Multiphase U-Pb geochronology of sintered breccias from the Steen River impact structure, Canada: Mixed target considerations for a Jurassic-Cretaceous boundary event

McGregor, Maree; Walton, E. L.; McFarlane, Christopher R.M.; Spray, John G.

doi:10.1016/j.gca.2020.01.052

Cited by 10 publications

(4 citation statements)

References 86 publications

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“…This extensive study has suggested a revision of the J–K boundary, reducing its age to between 140.7 and 140.9 Ma. Based on these radioisotopic data, a link between the J–K boundary and the Steen River impact structure in Canada has also been suggested, with an LA‐ICP‐MS U–Pb age of 141 ± 4 Ma for apatites (McGregor et al., 2020). The LA‐ICP‐MS U–Pb dating of zircons from the fossil‐bearing Late Jurassic to Early Cretaceous volcaniclastic sandstones of the Murihiku Terrane (New Zealand) has provided significant components in the age range 140–143 Ma, possibly straddling the J–K boundary (Browne et al., 2020).…”

Section: Discussionmentioning

confidence: 99%

Provenance and the U–Pb age constraints on the tuff beds of the Late Jurassic–Early Cretaceous Bazhenovo Formation, West Siberian Basin

Bulatov,

Yermakov,

Kulikova

et al. 2024

The Depositional Record

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Thin tuff beds of the Late Jurassic–Early Cretaceous Bazhenovo Formation are laterally widespread in the central part of the West Siberian Basin (ca 0.5 million km2). However, the source of the tuff beds remains unclear. The stratigraphy, geochemistry and geochronology of the tuff beds were investigated to reveal their magmatic origin and potential source region. Most of the tuff beds are recorded in member 4 and can be correlated through the Bazhenovo sequence. Thin‐section petrography and X‐ray diffraction indicate that the tuffs mostly comprise clay minerals and K‐feldspars. Less common minerals are plagioclase, quartz and pyrite. The geochemical composition of the Bazhenovo tuff beds suggests a parental magma origin of andesite/basalt, which came from volcanic arc‐related settings. Considering the results of geochemical studies along with LA‐ICP‐MS zircon U–Pb dating (141.3 ± 0.3/2.8 Ma), the palaeovolcanoes of the Caucasus region or south‐east Mongolia–North‐East China are one of the potential source regions of the tuffs. The record of these tuffs indicates the intensive volcanic eruption during the Volgian–Ryazanian, accompanied by a very low‐sedimentation rate and preservation in a reducing environment. The tuff beds have broad implications as an isochronous marker horizon and constraints for the numerical age of the Jurassic–Cretaceous boundary in the Boreal Realm.

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Section: Discussionmentioning

confidence: 99%

Provenance and the U–Pb age constraints on the tuff beds of the Late Jurassic–Early Cretaceous Bazhenovo Formation, West Siberian Basin

Bulatov,

Yermakov,

Kulikova

et al. 2024

The Depositional Record

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“…The Steen River is a complex impact structure formed at 141 ± 4 Ma and located in northwest Alberta, Canada (McGregor et al., 2020; Walton et al., 2016; Figure 3). The structure is entirely buried, elliptical in shape, and has a rim‐to‐rim diameter along its major axis of ~25 km (~20 km minor axis).…”

Section: Regional Context and Sample Observationsmentioning

confidence: 99%

Pressure–temperature–time controls on shock vein formation within the Steen River impact structure

Hopkins,

Spray,

Walton

2024

Meteorit & Planetary Scien

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Thermodynamic modeling has been applied to determine pressure–temperature–time conditions leading to shock vein formation during the passage of a natural shock wave generated by hypervelocity impact. The approach is novel in considering both shock front and rarefaction pressures, as well as simultaneously forming and cooling the shock veins via two‐dimensional steady‐state conduction. Model results are tested using shock veins developed in granitic rocks that constitute the central uplift of the Steen River impact structure in Canada. Here, two variants of majoritic garnet were generated in different settings: (1) along the margins of shock veins due to pargasite and biotite breakdown (accompanied by maskelynite formation), and (2) within the originally molten shock vein matrix as newly grown crystals. We determine that during shock vein formation, the shock front pressure and wave width at the reconstructed sample location were 18 GPa and 830 m, respectively, with a dwell time of 160 ms. Intra‐vein melting at 2150°C was attained within 1 μs. Melt cooled to the solidus in 150 ms following shock front passage. Majoritic garnet formation was facilitated by the high temperatures realized within the veins as a result of frictional melting that accompanied shock loading. The calculated pressure–temperature–time (P–T–t) path provides constraints on the formation conditions of majoritic garnet at Steen River. The model results independently support previously determined P–T conditions based on mineral stability fields. The vein margin garnets (35–39 mole% majorite) and maskelynite formed first under higher P–T conditions for a longer duration (36 ms). The matrix garnets (11–22 mole% majorite) crystallized from melt under lower P–T conditions and for a shorter duration (22 ms). Our results indicate that shock pressure alone should not be used as a basis for shock classification. Instead, the interplay between pressure and temperature with time and the duration of shock immersion (dwell) must be considered.

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“…Many accessory minerals of geochemical and geochronological interest occur as granular aggregates at terrestrial impact structures, where they may provide accurate impact ages, though granular silicates have not been noted. These include zircon (Cavosie & Koeberl, 2019; McGregor et al., 2018), apatite (Kenney et al., 2019; McGregor et al., 2019), titanite (McGregor et al., 2020), and monazite (Erickson, 2018), from shocked rocks. They are generally interpreted as neoblasts, due to solid‐state recrystallization after severe shock deformation.…”

Section: Phenomena Related To Shock Meltingmentioning

confidence: 99%

Pervasive shock melting at >65 GPa in a Martian basalt, the shergottite Northwest Africa 14672

Hewins

Leroux

Jacob

et al. 2023

Meteorit & Planetary Scien

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Shergottites have provided abundant information on the volcanic and impact history of Mars. Northwest Africa (NWA) 14672 contributes to both of these aspects. It is a vesicular ophitic depleted olivine–phyric shergottite, with average plagioclase An61Ab39Or0.2. It is highly ferroan, with pigeonite compositions En49‐25Fs41‐61Wo10‐14 like those of basaltic shergottites, for example, NWA 12335. Olivine (Fo53‐15) has discrete ferroan overgrowths, more ferroan when in contact with plagioclase than when enclosed by pyroxene. The pyroxene (a continuum of augite, subcalcic augite, and pigeonite) is patchy, with ragged “cores” enveloped or invaded by ferroan pyroxene. Magma mixing may be responsible for capture of olivine and formation of pyroxene mantles. The plagioclase is maskelynite‐like in appearance, but the original laths were (congruently) melted and the melt partly crystallized as fine dendrites. Most of the 14% vesicles occur within plagioclase. Olivine, pyroxene, and ilmenite occur in part as fine aggregates crystallized after congruent melting with limited subsequent liquid mixing. There are two fine‐grained melt components, barred plagioclase with interstitial Fe‐bearing phases, and glass with olivine dendrites, derived by melting of mainly plagioclase and mainly pyroxene, respectively. Rare silica particles contain coesite and/or quartz, and silica glass. The rock has experienced >50% melting, compatible with peak pressure >~65 GPa. It is the most highly shocked shergottite so far, at shock stage S6/7. It may belong to the group of depleted shergottites ejected at ~1 Myr from Tooting Crater.

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Multiphase U-Pb geochronology of sintered breccias from the Steen River impact structure, Canada: Mixed target considerations for a Jurassic-Cretaceous boundary event

Cited by 10 publications

References 86 publications

Provenance and the U–Pb age constraints on the tuff beds of the Late Jurassic–Early Cretaceous Bazhenovo Formation, West Siberian Basin

Provenance and the U–Pb age constraints on the tuff beds of the Late Jurassic–Early Cretaceous Bazhenovo Formation, West Siberian Basin

Pressure–temperature–time controls on shock vein formation within the Steen River impact structure

Pervasive shock melting at >65 GPa in a Martian basalt, the shergottite Northwest Africa 14672

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