Comparison of Mid‐Size Terrestrial Complex Impact Structures: A Case Study

Osinski, G. R.; Grieve, R. A. F.

doi:10.1002/9781118447307.ch19

Cited by 4 publications

(4 citation statements)

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“…There are further complications in that a number of only slightly eroded terrestrial complex structures (e.g., Haughton, Canada [ D = 23 km]; Ries, Germany [ D = 26 km]; Zhamanshin, Kazakhstan [ D = 14 km]) lack an emergent central peak (Grieve and Therriault ). This has been ascribed to target effects (Grieve and Therriault ; Osinski and Grieve ); all these structures formed in targets of sedimentary rock overlying crystalline basement. It is, therefore, clear that target lithology plays an important—but as yet not fully understood—role in determining the morphology and morphometry of lunar and terrestrial impact craters.…”

Section: Introductionmentioning

confidence: 99%

Transitional impact craters on the Moon: Insight into the effect of target lithology on the impact cratering process

Osinski

Silber

Clayton

et al. 2018

Meteorit & Planetary Scien

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We studied a data set of 28 well‐preserved lunar craters in the transitional (simple‐to‐complex) regime with the aim of investigating the underlying cause(s) for morphological differences of these craters in mare versus highland terrains. These transitional craters range from 15 to 42 km in diameter, demonstrating that the transition from simple to complex craters is not abrupt and occurs over a broad diameter range. We examined and measured the following crater attributes: depth (d), diameter (D), floor diameter (Df), rim height (h), and wall width (w), as well as the number and onset of terraces and rock slides. The number of terraces increases with increasing crater size and, in general, mare craters possess more terraces than highland craters of the same diameter. There are also clear differences in the d/D ratio of mare versus highland craters, with transitional craters in mare targets being noticeably shallower than similarly sized highland craters. We propose that layering in mare targets is a major driver for these differences. Layering provides pre‐existing planes of weakness that facilitate crater collapse, thus explaining the overall shallower depths of mare craters and the onset of crater collapse (i.e., the transition from simple to complex crater morphology) at smaller diameters as compared to highland craters. This suggests that layering and its interplay with target strength and porosity may play a more significant role than previously considered.

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Section: Introductionmentioning

confidence: 99%

Transitional impact craters on the Moon: Insight into the effect of target lithology on the impact cratering process

Osinski

Silber

Clayton

et al. 2018

Meteorit & Planetary Scien

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“…During the following excavation stage, the melt was mainly ejected towards the NW and in the modification, stage flowed down covering the impact breccias fallen within the crater floor. This stratigraphic sequence is indeed common within several complex impact craters on Earth and other Terrestrial bodies (e.g., Osinski et al 2011;Osinski and Grieve, 2016;Grieve and Therriault, 2016). The gas trapped within voids in the melt was afterwards expelled producing degassing features and ejecta as envisaged already by Howard (1975).…”

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confidence: 68%

Geologic evolution and map of Copernicus Crater interior (Moon)

Tusberti,

Massironi,

Pozzobon

et al. 2024

GFT

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“…Tunnunik is a mid‐size impact structure with an ~10 km wavelength negative Bouguer gravity anomaly of ~3 mGal amplitude over its center. Midsize complex impact craters (see Osinski and Grieve for a review) are typically characterized by circular negative gravity anomalies that extend to or beyond the crater diameter. The size and amplitude of the anomaly are expected to increase with an increasing apparent crater diameter D a (Pilkington and Grieve ; Grieve and Pilkington ).…”

Section: Discussionmentioning

confidence: 99%

Geophysical signature of the Tunnunik impact structure, Northwest Territories, Canada

Quesnel

Zylberman

Rochette

et al. 2020

Meteorit & Planetary Scien

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In 2011, the discovery of shatter cones confirmed the 28 km diameter Tunnunik complex impact structure, Northwest Territories, Canada. This study presents the first results of ground-based electromagnetic, gravimetric, and magnetic surveys over this impact structure. Its central area is characterized by a~10 km wide negative gravity anomaly of about 3 mGal amplitude, roughly corresponding to the area of shatter cones, and associated with a positive magnetic field anomaly of~120 nT amplitude and 3 km wavelength. The latter correlates well with the location of the deepest uplifted strata, an impact-tilted Proterozoic dolomite layer of the Shaler Supergroup exposed near the center of the structure and intruded by dolerite dykes. Locally, electromagnetic field data unveil a conductive superficial formation which corresponds to an 80-100 m thick sand layer covering the impact structure. Based on the measurements of magnetic properties of rock samples, we model the source of the magnetic anomaly as the magnetic sediments of the Shaler Supergroup combined with a core of uplifted crystalline basement with enhanced magnetization. More classically, the low gravity signature is attributed to a reduction in density measured on the brecciated target rocks and to the isolated sand formations. However, the present-day fractured zone does not extend deeper than~1 km in our model, indicating a possible 1.5 km of erosion since the time of impact, about 430 Ma ago. PLAIN LANGUAGE SUMMARYThis study reveals the geophysical signature of the buried structure of an eroded impact crater, Tunnunik, located in Northwest Territories, Canada. A positive magnetic anomaly was detected at the center, showing the uplift of some deep geological formations and the possible presence of strongly magnetized basement. A negative gravimetric anomaly is also observed, mostly corresponding to the fracturing/brecciation of the impacted rocks inside the crater. Using numerical models constrained by laboratory measurements on rock samples, the physical properties and geometry of the buried geological formations are estimated. An important implication of this study is the link between the geophysical remains of an impact crater and the postimpact erosion. KEY POINTSA 3 mGal negative gravity anomaly and a 120 nT positive magnetic anomaly were measured over the center of the Tunnunik impact structure. A numerical model constrained by laboratory measurements on rock samples suggests an uplifted magnetic crystalline basement. The fracturing/brecciation extends down to 1 km in depth.

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Comparison of Mid‐Size Terrestrial Complex Impact Structures: A Case Study

Cited by 4 publications

References 58 publications

Transitional impact craters on the Moon: Insight into the effect of target lithology on the impact cratering process

Transitional impact craters on the Moon: Insight into the effect of target lithology on the impact cratering process

Geologic evolution and map of Copernicus Crater interior (Moon)

Geophysical signature of the Tunnunik impact structure, Northwest Territories, Canada

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