Palaeoenvironmental Interpretation Research Articles

Taphonomy and palaeoenvironmental interpretation of a new amber-bearing outcrop from the mid-Cretaceous of the Maestrazgo Basin (E Iberian Peninsula)

Cretaceous amber-bearing outcrops are numerous and mainly distributed along the Northern Hemisphere. They have been related to extensive resin mass production occurring from the Barremian to the Campanian presumably due to interrelated abiotic and biotic factors. Amber outcrops are also abundant in the Iberian Peninsula, and they are mostly dated as Albian. Here, we present a new amber-bearing outcrop from the Cretaceous of the Maestrazgo Basin called La Dehesa (Estercuel, Aragón, Spain). This locality is assigned to the Boundary Marls Unit and is known for its rich and diverse palaeobotanical record. The dating of the amber-bearing bed is late Albian–early Cenomanian, based on palynomorphs and ostracods. Amber characteristics are compatible with a medium to long-distance transport before resin deposition, i.e., allochthonous origin. Organism-resin interactions have been identified, such as hyphae of resinicolous fungus in the cortex of the amber, a pholadid boring determined as Teredolites clavatus, and an oyster shell that grew on the solidified resin surface. No bioinclusions have been found so far. The study of the microfossils, some of them containing pyrite aggregates or crystals, found in the amber-bearing bed (palynomorphs, plant remains, foraminifers, echinoid spines, ostracods, and vertebrate remains) points to a coastal to inner mixed platform environment.

Landscape evolution and hydrology at the Late Pleistocene archaeological site of Narabeb in the Namib Sand Sea, Namibia

The Namib Sand Sea (NSS) in Namibia is known to preserve a wide variety of Pleistocene-age archaeological sites. However, few Middle Stone Age (MSA) sites in this region have been systematically investigated and basic questions around chronology and technological organization remain open. Here we examine Narabeb, an open air MSA surface site exposed in an interdune pan, ∼30 km into the northern NSS. Narabeb was first documented in the 1970s, and then re-examined in 2021 and 2022 by members of this team. Lithic technological analysis combined with a geomorphological description of the site, palaeoenvironmental interpretation of fine-grain water-lain sediments, and luminescence ages from northern and southern locations on the Narabeb pan provide some of the first understanding of human-environmental interactions and estimates of chronology from the later-Middle and Late Pleistocene in the NSS. In addition, we apply a quantitative approach to aeolian linear dune accumulation and extension to explore possible scenarios for landscape development at this site, in order to better understand the former water course(s) affecting the area. The new chronology suggests this site contained standing water at, or just after, the MIS 7/6 transition, and again at, or just after, the end of MIS 6 into early MIS 5. The timing of greater phases of water availability have some overlap with the speleothem growth record at Rössing Cave, situated ∼90 km north of the NSS (and ∼135 km north of Narabeb). Our results provide the foundation for larger, regional-scale analyses of early human adaptive strategies in this unique environment within Southern Africa.

Taphonomy of the middle Miocene regular echinoid spines from Cairo-Suez District, Egypt: Palaeoecological and palaeoenvironmental interpretations

The palaeoecology and palaeoenvironment of a dense cluster of regular echinoid spines that occur in an oyster-rich limestone layer are interpreted based on detailed taphonomic study. The paucispecific macrobenthic assemblage associated with these echinoid spines have been studied in the middle Miocene Geniefa Formation, Gebel Gharra, Cairo-Suez District of Egypt. Both echinoid spines and macrobenthic assemblages are dominated by moderately to well-preserved, moderately packed, highly disarticulated, moderately to poorly sorted, re-oriented, and moderately to highly fragmented specimens, confirming parautochthonous nature of this assemblage. The spines are commonly encrusted and bored. At least four taxonomic groups of encrusters are identified, including juvenile oysters, sheet-like cheilostome bryozoans, serpulids, and balanoid barnacles. The diversity of bioerosional ichnotaxa is moderate and includes Gastrochaenolites, Entobia, Maeandropolydora, Trypanites, and Spirolites. Moreover, some echinoid spines display distinct biting traces of fish, representing the first recorded of fish tooth bite marks on remains of regular echinoid spines from the Miocene deposits of Egypt. The faunal composition and trophic structure of the studied faunal assemblage indicate fully oxygenated and euhaline shallow-marine environment with meso- to eutrophic productivity level. The controlling environmental parameters include substrate consistency, bathymetry, water energy, surface-water productivity, and rate of sedimentation. Furthermore, two scenarios for sclerobionts colonisation and development of fish bite marks have been proposed. In the first syn vivo scenario, predatory fish either focused on the encrusting organisms attached to the spines or attacked the echinoid as a food source, resulting in the separation of spines from their original test during the echinoid’s life. In the second post-mortem scenario, disarticulated spines serve as a hard substrate for the colonisation of sclerobionts. Once again, the spines became subject to attacks by fish that fed on the encrusters, resulting in additional bite marks.

The Jurassic-Cretaceous boundary on the northern Tethyan margin: Karpentná and Ropice sections (Outer Western Carpathians, Czech Republic)

Microfacies and high-resolution studies at the Silesian Unit (Outer Western Carpathians, Czech Republic) on calpionellids, calcareous and non-calcareous dinoflagellate cysts, foraminifers and calcareous nannofossils, aligned with paleomagnetism, δ13Ccarb and δ18Ocarb, allow construction of a detailed stratigraphy and palaeoenvironmental interpretations across the Jurassic-Cretaceous (J/K) boundary. Two studied sections consist of allodapic and biomicritic limestones and marlstones. Ropice section spans the stratigraphic range from the upper Tithonian calpionellid Chitinoidella Zone, nannoplankton zone NJT16 to the lower Berriasian calpionellid Alpina Subzone of the Calpionella Zone, nannoplankton NC1 Zone. The J/K boundary is marked by the dominance of small forms of Calpionella alpina, rare occurrence of Nannoconus wintereri, and the first occurrence of organic-walled dinoflagellate cysts Dichadogonyaulax bensonii and Muderongia longicorna. A negative shift in the δ13Ccarb values corresponds to the Tithonian/Berriasian boundary, the base of the Calpionella Zone (Alpina Subzone). Karpentná section is represented by upper Tithonian calpionellid Chitinoidella to Crassicollaria zones. Remagnetization was documented in both sections.

Fluvial ichnofossil assemblage from the Miocene Siwalik succession of Pathankot District, Punjab, India: Palaeoenvironmental interpretation

Fluvial ichnofossil assemblage from the Miocene Siwalik succession of Pathankot District, Punjab, India: Palaeoenvironmental interpretation

Exceptional preservation of three-dimensional dunes on an ancient deep-marine seafloor: implications for sedimentary processes and depositional environments

Depositional and erosional bedforms can be used to reconstruct sedimentary processes and aid palaeoenvironmental interpretations. Using exhumed deep-marine strata in the Eocene Aínsa Basin, Spain, we document a 3-dimensional package of dunes, a rarely identified bedform in deep-marine environments. Our analysis shows that the dunes have curvilinear crests in planform, with smaller superimposed oblique dunes and ripples across the stoss sides. Beds containing these dunes have two main internal divisions: a lower inversely-graded (fine-to-coarse sandstone) and predominantly structureless division, and an upper coarse-grained sandstone division with well-developed cross-stratification, which is scoured and mantled with mudclasts and coarse-grains on the stoss-side. The rugose remnant relief of the bedforms controls the location of subsequent bedforms. Following recently reported direct measurements of natural turbidity currents, we interpret the basal division as recording deposition from the dense basal head of a high-velocity turbidity current, followed by the development of dunes beneath the more sustained but relatively high-velocity and unsteady flow body that reworked the initial sandy deposit into downstream migrating dunes and scours. These dune-forming beds have been identified in different deep-water environments in the Aínsa Basin stratigraphy, including channel overbank and channel mouth settings and scour-fills. These locations suggest that the dunes were intimately tied to high-velocity flows that bypassed through channel axes before expanded and depositing in less confined channel overbank or channel mouth settings. Preservation of these dunes in the Aínsa Basin was likely enhanced by tectonically-forced lateral migration of channels, which prevented cannibalisation of bypass-zones, in combination with high aggradation rates due to confinement, or periodic supply of flows from a particularly clay-poor source area. Where identified these dune-like bedforms are considered diagnostic of substantial sediment bypass downslope to deep-water basins.

Integrated biostratigraphy of Upper Cretaceous deposits from an exceptional continental vertebrate-bearing marine section (Transylvanian Basin, Romania) provides new constraints on the advent of ‘dwarf dinosaur’ faunas in Eastern Europe

The present paper outlines the results of a detailed study of calcareous nannofossils and small foraminifera made on Campanian marine deposits from the southwestern part of the Transylvanian Basin, Romania, part of the marine-to-continental transitional Petrești succession that yielded the oldest temporally well-constrained continental vertebrate remains in this area. These results are integrated with new and previously published palynostratigraphic information as well as with novel detrital zircon geochronometry data. All three groups of fossils (calcareous nannofossils, small foraminifera, and palynomorphs) convergently indicate an early to middle Late Campanian age for the marine part of the Petrești section. Based on detrital zircon analyses, the most likely maximum depositional age of the studied deposits is 76 ± 1.7 Ma, thus confirming the age supported by microfossil assemblages. Palaeoenvironmental interpretation of the fossil assemblages recovered from the marine part of the Petrești section suggests that despite their flysch-like facies, these beds were deposited in a continental shelf setting, under suboxic conditions and frequent fluctuations in nutrient supply to the seafloor, but quite stable environmental conditions within the water column. The synthesis of all currently available biostratigraphic and geochronologic data from the Petrești succession suggests a middle-late Late Campanian start for the expansion of the emergent land areas that made up the latest Cretaceous Hațeg Island, earlier than previously accepted dates (Maastrichtian) for this event. Furthermore, it documents the establishment of a diversified continental vertebrate faunal assemblage by the second half of the Late Campanian on these emergent lands while also providing further evidence for a later, post-Campanian arrival of certain iconic Hațeg Island dinosaur groups such as titanosaurs and hadrosauroids. Finally, our data show that kogaionid multituberculate mammals were already members of the earliest known Hațeg Island faunas, extending the fossil record of this group from the Maastrichtian into the later part of the middle Late Campanian.

Evolutionary model and palaeoenvironmental interpretation of the La Codera archaeological complex (Ebro Basin, NE Spain)

La Codera archaeological site is one of the most important settlements from the 1st Iron Age in the Ebro valley, dated between ca. 800 795 and ca. 460 cal. BC. The archaeological area also includes other later settlements. We analyzed the geomorphological context of the area by conducting a geoarchaeological survey and sampling. We also completed the evolutionary framework of the settlement, including paleoenvironmental information. Four slope stages (S1–S4) were identified, some of them related to fluvial terraces. Stages S4 and S3 are two old residual slopes dated to the Pleistocene, without evidence of human occupation. Older features related to human occupations are charcoals dated to Chalcolithic times from T2 terraces of La Codera stream. Slope S2 contains archaeological remains from the 1st Iron and Bronze Ages. Therefore, La Codera and its slopes were occupied during the Bronze Age, before Iron Age settlements. Slope S2 formation corresponds to the stable environmental stage known as the Iron Age Cold Epoch, or 2.8 Bond Event, also identified in many areas of the Ebro Depression. This period was followed by an erosive stage after the Roman Epoch (possibly during the 1.4 Bond Event). Later, a new slope (S1) formed, together with a new terrace (T1). This slope includes walls and ceramics from Iberian, Roman, and Medieval times toward the northeast of the settlement. These features make it possible to infer that this last accumulation formed during the cold stages of the LIA.

A review of the glacial environment arthropod trace fossilsUmfoloziaandWarvichniumwith the description of new ichnotaxa

AbstractTrace fossils are important records of the presence and behaviour of animals in the past, especially in deposits where few body fossils are preserved. They tend to provide the main palaeobiological record for past glacial environments, and are thus very important for understanding the ecology of these palaeoenvironments. Two ichnogenera are common in glacial sediments:UmfoloziaandWarvichnium. BothUmfoloziaandWarvichniumare attributed to arthropods; the former occurs across the Late Palaeozoic Ice Age (LPIA) and the latter occurs during both the LPIA and the Quaternary glacial event. Here, we review the stratigraphic record, ichnotaxonomy, palaeoecology, palaeoenvironments and possible tracemakers of these two ichnogenera. In addition to assessing morphological ichnotaxobases, we use multivariate morphometric analysis and inferential statistical tests to support our ichnotaxonomic revisions. The diagnosis ofUmfoloziais revised, with the description of a new ichnospecies,Umfolozia terere, and the emendation ofUmfolozia riojana(formerlyUmfolozia longula). We revisedWarvichnium, maintaining the originalWarvichnium ulbrichiand allocating two morphologies to the ichnogenusIrichnus:Irichnus saltatoriusandI. paripinnatusisp. nov. These trace fossils record several behaviours, and have implications for palaeoenvironmental interpretations and the evolution of invertebrate ecosystems. UsingUmfoloziaandWarvichniumas case studies, we demonstrate the application of morphometric analysis in ichnotaxonomy and highlight this as a tool that may be applied to other trace‐fossil groups.

Morphometric analysis of pebbles in verification of transport processes and interpretation of palaeoenvironment: A case study from the Ogwashi Formation (Oligocene), Niger Delta Basin, Nigeria

The present paper discusses a palaeoenvironmental interpretation of the Oligocene Ogwashi Formation (Niger Delta Basin, Nigeria) through morphometric analysis of pebbles, a research method essentially depending on the quantitative evaluation of pebble size and shape which change during transport processes in a range of depositional environments. The relationship of bivariate and ternary-diagram plots of independent functions was determined from freshly exposed sandstone sections in quarries at Ibusa, near Asaba, Nigeria. The grain size of pebbles ranges from fine (11.00 mm) to very coarse (41.33 mm), with a mean size of 21.05 mm (coarse pebbles). A bivariate plot of the flatness index vs maximum projection sphericity index shows 37% of the pebbles to fall within a beach (marine) environment, and 33% within a fluvial environment; the remaining 30% are uncertain. The maximum projection sphericity index vs oblate-prolate index bivariate plot indicates that 47% of pebbles fall within a marine environment and 22% within a fluvial environment, while the remaining 31% are uncertain. The sphericity-form ternary diagram plot shows that the pebbles primarily comprise bladed, platy, very bladed and very platy of near-equal proportions with minor elongate and very elongate stones, which suggests that the pebbles are diverse in origin. The sphericity-form bivariate plot indicates that the pebbles are largely of disc and blade shapes with a minor number of spherical and rod shapes. The near-equal proportion of pebbles in different segments of the bivariate and ternary diagram plots, and the wide distribution of the pebble grain sizes and shapes suggest the Ogwashi Formation is composed of redeposited sediments that likely were transported and deposited in a mix of marine and fluvial settings with possible transitional environments. In other words, the pebbles can be interpreted as marine-influenced fluvial sediments in marginal-marine settings.

New 14C data of megafaunal remains from Lithuania – implications for the palaeoenvironmental interpretation of the Middle Weichselian

Palaeobiological data, supplemented by new 14C dates in conjunction with palaeobotanical and lithological information, have allowed reconstruction of Middle Weichselian (MIS 3) environmental fluctuations in the southern Eastern Baltic region. Palaeoenvironmental reconstructions implying non-glacial conditions during the Middle Weichselian (MIS 3) are supported by the spatial and temporal context of recently discovered remains of Mammuthus primigenius Blumenbach and Rangifer tarandus Linnaeus, 1758. Recording both cold and warm climatic reversals of MIS 3, representatives of the megafauna thrived in an environment characterized by a heterogeneity of vegetation and climate. 14C dating shows that the majority of the megafaunal remains analysed represent the 38–45 cal kyr BP time-interval, which correlates with the Nemunas 2c cold interval (cryomer), and the 31–34 cal kyr BP or Mickñnai 3 thermomer. From pollen data, the palaeovegetation pattern varied from tree-less tundra to birch-predominating forest with an admixture of temporal tree species providing additional information about the diet and habitat preferences of these herbivores in the context of the MIS 3 climatic events.

Flower inclusions of Canarium (Burseraceae) from Miocene Zhangpu amber (China)

The Miocene amber from Zhangpu (Fujian Province, southeastern China) has recently displayed a significant palaeobiodiversity with numerous inclusions of insects, fungi, angiosperms as well as a few gastropods and feathers. In this paper, we investigate for the first time flower inclusions from the Zhangpu amber, using synchrotron-radiation-based X-ray micro-computed tomography (SRμCT). Our results show that both flowers are morphologically bisexual but functionally male, whorled, and trimerous. The perianth is differentiated into a synsepalous calyx and a polypetalous corolla. The obdiplostemonous androecium comprises six connate stamens forming a staminal tube around a fleshy nectary disk and an aborted syncarpous gynoecium with a superior ovary. Both flowers also share a subtending bract, a pair of bracteoles and secretory ducts. We recognize two new fossil species of Canarium, C. wangboi n. sp. and C. leenhoutsii n. sp., distinguished from one another by the shape, length and extent of fusion of the calyx, the shape and length of the corolla, the fusion and length of the staminal tube and the shape of the nectary disk. The genus, which belongs to the Burseraceae family, is nowadays distributed pantropically in the warm regions of Africa, Asia and Northeast Oceania. This study represents the first fossil record of Canarium flowers and gives new insights into the diversity of the Zhangpu amber forest. Moreover, it supports the palaeoenvironmental interpretation of the sedimentary plant fossils deriving from the amber bearing layer, indicating a warm and humid climate in Zhangpu during the Mid-Miocene Climatic Optimum.

Tropical forests and Combretaceae woodland at Usno in the Lower Omo Valley (Ethiopia), 3.3–3.2 Ma ago

In this paper, we describe anatomical structures of 11 fossil wood samples collected from two localities (Brown Sands and Flat Sands) of the Usno Formation, in the Lower Omo valley, Ethiopia. On the basis of former stratigraphy and new investigation, notably Ar/Ar dating of intercalated tuffs and palaeomagnetic studies, the samples are dated between 3.33 and 3.21 Ma. The identified wood samples have been collected within two distinct stratigraphic layers deposited during this time range. The oldest one from Brown Sands includes Albizia sp., Entada sp. and a possible Combretaceae or Leguminosae. The youngest assemblage from White Sands includes many representatives of Combretaceae including Combretum molle and Terminalia sp. associated with Erythrina sp. These assemblages strongly differ from other Miocene and Pliocene wood assemblages known from Ethiopia. Palaeoenvironmental interpretation of the identified tree taxa support affinities with the extant mid-elevation Albizia forest replaced by Combretum/Terminalia woodland in about one hundred thousand years. In the Lower Omo valley, the more humid character of the Pliocene vegetation strongly contrast with the arid Acacia/Commiphora steppe widely spread over the region today. Such past vegetation attests to much wetter and favourable climatic conditions under seasonal climate. However significant changes in the floristic composition of tree cover occurring within a timespan of hundred thousand years, plays in favour of climatic and palaeo-environmental instabilities at a time when Australopithecus afarensis existed in the Turkana basin and flourished elsewhere in Ethiopia.

Radiaxial fibrous calcite forms via early marine‐diagenetic alteration of micritic magnesium calcite

ABSTRACTMarine radiaxial fibrous calcites are common pore‐filling carbonate fabrics in Palaeozoic and Mesozoic carbonates, yet recent analogues are scarce. Although ancient marine radiaxial fibrous calcites are often considered a cement phase and used for palaeoenvironmental interpretations, their origin (primary precipitation versus diagenetic alteration of a pre‐existing fabric) and their specific formation processes remain ambiguous. This may be related to insufficient information from a few recent analogues and limitations of traditional methods in investigating ancient radiaxial fibrous calcites. This study documents a Holocene occurrence of marine pore‐filling radiaxial fibrous Mg calcites and focuses on their origin, formation processes and implications for ancient analogues. The radiaxial fibrous Mg calcites examined in this study share morphological and mineralogical similarities with numerous ancient marine radiaxial fibrous calcites with a Mg calcite precursor. Based on petrological and geochemical data, the radiaxial fibrous Mg calcites are interpreted as secondary porewater products formed during early burial alteration of micritic Mg calcite precursor cement. These findings provide implications for, at least in part, ancient marine radiaxial fibrous calcites in the context of the formation process and mechanism and are relevant for palaeoceanographic and palaeoenvironmental interpretations based on the presence of this carbonate phase.

Sediment geochemistry of the section Tagay-1 at Olkhon Island (Lake Baikal, Eastern Siberia): a contribution to palaeoenvironmental interpretations

The Miocene Tagay section in the north-western part of Olkhon Island, Lake Baikal, provides a unique window into past life in northern Asia. To aid palaeoenvironmental reconstructions, we carried out whole-rock geochemical analyses of 17 sedimentary layers of this section. The aim of this geochemical approach is to examine the element variations as a response to climate change during formation of the Tagay section deposits with a focus on the hydrological regime of the catchment and in-lake processes. Our results establish that temperature and climate conditions during the formation of sediments of section Tagay-1 were fairly stable, no abrupt climatic changes occurred. The palaeoclimate was temperate, however, it had a cyclic nature: wet and semiarid epochs of different intensity and duration alternated. The basal part of the sediment sequence is dominated by terrigeneous material, mainly by surface runoff, so the sedimentation was fed by erosion products of the weathering crust. During sedimentation of this lower part (layers 17–9), the palaeo-lake level and salinity stayed practically unchanged. The drawdown of the palaeo-lake and increasing salinity started in the higher middle part (layer 8), and reached the minimum water level and maximum salinity in layers 7–6. Sediments of the layers 8–6 accumulated in an arid climate. After deposition of layer 5, the water level began to rise, and during formation of layer 3 it fell again. The highest sedimentation rate was in layers 12–5, these are also the layers with the highest enrichment of biogenic elements (layers 12, 7–5) and where carbonate deposition took place. The observed changes in element behaviour are related to hydrological changes in the catchment (precipitation), lake level status, and evaporation, and are ultimately driven by climate.

A new species of Pleuromeia (Lycopsid) from the upper Middle Triassic of Northern China and discussion on the spatiotemporal distribution and evolution of the genus

Pleuromeia Corda is an iconic lycopod genus in the Early Triassic floras of the world. Pleuromeia fossils are very significant in stratigraphy and palaeoenvironmental interpretation and have been regarded as an important Lower Triassic index fossil. Although some recent studies show that the genus occurred in the lower part of the Middle Triassic, no definite Pleuromeia has been reported from the late Middle Triassic and the younger strata so far. In this paper, some reproductive organ fossils of Pleuromeia from the upper Middle Triassic Tongchuan Formation in Shaanxi Province (belonging to the Ordos Basin), North China, are described for the first time, belonging to the new species Pleuromeia obovata Deng nov. sp. Highly accurate dating results of tuff layers indicate that the age of the new species is between 241.06 ± 0.12 Ma and 241.558 ± 0.093 Ma, equivalent to the early Ladinian. This is the youngest species of genus Pleuromeia so far. Spatiotemporal distribution of Pleuromeia indicates that the genus first appeared in the Induan (Early Triassic) in North China, occurred widespread and flourished in both Laurasia and Gondwana during the Olenekian (late Early Triassic), declined from the Anisian (early Middle Triassic), survived in the Ladinian in North China, and may have gone extinct as early as the end of the Middle Triassic. North China may well have included the place of origination and the last habitats of this genus.

A classification scheme for sedimentary architectures arising from aeolian-fluvial system interactions: Permian examples from southeast Utah, USA

• Novel classification scheme for types of aeolian-fluvial interaction in ancient erg deposits. • Scheme applied to outcrops of Permian Cutler Group to enable 3D architecture analysis. • Classification scheme is generally applicable. • Classification scheme assists palaeoenvironmental interpretation. The preservation of the sedimentary deposits of arid environments is determined by both geomorphic and geologic processes. Sedimentary evidence of aeolian-fluvial system interactions in arid-climate settings are preserved in both recent and ancient sedimentary successions. However, despite considerable prior sedimentological research, there is no unifying scheme to provide generalized definitions of commonly occurring types of preserved aeolian-fluvial interactions. This study addresses this shortcoming by introducing a novel classification scheme for sedimentary architectures arising from such system interactions. The scheme is demonstrated through reference to examples from the Permian Cutler Group, Paradox Basin, Southeast Utah, USA – a sedimentary record of competing aeolian dune-field and fluvial-fan systems along a palaeo-coastline. Well-preserved, laterally continuous outcrops arranged in different orientations enable three-dimensional architectural characterization. The sedimentary record of eight distinct types of aeolian-fluvial interaction are identified: (i) water-table-controlled interdune sedimentation; (ii) deposits of low-energy fluvial floods; (iii) isolated fluvial channel-fills originating from episodic and confined flooding of interdunes in orientations parallel to the trend of dune crestlines; (iv) channel fills oriented perpendicular to the trend of dune crestlines; (v) amalgamated fluvial channel elements resulting from persistent, long-lived but confined dune-field flooding; (vi) deposits of unconfined sheet-like flood deposits; (vii) fluvial breaching of dunes and their reworking by catastrophic flooding; (viii) aeolian reworking of fluvial deposits. Each interaction type is characterized in terms of preserved sedimentary facies, architectural element geometries and associated proprieties, to demonstrate sedimentary variability in three dimensions. Results provide a guide with which to make sedimentological comparisons and interpretations between active systems and their preserved depositional record.

Sequence stratigraphy of the upper Oligocene–middle Miocene succession in west–central Sinai, Egypt

The calcareous nannofossil and foraminiferal analyses have been integrated to build a detailed chronostratigraphic scheme for the upper Oligocene–middle Miocene succession in the Nukhul–Sudr area, west–central Sinai, Egypt. The palaeoenvironmental conditions of the studied succession were assessed using the palaeoecologic preferences of calcareous nannofossil species, benthic foraminifera, and planktonic/benthic (P/B) ratios. Six complete and two incomplete depositional sequences bounded by seven sequence boundaries have been distinguished in the studied sections based on the integration between chronostratigraphic and palaeoenvironmental interpretations as well as the nature of stratigraphic surfaces. Levels suggesting subaerial exposures (such as alluvial fans and polymictic conglomerates) and biostratigraphic breaks were employed to delineate sequence boundaries. The inferred relative sea‐level curve points to palaeodepth change ranging from lagoonal to outer shelf settings during the deposition. The established upper Oligocene–middle Miocene sequence stratigraphic framework demonstrates a more‐or‐less compatible correlation toward the corresponding ones from the neighbouring localities around the eastern rim of the Gulf of Suez. However, the inferred relative sea‐level curve shows significant deviations when compared with the eustasy. These deviations are expressed mainly by several prolonged time gaps and discrepancies in the timing and magnitude of the transgression and regression events. Therefore, the Gulf of Suez rift Basin development and the coincident regional tectonic events are the main controlling factors for the sedimentation regime in west–central Sinai.

Timing and stratigraphic evolution of a Miocene foreland unroofing sequence in the Austral–Magallanes Basin during Southern Patagonian Andes uplift

Detrital zircon U–Pb geochronology is a widely used technique for interpreting sedimentary provenance in basin systems. This, combined with detailed sedimentary facies interpretation and stratigraphy evolution, has been extensively applied in foreland basin settings to understand tectonic processes by tracking the exposure and erosion of distinct sediment source areas through time. We present a case study in the Miocene foreland sedimentary record of the NW Austral–Magallanes Basin ( c. 47° 30′ S), which is associated with the main phase of Andean uplift. We define three sedimentary units (SU) for palaeoenvironmental interpretation from shallow-marine deposits (SU-I) to mixed-load fluvial deposits (SU-II) to an alluvial fan (SU-III). Also, we constrain the timing of this synorogenic clastic wedge between c. 20 and c. 12 Ma applying U–Pb zircon maximum depositional ages of six sandstones and one tuff sample. From detrital zircon provenance analysis, we document a progressive upsection loss of contribution from younger units and an enrichment of older units derived from hinterland sources, suggesting the development of an unroofing erosional process owing to coeval Andean uplift of the cordilleran sources. Tectonostratigraphic stages determine the initial stages of orogenic uplift (Stage 1), the subsequent advance of the orogenic belt and progressive loss of accommodation space (Stage 2) and finally foreland clogging (Stage 3). Supplementary material: Geochronological U–Pb isotopic ratios are available at https://doi.org/10.6084/m9.figshare.c.6132000

Palynostratigraphy, biochronology and palaeobathymetry of a section of Awaizombe-1 well, eastern Niger Delta, Nigeria

ABSTRACTDitch cuttings (69 samples) from a section of Awaizombe-1well located in the Northern Depobelt of the eastern Niger Delta Basin were used for this study. The lithology of the studied interval 1373–1812 m (439 m thick) consists of fissile grey shale and mudstone units. The scid method of sample preparation for palynormorphs’ recovery was adopted. Analysis recorded a well-preserved and diverse assemblage of palynomorphs, rich in pollen, spores and dinoflagellate cysts (dinocysts). First and last occurrences of marker and age diagnostic species were used for palynostratigraphic interpretation. Four palynostratigraphic interval range zones were established: Psilatriporites sp.–Racemonocolpites hians Zone; early Oligocene (Rupelian age), Praedapollis africanus–Doualaidites laevigatus Zone; late Eocene (Priabonian age), middle Eocene (Lutetian and Bartonian ages), Doualaidites laevigatus–Praedapollis flexibilies Zone; and early Eocene (Ypresian age), Verrucatosporites usmensis–Retitricolpites ituensis Zone. The first downhole occurrence of D. laevigatus at the 1482 m marks the late Eocene/early Oligocene boundary. Established zones are useful for inter and intra basins correlation. Lithology and age of the studied section are suggestive of the lower Agbada Formation. Palaeoenvironmental interpretations using diagnostic species revealed two environments: brackish and inner neritic to upper bathyal (0–600 m) under relatively warm-water marine condition indicated by thermophilic dinocyst taxa, such as Lingulodinium machaerophorum, Polysphaeridium zoharyi and Homotryblium spp. The lithology and these types of environments are good sites for hydrocarbon generation.