Wrinkle ridges are a common feature of the lunar maria and record subsequent contraction of mare infill. Constraining the timing of wrinkle ridge formation from crater counts is challenging because ...they have limited areal extent and it is difficult to determine whether superposed craters post-date ridge formation or have alternatively been uplifted by the deformation. Some wrinkle ridges do allow determination to be made. This is possible where a ridge shows a sufficiently steep boundary or scarp that can be identified as deforming an intersecting crater or the crater obliterates the relief of the ridge. Such boundaries constitute only a small fraction of lunar wrinkle ridge structures yet they are sufficiently numerous to enable us to obtain statistically significant crater counts over systems of structurally related wrinkle ridges. We carried out a global mapping of mare wrinkle ridges, identifying appropriate boundaries for crater identification, and mapping superposed craters. Selected groups of ridges were analyzed using the buffered crater counting method. We found that, except for the ridges in mare Tranquilitatis, the ridge groups formed with average ages between 3.5 and 3.1 Ga ago, or 100–650 Ma after the oldest observable erupted basalts where they are located. We interpret these results to suggest that local stresses from loading by basalt fill are the principal agent responsible for the formation of lunar wrinkle ridges, as others have proposed. We find a markedly longer interval before wrinkle ridge formation in Tranquilitatis which likely indicates a different mechanism of stress accumulation at this site.
•We demonstrate a new approach to date lunar wrinkle ridges.•A global survey of wrinkle ridges ages was made using buffered crater counting.•Ridge groups show average ages between 3.5 and 3.1 Ga, typically around 0.5 Ga after emplacement of oldest local mare basalts.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Accurate estimates of mare basalt ages are necessary to place constraints on the duration and the flux of lunar volcanism as well as on the petrogenesis of lunar mare basalts and their relationship ...to the thermal evolution of the Moon. We performed new crater size‐frequency distribution measurements in order to investigate the stratigraphy of mare basalts in Oceanus Procellarum and related regions such as Mare Nubium, Mare Cognitum, and Mare Insularum. We used high‐resolution Clementine color data to define 86 spectrally homogeneous units within these basins, which were then dated with crater counts on Lunar Orbiter IV images. Our crater size‐frequency distribution measurements define mineralogical and spectral surface units and offer significant improvements in accuracy over previous analyses. Our data show that volcanism in the investigated region was active over a long period of time from ∼3.93 to 1.2 b.y., a total of ∼2.7 b.y. Volumetrically, most of the basalts erupted in the Late Imbrian Period between ∼3.3 and 3.7 b.y., and we see evidence that numerous units have been resurfaced. During the Eratosthenian Period, significantly less basalt was erupted. Depending on the absolute model ages that one can assign to the lunar chronostratigraphic systems, five units might be of Copernican age. Younger basalts are generally exposed in the center of the investigated area, that is, closer to the volcanic centers of the Aristarchus Plateau and Marius Hills. Older basalts occur preferentially along the northwestern margin of Oceanus Procellarum and in the southeastern regions of the studied area, i.e., in Mare Cognitum and Mare Nubium. Combining the new data with our previously measured ages for basalts in Mare Imbrium, Serenitatis, Tranquillitatis, Humorum, Australe, and Humboldtianum, we find that the period of active volcanism on the Moon lasted ∼2.8 b.y., from ∼4 b.y. to ∼1.2 b.y. On the basis of the basalts dated so far, which do not yet include the potentially young basalts of Mare Smythii e.g.,all investigated basins but probably also is the location of some of the youngest basalts on the lunar surface.
Impact basin formation is a fundamental process in the evolution of the Moon and records the history of impactors in the early solar system. In order to assess the stratigraphy, sequence, and ages of ...impact basins and the impactor population as a function of time, we have used topography from the Lunar Orbiter Laser Altimeter (LOLA) on the Lunar Reconnaissance Orbiter (LRO) to measure the superposed impact crater size‐frequency distributions for 30 lunar basins (D ≥ 300 km). These data generally support the widely used Wilhelms sequence of lunar basins, although we find significantly higher densities of superposed craters on many lunar basins than derived by Wilhelms (50% higher densities). Our data also provide new insight into the timing of the transition between distinct crater populations characteristic of ancient and young lunar terrains. The transition from a lunar impact flux dominated by Population 1 to Population 2 occurred before the mid‐Nectarian. This is before the end of the period of rapid cratering, and potentially before the end of the hypothesized Late Heavy Bombardment. LOLA‐derived crater densities also suggest that many Pre‐Nectarian basins, such as South Pole‐Aitken, have been cratered to saturation equilibrium. Finally, both crater counts and stratigraphic observations based on LOLA data are applicable to specific basin stratigraphic problems of interest; for example, using these data, we suggest that Serenitatis is older than Nectaris, and Humboldtianum is younger than Crisium. Sample return missions to specific basins can anchor these measurements to a Pre‐Imbrian absolute chronology.
Key Points
New measurements of crater statistics and stratigraphy for 30 lunar basins
Any transition in lunar impactor populations occurred before the mid‐Nectarian
The oldest lunar basins are likely cratered to saturation equilibrium
Provider: - Institution: - Data provided by Europeana Collections- Monumentul, realizat din marmură și beton, este alcătuit din postament în două trepte, soclu și obelisc ale cărui muchii sunt ...decorate cu reprezentări de frunze de laur. Deasupra obeliscului este fixată reprezentarea unui proiectil de tun. Monumentul este inscripționat, pe toate fețele și pe verso, cu nume de militari germani și cu dedicații. Dimensiuni: 88 x 84cm.- Mențiuni despre monument: Stare bună de conservare.- Inscripții pe monument: Pe fața principală, în limbile română și germană cu litere latine și gotice: „ÎN AMINTIREA EROILOR MORȚI ȘI DISPĂRUȚI ÎN RĂZBOIUL MONDIAL DIN COMUNA JAMUL MARE” „IN EHREN DER GEFALLENEN UND VERMISSTEN HELDEN IM WELTKRIEGE 1914-1918 IN GEMEINDE JAMUL MARE. EUER TOD UNSER LEBEN” Pe verso: NUME DE EROI (8) Stânga: „MORȚI. GEFALLENEN” NUME DE EROI (35) Dreapta: „MORȚI. GEFALLENEN” NUME DE EROI (10) „DISPĂRUȚI. VERMISSTE” NUME DE EROI (24)- All metadata published by Europeana are available free of restriction under the Creative Commons CC0 1.0 Universal Public Domain Dedication. However, Europeana requests that you actively acknowledge and give attribution to all metadata sources including Europeana
High alumina (HA) mare basalts play unique roles in understanding the heterogeneity of lunar mantle. Their presence was confirmed by the Apollo and Luna samples, and their remote sensing ...identification was implemented using HA sample FeO, TiO2 and Th concentration constraints. This study selected the surfaces with ~0.5% rock abundance as windows into HA basalts identification. The lithology of these rock pixels was first classified based on thorium maps from the Lunar Prospector and major element oxide products from Diviner data onboard the Lunar Reconnaissance Orbiter (LRO). Then, the LRO Diviner Al2O3 (~11 wt%) concentration constraint was applied in the mare basalt rock pixels across the Moon. The mare-highland mixtures were distinguished from HA basalt rocks based on the positive linear relationships between Al2O3 and Mg# in the adjacent pixels for four impact vector directions away from each candidate HA pixel. These HA basalts rock pixels identified by this study indicate that HA basalts are concentrated locally in South Pole-Aitken (SPA) basin, Schiller-Schickard region and 13 maria such as southern and northern Oceanus Procellarum, central Humorum, Tranquillitatis, Fecunditatis and Serenitatis, northern Imbrium and southern Nubium, but are seldom found in Mare Moscoviense and Orientale regions on the farside. Detailed investigations in Mare Fecunditatis found that fifteen HA basalt units or patches could be confidently identified. These HA basalts have the total area and volume of <77,658 km2 and <54,301 km3, and the maximum depth and thickness of 1147 m and 1062 m respectively. In addition, analyses of the HA rocks indicated that the HA basalts are discontinuous and have variable thicknesses.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The formation ages of lunar impact basins are critical to understanding the late accretion history of the inner solar system. Furthermore, the correct interpretation of the provenance and isotopic ...dates of basin-derived impact melt (‘basin melt’) is essential for the calibration of lunar chronology function. However, abundances of basin melt in the lunar near-surface are not well understood. Basin melt has been gardened by a long sequence of subsequent impact events, altering its abundance and size distribution. We developed a numerical model to investigate this process by means of the Monte Carlo method in a spatially resolved model. The fraction of melt in ejecta was tracked globally and at the Apollo 14–17 and Luna 20 sampling sites and was compared with K-Ar age distributions of lunar impact melt breccias. It was found that melt produced by the very large SPA basin as well as the relatively late-forming Imbrium basin should be dominant in the near-surface (top one meter). The simulation shows that the melt component at the Apollo 14–17 and Luna 20 sites is strongly affected by nearby mid- to late-forming basins. Imbrium melt should be abundant in Apollo 14–17 samples; Crisium melt is the most significant component of basin-sourced melt in Luna 20 samples; all the Apollo 14–17 and Luna 20 samples could include melt from Serenitatis and the SPA basin; Nectaris melt should occur in Apollo 16, Apollo 17 and Luna 20 samples; and Orientale melt has no significant mixing in the Apollo 14–17 and Luna 20 sampling sites. In general, besides a prominent age peak at 3.9 Ga (related to the Imbrium basin), the model predicts pronounced abundance peaks of older basin melt (>3.9 Ga) which tend to be absent from distributions of K-Ar ages of impactites from landing sites. The diffusion characteristics of basin melt suggest that for future sampling aimed at collecting early basin melt, the re-excavation zones of late impact craters larger than tens of kilometer in diameter inside basins may provide the highest abundances of melt from early basins.
•Impact gardening of basin melt modeled in 3D to estimate present surface abundance•Estimate relative abundances of differently-aged melt at Apollo/Luna sampling sites•Surface melt abundance strongly affected by nearby late-forming basins•Deficiency of ancient melt compared to aggregated K-Ar sample age distribution
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The timeline of volcanic activity is critical for constraining the thermal evolution of the Moon. The spatial extents of mare basalts, major products of lunar volcanism, have been precisely extracted ...from LROC (Lunar Reconnaissance Orbiter Camera) image mosaics. With the maria extents newly extracted from LROC mosaics, we found that a large area of mare basalts in the junction of Oceanus Procellarum, Mare Imbrium, Mare Insularum, and Mare Vaporum (the PIV region) has not yet been dated. This study analysed the chronology, composition, and mineralogy of the PIV region, aiming to finish the picture of basaltic volcanism in the Procellarum region, which is a key puzzle of our global geological mapping of the Moon. According to the topographical, spectral, and compositional characteristics, mare units of the PIV region are defined, and the crater size frequency distribution is measured. The primary craters with diameters >0.1 km in the PIV region are measured, and the absolute model ages of basalt units between ∼3.78 Ga and ∼1.71 Ga are derived. Most western PIV basalt units are Eratosthenian-aged, while eastern units mostly formed in the Imbrian period. The spectra of 4965 small impact craters are extracted to interpret the mineral compositions of the PIV basalt units using Chandrayaan-1 Moon Mineralogy Mapper data. Using a Modified Gaussian Model, the reflectance spectra are deconvoluted, and the obtained modal proportions of mafic minerals show low olivine and high low-Ca pyroxene abundances in the eastern PIV region, while the western region features high olivine and calcic pyroxene concentrations. Three episodes of volcanic events occurring in the PIV region are identified. The first (main) occurred at approximately 3.5 Ga (Late Imbrian), with erupted lava flows with less evolved compositions covering most of the PIV area. The peak of volcanic activity in the Eratosthenian period occurred around 2.5 Ga, where mare basalts with moderately evolved compositions and mineralogy were formed. The last major eruption occurred at approximately 1.8 Ga, forming mare basalts with highly evolved compositions.
•Basaltic volcanism chronology of undated unit in Procellarum region was determined.•Three volcanic episodes identified in the PIV region reveal magmatic evolution.•The western PIV region has more evolved compositions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Lunar mare regolith is traditionally thought to have formed by impact bombardment of newly emplaced coherent solidified basaltic lava. We use new models for initial emplacement of basalt magma to ...predict and map out thicknesses, surface topographies and internal structures of the fresh lava flows, and pyroclastic deposits that form the lunar mare regolith parent rock, or protolith. The range of basaltic eruption types produce widely varying initial conditions for regolith protolith, including (1) autoregolith, a fragmental meter‐thick surface deposit that forms upon eruption and mimics impact‐generated regolith in physical properties, (2) lava flows with significant near‐surface vesicularity and macroporosity, (3) magmatic foams, and (4) dense, vesicle‐poor flows. Each protolith has important implications for the subsequent growth, maturation, and regional variability of regolith deposits, suggesting wide spatial variations in the properties and thickness of regolith of similar age. Regolith may thus provide key insights into mare basalt protolith and its mode of emplacement.
Plain Language Summary
Following recent studies of how lava eruptions are emplaced on the lunar surface, we show that solid basalt is only one of a wide range of starting conditions in the process of forming lunar soil (regolith). Gas present in the lavas during eruption also produced bubbles, foams, and explosive products, disrupting the lava and forming other starting conditions for mare soil parent material.
Key Points
New basalt magma emplacement models explore fresh lava flows that form the lunar mare regolith parent rock, or protolith
Some conditions predict immediate formation of a fragmental meter‐thick “autoregolith” that mimics impact‐generated regolith
Lava flows with significant near‐surface vesicularity, macroporosity, and magmatic foams will create nontraditional regolith growth rates
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Impact basins are primary geological structures on the Moon, and play key roles in revealing the lunar history. Due to the different identification standards currently used, the basin identification ...results are highly inconsistent. Except for the major basins (e.g., Orientale, Schrödinger, Imbrium, Crisium, Apollo, and Nectaris Basin), detailed sub-formation interpretations for most other basins are lacking, which hampers the construction of a complete (global) geological interpretation for the lunar impact basins. Based on multisource remote sensing data and previous works, we established a basin identification standard, and a new global lunar basin catalog containing 81 basins. According to the ring diameter ratios, the purest anorthosite (PAN) distribution, and basin radial textures, we divided the basin sub-formations into the central-peak, peak-ring, basin-floor, basin-wall, basin-rim, and basin-ejecta formations. We interpreted the ejecta formation and other basin sub-formations by combining the Focal Flow data with LROC WAC images, topographic data, gravity anomalies, and spectral data. Our new lunar geologic map shows more precise distribution of basin formations, covering nearly 70% of the lunar surface. Moreover, we obtained the origin of basin rings using basin sub-formations map. Additionally, the basin sub-formation map can contribute to the basin impact conditions, such as the discovered ring (concentric with the outermost ring) provides evidence for three impacts in the Mare Moscoviense, and the SPA sub-formation distribution indicates the impact direction of SPA is SE-NW. Furthermore, the sub-formation distribution can facilitate the geological characteristics and evolution study of the lunar exploration sites.
•Impact basin identifying standard and new global lunar basin catalog established.•Basin sub-formations divided based on ring ratio, PAN distribution, and basin radial textures.•Focal Flow data first used to interpret sub-formation, improving map resolution.•A more accurate distribution map of lunar basin formations is produced.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The lunar crater chronology has been built by connecting radiometric ages of sampled terrains with the areal crater densities on those terrains, particularly the density at diameters (D) ≥ 1 km (aka ...N(>1)). In the past, very few crater chronologies have considered the effect of terrain properties on the crater densities and size-frequency distributions (SFDs) used to build them. This influence is especially important when N(>1) cannot be directly measured. Here we study this influence by using the Model Production Function (MPF) chronology, which incorporates terrain properties into computing N(>1) and absolute model ages (AMAs) through computing crater diameters using standard crater scaling laws. Furthermore, we also gain a better understanding of actual lunar terrain properties by adjusting the MPF to reproduce AMAs close to the radiometric ages of several Apollo sample sites. The properties examined are the consolidation state of the terrain, its effective cratering strength, and density. Overall, we find that the impact melt of Copernicus crater (∼0.8 Ga) is stronger and more consolidated than the mare and highland terrains investigated. The mare become less consolidated and weaker as they age (from 3.1 to 3.8 Ga) – likely due to fracturing and regolith formation by subsequent impacts. The highlands (∼3.8 Ga) are the weakest terrain. The analysis of terrain proprieties allows our MPF computations to reproduce the radiometric ages, and the impact melt and ejecta of Copernicus crater to have the same age, as expected. The new lunar terrain property constraints can be used with the MPF to derive more robust absolute model ages for unsampled terrains. The values presented in this work for impact melt, ejecta, mare, and highlands can serve as references.
•Model Production Function used to infer how terrain properties affect age derivation.•New constraints on strength terrain properties of Apollo sampling sites are given.•Crater model ages should consider terrain properties, particularly for D < 200 m.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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