Transport and emplacement of crater and basin deposits

Oberbeck, V. R.; Morrison, R. H.; Hörz, Friedrich

doi:10.1007/bf00567505

Cited by 31 publications

(9 citation statements)

References 4 publications

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“…A unit's pristine basalt composition is based on the highest FeO and TiO 2 abundances obtained from craters within that unit. Although the regolith in any location is dominated by local material, over time impact gardening introduces an increasing amount of exotic material to a given location [ Arvidson et al , ; Oberbeck et al , ; Li and Mustard , ]. Therefore, regolith formed atop a basalt unit is expected to decrease in FeO and TiO 2 concentrations because the lunar highlands composition dominate the lunar crust by area and volume.…”

Section: Methodsmentioning

confidence: 99%

The basalts of Mare Frigoris

et al. 2015

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This paper discusses the methodology and results of a detailed investigation of Mare Frigoris using remote sensing data from Clementine, Lunar Prospector, and Lunar Reconnaissance Orbiter, with the objective of mapping and characterizing the compositions and eruptive history of its volcanic units. With the exception of two units in the west, Mare Frigoris and Lacus Mortis are filled with basalts having low‐TiO2 to very low TiO2, low‐FeO, and high‐Al2O3 abundances. These compositions indicate that most of the basalts in Frigoris are high‐Al basalts—a potentially undersampled, yet important group in the lunar sample collection for its clues about the heterogeneity of the lunar mantle. Thorium abundances of most of the mare basalts in Frigoris are also low, although much of the mare surface appears elevated due to contamination from impact gardening with the surrounding high‐Th Imbrium ejecta. There are, however, a few regional thorium anomalies that are coincident with cryptomare units in the east, the two youngest mare basalt units, and some of the scattered pyroclastic deposits and volcanic constructs. In addition, Mare Frigoris lies directly over the northern extent of the major conduit for a magma plumbing system that fed many of the basalts that filled Oceanus Procellarum, as interpreted by Andrews‐Hanna et al. (2014) using data from the Gravity Recovery and Interior Laboratory mission. The relationship between this deep‐reaching magma conduit and the largest extent of high‐Al basalts on the Moon makes Mare Frigoris an intriguing location for further investigation of the lunar mantle.

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Section: Methodsmentioning

confidence: 99%

The basalts of Mare Frigoris

et al. 2015

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“…BB has been considered by all authors as ballistic ejecta from the sedimentary target rocks (for a section on the preimpact target, see St€ offler et al 2013). Although the theory of ballistic sedimentation was first described by Oberbeck et al (1975) for craters on the airless Moon, it is perfectly applicable to BB emplacement: massive, mostly unshocked fragments from the sedimentary cover are ejected; they move along parabolic trajectories without substantial interaction with the atmosphere and with each other, fall back to the surface with approximately the same high velocity as they were ejected with (increasing at greater distance from the crater), and incorporate a substantial amount of local material into the ejecta blanket (Pohl et al 1977;H€ orz et al 1983).…”

Section: Bunte Breccia and Megablock Emplacementmentioning

confidence: 99%

Ries crater and suevite revisited—Observations and modeling Part II: Modeling

Artemieva

Wünnemann

Krien

et al. 2013

Meteorit & Planetary Scien

218

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Abstract-We present the results of numerical modeling of the formation of the Ries crater utilizing the two hydrocodes SOVA and iSALE. These standard models allow us to reproduce crater shape, size, and morphology, and composition and extension of the continuous ejecta blanket. Some of these results cannot, however, be readily reconciled with observations: the impact plume above the crater consists mainly of molten and vaporized sedimentary rocks, containing very little material in comparison with the ejecta curtain; at the end of the modification stage, the crater floor is covered by a thick layer of impact melt with a total volume of 6-11 km 3 ; the thickness of true fallback material from the plume inside the crater does not exceed a couple of meters; ejecta from all stratigraphic units of the target are transported ballistically; no separation of sedimentary and crystalline rocksas observed between suevites and Bunte Breccia at Ries-is noted. We also present numerical results quantifying the existing geological hypotheses of Ries ejecta emplacement from an impact plume, by melt flow, or by a pyroclastic density current. The results show that none of these mechanisms is consistent with physical constraints and/or observations. Finally, we suggest a new hypothesis of suevite formation and emplacement by postimpact interaction of hot impact melt with water or volatile-rich sedimentary rocks.

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“…2) Proximal layered deposits formed as described in Hypothesis 1, but cold spot surfaces further from the source crater were formed by gas flows across the lunar surface. Oberbeck (1975) and Oberbeck et al (1975) describe dune-like morphologies associated with crater ejecta. Initially, dilute pyroclastic density currents (base surges) were invoked as an explanation for these deposits, but the difficulty of forming base surges in a vacuum environment led Oberbeck (1975) to put forth the hypothesis that was termed ballistic sedimentation.…”

Section: Formation Mechanismsmentioning

confidence: 99%

Lunar cold spots: Granular flow features and extensive insulating materials surrounding young craters

Bandfield

Song

Hayne

et al. 2014

Icarus

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This is an author-produced, peer-reviewed version of this article. The final, definitive version of this document can be found online at Icarus, published by Elsevier. Copyright restrictions may apply. DOI: 10.1016DOI: 10. /j.icarus.2013 Abstract Systematic temperature mapping and high resolution images reveal a previously unrecognized class of small, fresh lunar craters. These craters are distinguished by near-crater deposits with evidence for lateral, ground-hugging transport. More distal, highly insulating surfaces surround these craters and do not show evidence of either significant deposition of new material or erosion of the substrate. The nearcrater deposits can be explained by a laterally propagating granular flow created by impact in the lunar vacuum environment. Further from the source crater, at distances of ~10-100 crater radii, the upper few to 10's of centimeters of regolith appear to have been "fluffed-up" without the accumulation of significant ejecta material. These properties appear to be common to all impacts, but quickly degrade in the lunar space weathering environment. Cratering in the vacuum environment involves a previously unrecognized set of processes that leave prominent, but ephemeral, features on the lunar surface. HighlightsSmall lunar craters are surrounded by granular flow deposits Extensive insulating surfaces extend beyond the granular flowsThe insulating surfaces show no evidence for impact related deposition or erosion These properties appear common to all small lunar impacts and are ephemeralThe structure of the upper regolith is modified by relatively distant small impacts 2 This is an author-produced, peer-reviewed version of this article. The final, definitive version of this document can be found online at Icarus, published by Elsevier. Copyright restrictions may apply.

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Transport and emplacement of crater and basin deposits

Cited by 31 publications

References 4 publications

The basalts of Mare Frigoris

The basalts of Mare Frigoris

Ries crater and suevite revisited—Observations and modeling Part II: Modeling

Lunar cold spots: Granular flow features and extensive insulating materials surrounding young craters

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