The Quebec-western Maine seismic reflection profile: Setting and first year results

Stewart, David B.; Unger, J.D.; Phillips, Jeffrey D.; Goldsmith, Richard; Poole, W H; Spencer, Carl; Green, A. G.; Loiselle, Marie-Claude; St‐Julien, Pierre

doi:10.1029/gd014p0189

Cited by 42 publications

(14 citation statements)

References 5 publications

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“…Brunswick is also ~15 km east of the eastern margin of the Sebago batholith (293 ± 2 Ma, U-Pb monazite; Tomascak et al, 1996a), which is in the Central Maine belt. The Hackmatack Pond boundary separates the Central Maine belt and Falmouth-Brunswick sequence and appears as a west-dipping reflector on regional seismic profiles (Stewart et al, 1986). This boundary has been described as either a thrust fault (Pankiwskyj, 1976) or a stratigraphic unconformity (Osberg, 1988).…”

Section: Geologic Contextmentioning

confidence: 99%

“…For example, the data permit the leucogranites to be products of a mixture of juvenile Avalon-like crust and Central Maine belt metasedimentary rocks, characterized by ε Nd [278 Ma] ≤-6 (Lathrop et al, 1996). This would require Central Maine belt supracrustal rocks to underlie the Coastal lithotectonic belt despite the interpreted west-dipping fault (Hackmatack Pond boundary) that separates the two domains (e.g., Stewart et al, 1986). Hence, the proportion of Central Maine belt material involved in the genesis of the Topsham-Brunswick leucogranites is likely minimal.…”

Section: Constraints On Sourcesmentioning

confidence: 99%

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Significance of the Norumbega fault zone in southwestern Maine: Clues from the geochemistry of granitic rocks

Tomascak¹,

Krogstad²,

Walker³

1999

Norumbega Fault System of the Northern Appalachians

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Mineralogically distinct leucogranite bodies in the Topsham-Brunswick area of coastal southwestern Maine have principally Permian crystallization ages, and similar initial Nd (ε Nd [278 Ma] = -5.2 to -3.7) and Pb isotope compositions ( 206 Pb/ 204 Pb = 18.40-18.46; 207 Pb/ 204 Pb = 15.61-15.66; 208 Pb/ 204 Pb = 38.19-38.41), indicating their derivation from similar source materials. However, the major and trace element contrast between these rocks does not favor their relation through simple fractionation processes. The sources of the leucogranites are distinct from the sources of fine-grained biotite granites farther east in Phippsburg (ε Nd [278 Ma] = -2.4 to -1.6) and from country-rock migmatites (-2.9 to +0.8). The leucogranites have initial Pb isotopic compositions that overlap those of abundant evolved granitic pegmatites in Topsham.The biotite granite in Phippsburg may be derived completely from material with relatively juvenile Nd isotope signatures, comparable to Avalon-like basement or to the Topsham-Brunswick area migmatites. The Topsham-Brunswick leucogranite Nd isotope data require input from more evolved sources than the rocks they intrude. A Central Maine belt source component is not favored, due to regional tectonic relations. The leucogranite isotope data are best explained through derivation from non-North American sources. These sources display a degree of Nd isotope distinction from typical Avalonian basement. Juxtaposition across the Norumbega fault zone of granites derived from isotopically distinct basement sources may indicate that this structure is at some crustal level a fundamental division between different exotic basement terranes.

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Section: Geologic Contextmentioning

confidence: 99%

Section: Constraints On Sourcesmentioning

confidence: 99%

Significance of the Norumbega fault zone in southwestern Maine: Clues from the geochemistry of granitic rocks

Tomascak¹,

Krogstad²,

Walker³

1999

Norumbega Fault System of the Northern Appalachians

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“…The westernmost edge of the Appalachians, the Grenville Ramp (Figure 2), has been imaged as an east dipping zone of reflections that is also expressed as a pronounced Bouguer gravity gradient [Ando et al, 1984]. The nappe of slices of basement and sedimentary cover is thought to be responsible for the reflectivity of this zone [Stewart et al, 1986]. The Grenville Ramp also correlates with a major lateral velocity change in the upper and middle crust (Figure 2): from 6.5 km/s in the Grenville Province on the west side of the ramp to 5.9-6.4 km/s in the Appalachian Province on the east side of the ramp [Hughes and Luetgert, 1991].…”

Section: Grenville Provincementioning

confidence: 99%

Composition of the crust in the Grenville and Appalachian Provinces of North America inferred from V_P/V_S ratios

Musacchio¹,

Mooney²,

Luetgert³

et al. 1997

J. Geophys. Res.

111

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“…The major features of the gravity field (Stewart et al 1986, Fig. 2b) appear not to be related directly to presumed Palaeozoic terrane boundaries, as has been commonly assumed.…”

Section: Comparison Ofmentioning

confidence: 75%

Interpretation of migrated seismic reflection profiles across the northern Appalachians in Maine

Unger¹,

Stewart²,

Phillips³

1987

Geophys J Int

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A simple line-migration technique has been developed and applied to deep crustal reflection data collected in the northern Appalachians of Quebec and central Maine. Preliminary interpretation of these data, combined with the results of gravity and refraction studies, shows thinning of the crust in two distinct steps beneath the Silurian-Devonian Merrimack synclinorium and shows evidence for Mesozoic crustal stretching and dike intrusion.

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The Quebec-western Maine seismic reflection profile: Setting and first year results

Cited by 42 publications

References 5 publications

Significance of the Norumbega fault zone in southwestern Maine: Clues from the geochemistry of granitic rocks

Significance of the Norumbega fault zone in southwestern Maine: Clues from the geochemistry of granitic rocks

Composition of the crust in the Grenville and Appalachian Provinces of North America inferred from V_P/V_S ratios

Interpretation of migrated seismic reflection profiles across the northern Appalachians in Maine

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The Quebec-western Maine seismic reflection profile: Setting and first year results

Cited by 42 publications

References 5 publications

Significance of the Norumbega fault zone in southwestern Maine: Clues from the geochemistry of granitic rocks

Significance of the Norumbega fault zone in southwestern Maine: Clues from the geochemistry of granitic rocks

Composition of the crust in the Grenville and Appalachian Provinces of North America inferred from VP/VS ratios

Interpretation of migrated seismic reflection profiles across the northern Appalachians in Maine

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Product

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Composition of the crust in the Grenville and Appalachian Provinces of North America inferred from V_P/V_S ratios