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Sedimentology and palaeoenvironmental reconstruction of the late Pleistocene deposits along the Bizerte Coast, N-E Tunisia

Wided Sahli, Saadi Jalila, Adel Klai, Kamel Regaya

Geological Quarterly

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2023

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Vol. 67, No. 2

art. no. 16

EN

The N–E Tunisian coast (Bizerte region) shows several Quaternary sedimentary archives of middle to late Pleistocene age. Sedimentological analyses carried out (grain size, morphoscopy, exoscopy, petrography, mineralogy, and fossil content) on 12 sections reveal a succession that begins with infratidal deposits attributed to the last Interglacial period, followed by intertidal, continental (palaeosol) and/or aeolian deposits (aeolianites). The arrangement of these deposits, their lithological characteristics and their faunal contents are the basis for a palaeoenvironment reconstruction and estimation of palaeoclimatic conditions. A warmer climate and a high sea level characterize the beginning of this interval, followed by a sea level fall accompanied by an alternation of humid and arid climate. This alternation is reflected by intercalations of the palaeosol levels between the aeolian deposits.

2

Insights into the palaeoenvironments, structure and stratigraphy of the lower Miocene of the Eastern Carpathians Bend Zone, Romania

Bercea Răzvan-Ionuţ, Bălc Ramona, Tămaș Alexandra, Filipescu Sorin, Mircea Tămaș Dan, Guillong Marcel, Flavius Szekely Flavius, Lukács Réka

Geological Quarterly

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2023

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Vol. 67, No. 1

art. no. 2

EN

The ages of several Oligocene to Miocene sedimentary formations from the Eastern Carpathians Bend Zone are poorly constrained due to palaeoenvironmental factors, reworking of fossils, structural complexity and limited exposure. To help overcome these issues, this study integrates calcareous nannoplankton and foraminifera biostratigraphy with isotopic age dating (U-Pb) of volcaniclastic zircons, and sedimentological and structural observations/interpretations. Our study was carried out along an ~6-km-long section made from a series of outcrops along the Bizdidel River which exposes several formations such as the Pucioasa, Fusaru, Vinețișu, Starchiojd and Slon. We show that the Fusaru Formation consists of coarse-grained rocks deposited as confined longitudinal channel successions that migrated laterally. It is bounded by the mud-rich Pucioasa and Vinețișu formations which are lateral equivalents of the Fusaru confined channels deposited as levee/overbank units. These genetically related formations appear to reach younger ages – of the lower to middle Burdigalian based on calcareous nannoplankton and foraminifera biostratigraphy – than previously thought (upper Oligocene to lower Burdigalian). The dominant organic-rich mudstones of the Starchiojd Formation represent pelagites/hemipelagites deposited in anoxic conditions. Their middle Burdigalian age is established by a 17.41 ±0.27 Ma zircon U-Pb age of zircons from the Bătrâni Tuff in the Starchiojd Formation. Based on the similar phenocryst content, zircon U-Pb age and zircon trace element composition, the source of the tuff is suggested to be the 17.3 Ma Eger ignimbrite-forming eruption, which has proximal, near-caldera deposits in the Bükkalja Volcanic Field, Hungary. The mud-rich Slon Formation seems to be related to shelf edge/upslope failure that formed cohesive debrite avalanches resulting from foreland propagation of compression. The Slon Formation extends in this area to at least the upper part of the lower Miocene to middle Miocene. These results highlight the need to revise ages of those parts of the sequence which are poorly constrained or different in other parts of the Carpathian Basin. Such revised ages help to better constrain the understanding of the deformation history of the Carpathians.

3

Lost Norian fluvial tracks : Sedimentology and stratigraphy of the Upper Triassic coarse-grained deposits in Kamienica Śląska (Upper Silesia, southern Poland)

Fijałkowska-Mader Anna, Paszkowski Mariusz, Kędzior Artur, Jewuła Karol

Annales Societatis Geologorum Poloniae

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2022

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Vol. 92, No. 3

277--293

EN

In the Triassic-Jurassic boundary profiles of the Upper Silesian region, there are locally developed coarse clastic deposits, commonly known as the Połomia Gravels, Połomia Beds or “Połomia Formation’’ (informal name). Due to the lack of reliable stratigraphic tools, the chronostratigraphic position of these deposits remains one of the most controversial aspects of the Triassic-Jurassic lithostratigraphy in the region. Sparse biostratigraphic data from the overlying and underlying deposits indicate a wide range of ages, from the Late Triassic to Early Jurassic. This paper presents the results of sedimentological, petrographical and palynological analyses of the coarse-grained deposits from the Kamienica Śląska gravel pit, which is currently one of the biggest facilities of this type in Upper Silesia. The outcrop section, with a total thickness of up to 20 m, is dominated by friable, light grey to beige and locally dark grey, large-scale planar to trough cross-stratified conglomerates and coarse-grained sandstones with subordinate thin interbeds of grey and reddish brown mudstones. Three facies associations have been distinguished, representing a main channel belt, secondary channels and floodplains subenvironments. Facies analysis points to a braided river tract with localised floodplain sediments. The grain composition of the Kamienica Śląska gravel/conglomerate is less diversified than that of the polymictic typical Połomia Beds of the Myszków area and resembles oligomictic conglomerates known from the Grabowa Formation of the Norian age and/or conglomerates of the Gorzów Beds of Rhaetian age, which also occur on the studied region. Palynological analysis of mudstone interbeds within the conglomeratic deposits shows the presence of miospores guiding and characteristic for subzone c of the Corollina meyeriana zone of the late Norian-early Rhaetian age. The appearance of the coarse-grained deposits in late Norian could be associated with the development of a long-reach braided fluvial tract, draining the S and SE part of the Sudetian-Malopolska-Lublin land (S-M-L land) in response to the tectonic rearrangement in the source area and gradual climatic change from semi-arid to humid in the Rhaetian.

4

Tsunami event identified in a sedimentary record of the Gaza Strip, Palestine

Ubeid Khalid Fathi

Studia Quaternaria

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2021

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Vol. 38, Nr 1

43--51

EN

The outcrop of the tsunami deposits, about 6 m thick, is located in the archaeological site Tel Askan in the Al Zhraa locality, southwest of the Gaza City. These deposits are unconformably underlain by sand dunes and sharply overlain by a palaeosol. They are pale gray sands mixed with volcanic ash and fine-grained deposits, and are intercalated with peat, few centimetres thick. The sand-sized grains are well rounded and well sorted, and consist mainly of quartz and subordinate of feldspar. Both macro- and microfossils were observed from tsunami deposits. Additionally, rip-up clasts and pottery shards were observed, indicating higher-flow regime. The potteries in tsunami deposits provide evidence for tsunami inundation at distance of about 1 km from the present shoreline.

5

Middle and Late Pleistocene loess-palaeosol archives in East Croatia: multi-proxy palaeoecological studies on Zmajevac and Šarengrad II sequences

Molnár Dávid, Makó László, Cseh Péter, Sümegi Pál, Fekete István, Galović Lidija

Studia Quaternaria

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2021

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Vol. 38, Nr 1

3--17

EN

Multi-proxy palaeoenvironmental analyses on the two loess-palaeosol sequences of Šarengrad II and Zmajevac (Croatia) provided the opportunity to obtain various data on climatic and environmental events that occurred in the southern part of the Carpathian Basin during the past 350,000 years. Palaeoecological horizons were reconstructed using sedimentological data (organic matter and carbonate content, grain-size distribution and magnetic susceptibility) and the dominance-based malacological results (MZs) supported by habitat and richness charts, moreover multi-variate statistics (cluster analysis). The correlation of the reconstructed palaeoecological horizons with global climatic trends (Marine Isotope Stages) determined the main accumulation processes in the examined areas. The palaeoecological analyses revealed specific accumulation conditions at both sequences, fluvial and aeolian environments at Šarengrad and a possible forest refuge at Zmajevac.

6

MAR comparisons between different chronometric methods for two profilesin the Bodrogkeresztúr area

Makó László, Molnár Dávid, Cseh Péter, Sümegi Pál

Studia Quaternaria

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2021

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Vol. 38, Nr 1

67--73

EN

The deepening and exploration of the loess-palaeosol section at the foot of the Kopasz Hill at Bodrogkeresztúr have been carried out to expand the existing knowledge of the Carpathian foothill palaeoenvironmental factors and their impact. The study deals with particle size analysis, organic matter and carbonate content. For the presentation of age-depth models, the OSL dates of Bodrogkeresztúr (BKT) and the 14C dates of Bodrogkeresztúr, brickyard 1 were used-, and the diagrams of the Accumulation Rates (AR) derived from them. These were compared with Mass Accumulation Rate (MAR) calculations based on OSL and 14C data from BKT and 14C data from Bodrogkeresztúr, brickyard 1. It became evident that there is a significant difference between the two sections, which may be due to the upland position, the overlap, or the wind tunnel effect. Sedimentological studies revealed coarser grain composition, however, the nearly complete absence of coarser sand fraction is also noticeable in the case of BKT. Also, the entire section is characterized by increased carbonate content due to post-sedimentation processes, recarbonization and leaching. The AR and MAR results show the difference between the suitability of different chronometric methods, indicating that the top of both sections may have been redeposited or eroded.

7

Lacustrine deltas and subaqueous fans: almost the same, but different – a review

Gruszka Beata, Zieliński Tomasz

Geologos

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2021

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Vol. 27, No. 1

43--55

EN

Although deltas and subaqueous fans are both formed in the same near-shore zones of basins, the hydraulic conditions for their formation, development and sedimentary records are different. The present review discusses the results of previously published studies of fan deltas (Gilbert-type deltas) and subaqueous fans of lacustrine and glaciolacustrine environments. The depositional mechanisms of deltas and subaqueous fans, textural and structural features of the lithofacies associations and their typical lithofacies are presented. The characteristics of subaqueous fans, which are still relatively poorly understood and are often overlooked in sedimentological interpretations of lacustrine sedimentary successions, receive particular attention. The palaeoenvironmental and lithological differences between deltas and subaqueous fans are highlighted.

8

Tectonic-climatic interactions during changes of depositional environments in the Carpathian foreland: An example from the Neogene of central Poland

Widera Marek, Zieliński Tomasz, Chomiak Lilianna, Maciaszek Piotr, Wachocki Robert, Bechtel Achim, Słodkowska Barbara, Worobiec Elżbieta, Worobiec Grzegorz

Acta Geologica Polonica

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2021

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Vol. 71, no. 4

519--542

EN

Many geological problems have not been convincingly explained so far and are debatable, for instance the origin and changes of the Neogene depositional environments in central Poland. Therefore, these changes have been reconstructed in terms of global to local tectonic and climatic fluctuations. The examined Neogene deposits are divided into a sub-lignite unit (Koźmin Formation), a lignite-bearing unit (Grey Clays Member), and a supra-lignite unit (Wielkopolska Member). The two lithostratigraphic members constitute the Poznań Formation. The results of facies analysis show that the Koźmin Formation was deposited by relatively high-gradient and well-drained braided rivers. Most likely, they encompassed widespread alluvial plains. In the case of the Grey Clays Member, the type of river in close proximity to which the mid-Miocene low-lying mires existed and then were transformed into the first Mid-Miocene Lignite Seam (MPLS-1), has not been resolved. The obtained results confirm the formation of the Wielkopolska Member by low-gradient, but mostly well-drained anastomosing or anastomosing-to-meandering rivers. The depositional evolution of the examined successions depended on tectonic and climatic changes that may be closely related to the mid-Miocene great tectonic remodelling of the Alpine-Carpathian orogen. This resulted in palaeogeographic changes in its foreland in the form of limiting the flow of wet air and water masses from the south and vertical tectonic movements.

9

Badania złóż soli kamiennej i potasowo-magnezowej prowadzone w Państwowym Instytucie Geologicznym

Czapowski Grzegorz, Peryt Tadeusz, Marek

Przegląd Geologiczny

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2019

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Vol. 67, nr 7

594--598

EN

Middle Miocene Badenian salt, occurring in the frontal zone of the Carpathian Overthrust (southern Poland), and the Upper Permian (Zechstein) bedded and diapir salt deposits, have been the subject of the research by PGI scientists. Many salt deposits were discovered by the PGI, but in particular, the greatest achievement related to the origin of salt deposits is the reconstruction of sedimentary environments and conditions based on detailed sedimentological and geochemical analyses.

10

The interpretative significance of ripple-derived sedimentary structures within an upper Neogene fluvial succession of central Poland

Maciaszek Piotr, Chomiak Lilianna, Wachocki Robert, Widera Marek

Geologos

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2019

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Vol. 25, No. 1

1--13

EN

Sedimentary structures discussed in the present study are genetically linked to ripples that consist of pure sand or alternating sand and mud layers. All types of ripple-related structures, such as climbing-ripple cross-lamination and heterolithic bedding, i.e., flaser, wavy and lenticular (nodular), have been identified for the first time in fluvial strata that have been characterised previously as commonly massive. These small-scale bedforms, produced by migrating ripples, have been documented in a fluvial channel of late Neogene age in central Poland. The abundance and co-occurrence of the structures discussed and their spatial distribution provide evidence of their formation under very low-energy conditions, when flow velocity changed markedly, but was often significantly less than 0.5 m/s. Therefore, these ripple-derived sedimentary structures are here recognised as typical of channel fills of an anastomosing river.

11

Secular and catastrophic processes reflected in sediments of the Suchedniów water reservoir, Holy Cross Mountains (Poland)

Przepióra Paweł, Kalicki Tomasz, Aksamit Michał, Biesaga Piotr, Frączek Marcin, Grzeszczyk Paulina, Malęga Emanuela, Chrabąszcz Mariusz, Kłusakiewicz Edyta, Kusztal Piotr

Geologos

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2019

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Vol. 25, No. 2

139--152

EN

The Suchedniów water reservoir is located in the central section of the River Kamionka in the northern part of the Holy Cross Mountains of central Poland. This area once belonged to the Old Polish Industrial District that, during the Middle Ages, was very intensively developed by iron metallurgy. Many forges and mills along the rivers used water power, which led to the construction of an anthropogenic, small-scale water retention system. At the beginning of the twentieth century many of these reservoirs were drained after the collapse of metallurgical activities. The present-day reservoir was built in 1974 and drained in 2017. Research into the drained basin has documented various forms and sediments, some of which record present-day depositional processes (fire proof clay layer, inland fan delta), while others represent the historical period (lacustrine sediments of older reservoirs). Traces of catastrophic events have been preserved as well; an assemblage of megaripples marks the sudden drainage caused by a dam break in 1974.

12

Tectonic discrimination of siliciclastic sedimentary record of the northern Tethyan margin at the end of the Triassic

Vďačný Marek, Michalík Josef, Lintnerová Otília

Geological Quarterly

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2019

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Vol. 63, No. 1

30--38

EN

Tectonic setting of both the uppermost Triassic Tomanová and the lowermost Jurassic Dudziniec formations can be characterized by a series of diagnostic discrimination diagrams. High-silica and low-silica multi-dimensional diagrams indicate that the sediments could have been deposited in the continental collision/rift setting. Diagrams of K2O/Na2O versus SiO2, SiO2/Al2O3 versus K2O/Na2O and Th-Co-Zr/10 as well as Th-Sc-Zr/10 determine an origin from the tectonically active and/or passive continental margin setting. REE parameters indicate predominantly a passive margin tectonic setting of the sediments. The most probable source of clastic admixture in the Scythian to Domerian sediments in the Tatric Unit was situated in a remnant of the Variscan collisional orogen - the Vindelician Highlands. Occasional monsoonal rains occurring in orbitally controlled cycles transported weathered material from the source area down river valleys on the seaward slopes of the Variscan Vindelician Mountains towards the Tethyan Sea. The input of this material influenced also the marginal parts of the Fatricum (e.g., Vysoká or Havran units).

13

Main determinants of the grain size distribution of overbank deposits in Poland : an overview of literature on models of sedimentation

Szmańda J. B.

Geological Quarterly

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2018

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Vol. 62, No. 4

873--880

EN

The article describes the most important features of the grain size distribution of overbank deposits (madas) of Polish rivers. The most important characteristics of their deposition and the factors determining the variability of the grain size distribution of overbank deposits are indicated. Almost all grain fractions distinguished in nature, i.e. cobbles, gravels, sands, silts, and clays, occur in the overbank deposits of Polish rivers. The sandy fraction dominates in overbank sediments, which contradicts their widespread recognition as silty-clayey (mud) sediments. The change in the proportion of these fractions (the formation of different types of lithological overbank deposits) is caused by a change in the conditions of sediment transport dependent on six factors: (1) decrease in water flow velocity over a floodplain along with an increase in the distance from the river channel, (2) change in water flow velocity during a single flood (stages of a flood), (3) the diversity of the floodplain relief, (4) changes in the forest cover of the river basin (catchment), (5) change in the longitudinal slope and (6) width of floodplains.

14

An Early Jurassic braided river system from Mehadia, South Carpathians, Romania

Kędzior A., Popa M. E.

Geological Quarterly

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2018

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Vol. 62, No. 2

415--432

EN

The Lower Jurassic (Hettangian–Sinemurian) continental deposits of the Mehadia area (Caraş–Severin County) belong to the Presacina Basin, Upper Danubian Units of the South Carpathians, Romania. This un-named succession is exposed along large areas within the Greaţca Quarry where deposits of a complex braided river system can be seen. Nine clastic facies are identified within the Mehadia section and grouped into two facies associations reflecting two main sub-environments. (A) a fine-grained association, up to 6.5 m thick, composed of greyish black and dark grey massive and horizontally laminated mudstones interbedded with fine- to medium-grained sandstones showing ripple lamination, tabular low-angle large-scale cross-bedding and in some places massive sandstones. Within this association coarsening and fining-upward sequences are visible, while subordinate pensymmetrical-like sequences were observed. The sediments of the fine-grained association are interpreted as having been deposited along an alluvial plain from flood waters. The sandstone interbeds are interpreted as crevasse channel-fills and the thinner sandstone bodies as proximal crevasse splays. (B) a coarse-grained facies association represented by sandstones and conglomerates, both clast- and matrix-supported, from granule to pebble clast sizes. Almost all basal members of this association are underlain by erosional surfaces, while internal erosional surfaces occur at some levels. The coarse-grained facies association is interpreted as having been deposited within active river channels of a sandy braided river system. The occurrence of numerous erosional surfaces, the recurrence of the facies within this association (channel bodies), as well as the abundant mudstone and sandstone intraclasts all point to frequent conditions of erosion (including redeposition) of previously deposited sediments. The relatively low fine-grained sediment content (<25%) can be explained by two factors: (1) a creation rate for accommodation space was not enough for the accumulation of a large amount of overbank deposits; (2) a lack of larger quantities of fine-grained material being transported in the river system. Both factors may have operated independently or interacted.

15

The Late Quaternary vegetational and environmental history of western tropical Africa - the eastern Benin Basin, Lagos, Nigeria

Adeonipekun P. A., Adeniyi T. A., Mateawo J., Agbalaya B.

Geology, Geophysics and Environment

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2017

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Vol. 43, no. 4

277--291

EN

A palynological study of a 30 m borehole within the Akoka campus of the University of Lagos, Akoka, Nigeria revealed Late Quaternary paleo-vegetational, climatic and environmental changes. Sixteen samples at a regular interval of 2 m were subjected to standard palynological and sedimentological techniques. Six pollen zones representing six paleoclimatic phases within the Late Quaternary period were recognized. The age model is based on two radiocarbon dates (6 m: 5,495 ± 25 ¹⁴C yr and 12 m: 15,660 ± 40 ¹⁴C yr) and, by extrapolation, the sequence spans approximately the last 35,000 yr BP. The African maximum transgression and the African Humid Period (wet paleoclimate maximum) – the Nouaktchottian, and Pre-Nouaktchottian respectively – were recognized, while the Ogolian II (Erg II) was stratigraphically recognized and the Upper Inchirian extrapolated. Recovered diatom frustules with other proxies were employed for paleoclimatic and paleoecological deductions. Four hydrological cycles and three paleoecological settings were identified. Results from this work indicate the co-eval record of paleoclimatic events across Africa, suspected cooling during the African maximum transgression in Nigeria and the usefulness of coastal freshwater swamp sediments for paleoclimate studies.

16

Evolution of Early Pleistocene fluvial systems in central Poland prior to the first ice sheet advance – a case study from the Bełchatów lignite mine

Goździk J., Zieliński T.

Geologos

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2017

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Vol. 23, No. 2

89--107

EN

Deposits formed between the Neogene/Pleistocene transition and into the Early Pleistocene have been studied, mainly on the basis of drillings and at rare, small outcrops in the lowland part of Polish territory. At the Bełchatów lignite mine (Kleszczów Graben, central Poland), one of the largest opencast pits in Europe, strata of this age have long been exposed in extensive outcrops. The present paper is based on our field studies and laboratory analyses, as well as on research data presented by other authors. For that reason, it can be seen as an overview of current knowledge of lowermost Pleistocene deposits at Bełchatów, where exploitation of the Quaternary overburden has just been completed. The results of cartographic work, sedimentological, mineralogical and palynological analyses as well as assessment of sand grain morphology have been considered. All of these studies have allowed the distinction of three Lower Pleistocene series, i.e., the Łękińsko, Faustynów and Krzaki series. These were laid down in fluvial environments between the end of the Pliocene up to the advance of the first Scandinavian ice sheet on central Poland. The following environmental features have been interpreted: phases of river incision and aggradation, changes of river channel patterns, source sediments for alluvia, rates of aeolian supply to rivers and roles of fluvial systems in morphological and geological development of the area. The two older series studied, i.e., Łękińsko and Faustynów, share common characteristics. They were formed by sinuous rivers in boreal forest and open forest environments. The Neogene substratum was the source of the alluvium. The younger series (Krzaki) formed mainly in a braided river setting, under conditions of progressive climatic cooling. Over time, a gradual increase of aeolian supply to the fluvial system can be noted; initially, silt and sand were laid down, followed by sand only during cold desert conditions. These fluvio-periglacial conditions are identified in the foreground of the advance of the oldest ice sheet into this part of central Poland. The series studied have been compared with other fluvial successions which accumulated in the Kleszczów Graben during subsequent glaciations so as to document general changes in fluvial systems as reactions to climatic evolution. Thus, a palaeoenvironmental scenario has emerged which could be considered to be characteristic of central Poland during the Early Pleistocene.

17

Palaeoecology and sedimentology of the Miocene marine and terrestrial deposits in the “Medieval Quarry” on Devínska Kobyla Hill (Vienna Basin)

Pivko D., Hudáčková N., Hrabovský J., Sládek I., Ruman A.

Geological Quarterly

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2017

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Vol. 61, No. 3

549--568

EN

Dramatic tectonic and sea level changes of the Central Paratethys realm during the Middle Miocene resulted in changes of the coastal and seabed morphology affecting the composition of the marine association and the distribution of the facies along the coast. Three different episodes (marine-terrestrial-marine) in the environmental evolution are interpreted. A lower marine unit (Badenian; Lower Serravallian) reflects organodetrital sedimentation on and around an algal bioherm. Low terrigenous input maërl facies of typical rhodalgal carbonate factory type characterise the top of the algal mound. On the slopes, a rim of rhodechfor facies separated the bioherm from the rest of the bottom which had a seagrass cover. This high-energy rhodechfor carbonate factory is described from the Central Paratethys realm for the first time. It is composed mostly of coralline algae (Mesophyllum, Lithothamnion, Spongites and Lithophyllum), benthic foraminifers (Elphidium crispum, Neoconorbina terquemi, Miniacina sp., Borelis melo), echinoids (cidaroid, spatangoid and diadematoid groups) and bryozoans. Uplift of the Malé Karpaty Mts. resulted in tectonic activity in the vicinity, documented by the presence of clastic dikes and normal faults in the profile studied. Subsequent fluvial and terrestrial sedimentation is represented by regolith, palaeosoil and channel body deposits set discordantly on the top of lagoonal deposits. Finally, the third episode is represented by the Sarmatian transgressive marine sequence, which is characterized by coarse pebbly deposit eroded from an uplifted pre-Neogene basement. The strata studied originated in a warm temperate climate around the Badenian–Sarmatian transition.

18

A Miocene anastomosing river system in the area of Konin Lignite Mine, central Poland

Widera M., Kowalska E., Fortuna M.

Annales Societatis Geologorum Poloniae

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2017

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Vol. 87, No. 2

157--168

EN

This sedimentological study of the Wielkopolska Member of the Miocene Poznań Formation in the Jóźwin IIB opencast lignite-mining field, central Poland, reveals a late mid-Miocene anastomosing fluvial system with ribbon-shaped channels filled mainly by sandy and muddy deposits. The fluvial system, extending across the eastern flank of the post-Mesozoic Kleczew Graben, was tributive in its eastern upper reaches, but was increasingly distributive and northwards deflected in its lower reaches near the graben axis. Lithofacies analysis of a representative palaeochannel indicates that the river discharge significantly fluctuated and that the channels were filled with mud-bearing stratified fine-grained sand by low-density tractional turbulent flow during the high and low water stages and with a massive mud or sandy mud by a high-density flow during the rising and falling stages. The spatial pattern of fluvial channels and deformation channel-fill sandbodies were controlled by the graben topography and the differential compaction of peat substrate, with possible influence of bedrock faults. The fluvial system is thought to have drained to an endorheic ‘terminal’ basin to the north, rather than into the hypothetical Baltic River and further westwards to the distant North Sea basin, as postulated by some previous authors. The present case study contributes to the known spectrum of anastomosing river systems as a sand- to mud-dominated end-member.

19

Silurian stratigraphy of Central Iran - an update

Hairapetian V., Ghobadi Pour M., Popov L. E., Männik P., Miller C. G.

Acta Geologica Polonica

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2017

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Vol. 67, no. 2

201--233

EN

The Silurian biostratigraphy, lithostratigraphy, and facies of Central Iran including the Kashmar (Boghu Mountains), Tabas (Derenjal Mountains, Ozbak-Kuh), Anarak (Pol-e Khavand) and Kerman regions is reviewed and updated. The current state of knowledge of the Silurian in the Zagros Basin, Alborz, Kopet-Dagh and Talysh regions, as well as in a few areas scattered across the Sabzevar Zone, and the Sanandaj-Sirjan terranes is also reviewed. Silurian volcanism in various parts of Iran is briefly discussed. The end of the Ordovician coincided with a widespread regression across Iran synchronous with the Hirnantian glaciation, and only in the Zagros Basin is there a continuous Ordovician–Silurian transition represented by graptolitic black shales of the Sarchahan Formation. In the Central-East Iranian Platform marine sedimentation re-commenced in the early to mid Aeronian. By the Sheinwoodian, carbonate platform depositional environments were established along its north-eastern margin. In other parts of Iran (e.g., Kopet-Dagh and the Sabzevar Zone), siliciclastic sedimentation continued probably into the late Silurian. The Silurian conodont and brachiopod biostratigraphy of Central Iran is significantly updated facilitating a precise correlation with the Standard Global Chronostratigraphic Scale, as well as with key Silurian sections in other parts of Iran. The Silurian lithostratigraphy is considerably revised and two new lithostratigraphical units, namely the Boghu and Dahaneh-Kalut formations, are introduced.

20

Evaluation of geochemical anomalies detected in the Boda Claystone Formation

Nadasi J., Madai V., Foldessy J.

Geology, Geophysics and Environment

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2016

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Vol. 42, no. 1

105--106

EN

The Boda Claystone Formation (BCF) is a sedimentary complex researched for decades (Barabásné Stuhl 1981, Fülöp 1994, Varga 2009, Halász 2011). It was chosen the most suitable geological formation to host the high-level radioactive waste disposal (HRWD) facility in Hungary (Hámos et al. 1999, Konrád & Hámos 2006). Since the first mappings it has been known – that the reductive layers of the formation ore-indications appear (Kiss 1960). Since these were not studied, their significance is unknown. The establishment of the radioactive waste disposal facility and a possible-ore extraction are incompatible. Our study aimed at clarifying the nature of these anomalies; assess their potential as possible economic mineralisation during the geological research for the HRWD-project. The deep boreholes which penetrated the BCF formation encountered sulphide mineralization in certain intervals. Our evaluation is based on previous publications and reports, as well as the samples of the BAF-2 hole. The characterizations of the samples were made by macroscopically and on polished sections, in addition electron microprobe, XRD and XRF spectrometry measurements were used. A series of samples were assayed for trace element content by ICP-MS methods in the ALS Global Laboratory. The XRF chemical analysis was used to outline the main element distribution. Applying polished section microscopy and the microprobe studies, and complemented by ICP-MS assay, we could clarify that: - a section of the upper 100 m thick part of the BCF shows hydrothermal alteration effects, with Cu, Ag, Ba enrichment; - the origin of sulfide enrichment is – epigenetic and follows the albitization period, which has been interpreted as late diagenetic process; - in some REE minerals (monazite, xenotime) located in the microprobe samples structures suggesting remobilisation of REE occur. Based on these observations, we assume that on the higher level anomaly in the BAF-2 drill hole the reductive geochemical zone worked as trap during at subsequent hydrothermal fluid transport. The lower anomaly of sulphide enrichment does not show relation to any significant base metal or precious metal enrichment. It could not be verified, neither be excluded if the hydrothermal geochemical anomalies would indicate any ore mineralization of commercial grade. Further detailed sampling is warranted in the upper reductive zone to get better knowledge of the mineral assemblage and its potential economic importance.