File:The Canadian field-naturalist (1931) (20334048619).jpg

Title: The Canadian field-naturalist
Identifier: canadianfieldnat451931otta (find matches)
Year: 1931 (1930s)
Authors: Ottawa Field-Naturalists' Club
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Publisher: Ottawa, Ottawa Field-Naturalists' Club
Contributing Library: Harvard University, Museum of Comparative Zoology, Ernst Mayr Library
Digitizing Sponsor: Harvard University, Museum of Comparative Zoology, Ernst Mayr Library

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26 The Canadian Field-Naturalist
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(Vol. XLV Figure 1.—Quarry in "Transition Beds," on the farm of Mr. H. J. Hands, Lot 10, Concession II, Drummond Township, Lanark County, Ontario, where remarkably well preserved ripple marks may be seen. certainly exceptional and local. The Potsdam sandstone is succeeded by the sandy dolomitic limestone or limey dolomite of the Beekmantown, the change from the Potsdam to the Beekman- town taking place in most places transitionally, beds of sandstone up to four feet thick alternating with beds of sandy dolomitic limestone. These alternating beds formerly known as "Transition Beds", but now called Theresa in New York state, are usually thin, the maximum thickness so far observed by the writer being 30 to 40 feet in the vicinity of Smiths Falls. The sandstone of the Potsdam and the Tran- sition Beds is ripple marked in many places, the ripples being for the most part of the unsym- metrical type. The greater part of the ripples trend northeast-southwest or east-west and the steeper side of the crests of the ripples are on their south- east or south sides indicating that the current by which they were formed came from the north- west or north. During the past season the writer encountered some exceptionally perfect ripple marks in sand- stone of the Transition beds in a quarry excavated for road material on the farm of Mr. H. J. Hands, Lot 10, Concession II, Drummond Township, Lanark County, Ontario. The quarry lies about 3 m^les northeast of Perth and 300 yards north of the second line of Drummond which forms a part of the original stage road from Perth to Ottawa, and the most probable route of the proposed Ottawa-Sarnia highway. The mode of occurrence of the ripples in thin beds on the quarry floor is shown in Figure 1. They occur nearly everywhere throughout the entire extent of the quarry which is over 200 feet long by 100 feet wide and throughout a vertical range of about 14 inches. The total thickness of strata exposed in the quarry face is about 5 feet. This consists of thin bedded sandy dolomitic limestone, in which beds or zones and lenses of white sandstone up to 1 inch thick are inter- calated sparingly near the top but more abun- dantly near the bottom.- Closer views of the ripple marks are shown in Figures 2 and 3. Al- though these ripple marks were formed during the early Palaeozoic and hence are almost certainly several hundred million years old they are as perfect as the day they were made. In Figure 3 it can be seen that sun cracks have been super- imposed on the ripple marks. This shows that the ripple-marked beds were dried by the sun before the succeeding bed was laid down and hence were deposited on an intertidal flat.

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