Pleistocene Section Research Articles

Evaluation of geomagnetic relative palaeointensity as a chronostratigraphic tool in the Southern Ocean: Refined Plio-/Pleistocene chronology of IODP Site U1533 (Amundsen Sea, West Antarctica)

International Ocean Discovery Program (IODP) Expedition 379 to the Amundsen Sea margin of West Antarctica recovered drill cores at two sites spanning the Latest Miocene–Holocene interval with the aim of reconstructing past West Antarctic Ice Sheet dynamics. The recovered Plio-/Pleistocene sediment sequences offer an opportunity to apply and test different dating approaches in an Antarctic deep-sea drift setting, where the records are nearly continuous and unaffected by scouring of icebergs or grounded ice. Here, through palaeomagnetic analysis of continuous u-channel samples and application of X-ray fluorescence (XRF) scanning, we revise the IODP Exp. 379 Site U1533 age model for the uppermost Pliocene and Pleistocene composite interval (0.0–2.9 Ma). We first refine the magnetostratigraphic age model with high-resolution u-channel analysis and interpreted directional data. Consistent with shipboard results, all major geomagnetic polarity chrons and subchrons are identified in the Pleistocene section. The new high-resolution u-channel dataset also allows us to identify a geomagnetic polarity excursion at ∼884 ka (interpreted as the Kamikatsura excursion) and another excursion at ∼2734 ka with confidence (potentially the Porcupine excursion). Based on the improved polarity stratigraphy, we then develop two new highly resolved age models for Site U1533 using: (i) barium enrichment cycles identified in XRF scanning data, and (ii) geomagnetic relative palaeointensity (RPI). In our first age model, we correlate cyclic variations in sedimentary barium enrichment, inferred to represent changes in export productivity, to glacial‒interglacial cycles of the Lisiecki and Raymo (2005) benthic foraminiferal oxygen isotope (δ18O) stack (LR04). Nearly all Pleistocene Marine Isotope Stages (MIS) are interpreted to be present in the barium enrichment record of Site U1533, assuming simultaneous changes in Antarctic sea-ice extent/local export productivity and global oxygen isotope stratigraphy. We then construct the second, independent age model using the Plio-/Pleistocene RPI record developed for Site U1533, which represents the longest (nearly) continuous RPI record currently available for the Antarctic margin. Comparison of the two, independently derived age models shows a variable offset, on average ± 12 kyr, with the RPI-based ages consistently older than the barium-based ages in the interval from 1.9 to 2.9 Ma and then consistently younger from 0.0 to 1.9 Ma. We interpret these offsets to result from a combination of lock-in depth effects in the younger interval (due to the relatively low sedimentation rates at this site, ∼2 cm/kyr), temporal offsets between global δ18O changes in the deep ocean and productivity response on the Antarctic margin, and/or systematic miscorrelation in the construction of the two age models. Finally, we construct a hybrid age model for the Pleistocene section of Site U1533 by combining a mixture of RPI- and barium-based age tie points that are deemed to be robust. The Site U1533 RPI record is then used, together with other Southern Ocean RPI records, to construct an Antarctic RPI stack (designated as ‘ANT-1600’) for the interval 0.0–1.6 Ma. Although sedimentation rates at two-thirds of the sites selected for the stack are lower than 10 cm/kyr, the new ANT-1600 stack is strongly coherent with the SINT-2000 RPI stack (Valet et al., 2005) on time scales of ∼20–200 kyr, allowing for its use as a regional RPI reference curve in future studies. Overall, we demonstrate that RPI at Antarctic margin/Southern Ocean sites provides a viable and valuable independent dating method for application to Plio-/Pleistocene Antarctic sediments.

Inland Record of the Last Interglacial Maximum in the Western Mediterranean: Revealing the Aljezares Pleistocene Basin (Alicante, SE-Spain)

The search for a continuous continental record of interglacial periods in semi-arid regions is problematic due to the absence of stable and continuous sedimentary systems over time in this type of climate. In this work, a relatively stable basin is described and analyzed during the last interglacial period in a semi-arid region of the western Mediterranean. For this purpose, a geomorphological, stratigraphic and sedimentological study has been carried out, with dating through 230Th. A semi-endorheic Pleistocene section has been identified, with two units that correspond to a fluvial-lacustrine system (unit P1) and an alluvial system (unit P2). Unit P1 has been dated to the MIS 5e interglacial episode. A framework for future studies is described, in which the Aljezares Pleistocene basin can be considered as a possible source of paleoenvironmental and paleoclimatic information in semi-arid regions from the last interglacial period.

Early Pliocene otolith assemblages from the outer-shelf environment reveal the establishment of mesopelagic fish fauna over 3 million years ago in southwestern Taiwan

Understanding the diversity of deep-sea fish fauna based on otoliths in the tropical and subtropical West Pacific has been limited, creating a significant knowledge gap regarding regional and temporal variations in deep-sea fish fauna. To address this gap, we collected a total of 122 bulk sediment samples from the Lower Pliocene Gutingkeng Formation in southwestern Taiwan to reconstruct the otolith-based fish fauna. Using planktonic foraminiferal biostratigraphy, we determined the age of the samples to be 5.6 to 3.1 Ma. A total of 8314 otoliths were assigned to 64 different taxa from 33 families, including the discovery of one new genus, Gutingichthys gen. nov., and three new species: Benthosema duanformis sp. nov., Benthosema parafibulatum sp. nov., and Gutingichthys changi sp. nov. Comparisons with other regional otolith-based assemblages highlighted the exceptional diversity of our collection, making it the most diverse fossil fish fauna reported from Taiwan to date. Otolith diversity analysis revealed very few taxa were dominant in the assemblage, particularly the mesopelagic Myctophidae, with a wide variety of minor taxa. The co-occurrence of shallow-water elements suggests episodic storm events as a potential source. The predominance of deep-sea and oceanic fishes indicated an outer-shelf to upper slope environment, resembling the modern outer-shelf and upper slope fish fauna in the region. Our findings suggest an early establishment and persistent presence of the mesopelagic fish community since the Early Pliocene. Further investigations of the Upper Miocene and Pleistocene sections of the Gutingkeng Formation would provide valuable insights into the evolution of deep-sea fish fauna in the area.

Early Middle Weichselian in the White Sea and adjacent areas: Chronology, stratigraphy and palaeoenvironments

The paper presents the lithological and chronometric data (15 new and 9 earlier published dates) obtained in 2018–2020 on the Upper Pleistocene sections along the Terskiy and Zimniy Coasts of the White Sea. Focused on the Lower Weichselian (MIS 5d-a) and lower Middle Weichselian (MIS 4) sediment successions, the marine and glacial events are discussed. Marine environment was reconstructed in the White Sea basin, and water exchange between Barents and White Seas via Gorlo Strait. In the presented sedimentary succession, the sandy units dated to 72–66 ka and 63.5–53.5 ka on the Terskiy Coast and to 61–52 ka on the Zimniy Coast were associated with the Mezen marine transgression. Glacial event during MIS 4 is suggested in the north-easternmost shore of the White Sea, where the Barents Ice Sheet expanded from the Kara and Barents Seas shelf and reached the eastern coast of the Mezen Bay. The Terskiy Coast (southern Kola Peninsula) seems to be affected by local glacial sheet during the early Middle Weichselian.

Quaternary stratigraphy and paleoenvironmental evolution of the Ningbo Coastal Plain revealed by core Z02.

The Quaternary sediment in the Ningbo Coastal Plain was the deposit due to sea-land interaction, which recorded information of past climate changes. The region is therefore an ideal area to study paleoclimate changes and sedimentary characteristics. We determined the stratigraphic division and paleoenvironmental evolution based on 14C and paleomagnetic dating, along with detailed analyses of lithology, pollen assemblage, foraminifera and ostracodes assemblage, and grain size of sediment in core Z02 located in the southeastern Ningbo Coastal Plain. The results showed that the boundary between the Holocene and Upper Pleistocene in the core Z02 record was at 30.5 m, the boundary between the Upper and Middle Pleistocene was at 82.65 m, and the boundary between the Quaternary and Lower Cretaceous was at 90 m. The Middle Pleistocene section of the core contained few sediments, while the Lower Pleistocene section was completely missed. During the late Pleistocene, the hydrodynamic conditions experienced energy levels of medium to medium low to medium, and sedimentary facies changed from alluvial lake to overbank to river to lake to alluvial lake to lake to overbank. During the Holocene, the hydrodynamic changes experienced energy levels of medium low to low to medium, and the sedimentary facies changed from shoreland to shallow sea to shoreland lake. The Ningbo Coastal Plain had experienced tectonic uplift, weathering and erosion stage in the Early and Middle Pleistocene, from warm and humid to dry in the Late Pleistocene, and from warm and humid to dry and cool in the Holocene, as revealed by the core Z02 record. This study provided useful information in investigating past environmental changes in the subtropical coastal region of eastern China.

Pleistocene palaeoenvironments in the Lower Volga region (Russia): Insights from a comprehensive biostratigraphical study of the Seroglazovka locality

There are many Middle-Upper Pleistocene outcrop sections in the Lower Volga region (Caspian Lowland, Russia) in between cities of Volgograd and Astrakhan. The present study focuses on the Seroglazovka locality, which is among the most famous key sites within the Lower Volga region. The Seroglazovka locality is of great regional interest, because of its clear exposure of genetically variable Middle and Upper Pleistocene deposits containing diverse complexes of fauna and flora. Even though the Seroglazovka locality was studied by many researchers, the diversity and along-strike variability of the depositional facies often makes the stratigraphic interpretation challenging. In this study, we performed an extensive and integrated study of the Seroglazovka locality including detailed outcrop mapping with lithological description, as well as diverse biostratigraphy analysis and OSL-dating. In addition to outcrop data, we used recently obtained borehole data near the Seroglazovka locality, which cover almost the entire Quaternary interval. This multidisciplinary approach permitted us to confidently stratify the Quaternary interval of the Seroglazovka locality into a series of regional horizons and subhorizons including the Akchagyl, Apsheron, Tyurkyan, Baku, Khazar and Khvalyn. Furthermore, we correlated the interpreted section to the adjacent parts of the Caspian Lowland and the Regional Stratigraphic Scale. Our results allowed us to determine the main Pleistocene palaeoenvironments and their evolution within the study area. Our findings are important to understand the processes, which led to the modern faunistic composition of the Lower Volga region, and to clarify the role of glacial refugia in the settlement of certain species and further colonization of water basins and land areas with habitable environments. Finally, we suggest the Seroglazovka locality as the key reference Pleistocene section for the Lower Volga region.

Stratigraphy and the small mammal fauna of the Late Pleistocene sections in the south of the middle reaches of the Volga River

Two Pleistocene sections in the middle reaches of the Volga River – Spasskoe and Yagodnoe – have been described in details and analyzed, small mammal remains being recovered and identified. The fauna includes remains of open landscape species: Eolagurus luteus (Eremin and Moloskovsky, 1981), Lagurus lagurus Pallas, 1773, Lasiopodomys (Stenocranius) gregalis (Pallas, 1779) and others. Bone remains of a tundra species – collared lemming Dicrostonyx sp. were found in the Spasskoe section. No forest species are present in the sequence, nor remains of water vole Arvicola. The species richness of the faunas is rather low, which may be related to insufficient amount of material or to a specific climate. Such low species richness is typical of the periglacial faunas of the Pleistocene. The authors of recent article attribute the third Volga terrace to the Late Pleistocene refer usually to the 3rd terrace deposits in the lower reaches of the Volga where the Caspian Upper Khazarian (Hyrcanian) layers are found at the base of the sequence. The rodent molar morphology permits to date fauna to the beginning of the Late Pleistocene (to the early stages of the Valday glaciation) and to reconstruct periglacial steppes widely distributed in the Volga middle reaches at that time.

High‐resolution seismic velocity field estimation techniques and their application to geohazard, lithology and porosity prediction

ABSTRACTSeismic velocity is an attractive parameter for geohazard interpretation, pore pressure analysis, play and prospect evaluations, and other geological studies, but ordinary seismic processing velocities often do not have a good enough resolution. We adapt a dynamic time warping algorithm to estimate geologically reasonable high‐resolution velocities from average‐quality seismic data that can be used for geohazard analysis based on 3D seismic data. To predict free gas and/or excess pore water pressure in thin shallow layers, we use velocity inversion. It is a method for simultaneous inversion of velocity data to geological attributes. It runs in the depth domain, uses a background velocity model for balancing of input velocities to wells and a normal compaction trend model to simultaneously estimate lithology, pore pressure and net apparent erosion attributes, while porosity is calculated from a sandstone–porosity relationship. The overall workflow is applied for geohazard analysis at two marine sites. The first example is a deep‐water one from the Norwegian Sea, where thin and possibly overpressured or gas‐filled layers are identified in the Pleistocene section. The second example is in a region with limestone‐dominated lithology, where thin overpressured shales can cause severe drilling problems. In both examples, the thicknesses of the layers prone to geohazards are estimated to be about half of the wavelength. Dedicated high‐resolution velocity estimations, such as those obtained through the proposed workflow with dynamic time warping, applied to standard 3D seismic data and followed by dedicated velocity inversion routines, are, therefore, a necessity for proper geohazard assessment.

DEVELOPMENT OF VEGETATION AND SOILS IN THE CENTRAL PART OF THE PRYDNIPROVSKA UPLAND DURING THE SHYROKYNE AND MARTONOSHA STAGES OF THE EOPLEISTOCENE – EARLY NEOPLEISTOCENE

New materials on reconstruction of vegetation and soil cover of the central part of the Prydniprovska Upland during the Shyrokyne and Martonosha stages are presented. For the first time paleofloristic reconstructions were performed not only at the level of paleogeographic stages but also sub-stages for the study region. The importance of a comprehensive study of the deposits of the Shyrokyne and Martonosha climatoliths in connection with the discussion of the Matuyama-Brunes boundary in the continental Pleistocene section of Ukraine is substantiated. The micromorphological characteristics of the Shyrokyne and Martonosha soils were significantly supplemented. The lithological characterization of the Shyrokyne and Martonosha climatoliths is given, and attention is paid to the features of the structure of the studied pedohorizons within this region. The results of detailed micromorphological studies of the Shyrokyne and Martonosha soils of the basic section of the Pleistocene sediments near Raygorod village are presented. Changes in the vegetation composition of the study region during the Shyrokyne and Martonosha stages are retraced. A comparative analysis of the composition of the Shyrokyne and Martonosha dendroflora is performed. The arguments in favor of the attribution of the Shyrokyne climatolith to the Eopleistocene in the Modified Stratigraphic Scheme of Quaternary deposits are given. The general and distinctive features of vegetation cover and soils of the Shyrokyne and Martonosha stages are determined.

New pleistocene key section Ulan-Zhalga of the Western Transbaikalia

The currant paper presents the preliminary results of the multidisciplinary study of the new Pleistocene section Ulan-Zhalga (51°29′40.75″ С, 107°20′18.11″ В) discovered in the Western Transbauikalaia in 2017. On the base of the paleontological, paleomagmetic, and lithological data the early, middle and late Pleistocene sediments were recognized in the section. The analysis of the rich small mammal fossils resulted in to trace the paleoenvironmental and climatic changes in the region during the Quaternary. The unique alternation of the 19 faunistic horizons and 11 fossil soils in the whole section, the high correlation of the paleomagnetic and paleontological data allow us to refer the studied section Ulan-Zhalga to addition new late Cenozoic Key section of the south Eastern Siberia. The new geological and paleontological data would be important for paleogeographical reconstruction and biostratigraphic analysis.

A history of the modern Aral Sea (Central Asia) since the Late Pleistocene

The catastrophic demise of the Aral Sea in the late twentieth century has stimulated significant international efforts to understand the geological, hydrological, and climatological controls on lake level at timescales ranging from years to millennia. Here we extend this time range to the Late Pleistocene with sedimentological, chronological and paleontological results from a core that dates from ca. 17.6 kyr cal BP. To our knowledge, this Aral Sea core (B-05-2009) is the oldest directly-dated sediment record with multiple late Pleistocene 14C dates currently available from the region. The core shows that the modern Aral Sea formed at least as early as the end of the Last Glacial Maximum. The main source of water was most likely glacial meltwater from the Tian Shan, Pamir, and other distant mountain systems in the modern day Aral Sea watershed, carried by the Syr Darya and Amu Darya rivers. The Late Pleistocene section of the core contains ostracods and foraminifera throughout, providing evidence that the lake supported life since its inception. Our chronology suggests a relatively high average sedimentation rate at the onset of lake development, and a significant sedimentation hiatus around the time of the Pleistocene/Holocene boundary.

РАЗРЕЗЫ ВЕРХНЕГО НЕОПЛЕЙСТОЦЕНА ПРИТЕЛЕЦКОГО РАЙОНА ГОРНОГО АЛТАЯ (ЛИТОЛОГИЯ, ПАЛИНОЛОГИЯ, МИКРОФАУНА)

A number of Pleistocene sections located in the Priteletsky region of the Gorny Altai were studied in connection with the geological survey. In order to determine the age of the sediments and the features of their formation, their detailed lithological and micropaleontological studies were conducted. For the section Turochak and Malaya Chile obtained new data of absolute age. Almost all sections are dated to the second half of the Late Pleistocene, during which the taiga landscapes were repeatedly replaced by steppe ones.

Disturbed Stratification in Late Pleistocene Sediments of the Khibiny Pluton (Kola Peninsula)

Abstract —The paper presents a description of three Late Pleistocene sections within the Khibiny pluton, outcropping on the proximal slope of the Kukisvum morainic ridge, a fluvioglacial terrain in the valley of the Kukisiok River, and a glacial complex in the valley of the Vuonnemiok River. Various small disturbances of the primary stratification were found in the first two sections. These structures do not form horizons sustained along the strike and are associated with the top of sand–silt sediments with horizontal or wavy bedding of shallow lacustrine genesis. They form small wavy bends, ‘tongues”, ovoids, and flexural microfolds that could not be preserved at the bottom of the basin and, consequently, formed after overlapping deposits accumulation. Analysis of the cross bedding of the coarse clastic deposits of the fluvioglacial terrace has allowed us to relate its formation to north-to-south glacial water discharge along the trough valley of the Kukisiok River. In the glaciolacustrine varve clays of the third section (the Koashva open pit), extended horizons of plicative disturbances 0.5–2 m in thickness and 300 m in length were studied. The soft-sediment deformations are covered with an unstructured horizon composed of coarse grains dispersed in sand–silt matrix, which means that the deformation was caused by either a glacial flood or a mudflow. The study has revealed no signs of seismic liquefaction during the formation of the folded structures. The relevance of the performed study is determined by the fact that it has become possible not only to clarify the formation conditions of the Quaternary Khibiny deposits but also to develop the objective criteria for determination of the soft-sediment deformation structures associated with thixotropic effects in weakly consolidated sediments. Similar structures are sometimes regarded as seismic convolutions, which can lead to unjustified overestimation of the regional seismic hazard level.

Hemipelagic and turbiditic deposits constrain lower Bengal Fan depositional history through Pleistocene climate, monsoon, and sea level transitions

The Bengal Fan contains the most complete record of Himalayan climate and tectonics. As the largest fan system of the world it is fed by the Ganges-Brahmaputra river systems. International Ocean Discovery Program (IODP) Expedition 354 cored seven sites along an east-west core transect at 8°N in the lower Bengal Fan. We studied the Pleistocene sections of these sites to provide constraints on the depositional history of the last 1.25 Ma. Low-resolution bio- and magnetostratigraphic constraints identified two regionally-extensive hemipelagic units and intercalated turbidite deposits that provide a chronostratigraphic framework for the 320 km transect. Using a combination of lithostratigraphy and sediment physical properties that vary on orbital timescales, we tuned high-resolution data sets to the LR04 benthic δ18O isotope stack to obtain new constraints on the timing of depositional changes.Above the underlying Unit 1, which consists of Early to Middle Pleistocene turbiditic deposits, we divide four more units for the last 1.25 Ma: Unit 2, a Middle Pleistocene hemipelagic layer deposited at all sites from Marine Isotopic Stages (MIS) 37 to ∼17 (∼1.24–0.68 Ma) during the entire time of the Mid-Pleistocene Transition, when the Bengal Fan depocenter must have been distal to our transect; Unit 3, mostly turbidites with some intercalated hemipelgic sediments deposited from ∼MIS 16–∼13 (∼0.68–0.48 Ma), with sandy lithologies only found at the easternmost site on the west flank of the Ninetyeast Ridge; Unit 4, massive turbiditic sediments that started to dominate deposition with the Mid-Brunhes Transition (∼MIS 12) until MIS 7/8 (∼0.48–0.25 Ma), when the channel-levee system was focused east of the 85°E basement ridge at 8°N; and Unit 5, a Late Pleistocene hemipelagic layer at the top that spans MIS 7/8–1 (∼0.25 Ma to present) while the turbidite deposition was focused west of the 85°E basement ridge at 8°N. We find evidence that, on these timescales, deposition across the lower Bengal Fan changed with the evolution of Pleistocene climate, monsoon and sea-level history and hence responded to external controls on sediment accumulation and fan architecture rather than only fan-internal, autocyclic mechanisms.

Deposition in a changing paleogulf: evidence from the Pliocene–Quaternary sedimentary succession of the Nile Delta, Egypt

Sedimentary complexes of ancient gulfs provide valuable information about paleoenvironmental dynamics. The study of several Pliocene–Pleistocene sections allowed reconstruction of the regional stratigraphical framework in the southwestern fringes of the Nile Delta. The Kafr El-Shiekh, the Gar El-Muluk, and the Kom El-Shelul formations of the Zanclean Age and the Wastani Formation of the Piacenzian Age constitute the Pliocene sedimentary succession in the study area. The establishment of 11 facies types related to 5 facies associations coupled with the results of the stratigraphical study indicate the existence of a paleogulf corresponding to the modern delta and lower valley of the Nile. This Nile Paleogulf appeared and reached its maximum spatial extent in the beginning of the Pliocene. Then, it retreated gradually and disappeared before the end of this epoch when alluvial sedimentation reestablished. There was significant flux of siliciclastic material to the study area. The Zanclean Flood in the Mediterranean Sea allowed marine incursion in the study area where the river valley incised during the precedent Messinian Salinity Crisis. Regional tectonic uplift and filling of the accommodation space with siliciclastic material from the eroded land were the main controls on the paleogulf evolution. Strengthened glaciation triggered global sea level fall, and alluvial deposition dominated the study area in the late Pliocene–Pleistocene.

Late Quaternary Paleoenvironmental Reconstruction, Using Benthic Foraminifera and Ostracoda, of Marine Sedimentary Beds On the Southern Coast of Laizhou Bay, Bohai Sea, China

Abstract Extensive studies of Quaternary transgressions have been conducted in Bohai Sea, but debates continue regarding the sedimentary evolution and timing of transgressions, especially in the Pleistocene section. Benthic foraminifers and ostracodes from three boreholes (GK138, GK111, GK95) at Laizhou Bay, Bohai Sea, were utilized to interpret the paleoenvironments of deposition and elucidate the coastal response to global sea-level changes since the late Quaternary. Benthic foraminiferal species identified included 32 species from 15 genera; ostracodes included 28 species from 16 genera. Three marine sedimentary beds were recognized based on sedimentary characteristics, down-core changes in environmental proxies (benthic foraminifers and ostracodes), accelerator mass spectrometry (AMS) 14C, and optically stimulated luminescence (OSL) dates. These three beds were interpreted as: marine sedimentary bed 3 (M3), deposited in the late-middle Pleistocene; marine sedimentary bed 2 (M2), deposited during the late Pleistocene; and marine sedimentary bed 1 (M1), deposited during the Holocene. Three microfossil assemblages were identified, all indicating nearshore conditions. Assemblage III indicated a fluvially influenced or paralic environment during a relatively small-scale late-middle Pleistocene transgression that produced bed M3. Assemblage II indicates an intertidal-subtidal environment where bed M2 was deposited during the late Pleistocene transgression. Assemblage I indicates somewhat more marine influence in a subtidal environment where bed M1 was deposited during the Holocene marine transgression.

Problems of magnetostratigraphy of Pleistocene loess-soil deposits of the South of Ukraine

Main principles of magnetostratigraphy, paleomagnetic method of measurement and its applying in Quaternary stratigraphy have been set forth. Results of Matuyama-Brunhes (M/B) boundary detection in loess-soil sediments of Ukraine and other territories given in the previous studies are presented. Attention has been paid to contradictions in determination of M/B boundary position and episodes of inverse polarity within Brunhes chron according to the data of different authors. The situation is notably shown on Roxolany section in West Black Sea region as an example. One of the reasons there can be increase of magnetometric equipment precision and quality of measurements which exclude the bias effects nowadays. Another reason is the contradictions in stratigraphic partition of sections that are located even within the same loess province. We have got informative data that allow to predetermine M/B boundary position in Roxolany section at 46.6 m depth between Lubny and Martonosha soil horizons which conforms to modern point of view of Ukrainian stratigraphers and corresponds to previous investigations of Dolynske section (M/B boundary was found at the level of Martonosha horizon). Further complex paleomagnetic studies of Pleistocene sections of Ukraine will help to revise and correlate still conflicting magnetostratigraphic charts.

Aviat: a Lower Pleistocene shallow gas hazard developed as a fuel gas supply for the Forties Field

Abstract The search for a gas source near to Apache's Forties Field in the North Sea was motivated by the prediction of an ever-increasing fuel gas shortfall as the field oil rate declined. The Central North Sea is well known for a large number of shallow gas hazards in the Pleistocene section that have historically caused blowouts during exploration and development. These gas accumulations typically show up as small bright anomalies on seismic data. In 2009, a large gas anomaly was identified to the east of Forties, and the Aviat Field was discovered in 2010 when exploration well 22/7-5 was drilled. The Aviat Field reservoir is interpreted to be a subaqueous glacial outwash fan, consisting of silt-grade, rock flour material, deposited in front of a grounded ice sheet in some 400 m of water. Aviat sits on an overcompacted silty mudstone that was deformed by this ice sheet – the Crenulate Marker. The distribution of this horizon implies that the Early Pleistocene ice sheet covered at least the northern half of the UK North Sea. Although the Aviat reservoir is thin (2–9 m thick), the well tests, pressure profiles and geophysical response demonstrate that the reservoir is well connected, extensive (over 35 km 2 ) with high deliverability (up to 18 MMscfd achieved). Aviat was sanctioned in 2014 for development as a fuel gas supply for the Forties Field, with first gas achieved in July 2016.

BENTHIC FORAMINIFERA ASSOCIATED WITH THE ZOOXANTHELLATE CORAL CLADOCORA IN THE PLEISTOCENE OF THE KOS ISLAND (AEGEAN SEA, GREECE): SEA LEVEL CHANGES AND PALAEOENVIRONMENTAL CONDITIONS

A Pleistocene section, cropping out in the northern Kos Island has been selected for study. The main lithology (clayey sands, sandy marls) of the section is interrupted by a prominent Cladocora bank which allows a proper extraction of its faunal contents and identification at species level. The evaluation of benthic foraminiferal assemblages from this bank helps to determine the range of the environmental controls in sedimentation. The foraminiferal assemblage is related to a relatively high supply of organic material and rather strong current intensities in water depth of the coral growth. We suggest that the fossil reef of Cladocora grew in coastal waters characterised by a marked seasonality, with periodical inputs of terrigenous sediments, moderate turbidity and higher temperature than today. Such results, although preliminary, suggest that Cladocora together with benthic foraminifera could be reference species for future work on changing Mediterranean climate and sea level.

Two Pleistocene sections in south‐western Donegal and their relation to the last glaciation of the Glengesh Plateau

Abstract not available...