A detailed gravity study of the Chattolanee Baltimore Gneiss Dome, Maryland, U.S.A.

Kodama, Kenneth P.; Chapin, David A.

doi:10.1016/0012-821x(84)90160-2

Cited by 3 publications

(2 citation statements)

References 9 publications

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“…Coupled with the gravity data, that observation strongly suggested that the gneisses of the Phoenix dome were not rooted, as required by Eskola's model, but were simply the exposed part of a thin sheet of basement rock infolded with the cover sequence, either a fold nappe or a thrust sheet. Kodama and Chapin (1984) conducted a more detailed gravity survey along three roughly N-S traverses across the Chattolanee dome. Like Bromery, they found an elongate gravity low clearly associated with the dome, but two-dimensional modeling and geological information suggested to them that this dome is also unrooted, most likely an arched recumbent fold cut off from its root zone, probably by thrusting.…”

Section: Reinterpretation Of the Baltimore Gneiss Domesmentioning

confidence: 99%

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: Reinterpretation Of the Baltimore Gneiss Domesmentioning

confidence: 99%

The Baltimore Gneiss domes of the Maryland Piedmont

Fisher

Olsen²

2004

Gneiss Domes in Orogeny

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“…The northeastern portions of the anticlinorium, which include the Phoenix, Texas, Towson, and Chattolanee domes (Figure 2), belong to a westward directed Taconic nappe system that rooted under the Towson dome, and were later refolded during the late Acadian or Alleghanian orogenies [ Kodama and Chapin , 1984; Muller and Chapin , 1984; Gates et al , 1999]. The Woodstock, Mayfield, and Clarksville domes in the southwestern portion of the anticlinorum experienced a similar deformation history in terms of the matrix foliations, but are regarded as belonging to another nappe system with an unknown root [ Kodama and Chapin , 1984]. Muller and Chapin [1984] suggested that at least four stages or phases of ductile deformation have affected the Pennsylvania nappe system.…”

Section: Geological Settingmentioning

confidence: 99%

Significance of dextral reactivation of an E‐W transfer fault in the formation of the Pennsylvania orocline, central Appalachians

Yeh¹,

Bell

2004

Tectonics

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Three hypotheses for orocline development including (1) primary plate boundary shape, (2) arc rotation, and (3) arc overprinting were evaluated for the formation of the Pennsylvania orocline, Maryland, USA, using foliation intersection/inflection axes preserved within porphyroblasts (FIA). The distribution and the timing of sequences of FIA data measured from garnet porphyroblasts within the Loch Raven formation are statistically the same across the Pennsylvania orocline, suggesting that all subregions of the arc have experienced the same deformation history. This may suggest that the geometry of the paleocontinental margin controlled the basic shape of this orocline. However, if the orocline is treated as three separate regions, defined by the SW‐WE‐NE trending portions of its slightly staircase‐shaped outline, a much higher proportion of the NNE‐SSW trending FIAs (set II) are preserved in the W‐E trending region than those to either side. This geometric relationship could have resulted from WNW‐ESE directed bulk stress causing a zone of dextral shear along what is now the W‐E trending portion of this orogen. It appears that what could have been an early formed W‐E trending sinistral transform shear zone was preferentially dextrally reactivated during the Taconian orogeny.

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