This study reports the first documented occurrence of planktonic foraminiferal assemblages from core and grab samples collected from the United Arab Emirates (UAE) sector of the Arabian Gulf, specifically from offshore Abu Dhabi. Although planktonic foraminifera were found at only 4 out of 20 surveyed sites, representing less than 5 % of the total foraminiferal assemblage, their presence is notable. This finding demonstrates that planktonic foraminifera can be found far from their typical habitat near the oceanic inlet to the semi-enclosed Arabian Gulf - the Strait of Hormuz. The recovered material includes at least five species (three true planktonic foraminifera, one with a planktonic adult stage, and one incertae sedis): Neogallitellia vivans, Globigerinoides tenellus, and Turborotalita clarkei, as well as the benthic-planktonic species Tretomphalus bulloides and a planktonic taxon of uncertain origin described under the name Bachmayerella sp. The species N. vivans dominates in the studied samples, comprising over 90 % of the planktonic assemblage; however, their small size means that most specimens are not retained on a 125 & micro;m sieve. This work is part of a broader project to re-examine localities in the southeastern Arabian Gulf that were previously studied for benthic foraminifera, as well as to explore areas further offshore, which were previously uncharted for their foraminiferal content (particularly for the presence of planktonic foraminifera).

We report salinity and temperature of seawater of the southeastern Arabian Gulf from CTD surveys in August 2024 and March 2025. Uniformly high temperatures exceeding 34 degrees C in August 2024 down to 30 m water depth and extending up to 80 km offshore have been recorded. Seasonal salinity variations show the effect of cyclonal circulation on the southeastern Gulf and high rates of evaporation, which are also evident in delta 18O values of seawater that show a trend with salinity similar to the Red Sea. Sediment cores retrieved along a 115 km long onshore-offshore transect down to 52 m of water depth consist predominantly of medium to fine sand deposited above the effective wave base. Micro-mollusks and benthic foraminifers are the major benthic and nannoplankton and pteropods are the major planktonic sediment producers. According to their oxygen isotopic composition, bivalve shells form predominantly during the warm season, while calcareous nannoplankton appears to precipitate calcite during the cooler season. Carbonate production of the southeastern Gulf is compared with previously published geochemical evidence, and the depositional system of a carbonate ramp is critically discussed. Monitoring of seawater properties and more detailed studies of the major benthic and planktonic carbonate producers are required to understand diversity patterns in relation to the extreme environmental conditions and predicted climate change.

The northeastern Arabian Peninsula has an extreme arid climate. To establish past variations in precipitation intensity during the late Quaternary, the oxygen isotope ratios (delta 18O) of meteoric calcite cements of the late Quaternary aeolianites of the Ghayathi Formation in Abu Dhabi and Dubai have been analysed. The Ghayathi Formation is a carbonate-rich aeolianite, stabilised by calcite cement precipitated from rising groundwater during humid intervals. The calcite cements are well developed inside and outside a thin micrite rim of now hollow grains, formed by leaching of unstable carbonate grains. The delta 18O values of cement analysed in thin sections by secondary ion mass spectrometry vary from -9.1 parts per thousand (VPDB) in coastal to +12.7 parts per thousand (VPDB) inland areas. This exceptionally wide range of the otherwise petrographically uniform aeolianite is due to the contrasts in humidity and evaporation rate between the coastal and inland areas. The delta 18O values as low as -9.1 parts per thousand suggest intense precipitation in the late Quaternary, possibly due to the northward expansion of the intertropical convergence zone and intensified Indian summer monsoon. The exceptionally high values must be due to intense evaporation at low humidity in low-salinity, playa-type environments during intermittent arid intervals.

The effect of the early Aptian Oceanic Anoxic Event (OAE1a) on the southern Tethyan carbonate sedimentation on the eastern Arabian shelf is investigated. Chemostratigraphic platform-to-basin correlation of published and new outcrop and well core data allows for a lateral and temporal investigation of the changes in the depositional environment and reassessing the paleoenvironmental impact of OAE1a. Our results demonstrate that sedimentation rates varied spatially, influenced primarily by accommodation space and sediment redistribution rather than by effects of global carbon-cycle perturbations on carbonate production. Contrary to previous hypotheses, geochemical proxies do not support widespread anoxia on the Arabian shelf; instead, intermittent oxygen depletion was limited to specific basinal settings. Likewise, with the stratigraphic resolution of this study, no evidence of ocean acidification was detected, challenging models linking global carbonate platform demise to ocean acidification. Facies analysis reveals that transgressive-regressive cycles played a dominant role in shaping carbonate deposition. The transition from rudist-coral to orbitolinid-Bacinella assemblages reflects sea-level changes rather than nutrient stress. The spatial variations of delta 13Ccarb indicate hydrodynamic isolation within the platform interior, affecting local carbon budgets. Sediment preservation rates align with other Tethyan carbonate platforms, reinforcing the role of sea-level fluctuations in controlling carbonate production and accumulation.

Oceanic Anoxic Event 2 (OAE 2), spanning the Cenomanian/Turonian boundary (93.9 Ma), was an episode of major perturbation of the global carbon cycle. Its geochemical signature is a synchronous positive delta 13C excursion in both carbonates and organic matter that resulted from the net burial of large amounts of organic carbon in deep-sea and hemipelagic settings. Causes for OAE 2 are still the subject of investigations; however, several studies postulate that massive submarine volcanic activity emitted greenhouse gases and provided biolimiting metals in marine ecosystems, leading to the onset of the Cenomanian-Turonian thermal maximum and to the enhancement of ocean fertility. Ocean temperature, sea-surface stratification, nutrient availability, and carbonate ion saturation were subject to variations during OAE 2 that resulted in fluctuations in diversity abundance and calcification of species. We analyzed the record of the main biocalcifiers of pelagic-hemipelagic settings (planktonic foraminifera and calcareous nannofossils) and of low-latitude carbonate platforms (larger benthic foraminifera and rudist bivalves) by looking at well-dated sections. Carbon isotope stratigraphy allowed precise correlation from shallow to deep water and tied the biotic response to the record of geochemical proxies of paleoenvironmental changes. The main extinction event, severely affecting the shallow-water benthic biocalcifiers and to a minor extent the calcareous plankton, occurred within and after the Plenus Cold Event. Fluctuations in surface seawater temperature and extreme warming were probably the main cause of extinction, with contributions from decreased seawater carbonate saturation and disruption of ocean stratification. Overall, calcareous plankton fared much better, showing a greater resilience than carbonate-platform biocalcifiers to paleoenvironmental perturbations across OAE 2.

Larger benthic foraminifera such as orbitolinids are particularly important in Lower and mid-Cretaceous biostratigraphy of neritic deposits of the Arabian Plate. These data are supplemented by a few non-orbitolinid taxa. Among these, two new species are described herein as Voloshinoides simplex and Cribellopsis? kharaibensis from upper Barremian–lowermost Aptian inner platform limestones of the Kharaib Formation and the Hawar Member cropping out in Wadi Rahabah, United Arabian Emirates. V. simplex sp. nov. represents the oldest and most primitive species of the genus Voloshinoides Barnard and Banner, exhibiting a simple and poorly developed exoskeleton. C.? kharaibensis represents a rather small species exhibiting a primitive marginal zone that lacks intercalary beams. The assignment of the taxonomic status is provisional awaiting some structural clarifications. While C.? kharaibensis is restricted to the upper Barremian Kharaib Formation, V. simplex reaches into the lower part of the lowermost Aptian Hawar Member.

We present a high-resolution record of carbonate depositional facies, biostratigraphy, stable-isotope and elemental geochemistry of the Kharaib and Shu’aiba formations exposed in Ras Al Khaimah, northern UAE. This is the first comprehensive study of these deposits in the northeastern Arabian Peninsula, which have previously been studied extensively in Abu Dhabi, Oman, NE Saudi Arabia, and southwestern Iran, and represents the most detailed biostratigraphic and chemostratigraphic record currently available from a continuous outcrop section of the Arabian Plate. The Barremian–Aptian boundary was approximated based on orbitolinid biostratigraphy, while a subdivision of the Barremain was not possible. There is no biostratigraphic evidence that the Shu’aiba Formation in the section studied ranges into the upper Aptian. Previously well-established depositional sequences of the Barremian–lower Aptian of the Arabian Plate are discussed in the context of carbonate textures, siliciclastic influx, and biotic assemblages. There is a general trend of decreasing siliciclastic components during the Barremian and earliest Aptian, and peaks in siliciclastic influx indicate episodes of maximum accommodation. Palaeogeographic implications of our data for the distribution of intrashelf basins and their connection to Neotethys are discussed. The negative carbon-isotope excursion that globally marks the onset of OAE1a is not evident in our dataset, while the positive excursion at the end of OAE1a is present in the late early Aptian. A comparison of carbon-isotope records across the early Aptian of the Arabian Plate highlights issues of correlations that are predominantly based on chemostratography in diagenetically altered platform carbonates.

We have compiled stratigraphic ranges of genera of calcareous nannofossils, calcispheres, planktonic foramini-fers, larger benthic foraminifers, corals and rudists bivalves, and species of dasycladalean green algae. These taxa comprise the main planktonic and benthic carbonate producers of the Cretaceous, a period of exceptionally high sea level and palaeotemperatures that was characterized by unique assemblages of benthic carbonate producers and the significant rise in pelagic carbonate sedimentation. The autecology, physiological control on calcifica-tion, and carbonate-production potential of these groups is summarized. The observed diversity patterns are compared with proxy data of Cretaceous climate and seawater chemistry to elucidate the effect of environmental change on carbonate production and sedimentation.Two characteristic patterns are recognized. Diversity of calcareous nannofossils, calcispheres, planktonic foraminifers and corals trace the evolution of Cretaceous sea-level, while the diversity of dasycladalean algae, larger benthic foraminifers, corals and rudist bivalves show significant reductions at the level of oceanic anoxic events (OAEs). Benthic carbonate producers except for corals thus appear to have been more vulnerable to environmental change, and these general patterns appear to be unrelated to the autecology of the taxa inves-tigated. The expansion of suitable habitats during episodes of high sea level and high temperatures appears to have been a more important control of diversity in calcareous nannofossils, planktonic foraminifers, and corals than changes in seawater chemistry. Aragonitic or aragonite-dominated benthic carbonate producers are most affected during extinction events related to OAEs, and there is a general trend of decreasing aragonite dominance throughout the Cretaceous. This is compensated by the extensive formation of calcitic hemipelagic chalk since the Cenomanian. The trend of decreasing aragonite dominance is independent of the level of biological control on calcification in the different taxa affected. The demise of aragonitic or aragonite-dominated carbonate pro-ducers at OAE1a (early Aptian) and OAE2 (Cenomanian-Turonian boundary interval) may be related to short episodes of reduced seawater carbonate-saturation caused by short-lived injections of CO2 from large igneous provinces that initiated OAEs. For OAE1a, this scenario also explains the retreat of carbonate platforms to low latitudes in the early Aptian, as sea-surface water typically has a higher carbonate saturation in warm, lower than in cooler, higher latitude waters. The gradual decrease of aragonite throughout the Cretaceous matches model simulations of seawater carbonate-saturation. An increase in the relative number of azooxanthellate coral genera following OAE1a and OAE2 suggests a disruption of photosymbiosis in the course of these global events due to high temperatures. However, the relative numbers of azooxanthellate genera continued to increase during the Late Cretaceous, when global temperatures declined. Due to the short residence time of major nutrients in seawater, these may have affected carbonate-producing ecosystems regionally. The recent patterns of benthic carbonate production being highest in oligotrophic environments cannot confidently be extrapolated to the Cretaceous.Our database records ranges of genera at the substage level. Higher-resolution stratigraphical studies of neritic carbonate sequences are required to understand what aspect of environmental change in the sequence of events that unfolded in the context of OAEs caused the demise of benthic carbonate producers.

We report the first high-resolution sedimentological and geochemical record of the negative carbon-isotope excursion (CIE) at the onset of the early Aptian oceanic anoxic event (OAE) 1a from a carbonate-ramp depositional environment, analysed from a well core from c. 2500 m depth, 100 km offshore Abu Dhabi, United Arab Emirates. Time-series analysis of stable oxygen isotope values and concentrations of Si, Al, and Ti resulted in durations of the C3 and C4 segments of the CIE that support relative completeness of the C3 segment and high sediment preservation rates of c. 13 cm/kyr of the studied sedimentary sequence. Stable oxygen-isotope ratios of bulk carbonates are interpreted to indicate two episodes of cooling, separated by rapid warming during the peak of the negative CIE. The contributions of diagenesis and seawater pH on the bulk oxygen-isotope record will have affected the palaeoclimatic signal and are critically discussed. A major shift in oxygen isotope values at the peak of the negative CIE in the C3 segment coincides with relatively carbonate-poor, marly deposits, time-equivalent with other, global evidence for a reduction of carbonate saturation of sea-surface water. According to our chemo- and cyclostratigraphic calibration, this episode of low carbonate saturation of seawater reflects a pulse of major volcanic CO2 release from the Ontong-Java large igneous province that was sufficiently short to have escaped internal buffering by the dynamics of the ocean lysocline.

Aeolianites with a mixed clastic and carbonate detrital mineralogy are typical deposits of tropical coastal desert environments. These deposits are genetically related to transgressive–regressive cycles, with the shallow‐marine carbonate detrital component being deflated from the exposed seafloor during episodes of glacial sea‐level lowstands, transported and later accumulated onto more continental areas. A detailed investigation of the granulometric and petrographic properties of the Late Pleistocene to Holocene Ghayathi Formation in the United Arab Emirates provides a comprehensive numerical dataset that reveals the complex spatio‐temporal depositional and diagenetic evolution of a mixed siliciclastic–carbonate continental aeolianite. Fifty‐one thin sections and forty‐four rock samples of three sedimentary units (Madinat‐Zayed, Ghayathi and Fuwayrit formations) from the United Arab Emirates were analyzed for their grain‐size distribution, mineralogy and the bulk stable‐carbon and oxygen isotopic composition. Sorting, skewness and kurtosis of the grain‐size distributions provide evidence for a divergent aerodynamic behaviour between the carbonate and siliciclastic particles. The different grain‐size distributions between the inland and coastal sections of the Ghayathi Formation indicate that continental mixed clastic−carbonate aeolianites are affected by density‐driven selective transport and consequent traction sorting due to the nature of carbonate detritus. The transport decoupling of the different detrital components resulted in a ‘continental sorting’ effect, with the inland sections yielding layers characterized by a better sorted detritus than the coastal areas. All detritus originally composed of aragonite has been removed by dissolution during early meteoric diagenesis, with its shapes frequently preserved by micritic envelopes. The bulk stable‐isotope composition of the carbonate fraction reflects a decreasing degree of meteoric cementation from coastal to inland areas. The high complexity of the lateral and vertical distribution of the sedimentary, diagenetic and isotopic properties of continental mixed aeolianites, such as the Ghayathi Formation, highlights the problem of recognizing such deposits in the pre‐Quaternary sedimentary record.

The formation of carbonate build‐ups associated with seafloor methane vents – where microbially mediated sulphate‐dependent anaerobic oxidation of methane produces alkalinity – is well documented in modern marine environments and in the geologic record. However, the triggering event(s) behind the processes leading to hydrocarbon disequilibrium, seeping and consequent deposition of seep‐carbonates remain poorly constrained. This contribution characterises the salinity, geochemistry and temperature framework of a suit of fluid inclusions from hydrocarbon‐derived seep‐carbonate veins, collected from the Marmorito Formation in the Monferrato Hills, NW Italy. The datasets yield evidence of three different precipitation events, which comprise porous structures composed of well bladed calcites and aggregated spherules of aragonite. Fluid inclusions analysis shows the presence of a heterogeneous entrapment of immiscible fluids proving the paleo‐dissolution of a suite of complex hydrocarbons, which have a wide range of closing temperature starting at ca. 60°C. These physical and chemical conditions are considered to indicate seep‐carbonate deposition driven by disequilibrium of hydrocarbon‐bearing compounds at temperatures much warmer than the background ambient bottom waters (ca. 1 to 5°C) due to the influence of the Late Oligocene to Early Miocene tectonic compression at the junction of the southern Alps and Apennines.

In the late Cenomanian, palaeoenvironments on the Arabian Shelf were characterised by shallow-marine carbonate build-ups and extensive intra-platform basins. The hemipelagic carbonate succession of the Shilaif Basin (Abu Dhabi, United Arab Emirates) offers a continuous sedimentological record from a palaeoequatorial latitude. Carbon-isotope records from these shelf carbonates that span across the Cenomanian-Turonian boundary interval are characterised by low carbonate delta C-13 values that predate the positive carbon-isotope excursion related to Oceanic Anoxic Event 2. It is to date uncertain whether this late Cenomanian negative delta C-13 shift is diagenetically linked to the preservation of organic matter or if it indicates a global signal related to palaeoenvironmental change at the onset of OAE 2. To better understand the cause of this anomaly and to improve our understanding of global palaeoclimatic changes at the onset of OAE 2, we present a multiproxy study on two continuous successions from across the Shilaif Basin. The work includes high-resolution bulk carbonate carbon-isotope records, bio- and cyclostratigraphy, characterisation of organic matter, and elemental concentrations. The integration of available data provides precise chronostratigraphic control between sections and allows for reconstructions of detrital sediment influx, relative sea-level change, differential accumulation rates, and changes in redox conditions. Findings confirm a pronounced light carbonisotope anomaly preceding the characteristic heavy excursion relating to OAE 2. Orbital cyclicities obtained from core-scan greyscale images are in agreement with nannofossil biostratigraphy and suggest a duration of approximately 528-678 kyr for the negative and 194-250 kyr for positive delta C-13 CIEs in the late Cenomanian. The intra-basinal correlation presented in this study further supports evidence for a palaeoceanographic origin of the negative CIE, which appears to be unrelated to diagenetic processes. Integration of results suggests peak sea-levels in the late Cenomanian and a significant increase in surface-water productivity preceding the positive carbon-isotope excursion diagnostic for OAE 2. Organic matter preservation is asynchronous and was probably controlled by restriction, initiating from the South of the Shilaif Basin approximately 550-650 kyr before the positive CIE. Maximum organic matter preservation in the North coincides with the latest Cenomanian OAE 2 carbon-isotope excursion, suggesting open water exchange with the Neotethys. During OAE 2, the sedimentary record and present proxies suggest high-frequent changes in sea-level and sediment oxygenation possibly related to the 'Plenus' event.

The background to the preparation of the rudist sections for the ongoing complete revision of the Bivalvia volumes of the 'Treatise on Invertebrate Palaeontology' is described. The progress on publication is reported. The plans for further work are outlined. Three introductory chapters on rudists have already been published in 'Treatise Online' (University of Kansas, Paleontological Institute). Future work will be devoted to the preparation of the taxonomic descriptions of genera and a synoptic example of which is provided for the genus Pachytraga.

In the Triassic-Jurassic (T-J) interval, only a few continuous carbonate sections have been reported, and detailed studies about ooids and their significance are scarce. This study focuses on abundant ooids in potentially continuous T-J carbonate sections representing equatorial, shallow marine environments. Mineralogical changes of ooids are proposed as a marker for transitional marine chemistry including carbonate saturation after ocean acidification and provide information about crisis and recovery scenarios for the initial CIE (carbon isotope excursion) and subsequent positive CIE. In the Ghalilah Formation, United Arab Emirates (UAE), the Sakhra Member is deposited immediately above the T-J boundary. Based on field work and thin section observation, the Sakhra Member can be divided into three coarsening-upward cycles (in ascending order, named C1–C3), each of which consists of peloidal mudstone/wackestone in the lower part and oolitic packstone/grainstone in the upper part. Petrological observation (thin section, SEM), stable isotope (inorganic carbon and oxygen) and elemental analysis suggest temporal change of original mineralogy from C1 to C3 ooids: from high-Mg calcite in C1 ooids to aragonite in C2 and C3 ooids. The mineralogical change of ooids is possibly related to variations in seawater carbonate saturation. The lower carbonate saturation indicated by C1 ooids reflects a transitional period before recovery from ocean acidification due to massive and rapid release of acidic gases (CO2 and SO2) by CAMP eruptions. Subsequently, from C1 to C3 ooids, seawater gradually experienced increasing carbonate saturation and increasing microbial carbonate precipitation. Increased microbial activities combined with elevated terrestrial influx may have significantly reduced the atmospheric CO2 concentration and restored carbonate saturation, which laid the foundation for full biotic recovery.

This special issue of the Canadian Journal of Earth Science, which is entitled “Advances in low–temperature geochemistry, diagenesis, seawater and climate evolution through the Earth’s history: A special tribute to J. Veizer” is in honor of Professor Dr. Jan Veizer who is the Distinguished University Professor (emeritus) of Earth Sciences at the University of Ottawa and former Chair of Sedimentary and Isotope Geology, Institute for Geology, Mineralogy und Geophysics, of Ruhr University (Bochum, Germany).

The sedimentary record of the Arabian Shelf offers a unique opportunity to study the Cretaceous (Albian-Turonian) greenhouse climate from a palaeoequatorial perspective. In particular, hemipelagic to pelagic carbonate successions from the extensive Shilaif intra-shelf basin have the potential to produce an excellent record of carbon cycle perturbations during this interval. This study presents a 269m thick chemostratigraphic (carbonate C-13 and O-18) record from the Middle Albian to Early Turonian of central Abu Dhabi (United Arab Emirates), representing over 14Myr of uninterrupted carbonate sedimentation. The Mauddud to Shilaif formations represent outer ramp to basinal intra-shelf carbonates with variations from laminated organic-rich to clean bioturbated intervals. Isotopic evidence of the latest Albian Anoxic Event (Oceanic Anoxic Event 1d), Middle Cenomanian Event I and the Cenomanian-Turonian Anoxic Event (Oceanic Anoxic Event 2) are confirmed and biostratigraphically calibrated by means of calcareous nannofossils. The carbon isotope record allows correlation with other regional records and well-calibrated records across the Tethyan Ocean and represents a significant improvement of the chronostratigraphic framework of the United Arab Emirates (Shilaif) and Oman (Natih) intra-shelf basins. The study further confirms that low carbon isotope values corresponding to the two source rock intervals in the Shilaif Formation clearly precede the isotopic expressions of Oceanic Anoxic Event 1d and Oceanic Anoxic Event 2.

The carbon and oxygen isotopic composition was analysed several shells of Vaccinites cornuvaccinum (Bronn) from late Santonian-Campanian transgressive deposits of Beotia (central Greece) … in order to continue, download the full paper in PDF.

Book review: Rong Jiayu (editor-in-chief), Jin Yugan, Shen Shuzhong and Zhan Renbin (eds.), 2017. Science Press, Beijing, P.R. China, xviii + 1096 p. (two vols.)