Measuring gravity on ice: an example from Wanapitei Lake, ON, Canada

Ugalde, Hernan; L’Heureux, Elizabeth; Milkereit, B.; Lachapelle, Richard

doi:10.1190/1.1845292

Cited by 2 publications

(3 citation statements)

References 5 publications

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“…Dikes are demagnetized or vaporized in a central area with a diameter of ~3 km. (Ugalde et al, 2004). Increased sampling shows that the shape of the anomaly is concordant to the regional geologic framework rather than simply circular.…”

Section: Discussion Of Resultsmentioning

confidence: 95%

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Using vertical dikes as a new approach to constraining the size of buried craters: An example from Lake Wanapitei, Canada

L’Heureux¹,

Ugalde²,

Milkereit³

et al. 2005

Large Meteorite Impacts III

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Lake Wanapitei, located within the Southern Province of Ontario, Canada, provides the setting for a unique study of an impact crater situated within a shield environment. Evidence for the 7.5-km-diameter Wanapitei impact includes a circular Bouguer gravity low centered over the central area of the lake and features of shock metamorphism in samples of glacial drift found on the southern shores. Geophysical studies of craters in hard-rock environments are often limited by the lack of markers used for exploration; this may be overcome with the use of the large igneous dike swarms that characterize Archean terrains. The 1.2 Ga Sudbury dike swarm predates the impact that is suggested to have generated Lake Wanapitei and provides the setting for a study to constrain the size and location of the impact crater. The swarm is clearly visible on aeromagnetic maps as high amplitude, linear features, suggesting they could be used as vertical markers indicative of structural changes having an effect on target rock susceptibilities.To fully establish the size of the crater, a total fi eld magnetic map was produced to trace the Sudbury dikes through the proposed crater center. A gap in their signature, expressed as a 100 nT low, 2-3 km in width, constrains the size of the crater to <5 km. Numerical modeling suggests that a crater of this size will demagnetize target rocks, producing a low in the total magnetic fi eld, up to a maximum diameter of 3 km. Dikes L'Heureux, E., Ugalde, H., Milkereit, B., Boyce, J., Morris, W., Eyles, N., and Artemieva, N., 2005, Using vertical dikes as a new approach to constraining the size of buried craters: An example

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Section: Discussion Of Resultsmentioning

confidence: 95%

“…Recently, new gravity data was collected that provides a fi ner sampling of the anomaly over Lake Wanapitei (Ugalde et al, 2004). The fi nal Bouguer map, including terrain corrections, shows a smaller, less circular low in the central area of the lake (Fig.…”

Section: Discussion Of Resultsmentioning

confidence: 98%

Using vertical dikes as a new approach to constraining the size of buried craters: An example from Lake Wanapitei, Canada

L’Heureux¹,

Ugalde²,

Milkereit³

et al. 2005

Large Meteorite Impacts III

View full text Add to dashboard Cite

show abstract

“…This 7-km structure, however, is also the host of a dike swarm of 1200 Ma, a feature that helps the comprehension of the rocks below the surface based on magnetic studies (L'Heureux et al 2005). Ugalde et al (2006) suggest that the N-S trend observed in the gravity anomaly map is related to a regional fault zone of 2200-1900 Ma that has gone through reactivation over time.…”

Section: Discussionmentioning

confidence: 94%

3D gravimetric investigation of the Cerro do Jarau structure, Rio Grande do Sul, Brazil

Giacomini

Leite

Crósta

2017

Meteorit & Planetary Scien

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The Cerro do Jarau structure is possibly the third Brazilian basaltic crater formed in continental flood basalt of the Serra Geral Formation, Paraná Basin, a large igneous province (LIP) in southern Brazil. It is a nearly circular landform with a diameter of approximately 13 km that rises 200 m above the plains of the “pampas” in southern Brazil. In this work, Bouguer anomalies were calculated from gravity accelerations measured on the area of this structure. The residual Bouguer map shows a strong positive anomaly trending NE‐SW, located in the northeastern part of the structure, a feature not commonly associated with impact structures. However, the negative anomaly present in its center and the circular positive anomaly surrounding the central portion are typical of impact structures. The residual Bouguer anomaly varies from −2 mGal to 8 mGal. The positive circular anomaly is not spatially coincident with the rim of the structure. Based on the interpretation of our gravimetric data, the estimated diameter of the structure is 12 km and the central portion has a diameter of approximately 5 km, both slightly smaller than previously suggested. The Bouguer anomaly map was inverted into a 3D density model using a constrained inversion method with a maximum density contrast of 0.5 g cm−3. This model was interpreted to associate densities with rock types, resulting in a geological model. This geological model is in accordance with the meteorite impact nature of Cerro do Jarau.

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Measuring gravity on ice: an example from Wanapitei Lake, ON, Canada

Cited by 2 publications

References 5 publications

Using vertical dikes as a new approach to constraining the size of buried craters: An example from Lake Wanapitei, Canada

Using vertical dikes as a new approach to constraining the size of buried craters: An example from Lake Wanapitei, Canada

3D gravimetric investigation of the Cerro do Jarau structure, Rio Grande do Sul, Brazil

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