Geochronology and evolution of a complex barrier, Younghusband Peninsula, South Australia

This study examines the southeastern end of the Younghusband Peninsula in South Australia at a location called The Granites in order to gain a better understanding of the processes of formation of the foredune ridge system, and to investigate the drivers that controlled its progradational development during the Holocene. Our findings are based on amorphological analysis, a ground penetrating radar survey, and 14C and OSL dating. The Younghusband Peninsula at The Granites was formed by an initial aggradational phase resulting in a single complex foredune ridge, and which ended around 4.3 ka, and by a regressive (progradational) barrier phase (750 m wide) that developed in the last 4.3 ka, under very low rates of progradation (0.38 to 0.09 m/yr). The last part of this phase shows significant foredune ridge building in the last 1000 years or so. Barrier progradation via foredune ridge development is likely an effect driven by lowwave energy that favored conditions for coastal stability and foredune formation. Paleontological and GPR data indicate a maximum sea-level of +1.23 to +1.5 m, respectively, during initial barrier development. The foredune ridge plain of the barrier experienced at least three phases of significant aeolian activitywith ages centered at around 3.9, 3.4 and 3.0 ka suggesting their occurrence at 500 to 400-year events. Computer modelling indicates that sediments for the progradational phase of the barrier were provided by the forced regression produced by a sea-level fall over the past 4.3 ka. The large foredune complex formed during the last phase of progradation could be the result of both the very low progradation rate of 0.09 m/yr, and periods of disturbance possibly related to enhanced storm activity.

Transplanting Hybrid Potato Seedlings at Increased Densities Enhances Tuber Yield and Shifts Tuber-Size Distributions

To contribute to the development of a novel cropping system for potato grown from greenhouse-derived seedlings from hybrid true potato seeds, planting density trials were carried out under normal Dutch agronomic conditions. For two consecutive years, 5-week-old seedlings of two experimental genotypes were transplanted into farmers’ potato production fields at two contrasting locations: a flat-bed system on sandy soil and a traditional ridge system on clay soil. Planting densities were 6.25, 12.5, 25, 50, 100 and 200 plants/m2 in the flat-bed system, and 3.125, 4.688, 6.25, 12.5, 25 and 50 plants/m2 in the ridge system. In general, increasing planting density of hybrid seedlings per area decreased tuber fresh weight per plant and reduced the number of tubers per plant. On a per hectare basis, an increased planting density resulted in increased total tuber yield and number of tubers up to very high densities, but finally both parameters levelled off. Highest total tuber yields harvested were 107 and 45 Mg/ha for the flat-bed and ridge system, respectively. On flat-beds, the optimal planting density for total yield was 50 plants/m2. On ridges, planting density interacted with year and genotype, resulting in an optimum planting density of 25 plants/m2 to reach the maximum total yield. Obtained yields in the commercial size classes Baby Baker (20 < size class ≤ 35 mm) and Seed Tubers (28 < size class ≤ 50 mm) were in general very high on the flat-beds, with a maximum Seed Tuber yield of 64 Mg/ha at 50 plants/m2. The current study showed that transplanted hybrid seedlings are feasible alternatives for seed-tuber-grown systems for certain potato outlets.

Spatiotemporal Relationship between Arctic Mid-Ocean Ridge System and Intraplate Seismicity of the European Arctic

In this article, we investigate the influence of the Arctic mid-ocean ridge system (AMORS), including the Gakkel and Mohns ridges, and the Knipovich ridge–Lena trough (KL) segment, on seismicity of the Novaya Zemlya archipelago area (NZ) and the northernmost margin of the East-European Platform (EEP) for 1980–2019. For each individual area, the annual seismic energy was obtained by adding the energies of all earthquakes. To do this, we have converted various types of magnitude by different seismic networks into moment magnitude Mw. We compiled the updated catalog for the NZ, the northern EEP, and the northern part of the Ural fold belt (UFB). As a result, we constructed time distributions of annual seismic energy releases for each composing ridges of AMORS, NZ, and EEP combined with UFB. A model based on the Elsasser’s one describing the transfer of lithospheric stress disturbances in the horizontal direction was built, and quantitative calculations of the disturbance propagations from AMORS were performed. Results are in good agreement with the annual seismic energy time lags between rifts and NZ and EEP together with the UFB. We calculated correlation coefficients between the seismic energy releases over the time for the structures, enabling identification of the characteristic excitation cycles and estimation of the interval of disturbance transfer from AMORS. As a result, disturbances from the Gakkel ridge appear 3 yr later in NZ, from the KL segment in 4 yr, and from the Mona ridge in 8 yr. For the EEP + UBF combined area, we found the following disturbances spreading lags as 7 yr for the Mona ridge, 4 yr for the KL segment, and 5 yr for the Gakkel ridge. The obtained damping amplitudes of the disturbance spreading from the arctic ridges are sufficient to affect the intraplate seismic activity.

Rainfalls And Salinity Effects On Fecal Coliform Most Probable Number (MPN) Index Distribution In A Beach Ridge-Shore Ridge System In Mengabang Telipot, Terengganu, Malaysia

A Holocene beach ridge and present day shore ridge system located in a rural area north east of Kuala Terengganu was studied. The relation between fecal coliform (FC) MPN Index (Most Probable Number) distribution with rainfalls and saline intrusions into the unconfined aquifer of the beach ridge–shore ridge system was examined. The probable primary source of the pollutants was also investigated in order to highlight the susceptibility of such aquifers to pollution. Six sampling sessions were made from September 2009 to January 2010. Three represent drier conditions and the other 3, heavier rainfalls corresponding to the northeast monsoon season. This sampling period represent a condition when this area was still not subjected to major coastal erosions and subsequent rock revetment work. Altogether, water samples were taken from 13 wells and 3 river stations. Physical-chemical measurements were made in-situ, while FC was tested at UMT laboratory. Essentially, the results indicated that the groundwater in the unconfined aquifer layer of the beach ridge was moderately to highly polluted with FC (up to 1600 MPN). In contrast, the shore ridge was only slightly polluted, whereas river stations had mixed conditions but generally worse than the beach ridge and shore ridge. These phenomena could be associated with salinity spatial-temporal variations. Samples from heavy rainfall conditions indicated lower pollution levels compared to drier conditions. This phenomenon could be associated with the availability of more infiltrated atmospheric water to dilute pollutants in a high hydraulic conductivity environment as the ridges are made of fine to coarse sands. The results underscore the sensitivity of such environment to pollution transport and distribution and hence implied special attention with regards to water resource management.

Ridge Dynamics in the expanding Artemis Coronae: axis sinuosity, transform faults, and microplates.

&lt;p&gt;Venus today presents no large-scale network of subduction and accretion ridges, which is the signature of plate tectonics on Earth. On the other hand, Venus relatively young surface points towards either a quite recent catastrophic renewal of the whole planet surface (&amp;#171;&amp;#160;episodic subduction regime&amp;#160;&amp;#187;), or the continuous renewal of small areas of the planet for exemple by volcanism.&lt;/p&gt; &lt;p&gt;Unique to Venus, coronae are circular features from 50 to 2600 km in diameter. The largest ones have been attributed to mantle plumes. Close inspection of Magellan&amp;#8217;s data revealed that subduction features are also encountered on part of their rim (McKenzie et al, 1992&amp;#160;; Sandwell and Schubert, 1992, 1995).&amp;#160; Recent modeling has shown that plumes could indeed induce roll-back subduction around segments of an expanding coronae. Artemis coronae is the largest coronae on Venus and shows both plume and subduction features that are well explained by the plume-induced subduction mechanism (Davaille et al, 2017). Scaling laws then predict a slab roll-back (and therefore a coronae expansion) velocity between 1 and 10 cm/yr.&amp;#160; If the coronae has been expanding, then we should expect the existence of an accreting ridge system&amp;#160; inside the coronae, equivalent to the Earth&amp;#8217;s mid-ocean ridges developing in back-arc basins. Artemis interior indeed also presents a prominent ridge system (Sandwell and Schubert, 1992&amp;#160;; Brown and Grimm, 1996&amp;#160;; Spencer, 2001&amp;#160;; Hansen, 2002), but its lateral tortuosity is much more prononced than on Earth (fig.1).&amp;#160; &amp;#160;&lt;/p&gt; &lt;p&gt;Using laboratory experiments, we recently showed that the shape of an accretion ridge is governed primarily by the axial failure parameter &amp;#928;&lt;sub&gt;F&lt;/sub&gt;, which depends on the spreading velocity, the mechanical strength of the lithospheric material and the axial elastic lithosphere thickness (Sibrant et al, 2018). Experiments with the largest &amp;#928;&lt;sub&gt;F&lt;/sub&gt; presented quite unstable ridge axis with a large lateral sinuosity,&amp;#160; long transform faults, and the formation of numerous microplates. These microplates rotate along the transforms before getting incorporated in the main plate on one side of the ridge axis or the other. There, they appear as blocks whose main fabric is either concentric or rotated compared to the main plate&amp;#8217;s.&amp;#160;&lt;/p&gt; &lt;p&gt;On a planet, this regime occurs for high spreading velocity and/or low axial elastic thickness. For the Earth, it would require spreading velocities greater&amp;#160; than 30 cm/yr. But on Venus, where the surface temperature is about 500&amp;#176;C higher, and therefore the elastic thickness on the ridge axis is smaller than on Earth, spreading velocities between 1 and 10 cm/yr would suffice. The scaling laws derived from the laboratory experiments further predict a tortuosity of the ridge axis comparable to what is observed inside Artemis coronae (fig.1). Furthermore, guided by the experiments, we are tempted to identify two long transform faults on each side of Britomartis, as well as a number of rotated blocks or microplates. However, the resolution of Magellan data is not sufficient to be sure of our interpretation. There is an urgent need for better resolution and better coverage of Venus topography, that a mission such as VERITAS could provide.&lt;/p&gt; &lt;p&gt;&amp;#160;&lt;/p&gt;

Visibility of the Gask Ridge Road from Simulated Watchtowers: a Monte Carlo Testing Approach

The Gask Ridge system is a series of forts, fortlets, and timber watchtowers situated along a Roman road in northern Scotland. The high intervisibility of the watchtowers in the Gask Ridge system has resulted in the proposal of two main functions: one that the watchtowers were a signalling system and two that the watchtowers provided visibility of the Gask Ridge road for surveillance and monitoring. Despite this, only the former function has been assessed. This paper explores the function of the watchtowers along the Gask Ridge road using computational methods, including Monte Carlo hypothesis testing. The analytical approach, which is documented and reproducible with accompanying code, rejects that the watchtowers were randomly located along the Gask Ridge road, instead favouring the alternative hypothesis that the watchtowers were located to maximise the visibility of the road. Furthermore, it is possible to claim that the need to monitor the road shows a causal relationship with the location of the watchtowers, rather than associative. The findings support the interpretation that main function of the watchtowers was for the surveillance and monitoring of the Gask Ridge road, providing an early warning system of an attack from the Highlands (Woolliscroft, 1993).

"Eastern transfer" as the main argument in favor of the water origin of the ridge relief of the South of Western Siberia

New data were obtained in favor of “Eastern transfer” – the transfer of material from the North-East to the South-West during the formation of the ridge system in Late Pleistocene. They consist in two positions: first, they are longitudinal furrows in the axial part of the ridges, which are fan-shaped split at their South-Western ends; second, the inextricable genetic link of the ridge relief with the spillways is confirmed. The Eastern transfer is interpreted as convincing evidence of the water origin of the ridge relief.

Maximum Holocene groundwater levels and associated extension of peat in the border zone of ‘Het Gooi’ (the Netherlands): a reconstruction based on the study of soil transects

The area ‘Het Gooi’ in the Netherlands is part of a Pleistocene ice-pushed ridge system that partially drowned during the Holocene upon sea level and associated groundwater rise. As a result, the ridge system was gradually encroached by peat. From the late Middle Ages onward, man reclaimed the peatlands surrounding Het Gooi, heavily reducing their extension and lowering the regional groundwater level by increasingly intensive drainage. Based on historical and archaeological arguments, several authors assume that the Holocene peat cover in the border zones of ‘Het Gooi’ formed the extension of large raised peat bogs that formed further to the west and east, respectively. They presume that in the late Middle Ages these extensions reached ‘upslope’ to a maximum altitude of 3 m + NAP (Dutch Ordnance Datum – approximating mean sea level). However, the original extension is difficult to reconstruct, as this peat has disappeared as a result of its exploitation and oxidation, if having been present at all. In this study, the maximum extension of the Holocene peat cover on the ice-pushed ridge system was reconstructed based on soil characteristics. Used soil characteristics concerned the presence of iron coatings around sand grains and the upper boundary of gleyic features, because these are indicators for the mean highest groundwater level (MHG). For peat to form, this MHG needs to be at or just above the ground surface for most of the year. Based on study of a number of soil transects, we reconstructed to what maximum altitude peat encroachment may have occurred. This ‘maximum extension’ can alternatively be described as the maximum altitude of the bottom of the peat onlapping the ridge system. In the western border zone, this peat cover was found to have reached to c. NAP or just above, near Hilversum. No indications were found for the occurrence of raised bogs. We conclude that the phreatic groundwater level in this zone was controlled by the sea level and associated lake levels (Naardermeer and Horstermeer), a dominant role being played by the shallow presence of Pleistocene formations with a high hydraulic conductivity. In the eastern border zone, altitudes were more variable and in places reached 2 m + NAP. Peat at this higher elevation probably formed under the influence of a higher phreatic groundwater level, induced by the presence of a clayey Eemian fill with low hydraulic conductivity in the adjacent glacial basin (the Eem valley). This study demonstrates the value of detailed soil transect studies for palaeogeographical reconstructions of the former Holocene peat cover in Pleistocene landscapes of NW Europe. It also provides independent data for validation of geohydrological models for such landscapes.