Part 1-Columbia to Chicks Rock
One of my ongoing projects is the development of a geological guide for recreational trails in Northwest Lancaster County. The trail runs north from Columbia to Falmouth, about 14 miles, along the floodplain of the Susquehanna River.
The trail starts at the spectacular Columbia Crossing River Trails Center, next to Walnut Street, south of the Veterans Memorial Bridge (Pa. Rte. 462). The center has great displays, focusing on the history of the Lower Susquehanna Valley. Colombia is located in the lowlands of Piedmont or locally known as the Conestoga Valley.
Understanding our landscape in this part of the United States is fairly simple. Soft rocks such as limestone and shale are located below the valley, while harder rocks such as quartzite (metamorphic sandstone), igneous rocks, and conglomerates make up higher elevations. Limestone dominates the Conestoga Valley, and because it is prone to weathering and erosion, exposure of limestone is rarely seen in Colombia.
More: This York County geologist has five fossils named after him
Continue north along the Northwest Lancaster County Trail, under the Wright Ferry Bridge that connects York County and Lancaster County with U.S. Route 30. The concrete bridge opened on November 21, 1972, at a cost of 12 million U.S. dollars. Note that just to the north of the bridge, the trail enters a new part of the landform called the Piedmont highland part. Notice that the valley is now behind you, and the ridge starts to appear to your right. Most of the rocks in the high section are composed of metamorphic rocks, such as quartzite and phyllite. Quartzite was originally sandstone, and phyllite was once shale. The age of these rocks is from Late Proterozoic to Early Paleozoic (541-530 million years).
To the north of the Wrights-Ferry Bridge is the remains of St. Charles Furnace on the east side of the trail. Pay attention to the black soil around the furnace. The furnace is the southernmost point of this type of operation in the Chickies Rock area and was built in 1854 by Clement Brooke Grubb, the blacksmith of a famous iron ore mining and manufacturing family. Grubb brought Henry Clay Furnace (station 6) in 1875 and renamed it St. Charles 2. The annual pig iron output of these two furnaces exceeds 20,000 tons, which is used for the manufacture of boiler plates, bars, nails and casting work. St. Charles 1 was remodeled between 1879 and 1880, but only operated for six years. The furnace was dismantled in 1897.
The foundation of the foundry room, part of the engine and the stone piles of the furnace still stand in the surrounding brushes. You can see the brick arch opening of the tuyere and the circular channel that partially extends around the bottom of the chimney to guide the hot air to the furnace. The heat of the stove is first supplied by charcoal, and then coal is used after the renovation. Black soil comes from slag, charcoal, coal and iron ore fragments.
Not far north of St. Charles Furnace is the Point of Rock Railway Tunnel. We saw these metamorphic rocks for the first time in the tunnel. The Harrisburg, Joey Mountain, Portsmouth, and Lancaster lines of the Pennsylvania Railway passed through this tunnel in 1850. The tunnel is 180 feet long and cuts through solid rock. The rocks exposed here belong to the Harpers group. The rock here is phyllite, which shows foliation and silky luster due to small pieces of mica. Foliation is a metamorphic feature in which minerals are flattened and arranged parallel to each other. The pressure and compaction during continental collisions will produce fronds.
In this case, the rock changed during the Africa-North America collision during the Alcanian orogeny 325-260 million years ago. Quartz veins pass through phyllite, which was formed as a result of the subsequent crustal fracture movement and subsequent filling of silica. Also note the many chisel marks perpendicular to the foliation. These came from the construction of the tunnel. Workers were holding a star-shaped pointed chisel, and another worker hammered the chisel with a 10-pound sledgehammer. Then rotate the chisel 90° and strike again. After repeating this action many times, a hole will be deep enough to place black powder and blast the rock apart.
Continue north on the trail, and on the west side of the trail north of the BreezyView trail intersection that intersects with the trail is a huge rectangular Chickies quartzite block. This is a great opportunity to touch and feel this rock, because Chickies County Park does not allow access to the outcrops outside the trail. Quartzite is a metamorphic rock formed from sedimentary rocks called sandstones. Sandstone is exposed to heat and/or pressure to fuse the quartz particles in the rock to form larger particles and increase the density of the rock. The rectangular shape of the block comes from the joints, which is the process by which the rock cracks in patterns due to the pressure in the earth's crust. Please note that due to the low iron content in the rock, quartzite will weather brown.
As you go north, note that the hillside on the right is sometimes close to the trail, while in other locations, the hillside is further away from the trail. This is due to the alternating areas of the Harpers and Chickies formations. Chickies Quartzite is harder and forms the hillside closest to the trail. Harpers phyllite is softer and is located in the ridge of the trail depression.
The next feature to emphasize is the remains of Henry's clay furnace. The Henry Clay furnace was one of the earliest anthracite furnaces along the Susquehanna River between Columbia and Marietta. Built in 1845 by Peter Haldeman, a celebrity in the local ironmaking industry. After 1855, the furnace changed hands several times and production was intermittent until Danny and Hess took over operations in 1865. The former tavern dates back at least to 1819, became a blacksmith's house when the furnace was opened, and is now the residence of John Q. Denney. In 1875, Clement Brooke Grubb purchased the furnace. Mr. Grubb refurbished the furnace again in 1879-1880 and 1887. The furnace ceased operation in 1889.
The location of the furnace allows easy access to the Pennsylvania Canal, which imports anthracite from northwestern Pennsylvania. A road goes up through Jones Valley from here to the iron deposits on Chestnut Hill, about six miles east. Jones Run is blocked by rock fragments and is no longer visible, supplying water to the furnace. The limestone used as a flux in the furnace was mined north of Chickies Ridge. When the Harrisburg, Portsmouth, Joey Hill, and Lancaster lines of the Pennsylvania Railroad were installed in the 1850s, the furnace became a link to a larger transportation network.
The north wall of the six rooms still stands on the east side of the path. Stone walls made of Chickies quartzite are unstable. The building was used by workers in the furnace during its operation and became a residence for railroad workers, northern stone crusher employees, and low-income tenants until the fire made the building uninhabitable in the early 1920s.
The display area of the leisure trail is Chickies Rock. In fact, it is one of the exhibits of geology in southeastern Pennsylvania. Several universities came here from out of state to study Chickies Rock, and many geologists studied this outcrop dating back to the early 1800s.
So what makes this 100-foot-high summit stand out? First of all, it is a type site for the chick group. The description of the rock types and how they are related is established from here. Second, look at the overall outline of the rock. Have you noticed that the cliff looks like an arch? The rock was folded into what geologists call an anticline. Chickies Rock is a classic exposure of anticlines. When you drive about half of the cliff north, you will see a small overhang or rock shelter at the bottom. This is the center of the anticline. If you enter the rock shelter and look towards the roof on the north side, you will see several Skolithos linerais pipes. These fossils are always found perpendicular to the bed. Geologists believe that these pipes are sea worm caves, and the age of the rocks is about 541 million years. Part 2 of the path description will detail the naming of these fossils.
If you look at the rock (preferably from the south end), try to follow the bedding of the quartzite. Many of the cracks you see on the cliff are faults, and the angle of the bedding may change with the cracks. So not only did Chickies Rock fold into an anticline, but the rock was also faulted.
At the northern end of Chickies Rock, there are traces of ripples. In very shallow sea water, ripples are formed along with the current. Today, when you visit the beach, your feet will change as the water temperature changes, so you can see traces of ripples. Based on the evidence provided, you can outline what Chickies Rock looks like in your mind. 541 mya quartzite is composed of sand. The presence and ripple traces of Skolithos linerais indicate that it is a beach shallow sea environment, all of which are folded and later occurred in Africa -Faults during the North American collision. As the weather starts to point towards spring, enjoy this column and explore, this is a good time to go out and touch the rocks.
Jeri Jones regularly writes articles about local geology.