Wrinkle Ridges Research Articles

Special Thermophysical Features of Floor Materials in Mare Smythii Indicated by CE-2 CELMS Data

Mare Smythii is a special basin, which is one of the oldest mare basins with the considerably young mare basalts and the high density of floor-fractured craters. In this article, the microwave sounder, named CELMS, onboard Chang'E-2 lunar orbiter was first invested to assess the thermophysical characteristics of the floor materials in mare Smythii. Based on the numerical simulation with the radiative transfer model and the previous geological results, several special findings are noted as follows. First, the substrate temperature in mare Smythii is likely fairly high, and a special temperature structure is provided. Second, there likely exists an unrevealed deposit in the upper layer of the regolith with strong thermal absorption ability. Third, the CELMS results show a strong correlation with the subsurface features obtained by lunar radar sounder data and the surface wrinkle ridges. These findings will be of essential importance to strengthen knowing the thermal and magmatic evolutions of the lunar maria.

The Long‐Lived and Recent Seismicity at the Lunar Orientale Basin: Evidence From Morphology and Formation Ages of Boulder Avalanches, Tectonics, and Seismic Ground Motion

AbstractThe geologic analysis of lunar tectonic and co‐existing mass wasting features provides important insights into seismicity, seismic ground motion, and the seismic risk of the landed missions. Hence, we performed a detailed geologic mapping of tectonic features and co‐seismic boulder avalanches present at the 930‐km‐diameter lunar Orientale basin. We traced 6869 boulder falls at 141 sites along the basin rings, impact crater walls, and volcanic features. The boulder fields also occur on the graben walls and wrinkle ridges. The boulder trail length and width, and slopes of trail and source region of fallen boulders provide insights into formation processes and transport dynamics. Tens of sites have anomalously larger number of boulder falls and trail density. The cumulative size‐frequency distributions of superimposed impact craters present on the boulder trails provided their model formation ages varying between present and 7.5 Ma with at least eight formation episodes, suggesting the timings of seismic activities along the Cordillera and Outer Rook Rings. Many boulder falls are devoid of superimposed impact craters suggesting their recent origins, including some possibly triggered by the 1972 (MW 2.7) shallow moonquake that occurred near the Cordillera Ring. The formation rates of shallow moonquakes and impact craters along with the seismic ground motion simulations suggest that shallow moonquakes are more dominant sources of ground shaking for triggering the boulder falls in the last 30 million years. Therefore, the Orientale basin has been seismically active for long time and it may be seismically hazardous locally for the future landed missions.

Structural interpretation of thrust fault-related landforms on Mercury using Earth analogue fault models

The Yakima Fold Province has often been referenced as an Earth analogue to thrust fault-related landforms on many solar system bodies including Mars, the Moon, and Mercury. The asymmetric ridges of deformed flood basalts in this region evoke the morphology and topographic expression of the landforms observed in the Smooth Plains units of Mercury. Observed similarities have supported the interpretation that thrust faults and folds comprise both sets of landforms; however, this is an incomplete analogy. Recent modeling efforts have revealed that the terrestrial landforms developed over millions of years with vertical uplift associated with each landform accumulating on multiple faults and accommodated by large folds. These studies highlight the important role that folding plays in accommodating crustal shortening. Work presented here uses the structural geometries and folding styles from the Yakima Fold Province as a framework for constructing ten three-dimensional models of thrust fault-related landforms in Smooth Plains units near Suisei Planitia on Mercury, which traditionally would have been classified as “wrinkle ridges” based on appearance and some aspects of morphology. Forward modeling of topography revealed that multiple faults and folds are necessary to reproduce complex topographic features. Folding was found to account for >50% of vertical uplift associated with the landforms and without considering folding, shortening accommodated by the landforms was underestimated by 61 to 88%. Studies which use thrust fault-related landforms as proxies for stress and strain must therefore consider the effect of folding on these estimates and their associated effect on tectonic and thermal histories.

The tectonic architecture of wrinkle ridges on Mars

The geodynamic history of Mars is written largely in the form of its tectonic structures. A global population of compressional structures records a history of interior cooling and contraction, in combination with volcanic loading and flexure of the lithosphere. The most common of these structures are wrinkle ridges, interpreted as having formed by folding of near-surface layered volcanic materials above blind thrust faults. Topographic profiles of wrinkle ridges are found to dominantly fall into three classes: symmetric ridges, arch-style ridges characterized by broad convex upward backlimbs, and double ridges characterized by a broad arch and narrow ridge. A Monte Carlo boundary element model was used to constrain the underlying geometry of faults associated with the different ridge types. Symmetric ridges are pop-up structures formed between quasi-symmetric thrust and backthrust faults, in some cases above a horizontal décollement or low angle fault at depth. Arch-style ridges formed above a dominant primary thrust fault of near constant dip, with a secondary backthrust playing a lesser role in generating subtle inflections in the backlimb. Double ridges require two backthrust faults to localize strain within the narrow ridge at the ridge crest and to generate the secondary antiform on the backlimb. In these ridges, both the upper primary thrust and backthrust are contained within the layered volcanic materials, while the lower portions of the primary thrust can extend deep into the crust or upper mantle. A shallower depth of fault penetration in areas of thicker crust is consistent with the depth of faulting being limited by the brittle-ductile transition. Dips vary widely, but are typically steep in the upper faults and quite gentle in the lower faults. Thus, while wrinkle ridges do provide important records of tectonic and geodynamic processes on Mars as well as other bodies, the associated tectonic structures are more complex and varied than previously considered.

Geology of Grimaldi Basin on the Moon: Evidence for volcanism and tectonism during the Copernican period

The Grimaldi Basin, centered at (5.2° S, 68.6° W), is a ~400 km diameter highly degraded, Pre-Nectarian double-ring impact structure on the Moon located near the western edge of the Oceanus Procellarum. Hyperspectral data from Moon Mineralogy Mapper (M3), FeO estimates from Kaguya Lunar Multiband Imager (MI) data and TiO2 estimates from WAC 321/415 nm ratio have been used to study the compositional make-up of the Grimaldi mare basalt. Additionally, morphological studies and crater chronology have been carried out using moderate to very high-resolution images from Lunar Reconnaissance Orbiter (LRO) to decipher the geological evolution of the Grimaldi Basin. Mare Grimaldi are dominantly composed of clino-pyroxenes with olivine and/or of feldspathic mixing with lateral as well as depth-wise variations in composition. In the south central part, the basin experienced Copernican aged volcanism ~700 Ma ago resulting in the formation of olivine bearing basalts with high FeO and TiO2 content. Cross-cutting of small Copernican craters by fresh wrinkle ridges and lobate scarps has been observed at several places in the basin suggesting that tectonic activities occurred in the basin within the past ~50 Ma-1 Ga. Thus, similar to the Oceanus Procellarum region, Grimaldi Basin was also geologically active during the Copernican period.

A large long-lived central-vent volcano in the Gardner region: Implications for the volcanic history of the nearside of the Moon

Large shield-building volcanic structures (>30 km) with central vents are rare on the Moon. The most popular candidate targets of lunar large shield volcanoes are volcanic complexes on the lunar nearside within the compositionally evolved Procellarum KREEP terrane (PKT). However, there is a unique mass concentrated volcanic complex not within the PKT, namely Gardner (16.1°N, 34.1°E, ∼70 km in diameter) on the northern edge of Mare Tranquillitatis, whose origin is enigmatic. Here we use multi-source remote-sensing data to assess its morphology, composition and stratigraphy to better understand its formation and evolution. Results show that domes, sinuous rilles, and an irregular depression exist in this region. Gardner has experienced four stages of volcanic activities with absolute model ages from 3.90 to 2.96 Ga, contemporaneous with the main volcanic activity periods of the lunar nearside. An area with relatively low albedo, high FeO and TiO2 contents, low rock abundances, and young surface age is identified in the southeast part of the irregular depression at the summit of the plateau, which could have been the result of a long-lived eruptive center. Quasi-circular positive Bouguer-gravity anomaly suggests either sill/laccolith intrusions or large conduit solidifications underneath this area, which could be related to its surrounding radially distributed lava domes, wrinkle ridges and faults. We conclude that Gardner is the largest central-vent volcano identified so far on the Moon, and it provides an essentially new perspective and supplement for the knowledge of the lunar nearside volcanism.

The origin of neotectonics on the lunar nearside

Abstract New observations of wrinkle ridges on the nearside maria of the Moon display signs of ongoing ridge modification. In association with the wrinkle ridges, we observed an absence of superposed craters, narrow (<30 m) lobate scarps and graben, and thermal anomalies related to exposures of meter-size blocks. Many of these active wrinkle ridge systems are well beyond the influence of mascon basins and unrelated to any global tectonic pattern. Nevertheless, they spatially correlate with ancient deep-seated dike intrusions on the lunar nearside revealed by gravity data analysis. We propose that this active nearside tectonic system (ANTS) reflects ongoing reactivation of an ancient system related to offset antipodal effects from the South Pole–Aitken basin.

Long-lived volcanism expressed through mare infilling, domes and IMPs in the Arago region of the Moon

Mare Tranquillitatis corresponds to the deposit of successive Early to Late Imbrian basaltic units filling the Tranquillitatis basin on the Moon. The present study focuses on the western half of the mare, in the vicinity of the Arago crater (6.16°N, 21.42°E). High resolution datasets from recent remote sensing missions were used to reconstruct the geologic history of the area, which includes a variety of geological features such as: 8 extrusive domes, numerous wrinkle ridges, a sinuous rille and 37 Irregular Mare Patches (IMPs). We performed crater counting to date the domes emplacement and estimated the domes lava rheologic properties (plastic viscosities, lava effusion rates, and durations of effusion) using their geometric characteristics. As a result we classify the Arago domes into three groups: E1-type domes (Arago 1 and 8), H1-type domes (Arago 4 to 7), and B-type domes (Arago 2 and 3) respectively emplaced ​~ ​3.7 ​Ga, ~3.4 ​Ga, and ~2.8 ​Ga ago. IMPs are observed in the younger mare unit and on the top of the Arago 6 dome; they likely correspond to a late stage of waning mare volcanism in the area. Both IMPs and domes have a composition similar to the surrounding mare in the VNIR spectral domain, consistent with mafic materials. The exceptionally long-lived volcanism and its diversity recorded in the Arago region may be related to both a Th-rich anomaly reported nearby and to the large-scale magma center responsible for the Lamont positive Bouguer anomaly. In addition, volcanic features of the Arago region are superimposed on a Ti-rich mare unit visited by the Apollo 11 crew 175 ​km to the south at Tranquility Base. The geological and historical richness of this region makes it a compelling site for future science and/or In Situ Resources Utilization (ISRU) driven missions to the Moon.

Automatic detection and characterization of Lunar Wrinkle ridges

Abstract Related computational advances, across various geoscience disciplines, have led to development of an upcoming field: Computers & Geosciences. This multidisciplinary research area is attracting interest of both computer science and planetary/space scientists since last two decades. Under this domain, the most significant area which is gaining importance is application of computational intelligence to automatically extract landforms present on planetary surfaces and determine their morphometric attributes. Wrinkle ridges are one of the common features on lunar surface that need to be explored more for further computation and analysis. This paper focuses on application of image processing approaches for automatic detection of wrinkle ridges and evaluation of morphometric parameters like length, width, orientation and area. The software developed was tested on DEMs (Data Elevation Model) of lunar wrinkle ridges utilizing SLDEM (Selene Lunar Data Elevation Model) data set. The test dataset comprises of 9 lunar wrinkle ridges having 62 segments with a total length of 1414 km. The results were verified by manual calculations using QGIS software. The software was found to perform with a mean percentage deviation varying from 3.10 to 5.97 for different parameters

Provenance of Block Fields Along Lunar Wrinkle Ridges

AbstractBlock fields and associated relatively high reflectance material along wrinkle ridge summits are revealed in meter‐scale Lunar Reconnaissance Orbiter Camera images. Wrinkle ridges with block fields in Mare Australe, Crisium, Fecunditatis, Frigoris, Nubium, the northern half of Oceanus Procellarum, Serenitatis, and Tranquillitatis are evenly distributed, and block density generally increases with wrinkle ridge slope. The median cross‐sectional area (proxy for diameter) of the 1,368 blocks measured in this study is ~7 m2, and 75% of these blocks are ≤~14 m2. We propose that the largest variation in cross‐sectional area of the blocks is related to substrate physical properties of the mare basalt and not a function of the slope on which they occur, suggesting that physical properties rather than slope are a stronger control on block size. The maximum length of blocks may constrain the minimum basalt flow thickness or joint width; our block measurements suggest basalt flows ~2–14 m thick, agreeing with previous estimates. The data suggest that blocks originate from mare basalt layers that buckle and break as a result of movement along ridge‐forming thrust faults. High reflectance material associated with wrinkle ridge blocks likely represents freshly exposed rock and soil. Meter‐scale blocks may erode relatively quickly due to collisional disruption, indicating recent downslope movement of regolith exposing preexisting blocks or blocks formed and exposed by recent activity on ridge‐forming faults.

Dating long thrust systems on Mercury: New clues on the thermal evolution of the planet

The global tectonics of Mercury is dominated by contractional features mainly represented by lobate scarps, high relief ridges, and wrinkle ridges. These structures are the expression of thrust faults and are linear or arcuate features widely distributed on Mercury. Locally, these structures are arranged in long systems characterized by a preferential orientation and non-random spatial distribution. In this work we identified five thrust systems, generally longer than 1000 ​km. They were named after the main structure or crater encompassed by the system as: Thakur, Victoria, Villa Lobos, Al-Hamadhani, and Enterprise. In order to gain clues about their formation, we dated them using the buffered crater counting technique, which can be applied to derive the ages of linear landforms such as faults, ridges and channels. To estimate the absolute age for the end of the thrust system’s activity, we applied both Le Feuvre and Wieczorek Production Function and Neukum Production Functions. Moreover, to further confirm the results obtained with the buffered crater counting method, the classic stratigraphic approach has been adopted, in which a faulted and an unfaulted craters were dated for each system. The results gave consistent ages and suggested that the most movements along major structures all over Mercury most likely ended at about 3.6–3.8 ​Ga. This gives new clues to better understand the tectonics of the planet and, therefore, its thermal evolution. Indeed, the early occurrence of tectonic activity in the planet’s history, well before than predicted by the thermophysical models, coupled with the orientation and spatial distribution of the thrust systems, suggests that other processes beside global contraction, like mantle downwelling or tidal despinning, could have contributed to the first stage of the planet’s history.

AUTOMATED DETECTION OF LUNAR RIDGES BASED ON DEM DATA

Abstract. Wrinkle ridges are a common feature in the lunar maria and record subsequent contraction of mare infill. Automatic detection of wrinkle ridges is challenging because the ridges are of irregular shapes and many ridges have been eroded and/or degraded over time. The proposed method consists of the following steps. First, as the slope can reflect the gradient changes of the ridge rims to a certain extent, the slope map is generated and converted to a grayscale (0–255) image. Then the phase symmetry of the slope map is calculated with filter wavelength and filter scales parameters, which reduce the regions into symmetry regions. Next, a regional threshold is applied to limit the ridge candidates. Candidates with values less than the threshold are rejected. Moreover, the images are processed using a series of morphological operations, such as close, open, edge linking and noise removal. Finally, after thresholding the ridge map can be obtained. An experiment was performed using Lunar Reconnaissance Orbiter Camera (LROC) WAC image and topographic data from LOLA, the results demonstrate promising performance with detection percentage from 73 to 90.

Geology of the Alpha Regio (V-32) Quadrangle, Venus

ABSTRACT We present a 1:2,500,000 geological map of the Alpha Regio (V-32) quadrangle, Venus. The V-32 quadrangle extends from 0° to 25 S, 0°to 30° E with an area of approximately 7,600,000 km2. Geological mapping was conducted using full resolution (maximum 75 m/pixel) SAR, altimetry and stereo-derived topography data from NASA's Magellan mission in ArcGIS 10.5. Nearly 40,000 lineaments were mapped. The oldest unit, tessera terrain, is present in two major regions: Alpha Regio and Minu-Anni Tessera. Two major fracture belts, both oriented approximately NNW-SSE, and four minor fracture belts have been identified and characterized. Two previously unrecognized wrinkle ridge trends of radiating and circumferential orientation have also been identified in the northeastern corner of the quadrangle. A total of 77 geological units were mapped. Plains material, previously mapped as global regional plains units, was divided into 27 units. Earlier estimates of the diameters of several coronae have been extended by hundreds of kilometres.

Wrinkle ridges on Mercury and the Moon within and outside of mascons

Found on all terrestrial planets, wrinkle ridges are anticlines formed by thrust faulting and folding resulting from crustal shortening. The MErcury Surface, Space Environment, Geochemistry, and Ranging (MESSENGER) spacecraft's orbital phase returned high resolution images and topographic data of the previously unimaged northern high latitudes of Mercury where there are large expanses of smooth plains deformed by wrinkle ridges. Concurrently, the Lunar Reconnaissance Orbiter (LRO) is obtaining high resolution images and topographic data covering lunar mare wrinkle ridges. These data allow quantitative comparison of the scale of wrinkle ridges in smooth plains volcanic units on Mercury with mare wrinkle ridges. We evaluate the topographic relief of 300 wrinkle ridges within and outside of mascon basins on the Moon and Mercury. Measured wrinkle ridges range from ~112 to 776 m in relief with a mean of ~350 m (median = ~340 m, n = 150) on Mercury and from ~47 to 678 m in relief with a mean of ~198 m (median = ~168 m, n = 150) on the Moon. Wrinkle ridges on Mercury thus are approximately twice as large in mean relief compared to their counterparts on the Moon. The larger scale of Mercury's wrinkle ridges suggests that their formation can be attributed, in part, to global contraction. As global contraction on the Moon is estimated to be an order of magnitude smaller than on Mercury, the smaller scale of lunar wrinkle ridges suggests they most likely form primarily by load induced subsidence of the mare basalt. Wrinkle ridges located in lunar mascon basins and in the Caloris mascon on Mercury are not statistically significantly different in relief than ridges in non-mascon regions, suggesting comparable levels of contractional strain. The fact that mascon basins do not host wrinkle ridges with greater structural relief relative to non-mascon units may indicate the critical role lithospheric thickness plays in controlling subsidence and contraction of thick volcanic sequences on the Moon and Mercury.

Young wrinkle ridges in Mare Imbrium: Evidence for very recent compressional tectonism

Wrinkle ridges are common landforms widely distributed in the lunar maria. Many young wrinkle ridges were found inside Mare Imbrium using Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) high-resolution images. They represent very recent tectonic activity on the lunar surface. Determining their formation times and morphology is important in understanding the Moon's late evolution. The young ridges were mapped, and they have a winding and arched morphology. Based on their small scale and crisp appearance, crosscutting relations with very young small craters whose youth was concluded from spatial boulder densities within their ejecta blankets, these young wrinkle ridges were estimated to be as young as 10 or a few 10s of Ma, and may still be active today. The young ridges were mainly distributed in the inner region of Imbrium basin, which may suggest that the thermal and structural evolution of the inside area of Imbrium basin was protracted.

Morphological and Chronological Mapping of Manilius Crater Region Using Chandrayaan-1 Data Sets

Fine-resolution morphological mapping aided by ortho-images and digital elevation model from Chandrayaan-1 Terrain Mapping Camera and 3D GIS visualization has revealed scientifically diverse characteristics of lunar surface features, due to unique topographical significance of morphological features, i.e., highlands, basaltic plains and craters, which are very well manifested in 3D GIS environment. The distribution of various morphological features provides insights into the sequential evolution and surface process of the study area. The highland region represented by the Fra Mauro formation in the study area exhibits high albedo with distinct topography. The northern part of the study area falls in the southern part of major basin Serenitatis, and exhibits the dark mantling material with low albedo. The morphological features, i.e., wrinkle ridges and rilles, indicate volcanic flow events consequence to the loading of basaltic materials in the interior of the Serenitatis and Imbrium Basins and related extensional failure. The Manilius crater, which occupies the central part of the study area, is a complex crater with a central peak and asymmetric ejecta deposit. The ages of the major surficial features were determined based on size, frequency and distribution pattern of craters using crater size-frequency distribution model. Age of the Fra Mauro highland, Manilius crater, Mare Serenitatis and Mare Vaporum is, respectively, 3.9, 3.5, 2.8 and 1.7 Ga years, indicating that the lunar surface of this region evolved in Imbrian to Eratosthenian age of lunar selenological timescale.

Evidence for recent and ancient faulting at Mare Frigoris and implications for lunar tectonic evolution

Nearside basin-related extensional tectonism on the Moon was thought to have ended by about 3.6 billion years ago and mare basin-localized contractional deformation ended by about 1.2 billion years ago. Lunar Reconnaissance Orbiter Camera (LROC) high resolution (50–200 cm/pixel) images show the Moon's surface in unprecedented detail and have enabled us to find many previously unidentified tectonic landforms, forcing a re-assessment of our views of tectonism in the maria. The morphology and stratigraphic relationships of these newly identified populations of tectonic landforms imply a more complex and longer-lasting history of deformation. We selected Mare Frigoris as an ideal location to perform a mapping survey where excellent imaging conditions, abundant tectonic landforms, and restricted mascon allow us to unravel the mare's tectonic evolution. Similar to previous surveys, we find that tectonism in the eastern portion of Mare Frigoris was controlled by ancient mascon induced flexure. In the western portion, however, we identify a parallel set of ancient compressional wrinkle ridges across the mare that is inconsistent with an origin by mare basin-centric mascon flexure or influence from the Mare Imbrium mascon. Instead, our results imply an ancient, regional, non-isotropic stress field over western Mare Frigoris. We also identify young wrinkle ridges and show that they have likely been active within the last 1 billion years, and some ridges as recently as within 40 million years. Finally, we identify a 300 km long series of lobate scarps coincident with one of the shallow moonquakes recorded during Apollo and use geodetic strain from the mapped global population of young lobate scarps to predict a level of seismicity consistent with the shallow moonquakes recorded during Apollo. In tandem with similarly young lobate scarps and small graben, as well as recorded shallow moonquakes, these young wrinkle ridges imply that some tectonism in and around Mare Frigoris has occurred in the geologically recent past and likely still continues today.

Polygonal Impact Craters in the Thaumasia Minor, Mars: Role of Pre-existing Faults in Their Formation

Terrestrial planets, dwarf planets and moons (natural satellites) in the solar system have undergone meteoric impacts since their formation. The craters formed due to such impacts may show various geometric shapes. Formation of impact craters that are polygonal in shape is controlled by the presence of pre-existing tectonic features in the area of impact. Thaumasia Minor, the easternmost part of Thaumasia Planum of Mars, has ~ E–W-trending grabens and ~ N–S-trending wrinkle ridges, similar to the rest of Thaumasia Planum. The massive weight of the Tharsis Montes, lying to the northwest of Thaumasia, is considered as the primary cause for the extensional and compressional fractures developed in multiple temporal phases throughout the geological history of Mars. Five such polygonal impact craters in the southern Thaumasia Minor were compared with the visible expressions of tectonic planes in the region. The straight segments of the craters are also used as a proxy to reveal the presence and possible orientations of buried weak planes in the region.

Tectonic patterns of shortening landforms in Mercury's northern smooth plains

Mercury's northern smooth plains are volcanically emplaced units characterized by ghost craters, volcanically buried impact basins, and thrust fault-related landforms. We analyzed the thrust fault-related landforms, traditionally categorized as lobate scarps and wrinkle ridges, within the northern plains in order to describe trends in how these landforms are organized and oriented and what style of deformation (either thin or thick-skinned) their map patterns represent. Our analysis also establishes geologic constraints for which global processes may have produced stresses contributing to these tectonic patterns. We mapped 4853 thrust fault-related landforms in the northern plains at a map scale of 1:1,000,000 using three MErcury Surface, Space, ENvironment, GEochemistry, and Ranging (MESSENGER) global monochrome mosaics. These landforms, described as curvi-linear asymmetric ridges, frequently occur in complex geometrical arrangements that are interpreted to share similar structural characteristics. We called these arrangements “compound landforms”. Like prior studies, we observed thrust faults to follow rims of buried craters. We also observed (1) sigmoidal rises bounded by fault-related landforms, (2) V-shaped rises composed of two landforms terminating at a single sharp point, (3) broad arcuate rises of nearly equal width, (4) parallel, evenly-spaced ridges, and (5) landforms showing alternation in direction of tectonic transport along strike. Respectively, we interpreted these landforms as transpressional uplifts, faults with sharply juxtaposing ramps, pop-up structures, fold and thrust belts, and antithetic fault intersections. By comparison with Earth analogues and patterns produced in numerical and physical models, our results suggest that deformation in the NSPs is thin-skinned. Orientation analysis showed that the northernmost landforms (90°–70°N) were predominantly oriented east–west while most of the landforms between 50° and 30°N were oriented north–south. Variations in orientation with latitude indicate that the growth of thrust fault-related landforms was influenced by sources of stress other than global contraction. If reorientation of the pole due to the formation of the Caloris basin impact did occur, the pattern of fault orientations indicates that geologic processes producing the pattern operated after reorientation.

Morphometric and rheological study of lunar domes of Marius Hills volcanic complex region using Chandrayaan-1 and recent datasets

Marius Hills volcanic complex is one of the most important regions on the lunar surface having an abundant number of volcanic features like domes and cones. Systematic mapping of 106 domes/cones in the Marius Hills region was carried out in this study using high-resolution orthoimage and digital elevation models of Chandrayaan-1 and Kaguya missions. Various morphometric parameters like diameter, height, volume, flank slope, circularity index and form factor are derived for all the mapped domes. The rheological parameters, such as viscosity and eruption rate are estimated for isolated domes and cones superimposed over low domes. The morphometric and rheological properties of these domes are comparable to those located in the area near to Hortensius crater and other mare regions. Surface ages derived for a selected region in NW portion of the Marius Hills volcanic complex using crater size-frequency distribution technique yields ages of 2.98 and 1.91 Ga. It suggests that the domes in this region formed at about 2.98 Ga ago, and then, the younger mare basalts likely embayed this region about 1.98 Ga ago. Stratigraphic sequence of rilles, wrinkle ridge and domes shows that wrinkle ridges are the oldest, while the rilles are younger than the domes.