麻豆传媒

Four sand and gravel pits east of Upper Nine Mile River expose parts of a 25 km long ridge of unconsolidated glaciofluvial sediment. Twenty five (25) stratigraphic sections were measured along fresh exposures in the westernmost pit, owned by Ed Spencer, which is believed to be representative of the entire deposit. Additional observations, comparisons and section measurements were three other pits (Babcock, Davis, Nova Scotia Sand and Gravel).

Six sediment types were defined in the field on the basis of clast size and sorting, overall texture, and observed sedimentary structures. These types are: 1); 2) ; 3) ; 4) ; 5) and 6) .

1. silt and clay
2. fine sand
3. coarse sand
4. gravelly sand
5. sandy gravel
6. coarse gravel

Grain size analyses later confirmed the distinctions.

The central core of the Spencer pit is composed of thick, alternating strata of coarse gravels to coarse sands, with thin interbeds of fine sand and silt. The core gravels grade westward to sands and gravelly sands, and all beds thin and fine towards the flanks. This westward and outward gradation likely represent the proximal to distal relationship of an esker bead that was deposited from the mouth of a sub-glacial tunnel.

The Spencer pit is representative of the entire deposit except in two details:

1. Overall, the deposits within the other pits are wider and more continuous.
2. The Babcock pit has more laterally continuous beds in cross-section, and has steeper sided flanks that contain more faults.

These differences imply minor differences in the mode of deposition.

The westward paleocurrent directions obtained from the orientation of three-dimensional cross-beds and cross-laminae in the Spencer pit and Nova Scotia Sand and Gravel pit indicate that the sediments were transported towards the west. These measurements and the similarity in composition of the granitic pebbles in the deposits with the Cobequid Highland granites indicate that the depositing ice flow originated to the east or northeast.

Keywords:
Pages: 68
Supervisors: G. Clint Milligan / Martin Gibling

听

听