Montagnais: A submarine impact structure on the Scotian Shelf, eastern Canada

Jansa, L. F.; Pe‐Piper, Georgia; Robertson, P. B.; Friedenreich, Otto R.

doi:10.1130/0016-7606(1989)101<0450:masiso>2.3.co;2

Cited by 59 publications

(57 citation statements)

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“…3d) (Jansa et al 1989). It is believed that the central high/uplift of the structure was a positive relief feature above the seafloor and an obstacle to ocean-bottom currents during post-early Eocene times (e.g., Jansa 1993).…”

Section: Post-impact Infillingmentioning

confidence: 99%

“…At Montagnais crater (Table 1), continuous reflections from post-impact strata of Eocene to Holocene age are observed along seismic reflection profiles tied to the deepwell drilled on the central uplift/high (Jansa et al 1989;Pilkington et al 1995), and there is clear evidence of draping of these sequences on the flanks of the central uplift (Fig. 3d).…”

Section: Post-impact Infillingmentioning

confidence: 99%

“…Collapse of this cavity starts at its base and causes a flow of water and rock debris toward the crater center (e.g., Shuvalov 2002). These processes at marinetarget craters may explain the lack of a raised crater rim at the Mjølnir (Tsikalas et al 1998a(Tsikalas et al , 1998bTsikalas and Faleide 2004), Lockne (Sturkell and Lindström 2004), Chesapeake Bay (Poag et al 1994(Poag et al , 2004, and Chicxulub (e.g., Morgan et al 2002a) craters, and the beveled crater rim at Montagnais crater (Jansa et al 1989;Jansa 1993) (cf. Figs.…”

Section: Post-impact Infillingmentioning

confidence: 99%

“…c) Chicxulub crater (re-interpreted part of profile Chicx-A1 across the northwest side of the crater rim [Snyder and Hobbs 1999b]). d) Montagnais crater (profile across the entire structure [modified from Jansa et al 1989]). e) Bosumtwi crater (re-interpreted part of profile B2000-1 ).…”

Section: Post-impact Infillingmentioning

confidence: 99%

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Post‐impact structural crater modification due to sediment loading: An overlooked process

Tsikalas

Faleide

2007

Meteorit & Planetary Scien

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Abstract-Post-impact crater morphology and structure modifications due to sediment loading are analyzed in detail and exemplified in five well-preserved impact craters: Mjølnir, Chesapeake Bay, Chicxulub, Montagnais, and Bosumtwi. The analysis demonstrates that the geometry and the structural and stratigraphic relations of post-impact strata provide information about the amplitude, the spatial distribution, and the mode of post-impact deformation. Reconstruction of the original morphology and structure for the Mjølnir, Chicxulub, and Bosumtwi craters demonstrates the long-term subsidence and differential compaction that takes place between the crater and the outside platform region, and laterally within the crater structure. At Mjølnir, the central high developed as a prominent feature during post-impact burial, the height of the peak ring was enhanced, and the cumulative throw on the rim faults was increased. The original Chicxulub crater exhibited considerably less prominent peakring and inner-ring/crater-rim features than the present crater. The original relief of the peak ring was on the order of 420-570 m (currently 535-575 m); the relief on the inner ring/crater rim was 300-450 m (currently ∼700 m). The original Bosumtwi crater exhibited a central uplift/high whose structural relief increased during burial (current height 101-110 m, in contrast to the original height of 85-110 m), whereas the surrounding western part of the annular trough was subdued more that the eastern part, exhibiting original depths of 43-68 m (currently 46 m) and 49-55 m (currently 50 m), respectively. Furthermore, a quantitative model for the porosity change caused by the Chesapeake Bay impact was developed utilizing the modeled density distribution. The model shows that, compared with the surrounding platform, the porosity increased immediately after impact up to 8.5% in the collapsed and brecciated crater center (currently +6% due to post-impact compaction). In contrast, porosity decreased by 2-3% (currently −3 to −4.5% due to post-impact compaction) in the peak-ring region. The lateral variations in porosity at Chesapeake Bay crater are compatible with similar porosity variations at Mjølnir crater, and are considered to be responsible for the moderate Chesapeake Bay gravity signature (annular low of −8 mGal instead of −15 mGal). The analysis shows that the reconstructions and the long-term alterations due to post-impact burial are closely related to the impact-disturbed target-rock volume and a brecciated region of laterally varying thickness and depthvarying physical properties. The study further shows that several crater morphological and structural parameters are prone to post-impact burial modification and are either exaggerated or subdued during post-impact burial. Preliminary correction factors are established based on the integrated reconstruction and post-impact deformation analysis. The crater morphological and structural parameters, corrected from post-impact loading and modification effects, can be used to better const...

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Section: Post-impact Infillingmentioning

confidence: 99%

Section: Post-impact Infillingmentioning

confidence: 99%

Section: Post-impact Infillingmentioning

confidence: 99%

Section: Post-impact Infillingmentioning

confidence: 99%

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Post‐impact structural crater modification due to sediment loading: An overlooked process

Tsikalas

Faleide

2007

Meteorit & Planetary Scien

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“…In the Mjalnir beds, no biological extinctions have been identified so far, which is also true for the similarly sized Eocene Montaganis crater of the Canadian east coast (Jansa et al, 1989). Both impacts were too small to cause extinctions according to the estimates of McLaren and Goodfellow (1 990) and Raup (1 990).…”

Section: Reconstruction Of the Impact Eventmentioning

confidence: 86%

Geochemical signals of the late Jurassic, marine Mjølnir impact

Dypvik¹,

Attrep²

1999

Meteorit & Planetary Scien

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Abstract-Of the only seven submarine impact craters that have been found globally, the Mj0lnir crater is one of the best preserved and retains crater and ejecta. Geochemical studies (organic pyrolysis using the Rock Eva1 technique and XRF analysis for major, minor, and trace elements) of the Institute for Petroleum Research (IKU) core 7430/10-U-01 that was taken fiom a drillhole located -30 km north-northeast of the crater rim show gradual establishment of anoxic sea floor conditions through the late Jurassic. These poorly ventilated water conditions were overturned due to the Mjslnir impact event. Waves and currents transported impact glass (which is now partly weathered to smectite) into the depositional area where the drillhole is located. The succeeding crater collapse transported impact material (e.g., shocked quartz and Ir) from the crater rim and deeper levels to the core site. Normal marine depositional conditions were established a short time after the crater collapsed.

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Geophysical Studies of Impact Craters

Morgan

Rebolledo-Vieyra

2012

Impact Cratering

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Montagnais: A submarine impact structure on the Scotian Shelf, eastern Canada

Cited by 59 publications

References 0 publications

Post‐impact structural crater modification due to sediment loading: An overlooked process

Post‐impact structural crater modification due to sediment loading: An overlooked process

Geochemical signals of the late Jurassic, marine Mjølnir impact

Geophysical Studies of Impact Craters

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