Wrinkle Ridges Research Articles

Morphological and Structural Characterization of Shortening Landforms on Mars

AbstractThe lithosphere of Mars accommodates horizontal shortening through folding and faulting, producing landforms described as wrinkle ridges or lobate scarps. Despite this nomenclature, we lack a deep understanding of the drivers of morphological differences observed between landform types. This study aims to develop a quantitative model for shortening landform classification based on surface morphology, subsurface architecture, and strain accommodation, facilitating interpretations of where and how lithospheric stresses are recorded. We developed this model by mapping 100 shortening landforms in a Geographic Information System, recording 12 unique geomorphic parameters such as length and asymmetry, and estimating the strain of each landform. We conducted a Discriminant Function Analysis (DFA) using surface morphometrics. This DFA produced a predictive linear function for categorizing wrinkle ridges and lobate scarps and for quantifying which landforms were exemplars within those categories. The three most influential variables on the surface morphometry DFA were the maximum width, forelimb slope, and back limb length. We then modeled the subsurface structural geology of 50 landforms using MOVE Structural Geology Modeling Software and conducted a second DFA based on subsurface metrics. DFA was most influenced by the dip and depth of the lower ramp base. When both surface morphology and subsurface geometry are input into single DFA, wrinkle ridges and lobate scarps can be distinguished quantitatively 96% of the time. Our results also show that lobate scarps accommodate more strain and imply that studies should consider landform type when interpreting local, regional, and global geological stress histories.

Morphometry and kinematics correlation of wrinkle ridges on Mars: Insights from Trishear modelling

Wrinkle ridges are among the most common and controversial compressional tectonic structures on terrestrial planets. While their origins are well inferred to be related to crustal shortening driven by compressional stress, their subsurface characterization is still a matter of debate. Open questions remain about the geometry, number, structural style and kinematics of faults promoting wrinkle ridges. We use the Trishear and Fault-Parallel-Flow integrated forward kinematic modelling to model wrinkle ridges related faults. This is achieved through a series of balanced cross sections and a consequent set of narrow 3D models. We perform a detail kinematic analysis on nine wrinkle ridges: six are located in the circum-Tharsis regions of Lunae Planum and Solis Planum, while three are located in the Hellas Planitia, Hesperia Planum and Syrtis Major Planum, respectively. The applied methodology allows us to quantitatively assess wrinkle ridges geometry and kinematics, and to correlate them with morphometric parameters (i.e., width and relief). Our results indicate how wrinkle ridges tectonics can be characterized by a more complex array of faults than previously modelled. This leads to a total amount of horizontal shortening accommodated differently depending on the number and type of faults (i.e., main fault, backthrust, synthetic faults). The location and geometry of the modelled faults suggest the presence of multiple detachments at different depths and with different mechanical behaviors such as weaker and more frictional décollements, which are likely found within sedimentary interlayers. The amount of shortening, the fault geometry and spacing, as well as the upper faults tips depth are positively correlated with major morphometric parameters of wrinkle ridges topography.

Structural control on formation of polygonal rims of impact craters in Thaumasia Minor, Mars

It has been known for almost a century that the surfaces of rocky planets contain polygonal-shaped, circular, or elliptical craters. Researchers have hypothesized that pre-existing structurally weak planes, such as faults or fractures, in the vicinity of the impact, are responsible for polygonal patterns of the crater rims. Thaumasia Minor, Mars, which is a heavily deformed late-Noachian terrain with craters of various morphologies, including polygonal impact craters (PICs), is the present area of study to understand the geological control behind the polygonal shapes of the crater rims. A population of 45 carefully chosen polygonal craters are mapped and compared with morphotectonic structures such as graben, wrinkle ridges, and dykes. To discern the relationship between the features, the study uses trends, statistical and spatial analyses of orientation data, and other parameters such as crater diameter and crater excavation depth. Also, to understand the factors affecting PIC formation, 12 earlier studied craters in East Coprates Planum, a region adjacent to the Thaumasia Minor, are studied again. The study proposes two possible geological controls on PIC formation. The study also suggests that graben have more control over smaller PICs while larger PICs are controlled by wrinkle ridges.

Deformation of the Gruithuisen region lava tube under compressional stress on the Moon

The lava tube in the Gruithuisen region on the Moon is intriguing because it is characterized by a distinctive chain of collapsed pits and raised features, providing an opportunity to understand the potential morphologic deformation of lunar lava tubes under compressional stress. This study aimed to understand the morphological deformation in the Gruithuisen region’s lava tube when subjected to compressional stress. A combination of numerical simulations and morphometric analysis was employed to achieve this objective. The morphometric analysis of different collapsed and raised features associated with a lava tube in the study area revealed eight characteristic morphologies ranging from curvilinear channel-like to elliptical shape. Notably, average normal stress and strain values derived from a wrinkle ridge were found to be ∼70 MPa and 2 × 10−3, respectively, and wrinkle ridges exhibited a northward orientation. These quantified parameters were utilized as the foundation for initializing three-dimensional models. Furthermore, the outcomes of the models closely replicated the deformation in the Gruithuisen region, emphasizing the significant role of compressional stress in the deformation of the lava tube. These models suggest that the observed eight unique features associated with the lava tube arise from disparities in displacement magnitude and direction along three axes (x, y, z). Our research sheds light on the structural transformations of lava tubes when subjected to varying compressional stress and enhances understanding of the ways in which the interplay between compressional tectonic activity and lava tube features has shaped the Moon’s surface.

Contractional strains and maximum displacement-length ratios of lunar wrinkle ridges in four Maria of basalt

Compressional stresses from the basalt basins on the lunar are responsible for the formation of wrinkle ridges in lunar mare basalts. According to the wide angle multispectral camera (WAC) mosaic image, we selected 62, 75, 73, and 58 single wrinkle ridges in Mare Imbrium, Mare Serenitatis, Mare Fecunditatis, and Mare Tranquillitatis, respectively, for this paper. Several topographic profiles near the midpoint of each wrinkle ridge are generated to measure the maximum displacement (Dmax) and height of the wrinkle ridges using digital elevation model (LOLA) data. After that, we create 2D plots of displacement-length (L) for the ridge population in the four Maria and compare the results. A linear fit method derives the Dmax/L ratios (γ) from the D-L data. We calculated the contractional strains in each mare area based on the cap D sub m a. x over cap L data. Moreover, each mare's gravity pattern, mare thickness, and formation age are also presented. The ridges in Mare Imbrium and Mare Serenitatis have a higher γ value (1.83 × 10−2 and 1.98 × 10−2) than the ridges in Mare Fecunditatis and Mare Tranquillitatis, which have γ values of (1.67 × 10−2 and 1.75 × 10−2). Finally, the contractional strains (ε) in Mare Imbrium, Mare Serenitatis, Mare Fecunditatis, and Mare Tranquillitatis are estimated to be 0.23 %, 0.41 %, 0.39 %, and 0.18 % (considering 25° is the fault plane dip θ), respectively. The maximum values of the free-air gravity anomalies in Mare Fecunditatis range from −30 to 250 mGal, while minimum gravity anomalies in Mare Serenitatis range from −80 to 140 mGal. Mare Imbrium, Mare Serenitatis, Mare Fecunditatis, and Mare Tranquillitatis have an average thickness of 300 m, 910 m, 652 m, and 760 m, respectively. Furthermore, the Mare Imbrium ridge group is older than the Lunar Wrinkle Ridges in Mare Serenitatis. Mare Tranquillitatis ridge group formation takes longer than Mare Imbrium ridge group formation. Therefore, we believe that it has thicker basaltic units, a longer wrinkle ridge formation time, and higher gravity anomaly than the Mare Imbrium and Mare Serenitatis basins, even though the formation of the Mare Tranquillitatis and Mare Fecunditatis basins occurred earlier.

Detecting Lunar Linear Structures Based on Multimodal Semantic Segmentation: The Case of Sinuous Rilles

Tectonic features on the Moon can reflect the state of stress during the formation of the structure, and sinuous rilles can provide further insight into the tectonic-thermal evolution of the Moon. Manual visual interpretation is the primary method for extracting these linear structures due to their complex morphology. However, extracting these features from the vast amount of lunar remote sensing data requires significant time and effort from researchers, especially for small-scale tectonic features, such as wrinkle ridges, lobate scarps, and high-relief ridges. In order to enhance the efficiency of linear structure detection, this paper conducts research on the automatic detection method of linear structures using sinuous rilles as an example case. In this paper, a multimodal semantic segmentation method, “Sinuous Rille Network (SR-Net)”, for detecting sinuous rilles is proposed based on DeepLabv3+. This method combines advanced techniques such as ECA-ResNet and dynamic feature fusion. Compared to other networks, such as PSPNet, ResUNet, and DeepLabv3+, SR-Net demonstrates superior precision (95.20%) and recall (92.18%) on the multimodal sinuous rille test set. The trained SR-Net was applied in detecting lunar sinuous rilles within the range of 60°S to 60°N latitude. A new catalogue of sinuous rilles was generated based on the results of the detection process. The methodology proposed in this paper is not confined to the detection of sinuous rilles; with further improvements, it can be extended to the detection of other linear structures.

A statistical evaluation of the morphological variability of shortening landforms on Mercury

Observations of Mercury from both the Mariner 10 and MESSENGER missions showed that Mercury has a global population of shortening landforms, with several thousands of individual structures identified to date. The accommodation of widespread tectonic shortening is widely regarded to be the result of global contraction—the long, sustained cooling of the interior that has caused the planet to shrink. Shortening landforms on Mercury have been traditionally categorized into three distinct categories: lobate scarps, wrinkle ridges, and high-relief ridges. Although the clearest examples of shortening landforms at the time were used to describe and define these categories qualitatively, later studies showed that shortening landforms on Mercury display morphological characteristics that do not make for a ready classification into one of these “traditional” groups. More recently, other studies have classified shortening landforms based on the terrain that those landforms reside in to avoid generalizing morphology. In this study, we quantitatively assess the shape of shortening landforms by measuring and compiling a suite of 12 morphological parameters for 100 such structures across the planet. These parameters were evaluated for their importance in defining categories using two multivariate statistical analyses, a Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA). These methods allow us to assess any correlation that the traditional categories, terrain types, or alternative classification schemes have with the variation observed across our set of measurements. Our results show that the morphologic characteristics of shortening landforms on Mercury are not accurately captured by traditionally recognized groups. Instead, shortening landforms fall along a morphological spectrum, where only a few ideal examples of lobate scarps or wrinkle ridges provide clear endmembers. Therefore, despite the frequent use of the terms “lobate scarps” and “wrinkle ridges” in works regarding planetary tectonics, we find that such terminology does not appropriately define the morphology of shortening landforms found on Mercury and may lead to the generalization, or misinterpretation of landforms described as accommodating shortening on Mercury's surface. Future studies should test if a distinction between the landforms is found in the underlying thrust fault systems.

Lunar Boulder Fields as Indicators of Recent Tectonic Activity

Wrinkle ridges are the predominant tectonic structure on the nearside lunar maria. Although lunar wrinkle ridge formation began as early as ∼3.9–4.0 Ga, recent investigations have identified wrinkle ridges in the lunar maria that were tectonically active as recently as the Copernican period of lunar geologic history. Some of those geologically young wrinkle ridges were identified by the presence of dense fields of meter-scale boulders on their scarps and topographic crests. Other investigations have identified recently active lunar wrinkle ridges that lack the ubiquitous presence of boulder fields, thereby rendering the presence of boulder fields ambiguous in the search for ongoing tectonic activity on the Moon. Here we assess boulder populations associated with 1116 wrinkle ridge segments on the lunar maria that are inferred to be recently active (<1.5 Ga) based on their crisp morphologies and crosscutting relationships with small impact craters. We utilize data from the Lunar Reconnaissance Orbiter Mini-RF and Diviner Lunar Radiometer Experiment instruments to assess surface rock populations across these recently active structures. Our results indicate that, where present, meter-scale boulder fields are likely indicators of fault-slip-induced ground acceleration given the short lifespan of lunar surface boulders. However, elevated boulder populations are not observed on all recently active ridges analyzed here. This latter observation supports the notion that wrinkle ridge boulder fields are a nonunique indicator of recent tectonic activity. Furthermore, the spatial distribution of those boulder fields indicates that variable mare protolith properties may play a role in boulder field formation.

Geomorphology, Mineralogy, and Chronology of Mare Basalts in the Oceanus Procellarum Region

Mare basalts on the lunar surface are tangible expressions of the complex thermal evolution and geological processes that have occurred within the lunar interior. These basaltic manifestations are highly important because they provide invaluable insights into lunar geological evolution. Notably, the Oceanus Procellarum region, which is renowned for its extensive and long-lasting basaltic volcanism, is a premier location to investigate late-stage lunar thermal evolution. The primary aim of this research is to elucidate the geomorphological, compositional, and temporal attributes that define the mare basalts within the Oceanus Procellarum region. To achieve this aim, we comprehensively analyzed the geomorphological features present within the region, leveraging Kaguya/SELENE TC images and digital elevation models. Specifically, these geomorphological features encompass impact craters, wrinkle ridges, sinuous rilles, and volcanic domes. Subsequently, we thoroughly examined the mineralogical attributes of basalts in the Oceanus Procellarum region, leveraging Kaguya/SELENE MI data and compositional map products. To more accurately reflect the actual ages of the mare basalts in the Oceanus Procellarum region, we carefully delineated the geological units within the area and employed the latest crater size-frequency distribution (CSFD) technique to precisely determine their ages. This refined approach allowed for a more comprehensive and accurate understanding of the basaltic rocks in the study area. Overall, our comprehensive study included an in-depth analysis of the volcanic activity and evolution of the Oceanus Procellarum region, along with an examination of the correlation between the mineralogical composition and ages of mare basalts. The findings from this exhaustive investigation reveal a definitive age range for basalt units within the Oceanus Procellarum region from approximately 3.69 Ga to 1.17 Ga. Moreover, the latest mare basalts that formed were pinpointed north of the Aristarchus crater. Significantly, the region has experienced at least five distinct volcanic events, occurring approximately 3.40 Ga, 2.92 Ga, 2.39 Ga, 2.07 Ga, and 1.43 Ga, leading to the formation of multiple basalt units characterized by their unique mineral compositions and elemental abundances. Through the application of remote sensing mineralogical analysis, three primary basalt types were identified: low-titanium, very-low-titanium, and intermediate-titanium basalt. Notably, the younger basalt units exhibit an elevated titanium proportion, indicative of progressive olivine enrichment. Consequently, these younger basalt units exhibit more intricate and complex mineral compositions, offering valuable insights into the dynamic geological processes shaping the lunar surface.

Unraveling the Tectonic History of the Tharsis Rise on Mars: Plume Migration and Critical Taper Dome

AbstractWrinkle ridges are widespread tectonic landforms that serve as paleo‐strain and paleo‐stress indicators of the compressional history and thermal evolution of Mars. To reconstruct the center of the Tharsis rise and its migration with time, we mapped wrinkle ridges in the periphery of the dome and analyzed 34,741 wrinkle ridge segments with a total length of 77,294 km. We determined the deviation of each wrinkle ridge segment from a concentric strike direction for systematically changing centers. A fitting procedure indicates that all wrinkle ridge segments can be allocated with good precision to five different stress centers (C1‐5) within the Tharsis rise: the southern edge of the Alba Mons caldera (C1), Ceraunius Fossae (C2), between Ulysses Patera and Pavonis Chasma (C3), Phoenicis Lacus (C4), and Claritas Rupes (C5). We performed a morphometric analysis of each wrinkle ridge and calculated the amount of shortening and depth of detachment, making use of methods for constructing balanced cross‐sections. The amount of horizontal shortening varies from 1.5 to 3.8 km and the range of the detachment depth was found to be between 2.9 and 8.8 km, with significant variance forming an acute wedge of 1.2°–2.2°. Based on the critical taper theory, we inferred a very low basal friction coefficient ranging from 0.077 to 0.093 across the detachments for the five centers (C1–C5). Our findings suggest that these detachments are either localized along salt or clay layers or occur where liquid water is dominant below an impermeable permafrost layer.

Analysis and mapping of lunar wrinkle ridges (LWRs) using automated LWRs detection process with LROC-WAC and LOLA data

Maps of lunar wrinkle ridges (LWRs) were created from 70°N to 70°S and 140°E to 140°W (extracted and highlighted the major LWRs area) using automated LWRs detection process with Lunar Reconnaissance Orbiter Camera wide range angle camera and Lunar Orbiter Laser Altimeter data. Automatic detection of LWRs is challenging because the ridges are of irregular shapes and many ridges have been eroded and/or degraded over time. It’s a preliminary study of automated ridge detection from DEM data. Statistics and measurements of the extracted LWRs, including orientation, extent, length, height, and elevation offset, were performed based on the mapping of lunar ridges. The identified ridges were classified based on their orientation, distribution, direction, and each class were further divided over basalts, and nearby highlands. According to the findings, 3,375 segments with a total length of 26,455.01 km were identified, and the average elevation offset, width, and height of all the wrinkle ridges were 40.39 m, 3.47 km, and 0.29 km respectively after weighting by length. The LWRs were divided into three morphologies and distributions: parallel ridges, isolated ridges, and concentric ridges. The vast majority of LWRs were found in basalts area, with an extension into neighboring highland. The relations between the morphological parameters were further quantitatively analyzed, and a similar linear correlation between the width and height was found in each class of lunar ridges, implying that small and large ridges were formed as a continuum and that the three classes of ridges were probably formed by some common processes. Finally, the relations between the lunar wrinkle ridges and other geomorphic phenomena were analyzed, indicating that purely volcanic origin or buried premare structures are difficult to reconcile with the investigation. In addition, the consistency between the occurrence of the lunar wrinkle ridges and the thickness of lunar maria indicates that the formation of lunar wrinkle ridges is closely related to the lunar maria; nevertheless, the statistical NW direction of individual classes of LWRs also proposes the presence of an appropriate stress field during the process of their formation.

LineaMapper: A deep learning-powered tool for mapping linear surface features on Europa

As discontinuities of the smooth icy surface, linear surface features might be directly or indirectly linked to Europa’s subsurface ocean. Mapping and categorising Europa’s lineaments is a means of retrieving information that could be linked to their formation history. As of today, planetary mapping is mainly conducted manually, which is tedious and subject to human bias once data sets become large. Mapping is further complicated by the heterogeneous quality and coverage of the available image data.Here, we train LineaMapper, a convolutional neural network (Mask R-CNN), to conduct instance segmentation of the four main units of linear surface features on Europa: bands, double ridges, ridge complexes and undifferentiated lineae. LineaMapper is trained on the basis of 15 mosaics from the Galileo solid-state imager data, yielding 930 training tiles. With LineaMapper, we provide a new method that facilitates detailed mapping of lineaments in Galileo images. LineaMapper could be applied to data to be returned by the Europa Imaging System (EIS) onboard the Europa Clipper mission. We validate LineaMapper v1.0 on an independent test set. On this test set, LineaMapper shows an overall higher precision than recall. In other words, there are more non-detections of actual lineaments than there are false detections of lineaments. The model shows the most correct predictions for double ridges (highest precision), while the most complete detections happen for ridge complexes (highest recall), compared with the ground truth. In some cases, LineaMapper preserves the cross-cutting relationships. The biggest strength of LineaMapper lies in its speed and tunable output. In the future, LineaMapper can be retrained, fine tuned and applied to similar looking features, for example wrinkle ridges on Venus, ridges on other planets and moons or even dust devil tracks on Mars.

Estimated seismicity of Venusian wrinkle ridges based on fault scaling relationships

Venus' young surface age implies significant geologic activity. Several lines of evidence suggest current volcanism, but there is no data to directly constrain current tectonism. Wrinkle ridges are an abundant, globally distributed fault type, and may have formed relatively recently. We estimate seismicity using a scaling relationship between fault length and moment release. We obtain fault lengths from previously mapped wrinkle ridges and limit their lengths in two ways: (1) with realistic vertical slip extents (VSEs) of 50, 30, and 10 km, and (2) with four tiers of segmentation. A VSE limits fault dimensions and is constrained by faulting depth, and segmentation is important to produce a realistic magnitude-frequency distribution. We use 100 million years as a deformation time to calculate annual seismicity for the wrinkle ridges. Resulting moment release rates are 5.1×1017 N⋅m/yr, 3.7×1017 N⋅m/yr, and 9.1×1016 N⋅m/yr for fault VSEs of 50 km, 30 km, and 10 km, respectively. We predict seismicity roughly 1 order of magnitude more than the extrapolated Mars global seismicity from measurements at a single station, and ∼5 orders of magnitude less seismicity than is observed on Earth. This estimate is conservative since we assume each segment breaks once and the faults are mapped using low resolution global data. Moreover, Venus exhibits many other likely sources of seismicity, including volcanoes, ridge belts, graben, and other faults. Wrinkle ridges and other features likely produce quake magnitudes detectable through infrasound using a balloon-based barometer.

Morphostructural mapping of Borealis Planitia, Mercury

ABSTRACT Orbital data from the MESSENGER spacecraft show that a significant portion of Mercury’s northern hemisphere is covered by smooth plains, which are interpreted to be flood volcanic material and/or impact melt. The smooth plains show pervasive tectonic structures and encompass a broad raised bulge of uncertain geophysical interpretation. In this work, we focus on the mapping of all the morphostructures within the northern smooth plains, aiming at providing a useful dataset for further studies about the mapped area. The structural map is obtained through a twofold process: first with an automatic mapping, using an algorithm to identify all the lineaments from a DEM; and second with a visual inspection and classification of the results of the algorithm in a GIS environment. The final maps are drafted at two different scales, 1:300,000 and 1:600,000. With this approach, we mapped and characterized more than fifty thousand lines marking scarps on the surface, creating a database with several morphometric attributes for each of the identified scarps (e.g. length, azimuth, and height), which can be used for geostatistical study of smooth plains tectonics. Our structural map reveals that: (i) the area is broadly dominated by wrinkle ridges, ghost crater assemblages of lineaments, and scarps related to impact crater processes (e.g. radial faults, secondary crater chains, ejecta emplacement) and that (ii) the amount of strain was not evenly accommodated throughout the northern smooth plains.

Evidence for structural control of mare volcanism in lunar compressional tectonic settings

One of the long-standing enigmas for lunar tectonic-thermal evolution is the spatiotemporal association of contractional wrinkle ridges and basaltic volcanism in a compressional regime. Here, we show that most of the 30 investigated volcanic (eruptive) centers are linked to contractional wrinkle ridges developed above preexisting basin basement-involved ring/rim normal faults. Based on the tectonic patterns associated with the basin formation and mass loading and considering that during the subsequent compression the stress was not purely isotropic, we hypothesize that tectonic inversion produced not only thrust faults but also reactivated structures with strike-slip and even extensional components, thus providing a valid mechanism for magma transport through fault planes during ridge faulting and folding of basaltic layers. Our findings suggest that lunar syn-tectonic mare emplacement along reactivated inherited faults provides important records of basin-scale structure-involved volcanism, which is more complex than previously considered.

The history of global strain and geodynamics on Mars

The tectonic record of Mars is dominated by compressional wrinkle ridges on volcanic surfaces, and these structures have been widely used as a record of tectonic and geodynamic evolution. This study analyzes the density of compressional tectonic structures and inferred strain as functions of time, using the lengths and heights of compressional ridges together with geologic estimates of surface age. Our analyses confirm an apparent peak in compressional strain in the late Noachian and early Hesperian, and comparatively lower values before and after. The lower tectonic strain in the early and middle Noachian relative to the early Hesperian reflects the incompleteness of the ancient compressional tectonic record of strain, as older surfaces should accumulate more strain than younger surfaces. This strain deficit necessitates other means of accommodating contractional strain in the ancient crust, including distributed strain and small-scale faulting. The abrupt decrease in the accumulated tectonic strain and strain rate after the early Hesperian reflects a rapid episode of global contraction followed by much lower rates, in conflict with models of steady-state mantle evolution. The decreasing strain rate may be explained by a changing mantle rheology due to volcanic outgassing. Alternatively, the strain history may be explained by the dominance of mantle plumes in the late Noachian and early Hesperian associated with the formation of Tharsis and the early Hesperian volcanic provinces, which could have led to a pulse of rapid contraction caused by disequilibrium cooling and volcanic outpourings. The tectonic record of strain on Mars – including the incomplete ancient record and evidence for strong departures from steady-state models – may have implications for the interpretation of the tectonic record and thermal evolution of other bodies as well.

Timing and Origin of Compressional Tectonism in Mare Tranquillitatis

AbstractThe lithosphere of the Moon has been deformed by tectonic processes for at least 4 billion years, resulting in a variety of tectonic surface features. Extensional large lunar graben formed during an early phase of net thermal expansion before 3.6 Ga. With the emplacement of mare basalts at ∼3.9–4.0 Ga, faulting and folding of the mare basalts initiated, and wrinkle ridges formed. Lunar wrinkle ridges exclusively occur within the lunar Maria and are thought to be the result of superisostatic loading by dense mare basalts. Since 3.6 Ga, the Moon is in a thermal state of net contraction, which led to the global formation of small lobate thrust faults called lobate scarps. Hence, lunar tectonism recorded changes in the global and regional stress fields and is therefore an important archive for the thermal evolution of the Moon. Here, we mapped tectonic features in the non‐mascon basin Mare Tranquillitatis and classified these features according to their respective erosional states. This classification aims to provide new insights into the timing of lunar tectonism and the associated stress fields. We found a wide time range of tectonic activity, ranging from ancient to recent (3.8 Ga to &lt;50 Ma). Early wrinkle ridge formation seems to be closely related to subsidence and flexure. For the recent and ongoing growth of wrinkle ridges and lobate scarps, global contraction with a combination of recession stresses and diurnal tidal stresses, as well as with a combination of South Pole‐Aitken ejecta loading and true polar wander are likely.

Formation and modification of wrinkle ridges in the central Tharsis region of Mars as constrained by detailed geomorphological mapping and landsystem analysis

Wrinkle ridges are common landforms documented on all rocky planets and the Moon in the inner solar system. Despite the long research history, their formation mechanisms remain debated. A key unresolved issue is whether the wrinkle-ridge formation is related to igneous processes. This is because wrinkle ridges are mostly associated in space and possibly in time with the occurrence of flood-basalt volcanism in all cases on the rocky bodies in the inner solar system. To address this issue, we conducted geomorphological mapping, a topographic-data analysis, and a detailed landform analysis of satellite images at a resolution of 25 cm/pixel to 6 m/pixel in the central Tharsis region of Mars. The main results of this work are in the form of (1) a regional geomorphological map at a resolution of 6 m/pixel and (2) a local geomorphological map at a resolution of 50 cm/pixel. Our work suggests the following sequence of geological events in the study area: (1) formation of a northeast-trending mountain range (i.e., the Thaumasia plateau) along the eastern margin of the Tharsis rise resulting from the Himalayan-style crustal-scale thrusting; (2) coeval volcanic-plateau construction west of the thrusting-induced rising mountain range; (3) termination of east-flowing lavas sourced from the volcanic plateau at the rising mountain range to the east; (4) wrinkle-ridge development by folding in recently emplaced warm, ductile volcanic-lava piles; (5) emplacement of a regionally extensive ice sheet over the central Tharsis region that produced extensive boulder-bearing materials, striated surfaces, and boulder-bearing dendritic-ridge networks possibly representing glacial eskers; and (6) deposition of locally highly concentrated glacial flours during deglaciation that resulted in the formation of mantled terrain on plains between wrinkle ridges. Our work supports the early suggestion that the Tharsis wrinkle ridges were created by horizontal shortening induced by crustal-scale tectonic processes. In detail, however, the occurrence of flow-front-like margins of many mapped wrinkle ridges suggests their formation by ductile deformation, which we attribute to the thermally weakened lava piles emplaced during or immediately before the folding event. Our compression-induced wrinkle-ridge model also differs from the early hypotheses in that the thin-skinned folding is associated with basement subduction, which explains the lack of coeval and parallel folding and extensional faulting. Post-folding glacial modification means that the present wrinkle-ridge morphologies may differ significantly from the original fold shapes, which prevents the utility of using present-day topographic profiles across wrinkle ridges for inverting the underlying thrust geometries.

Thrust Faults Bound an Elevated Mantle Plug Beneath Several Lunar Basins

AbstractThe lunar maria are large expanses of basalt that infill antecedent impact basins and show evidence for postemplacement deformation. Landforms within many of these basins suggest a period of compressive tectonics, although their formation mechanism has yet to be established. Previous work for Mare Crisium demonstrated that basin‐circumferential wrinkle ridges, which typically demarcate the inner edge of an annulus of elevated terrain, are the result of deep‐seated thrust faults that preferentially form along the boundary of an elevated superisostatic portion of mantle and a thick, subisostatic collar of crustal material. Here, we show that a similar fault architecture exists for several other mascon‐bearing basins, including Maria Serenitatis, Nectaris, Moscoviense, and, to a lesser degree, Humorum and Imbrium. These deeply penetrating basin‐circumferential thrust faults, as for Mare Crisium, form a (partial) outward‐dipping ring‐fault system that bounds the elevated mantle plug beneath each basin as a geometric consequence of mascon evolution. If this geometric arrangement is unique to the Moon, then some characteristic(s) of lunar mascon evolution enables the formation of such mascon‐bounding faults. Despite the ubiquitous nature of mascon‐bound thrust ring faults at several lunar basins, whether such structures exist at mascon basins on other terrestrial worlds remains an open question.

Analysis of lunar wrinkle ridges regarding the maximum displacement–length scaling relationship and relevant geological factors

Wrinkle ridges are thrust fault-related landforms that are widely distributed on the Moon and terrestrial planets. We investigated the dimensions of ∼260 well-preserved wrinkle ridges with sufficient length in nine lunar maria. We found a positive linear relationship between the maximum displacement Dmax and length L of ridges in each mare. The Dmax/L ratio (γ) varies from 6.0 × 10−3 in Mare Nectaris to 2.74 × 10−2 in Mare Orientale, which may be relevant to some geological factors (such as basin ages, gravity signatures, and basalt properties) and may depend on ridge formation times and growth stages. Basin formation ages and Bouguer gravity anomalies that possibly represent the regional flexure and concentration of stresses beneath basins are highly correlated with γ. Ridges are affected by basin modification processes. Significant in-group variations in γ indicate that faults could have grown based on the segment linkage model, having been frozen at different stages of tectonic development when growth stopped. We speculate that complex internal and external stresses acted on the lunar topography and changed the propagation of underlying thrust faults.