Geology of the Precambrian Basement Beneath the Paleozoic of Southwestern Ontario

Easton, R.M.; Carter, T. R.

doi:10.1007/978-94-017-0831-9_26

Cited by 14 publications

(11 citation statements)

References 14 publications

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“…One of the major features of the Paleoproterozoic basement of the United States is that it has been profusely intruded by Mesoproterozoic "anorogenic" plutons (Silver et al, 1977;Anderson, 1983); plu tons of this suite also extend into Labrador (e.g., Gower et al, 1990), and recent studies in the Grenville province (e.g., Easton, 1992;Easton and Carter, 1995;Dickin and Higgins, 1992) indi cate that many of the granitic gneisses have protoliths that included plutons of both age groups. In the Midcontinent region many of these plutons are magnetite-series granites and conse quently show up very well as small, circular anomalies on geo physical maps (Zietz, 1982;Zietz et al, 1984;Yarger, 1985).…”

Section: Accumulation Of Volcanic Units In the Western St Francoismentioning

confidence: 95%

“…4). Although its age is typi cal of the Frontenac terrane, the location is far west of outcrops of this terrane; thus we believe the rock sampled is most likely related to metamorphism of the Bancroft terrane of Easton (1992;and Easton and Carter, 1995), the westernmost of the CMB terranes. The rock sampled in drill hole MIWY-001 near Detroit is too far west to be related to CMB metamorphism.…”

Section: Zircon U-pb Ages In Southeastern Michigan and Southwestern Omentioning

confidence: 98%

“…1), and K-Ar ages show that it has been affected by ca. 1.0 to 1.1 Ga deformation and metamorphism (e.g., Turek and Robinson, 1982;Easton and Carter, 1995). Turek and Robinson (1984) compiled the geology of the Precambrian basement of southwestern Ontario from 536 drill holes and con cluded that granitic gneisses compose about 70% to 75% of the subcrop; clastic metasedimentary rocks compose the next largest area of subcrop (ca.…”

Section: Buried Basement O F Southwestern Ontariomentioning

confidence: 99%

“…18%), and minor amounts of metagabbro, marble, and other metamorphic rocks compose the remainder of the basement. This region is generally regarded as the southern extension of the central gneiss belt of the Grenville province (e.g., Easton, 1992;Easton and Carter, 1995).…”

Section: Buried Basement O F Southwestern Ontariomentioning

confidence: 99%

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Proterozoic geology of the east-central Midcontinent basement

Schmus¹,

Bickford²,

Turek³

1996

Basement and Basins of Eastern North America

123

149

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The Precambrian basement beneath much of Illinois, Michigan, southwestern Ontario, Indiana, western Ohio, western Kentucky, and southeastern Missouri (including exposures in the S t Francois Mountains) is known as the eastern granite-rhyolite prov ince. This crust is characterized by undeformed and mostly unmetamorphosed highsilica rhyolite to dacite with epizonal granite of equivalent composition having zircon UPb ages of 1,470 ± 30 Ma. The Precambrian subcrop beneath parts of southwestern Mis souri, southern Kansas, northern Arkansas, most of Oklahoma (including small areas of outcrop), and the panhandle of Texas is known as the southern granite-rhyolite province. This crust is also characterized by undeformed and mostly unmetamorphosed high-silica rhyolite to dacite with epizonal granite, but zircon U-Pb ages from this province are about 100 m.y. younger, 1,370 ± 30 Ma. We have obtained additional zircon U-Pb ages and whole-rock Sm-Nd data for many drill-hole samples and a few outcrop samples from these provinces to (1) define their geographic limits more accurately, and (2) use them as a means of defining the age of the crust which presumably underlies these two provinces and from which the granite and rhyolite magmas were derived.These granite-rhyolite provinces were previously thought to have formed from anatectic melting of preexisting Paleoproterozoic crust, which is a southward and eastward extension of the 1,600 to 1,800 Ma Central Plains orogen. However, recent Sm-Nd stud ies, including additional data reported here, indicate that some of the rhyolite and gran ite from both the eastern granite-rhyolite province and the southern granite-rhyolite province have Nd crustal residence ages indicating magma derivation from juvenile, mantle-derived sources that are only slightly older than the granites and rhyolites them selves. As a result, a relatively sharp boundary can be defined that separates Mesoproterozoic granites and rhyolites (regardless of age) having Nd crustal residence ages indicative of Paleoproterozoic crustal sources (TDM > 1,550 Ma) from ones having younger crustal sources (TDM < 1,550 Ma). This boundary extends northeasterly from southeastern Oklahoma through southeastern Missouri, southern Illinois, central Indi ana, southeastern Michigan, and into southwestern Ontario; its southwestern extension is not defined, but it probably parallels, and may be close to, the northwestern boundary of the Llano province in Texas. The underlying crust northwest of boundary line is inferred to be Paleoproterozoic, whereas the underlying crust southeast of this bound- Van Schmus, W. R., Bickford, M. E., and Turek, A., 1996, Proterozoic geology of the east-central Midcontinent basement, in van der Pluijm, B. A., and Catacosinos, P. A., eds., Basement and Basins of Eastern North America: Boulder, Colorado, Geological Society of America Special Paper 308. 7 on May 15, 2015 specialpapers.gsapubs.org Downloaded from 8 W. R. Van Schmus and Othersary is inferred to be Mesoproterozoic. We interpret this boundary ...

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Section: Accumulation Of Volcanic Units In the Western St Francoismentioning

confidence: 95%

Section: Zircon U-pb Ages In Southeastern Michigan and Southwestern Omentioning

confidence: 98%

Section: Buried Basement O F Southwestern Ontariomentioning

confidence: 99%

Section: Buried Basement O F Southwestern Ontariomentioning

confidence: 99%

See 2 more Smart Citations

Proterozoic geology of the east-central Midcontinent basement

Schmus¹,

Bickford²,

Turek³

1996

Basement and Basins of Eastern North America

123

149

View full text Add to dashboard Cite

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“…2), a region characterized by relatively thin (Ͻ1.0 km), flat-lying calcareous Paleozoic strata between the Appalachian Orogen and the Grenville Province of the Canadian Shield (Williams, 1984;Williams et al, 1991). This region is underlain by a broad northeast-trending basement arch, comprising the Algonquin and Findlay Arches, separating the Appalachian (Allegheny) and Michigan sedimentary basins (Easton and Carter, 1995). The Frontenac Arch and Adirondack Mountains bound the area on the northeast and east, respectively.…”

Section: Tectonic Settingmentioning

confidence: 99%

Seismicity of the Southern Great Lakes: Revised Earthquake Hypocenters and Possible Tectonic Controls

Dineva

Eaton

Mereu

2004

Bulletin of the Seismological Society of America

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Using data from 27 seismograph stations for the period 1990-2001, we have relocated 106 hypocenters of earthquakes with magnitudes from 0.9 to 5.4 in the region of the southern Great Lakes. Two complementary methods were used for relocation: a conventional least-squares approach (Lienert and Havskov, 1995) and joint hypocentral determination (Pujol, 2000). These two methods yielded mutually consistent spatial patterns of seismicity with an average difference of 3.7 km in epicentral locations and 1.1 km in focal depths. We show that the hypocenter locations are not very sensitive to realistic uncertainties in 1D crustal velocity. Our sharpened definition of zones of seismicity delineates several clusters beneath Lake Ontario, around Niagara Falls, and near the south shore of Lake Erie. These seismicity zones appear to correlate with areas where the regional magnetic data exhibit prominent short-wavelength (Ͻ5 km) linear anomalies. The magnetic anomalies are associated with basement structures that formed during the Precambrian (Mesoproterozoic) Grenville orogen. Both the seismicity and magnetic anomalies exhibit statistically significant preferred orientations at N40ЊE-N45ЊE, but the correlation of the earthquake clusters with specific aeromagnetic lineaments remains uncertain. Three preliminary focal mechanisms of earthquakes with magnitudes m N 3.1 to 3.8 show unusual normal faulting, with nodal planes in almost the same direction as the magnetic trends, N42ЊE-N52ЊE. Proximity of the earthquake clusters to large bodies of water, coupled with colinearity with magnetic anomaly trends, suggests that both surface water and pre-existing basement structures may play significant roles in controlling intraplate seismicity in the southern Great Lakes region.

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