Coarse-grained ripples investigated by the Opportunity rover on Meridiani Planum, Mars

Aeolian coarse-grained ripples have been found in all regions investigated by Mars rovers: Meridiani Planum, Gusev crater, Gale crater, and Jezero crater. Therefore, it can be assumed that coarse-grained ripples are one of the most common landforms on Mars. Studying their formation and evolution gives us the opportunity to determine past and current wind patterns. They are also crucial for understanding the formation and evolution of larger aeolian bedforms. Of all locations studied in situ on Mars, coarse-grained ripples in extensive (∼100 $km^{2}$) ripple fields were found only on Meridiani Planum. As coarse-grained ripples on Mars are not well characterized in the literature, in this work, the morphometry, morphology, spatial distribution, and orientation of coarse-grained ripples investigated along the 45 km long traverse of the Opportunity rover were analyzed. The obtained results allowed for a more precise definition of coarse-grained ripples and for distinguishing three classes of coarse-grained ripples on Meridiani Planum: small, medium, and large. The coarse-grained ripple activity on Meridiani Planum is now limited due to low material supply, and the relatively strong induration of the ripple surfaces. Even though most of the coarse-grained ripples on Meridiani Planum were formed thousands of years ago, some smaller coarse-grained ripples were formed by modern winds

Simultaneous growth releases and reductions among Populus alba as an indicator for floods in dry mountains (Morocco)

We studied the growth reaction of silver poplar trees (Populus alba) to a large flood in November 2014 in the semi-arid High Atlas Mountains, Morocco. The flood resulted in half of the studied trees developing wider tree rings in 2015 and the other half developing narrower rings in 2015, next year after the flood. For 57.1% of trees which released growth in 2015, this was the most significant increase of ring width during their whole lives (in whole tree-ring chronologies), and for 23.8% of trees which reduced growth in 2015, this was the most significant decrease of ring width. Tree-ring reductions in next year after the 2014 flood resulted from environmental stress related to burying stems with alluvia deposited during the flood. Fresh sediments cut off air access from the root system, and for some of the sampled trees, this stress was strong enough to control their radial growth. Growth releases that follow the 2014 flood are a record of trees benefitting from a sudden supply of water, a rare opportunity in dry study area, where water is usually scarce. The study demonstrates that floods in high mountains of arid zone can cause dual, opposite growth reaction of affected trees. Such dual record is characteristic for environmental impulses, which exert stress on trees, but, at the same time, improve other conditions of tree growth. Environmental events that cause simultaneous positive and negative reactions among a population of trees, like studied flood, can easily be overlooked in chronologies based on average widths of tree rings each year. For trees affected during studied flood arithmetical mean of ring widths in 2015 is average and does not stand out from arithmetical means for other years. However, when analysed in detail, the year 2015 is significantly different from other years, as is demonstrated by high values of dispersion indicators (standard deviation and coefficient of variation) calculated for all sampled trees. This study demonstrates that following the standard procedure (developing tree-ring chronology from average ring widths) is not a reliable solution for reconstructions of environmental impulses which cause dual, opposite reaction among sampled trees. Even strong events of this type will not be emphasised in standard chronologies, which can lead to underestimating frequency and magnitude of processes and, in the case of floods, to underestimating hazard and risk

Scale-dependent perspectives on the geomorphology and evolution of beachdune systems

Despite widespread recognition that landforms are complex Earth systems with process-response linkages that span temporal scales from seconds to millennia and spatial scales from sand grains to landscapes, research that integrates knowledge across these scales is fairly uncommon. As a result, understanding of geomorphic systems is often scale-constrained due to a host of methodological, logistical, and theoretical factors that limit the scope of how Earth scientists study landforms and broader landscapes. This paper reviews recent advances in understanding of the geomorphology of beach-dune systems derived from over a decade of collaborative research from Prince Edward Island (PEI), Canada. A comprehensive summary of key findings is provided from short-term experiments embedded within a decade-long monitoring program and a multi-decadal reconstruction of coastal landscape change. Specific attention is paid to the challenges of scale integration and the contextual limitations research at specific spatial and/or temporal scales imposes. A conceptual framework is presented that integrates across key scales of investigation in geomorphology and is grounded in classic ideas in Earth surface sciences on the effectiveness of formative events at different scales. The paper uses this framework to organize the review of this body of research in a 'scale aware' way and, thereby, identifies many new advances in knowledge on the form and function of subaerial beach-dune systems. Finally, the paper offers a synopsis of how greater understanding of the complexities at different scales can be used to inform the development of predictive models, especially those at a temporal scale of decades to centuries, which are most relevant to coastal management issues. Models at this (landform) scale require an understanding of controls that exist at both ‘landscape’ and ‘plot’ scales. Landscape scale controls such as sea level change, regional climate, and the underlying geologic framework essentially provide bounding conditions for independent variables such as winds, waves, water levels, and littoral sediment supply. Similarly, an holistic understanding of the range of processes, feedbacks, and linkages at the finer plot scale is required to inform and verify the assumptions that underly the physical modelling of beach-dune interaction at the landform scale

Ichnofabrics of the Upper Cretaceous fine-grained rocks from the Stołowe Mountains (Sudetes, SW Poland)

Upper Cretaceous fine-grained rocks (the “Plänermergel”) from the Stołowe Mountains are in general strongly bioturbated. The sections studied (180 m thick), located in the southern part of the mountains, are dominated by mudstones, marlstones and siltstones; sandstones, partly unbioturbated, are subordinate. The entire sequence shows a succession of ichnofabrics, which reflects a transgressive-regressive cycle (Cenomanian) and a regressive cycle (lower to middle/upper? Turonian). The trace fossil assemblage contains nine ichnogenera: Asterosoma, Cylindrichnus, Ophiomorpha, Palaeophycus, Phycosiphon, Planolites, Taenidium, Teichichnus, and Thalassinoides. Three basic types of ichnofabrics have been recognized: Ophiomorpha, Thalassinoides and Phycosiphon, all representing fully marine ichnofacies. The first two of these belong to the Cruziana ichnofacies, indicating the offshore zone, and the third one probably to the Zoophycos ichnofacies indicating a quiet shelfal setting below storm wave base

Vertical profiles of aeolian mass flux above different sand surfaces and sand surfaces covered with pebbles

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