|Grant, D. R.
|This preliminary investigation of coastal non-stratified
glacial deposits was planned to study the regional pattern, and
provide basic information necessary for the interpretation of
Scotian Shelf sediments. It is a detaiied-reconnaissance survey
aimed at establishing the geographic distribution of till types
as characterized by their pebble associations. The scope ranges
from detailed pebble analysis to stratigraphy and chronology.
One hundred and sixty ground moraine samples were col lected along road traverses over a 6000 square-mile area. The
5.6mm - 22.2mm pebble fraction was dry sieved in the field and
wet screened in a rotary washing mill. Number frequency pebble
counts were made on 500-grain samples and the data are examined
variously as; unit percentages of all rock species, bedrock
components versus foreign elements, relative proportions of the
foreign species, and as relative source area influences.
Fifty rock species are traced to seven source regions,
for which special topographic and geographic features pertinent
to interpretation are set out. A bar diagram map of source
area lithology, and triangular diagrams reveal that three mono lithologic till types form the bulk of the ground moraine.
Each contains at least 80 per cent bedrock material, and has a
distribution matching the ,corresponding local source - granite
quartzite or slate. Minor hybrid or mixed tills occur near
source area contacts. Isopleth maps oft he foreign elements,
recalculated to 100 per cent, reveal a lobate dispersal
In the anomalous areas of foreign-pebble enrichment
occur red clay drumlin fields which were sampled subsequently.
Ternary compositional diagrams reveal a characteristic lith ology for each field. Lithology of individual drumlins can
be related to distance of travel over the underlying bedrock,
and away from the distant sandstone area. The anomalous fine grained red, 'drumlin' till matrix is interpreted as former
alluvial, lacustrine, and tidal flat deposits winnowed during
an interstadial from pre-existing red tills.
The lobate foreign-pebble distribution is interpreted
as the result of currents created in the thin ice sheet margin,
either by topographic channeling or confluence of local ice
caps. A tentative sequence of glacial events is based on
stratigraphic correlation of sections and radiocarbon dates.
Linear outcrops of cemented outwash are assigned to a pre Sangamon terminal moraine. 'Early' Wisconsin tills are pres ent, followed by pre-classical Wisconsin regoliths underlying
the compact sub-drumlin Tazewell till. The drumlin advance
dates from the 'Port Stanley' episode, and the drumlins were
overridden during the 'Port Huron' glaciation.
A parallel study of beach sand heavy minerals reveals
an identical dispersal pattern of indica~or augiteo The mis leading occurrence of 'transported' _geoch~mical anomalies in
drumlin fields is emphasized. Applications to oceanographic
sampling and sedimentary petrographic interpretation are
|Glacial landforms -- Nova Scotia
|Pebble lithology of the tills of southeast Nova Scotia
|Department of Geology
|Master of Science