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Within the Piedmont Uplands Section of southeastern Pennsylvania lies a metamorphic terrane containing the Peach Bottom Slate. The Peach Bottom Formation has been the center of attention for both quarrymen and geologists for more than 200 years. This probably early Paleozoic unit, underlying “Slate Ridge,” has been mined in Lancaster and York Counties, Pennsylvania, and Harford County, Maryland. The Peach Bottom Slate was judged the best building slate in the world at the 1850 World Exposition in London. Although mining terminated in the 1940s, the effect of the slate on the community and its heritage is well preserved today. The main purpose of the field trip is to examine some of main landmarks of the slate’s cultural effects, including a visit to a Welsh cemetery and a view of the district’s largest quarry. We also will seek an understanding of how the slate industry’s history has been preserved.

Some problems of the regional geology also will be addressed. At our first two stops in Chester and Lancaster Counties, we will examine serpentinite within the Baltimore Mafic Complex. Our next stop in Lancaster County is a key exposure showing the relationship between the Peach Bottom Formation and its neighboring rock units. Despite much research on the structural implications of these rocks, the interpretation is still “up in the air.” Your opinions will be very much welcomed.

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