the lake won't drain. He contracted your consulting company to check it out and of course the boss sent you out ASAP and you did not have the chance to read up on these sands.
What can you tell him about the sand bodies present (at least in one unit) at Caldwell Park? How far back from the study section should the pond be built?
Follow our Format and make a 3-4 page report for Mr. Smith. Make some specific reccomedianions what should be done so he can determine how much money he will have to donate.
Be sure you follow special instructions
