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Chadwick Wildlife Preserve

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This is a contributing entry for Chadwick Wildlife Preserve and only appears as part of that tour.Learn More.

Continue on Long Point Trail past the intersection with The Minquas Path. Further along the creek bed you will see two large expanses of cobblestones leading into Ridley Creek. These are the Meander Point Bars. Long Point is the sharpest meander of Ridley Creek, formed where the flow was diverted millennia ago by the highly resistant rock of the hill across the stream. A point bar is a depositional feature made of sand, gravel, and cobblestones that accumulates on the inside bends of streams and rivers in a crescent shape. 


Southeast bend Meander Point Bars on Ridley Creek

Southeast bend Meander Point Bars on Ridley Creek

Northeast bend Meander Point Bars on Ridley Creek

Northeast bend Meander Point Bars on Ridley Creek

The material deposited on the meander points is well-sorted by flood currents, causing the cobbles, gravel, and sand to form bands or zones. Point bars have a very gentle slope and an elevation close to water level. Since they are low-lying, they are often covered by floodwaters and can accumulate driftwood and other debris during times of high water.

Due to their nearly flat topography, near-absence of vegetation, and the fact that the water speed is slow in the shallows of the point bar they are popular rest stops for boaters, rafters, and walkers. Because several kinds of bedrock are present just upstream from this point bar, there is a striking variety of cobblestone and gravel colors and textures mixed together here. You will also find quartz and serpentinite, and highly weathered artifacts such as bricks and bits of glass.

One of the most interesting aspects of Rose Valley's geology is the small serpentinite outcrop — about 2½ acres — near the top of the hill just across the creek from Long Point on Wychwood Lane. Serpentinite is a metamorphic rock derived from igneous oceanic crust and is quite rare on land. It's famous for weathering into a very unusual type of soil that often supports unique vegetation called serpentine barrens, which includes many rare or endangered species. When you wander the point bars at Long Point, which are directly downslope from Rose Valley's serpentinite outcrop, you can find a few cobbles of light-green serpentinite among the many cobbles of schist, gneiss, and quartz.

Latham, Dr. Roger. Meander Point Bars (Cobblestones). Notes for Chadwick Preserve. August 16th, 2023.