Browsing by Author "van Loon, A.J. (Tom)"
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Item A hitherto unknown river type from the Archaean at Bhurkuli (Jharkhand, E India)(Instytut Geologii UAM, 2017-08) van Loon, A.J. (Tom); De, ShuvabrataThe Archaean granitoid pluton of the Singhbhum craton in E India is overlain by Archaean to Palaeoproterozoic metasediments. These sediments are still poorly known and their stratigraphy is under debate. Several scattered, most probably Meso- to Neoarchaean, conglomerates are present in the state of Jharkhand that differ so much in characteristics that they are probably not related to each other. The sedimentology of a series of conglomerate patches and layers near Bhurkuli has been investigated, including the characteristics of the clasts. It is deduced on the basis of these characteristics and the sedimentological context that the Bhurkuli conglomerates represent the channel facies of a river system that differed from the types of fluvial systems that exist nowadays.Item A new type of slumping-induced soft-sediment deformation structure: the envelope structure(Instytut Geologii UAM, 2019-08) Byun, Uk Hwan; van Loon, A.J. (Tom); Kwon, Yi Kyun; Ko, KyoungtaeThe sediments of the Cretaceous Gyeokpori Formation in south-western South Korea accumulated in a lake in which mainly siliciclastic rocks were deposited, with some interbedded volcaniclastics. The nearby volcanic activity resulted in unstable lake margins inducing a dominance of gravity-flow deposits. The high sedimentation rate facilitated soft-sediment deformation on the sloping margin. The deposition of numerous gravity-flow deposits resulted in a vertically heterolithic stratification. The slumps are composed of different lithologies, which is expressed in different types of deformation due to the difference in cohesion between sandy and mussy layers within the slumps. Coarser-grained (cohesionless) slumps tend to show more chaotic deformation of their lamination or layering. The difference in slumping behaviour of the cohesive and non-cohesive examples is explained and modelled. A unique soft-sediment deformation structure is recognized. This structure has not been described before, and we call it ‘envelope structure’. It consists of a conglomerate mass that has become entirely embedded in fine-grained sediment because slope failure took place and the fine-grained material slumped down with the conglomerate ‘at its back’. The cohesive laminated mudstone formed locally slump folds that embedded the non-cohesive overlying conglomerate unit, possibly partly due to the bulldozing effect of the latter. This structure presumably can develop when the density contrast with the underlying and overlying deposits is exceptionally high. The envelope structure should be regarded as a special – and rare – type of a slumping-induced deformation structure.Item Engineering-geological and geotechnical investigations for risk assessment of the University Olympic Village in Izmir (Turkey)(Bogucki Wydawnictwo Naukowe, 2010-03) Kincal, Cem; Koca, Mehmed Yalçin; Yilmaz, H. Recep; Akgün, Mustafa; Özyalm, Şenol; Eskişar, Tuğba; Akçiğ, Zafer; van Loon, A.J. (Tom)The Metropolitan Municipality of Izmir (Turkey) designated a steeply inclined area for the construction of buildings to house the participants of the Izmir University Olympic Games. Before the construction activities could start, engineering geological and geotechnical investigations had to be carried out in order to establish which zones in the area were suitable for safe constructions. Seismic studies, borings and laboratory tests yielded the data, which were used for preparing five hazard maps in a GIS environment. The construction activities based on the results of this complex investigation appeared successful. The engineering geological investigations included geotechnical measurements on core samples obtained from the boreholes (core drilling) and laboratory testing. The rock-quality designation (RQD%) values of the rock units were determined and used in the rock-mass classification (rock-mass rating method) as an in-put parameter and in the calculation of the bearing capacity of the various rock units. Geophysical surveys were carried out to determine the seismic velocity of the rocks at the site. A short overview is provided of the main problems that had to be dealt with, and of the successive steps taken to solve the engineering-geological problems. Determination of these problems is necessary for adequate land-use planning and construction activities.Item First find of biogenic activity in the Palaeoproterozoic of the Singhbhum craton (E India)(Wydawnictwo Naukowe UAM, 2013-09-15) van Loon, A.J. (Tom); Mazumder, R.The Palaeoproterozoic succession of the Singhbhum craton in E. India was hitherto considered as almost entirely siliciclastic and partly volcanogenic. Here we describe, from the fine-grained, tidally influenced shale facies of the Palaeoproterozoic Chaibasa Formation (2.1–1.6 Ga), a fine, originally more or less horizontal, wavy to strongly undulating (later locally deformed) lamination. Investigation of these laminae shows that they must be ascribed to the accumulation of fine particles on microbial mats that covered a sandy substrate. The structures must therefore be considered as stromatolites, features that are accepted as proof of the presence of micro-organisms, in this case most probably cyanobacteria. The interpretation of biogenic activity is supported by microscopic analysis. It is the first description of traces left by biogenic activity that took place in the Palaeoproterozoic of the Singhbhum craton.Item Glacial Terminations II and I as recorded in NE Iceland(Wydawnictwo Naukowe UAM, 2010) Van Vliet-Lanoë, Brigitte; Guðmundsson, Agust; Guillou, Hervé; Guégan, Soléne; van Loon, A.J. (Tom); De Vleeschouwer, FrançoisVolcanism in eastern Iceland has controlled the changes in glacier- and river-drainage patterns and the sedimentary budget, particularly during the Middle and Late Pleistocene. The glacial extent in NE Iceland appears to be related to the impact of volcanic activity, not only on the ice-stream dynamics, but also on the sedimentary successions. Analysis of the Jökuldalur and Jökulsa á Brù records results in a new interpretation of the changes in ice extent and flow direction for at least the last two glaciations. From MIS 8 onward, the development of the Snæfell volcano apparently forced the ice stream that derived from the Vatnajökull ice cap to take another course; it also affected the offshore sedimentary budgets at the new outlet at Vopnafjördur. The MIS 6 ice sheet was thick and extensive, and associated with an ice-stream diversion to the North. The thick sedimentary complex of palaeolake Halslón was formed close to an outlet of the Vatnajökull, the Brùarjökull, during Termination II and a part of the MIS 5e interglacial. The deposits formed during MIS 5e record two climate optima interrupted by two successive glacial advances correlated with the mid-Eemian cooling. The deposits of the Weichselian deglaciation (Termination I) are much more limited in thickness. During the Last Glacial Maximum and the Late Glacial, glaciers also seem to have been restricted in the Jökulsa á Brù area. Valley glaciers issued from the Brùarjökull re-advanced several times in the Jökuldalur only during at least the Older Dryas, the Younger Dryas and the Preboreal. NE Iceland has undergone considerable deglaciation since the Bølling. In contrast to the conclusions of previous studies, the results presented here are consistent with data on the glaciations in other Nordic regions and can increase the understanding of the mid-Eemian cooling.Item Interaction between turbidity currents and a contour current – A rare example from the Ordovician of Shaanxi province, China(Wydawnictwo Naukowe UAM, 2019-04) Li, Hua; van Loon, A.J. (Tom); He, YoubinThe silty top parts of graded turbidites of the Late Ordovician Pingliang Formation, which accumulated along the southern margin of the Ordos Basin (central China), have been reworked by contour currents. The reworking of the turbidites can be proven on the basis of paleocurrent directions in individual layers: the ripple-cross-bedded sandy divisions of some turbidites show transport directions consistently into the downslope direction (consistent with the di- rection of other gravity flows), but in the upper, silty fine-grained division they show another direction, viz. alongslope (consistent with the direction that a contour current must have taken at the same time). Both directions are roughly perpendicular to each other. Moreover, the sediment of the reworked turbidites is better sorted and has better rounded grains than the non-reworked turbidites. Although such type of reworking is well known from modern deep-sea environments, this has rarely been found before in ancient deep-sea deposits. The reworking could take place because the upper divisions of the turbidites involved are silty and consequently relatively easily erodible, while the contour current had locally a relatively high velocity – and consequently a relatively large erosional capability – because of confinement within a relatively narrow trough.Item Large-scale land-suitability mapping in the GIS environment for the construction site of the University Olympic Village in Izmir (Turkey)(Bogucki Wydawnictwo Naukowe, 2009) Kincal, Cem; Koca, M. Yalçin; van Loon, A.J. (Tom)Participants of the 23rd University Olympic Games held in Izmir (Turkey) were hosted in a Universiade Olympic Village that had to be newly constructed. A risk analysis has been performed to assess potential engineering problems at the envisaged construction site. The risk analysis was largely based on a new, large-scale land-suitability map that was prepared in the GIS environment with much detail for this type of construction work. Information was collected from several maps, in combination with mapping in the field, drilling and seismic data. Geological, geotechnical, geophysical and morphological data were then superimposed on these analyses. This sequence of overlay analyses was performed with the help of GIS software (MapInfo Professional 7.5); this resulted in five hazard maps. Risk points (1-11) were then attributed to the different zones in the five digital hazard maps. A land-suitability map indicating the suitability for envisaged constructional activities was subsequently obtained in the form of an overlay of the five hazard maps, thus allowing to calculate a total risk for each zone on this map. The land-suitability map that was thus obtained, has been prepared for a 1:1,000 scale development plan; such a large scale is uncommon in this context.Item Possible pitfalls in the procedure for paleobiodiversity-dynamics analysis(Wydawnictwo Naukowe UAM, 2008) Ruban, Dimitry A.; van Loon, A.J. (Tom)The changes in the diversity of specific taxa during certain parts of the geological past (paleobiodiversity dynamics) can, in principle, be established by counting the number of the fossil taxa present (worldwide or in a specific study area) in rocks dated for the time interval under study. Numerous obstacles are present, however, for instance in the form of lacking field data, disappeared collections, ambiguous identifications, temporary ‘disappearence’ of taxa, and dating problems. One major problem is the fact that, particularly in regional studies in some countries, a local, regional or national chronostratigraphic terminology is used rather than the chronostratigraphy recommended by the International Stratigraphic Commision of the International Union of Geological Sciences. This hampers international correlation and makes precise global paleodiversity-dynamics analyses extremely difficult. A reliable insight into the true paleodiversity dynamics requires not only that the various problems are recognized, but also that their consequences are eliminated or, if this is impossible, minimized. This is particularly important if the effects of mass extinctions on fauna and flora are investigated. Each analysis of paleobiodiversity-dynamics analysis of phenomena related to mass extinctions should therefore try to quantify the impact that missing data or inaccuracies of any kind may have on the final results; such an analysis should, in addition, try to find a solution for the major problems, so as to avoid significant inaccuracies of the calculated values. Large electronic databases can help, since about a decade, to diminish possible errors in diversity estimates. Paleobiodiversity should preferably be expressed in the form of values with a certain band with, indicating the inaccuracy, rather than in the form of exact values.Item Reconstruction of sediment provenance and transport processes from the surface textures of quartz grains from Late Pleistocene sandurs and an ice-marginal valley in NW Poland(Instytut Geologii UAM, 2015-06) Woronko, Barbara; Pisarska-Jamroży, Małgorzata; van Loon, A.J. (Tom)During the Pomeranian phase of the Weichselian glaciation (~17–16 ka), the Toruń-Eberswalde ice-marginal valley (NW Poland and easternmost Germany) drained water from the Pomeranian ice sheet, while intensive aeolian process -es took place across Europe in the foreland of the Scandinavian ice sheet (‘European Sand Belt’). The micromorphology of the quartz grains in the Toruń-Eberswalde ice-marginal valley shows no traces of these aeolian processes, or only vague signs of aeolian abrasion. This is unique among the aeolian sediments in other Pleistocene ice-marginal valleys in this part of Europe. The study of the surfaces of the quartz grains shows that the supply of grains by streams from the south was minimal, which must be ascribed to the climate deterioration during the Last Glacial Maximum, which resulted in a decrease of the discharge of these extraglacial rivers to the ice-marginal valley.Item Reflections on subglacial megafloods: their possible cause, occurrence, and consequence for the global climate(Bogucki Wydawnictwo Naukowe, 2009) van Loon, A.J. (Tom)Huge water reservoirs exist subglacially, for instance in the form of lakes. Failure of a wall around such a lake underneath the central part of a large ice mass may result in huge water outbursts. The resulting megafloods will rarely be traceable along the ice front, because much power is lost by friction and because the flood spreads subglacially over a large area. Truly giant meltwater outbursts might, however, still have an enormous power when reaching the marginal area of an ice cap. Such a megaflood may both affect the integrity of the ice mass, and help create a sliding layer over which huge ice masses can be easily transported towards the ocean, thus triggering a Heinrich-like event. This would have great impact on the global climate. Some of the Heinrich events that occurred during the past hundreds of thousands of years may well have been due to giant subglacial water outbursts, and such a situation may equally well occur in the time to come.Item Sedimentary environment and palaeogeography of the? Palaeocene–Middle Eocene Kashkan Formation, Zagros fold-thrust belt, SW Iran(Wydawnictwo Naukowe UAM, 2012) Yousefi Yeganeh, Bizhan; Feiznia, Sadat; van Loon, A.J. (Tom)The Kashkan Formation (?Palaeocene to Middle Eocene) in the Zagros fold-thrust belt, SW Iran, which is intercala-ted between to marine limestone formations, consists of conglomerates, sandstones and siltstones. The sedimentology and the palaeogeography of the Kashkan Formation had not received any attention thus far, but have now been studied in seven sections, situated in the province of Lorestan. The sediments form twelve lithofacies, three ichnosubfacies and seven architectural elements, which are described, depicted and analysed. The analysis leads to the conclusion that most sediments accumulated in a low-sinuosity, low-gradient braided-river system (characterised by mainly unidirec -tional palaeocurrent directions, and by sheetfloods), that occasionally showed meandering characteristics (represented by overbank deposits and large bars). The deposits of this system closely resemble those of the South Saskatchewan River in Canada, which is considered as the classical example of a sand-bed braided river. The river flowed roughly from North to South, as deduced by palaeocurrent indicators such as imbrication and large- to medium-scale trough cross-stratification (direction measured in the trough axes). This current direction is supported by the southward to south-westward thinning of the formation and by the diminishing average grain size in the same direction. The trace fossils in the Kashban Formation fit all in the Skoyenia ichnofacies, which has here three ichnosubfacies which allow a more detailed palaeoenvironmental reconstruction, indicating that the braided stream passed into the low-energy sho -reface zone of a tidally-influenced sea.Item Seismic and non-seismic soft-sediment deformation structures in the Proterozoic Bhander Limestone, central India(Bogucki Wydawnictwo Naukowe, 2014-06-30) Sarkar, Subir; Choudhuri, Adrita; Banerjee, Santanu; van Loon, A.J. (Tom); Bose, Pradip K.Numerous soft-sediment deformation structures occur within the Proterozoic Bhander Limestone of an intracratonic sag basin in a 750 m long section along the Thomas River, near Maihar, central India. Part of these deformation structu -res have most probably a non-seismic origin, but other structures are interpreted as resulting from earthquake-induced shocks. These seismic structures are concentrated in a 60 cm thick interval, which is interpreted as three stacked seismi -tes. These three seismites are traceable over the entire length of the section. They divide the sedimentary succession in a lower part (including the seismites) deposited in a hypersaline lagoon, and an upper open-marine (shelf) part. Most of the soft-sediment deformations outside the seismite interval occur in a lagoonal intraclastic and muddy facies asso -ciation. The SSDS within the seismite interval show a lateral continuity. They record simultaneous fluidisation and liquefaction. The bases of each of the three composing seismite bands are defined by small-scale shear folds, probably recording an earthquake and aftershocks. The presence of the three seismite bands at the boundary between the lagoonal and the overlying open-marine oolitic facies association suggests that the seismic event also triggered basin subsidence.Item Slide origin of breccia lenses in the Cambrian of the North China Platform: new insight into mass transport in an epeiric sea(Wydawnictwo Naukowe UAM, 2012) van Loon, A.J. (Tom); Han, Zuozhen; Yu, HanAn oolite in the Furongian (Late Cambrian) Chaomidian Formation in Shandong Province, China, which was deposited on the North China Platform in an epeiric sea, contains several limestone breccia lenses of various dimensions (centimetres to decimetres thick and decimetres to more than 10 metres in length) in an E-trending section. The oolite, which is approximately 40 cm thick, was originally thicker, as indicated by a planar truncation surface that formed by wave abrasion. The breccia lenses in this oolite are generally mound-shaped with a flat base and a convex top. The western margin of the lenses is commonly rounded whereas the eastern margin commonly has a tail (consisting of a rapidly eastwards thinning breccia horizon that gradually ends in a horizon of isolated clasts). Some of the breccia lenses are underlain by a shear zone. The formation of the breccia lenses cannot be easily explained by normal depositional or deformational processes. It is concluded that the lenses represent fragments of a partly consolidated layer, consisting of both rounded and angular platy clasts, which slid down over a very gently inclined sedimentary surface which acted – possibly together with a water film – as a lubricant layer. During transport, the layer broke up into several discrete bodies that formed small ‘highs’ at the sedimentary surface of the shallow epeiric sea. Subsequently, waves partially eroded the lenses, mostly at their margins, producing their mound-shaped form. Sliding of blocks is known from a wide variety of environments in the sedimentary record; however, this is the first description of the sliding of blocks in an epeiric sea. This indicates that such a low-relief submarine carbonate setting is, like its siliciclastic counterparts, susceptible to this process.Item Soft-sediment deformation structures in cores from lacustrine slurry deposits of the Late Triassic Yanchang Fm. (central China)(Instytut Geologii UAM, 2016-12) Yang, Renchao; van Loon, A.J. (Tom); Yin, Wei; Fan, Aiping; Han, ZuozhenThe fine-grained autochthonous sedimentation in the deep part of a Late Triassic lake was frequently interrupted by gravity-induced mass flows. Some of these mass flows were so rich in water that they must have represented slurries. This can be deduced from the soft-sediment deformation structures that abound in cores from these lacustrine deposits which constitute the Yanchang Fm., which is present in the Ordos Basin (central China). The flows and the resulting SSDS were probably triggered by earthquakes, volcanic eruptions, shear stress of gravity flows, and/or the sudden release of overburden-induced excess pore-fluid pressure. The tectonically active setting, the depositional slope and the high sedimentation rate facilitated the development of soft-sediment deformations, which consist mainly of load casts and associated structures such as pseudonodules and flame structures. Sediments with such deformations were occasionally eroded by slurries and became embedded in their deposits.Item Soft-sediment deformation structures in siliciclastic sediments: an overview(Bogucki Wydawnictwo Naukowe, 2009) van Loon, A.J. (Tom)Deformations formed in unconsolidated sediments are known as soft-sediment deformation structures. Their nature, the time of their genesis, and the state in which the sediments occur during the formation of soft-sediment structures are responsible for controversies regarding the character of these deformations. A definition for soft-sediment deformation structures in siliciclastic sediments is therefore proposed. A wide variety of soft-sediment deformations in sediments, with emphasis on deformations in siliciclastic sediments studied by the present author, are described. Their genesis can be understood only if their sedimentary context is considered, so that attention is also paid to the various deformational processes, which are subdivided here into (1) endogenic processes resulting in endoturbations; (2) gravity-dominated processes resulting in graviturbations, which can be subdivided further into (2a) astroturbations, (2b) praecipiturbations, (2c) instabiloturbations, (2d) compagoturbations and (2e) inclinaturbations; and (3) exogenic processes resulting in exoturbations, which can be further subdivided into (3a) bioturbations – with subcategories (3a’) phytoturbations, (3a’’) zooturbations and (3a’’’) anthropoturbations – (3b) glaciturbations, (3c) thermoturbations, (3d) hydroturbations, (3e) chemoturbations, and (3f) eoloturbations. This subdivision forms the basis for a new approach towards their classification. It is found that detailed analysis of soft-sediment deformations can increase the insight into aspects that are of importance for applied earth-scientific research, and that many more underlying data of purely scientific interest can, in specific cases, be derived from them than previously assumed. A first assessment of aspects that make soft-sediment deformation structures in clastic sediments relevant for the earth sciences, is therefore provided.Item Texture and composition of the Rosa Marina beach sands (Adriatic coast, southern Italy): a sedimentological/ecological approach(Instytut Geologii UAM, 2016-08) Moretti, Massimo; Tropeano, Marcello; van Loon, A.J. (Tom); Acquafredda, Pasquale; Baldacconi, Rossella; Festa, Vincenzo; Lisco, Stefania; Mastronuzzi, Giuseppe; Moretti, Vincenzo; Scotti, RosaBeach sands from the Rosa Marina locality (Adriatic coast, southern Italy) were analysed mainly microscopically in order to trace the source areas of their lithoclastic and bioclastic components. The main cropping out sedimentary units were also studied with the objective to identify the potential source areas of lithoclasts. This allowed to establish how the various rock units contribute to the formation of beach sands. The analysis of the bioclastic components allows to estimate the actual role of organisms regarding the supply of this material to the beach. Identification of taxa that are present in the beach sands as shell fragments or other remains was carried out at the genus or family level. Ecologi- cal investigation of the same beach and the recognition of sub-environments (mainly distinguished on the basis of the nature of the substrate and of the water depth) was the key topic that allowed to establish the actual source areas of bioclasts in the Rosa Marina beach sands. The sedimentological analysis (including a physical study of the beach and the calculation of some statistical parameters concerning the grain-size curves) shows that the Rosa Marina beach is nowadays subject to erosion.Item The 2014 field symposium ‘Late Quaternary terrestrial processes, sediments and history: from glacial to postglacial environments’(Instytut Geologii UAM, 2014-12) Börner, Andreas; Pisarska-Jamroży, Małgorzata; van Loon, A.J. (Tom)Item The challenge of reconstructing the Phanerozoic sea level and the Pacific Basin tectonics(Wydawnictwo Naukowe UAM, 2010) Ruban, Dmitry A.; Conrad, Clinton P.; van Loon, A.J. (Tom)The relationships between the interior dynamics of our planet and global sea level can be unravelled when plate-tectonic reconstructions are available for the entire Earth. A review of global tectonics reveals significant deficiencies in our understanding of the geodynamic evolution of the Pacific (Panthalassa or Proto-Pacific) during the Cambrian-Jurassic time-span. This particular, but major, shortcoming presents a true challenge for modern geoscientists, who are encouraged to produce a detailed plate-tectonic reconstruction of the Pacific for the pre-Cretaceous in order to advance our understanding of Phanerozoic sea-level change. A set of approaches, including geological/geophysical modelling, investigation of accretionary prisms, palaeobiogeographical studies, and careful examination of eustatic sea-level changes, are proposed that will help geoscientists tackle the challenge of understanding how Pacific geodynamics affected global sea level during the Phanerozoic.Item The life cycle of seismite research(Bogucki Wydawnictwo Naukowe, 2014-06-30) van Loon, A.J. (Tom)Item The Mesoproterozoic ‘seismite’ at Laiyuan (Hebei Province, E China) re-interpreted(Bogucki Wydawnictwo Naukowe, 2014-06-30) van Loon, A.J. (Tom)A 1-million m3 breccia near Laiyuan (Hebei Province, E China) occurs as a block-like lithological unit between dolo -stones of the 1.55–1.45 Ga (Early Mesoproterozoic) Wumishan Formation. It has previously been interpreted as a seis -mite, but it appears not to fulfil any of the commonly accepted criteria that jointly are considered diagnostic for seis -mites. Its presence in a graben-like structure with almost vertical bounding fault planes rather indicates an origin as a (submarine) valley fill. As the valley originated by tectonic activity in the form of faulting, the breccia can be consid-ered as a secondary effect of seismic activity, but it does not represent a seismite.