The Port Deposit Gneiss is a Paleozoic gneiss formation in Cecil County, Maryland. It is described as a "Moderately to strongly deformed intrusive complex, chiefly composed of quartz diorite gneiss. Rock types include gneissic biotite-quartz diorite, hornblende-biotite-quartz diorite, and biotite granodiorite, with minor amounts of quartz monzonite and hornblende-quartz diorite. Moderate protoclastic foliation grades into strong cataclastic shearing."[1] It intrudes into the Volcanic Complex of Cecil County.

Port Deposit Gneiss
Stratigraphic range: Paleozoic
Polished slab of the Port Deposit Gneiss, about 10.7 cm wide
Typemetamorphic
Lithology
Primarygneiss
Location
RegionPiedmont of Maryland
Extenteastern Maryland
Type section
Named forPort Deposit, Maryland
Photomicrograph of Port Deposit Gneiss, approximately 0.85 cm across, under crossed polarized light.

Quarrying

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The Port Deposit Gneiss has been quarried along the east as well as the west bank of the Susquehanna River for over 100 years.

Port Deposit Gneiss was used in:[2]

References

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  1. ^ Geologic map of Harford County, Owens, James P., and Southwick, David L., 1968. Scale: 1:62,500. County Geologic Map CGM-1.
  2. ^ A History of Maryland’s Lower Susquehanna Region Archived 2006-10-01 at the Wayback Machine