Structural Geology (2nd edition)

<abstract xml:lang="en"><title style='display:none'>Stratigraphy and sedimentology of the Niger Delta</title>During the Cenozoic, until the Middle Miocene, the Niger Delta grew through pulses of sedimentation over an oceanward-dipping continental basement into the Gulf of Guinea; thereafter progradation took place over a landward-dipping oceanic basement. A 12,000 m thick succession of overall regressive, offlapping sediments resulted that is composed of three diachronous siliciclastic units: the deep-marine pro-delta Akata Group, the shallow-marine delta-front Agbada Group and the continental, delta-top Benin Group.Regionally, sediment dispersal was controlled by marine transgressive/regressive cycles related to eustatic sea-level changes with varying duration. Differential subsidence locally influenced sediment accumulation. Collectively, these controls resulted in eleven chronostratigraphically confined delta-wide mega-sequences with considerable internal lithological variation.The various sea-level cycles were in or out of phase with each other and with local subsidence, and interfered with each other and thus influenced the depositional processes. At the high inflection points of the long-term eustatic sea-level curve, floodings took place that resulted in delta-wide shale markers. At the low inflection points, erosional channels were formed that are often associated, downdip, with turbidites in low-stand sediments (LSTs). The megasequences contain regional transgressive claystone units (TST) followed by a range of heterogeneous fine-to-coarse progradational or aggradational siliciclastic (para)sequence sets formed during sea-level high-stand (HST).An updated biostratigraphic scheme for the Niger Delta is presented. It also updates a sedimentation model that takes into consideration local and delta-wide effects of sea-level cyclicity and delta tectonics. Megasequences were formed over time intervals of ~5 Ma within individual accurate megastructures that laterally linked into depobelts. The megasequences form the time-stratigraphic frame of the delta and are the backbone for the new delta-wide lithostratigraphy proposed here. Such a new lithostratigraphy is badly needed, in particular because of the vigorous new activity in the offshore part of the Niger Delta (not covered in this contribution). There, as well as in the onshore part of the delta, the traditional lithostratigraphic subdivision of the Cenozoic Niger Delta section into three formations is insufficient for optimum stratigraphic application; moreover, the various informal subdivisions that have been proposed over time are inconsistent.</abstract>

Stratigraphy and sedimentology of the Niger Delta

<abstract><title style='display:none'>Abstract</title>The 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.</abstract>

A new type of slumping-induced soft-sediment deformation structure: the envelope structure

<abstract><title style='display:none'>Abstract</title>Hydrocarbon exploration in The Netherlands has a chequered history from serendipitous oil shows via chance oil/ gas discoveries to finding the largest continental European oil field in 1943, followed by finding the largest gas field in the world in 1959. The present contribution traces the development of moderate to good porosity/permeability trends in depositional facies of Zechstein Stassfurt carbonates in a ‘gas play’ intermediate in significance between the above two plays but all in the northern part of The Netherlands. Various depositional facies in the Stassfurt carbonates were turned into ‘carbonate fabric units’ by diagenetic processes creating or occluding the porosity/permeability. This formed moderate to good gas reservoirs in barrier-shoal, open-marine shelf and proximal-slope carbonates in the subsurface of the province of Drenthe in the NE Netherlands. The diagenetic models forming these carbonate fabric units are linked to the variety of facies in a depositional model which shows explain and predicts the reservoir trends. Such depositional/diagenetic facies are ‘translated’ into characteristic petrophysical values recognisable on wire line logs in uncored wells, and in characteristic seismic expressions that show these trends in undrilled areas. This approach has been proven to be effective in delineating porosity trends, visualised by 3-D seismic in the Collendoornerveen field, and thus provides a new exploration ‘tool’ in hydrocarbon exploration .</abstract>

Sedimentology and diagenesis as ‘hydrocarbon exploration tools’ in the Late Permian Zechstein-2 Carbonate Member (NE Netherlands)

The encyclopedia of volcanoes (second edition)

<abstract><title style='display:none'>Abstract</title>Assessments of the infiltration recharge of groundwater are performed using various methods and on different scales. Infiltration is dependent of climatic factors, aspects of water circulation, as well as on quasi-stationary and variable environmental features of a specific area, which are frequently difficult to determine on the basis of direct measurements or observations. The objective of the present study was to identify factors conditioning recharge of shallow groundwater in selected catchment areas of the Poznań Upland using the WetSpass simulation water balance model with spatially distributed parameters. Our analysis has indicated favourable and unfavourable conditions for recharge of groundwater in the annual period and in both half-year periods, which are the result of mutual relationships between the physical qualities of these catchment areas and their climatic and hydrological characteristics. The results obtained also confirmed the impact of surface runoff and actual evapotranspiration on the spatial distribution of effective infiltration. With soil types and groundwater depth distributions being similar in the catchment areas, changes in relationships between components of water balance are caused by differences in the type of land usage. Application of the WetSpass model has made it possible to arrive at a more accurate assessment of groundwater recharge. The results obtained may be used for erification of recharge areas and values of effective infiltration, set as a boundary condition in groundwater flow models.</abstract>

Application of the WetSpass simulation model for determining conditions governing the recharge of shallow groundwater in the Poznań Upland, Poland

<abstract>
<title style='display:none'>Abstract</title>
Fossil pearls are rare but important palaeoecological indicators in proving the former presence of parasites. A single right valve of <italic>Hyotissa hyotis</italic> from the Pliocene of Sidi Brahim shows numerous blister pearls inside the adductor muscle imprint. At the same locality, numerous shells with smooth adductor scars and without any blisters, have been collected. The structures in the studied valve can be assigned to blister pearls with high confidence due to their similarity to other Cenozoic pearls from Austria. The blister pearls likely formed as a reaction to parasite infestation. It is possible that some parasites especially targeted areas associated with the adductor muscles in the oyster genus <italic>Hyotissa</italic>, because similar blister pearls have previously been described in a congeneric species, <italic>H. squarrosa</italic>, from the Miocene of Austria.
</abstract>

First record of blister pearls in the oyster <italic>Hyotissa hyotis</italic> (Linné, 1758) from Pliocene deposits at Sidi Brahim, Lower Chelif Basin (north-west Algeria)

Thanks to the journal’s reviewers

<abstract>
<title style='display:none'>Abstract</title>
Models (paradigms) and former interpretations have often been presupposed when conducting field research. In the 19th century diamictites were for the first time interpreted to have originated from ancient glaciations. These interpretations have to a large part prevailed in the geological community, although there has been much progress in the areas of sedimentology, glaciology and physical geography. The present work is an effort to find criteria which most clearly discriminate between geological features produced by different processes, mainly glaciation and mass flow, the latter predominantly sediment gravity flows. Geological features which have been interpreted to have formed by glaciation throughout pre-Pleistocene Earth history are compared to similar-appearing geological features formed by mass flow and tectonics, so as to uncover variations in the appearance between features resulting from these different processes. The starting point for this comparison is documentation of the appearance of Quaternary products of erosion and deposition, in order to discern the origin of older formations. It is shown that the appearance and origin of pavements, dropstones, valleys, small-scale landforms, surface microtextures and most other geological features may in some cases be equivocal, but in others the details are indicative of the process which generated the feature. Detailed geological field data which have been compiled by geologists from outcrops of pre-Pleistocene strata, more often than is considered in most papers, commonly point to a mass flow origin, mainly a sediment gravity flow origin, rather than a glaciogenic origin. A process of multiple working hypotheses or interpretations is therefore advocated, based mainly on a comparison of the appearance of features formed by different geological processes documented from different research disciplines. Instead of starting with current interpretations or models, this multiple working hypothesis or methodology helps to avoid confirmation bias and jumping to conclusions.
</abstract>

Patterns, processes and models – an analytical review of current ambiguous interpretations of the evidence for pre-Pleistocene glaciations

<bold>Pliny and the eruption of Vesuvius</bold>, by Pedar W. Foss, 2022. Routledge, 1st edition; 334 pages. Hardback: price £136.00, e-book: price £39.99; ISBN: 978-0415705462.

Book reviews

Authors of articles published in Geologos in 2023 – brief information

<abstract><title style='display:none'>Abstract</title>The current growth in geotourism requires an urgent development of classifications of geological features on the basis of criteria that are relevant to tourist perceptions. It appears that structure-related patterns are especially attractive for geotourists. Consideration of the main criteria by which tourists judge beauty and observations made in the geodiversity hotspot of the Western Caucasus allow us to propose a tentative aesthetics-based classification of geological structures in outcrops, with two classes and four subclasses. It is possible to distinguish between regular and quasi-regular patterns (i.e., striped and lined and contorted patterns) and irregular and complex patterns (paysage and sculptured patterns). Typical examples of each case are found both in the study area and on a global scale. The application of the proposed classification permits to emphasise features of interest to a broad range of tourists. Aesthetics-based (i.e., non-geological) classifications are necessary to take into account visions and attitudes of visitors.</abstract>

postal address: P.O. Box 7333, Rostov-na-Donu, 344056

Aesthetics-based classification of geological structures in outcrops for geotourism purposes: a tentative proposal

<abstract><title style='display:none'>Abstract</title>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 structures 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 association.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.</abstract>

Department of Geological Sciences, Jadavpur University, Kolkata-700 032, India

Department of Earth Sciences, IIT Bombay, Powai, Mumbai 400 076, India

Institute of Geology, Adam Mickiewicz University, Maków Polnych 16, 61-606 Poznan, Poland. e-mail:

Seismic and non-seismic soft-sediment deformation structures in the Proterozoic Bhander Limestone, central India

<abstract xml:lang="en"><title style='display:none'>Alternative interpretations of grain-size data from Quaternary deposits</title>Several possibilities to present and to interpret the results of granulometric analyses of Quaternary fluvial, aeolian, glacial and wash-out slope deposits were investigated. Attention is paid particularly to the cumulative curves at a probability scale and the frequency curves, and it is shown how these curves can help to determine the sedimentary environment. The inclination of the cumulative curves in the part of the maximum proportion of a particular grain size appears significant. It appears possible to obtain information on the density and dynamics of the transporting medium from the course of the cumulative curves (inclination and spread of grain size).The examination of textural parameters allows to draw regression lines characteristic of both deposits from various sedimentary environments and deposits from one single environment but with different histories as to their transport dynamics.</abstract>

The Family Alliance School of Higher Education, M. Grzegorzewskiej 10, 02-778, Warsaw, Poland

Institute of Geography, Jan Kochanowski University in Kielce, Świętokrzyska 15, 25-418, Kielce, Poland

Alternative interpretations of grain-size data from Quaternary deposits

<abstract><title style='display:none'>Abstract</title> We present results of research into fluvial to aeolian successions at four sites in the foreland of the Last Glacial Maximum, i.e., the central part of the “European Sand Belt”. These sites include dune fields on higher-lying river terraces and alluvial fans. Sediments were subjected to detailed lithofacies analyses and sampling for morphoscopic assessment of quartz grains. Based on these results, three units were identified in the sedimentary succession: fluvial, fluvio-aeolian and aeolian. Material with traces of aeolian origin predominate in these sediments and this enabled conclusions on the activity of aeolian processes during the Pleniglacial and Late Glacial, and the source of sediment supply to be drawn. Aeolian processes played a major role in the deposition of the lower portions of the fluvial and fluvio-aeolian units. Aeolian material in the fluvial unit stems from aeolian accumulation of fluvial sediments within the valley as well as particles transported by wind from beyond the valley. The fluvio-aeolian unit is composed mainly of fluvial sediments that were subject to multiple redeposition, and long-term, intensive processing in an aeolian environment. In spite of the asynchronous onset of deposition of the fluvio-aeolian unit, it is characterised by the greatest homogeneity of structural and textural characteristics. Although the aeolian unit was laid down simultaneously, it is typified by the widest range of variation in quartz morphoscopic traits. It reflects local factors, mainly the origin of the source material, rather than climate. The duration of dune-formation processes was too short to be reflected in the morphoscopy of quartz grains.</abstract>

Faculty of Geology, University of Warsaw, Al. Żwirki i Wigury 93, 02-089 Warsaw, Poland

Department of Geoecology and Palaeogeography, Maria Curie-Skłodowska University in Lublin, Kraśnicka 2cd, 20-718 Lublin, Poland

Department of Marine Geology, Institute of Oceanography, University of Gdańsk, Al. Piłsudskiego 46, 81-378 Gdynia, Poland;

Climate evolution during the Pleniglacial and Late Glacial as recorded in quartz grain morphoscopy of fluvial to aeolian successions of the European Sand Belt

<abstract><title style='display:none'>Abstract</title>The Baba Ali skarn deposit, situated 39 km to the northwest of Hamadan (Iran), is the result of a syenitic pluton that intruded and metamorphosed the diorite host rock. Rare earth element (REE) values in the quartz syenite and diorite range between 35.4 and 560 ppm. Although the distribution pattern of REEs is more and less flat and smooth, light REEs (LREEs) in general show higher concentrations than heavy REEs (HREEs) in different lithounits. The skarn zone reveals the highest REE-enriched pattern, while the ore zone shows the maximum depletion pattern. A comparison of the concentration variations of LREEs (La–Nd), middle REEs (MREEs; Sm–Ho) and HREEs (Er–Lu) of the ore zone samples to the other zones elucidates two important points for the distribution of REEs: 1) the distribution patterns of LREEs and MREEs show a distinct depletion in the ore zone while representing a great enrichment in the skarn facies neighbouring the ore body border and decreasing towards the altered diorite host rock; 2) HREEs show the same pattern, but in the exoskarn do not reveal any distinct increase as observed for LREEs and MREEs. The ratio of La/Y in the Baba Ali skarn ranges from 0.37 to 2.89. The ore zone has the highest La/Y ratio. In this regard the skarn zones exhibit two distinctive portions: 1) one that has La/Y &gt;1 beingadjacent to the ore body and; 2) another one with La/Y &lt; 1 neighbouring altered diorite. Accordingly, the Baba Ali profile, from the quartz syenite to the middle part of the exoskarn, demonstrates chiefly alkaline conditions of formation, with a gradual change to acidic towards the altered diorite host rocks. Utilising three parameters, Ce/Ce*, Eu/Eu* and (Pr/Yb)n, in different minerals implies that the hydrothermal fluids responsible for epidote and garnet were mostly of magmatic origin and for magnetite, actinolite and phlogopite these were of magmatic origin with low REE concentration or meteoric water involved.</abstract>

Geochemistry of rare earth elements in the Baba Ali magnetite skarn deposit, western Iran – a key to determine conditions of mineralisation

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Geologos

The Journal of Adam Mickiewicz University

GEOLOGOS is an international, peer-reviewed journal publishing research results and review articles covering all earth-science disciplines, with a focus on the geology of central and eastern...

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GEOLOGOS is an international, peer-reviewed journal publishing research results and review articles covering all earth-science disciplines, with a focus on...