Comparitive Study of the Geomorphological Characteristics of Valley Networks between Mars and the Qaidam Basin

The complex valley networks that cross the Martian surface offer geomorphologic evidence of the presence of liquid water at some point in its history. However, the derivation of both temporal and hydrological dimensions of this climate phase is far from settled. Studies comparing terrestrial fluvial networks of known formation environments with those on Mars can be used as a key to unlock the past. This work represents an analogy study and comparison between the river networks in the Qaidam Basin and those on Mars. As the Martian valley networks formed in different geologic periods with characteristic and unique features, three cases from the Noachian to the Amazonian were selected to be compared with streams in the Mangya area, where the climate is extremely arid. In terms of the maturity of the dendritic river system, shape, concave index, and branching angle (BA), the valley network in the Mangya area is comparable to Naktong Vallis, dated to the Hesperian. We also calculated throughout the valley networks on Mars the parameters of the BA and the concave index, both of which are important climatic indicators. The results show that the climate on Mars became progressively more arid, starting from the Noachian up to the Amazonian.

The global distribution of depositional rivers on early Mars

Sedimentary basins are the archives of ancient environmental conditions on planetary surfaces, and on Mars they may contain the best record of surface water and habitable conditions. While erosional valley networks have been mapped, the global distribution of fluvial sedimentary deposits on Mars has been unknown. Here we generated an eight-trillion-pixel global map of Mars using data from the NASA Context Camera (CTX), aboard the Mars Reconnaissance Orbiter spacecraft, to perform the first systematic global survey of fluvial ridges—exhumed ancient deposits that have the planform shape of river channels or channel belts, but stand in positive relief due to preferential erosion of neighboring terrain. We used large fluvial ridges (>70 m width) as a conservative proxy for the occurrence of depositional rivers or river-influenced depositional areas. Results showed that fluvial ridges are as much as 100 km long, common across the southern highlands, occur primarily in networks within intercrater plains, and are not confined to impact basins. Ridges were dominantly found in Noachian through Late Hesperian units, consistent with cessation of valley network activity, and occurred downstream from valley networks, indicating regional source-to-sink transport systems. These depositional areas mark a globally distributed class of sedimentary deposits that contain a rich archive of Mars history, including fluvial activity on early Mars.

The Influence of Relief on the Density of Light-Forest Trees within the Small-Dry-Valley Network of Uplands in the Forest-Steppe Zone of Eastern Europe

An active process of the invasion of woody vegetation, resulting in the formation of light forests, has been observed in predominantly herbaceous small dry valleys of the forest-steppe uplands of the East European Plain over the past two decades. This paper investigates the spatial features of the density of trees in such light forests and its relationship with relief parameters. The Belgorod Region, one of the administrative regions of European Russia, was chosen as a reference for the forest-steppe zone of the plain. The correlation between some relief characteristics (the height, slope, slope exposure cosine, topographic position index, morphometric protection index, terrain ruggedness index, and width and depth of small dry valleys) and the density of light-forest trees was estimated. The assessment was carried out at the local, subregional and regional levels of generalization. The relief influence on the density of trees in the small dry valley network is manifested both through the differentiation of moisture within the territory under study and the formation of various conditions for fixing tree seedlings in the soil. This influence on subregional and regional trends in the density is greater than on local trends. The results obtained are important for the management of herbaceous small-dry-valley ecosystems within the forest-steppe uplands in Eastern Europe.

Valley complexes as ecosystem assets of heat island of urban agglomerations (on the example of the right-bank part of Kyiv)

The analysis of the influence of the valley network of the right-bank part of Kiev on the formation of summer surface temperatures based on the use of materials of space remote sensing is carried out. The results of processing Landsat satellite images from 1987 to 2018, presented as isotherms, were used. Comparison of temperature data, hypsometry, geomorphologic features, types of earth cover was carried out according to profiles crossing the valleys in the most representative areas. The main factors influencing the formation of the temperature field within the valleys are vegetation, insolation exposure and anthropogenic stress. The studies revealed the lowest temperatures in the valleys at the foot of the slopes of the northern exposure, covered with woody vegetation. It was established that the temperatures in the valleys with wood cover are 5–6С and lower than the temperatures on the built-up water divide and 2–30С lower than in the park zones on the water divide. As a result of the peculiarities of the internal atmospheric circulation, stagnation in the valleys, with significant anthropogenic pressure (buildings, highways, railways), positive thermal anomalies and even geochemical ones are formed. Unfavorable ecological conditions (high level air pollution, flooding of foundations) are formed on the river Lybid and Kiyanka stream. Due to climatic changes and constantly growing anthropogenic pressure (increase in the area of impermeable surfaces, density and number of storey of residential buildings), temperatures within the city's “thermal island” for the study period increased by an average of 2–30С. Preservation of the valley network in its natural state provides a kind of oases within the city with favourable microclimatic and recreational conditions.

Fluvial incised networks on top of late Ordovician interglacial valley buried hills as the result of post glacial isostatic rebound; 3D seismic input

<p>It is classically assume that prior to deep glacial valleys incision below large scale ice cap, often interpreted as the results of ice flow melting during tidewater period, the initial glacial topography was flat or very low angle and created during a major phase of cold glaciers advance as suggested by quaternary studies. Therefore up to now we have assume that the top of late Ordovician buried hills separating major glacial valleys was the remains of this flat surface truncating the pre-glacial Ordovician Hawaz series, later on flooded by the Lower Silurian. Surprisingly by reinterpreting 3D seismic cubes using spectral decomposition technics on the Murzuk basin in SE Libya, it appears that the top of buried hills are not at all characterized by a flat erosional surface, but it is strongly irregular and shows the development of narrow valley networks displaying the classical dendritic erosional pattern diagnostic of fluvial erosion. These small valleys are organized into a tributary network and don’t flow toward the ice margin, i.e. toward the N-NW but most of the time flow at right angle toward the adjacent main glacial valleys which are pointing toward the NW. These narrow valley networks in this context could be either glacial tunnel valleys located at the periphery of the ice cap in close relationships with glacial fronts (their common settings) or could correspond to fluvial valleys developed later on, in a subaerial setting at some distance from glacial fronts; we retain this second interpretation because in addition to the geomorphic features: (1) they flow parallel to the fronts that we have already recognized, Moreau et al. (2005), Rubino et al.  2007 and (2) they are suspended in the sense that these lateral networks do not reach the bottom of the main glacial valley but, they appear to be connected within the upper part of the glacial infill, immediately below the early Silurian post glacial flooding characterized by the well-known Rhuddanian hot shales. As a result, the incision of the valley network appears quite late in the ice cap melting history. It is why we tend to interpret these valleys erosion as the result of post glacial melting during ice retreat at some distance from the ice front and strongly enhanced by isostatic rebound. Some possible modern analogs of such valley fringing highs may exist in Artic Canadian islands.</p>

Cartographic Representation of Channel Forms on Planetary Geologic Maps

<p> </p><p>Channel morphologies are sinuous, negative-relief linear forms that form by a current of water or lava. They may be fluvial or volcanic in origin. Channels are exclusively volcanic on Venus, volcanic or fluvial on Mars and fluvial on Titan. On Venus and Mars, channels are all paleoforms while on Titan (and Earth) they are actively forming. Channels may be hosted by valleys, that represent the cumulative erosional history of the embedded channel. They may be singular or may form braided pattern separated by streamlined island forms (e.g., Kasei Valles); a channel floor may host interior channels (e.g., Navua Valles), and channels may disappear gradually into flat plains (e.g., Simud Vallis). These are just a few of their characteristics that make their cartographic representation a complex issue.</p><p>In this work we analyzed and compared the symbology of channel forms in planetary geologic maps. An ongoing work on planetary geologic symbology identified 95 maps containing channel symbols in a total of 154 map (Nass et al. 2017b). Symbology is important for several reasons (Nass et al. 2011, Nass et al. 2017a). Although each map is complete on its own, standardized symbology enables direct comparison between maps. Maps are used for measurements: channel morphometry measurements across different quadrangles become problematic if symbols are used and defined differently.</p><p>Planetary geologic maps use three classes of symbols for representing channel forms: polygons as geologic units, polygons as surficial units laid over a geologic unit and line symbols for smaller channels. Line symbols often transform to geologic units when they reach a cutoff size for the used map scale. Line symbols do not continue over the unit symbols. This way drainage networks are split into two, incompatible symbol types. The cutoff size is often not reported in the legend that use the vague "narrow channels" designation for the line symbols. Sometimes line symbols are used only for "small distributary channels" or "small valleys".</p><p>Named channel units may be grouped geographically (e.g., Ares Vallis), by age (e.g., Hesperian channels), by morphology (steep walled channels), process (outflow channels) or as true geologic units (vallis floor sediments). These categories may be even mixed within one map.</p><p>The line symbols are typically solid blue (cyan) lines. This is in accordance with FGDC standards (FGDC 2006).</p><p>Different problems arise with drainage databases (Hynek et al. 2010, Alemanno et al. 2018). They typically uniformly trace dendritic valley networks, but they also contain singular and other channel forms, whereas "outflow channels" and lava channels are missing from these databases. The global map of Tanaka et al. (2014) uses two different blue line symbols for "channel axis" (i.e., valley network and some outflow-like channels) and "outflow channels".</p><p>It is needed to redefine channel form classification in the planetary domain and symbology (from Venus to Mars to Titan) and make it clear for mappers if different symbols should be used for different sizes, origins, and morphologies and how different symbols may be combined in one map.</p><p> </p>