Port Deposit Gneiss
| Port Deposit Gneiss | |
|---|---|
| Stratigraphic range: Paleozoic | |
 Polished slab of the Port Deposit Gneiss, about 10.7 cm wide | |
| Type | metamorphic |
| Lithology | |
| Primary | gneiss |
| Location | |
| Region | Piedmont of Maryland |
| Extent | eastern Maryland |
| Type section | |
| Named for | Port Deposit, Maryland |
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.
Quarrying[edit]
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]
- Many houses and five churches in Port Deposit
- Schools like the U.S. Naval Academy, Haverford College and The Catholic University of America
- Fort McHenry, Fort Delaware and Fort Carroll
- Public buildings like the Boston Public Library and the U.S. Treasury Building
- Public works like the Concord Point Lighthouse, Lincoln Tunnel and the St Augustine seawall
-
McClanahan "Granite" Quarry c. 1898 -
McClenahan Quarry c. 1910 -
A present-day quarry across the Susquehanna River from Port Deposit in Havre de Grace, Maryland owned by Vulcan Materials Company, in January 2020
References[edit]
- ^ Geologic map of Harford County, Owens, James P., and Southwick, David L., 1968. Scale: 1:62,500. County Geologic Map CGM-1.
- ^ A History of Maryland’s Lower Susquehanna Region Archived 2006-10-01 at the Wayback Machine