Anna Wysocka

Alluvial deposits from the strike-slip fault Lo River Basin (Oligocene/Miocene), Red River Fault Zone, north-western Vietnam

Abstract The Lo River Basin (LRB) is one of several narrow sedimentary basins associated with the main faults of the Red River Fault Zone separating the South China and Indochina microplates. The basin is located on the NE boundary of the high-grade metamorphic Con Voi Massif and the sedimentary and metasedimentary Viet Bac fold zone in north-eastern Vietnam. The LRB is filled with over 6000 m of Oligocene/Miocene alluvial deposits. The source area was probably located on the NE margin of the basin and was composed mostly of low-grade metamorphic rocks with a minor component of sedimentary rocks. Three alluvial systems are recognised. The oldest system was a proximal braided river system, with the minor occurrence of alluvial fans. The younger systems record changes in clast composition and lithofacies, which suggests a transition from a distal braided river to a distal braidplain system. The LRB fill shows a range of features characteristic of strike-slip fault basins. The origin of the LRB is correlated with the left-lateral transtensional regime. The present shape of the basin is a result of post-sedimentation tectonic activity.

Formation of intracontinental basins in the opposite corners of the Tabas block as coeval structures controlled by transpressional faulting, Iran

The interaction of strike-slip faults in their restraining junctions allowed for the coeval formation of the Tabas and Abdoughi Basins and led to their inversion during the late Cenozoic. The intracontinental basins filled with Neogene and Quaternary deposits were controlled by large-scale dextral transpression along major faults that bounded the Tabas block, which is a part of the Central Iranian block. The anastomosing strike-slip fault pattern facilitated the development of both basins in opposite corners of the Tabas block. The subsided areas were formed as a result of interaction between the restraining junctions of strike-slip faults and thrusts. Flexural loading caused by the uplifted series of thrust sheets resulted in the depression of the opposite fault slabs, which permitted deposition of Neogene sediments. Deformation according to the “bookshelf” mechanism can be considered as a consequence of accommodation of the shortening of the area north of the Main Zagros thrust and externally imposed shearing along the Great Kavir (Doruneh) fault during the collision of the Arabian and Eurasian plates. Related processes of transpression and counterclockwise rotation of the tectonic blocks included in the Central Iranian block favored the interaction of strike-slip faults. The change of far-field stress and continuous transpression caused inversion of the basins and formation of Neogene folds in the northern and southern corners of the Tabas block. The geomorphic features observed along these strike-slip faults and on the thrust surfaces bounding the folds display their recent activity, consistent with present-day seismicity and geodetic measurements within the Central Iranian block.

The usefulness of ground-penetrating radar images for the research of a large sand-bed braided river: case study from the Vistula River (central Poland)

Abstract Ground-penetrating radar (GPR) surveys and sedimentological outcrop analyses were combined in order to determine the reflection patterns and internal architecture of terrace deposits of the Vistula River at Kępa Zawadowska in the southern part of Warsaw (central Poland). The sedimentary analyses concerned the granulometric composition and lithofacies analysis. The 34 GPR profiles, which were obtained in two outcrops, using a Malå RAMAC/GPR system with 500-MHz and 250-MHz shielded antennas, were up to 100 m long. The most characteristic ground-penetrating radar profiles are presented; they show a high-resolution data set of radar facies. The GPR data suggest the presence of three geophysically different units, namely with high-angle inclined reflections (radar facies 1), with discontinuous undulating or trough-shaped reflections (radar facies 2), and with low-angle reflections (radar facies 3). The internal structure of the fluvial deposits was obtained by integration of the GPR and sedimentological data, which combination provides a more accurate visualisation of sedimentary units than do reconstructions that are based only on standard lithologic point data.

Sedimentary architecture and ground penetrating radar (GPR) analysis of sandy-gravel esker deposits in Kozlow, Central Poland

The study area is situated near Kozlow village, about 70 km south-east from Warsaw (Central Poland), where relatively young unconsolidated fluvioglacial sediments are mined. The excavated sandy-gravel body is built up by architectural elements typical for esker deposits. Ground penetrating radar (GPR) surveys and sedimentological outcrop analyses are combined in order to characterize reflection patterns, internal architecture and to assess the GPR methods potential for imaging of Quaternary fluvioglacial deposits. Ground penetrating radar is a non-invasive tool which allows visualization of the subsurface so that excavations or point data are unnecessary. The results show that the sediments deposited by the glacier meltwater produce characteristic radar facies, which can be observed in sandy-gravel pit. Representative research points were selected where the GPR data could be directly correlated and compared with sedimentary information derived from exposures thus, geomorphological data could be provided. The study generated a high resolution data set of lithofacies and ground penetrating radar profiles. The results obtained for the study area show that integration of sedimentological data with geophysical imaging (GPR) enables the identification of stratigraphie units at the scale of depositional elements. Gridded ground penetrating radar surveys hold promise for 3-dimensional discovery of stratigraphy in the Kozlow esker and in other fluvioglacial deposits in Central Poland. The integration of sedimentological and GPR results provides a more accurate description and visualization of sedimentary units compared to reconstructions based solely on point data.

Tectono-sedimentary analysis using the anisotropy of magnetic susceptibility: a study of the terrestrial and freshwater Neogene of the Orava Basin

Abstract The Orava Basin is an intramontane depression filled with presumably fine-grained sediments deposited in river, floodplain, swamp and lake settings. The basin infilling constitutes a crucial record of the neoalpine evolution of the Inner/Outer Carpathian boundary area since the Neogene, when the Jurassic-Paleogene basement became consolidated, uplifted and eroded. The combination of sedimentological and structural studies with anisotropy of magnetic susceptibility (AMS) measurements provided an effective tool for recognition of terrestrial environments and deformations of the basin infilling. The lithofacies-oriented sampling and statistical approach to the large dataset of AMS specimens were utilized to define 12 AMS facies based on anisotropy degree (P) and shape (T). The AMS facies allowed a distinction of sedimentary facies ambiguous for classical methods, especially floodplain and lacustrine sediments, as well as revealing their various vulnerabilities to tectonic modification of AMS. A spatial analysis of facies showed that tuffites along with lacustrine and swamp deposits were generally restricted to marginal and southern parts of the basin. Significant deformations were noticed at basin margins and within two intrabasinal tectonic zones, which indicated the tectonic activity of the Pieniny Klippen Belt after the Middle Miocene. The large southern area of the basin recorded consistent N-NE trending compression during basin inversion. This regional tectonic rearrangement resulted in a partial removal of the southernmost basin deposits and shaped the basin’s present-day extent.

Sedimentary environment of the Early Pleistocene Gravels of the Edfu Formation from the Saqqara archaeological site (Egypt) – preliminary results

Abstract A gravel horizon is preserved in several locations within the world-wide known archaeological site in Saqqara (northern Egypt). It is characterized by a variable thickness, composed of coarse, quartz, quartzitic and flint pebbles, and considered to correspond to gravels of the Edfu Formation, deposited in the Early Pleistocene by the early phase of the Nile development (Protonile Phase). This relatively short (ca. 200 ka) and at the same time very dynamic period of Protonile activity during the Edfu Pluvial is one of the most poorly recognized hydrological-climatic episodes of the Quaternary in north-eastern Africa. This paper is focused on the preliminary sedimentological-petrographic characteristics of these deposits and an attempt to indicate their source areas as well as mechanisms of transportation and deposition in the context of Pleistocene pluvial episodes.

Ground Penetrating Radar and sedimentological investigations of quartz-glauconite sands in the Lubartow area (south-east Poland)

The study area is situated in Nowodwor-Piaski village (near Lubartów city) about 170 kilometers south-east from Warsaw (Central Poland), where Ground Penetrating Radar (GPR) surveys and outcrop investigations were conducted during an extensive open-pit mining of the Paleogene quartz-glauconite sands. The study was based on 29 GPR profiles and 12 sediment samples and generated a high resolution data set of lithofacies and ground penetrating radar profiles. Sedimentary analyses (the granulometric composition of deposits, lithofacies) followed the GPR studies. All GPR profiles were collected with 250 MHz shielded antenna. The results show that the sediments produce characteristic radar facies which can be observed in excavation. In studied sediments iron oxides and hydroxides are present they are either spread in sands or form iron horizons. The iron oxides and hydroxides have much better water retention capacity than quartz grains, which in turn affects the amplitude of the GPR signal. When they form layers they are clearly visible in GPR profiles.