Sinuous ridges in the Polesie region (SE Poland) as inverted fluvial channels: morphology, structure, and genesis

We present a geomorphic map of Chukhung crater (38.47°N, 72.42°W) in central Tempe Terra, Mars. Chukhung crater formed ~3.6–2.1 Ga, between the early Hesperian and early Amazonian periods of Mars' geologic history. It hosts dendritic networks of crater wall valleys, broad crater floor valleys, mid- to late-Amazonian-aged debris-covered glaciers, moraine-like deposits, and a radial assemblage of sinuous ridge landforms. We explore the origins of landforms in Chukhung crater, focusing in particular upon the sinuous ridges. In northern Chukhung crater, sinuous ridges extend downslope from fluvial valley systems on the northern crater wall. We interpret the northern sinuous ridges as inverted paleochannels: ridges formed by exhumation of resistant and/or indurated fluvial channel fill deposits. The origins of sinuous ridges on the southern floor of Chukhung crater are more ambiguous. They emerge from beneath moraine-like ridges which bound extant debris-covered glaciers extending from the southern wall of the crater. The southern sinuous ridges have numerous morphological and contextual similarities to eskers: ridges of glaciofluvial sediment deposited in meltwater conduits within or beneath wet-based glaciers. The close proximity of the northern and southern sinuous ridges, however, calls into question an interpretation which ascribes a different origin to each set. The similarity in the overarching process between esker and inverted channel formation (i.e., exposure by the removal of a bounding medium, be that ice or sediments/rock) results in convergence of form between eskers and inverted paleochannels. We discuss the esker-like characteristics of the southern sinuous ridges in detail, and argue that one of two ridge populations in southern Chukhung crater is best explained by the esker hypothesis while the other could be explained under either the esker or the inverted paleochannel hypothesis. Regardless of the specific formation mechanism for the southern sinuous ridges, we find that Chukhung crater has undergone significant modification by liquid water since its formation. The northern sinuous ridges and associated crater-wall valleys provide evidence for subaerial drainage of precipitation and/or snowmelt. This suggests that Chukhung crater, and possibly the surrounding region, experienced unusually warm and wet episodes between the early Hesperian and mid Amazonian. If some or all of the southern sinuous ridges are eskers, they could provide evidence for an additional influence of glacial meltwater in Chukhung crater during the mid-to-late Amazonian. If wet-based glaciation did occur in Chukhung crater, the location of the crater between major branches of the Tempe Fossae tectonic rift system would add to the growing body of evidence that elevated geothermal heat flux was an important driver of localized occurrences of recent wet-based glaciation on Mars.

<p><strong>Introduction</strong></p> <p>Inverted channel deposits or sinuous ridges are common on the Late-Noachian Early-Hesperian terrains on Mars<sup>[1,2]</sup>. These exhumed ribbon-like, sinuous sedimentary ridges have been interpreted to be evidence of existence of liquid water on early warm and wet Mars. In addition, these ridges have been interpreted to form as either: 1) short duration single-thread fluvial systems, likely from a single flow event<sup>[3]</sup> or 2) longer duration multi-thread systems which form channel-belt structure<sup>[4]</sup>. While single-thread systems more closely preserve the actual geomorphology of the fluvial system, the longer period of duration for the channel-belt systems makes it more conducive for ancient habitability. However, the channel-belt structure is inherently complex, preserving an interplay of contrasting lithologies and flow conditions over relatively longer periods of time. Considering these sinuous ridges are also sampling targets for rovers such as NASA’s Perseverance mission<sup>[5]</sup>, a detailed sedimentary analysis of preserved stratigraphy is important to understand the spatio-temporal distribution of architectural elements. Since in-situ observations of these ridges from Mars is still limited, sedimentology of Earth-based exhumed channel-belt deposits can be an important tool for reconstruction of long-lived fluvial processes on Martian surface.</p> <p> </p> <p><strong>Data and Methods</strong></p> <p>For this study, we rely on a combination of field-based observations from Earth and satellite image and topographic datasets from Mars. One of the best preserved sinuous ridge structures on Earth in the Oligo-Miocene Caspe Formation, Spain was utilized as a Terrestrial analogue. The sinuous ridges here formed a part of Guadalope-Matarranya fan that developed in an endorheic Ebro basin<sup>[6]</sup>. For the purpose of sedimentological analysis, detailed photopanel interpretation (recording detailed facies and architectural observations) was carried out at different roadcut outcrops, which provided a view nearly orthogonal to the axes of the ridges. This was supplemented with secondary observations in longitudinal view, parallel to the axes of the ridge. To compare this with Martian examples, 25–50 cm/pixel HiRISE<sup>[7]</sup> orthomosaics and derived DEMs were utilized to construct 3D models and conceptual architectural models were prepared for similar sinuous ridges on Mars at Hypanis fan, Eberswalde fan and Aram Dorsum.</p> <p> </p> <p><strong>Results and Discussions</strong></p> <p>In our example from Spain, we record that the extensive three-dimensional exposures exhibit facies relationships and sedimentary structures indicative of an amalgamated multistory sand bodies formed due to stacked sandstone bodies separated by erosional surfaces. Each individual story was interpreted to represent singular channel unit. These could be divided into thicker sandstone comprised channel-axis complexes and either associated or truncated thinner channel-wing complexes which extend into the floodplain horizon and preserve abundant floodplain mudstone between two such channel-wings. In addition, on each ridge face, three hierarchal surfaces were identified - Channel-bounding Surfaces, Bar-bounding Surfaces and Accretion surfaces. The nearly orthogonal ridge view also preserved the saw-tooth edges, which are commonly associated with reoccupational stacking where channels avulse and occupy previous channel locations<sup>[8]</sup>.</p> <p>Individual elements of this observed stratigraphy in the field are similar to those reported on Mars <sup>[e.g. 9]</sup>. These field based observations were used to prepare the conceptual models in form of synthetic cross-sections for Martian sinuous ridges and fluvial channel systems. With HiRISE mosaics, we identified key sedimentary features, such as point bars, recessive and protruding layering on the side of the ridges, etc and associated them with elevation data to identify possible distribution of architectural elements within the Martian sinuous ridges. This is helpful in understanding and predicting the distribution structures and lithologies, especially the finer-grained floodplain lithologies, which are important astrobiological targets. The structure of stacking within the Martian ridges also has important implications for usage of ridge elements in paleohydraulic reconstructions.</p> <p> </p> <p>References</p> <p>[1] Tanaka et al.,(2014), Geologic Map of Mars: USGS Scientific Investigations Series Map 3292, scale 1:20,000,000, pamphlet 43 p. [2] Carr et al., (2010), Earth and Planetary Science Letters 294(3-4), pp.185-203. [3] Zaki et al., (2022), Journal of Geophysical Research: Planets, 127, e2021JE007087. [3] Hayden et al., (2019), Icarus, 332, pp.92-110. [5] Farley et al., (2020) Space Science Reviews, 216(8), pp.1-41. [6] Cuevas Martinez et al., (2010), Sedimentology, 57(1), pp.162-189. [7] McEwen et al., (2007) Journal of Geophysical Research: Planets, 112(E5). [8] Chamberlin and Hajek, (2015) Journal of Sedimentary Research, 85(2), pp.82-94. [9] Skinner Jr et al., (2021), Icarus, 354, p.114071.</p>

Pervasive aqueous paleoflow features in the Aeolis/Zephyria Plana region, Mars

Barnard, a 121.1 km diameter crater along the southern rim of Hellas basin, is a well-preserved complex crater with a history of burial, excavation, and fluvial/glacial activity on its floor and walls. The interior of Barnard shows ice-rich deposits similar to other mid-to-high-latitude craters on Mars but is distinctive in that it also contains sinuous ridges. We have completed a geologic map of Barnard and surrounding materials using the global CTX mosaic. Mapping has identified and shown the distribution of features including sinuous ridges and fluvial channels, attributed to subglacial melting, and lobate debris aprons, mantling deposits, and arcuate ridges, indicative of the deposition and mobilization of ice within the crater. We have identified 13 geologic units on and around Barnard, including three distinct floor units, suggesting sustained periods of infill. We have conducted topographic and morphometric analyses using MOLA and HiRISE DTMs across Barnard and its interior landforms, which show significant infill on the crater floor (∼1 km thick), and local excavation of floor deposits indicating continued modification. Lobate debris aprons extending from the crater walls have maximum thicknesses of ∼300–350 m. Sinuous ridges on the crater floor range in height from ∼10 to 20 m. Crater counts on Barnard’s ejecta show that it formed ∼3.81 Ga in the Middle to Late Noachian, with subsequent periods of infill, excavation, fluvial, and wet-based glacial activity modifying its interior during the Late Hesperian/Early Amazonian, followed by further deposition and flow of ice-rich materials between ∼400 and 16 Ma into the Late Amazonian.

The Medusae Fossae Formation (MFF) is a geological formation comprising three geological units (members) spread across five principal lobes. It dominates a quarter of the longitudinal extent of the equatorial region of Mars. Positive relief features referred to as ‘sinuous ridges’ (commonly interpreted as inverted paleoflow channel or valley fills) have been observed in the lowest member of the western MFF, but have not been identified within the central and eastern portions of the formation, in the middle and upper members. This paper presents the identification and analysis of a branching, positive relief system which occurs in the central lobe of the MFF in what appears to be an exposure of the middle member. A simple geomorphological map of the system is presented, from which we have adopted the working hypothesis that this is an inverted fill of a branching fluvial channel or valley system. A suite of morphological and topographic evidence supporting this hypothesis is presented, including analysis of the network using a ∼15m/pixel digital terrain model derived from a Context Imager (CTX) stereo image pair. The evidence supporting this hypothesis includes: (1) the local slope and topography of the upper surface of the network are consistent with a contributory network; (2) the braided, fan-like form at the termination of the branching network is consistent in morphology with it being a depositional fan at the end of a fluvial system; (3) the terminal fan and surrounding deposits show layering and polygonization; and (4) there is strong association between the lower order branches and amphitheater shaped scarps in the depression walls. We evaluate the possible origins of this fluvial system and suggest that seepage sapping is the most probable. Two possible models for the evolution of the network and related features are presented; both require melt of ice within the MFF to form liquid water. We conclude that at least some portions of the Medusae Fossae Formation, if not the entire formation, were once volatile-rich. Finally, we note that our observations do not rule out the case that this network formed before MFF emplacement, and has since been exhumed. However, this conclusion would suggest that much of the surrounding terrain, currently mapped as middle-member MFF, is not in fact MFF material at all.

Geological mapping in eastern Poland resulted in the new find of organic deposits near Włodawa. Pollen and plant macrofossils analyses at the Dobropol site proved deposition during the Mazovian (Holsteinian) Interglacial (MIS 11). Pollen spectra indicated strong predominance of Carpinus in the optimum phase (pollen period III), suggesting intensive influence of continental climate in this part of Po land. The paleolake Dobropol was shallow, with many species of rushes in a littoral zone. During the Liviecian (MIS 10) and the Krznanian (MIS 8) Glaciations the reservoir was occupied by an ice-dam lake, in which silt and clay de position prevailed. The Mazovian Interglacial organic deposits were also recorded in immediate surroundings of the study area. Based on geological and paleobotanical examination of the Dobropol site, the ice sheet of the Krznanian Glaciation seemed to have reached at least the southern part of Włodawa. The ice sheet has not covered pre sum ably the whole study area as its advance occurred in several lobes. The surroundings of Włodawa in the West Polesie Region are the third largest Mazovian paleo-lakeland area in Po land, apart from the vicinities of Biała Podlaska and the Łuków Plain.

Human impact since medieval times in the western part of Lublin Polesie against the background of Holocene climate changes: record from Lake Mytycze in the Wieprz-Krzna Canal System (SE Poland)

A subset of the sinuous ridges (SRs) in the Aeolis/Zephyria Plana (AZP) region of Mars has been previously hypothesized to be inverted fluvial features, although the precise induration and erosion mechanisms were not specified. Morphological observations and thermal inertia data presented here support this hypothesis. A variety of mechanisms can cause inversion, and identification of the specific events that lead to fluvial SR formation can provide insights into the sedimentological, geochemical, and climatic processes of the region. Reconnaissance of two terrestrial lava‐capped ridges suggests some criteria that may be used to identify inverted fluvial features formed by lava infill on Mars, but these criteria are not satisfied by the majority of the AZP fluvial SRs. Armoring also appears inconsistent with terrestrial analogs. Layering and surface textures of fluvial SRs indicate that the most likely induration mechanism was geochemical cementation of fluvial sediments, and that the primary erosional mechanism that exposed the fluvial SRs was aeolian abrasion. This analysis of formation mechanism provides a foundation for estimating paleodischarge using an empirical form‐discharge approach, to which we have applied scaling, for Martian gravity. For those fluvial SRs meeting a set of criteria for accurate paleodischarge estimates, paleodischarge values generally range between 101and 103m3s−1. The largest of these initial estimates are comparable to paleodischarge estimates for some late‐stage Noachian fluvial channels on Mars, and provide a constraint on the atmospheric conditions at this equatorial location during the late Hesperian to early Amazonian time frame.

Analyses of dendritic ridges within Antoniadi crater, Mars, from CaSSIS and HiRISE data

The surface of Mars contains abundant sinuous ridges that appear similar to river channels in planform, but they stand as topographic highs. Ridges have similar curvature-to-width ratios as terrestrial meandering rivers, which has been used to support the hypothesis that ridges are inverted channels that directly reflect channel geometry. Anomalously wide ridges, in turn, have been interpreted as evidence for larger rivers on Mars compared to Earth. However, an alternate hypothesis is that ridges are exhumed channel-belt deposits— a larger zone of relatively coarse-grained deposits formed from channel lateral migration and aggradation. Here, we measured landform wavelength, radius of curvature, and width to compare terrestrial channels, terrestrial channel belts, and martian ridges. We found that all three landforms follow similar scaling relations, in which ratios of radius of curvature to width range from 1.7 to 7.3, and wavelength-to-width ratios range from 5.8 to 13. We interpret this similarity to be a geometric consequence of a sinuous curved line of finite width. Combined with observations of ridge-stacking patterns, our results suggest that wide ridges on Mars could indicate fluvial channel belts that formed over significant time rather than anomalously large rivers.

Branching to sinuous ridges systems, hundreds of kilometers in length and comprising layered strata, are present across much of Arabia Terra, Mars. These ridges are interpreted as depositional fluvial channels, now preserved as inverted topography. Here we use high‐resolution image and topographic data sets to investigate the morphology of these depositional systems and show key examples of their relationships to associated fluvial landforms. The inverted channel systems likely comprise indurated conglomerate, sandstone, and mudstone bodies, which form a multistory channel stratigraphy. The channel systems intersect local basins and indurated sedimentary mounds, which we interpret as paleolake deposits. Some inverted channels are located within erosional valley networks, which have regional and local catchments. Inverted channels are typically found in downslope sections of valley networks, sometimes at the margins of basins, and numerous different transition morphologies are observed. These relationships indicate a complex history of erosion and deposition, possibly controlled by changes in water or sediment flux, or base‐level variation. Other inverted channel systems have no clear preserved catchment, likely lost due to regional resurfacing of upland areas. Sediment may have been transported through Arabia Terra toward the dichotomy and stored in local and regional‐scale basins. Regional stratigraphic relations suggest these systems were active between the mid‐Noachian and early Hesperian. The morphology of these systems is supportive of an early Mars climate, which was characterized by prolonged precipitation and runoff.

Valley networks are some of the strongest lines of evidence for extensive fluvial activity on early (Noachian; >3.7 Ga) Mars. However, their purported absence on certain ancient terrains, such as Arabia Terra, is at variance with patterns of precipitation as predicted by “warm and wet” climate models. This disagreement has contributed to the development of an alternative “icy highlands” scenario, whereby valley networks were formed by the melting of highland ice sheets. Here, we show through regional mapping that Arabia Terra shows evidence for extensive networks of sinuous ridges. We interpret these ridge features as inverted fluvial channels that formed in the Noachian, before being subject to burial and exhumation. The inverted channels developed on extensive aggrading flood plains. As the inverted channels are both sourced in, and traverse across, Arabia Terra, their formation is inconsistent with discrete, localized sources of water, such as meltwater from highland ice sheets. Our results are instead more consistent with an early Mars that supported widespread precipitation and runoff.

The Argyre basin, located on the southern highlands, spans over 1500 km wide and is one of the largest impact basins on Mars. Three large valleys drain into Argyre from the southern circumpolar region, whereas the basin is breached at the north and perhaps connected to the Ladon-Morava-Ares outflow system draining into Chryse Planitia. Given its volume and valley connections, this basin played a key role in the global hydrology of early Mars (e.g., Clifford and Parker, 2001; Phillips et al., 2001). Several morphological features indicate that the basin may have contained a lake and/or ice sheet in the past, which could have been fed with meltwater from an ancient south polar ice sheet through three main inlet valleys (e.g., Hiesinger and Head, 2002; Ghatan and Head, 2004). A suite of sinuous ridges in the southern Argyre basin (ASRs)—commonly regarded as eskers—has been interpreted as evidence that an ice sheet once occupied the basin (e.g., Banks et al., 2009; Bernhardt et al., 2013). However, new morphological observations focusing on the context and stratigraphy raise discrepancies with the conventional esker interpretation, leading us to revisit their origin.To assess the origin of these ridges, we first have undertaken detailed morphometric measurements of ASRs and compared them to other glacial and fluvial ridge features on Earth and Mars. We mapped cross-sectional profiles at 1 km intervals along crestlines of ASRs using Context Camera (CTX) images and digital elevation models (DEM). We fitted power-law relationships to those ridge geometries, including width (W) and cross-sectional area (ACS). A power law is expected here because differing scaling relationships exist between channel width and bank-full discharge in fluvial (e.g., Parker et al., 2007) and subglacial systems (e.g., Ng, 1998, Hewitt and Cretys, 2019). We use ACS as a proxy for bank-full discharge (e.g., Ruso et al., 2024). Next, we carefully considered the stratigraphy of the ridges as well as the context where they are found, characterized by laterally extensive layered terrains. We measured dip and azimuths of individual layers observed within the ridge stratigraphy and compared them to those in the surrounding terrains. Then, we worked to understand the stratigraphic relationships between ASRs and surrounding layered terrains. Last, we performed crater counts using the buffer crater counting technique on the ASR to determine their ages (e.g., Kneissl et al., 2011).Two distinct populations of ASRs can be distinguished stratigraphically: NE-oriented ridges in the eastern population (upper) and NW-oriented ridges in the western population (lower). The power-law relationship for ASRs geometry, shown in Figure 1, shows a strong correlation between log-width and log-cross-sectional area, which is consistent with martian inverted fluvial channels in Aeolis Dorsa region, though the power-law exponents for ASRs are smaller than, yet still comparable to, the subglacial range. The measurement of layering structures revealed that the layers in ASRs are extremely horizontal (~0.07–

A beneficial outcome of ExoMars Rosalind Franklin Rover (ERFR) 1,2 landing site selection process has been the spinout science from detailed studies of parts of Mars that had not previously been examined in detail.  Here, we present the geological description of Aram Dorsum3 (Fig. 1), a well-preserved, flat‐topped, branching, ~85 km long and ~ 1 km wide ridge system in western Arabia Terra that was a ‘top 3’ candidate site during ERFR site selection.Fig 1. CTX Mosaic Showing Aram Dorsum (sinuous ridge running top right to lower left).We use morphostratigraphic mapping of the Aram Dorsum ridge and surrounding area, and detailed morphological observations, to propose a consistent working hypothesis for the geological history of the region. Our observations and mapping reveal Aram Dorsum to be the sedimentary deposits of an extensive aggradational fluvial channel belt system, now preserved in positive relief by differential erosion. The existing ridge was once a large river channel belt set in extensive flood plains, many of which are still preserved.Aram Dorsum is part of a wider set of similar inverted channels found across Arabia Terra4,5, and thus was probably part of a regional fluvial system, demonstrating movement of water and sediment across large distances. Furthermore, several smaller palaeochannel belts feed into the Aram Dorsum ridge from within the local regions, and their setting and network pattern suggest a distributed and local source of water. Aram Dorsum therefore appears to record both regionally and locally distributed sources of water.Combining mapping with HiRISE6 and CTX7 Digital Elevation Model data reveals that the Aram Dorsum alluvial succession is up to 60 m thick, suggesting a formation time of 105 to 107 years by analogy to Earth8. Correlating our observations with previous regional‐scale mapping9 shows that Aram Dorsum formed in the mid‐Noachian, a result supported by impact crater size frequency distribution measurements.The Aram Dorsum formation comprises a succession of what are, by analogy with terrestrial fluvial systems, probably coarse‐grained fluvial channel belt sandstones and finer‐grained overbank deposits. The vertical thickness of alluvial succession equates to several cubic kilometres of fluvial sediments in this study region alone. That other inverted channels elsewhere in Arabia Terra4,5,10 are similar in morphology and scale suggest that similar thicknesses and volumes of mid‐Noachian to late‐Noachian fluvial sediments may be extensive and common in the wider region.Aram Dorsum was an extensive long-lived fluvial system with distributed sources. This suggests that local and regional precipitation (either as rain or as seasonal or repeated snow melt) was the source of water. That Aram Dorsum is one of several similar systems suggests that precipitation was widespread across western Arabia Terra during this period. In contrast, Aram Dorsum's low elevation and distance from the majority of the Valley Networks, argues against the source of water being melting of a distant, high‐altitude, ice sheet, or ice cap11,12. Similarly, the aggradational fluvial depositional setting and the scale of the system do not suggest deposition from multiple short‐lived fluvial flows, as might have occurred due to impact cratering or catastrophic volcanic outgassing temporarily altering the climate12–15. We conclude that Aram Dorsum is one of the oldest fluvial systems described on Mars and indicates climatic conditions that sustained surface river flows on early Mars.References cited