Cretaceous Basin Research Articles

Plateau archives of lithosphere dynamics, cryosphere and paleoclimate: The formation of Cretaceous desert basins in east Asia

Southeastern Eurasia is a global window to the Cretaceous paleoclimate and lithosphere coupling. China contains one of the most complete and complex sedimentary records of Mesozoic desert basins on planet Earth. In this study, we perform the spatio-temporal tracking of 96 Cretaceous palaeoclimate indicators during 79 Myr which reveal that the plateau paleoclimate archives from East Asia resulted from an Early to Mid-Cretaceous ocean–atmosphere coupling and a shift to a preponderant role of Late Cretaceous lithosphere dynamics and tectonic forcing on high-altitude depositional systems linked to the subduction margins of the Tethys and Paleo-Pacific realms beneath the Eurasian plate. The crustal response to tectonic processes linked with the spatio-temporal evolution of the Tethyan and Paleo-Pacific margins defined the configuration of major sedimentary basins on this region. The significant increase and decrease in the number of active sedimentary basins that occur during the Cretaceous, from 16 in the Early Cretaceous, to 28 in the Mid-Cretaceous, and a decreasing to 20 sedimentary basins in the Late Cretaceous, is a direct response of lithospheric dynamics associated with the two main subduction zones (Tethys and Pacific domains). A shift in subduction style from an Early Cretaceous Paleo-Pacific Plate slab roll back to a Late Cretaceous flat-slab mode might have triggered regional plateau uplift, blocked intraplate volcanism, thus enhancing the denudation and sediment availability, and created wind corridors that led to the construction and accumulation of extensive Late Cretaceous aeolian sandy deserts (ergs) that covered Mid-Cretaceous plateau salars. At the same time, plateau uplift associated with crustal thickening following terrane assembly in the Tethyan margin triggered altitudinal cryospheric processes in sandy desert systems. Evidence of an active Cretaceous cryosphere in China include Valanginian-Hauterivian glacial debris flows, Early Aptian geochemical signature of melt waters from extensive ice sheets, and Cenomanian–Turonian ice-rafted debris (IRD). These cryospheric indicators suggest an already uplifted plateau in southeastern Eurasia during the Cretaceous, and the marked correlation between cold plateau paleoclimate archives and marine records suggests a strong ocean-atmosphere coupling during Early and Mid-Cretaceous cold snaps. We thus conclude that lithospheric tectonics during Cretaceous played a fundamental role in triggering high-altitude basin desertification and spatio-temporal plateau paleohydrology variability in the Cretaceous of south-eastern Eurasia.

Early Cretaceous provenance-depositional systems and volcano-sedimentary responses to strike-slip faulting in southern Jilin and eastern Liaoning provinces, NE China: a case study of the Tonghua Basin

ABSTRACT Understanding how the sedimentary responses adapt to the structural styles of fault basins in the strike-slip fault systems is one of the key goals of basin analysis. Variability of volcanic and epiclastic provenance-depositional systems and tectonic controls of the Lower Cretaceous Hengtongshan Formation in the Tonghua Basin are crucial to determine the evolution of the fault basins and wrench tectonics in southern Jilin and eastern Liaoning provinces (SJELP), NE China. Study of volcanism-induced sedimentation, composition plot, and depositional systems elucidates the sequence stratigraphy and volcano-sedimentary responses to wrench tectonics based on cores, outcrop sections, and seismic profiles of the Tonghua Basin. Two types of provenance-depositional systems (volcanic and epiclastic) were reconstituted using eight lithofacies and seven lithofacies associations. Of the lithofacies, six pyroclastic lithofacies and two epiclastic lithofacies were identified based on compositions, textures, and sedimentary structures. The presence of these lithofacies in different vertical successions was described as different lithofacies associations to interpret depositional processes and sedimentary environments. Depositional-system maps of the three sequences in the Hengtongshan Formation and analysis of structural framework indicate that volcanism and sedimentation were controlled by wrench faulting. Statistical analysis of rock compositions reveals that the deposition of the Hengtongshan Formation shows mixed contribution from both the volcanic and granitic fragments. Triangular compositional plots of detrital composition suggest a diverse provenance by straddling the litho-feldspatho-quartzose (lFQ), feldspatho-litho-quartzose (fLQ), feldspatho-quartzo-lithic (fQL), and quartzo-feldspatho-lithic (qFL) fields, indicating that the sources were derived from uplifted basement blocks and volcanic eruptions in a rift basin related to strike-slip faulting. The Tonghua Basin developed as a wrench-fault basin on the east side of Dunhua–Mishan Fault systems (DMF). This model for the Tonghua Basin can be used to understand the Liuhe Basin in the DMF and other Early Cretaceous basins in adjacent areas.

Geomorphic indices, machine learning and osl-palynology chronology to assess neotectonic deformation in the continental margin – Northeastern Brazil

The continental margin of Northeast Brazil (NE Brazil) is the most seismogenic of the passive margin of South America and has several evidence of neotectonics. However, the duration and magnitude of neotectonic events cannot be uniformly replicated for a scale of ∼3000 km of extension. Therefore, this study aimed to understand the tectonic dynamics, especially from Neogene to recent, for a region little studied in this scope. We conducted multiscale analysis: landforms, sub-basins, drainage systems, and sedimentary outcrops. Applying a multi-technical approach: geomorphic indices (Stream Length-Gradient-Sl, Channel Steepness ksn, Basin Asymmetry Factor); use of Machine Learning Algorithms (ML) for spatialization of Sl and ksn indices; and OSL-palynology chronology. The results indicate multiphase tectonic control occurring by reactivation of geological faults from the Cretaceous to the recent, affecting shear zones, Cretaceous Basins, and Miocene deposits (Barreiras Formation). In these areas, predictions by ML (Sl and ksn indices) showed high values associated with fault zones, which confine and direct drainage, and landforms conditioning ungraded river long-profiles and tilted sub-basins. Tectonic deformations also manifest at the outcrop scale, with strata showing deformations (folds, joints, and atypical dips). Furthermore, strata with marine palynomorphs (Miocene) and Pleistocene-Holocene sediments (Post-Barreiras) in an altitudinal position above ∼38 m above sea level suggest post-depositional movement. The multiscale and multi-technical approaches showed that tectonic activity acted in different periods. Notably, the spatial prediction of geomorphic indices with ML is potentially competent in regional analyzes of neotectonics.

Delineating structural features of North Cameroon using the EIGEN6C4 high‐resolution global gravitational model

The Cretaceous basins of the West and Central African Rift System (WCARS) are characterized by sinistral strike–slip movements observed between the Benue and Arabian–Nubian microplates. These basins share a similar basin‐filling structure, history, and tectonic processes. They have attracted a significant interest in the study of their geodynamics and subsurface structure through geophysical exploration methods. Nevertheless, North Cameroon located in this microplate confluence has not yet been investigated in terms of identifying geological structures, such as lineaments and faults. To contribute to a better understanding of the northern Cameroon structural framework and its tectonic context, we investigate the lineaments in northern Cameroon by using the EIGEN‐6C4 gravitational model and a variety of recent processing techniques (Tilt derivative [TDR], Theta Map [TM], Horizontal tilt angle [TDX], and Edge Detector [ED]). Our results show that the lineaments are trending in ENE–WSW, NW–SE, NE–SW, and WNW–ESE directions. These directions are consistent with the Cretaceous Garoua Rift and granitoids of the Cameroon‐Chad line. The presented result clearly delineates continuous architectonic features of the structural edges of the Saharan Metacraton, the Cretaceous Garoua Rift, the Bibemi‐Léré granitoids, and the Adamawa faults.

Comparison of shale depth functions in contrasting offshore basins and sealing behaviour for CH 4 and CO 2 containment systems

Mudrock compaction trends from the Rovuma Basin offshore Mozambique are compared with those of the Norwegian North Sea, the Gulf of Mexico and the Kutai Basin offshore Indonesia. The comparison reveals that burial rates and timing of rifting are the dominant causes for the differences observed. The compaction trend for the Rovuma Basin is broadly similar to the trends for the Kutai Basin and the Gulf of Mexico, but very different from those for the Norwegian North Sea data, which show higher porosity and shallower onset of overpressure than those from the other three basins. The relationships for seismic velocities as a function of depth show strong similarities between the Rovuma and Gulf of Mexico basins. These comparisons are used to make a general assessment of the capillary sealing potential of Cretaceous mudrocks in the Rovuma Basin, using a mudstone permeability-prediction function and a method for mapping permeability to threshold pressure, allowing estimation of maximum column heights for CO 2 and CH 4 , with uncertainty ranges. Predicted CO 2 column heights are slightly less than the equivalent CH 4 column heights. The observed CH 4 column height at one of the wells is significantly lower than that predicted from mudstone permeability, which is probably due to other factors such as fracturing or gas migration out of the structure. The comparison indicates generally good capillary sealing potential for the Rovuma Basin Cretaceous shales and offers a general approach for assessing CO 2 storage potential from hydrocarbon sealing datasets from multiple offshore basins. This article is part of the Energy Geoscience Series available at https://www.lyellcollection.org/cc/energy-geoscience-series

Reply to the discussion of Moustafa (2021) on Sayed et al. (2020) (Marine and Petroleum Geology, 17, 2020-104401)

Moustafa (2021) addressed four main comments in his discussion “On the structures of Abu Roash area and inverted basins of northern Egypt - Comments on “Surface expression of the Syrian Arc Kattaniya inverted basin in the Abu Roash area, northeast Western Desert, Egypt: Structural style and tectonic history” by Sayed et al. (2020)”. Two of these comments criticized the new structural mapping of Abu Roash outcrops and the proposed model for El Ghigiga-El-Hassana Folds based on the early geologic mapping of the Abu Roash area by Moustafa (1988). His other comments were concerning the NE-orientation and end of tectonic inversion of the extensional Jurassic -Lower Cretaceous basins in North Egypt including the Kattaniya basin. Except for two constructive memos on drafting errors in the regional geologic map of Abu Roash, the registered comments were inaccurate and can be refuted with the results of the comprehensive regional and integrated subsurface geologic mapping on the North Western Desert basins, the previous works of Moustafa and his collaborators and the figures included in his discussion as we will present in this reply. It was documented that the inversion time, intensity, and type (orthogonal versus oblique or compressional versus transpressional/transtensional) differ from one basin to another in the northern part of Egypt. The geologic structures of Abu Roash helped to define a transpressional (oblique) inversion tectonic model that started at the Santonian and ended by the Latest Senonian. This tectonic model represents the northeastern segment of the Kattaniya basin and does not generalize to the whole basin or other basins in North Egypt.

Stratigraphy and palaeoenvironments in the upper Turonian to lower Coniacian of the Saxonian Cretaceous Basin (Germany)– insights from calcareous and agglutinated foraminifers

Upper Turonian to lower Coniacian marls of the Strehlen Formation of the Graupa 60/1 core were investigated for their foraminiferal content to add stratigraphical and palaeoenvironmental information about the transitional facies zone of the Saxonian Cretaceous Basin. Further comparison with foraminiferal faunas of the Brausnitzbach Marl (Schrammstein Formation) were carried out to clarify its relationship to the marls of the Graupa 60/1 core. Tethyan agglutinated marker species for the late Turonian to early Coniacian confirm the proposed age of the marls of the Graupa 60/1 core and the Brausnitzbach Marl. The palaeoenvironment of the marls reflects middle to outer shelf conditions. The maximum flooding zones of genetic sequences TUR6, TUR7 and CON1 could be linked to acmes of foraminiferal species and foraminiferal morphogroups. In general, a rise of the relative sea-level can be recognised from the base to the top of the marls of the Graupa 60/1 core. While agglutinated foraminiferal assemblages suggest a generally high organic matter influx and variable but high productivity in the Graupa 60/1 core, the Brausnitzbach Marl deposition was characterized by moderate productivity and a generally shallower water depth.

Digital structural-lithological model and geological-genetic characteristics of Kopytkovsky phosphorite deposit

Introduction. The relevance of this publication is associated with the problem of foundation and developing a raw material base of phosphate raw material in accordance with the demand of the national agro-industrial complex. The purpose of the publication is to develop a preliminary digital structural-lithological model (DSLM) of the Kopytkivsky deposit, as a tool for information support of its development, as well as geological and genetic characteristics of the object as a basis for specifying the criteria for predicting deposits of this type. This goal covers the following tasks: - presentation of methodology and research methods; - presentation of the database; - demonstration of derivatives of the created digital structural-lithological model (DSLM) and their interpretation;- representation of functional and cognitive characteristics of the object (Kopytkivsky phosphorite deposit). Materials and Metodology. The studies are based on two methodological principles: traditional lithological, paleofacial, paleogeographic studies and the author's development - digital structural and lithological modeling, dialectically combined in the form of a single predictive-paleoreconstructive retrospective-static model. Main Results. Kopytkivsky deposit belongs to the Zdolbunovskiy district of the Zdolbunovskiy-Ternopil zone of the Volyn-Podolsk Cretaceous basin of the phosphorite-bearing province of the East European platform. The indicated zone refers to the Volyno-Podilllya plate, i.e the western slope of the Ukrainian shield. In the area of the Kopytkivsky deposit, layers of inoceramic limestones represent the lower stratigraphic subdivision of the Cretaceous system, lying directly on the pre-Mesozoic basement. The DSLM of the Kopytkivsky field has been developed, intended for information support for further work on its development (detailed exploration and operation). The DSLM database is represented by a description of 567 geological exploration wells. Conclusions. Based on the constructed DSLM, a number of derivatives (including visualizations) were obtained that reflect the structural and material - industrial characteristics of the field - a number of maps, profiles, as well as a block diagram of the central part of the field. The description of the most informative visualizations are given: Map of the hypsometry of the bottom of the "productive horizon", Map of the hypsometry of the roof of the "productive horizon", Map of specific reserves and others. The model derivatives reflect the spatial (areal and hypsometric) configuration of phosphorites ore bodies and the distribution of specific reserves of P2O5. Based on the methodological principles of formation analysis and the methodological approaches adopted by us for predictive-paleoreconstructive retrospective-static modeling of the object, a geological and genetic characteristic of the stage of formation of layers of inoceramic limestones has been obtained. The mechanism of phosphorite formation is considered. The presented DSLM is intended for information support of detailed and operational exploration, with the prospect of the current development of the model (as a permanent one) with the addition of new data during exploration and operational work.

Groundwater Hydrochemical and Isotopic Evolution from High Atlas Jurassic Limestones to Errachidia Cretaceous Basin (Southeastern Morocco)

The objective of this research was to determine the recharge of the Cretaceous aquifers by the High Atlas, as well as the interaction and possible mixing phenomena between the waters of the different aquifers, by investigating the hydrochemical and isotopic evolution of groundwater flow paths from the limestone karst systems of the High Atlas to the Cretaceous basin of Errachidia. Geological techniques were used to investigate and confirm the chemical and isotopic characteristics of the waters. Although the Gibbs diagram shows that water–rock interaction is the dominant hydrochemical process, some water samples in the Cretaceous basin are influenced by both evaporation and water–rock interaction, indicating a mixture of rainfall and deep waters. A saturation index study indicated that limestone minerals were supersaturated in parts of the groundwater samples (calcite and dolomite). This result was confirmed by isotope data. Indeed, some Cretaceous basin samples show isotopic similarities to those from the Jurassic High Atlas. The geological cross-sections illustrate that the High Atlas Jurassic limestones are in direct contact with the Cretaceous basin’s permeable rocks, allowing groundwater to circulate from the High Atlas to Errachidia’s Cretaceous basin.

Tectonic evolution and subsidence history of the Cretaceous basins in southern Egypt: The Komombo Basin

AbstractThe structure and tectonic evolution of the Cretaceous rift basins of southern Egypt are poorly understood. In this study, the tectonostratigraphy of the Komombo Basin has been determined using seismic, well and biostratigraphic data. The tectonostratigraphy of the basin is compared to the Kharit, Nuqra and Beni Suef basins in Egypt as well as Muglad Basin in Sudan. The Komombo Basin is a 58 km long, 28 km wide NW–SE trending half‐graben infilled with 2200 m of Berriasian‐Maastrichtian sediments and overlain by 400 m of Pliocene sediments. Four Berriasian to Maastrichtian syn‐rift and post‐rift sequences and three Pliocene channel systems of Nile sediments have been identified. Moreover, a series of normal faults, negative flower structures, reverse faults and folds are mapped in the basin. Backstripping reveals two rift phases during the Berriasian‐Barremian and Turonian‐Santonian, respectively. Additionally, the tectonic subsidence curves indicate that two major unconformities have occurred during the Aptian‐Albian and Maastrichtian‐Pliocene, which are correlated with a basement uplift during the Albian‐Cenomanian and the Oligocene‐Miocene flank uplift related to the opening of the Red Sea, respectively. The rift episodes are attributed to far‐field stress changes resulting from the initial opening of the South Atlantic and followed by the NW part of the African plate colliding and anticlockwise rotating into Europe. The highest β factors (1.20–1.11) for both rift phases are found at the centre of the basin. The rift phases thinned the crust from 32.5 to 28.2 km and 31.9 km in the depocenter and the western flank of the basin. The Komombo Basin has a similar rift history, stratigraphy and structural style to the Kharit, Nuqra and Mugland basins. All of these basins witnessed two major rift phases in the Early and Late Cretaceous, whereas the Beni Suef Basin encountered strike‐slip tectonic events in the Late Cretaceous.

Geological interpretation of a seismic reflection profile in the eastern part of the Bohemian Cretaceous Basin

Geological interpretation of a seismic reflection profile in the eastern part of the Bohemian Cretaceous Basin

Domichnial Borings in Serpulid Tube Walls: Prosperous Benthic Assemblages in the Cretaceous of France and the Czech Republic

The calcareous tubes inhabited by some polychaetes (some Serpulidae and the sabellid Glomerula) which are adapted to live sticking in soft ground, starting from the Permian, represent widespread but widely neglected and understudied substrates for domichnial bioerosion. Serpulids can be considered small macrofauna. However, due to the thinness of serpulid tubes, borings in them are sized in the order of 0.01–0.9 mm in diameter and thus rather considered micropaleontological objects. Extensive and methodologically broad search (vacuum castings studied at SEM; micro-computed tomography) for and study of borings in these specific substrates was performed on material from the Cenomanian of Le Mans area (France) and the Cenomanian and Turonian of the Bohemian Cretaceous Basin (Czechia). It shows that the bioerosive traces can be assigned to the existing ichnogenera Rogerella, Trypanites, Entobia, Maeandropolydora, and Iramena. Somewhat surprising is the frequency and disparity of dwelling borings. Several clues, especially in the more abundant ichnogenera Rogerella, Trypanites, and Entobia, support the hypothesis that the tracemakers of these borings adapted to the small size of their substrates by necessarily staying very small by themselves but nevertheless living to adulthood.

Nový výskyt příbojové facie u Ronova nad Doubravou (kolínský litofaciální vývoj, česká křídová pánev)

A rocky-coast facies in the Bohemian Cretaceous Basin (BCB) are developed mainly in the Kolín lithofacial area at its southern margin. Ronov – the newly described locality – is situated south of Ronov nad Doubravou, on the right bank of the Doubrava river near the St. Kříž church. The outcrop located in a ditch was partially excavated in order to study the character and extent of Cretaceous sediments (Beds No. 1–3; see Figs. 1–3). Bed 1 is composed of red clay with yellow streaks, representing lateritically weathered crystalline bedrock – likely amphibolites and garnet migmatites (Fig. 2). Overlying bed 2 consists of yellow to gray-green clay; in the lower part, the layer contains fragments of fossils that occur in the overlying layer, and sandy “intraclasts” interpreted as bioturbations. The most conspicuous bed 3 (25 cm in thickness) is represented by calcareous, coarse-grained sandstone to conglomerate with glauconite and abundant fauna (mainly fragmentary; Figs. 4 and 5). This type of rock in the wider area (between Ronov nad Doubravou and Žleby) was reported by Sejček (1982) who described three occurrences as scree or fragments on the surface but has not found any rock outcrops in situ despite excavation work. The individual layers were sampled for the study of foraminifers, calcareous nannoplankton and macrofauna. Shells of Rhynchostreon suborbiculatum, which are always disarticulated, often fragmented and bioturbated (Entobia exogyrarum), represent the most prominent element of macrofauna. In addition, Rastellum diluvianum and Amphidonte halitoidea, unspecified large colonies of bryozoans, spines of the echinoids Cidaris vesiculosa, complete shells of brachiopods Cyclothyris aff. difformis and tiny teeth of sharks Otodus rarely occur. Calcareous nannofossils were found only in bed 3. Isolated small, mostly difficult to identify fragments belong to long-range stratigraphic taxa (Fig. 6) and may indicate an interval from the uppermost Cenomanian to the lowermost Turonian. Similar poor nannofossil assemblages are known also in other rocky-coast facies of the BCB. The refining indicator of stratigraphic classification is thus macrofauna. Similar communities with Rhynchostreon suborbiculatum and echinoderms are known from Upper Cenomanian and Lower Turonian in the area of Heřmanův Městec, Čáslav and especially Kutná Hora. However, brachiopods Cyclothyris aff. difformis and oyster Amphidonte halitoidea recorded from Ronov are typical representatives of Upper Cenomanian “rocky-coast” faunas, whereas typically Lower Turonian elements such as the oyster Exogyra reticulata, Exogyra sigmoidea, or the spines of the Cidaris sorigneti are missing in the studied community. The study of macrofossil and nannofossil communities shows that the Upper Cretaceous rocks, represented by the calcareous glauconitic sandstones to conglomerates in Ronov locality, are most likely of the Upper Cenomanian age and represent the Korycany Member of the Peruc-Korycany Formation.

Preliminary source rock evaluation, paleo-depositional environment and hydrocarbon generation potential of the cretaceous organic-rich outcrops of Mayo-Figuil River, Babouri-Figuil Basin, Northern Benue Trough (Yola arm) Cameroon: Insights from bulk geochemistry

Babouri-Figuil sedimentary basin is considered the most northerly and one of the most attractive intracontinental Cretaceous basins in North Cameroon, which contains organic-rich deposits presumed to be oil shale levels. The fieldwork carried out as part of this study enabled to delineate six lithological units mainly consisting of black shales, marls, orange clay, black to grey clays and limestones. Twenty-two samples from the studied section were subjected to bulk organic (Rock Eval pyrolysis) and inorganic (biophiles XRF-trace element) geochemistry to investigate their hydrocarbon generation potential. Field data and organic geochemical analysis of organic matter reveal that three of the six lithological units are potential hydrocarbon source rocks; these are units 1 (1.50 ≤ TOC ≤3.98%), 2 (0.47 ≤ TOC ≤1.17%) and 4 (TOC = 24.74%) consisting mainly of black to grey clays and black shales. These source rocks are discontinuously distributed throughout the studied section with a cumulative stratigraphic thickness of 275 cm. The organic matter contained in unit 1 is mainly Type II/III (182 ≤ HI ≤ 382 mg HC/g TOC) with a significant contribution in Type II kerogen. It is mature (443 °C ≤ Tmax ≤448 °C) at the base (MF-1, -2, -3 and -4) and immature (Tmax = 416 °C < 435 °C) at the top (MF-5). Unit 2 contains early-mature type III organic matter (98 ≤ HI ≤ 155 mg HC/g TOC; 438–439 °C). Organic matter in unit 4 is also early-mature and has generated mainly oil (Type I or IIS). The combination of proxies of biophile trace elements (cross plots Ni/Co vs. V/Ni and V vs. Ni) indicates that this organic matter is of mixed source, both marine and terrestrial origin, deposited under oxic-dysoxic conditions. Thus, subject to further geochemical analyses and given the pessimistic predictions from outcrop samples, these units are conventional effective source rocks in place of the early reported immature oil shale levels.

Plagioptychus (Hippuritida) dominated assemblage from northern Peri-Tethys margin (Bohemian Cretaceous Basin, Cenomanian–Turonian transition)

Rudist bivalves are frequently used as an important tool for stratigraphy and palaeoecological reconstructions in Cretaceous ecosystems. In this study, we partly refine stratigraphic ranges of rudist genera and species reported from the Bohemian Cretaceous Basin (BCB). The first occurrences of Plagioptychus haueri (Teller) and consequently, the entire genus Plagioptychus might be dated to the upper Cenomanian. The research focused on two sites exposing near-shore/shallow-water deposits, located in the north-western part of BCB. This area represents palaeobiogeographical boundary between Tethyan and Boreal Realms. Here, the Tethyan rudist fauna reaches its northern limits within the Peri-Tethyan shelfs in Central Europe. Revision resulted in detection of the following rudist species: Plagioptychus haueri, Radiolites bohemicus (both already recognised), Petalodontia aculeodentata, Radiolites sanctaebarbarae and Radiolites saxoniae. Furthermore, large numbers of rudist fragments assignable to Hippuritidina suborder, corals and other macrofauna have been detected. Localities described herein are possibly of upper Cenomanian age, even though lower Turonian origin of some of the material deposited in studied localities cannot be excluded. We assign this taphocenosis with co-occurrence of rudist and coral fauna to ‘Coral-Rudist Lithosomes’ with two distinctive rudist eco-morphotypes typical of different substrate types and/or environments. Additionally, we discuss stratigraphical position of several taxa within the context of the entire Bohemian Cretaceous Basin.

Application of μXRF analysis on the Upper Cretaceous Mancos Shale: A comparison with ICP-OES/MS

This study investigates the elemental signature of fine-grained sedimentary rock (mudstone) obtained using energy-dispersive micro-X-ray fluorescence (μXRF). A short section (28.5 cm) of Upper Cretaceous Mancos Shale was analysed with an Itrax μXRF core scanner at 0.2 mm intervals for comparison to elemental and petrographic composition. Fifteen subsamples were collected at 2 cm intervals for ICP-OES/MS analysis to obtain absolute concentrations of elements and oxides, and thin sections were used for petrographic and microfacies analysis. The data obtained from the Itrax core scanner show a high level of reproducibility between separate scans and moderate to strong Spearman-Rho correlation (R2 > 0.6) to ICP-derived concentrations for several oxides: Fe2O3, SiO2, Al2O3, K2O, TiO2, and MnO. Common elemental ratios used in palaeoenvironmental studies (e.g., Zr/Rb, Ca/Ti, Mn/Ti) also showed good correlation to ICP-derived data when the trends were compared. The elemental signature obtained from the Itrax also showed good relationships to the petrography and lithology, with the Si/Ti ratio accurately identifying quartz-rich layers, and the Ca/Ti and Mn/Ti ratios corresponding to increased carbonate content, which are of importance in the planning of hydraulic fracturing for unconventional resources. At core scale, the elemental trends in Zr/Rb, Ti, and Si were useful for detecting short-term, rapid patterns of sedimentary events, likely resulting from storm activity (e.g., tempestites, wave-enhanced sediment gravity flows). The high-sampling resolution data from μXRF core scanners can provide advantages over traditional geochemical techniques since data aliasing is minimized. Analysing these elements and ratios in longer core sections from the Mancos Shale may serve as a proxy for determining high-frequency climatic changes in the Cretaceous Interior Seaway and allow for improved correlations of intra- and inter-basinal events in other Cretaceous basins.

Pläner: a traditional building stone in Saxo-Bohemian Cretaceous and Münsterland Cretaceous Basin

Pläner: a traditional building stone in Saxo-Bohemian Cretaceous and Münsterland Cretaceous Basin

Terrestrial records of Early Cretaceous paleoclimate fluctuations in the Yin'e Basin, northern China: Evidence from sedimentology and palynomorphs in lacustrine sediments

Rapid changes in paleoclimate in the Early Cretaceous had profound impacts on the global ecosystem, which is recorded not only in marine sediments but also in coeval sediments deposited in continental lake systems. This study performed the lake sedimentary characteristics and paleontological data of the upper member of Bayingebi Formation (K1b2) of Lower Cretaceous in the Yin'e Basin (North China) and revealed the paleoclimate disturbances and the evolution of paleovegetation and paleoenvironment recorded in the continental lake. The sediments of K1b2 can be divided into 10 kinds of lithofacies according to grain size, sedimentary structure and overall lithofacies. The three lithofacies associations are nearshore subaqueous fan, semi-deep lake/deep lake and shallow lake respectively. Seventy-eight palynomorph genera and two hundred and thirty-one palynomorph species were identified in the K1b2 samples, which allowed distinguishing 3 palynozones. The sporopollen spectrum and the ecological characteristics of sporopollen parent plants indicate that there was abundant temperate coniferous forest vegetation during the deposition of Bayingebi Formation. The mixed phenomenon of a few cold-loving molecular spores and pollen such as spruce, cedar and fir with tropical and subtropical spores and pollen suggest vertical zoning of plants. It is inferred that the ground shape and height difference around Yin'e Basin in Early Cretaceous is large, and there may be paleogeomorphic features of high mountains, and the paleoclimate has vertical zoning. The K1b2 depositional period was mainly in the warm temperate-temperate paleoclimate background, and oil shale was mainly developed in the semi-humid warm temperate climate. The suitable paleotemperature and the sedimentary environment of semi-deep lake/deep lake provide rich organic matter sources and good preservation conditions for the formation of oil shale. The dropstone structures commonly found in the lower strata of the oil shale member of the Bayingebi Formation in the study area were deposited in a semi-humid temperate climate and were inferred to be ice-rafting deposits, which may be related to a brief climatic cooling event or seasonal freezing during the Early Cretaceous in northern China. The typical East Asian paleontological fossils (Jehol Biota) and lacustrine hydrocarbon source rocks developed in the Early Cretaceous in the study area were affected by the paleoclimate warming in the early Aptian, which was closely related to the increase of global CO2 concentration in this period.

Sedimentary Provenance From the Evolving Forearc‐to‐Foreland Central Sakarya Basin, Western Anatolia Reveals Multi‐Phase Intercontinental Collision

AbstractCollision between the Pontides and Anatolide‐Tauride Block along the İzmir‐Ankara‐Erzincan suture in Anatolia has been variously estimated from the Late Cretaceous to Eocene. It remains unclear whether this age range results from a protracted, multi‐phase collision or differences between proxies of collision age and/or along strike diachroneity. Here, we leverage the Cretaceous‐Eocene evolution of the forearc‐to‐foreland Central Sakarya Basin system in western Anatolia to determine when and how collision progressed. New detrital zircon (DZ) and sandstone petrography results indicate that the volcanic arc was the main source of sediment to the forearc basin in the Late Cretaceous. The first appearance of Pontide basement‐aged DZs, in concert with exhumation of the accretionary prism and a decrease in regional convergence rates, indicates intercontinental collision initiated no later than 76 Ma. However, this first contractional phase does not produce advanced thick‐skinned deformation and basin partitioning until ca. 54 Ma. We propose three non‐exclusive and widely applicable mechanisms to reconcile the observed ∼20 Myr delay between initial intercontinental collision and thick‐skinned upper plate deformation: slab breakoff, relict basin closure north and south of the İAES, and underthrusting of progressively thicker passive margin lithosphere. These mechanisms highlight the links between upper plate deformation and plate coupling during continental collision.

Pyroclastic deposition in the Cretaceous Shahezi Formation (Well SK‐2) Songliao Basin, China: Implications for tectonics and volcanism

Well SK‐2 is located in the Songliao Basin. Core samples from this well indicate that the Early Cretaceous Shahezi Formation has a length of 2,359.01 m and is in direct contact with the basin basement of the Middle Triassic, missing the Huoshiling Formation. This paper is focused on the lowest sequence 1 (S1, at the bottom of the Shahezi Formation, interval of 5,450.72–5,695.00 m, a length of 244.28 m) of the Cretaceous basin fills. It was found that the volcanic components contributed important parts in the sequence of basin fills, and the start of the rifting resulted from the combination of regional extensional tectonics and volcanism. Based on the centimetre‐scale description of the continuous core samples, we propose a model to delineate the interaction between tectonics, volcanism, and pyroclastic deposition. The study shows the tectonic‐volcanism in the earliest rifting stages and its control on sedimentary filling. These results also have common sense for the initial rifting process of a continental half‐graben basin. Sequence 1 of the Shahezi Formation in well SK‐2 shows a typical volcanic‐ sedimentary sequence. During the lowstand stage, the weathering‐depositional system was controlled by extension; during the transgressive and highstand stages, the transitional weathering‐depositional system and the mixed volcanic and weathering depositional system were controlled by transtension.