Quaternary Sequences Research Articles

THE SIGNIFICANCE OF THE PLEISTOCENE AQUATIC FAUNA OF MOLLUSKS FOR THE REPRODUCTION OF SEDIMENTATION CONDITIONS IN WESTERN UKRAINE

The territory of Western Ukraine is characterized by the development of a wide range of genetic types of continental formations. The Carpathian Mountain Country (properly the Carpathians, East Carpathian Foreland, and Transcarpathia) and the highly fragmented parts of the Volhynia and Podolia Uplands are characterized by a special diversity. The time range of their formation is vast – from the Early Pleistocene to the present. The complexity of the structure of the Quaternary sequence gives rise to discussions about the origin of some components of anthropogenic accumulations. Despite the fact that most of the challenging issues have already been resolved, we find debatable information in the works of some researchers of the 20th and even the 21st centuries about the aqueous origin of the thick sequences of anthropogenic sediments covering the terraces of the Dniester and Dnieper basins. The researchers use many methods to solve the issue of the deposit genesis. Some of them are based on the study of paleontological (including paleomalacological) remains, which are often found in both aqueous (alluvial, lake, swamp) and aerial (primarily loess) formations. Malacofauna has been used since the second half of the 19th century to determine the age, conditions of formation, and origin of the deposits. To establish the origin of sediments we have used the mollusk fauna in this work, which can be often found in the formations of the studied territory. The interpretation of the fauna is debatable in the sections where several genetic types of formations are exposed, primarily alluvial and eolian–deluvial loess. This type of combination of deposits is found in outcrops on the numerous terraces of the Dniester and the terraces of its East Carpathian Foreland’s and Podolia tributaries. The results of the research obtained by us using paleomalacological studies correlate well with data obtained using other methods. Such methods include actual field observations, as well as lithological, palaeopedological, paleontological (study of fossil mammals, fish, spores, and pollen), archaeological, and other methods. The results presented in this work made it possible to establish the genesis of some components of polygenetic complex strata, as well as testify to the effectiveness of the applied research method. Keywords: anthropogen; malacofauna; alluvium; loess; paleogeography; Podolia; East Carpathian Foreland.

Identification of Milankovitch sedimentary cycle in Fengcheng Formation, Mahu depression: a case study of well Maye 1

The sedimentary cycle of Fengcheng Formation in Junggar Basin changes rapidly and is difficult to identify. The low classification accuracy of high-frequency fine-grained sedimentary cycles restricts the exploration of unconventional shale oil and gas. Full-interval coring of well Maye 1 provides a solid foundation for small-layer research. In this paper, the high-frequency sedimentary cycle of Milan kovitch in Fengcheng Formation is studied by means of spectral analysis and wavelet transform, and the shale sweet spot is identified. The long period of eccentricity of 405ka, short period of eccentricity of 100ka and long period of axis slope of 42736a can be used as semi-quantitative basis for the classification of the fourth, fifth and sixth sequences. The Fengcheng Formation can be divided into 2 quaternary sequence cycles, 9 quaternary sequence cycles and 16 quaternary sequence cycles. A long period of eccentricity of 405ka can identify large-scale lake recessional and recessional, and there is a maximum lake flooding surface in the middle of the second Fengcheng Formation, which corresponds to high abundance of organic matter and high hydrocarbon generation potential. The 100ka short period eccentricity can identify the sweet spot layer, and there are 8 sweet spots in the well Maye 1, which is consistent with the results of nuclear magnetic interpretation. The research results provide a semi-quantitative basis for the classification of high-frequency sedimentary cycles and the identification of sweet spots of Fengcheng Formation in Mahu Sag, Junggar Basin.

On the radiometric significance of glauconies in studies of provenance: An example of the quaternary marine sequences of the Rio Grande Cone (Pelotas basin, southern Brazil)

The sediments of the Pleistocene-Holocene marine sequences of the Rio Grande Cone (RGC) (offshore Pelotas Basin, southernmost Brazilian Margin) are dominantly composed by muddy facies with thin interspersed sandy layers containing abundant very fine-to coarse green grains, heavy minerals assemblage, shards and planktonic foraminifera. These components contribute for a better understanding of the RGC filling during the Pleistocene-Holocene. However, the aim of this work was focused in the radiometric dating of the green grains as tool for provenance studies in marine sedimentary sequences. Based on Electron Microprobe, Scanning Electron Microprobe, Transmission Electron Microprobe and optical analysis the green grains occur as: (01) yellowish-green grains with smooth surfaces, low K2O and moderate Fe2O3 contents, (02) pale green grains with surfaces slightly fractured with moderate K2O and Fe2O3 contents, and (03) dark green grains characterised by fractured (cracked) surfaces and high of K2O and Fe2O3 contents. These characteristics classified them as glauconitic minerals ranging from glauconitic smectite to glauconitic mica (glauconite) indicating the first (nascent) and intermediate (slightly-evolved and evolved) stages of the glauconitization process. K–Ar radiometric dating indicated ages from 33.2 ± 0.99 to 6.69 ± 0.54 Ma corresponding from Rupelian Stage (Oligocene) to Messinian Stage (Miocene) to these grains. Considering these glauconitic grains within a Quaternary sequence, an allochthonous (detrital) origin was attributed whose probable source areas were older sedimentary sequences exposed on the seafloor along fold-and-thrust belts related to the gravitational collapse of the RGC depocentre. After eroded the glauconitic minerals probably were distributed by countourite currents and deposited within the Quaternary deposits of the RGC.

The Quaternary sequence of the Nahr el Kebir, NW Syria: An important repository for evidence of Palaeolithic occupation and landscape evolution in the eastern Mediterranean

The third largest river in Syria, the Nahr el Kebir has a well-preserved record of river-terrace deposits that have produced substantial Palaeolithic artefact assemblages both from within the terrace deposits and from the land surfaces above and around them. At the Mediterranean coastline, the fluvial gravels interdigitate with raised shoreline terrace deposits, providing an insight into the temporal and climatic relations of both of these important geomorphological and morphostratigraphical archives, as well as their relationship with each other. New research is reported here on the Pleistocene geology and geomorphology of the Nahr el Kebir and the associated Palaeolithic archaeology, the latter having been reinterpreted based on reassessment of museum collections arising from earlier detailed work. Field visits revealed an additional, hitherto unrecognized low-level river terrace, whereas one of the previously recognized Palaeolithic levels can be shown to coincide with slope deposits that armour hilltops rather than representing a genuine fluvial formation. The new understanding of these geomorphological and sedimentary archives supports ideas that this corner of the Mediterranean has experienced unusually rapid uplift during the recent Quaternary, as a result of which the local rivers, including the Kebir, have deepened their valleys rapidly. Consequently, only the recent part of the Quaternary is recorded in the Kebir system and the ages envisaged previously for the terrace deposits and the Palaeolithic artefact assemblages were considerable overestimates in many cases, a finding that has significance for their correlation with those from the wider region. Reassessment of the Palaeolithic archaeology suggests a settlement history initially dominated by groups using handaxes, alongside simple core working (0.5–0.3 Ma), followed by a major change with the appearance of Levallois core working alongside handaxes, marking the transition to the early Middle Palaeolithic.

The autocorrelation of a class of quaternary sequences of length pq with high complexity

Recently, a class of quaternary sequences with period pq, where p and q are two distinct odd primes introduced by Zhang et al. were proved to possess high linear complexity and 4-adic complexity. In this paper, we determine the autocorrelation distribution of this class of quaternary sequence. Our results indicate that the studied quaternary sequence are weak with respect to the correlation property.

A Quaternary sequence of terrestrial molluscs from East Africa: a record of diversity, stability, and abundance since Marine Isotope Stage 5 (78,000 BP)

A Quaternary sequence of terrestrial molluscs from East Africa: a record of diversity, stability, and abundance since Marine Isotope Stage 5 (78,000 BP)

The 4-adic complexity of quaternary sequences with optimal odd-periodic autocorrelation magnitude

The 4-adic complexity of quaternary sequences with optimal odd-periodic autocorrelation magnitude

Pedostratigraphic age model for Devonian red beds of NW China

Detrital zircon geochronology has been used to determine provenance, but also gives maximum depositional ages that can constrain other forms of geochronology, such as magnetostratigraphy and pedostratigraphy. Pedostratigraphy and magnetostratigraphy correlate a series of global events by spacing or intensity in a fashion comparable with a commercial barcode. The Late Devonian Shaliushui Formation of NW China is poorly fossiliferous, but shows spikes in magnetic susceptibility, Al/Si ratios, Rb/Sr ratios and the depth to carbonate nodules (Bk horizon) corresponding with the timing of named Late Devonian black shale horizons. By contrast, the Ti/Al ratios show only small variations, indicating little long-term change in the source terrain or in the hydraulic sorting of heavy minerals. Most of the detrital zircon ages are older than an age model from the pedostratigraphic correlation of deep calcic horizons corresponding to global atmospheric CO 2 spikes at times of black shale expansion, but one detrital zircon age converges with the pedostratigraphic depositional ages near the top of the section. Pedostratigraphy is widely used in Quaternary sequences, but can also be a basis for age models of rocks in deep time if supported by detrital zircon ages. Supplementary material: Paleosol and geochemical data, and youngest zircon ages for a section of Devonian rocks near Ciyao, Gansu, China are available at https://doi.org/10.6084/m9.figshare.c.7008192

Environmental Variability of the Northern Caspian Sea during Khazarian Epoch (Based on Drilling Data)

The objective of our work was to reconstruct transgressive-regressive events in the Northern Caspian Sea during the Khazarian epoch of its Pleistocene history to determine the natural conditions of the development of the basins and to assess their response to climate change. This work is based onstudies of the sedimentary formations of the upper part of the Quaternary sequence in the Northern Caspian Sea. The borehole was drilled in the eastern part of the depression Shirotnaya, the sea depth was 11.9 m, and the depth of drilling was 56.4 m. The core was subjected to lithological, malacological, and palynological analysis. This paper discusses the results related to the interval 56.0–26.6 m. The structure, facies-lithological, and malacological composition of the core capture three transgressive stages of the Caspian, namely the Early Khazarian, Late Khazarian, and Hyrcanian stages, separated by regressive phases. The representative spore-pollen assemblages made it possible to carry out the climatic and stratigraphic subdivision of the studied Khazarian deposits and to suggest a provisional version of the history of climatic and phytocenotic events during the sedimentation period. The results of our studies have introduced new discussion points into the paleogeography of the Northern Caspian Sea.

Improvements on the 4-adic complexity of a class of quaternary sequences

Yang and Ke proposed a new class of quaternary sequences with low autocorrelation of period pq by using the inverse Gray mapping and the pair of two generalized cyclotomic sequences (Cryptography and Communications, vol. 3, pp. 55–64, 2011). In this paper, we aim to study and determine the 4-adic complexity of this class of quaternary sequences, and our results show that the 4-adic complexity of this class of quaternary sequences is quite large, and it can reach the maximum in particular cases.

The 4-adic complexity of quaternary sequences with low autocorrelation and high linear complexity

The 4-adic complexity of quaternary sequences with low autocorrelation and high linear complexity

Symmetric 4-adic complexity of quaternary sequences with low autocorrelation and period $ pq $

Symmetric 4-adic complexity of quaternary sequences with low autocorrelation and period $ pq $

Integrated approach of sedimentary processes on paleosol and calcareous tufas in two Late Quaternary sequences in Mediterranean contexts (Southern France)

Integrated approach of sedimentary processes on paleosol and calcareous tufas in two Late Quaternary sequences in Mediterranean contexts (Southern France)

The 4-adic complexity of interleaved quaternary sequences of even period with optimal autocorrelation

The 4-adic complexity of interleaved quaternary sequences of even period with optimal autocorrelation

Investigating Multilayer Aquifer Dynamics by Combining Geochemistry, Isotopes and Hydrogeological Context Analysis

Geochemical tracers have the potential to provide valuable insights for constructing conceptual models of groundwater flow, especially in complex geological contexts. Nevertheless, the reliability of tracer interpretation hinges on its integration into a robust geological framework. In our research, we concentrated on delineating the groundwater flow dynamics in the Innisfil Creek watershed, located in Ontario, Canada. We amalgamated extensive hydrogeological data derived from a comprehensive 3D geological model with the analysis of 61 groundwater samples, encompassing major ions, stable water isotopes, tritium, and radiocarbon. By seamlessly incorporating regional physiographic characteristics, flow pathways, and confinement attributes, we bolstered the efficiency of these tracers, resulting in several notable findings. Firstly, we identified prominent recharge and discharge zones within the watershed. Secondly, we observed the coexistence of relatively shallow and fast-flowing paths with deeper, slower-flowing channels, responsible for transporting groundwater from ancient glacial events. Thirdly, we determined that cation exchange stands as the predominant mechanism governing the geochemical evolution of contemporary water as it migrates toward confined aquifers situated at the base of the Quaternary sequence. Fourthly, we provided evidence of the mixing of modern, low-mineralized water originating from unconfined aquifer units with deep, highly mineralized water within soil–bedrock interface aquifers. These findings not only contribute significantly to the development a conceptual flow model for the sustainable management of groundwater in the Innisfil watershed, but also offer practical insights that hold relevance for analogous geological complexities encountered in other regions.

The 4-adic complexity of new quaternary sequences with good autocorrelation

The 4-adic complexity of new quaternary sequences with good autocorrelation

Radial and azimuthal seismic anisotropy in NW South America: Insights into crustal deformation and mantle flow using ambient noise and surface wave tomography

We illuminate the crustal and upper mantle structure of the northwestern corner of South America by mapping radial and azimuthal seismic anisotropy. Radial anisotropy is inferred from the discrepancy between VSV and VSH polarized S-velocities in horizontally propagating Rayleigh and Love waves, respectively. First, short-period (7–35 s) phase and group velocities are estimated from ambient noise cross-correlations, and long-period (40–170 s) group velocities are determined from fundamental-mode, surface-wave trains from earthquake sources at regional and teleseismic epicentral distances. Dispersion velocities are then tomographically inverted to develop maps of group velocity variation for periods between 7 and 170 s including azimuthal velocity dependence. We observe that positive anisotropy in the upper crust is related to thick Quaternary sequences in sedimentary basins, while negative anisotropy is found beneath active volcanoes and igneous-metamorphic terrains. Negative anisotropy features observed in the lower crust beneath the Eastern Cordillera suggest the existence of sill-like intrusions that penetrate the lower crust, thus supporting underplating mechanisms. Our study reveals SW-NE oriented fast axes of azimuthal anisotropy beneath the Eastern Cordillera, which strongly suggest the presence of shear zones within the fold and thrust belt system. Notably, the fast axes align parallel to the regional faults in the area, indicating a significant role in controlling faulting processes. Finally, we observe a wide trench-parallel zone of azimuthal anisotropy beneath the Nazca Plate, the Panama Block, and the Caribbean, which we associate with subslab mantle flow.

Quaternary stratigraphy of southern Vietnam continental margin

This study investigates the stratigraphic architectures of the South Vietnam continental margin (SVCM) from the Pliocene to the recent period. We have utilized high-resolution seismic data and sediment core data to achieve this. The study reveals that the Quaternary sequences on the continental margin are bounded by composite erosional surfaces, which were formed due to sub-aerial erosion during periods of sea level fall and subsequent reworking processes during sea level rise. The Quaternary sequence can be divided into two subsequences: the Early Pleistocene and the Middle Pleistocene-Holocene. The Middle Pleistocene-Holocene sequences can be subdivided into six fourth-order sequences, each lasting approximately 100 to 120 thousand years. These sequences are well-preserved on the outer shelf at a modern water depth of around 100 to 120 meters. Seismic stacking patterns indicate that regressive deposits predominantly dominate the Quaternary stratigraphy of the SVCM. This means that sediment deposition during the Quaternary period was more pronounced during periods of sea-level fall. The outer shelf margin of the modern continental margin shows a south-to-southeastward migration of prograding clinoforms, indicating sediment progradation in these directions. The thick Quaternary regressive deposits preserved on the outer shelf are attributed to various factors. These factors include the low shelf gradient, tectonic subsidence, regional hinterland uplift, monsoon strengthening, and high sediment supply from the Palaeo-Mekong Delta during sea-level fall. The interaction of these factors facilitated the accumulation of thick sedimentary deposits during falling sea levels. The mid-late Pleistocene stratigraphy of the SVCM shows similarities to many other continental margins worldwide. These margins are mainly shaped under the influence of asymmetric 4th-order Milankovitch cycles. These cycles are driven by variations in Earth's orbital parameters and are characterized by longer phases of relative sea-level fall followed by shorter periods of stabilization and rise.

The linear complexity and 4-adic complexity of quaternary sequences with period pq

The linear complexity and 4-adic complexity of quaternary sequences with period pq

The dating and correlation of an eastern Mediterranean lake sediment sequence: a 46–4 ka tephrostratigraphy for Ioannina (NW Greece)

ABSTRACTTerrestrial archives from the Mediterranean have been crucial to expanding our understanding of past environmental variability on a range of timescales. Dating Quaternary sequences in the Mediterranean is, however, often challenging, and age models often have large chronological uncertainties. Tephra deposits can provide crucial age control for detailed environmental reconstructions on sub‐centennial timescales. Here, tephra analysis is undertaken for the first time on a sediment core (I‐08) from Lake Ioannina, northwest Greece, for the interval spanning 46–4 ka bp. Detailed visible and ‘crypto‐’ tephra analysis identifies deposits associated with explosive volcanism at Italian volcanic sources, including Campi Flegrei, Pantelleria, and the Aeolian Islands. We identify two visible tephra layers, the Campanian Ignimbrite (CI/Y‐5; ca. 39.8 ka bp) and Pantelleria Green Tuff (PGT/Y‐6; ca. 45.7 ka), as well as the Holocene Vallone del Gabellotto cryptotephra marker (VG/E‐1; ca. 8.3 ka bp). Evidence for repeated remobilisation and redeposition of CI tephra material is outlined, and the potential mechanisms and effects of sediment reworking in lake environments are examined. Bayesian modelling, which incorporates the new tephra ages with earlier radiocarbon dates, extends the I‐08 core chronology back to ca. 46 ka bp, facilitating direct correlation of the Ioannina sequence to others in the Mediterranean region.