Bellevue State Park (BVD)
Bellevue State Park (BVD)
Latitude: N39.77472
Longitude: W75.49944
Elevation: 58 meters
Geology
The seismometer located at Bellevue State Park is placed on the Brandywine Blue Gneiss. The Brandywine Blue Gneiss is the new name given to the granulite-facies felsic gneisses in the Wilmington Complex. Informally called the “blue rocks,” this unit is a medium- to coarse-grained, lineated (pinstriped), two-pyroxene gneiss with variable quartz content and thin, discontinuous mafic layers, pods, and schlieren. The pinstriping and the massive nature of the rock suggest the rock is intrusive; however, deformation and recrystallization have obscured original igneous features.
The unit appears on the Wilmington North, Wilmington South, and Marcus Hook quadrangles where it underlies the city of Wilmington and its northeastern suburbs.
The bright blue to blue-gray color of the gneiss when freshly quarried led 19th century stone cutters and local geologists to call this rock the Brandywine blue granite, the “blue rock of the Delaware Quarries” or the “blue granite of the Delaware quarries”. To retain the local usage and priority of previous names, we have named this lithodeme the Brandywine Blue Gneiss.
Equipment
Seismometer:Mark Products L-4C Short period Vertical
Amplifier: Sprengnether AS-110 Gain 68dB
VCO: TC-10 1700 Hz