Petrology of the Baltimore gneiss in the northeast Towson dome, Maryland Piedmont

Olsen, Sakiko N.

doi:10.1130/0-8137-2330-2.113

Cited by 2 publications

(10 citation statements)

References 23 publications

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“…Many augen have been crushed and sheared into streaks, especially in rocks near the contact with the overlying Setters Formation. These augen were probably single crystals of K-feldspar, later granulated and mechanically mixed with some of the matrix to form the surrounding mortar (see Olsen, 1999). The average bulk composition of the Hartley (Table 1, column 9) is close to that of average granite-granodiorite (e.g., Nockolds, 1954).…”

Section: Petrology Of the Baltimore Gneiss And Gunpowder Granitementioning

confidence: 95%

“…16 in Hopson, 1964). The bulk composition of these migmatites estimated from observed proportions of leucosome to melanosome (column 4-Net) is similar to that of average graywacke (e.g., Pettijohn, 1957, p. 307), suggesting that the protolith was sedimentary, and that the leucosome-melanosome pairs in these rocks may have originated as alternating layers of sand and shale, now modifi ed by metamorphic differentiation (Olsen, 1999).…”

Section: Origin Of Baltimore Gneiss Migmatites and Gunpowder Granitementioning

confidence: 96%

“…Within each sheet, the Gunpowder is a homogeneous, fi ne to medium grained, muscovite-bearing gneissic granite containing scattered biotite schlieren and rare megacrysts of plagioclase and/or microcline. The granite is remarkably uniform (Olsen, 1999), with a composition close to average calc-alkaline granite (Table 1, column 10; compare, e.g., Nockolds, 1954).…”

Section: Petrology Of the Baltimore Gneiss And Gunpowder Granitementioning

confidence: 97%

“…1B and 2). The following description depends heavily upon those sections, supplemented by scattered outcrops in other domes, a trench dug in 1967 for a pipe line along the Gunpowder Falls (Olsen, 1999), and a 500-foot drill core from the Baltimore Gas and Electric Company's plant at the southeast end of the Gunpowder traverse (Eugster, 1960).…”

Section: Petrology Of the Baltimore Gneiss And Gunpowder Granitementioning

confidence: 99%

“…Hopson's (1964) magisterial review of Piedmont geology supported and extended Eskola's interpretation. More recent work, however, has revealed new structural complexities in the structure of the Baltimore region, which suggest that the apparent domes are better understood as refolded fold-and-thrust nappes (Bromery, 1968;Fisher, 1989;Gates et al, 1999), and has cast doubt on the extent of partial melting, especially during the Paleozoic (Olsen, 1977(Olsen, , 1999.…”

Section: Introductionmentioning

confidence: 96%

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The Baltimore Gneiss domes of the Maryland Piedmont

Fisher

Olsen²

2004

Gneiss Domes in Orogeny

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Gneiss domes in the Maryland Piedmont near Baltimore contain a wide variety of metamorphic rock types, all metamorphosed to amphibolite grade and collectively named Baltimore Gneiss. Most were derived from interlayered sedimentary and volcanic rocks into which granitic plutons were emplaced in both Precambrian and Paleozoic time. Migmatitic features are common in the Baltimore Gneiss. Most seem to refl ect either original sedimentary layering or original layering that has been enhanced by later metamorphic differentiation, but some involved partial melting, perhaps during the Precambrian metamorphism. We fi nd no evidence for widespread melting in rocks at the present level of exposure during the Paleozoic. Limited fl uid-driven K-metasomatism may well have occurred locally, but we fi nd no evidence for metasomatism on a regional scale. Pressure-temperature conditions for the Baltimore Gneiss during the Paleozoic metamorphism are estimated to be 7-9 kb and 625-675 °C.For half a century, the anticlinal structures exposing basement gneiss at Baltimore have been cited as classic examples of mantled gneiss domes, but more recent fi eld studies and geophysical investigations suggest that they are the result of interference between late upright folds and early nappe structures formed by a combination of isoclinal folding along subhorizontal axial surfaces and thrust faults rooted in a regional décollement.

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Section: Petrology Of the Baltimore Gneiss And Gunpowder Granitementioning

confidence: 95%

Section: Origin Of Baltimore Gneiss Migmatites and Gunpowder Granitementioning

confidence: 96%

Section: Petrology Of the Baltimore Gneiss And Gunpowder Granitementioning

confidence: 97%

Section: Petrology Of the Baltimore Gneiss And Gunpowder Granitementioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

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The Baltimore Gneiss domes of the Maryland Piedmont

Fisher

Olsen²

2004

Gneiss Domes in Orogeny

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Cockeysville marble: a heritage stone from Maryland, USA

Hannibal

Schnabel²

2020

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By virtue of its use in iconic monuments and historic buildings in the USA, Cockeysville marble, a dolomitic to calcitic lower Paleozoic (Cambrian/Ordovician) marble quarried in Baltimore County and adjacent areas in Maryland, is proposed as a potential Global Heritage Stone Resource. The most important use of this stone was for the Washington Monument in Washington, DC whose construction began in 1848; the second most important use was for the 108 columns of the United States Capitol's wings, completed in 1868. It was also used for two of the oldest major marble monuments in the USA, Baltimore's Battle Monument (dedicated in 1827) and Washington Monument (completed in 1829), as well as Baltimore's City Hall, Buffalo's Adkins Art Museum, Detroit's Fisher Building and parts of St Patrick's Cathedral in New York City. During the nineteenth century white Cockeysville was most desired, but a colourful variety, Mar Villa marble, was also used in the first decades of the twentieth century. Cockeysville marble is no longer quarried for dimension stone. All Cockeysville used outdoors has weathered to a lesser or great extent, but early testing indicating that the dolomitic marble would be more durable has proved to be true.

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Petrology of the Baltimore gneiss in the northeast Towson dome, Maryland Piedmont

Cited by 2 publications

References 23 publications

The Baltimore Gneiss domes of the Maryland Piedmont

The Baltimore Gneiss domes of the Maryland Piedmont

Cockeysville marble: a heritage stone from Maryland, USA

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