Rydal-Meadowbrook Civic Association

Mineral Deposits in Abington

Rydal-Meadowbrook, Cheltenham and a portion of Lower Moreland are part of the Pennypack watershed. Silty clay disintegration residuum and gypsiferous solution residuum predominate in this area that had been known to have problems with flooding. Silt often occurs as suspended sediment in a surface water body, or deposited at the bottom. Silty clay has 40% or more clay and 40% or more silt.

Gypsiferous soil contains more than 2% gypsum, which is a very soft mineral composed of calcium sulfate dihydrate. Gypsum increases electrolyte concentration of water at the surface of the surface and reduces the infiltration of water.

Edge Hill divides Abington Township. On the western side, the Sandy Run creek flows into the Wissahickon Creek to the west. Not surprisingly, the soil has both sand and clay. Much of these deposits sit on granite, but contain saprolite. This is a layer of clay and disintegrating rock. Rotting rock is typically created by chemical weathering in warm and humid climates.

To the western end of Abington and continuing into Springfield Township, the soil becomes more cherty. This is a variety of silica that contains microcrystalline quartz. Chert is a siliceous rock of chalcedonic or opaline silica occurring in limestone. Oreland contained three limekilns as recently as the early 20th Century.

The majority of the county does not match this profile. Although it has argillite, a fine-grained sedimentary rock composed predominantly of indurated clay particles, Montgomery County has a significant amount of shale. Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments (silt-sized particles) of other minerals, especially quartz and calcite. It also contains Arkose, a detrital sedimentary rock, specifically a type of sandstone containing at least 25% feldspar.

Sources and Links:
USGS National Atlas
USGS Mineral Resources
Audubon Musuem
Pennsylvania Geological Survey