<p> Cobequid Bay is a macrotidal embayment with a large intertidal sand bar complex at the east end, located at the head of the Bay of Fundy. Two sand bars were sampled in order to observe variations in impact pit densities on the surfaces of quartz sand grains, and to identify the pattern of grain size distribution over two intertidal bedforms. </p> <p> V pit densities obtained by viewing the quartz grain surfaces at magnifications of 10,000 and 5,000X with a scanning electron microscope indicate a linear correlation with grain size. The number of small V's appears to be consistent for all grain sizes, with the result that V's larger than approximately 1/5 micrometer produce the linear variation noted. Two trends of V pits formation combine to produce a "plateau", in which two grain size classes have similar V pit densities. This plateau corresponds to the break-point between the traction population and the intermittent suspension population. Trend one consists of the bombardment of large, well exposed grains (transported in the traction layer), by smaller saltating grains, while trend two consists of grain impacts between smaller grains in the concentrated "rheological layer". </p> <p> Two different grain size patterns were discovered on the two sampled bedforms. A fining upward trend toward the crest on both the stoss and slip faces was observed on an ebb dominated megaripple on Selmah Bar. The exact opposite pattern was noted on an ebb dominated sandwave from East Noel Bar. On this bedform, an upward coarsening trend toward the crest was discovered on both the stoss and slip faces. These two patterns correspond to the patterns observed by Dalrymple (1977) in his studies of intertidal bedforms. </p> / Thesis / Bachelor of Science (BSc)

<p> Triassic sandstones form rapidly eroding cliffs around much of the Minas Basin, Nova Scotia. The sand eroded from these cliffs is one major source of the modern intertidal sands. Wave erosion of the cliffs locally produces a small sand beach at the high tide level. </p> <p> Eight samples were examined using the Scanning Electron Microscope: two from the Triassic sandstones, and six from the high-tide beach below the cliffs. All samples contained rounded, as well as subrounded and subangular, quartz grains in the 0.5 - 1.00 mm size fraction. As the samples originated in the cliffs, abrasion by strong tidal currents cannot account for the rounded grain shape. </p> <p> All grains studied had suffered some degree of diagenesis in the form of a precipitation coat. This was generally thicker on the rounded grains than on the more angular ones. The Triassic sandstone grains generally illustrated upturned plates, semiparallel steps, conchoidal breaks and a fine V-shaped pattern. The high beach grains illustrated upturned plates, V-shaped patterns, conchoidal breaks, greater rounding of featu res present and arc-shaped steps. Wehrfritz (1973) studied quartz grains from intertidal sand bars in the Minas Basin. He concluded that grains were considerably rounded by intertidal processes, and the frequency of V-shapes increased with grain roundness. </p> <p> Although some rounding of the beach sands was inherited, wave and tidal action aided in rounding the features further. The initial rounding of the sand grains within the sandstones may have occurred during periods in the Triassic when they were exposed to wind or reworked in the lakes. </p> / Thesis / Bachelor of Arts (BA)