scholarly journals Structure of end moraines and dynamics of the recession phase of the Warta Stadial ice sheet, Kłodawa Upland, Central Poland

2020 ◽  
Vol 12 (1) ◽  
pp. 753-763
Author(s):  
Magdalena Anna Drążczyk

AbstractThe occurrence of end moraines reflects the dynamics of an ice sheet, and their inner structure is determined by processes taking place in marginal zones. In the southern part of the Kłodawa Upland of Central Poland, such moraines were formed, but opinions conflict as to their origin, including the influence of local transgression of the ice sheet, as well as its areal and frontal recession. The primary aim of this article is to analyse the inner structure of forms to define the dynamic state of the Warta Stadial ice sheet of the Odra Glaciation (Saalian). The conducted research includes fieldwork at four key sites, where lithofacial analysis was performed, as well as a geomorphological and geological mapping that included two cross-sections in greater detail. In exposures, the work focused on deformed structures of sediments. Description of key sites was extended by the creation and the analysis of general geological cross-sections. Considering the results of the research, the Kutno end moraines should not be classified as push moraines – they were revealed to be accumulative in character.

2016 ◽  
Vol 12 (4) ◽  
pp. 911-921 ◽  
Author(s):  
André Düsterhus ◽  
Alessio Rovere ◽  
Anders E. Carlson ◽  
Benjamin P. Horton ◽  
Volker Klemann ◽  
...  

Abstract. Sea-level and ice-sheet databases have driven numerous advances in understanding the Earth system. We describe the challenges and offer best strategies that can be adopted to build self-consistent and standardised databases of geological and geochemical information used to archive palaeo-sea-levels and palaeo-ice-sheets. There are three phases in the development of a database: (i) measurement, (ii) interpretation, and (iii) database creation. Measurement should include the objective description of the position and age of a sample, description of associated geological features, and quantification of uncertainties. Interpretation of the sample may have a subjective component, but it should always include uncertainties and alternative or contrasting interpretations, with any exclusion of existing interpretations requiring a full justification. During the creation of a database, an approach based on accessibility, transparency, trust, availability, continuity, completeness, and communication of content (ATTAC3) must be adopted. It is essential to consider the community that creates and benefits from a database. We conclude that funding agencies should not only consider the creation of original data in specific research-question-oriented projects, but also include the possibility of using part of the funding for IT-related and database creation tasks, which are essential to guarantee accessibility and maintenance of the collected data.


2019 ◽  
Vol 5 (4) ◽  
pp. 73-95
Author(s):  
Nikolai A. Senkin ◽  
Aleksandr S. Filimonov ◽  
Kirill E. Kharitonov ◽  
Vitaliy V. Yakovlev ◽  
Elizaveta O. Bondareva ◽  
...  

As part of student research at the St. Petersburg University of architecture and construction, alternative proposals are being developed for the creation of a circumferential high-speed highway with a total length of 147.2 km. Тhe scheme is proposed in the form of a polygon with HUB in the nodes and consists of three main parts: 1 above-ground (62.6 km), 2 above-water (29.6 km) and 3 surface-underground (55.0 km). The main tracks are located in a four-tube steel beam, each tube of which is organized by the technology of vacuum tube transport with a pressure of 10% of the normal for high-speed passenger trains on a magnetic levitation cushion using a linear traction motor (Maglev system). The rail base of the 1520 mm gauge is located along the entire length of the track, both in parking lots, acceleration and braking zones, and on the main high-speed sections for movement with a maximum speed of 500 km per hour. The main direction of research was the development of load-bearing structures that provide the necessary functionality, reliability and safety of structures. In order to reduce the noise impact on the metropolis, overcome numerous artificial and natural obstacles, improve anti-terrorist protection, the main level of the rail track for the above-ground and above-water structures was adopted at +88.00 in the Baltic elevation system. Calculations of variants with determination of internal forces in elements and movements of nodes with use of the program complex SCAD Office 21.1are executed, when accounting for the full range of loads taking into account dynamic effects and non-linearity. The selection of cross-sections of elements according to the method of limit states according to the current norms is carried out. The advantage of the arch-cable-stayed variant with a span of 360 m in strength, stability, stiffness and vertical size (height of supports) is shown. The continuation of research and design work on this topic should lead to the emergence of a district high-speed transport system at the borders of communication between St. Petersburg and the Leningrad region with passenger traffic, quite comparable to the metro line. Aim: To develop a district high-speed transport system at the borders of St. Petersburg and Leningrad region with passenger traffic comparable to the metro line. Materials and Methods: Using the software package "SCAD Office 21.1", the trestle structures are calculated for the combination of operating loads, forces and influences, including the consideration of dynamic aspects and nonlinearity, as well as the selection of cross-sections of elements by the method of limit states. To determine the optimal trestle structures of high-speed highways, namely high-rise and long-length metal structures supporting the overpass beam, calculations with the selection of cross sections of four variants of cable-stayed systems (arch-cable-stayed; cable-stayed rod with inclined cables and steel lattice pylons; the same, steel pipe-concrete pylons; cable-stayed rod system with suspensions according to the patent US5950543 (A). Results: the results of the trial design adopted arch-cable option with a span of 360 m according to the criterion of metal consumption, the consumption of steel amounted to 20.9 tons per 1 m length of highway. Conclusion: the estimated volume of passenger traffic per day for the four-track high-speed line will be 280 thousand passengers, and 102 million passengers per year, which is quite comparable to this figure for the metro line.


2021 ◽  
Author(s):  
Marco Möller ◽  
Beatriz Recinos ◽  
Ben Marzeion

<p>The Greenland Ice Sheet is losing mass at increasing rates. Substantial amounts of this mass loss occur by ice discharge. The ice sheet is surrounded by thousands of peripheral glaciers, which are dynamically decoupled from the ice sheet, and which account for ~10 % of the global glacier ice volume outside the two main ice sheets. Rather low-lying along the coasts, these peripheral glaciers are also losing mass at increasing, but disputed, rates. The total absence of knowledge about the role and share of solid ice discharge in this mass loss adds to the controversy. Since the quantification of ice discharge is still pending, a full understanding of ice mass loss processes in this globally important glacier region is substantially hampered.</p><p>Here, we present the first estimation of ice discharge from Greenland's peripheral tidewater glaciers. For each of these 760 glaciers, we combine an idealized rectangular flux gate cross sections derived from modelling with the Open Global Glacier Model with surface ice flow velocities derived from the ITS_LIVE and MEaSUREs remote sensing datasets to calculate glacier specific ice discharge on both annual and multi-annual time scales over the period 1985 to 2018. For the few glaciers not covered by either of the employed original datasets or modelling methods we use a regression tree-based extrapolation scheme to estimate the necessary input data for our calculation.</p><p>Our findings indicate a significant overall increase of ice discharge over the study period although several individual glaciers show contrasting developments. This increase became especially apparent across the southern parts of Greenland. Our results also show that the total of the ice discharge from Greenland's peripheral tidewater glaciers is dominated by few major contributors and that this dominance is completely time-independent.</p>


1987 ◽  
Vol 9 ◽  
pp. 221-224 ◽  
Author(s):  
Minoru Yoshida ◽  
Kazunobu Yamashita ◽  
Shinji Mae

Extensive echo-sounding was carried out in east Dronning Maud Land during the 1984 field season. A 179 MHz radar with separate transmitting and receiving antennae was used and the echoes were recorded by a digital system to detect minute reflections. The results gave cross-sections of the ice sheet along traverse routes from lat. 69 °S. to 75°S, Detailed observations on the ground at Mizuho station showed that there was elliptical polarization in the internally reflected echoes when two antennae, kept in parallel with each other, were rotated horizontally. The internal echoes were most clearly distinguished when the antenna azimuth was oriented perpendicular to the flow line of the ice sheet. The internal echoes with a high reflection coefficient were detected at depths of 500–700 m and 1000–1500 m at Mizuho station. Since a distinct internal echo at a depth of 500 m coincides with a 5 cm thick volcanic ash-laden ice layer found in the 700 m ice core taken near the observation site, these echoes may correspond to the acidic ice layers formed by past volcanic events in east Dronning Maud Land.


2020 ◽  
Vol 191 ◽  
pp. 15 ◽  
Author(s):  
Jonas Vanardois ◽  
Pierre Trap ◽  
Philippe Goncalves ◽  
Didier Marquer ◽  
Josselin Gremmel ◽  
...  

In order to constrain the finite deformation pattern of the Variscan basement of the Agly massif, a detailed structural analysis over the whole Agly massif was performed. Our investigation combined geological mapping, reappraisal of published and unpublished data completed with our own structural work. Results are provided in the form of new tectonic maps and series of regional cross-sections through the Agly massif. At variance from previous studies, we identified three deformation fabrics named D1, D2 and D3. The D1 deformation is only relictual and characterized by a broadly northwest-southeast striking and eastward dipping foliation without any clear mineral and stretching lineation direction. D1 might be attributed to thickening of the Variscan crust in a possible orogenic plateau edge position. The D2 deformation is a heterogeneous non-coaxial deformation, affecting the whole massif, that produced a shallowly dipping S2 foliation, and an anastomosed network of C2 shear zones that accommodated vertical thinning and N20 directed extension. D2 is coeval with LP-HT metamorphism and plutonism at ca. 315–295 Ma. D2 corresponds to the extensional collapse of the partially molten orogenic crust in a global dextral strike-slip at the scale of the whole Variscan belt. The D2 fabrics are folded and steepened along a D3 east-west trending corridor, called Tournefort Deformation Zone (TDZ), where the Saint-Arnac and Tournefort intrusives and surrounding rocks share the same NE-SW to E-W subvertical S3 foliation. Along the D3 corridor, the asymmetrical schistosity pattern and kinematic criteria suggest a D3 dextral kinematics. The D3 deformation is a record of E-W striking dextral shearing that facilitated and localized the ascent and emplacement of the diorite and granitic sheet-shaped plutons. D3 outlasted D2 and turned compressional-dominated in response to the closure of the Ibero-Armorican arc in a transpressional regime. The progressive switch from D2 thinning to D3 transpression is attributed to the lessening of gravitational forces at an advanced stage of extensional collapse that became overcome by ongoing compressional tectonic forces at the southern edge of the Variscan orogenic plateau.


1997 ◽  
Vol 113 (1-2) ◽  
pp. 55-80 ◽  
Author(s):  
K. Brodzikowski ◽  
A.J. Van Loon ◽  
T. Zieliński
Keyword(s):  

2020 ◽  
Vol 92 (3) ◽  
pp. 423-446
Author(s):  
Piotr Lamparski

The Ground Penetrating Radar (GPR) method potentially offers many possibilities for fast and reliable lithostratigraphic sediment models to be developed. From a cognitive point of view, this represents a major simplification and shortening of procedures with which information about sediments can be obtained. And from the point of view of the economy of operations, there can be a significant reduction in costs and time of research in shallow geology and the stratigraphy of areas where unconsolidated clastic sediments are of superficial occurrence. Also noteworthy is the possibility for the results of GPR surveys to be deployed in support of geological mapping, as well as in the shallow exploration of resources and hydrogeological studies.The most major advantage of the GPR method related to the possibility of the structure of forms being observed in full shape. In the absence of large outcrops, geophysical prospection of geomorphological forms is helpful, insofar as we are able to translate the results of geophysical surveys into the actual lithostratigraphic system of sediments building a specific form.Against that background, the research presented in this article forms part of the work to develop radar stratigraphy, as an important support for direct geological research (Huggenberger et al., 1994; Van Overmeeren, 1998; Beres et al., 1999, Overgaard and Jakobsen, 2001; Jakobsen and Overgaard, 2002; Neal, 2004; Lejzerowicz et al., 2014; Żuk and Sambrook Smith, 2015; Lejzerowicz et al., 2018). It also points to the research potential of the GPR method in determining the genesis of form. The discussion on the way kames form has been going on in the literature for years (Niewiarowski, 1959; 1961; Karczewski, 1971; Klajnert, 1978; Jaksa, 2003; Terpiłowski, 2008). The studies presented here do not suffice to allow the matter to be determined comprehensively, even though they do provide for verification of the opinions of previous researchers.The area forming the subject of this article is defined by Niewiarowski (1959) as the dead ice zone because of the characteristic set of forms (dead ice moraines, kames and eskers). Like modern researchers (Terpiłowski, 2008), Niewiarowski points to the importance of sub-Quaternary surface elevations in the formation of cracks in the ice sheet, with this leading on to the formation of kame hills above such elevations. This would also seem to have been one of the reasons for the formation in the mass of ice of lakes whose filling with sediment and melting ice walls took the form of kames.The great advantage of the GPR method lies in its ability to recognise macrostructural sediment patterns in glacilimic forms. This diagnosis allows for the high-probability assessment of the genesis of form, especially in the context of its position being determined in the marginal zone of the ice sheet. Also looking extremely promising is the capacity for the thickness of fine clastic sediments lying on till to be determined using GPR. It allows for the determination of the way in which a given form is rooted.Described as they are in brief only, test results for selected sites serve to confirm the great usefulness of the GPR method in the recognition of shallow lithostratigraphy of clastic sediments. Nevertheless, this should not be the only method used to recognise the geological structure of forms and sediments. Significant interpretation ambiguities mean that the GPR method should act in support of direct lithostratigraphic research, not merely serving as an alternative to it. GPR surveys offer a depiction particularly close to the real one – of sediment present in homogeneous sediments in relation to electrical parameters. Sediments ideal for GPR surveys would for example be fine dry sands or silts – and it is precisely these sediments that built most of the investigated kame forms.


2012 ◽  
Vol 57 ◽  
pp. 105-120 ◽  
Author(s):  
Włodzimierz Narloch ◽  
Jan A. Piotrowski ◽  
Wojciech Wysota ◽  
Nicolaj K. Larsen ◽  
John Menzies

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