Abrasion, transport and distribution of sediment in selected streams of Southern Ontario and Western New York /

The rate of decrease in mean sediment size and weight per square metre along a 54 km reach of the Credit River was found to depend on variations in the channel geometry. The distribution of a specific sediment size consist of: (1) a transport zone; (2) an accumulation zone; and (3) a depletion zone. These zones shift downstream in response to downcurrent decreases in stream competence. Along a .285 km man-made pond, within the Credit River study area, the sediment is also characterized by downstream shifting accumulation zones for each finer clast size. The discharge required to initiate movement of 8 cm and 6 cm blocks in Cazenovia Creek is closely approximated by Baker and Ritter's equation. Incipient motion of blocks in Twenty Mile Creek is best predicted by Yalin's relation which is more efficient in deeper flows. The transport distance of blocks in both streams depends on channel roughness and geometry. Natural abrasion and distribution of clasts may depend on the size of the surrounding sediment and variations in flow competence. The cumulative percent weight loss with distance of laboratory abraded dolostone is defined by a power function. The decrease in weight of dolostone follows a negative exponential. In the abrasion mill, chipping causes the high initial weight loss of dolostone; crushing and grinding produce most of the subsequent weight loss. Clast size was found to have little effect on the abrasion of dolostone within the diameter range considered. Increasing the speed of the mill increased the initial amount of weight loss but decreased the rate of abrasion. The abrasion mill was found to produce more weight loss than stream action. The maximum percent weight loss determined from laboratory and field abrasion data is approximately 40 percent of the weight loss observed along the Credit River. Selective sorting of sediment explains the remaining percentage, not accounted for by abrasion.

Sedimentology of the Sixteen Mile Creek Lagoon, Niagara Peninsula, Ontario, Canada

The effec s of relative water level changes in Lake Ontario were detected in the ysical, chemical and biological characteristics of the sediments of the Fifteen, Sixteen and Twenty Mile Creek lagoonal complexes. Regional environmental changes have occurred resulting in the following sequence of sediments in the three lagoons and marsh. From the base up they are; (I) Till,(2) Pink Clay, (3) Bottom Sand, (4) Gyttja, (5) Orange Sandy Silt, (6) Brown Clay and (7) Gray Clay. The till was only encountered in the marsh and channel; however, it is presumed to occur throughout the entire area. The presence of diatoms and sponge spicules, the vertical and ongitudinal uniformity of the sediment and the stratigr ic position of the Pink Clay indicate that it has a glacial or post-glacial lacustrine origin. Overl ng the Pink Clay or Till is a clayey, silty sand to gravel. The downstream fining and unsorted nature of this material indicate that it has a fluvial/deltaic origin. Water levels began rising in the lagoon 3,250 years ago resulting in the deposition of the Gyttja, a brown, organic-rich silty clay probably deposited in a shallow, stagnant environment as shown by the presence of pyrite in the organic material and relatively high proportions of benthic diatoms and grass pollen. Increase in the rate of deposition of the Gyttja on Twenty Mile Creek and a decrease in the same unit on Sixteen Mile Creek is possibly the result of a capture of the Sixteen Mile Creek by the Twenty Mile Creek. The rise in lake level responsible for the onset and transgression of this III unit may have been produced by isostatic rebound; however, the deposition also corresponds closely to a drop in the level of Lake Huron and increased flow through the lower lakes. The o ange Sandy Silt, present only in the marsh, appears to be a buried soil horizon as shown by oxidized roots, and may be the upland equivalant to the Gyttja. Additional deepening resulted in the deposition of Brown Clay, a unit which only occurs at the lakeward end of the three lagoons. The decrease in grass pollen and the relatively high proportion of pelagic diatoms are evidence for this. The deepening may be the result of isostatic rebound; however, the onset of its deposition at 1640 years B.P. is synchronous in the three lagoons and corresponds to the end of the subAtlantic climatic episode. The effects of the climatic change in southern Ontario is uncertain. Average deposition rates of the Brown Clay are similar to those in the upper Gyttja on Sixteen Mile Creek; however, Twenty Mile Creek shows lower rates of the Brown Clay than those in the upper Gyttja. The Gray Clay covers the present bottom of the three lagoons and also occurs in the marsh It is inter1aminated wi sand in the channels. Increases in the rates of deposi ion, high concentrations of Ca and Zn, an Ambrosia rise, and an increase in bioturbation possibly due to the activities of the carp, indicate th this unit is a recent deposit resulting from the activities of man.