CALL Course Field Trip #1

CALL Course on Geology and Environmental Geology of the State College Area

Field Trip #1, June 27, 2006
Periglacial Features, Soils, and Karst

STOP 1A. Assemble at Jo Hayes vista atop Tussey Mtn. View the double ridges underlain by Tuscarora and Bald Eagle sandstones and the intervening valley formed in the Juniata Formation that contains both sandstones and shales. View the forested “stripe” of Park Forest-Scotia underlain by the Gatesburg Formation, Bald Eagle Mtn (the other side of the Nittany Valley anticlinorium), the syncline of Mount Nittany, and the Allegheny Plateau on the skyline to the west.

Either here or at stop 1B we will examine the Tuscarora sandstone. It is light in color because it contains no clay, very hard because it consists of quartz grains cemented by quartz, contains occasional larger-grained layers, and has cross-bedding. These characteristics indicate that the mountainous source of its grains was some distance away and not particularly high (i.e., after the Taconian Orogeny), and that the formation represents a beach or off-shore bar environment.

STOP1B. The Indian Steps periglacial boulder field. The eastern and central US was invaded by four periods of glaciation in the Quaternary period (last 2 my): Nebraskan at 1.8 my to 1.65 my, Kansan at 900,000 to 750,000 y, Illinoian at 400,000 to 250,000 y, and Wisconsin, a series of ice advances and retreats at 100,000 to 10,000 y. Pre-Wisconsin age ice advanced, from Canada, to about 40 km south of Williamsport, and Wisconsin stopped about 50 km north of Williamsport. In other words, ice did not invade the State College area. But during ice advances, it was cold here, particularly on ridge tops, and average temperatures were probably below freezing. Ice retreated about 15,000 y ago and covered a large part of northern Canada until 8,000 y.

In many places atop Tussey Mtn, the Tuscarora sandstone was shaped by ice, frost, and freeze-thaw cycles. Large fields of angular boulders are found, particularly on south-facing slopes, from the tops of the ridges to the valley floors. Observable features include “patterned ground” – stone stripes and polygonal grouping of rocks. The breakup of bedrock and movement in fields occur by gelifluction: water released in the surface during a thaw cannot penetrate the frozen layer below. So the water is concentrated at the near-surface and produces a gel that lacks cohesion and can flow readily. These periglacial fields are moving very little today, as witnessed by the straight trees growing within them.

STOP 2. Radio Park Elementary School. Behind Radio Park are large blocks, which may or may not be outcrop, of Stonehenge limestone. Darker-colored bedding layers are considerably disrupted, probably by burrowing marine worms. A variety of fossil fragments can be seen.

Just to the south is Big Hollow, which extends to the west and to the east. It runs through the Armory on Fox Hollow Road, an area that contains Penn State’s well field. Big Hollow is a zone of concentrated fractures along which considerable volumes of groundwater flow. Note that there is no stream, ever, in this topographic low. All water movement is underground. But pollutants that might reach this feature, such as from the old State College municipal dump to the north, would travel quickly also, and groundwater is not easy to clean up. Small sinkholes develop within Big Hollow. The cartoon below is applicable to Big Hollow.
Another example of a pollutant is the discovery of a drycleaning-type contaminant in the soil at the Penn State Fire School site about 0.5 mile west of the Armory in Big Hollow. All contaminated soil was excavated and hauled to a secure landfill in Ohio. Fortunately, the contaminant had not worked its way down to the water table, so no groundwater cleanup was necessary.

STOP 3. K-Mart (now Lowe’s) parking lot and the subdivision behind the parking lot. The Park Forest area is underlain by the Gatesburg Formation that contains units of dolomite, sandy dolomite, clay-rich dolomite, and sandstone. On the bank behind the parking lot, we will examine the “modern” soil in the top 3 ft. This soil is quite acidic and thin. Just below the surface is the E horizon of pure quartz. This quartz layer in places piles up in the Park Forest-Scotia-Barrens area, looking like a sand pit. Quartz is the common mineral most resistant to weathering, so in this layer everything else has been weathered out. Because the soil is thin and acidic, early settlers were never able to farm it, and so it returned to forest.

Below the modern soil in the 50-ft bank, there is no bedrock outcrop. This material is an "ancient" soil, probably dating back 30 to 50 my, when worldwide climates were warmer than today. It contains lenses of white kaolinite clay (that are not very visible, now that Lowe’s has re-engineered the bank face) and nodules of iron oxide, both red (hematite, Fe₂O₃) and yellow-brown (goethite, FeO(OH)). Kaolinite only forms in hot, humid, tropical climates. The nodules also are products of weathering, a process that breaks down existing minerals, removes some elements in solution, and creates new minerals. New minerals include clay and iron oxides. We will visit a pile of these nodules to the west.

The same process operated in the Scotia Mine area in the gamelands to the west. There the soils are several hundred feet thick, probably because they developed down into sinkholes. Andrew Carnegie named these mines Scotia after his native Scotland. Millions of dollars worth of ore were taken out in the early 1900s for local iron operations. The mines shut down when higher quality and larger volume ore was developed in the Mesabi Range of northern Minnesota. Andrew Carnegie then directed his attention to Pittsburgh as a center of operations.

The area behind the parking lot sprouts new houses every day. We will visit a "location de jour" to see fragments of the sandstone bedrock.