Campanian-Maastrichtian Boundary Research Articles

Dinoflagellate cyst biostratigraphy of the upper Campanian–lower Maastrichtian interval in the Oslen-Krivodol section, Northwest Bulgaria: preliminary results

A dinoflagellate cyst biostratigraphy for the upper Campanian–lower Maastrichtian interval in the newly described Oslen-Krivodol section, northwest Bulgaria, is proposed. The dinocyst scheme comprises the zones of Areoligera coronata and Cerodinium diebelii, in ascending order, and illustrates the sharp transition between the Campanian and Maastrichtian dinocyst assemblages. The presented results confirm the high potential of dinoflagellate cysts for biostratigraphic correlations in the Campanian–Maastrichtian boundary interval.

Late Campanian-Maastrichtian in Pondicherry Area (Cauvery Basin) Southern India: Bioevents and Palaeoenvironmental Inferences from Planktonic Foraminifera

Abstract The late Campanian/Maastrichtian succession exposed in the Pondicherry area provides one of the best exposed marine sections in the Cauvery basin and is examined for its foraminiferal contents. The biostratigraphic distribution of 72 species of planktonic foraminifera has been used to identify eleven planktonic zones and subzones and correlated to the global bioevents. The present biostratigraphic analysis has revealed four bioevents in the late Campanian-Maastrichtian sediments of the Pondicherry area. The first one was associated with the Radotruncana calcarata (CF10), which correlated to the late Campanian event (LCE); the second bioevent was associated with the Rugoglobigerina rotundata (CF7a) and the Rugoglobigerina scotti CF7b, which correlated to the (Campanian-Maastrichtian boundary event (CMBE); the third bioevent is associated with Globotruncana linneiana and Contusotruncana contusa, which correlated to middle Maastrichtian event (MME). The fourth bioevent associated with the Racemiguembelina fructicosa, which is correlated with the late Maastrichtian event (LME) associated with the Cretaceous/Paleogene boundary in the studied area. Three principal climate and faunal associations were identified in the present study in Cauvery basin; (1) worldwide cooling with minimal variation in the late Campanian-earliest Maastrichtian observed through extraordinary diversification for the Cretaceous mostly accomplished in the early Maastrichtian (Event-1, C31r), (2) warming and stable high diversity (Event-2, upper C31r to lower C30n), (3) return to global cooling and high-stress environments (Event-3, C30n),

Charophytes from the Upper Cretaceous Castilian marine ramp and continental basins (central northern Spain): Fossil assemblages and depositional environments

The Upper Cretaceous sedimentary series of the Castilian marine ramp and continental basins (central northern Spain) have yielded numerous charophyte bearing sites which extend within the middle Cenomanian to upper Maastrichtian succession. The purpose of the paper is both to list the recognized charophyte taxa and to describe the sedimentary sequences in which the charophytes were found in order to reconstruct their depositional environments. The charophyte flora comprises 2 families, 15 genera and 28 species, including 3 new taxa: Lamprothamnium elongatum, Lamprothamnium ovoideum, Pseudoharrisichara sedanoensis. Among 27 charophyte bearing sites, 22 were formed during episodes of emersion and terrestrial conditions that interrupted the marine succession of the Castilian ramp, and 5 are from restricted Castilian continental basins that developed from the Campanian–Maastrichtian boundary onwards. The Campanian–Maastrichtian fossiliferous sites allow elucidating floristic and biostratigraphic correlations with the charophyte floras from Catalonia and from the Serrania de Cuenca.

Global carbon isotopic events in a Campanian–Maastrichtian deltaic succession (Tremp-Graus Basin, Spain) and multiproxy stratigraphy for high sedimentation rate environments

The Campanian to Maastrichtian sedimentary succession of the Tremp-Graus Basin (NE Spain) is characterized by the offshore-to-prodeltaic upper Vallcarga Fm giving way to prograding deltaic units (the Aren Fm), which are overlain by transitional facies (the Grey Unit) that correspond to the basal part of the Tremp Group. This work aims to improve the stratigraphical scheme of these deposits using a new dataset of δ13Ccarb and δ13Corg, δ18O and TOC variations through time, supported by a new biostratigraphical analysis and compiling previous biostratigraphical and paleomagnetic data. The comparison of isotopic signals from marine reference sections where δ13Ccarb is well calibrated in the Tethys realm allows recognition of global isotopic events that can be used as correlative marker events. Significant high-frequency δ13C variations defined in the δ13Ccarb are identified in the studied succession despite the different sedimentary setting and some can be related to global geochemical events such as the Late Campanian Event (LCE) and the Campanian–Maastrichtian Boundary Event (CMBE), in good agreement with the magnetic chrons at the base of the Tremp Group, and with some new biostratigraphic constraints. From multiple geochemical and petrographic analysis of the organic matter we suggest that the geochemical signal corresponds to global changes, but at higher resolution, sedimentary dynamics are also reflected in the geochemical signals, particularly inputs of surface water in the deltaic signal.

Depositional environment and sequence stratigraphy of the Upper Cretaceous Aruma Formation, NE Riyadh, Saudi Arabia

The Campanian to Maastrichtian Aruma Formation represents a distinctive depositional system of the carbonate-dominated ramp along the Arabian plate. Sedimentologic characteristics and stratigraphic relations are integrated with carbon and oxygen stable-isotope data to interpret the depositional environments in a sequence stratigraphic framework. One siliciclastic facies association (FA1) and eight carbonate microfacies (MF 1–8) belonging to four facies belts (FB1–4) were identified. Facies characteristics support accumulations on a carbonate ramp environment that extends from offshore/outer ramp to middle and inner ramp settings. Stable-isotope data are correlated to the oscillating global sea-level curve and global excursions’ events in order to refine the sequence stratigraphy of the Aruma Formation. Carbon-isotope chemostratigraphy shows remarkable long-time excursions, which are correlated to the two global negative excursions (Late Campanian event “LCE” and Campanian–Maastrichtian boundary event “CMBE”) as well as the positive δ13 C excursion of Middle Maastrichtian event “MME” and the uppermost negative δ13 C excursion toward the K–Pg boundary. The negative shift in the δ13 C values associated with relatively positive values in the δ18 O herald three marked sea-level falls, which can be coincided with global sequence boundaries. The merged surfaces TS1/SB1 and TS2/SB2 can be correlated to the Campanian events KCa3 (80 Ma) and KCa6 (75.4 Ma), respectively. The coplanar surface TS3/SB3 matches well with the Maastrichtian event KMa3 (69.4 Ma). The positive values of δ13 C and/or negative values of δ18 O coincide with periods of maximum transgressions. The minor pulses are mostly attributed to cyclic fourth-order sequences. The established sequence stratigraphic architecture and depositional model of the outcrop data herein will be useful in regional correlations with analogous subsurface successions along the Arabian plate and enhancement of potential petroleum explorations.

Quantitative analysis of calcareous nannofossil assemblages across the Campanian/Maastrichtian boundary interval at Kladorub (NW Bulgaria): preliminary results

An investigation of the variations in calcareous nannofossil abundances across the Campanian/Maastrichtian boundary interval at Kladorub (NW Bulgaria) has been carried out. The section has an established detailed biostratigraphic framework, based on calcareous nannofossils, and also contains the Campanian–Maastrichtian Boundary Event. The analysis shows that the nannofloras are dominated by Prediscosphaera cretacea, followed by Watznaueria barnesiae, Micula staurophora, Arkhangelskiella spp. and Cribrosphaerella ehrenbergii.

Turonian-Maastrichtian biostratigraphy and isotope stratigraphy of the Kopet-Dagh Basin deposits, northeastern Neo-Tethys, Iran

Planktonic foraminiferal biostratigraphy and isotope stratigraphy analyses of Turonian-Maastrichtian deposits have been carried out in the western part of the Kopet-Dagh Basin. The identification of the planktonic foraminiferal assemblages has led to the recognition of twelve Upper Cretaceous zones (Helvetoglobotruncana helvetica Zone to the Contusotruncana contusa-Abathomphalus mayaroensis zone) from the Tethyan realm. The obtained stable carbon isotope profile correlates with other reference curves, revealing many Late Cretaceous events including the Hitchwood, Navigation, Light Point, East Cliff, White Fall, Late Campanian Event (LCE), Campanian-Maastrichtian Boundary Event (CMBE), Middle Maastrichtian Event (MME) and KPg Events (KPgE). The Turonian-Maastrichtian deposits of the studied area represent severe changes in sedimentation rate and several hiatuses and condensed intervals, which mostly coincide with lithological boundaries. The data indicate a general shallowing -upwards in association with the Late Cretaceous tectonics of the Kopet-Dagh Basin. The reconstruction of the age model allows a discussion of the results in terms of changes in palaeoenvironmental conditions (eutrophic vs. oligotrophic).

Biostratigraphy and Systematic Palaeontology of Late Cretaceous Heterohelicidae Foraminifera from Kurdistan Region North-eastern Iraq

The biostratigraphical importance and systematic palaeontology of Early Turonian to Early Maastrichtian Heterohelicidae Planktic foraminifera from Kurdistan region, NE Iraq are described. Some 24 species from 11 genera are recorded. Species abundance and diversity increase from the Early Turonian to Early Maastrichtian, perhaps signifying cooler sea temperatures in the Arabian sector of the Tethys Ocean during the Early Maastrichtian. Despite the long biostratigraphical ranges of some species, the importance of the biserial and multiserial Planktic foraminifers in Late Cretaceous biostratigraphy is emphasized. From a biostratigraphic perspective, heterohelicids are important for the definition of the Campanian-Maastrichtian boundary in Kurdistan region, with Planoglobulina species being especially important in this respect, as they are in Iran, Turkey and North Africa.

Response of the lacustrine flora in East Asia to global climate changes across the K/Pg boundary

The global climate during the latest Cretaceous became variable, with several global warming and cooling trends in a context of a greenhouse Earth. The responses of marine ecosystems to these climate events are relatively well known worldwide; however, lacustrine responses are poorly known due to the less frequent and discontinuous terrestrial fossil records. The relative changes in charophyte diversity in continuous lacustrine sedimentary sequences from two basins in East Asia, i.e., Songliao and Jiaolai, are considered here for the first time to establish their correlation with global climate changes during the Late Cretaceous and K/Pg boundary, compared with the well-studied south European Ibero-Armorican Island. Lacustrine deposits correlated with the Campanian–Maastrichtian Boundary Event (CMBE), related to a long cooling period provided a relatively low diversity in East Asia. In contrast, we detected a diverse charophyte flora in lacustrine deposits correlated with the Mid-Maastrichtian Event (MME) in East Asia in a global warming trend. A higher charophyte diversity was further found in the end-Cretaceous global warming event due to speciation under the background of latest Maastrichtian warming event (LMWE). During the LMWE, Characeae species such as Microchara cristata reduced its size significantly due to environmental stress probably related to the Deccan volcanism. On the other hand, a general tendency of increasing the gyrogonite size in new Characeae taxa has been detected in populations extracted from lower Danian deposits, probably related to stable palaeoenvironmental conditions in a global cooling context. This study represents the first attempt to correlate the response of the charophyte flora to global climate changes in permanent lacustrine systems during the three main Late Cretaceous–early Danian climatic turnovers. • Changes of charophyte flora is a sensitive proxy to record climate changes. • Characeae species reduced their size due to environmental stress. • Increasing size in new Danian Characeae taxa is related to global cooling.

New Sedimentological, Magnetostratigraphic, and Biostratigraphic Data on the Campanian–Maastrichtian of Beshkosh Mountain, Southwest Crimea

An integrated study of the Campanian–Maastrichtian deposits of Beshkosh Mountain (Southwest Crimea) was carried out. The finds of cephalopods and dinocysts were studied, and ichnofacies and sedimentological analyses were performed. Isotopic, paleomagnetic, and petromagnetic data were obtained for the first time. New macro- and micropaleontological data made it possible to refine the stratigraphic subdivision of the section and confirm its late Campanian–Maastrichtian age. Paleomagnetic studies have revealed no analogs of magnetic Chron C31r. The only recognizable reversed-polarity magnetozone against the background of the prevailing normal polarity was identified as an analog of Chron C30r. The study of dinocysts revealed a sharp change in their assemblages in the lower part of the section, above which ammonite Pachydiscus (P.) neubergicus neubergicus (Hauer), a marker species of the Campanian–Maastrichtian boundary, was found. An integrated biostratigraphic, magnetostratigraphic, and sedimentological analysis made it possible to recognize the previously unknown unconformity in the Campanian–Maastrichtian boundary interval. Data of stable isotopes are consistent with the proposed hiatus.

Late Cretaceous stratigraphy in the Mudurnu–Göynük Basin (Turkey) and inferences on sea-level change in the Late Campanian to Early Maastrichtian

Abstract Upper Cretaceous strata at Göynük, northwestern Anatolia, Turkey, provide a geological record of the Campanian–Maastrichtian from the Sakarya Terrane along the active Neotethys margin. Shales and shaly marls with siliciclastic and volcaniclastic intercalations indicate a pelagic palaeoenvironment rich in planktonic and benthonic foraminifera and calcareous nannofossil assemblages. A composite record from the Campanian to the Maastrichtian records nannofossil standard zones UC15c (CC21) to UC20a (CC26) as well as the Globotrunanella havanensis planktonic foraminifera Zone to the Racemiguembelina fructicosa planktonic foraminifera Zone. The complete ‘mid’-Campanian to early Maastrichtian composite section can be correlated to other western Tethyan sections. The Campanian–Maastrichtian boundary is positioned between the first occurrence of the planktonic foraminifera Gansserina gansseri and the last occurrence of the nannofossil Uniplanarius trifidus . Clastic input and higher sedimentation rates constrain regional sea-level lowstands around the late Campanian calcarata Zone and the Campanian–Maastrichtian boundary, corresponding to the Campanian–Maastrichtian boundary event.

Palynological record of the Cretaceous ZKD14 core (Songliao Basin, Northeast China) and its paleoclimatic significance

AbstractTo better understand the vegetation and possible paleoclimate change, we recovered a palynological record obtained from the ZKD14 core covering from the Sifangtai and Mingshui Formations in the northern Songliao Basin, northeastern China. Based on the abundance and variations in determined palynomorphs, two palynological assemblages can be distinguished, including Schizaeoisporites–bisaccate–Tricolporopollenites and Taxodiaceaepollenites–bisaccate–Tricolporopollenites. These palynological assemblages are assigned to the late Campanian–Maastrichtian stage based on the geological range of some important elements and the correlation with relevant assemblages of other areas. In this paper, we applied a sporopollen–climate transforming methodology, which uses the percentage of xerophytic and thermophilic taxa to indicate stratigraphic trends of humidity and temperature, respectively. Then two vegetation and paleoclimate phases were reconstructed based on the ecological habits of the parent plant, as well as the abundance variation in xerophytic and thermophilic taxa: (i) The vegetation type was interpreted to reflect a mixed conifer forest with varying pteridophytes landscape, presenting a hot and arid subtropic climate during the Sifangtai to lower part of member 2 of the Mingshui Formations. (ii) The vegetation type was characterized by a conifer‐dominant landscape. Accordingly, the climate turned more humid and colder during the upper part of member 2 of the Mingshui Formation. The global cooling event (Campanian–Maastrichtian Boundary Event: CMBE) which occurred between 72.0–70.0 Ma appears to have an important influence on the climatic condition of Songliao Basin.

A Boreal reference section revisited (Kronsmoor, northern Germany): high-resolution stratigraphic calibration of the Campanian–Maastrichtian boundary interval (Upper Cretaceous)

A Boreal reference section revisited (Kronsmoor, northern Germany): high-resolution stratigraphic calibration of the Campanian–Maastrichtian boundary interval (Upper Cretaceous)

Tectonically controlled initiation of contemporaneous deep‐water channel systems along a Late Cretaceous continental margin, western British Columbia, Canada

AbstractSubmarine channel‐systems are globally prevalent on continental margins and their deposits record the transfer of significant volumes of sediment from continental catchments to deep‐water environments. These deposits contain signals of past events that can provide critical insight into the geological history of an area, including the long‐term (>1 Ma) controls on sedimentation. Well‐exposed outcrops of the Late Cretaceous Nanaimo Group, British Columbia, Canada, provide an opportunity to investigate long‐term sediment‐routing in a tectonically active setting. This study combines detrital zircon geochronology with stratigraphic analysis to establish a robust, basin‐wide palaeogeographic framework that constrains the timing and distribution of coarse‐grained sediment transport and deposition in the Nanaimo forearc basin. Three south‐west trending submarine conduits are documented along a 135 km long strike‐oriented transect, parallel to the north‐west/south‐east trending basin. Composite conduit deposits are 350 to 700 m thick, 4 to 16 km wide, and record substantial delivery of coarse‐grained detritus (up to boulder‐sized clasts) within submarine channel‐levée systems. Maximum depositional ages derived from detrital zircon datasets constrain contemporaneous sediment transfer and deposition at each conduit location, which spanned between 73·5 ± 1·3 Ma to 69·1 ± 1·1 Ma around the Campanian–Maastrichtian boundary. Submarine conduits are spaced at 40 km and 70 km, and were likely connected to fluvial drainage systems sourced in uplifted catchments. Widespread, coarse‐grained deposits suggest that surface uplift associated with concurrent regional events (such as deformation and/or magma emplacement) along the North American margin may have promoted sediment delivery to the deep‐water basin. Comparisons to modern and ancient analogues support palaeogeographic interpretations, as well as the interpretation that pervasive coarse‐grained deep‐water sediment delivery was linked to tectonic activity. The integrated stratigraphic–geochronological approach used provides unique insight into the influence of regional tectonics on continental margin physiography and the nature of deep‐water sediment dispersal.

From phytoplankton to oil shale reservoirs: A 19-million-year record of the Late Cretaceous Tethyan upwelling regime in the Levant Basin

Abstract The complexity of sedimentary organic-matter formation, its source to burial, and influence on bottom-water communities are addressed in this study of the 19 million years-long Upper Cretaceous Tethyan upwelling regime in the Levant. A multi-proxy approach is amalgamated into a model through which the paleoceanographic complexity of an intense and long-lasting upwelling system is better understood. A shift in primary producer assemblages and reorganization of the bottom water bacterial consortium followed the Campanian-Maastrichtian boundary, enforcing conspicuous sedimentological and faunal changes. The siliceous and phosphatic-bearing sediments of the Campanian gave way to Maastrichtian uniform and regionally distributed organic-rich carbonates, accompanied by an increase in sedimentation rates from ∼1 to >6 cm/kyr. This has facilitated both the increase in organic-matter production and its excellent preservation, and through diagenetic pathways affected its elemental composition. These paleoceanographic modifications have also affected foraminiferal assemblages, from massive blooms of triserial (buliminid) benthic foraminifera during the Campanian which have sequestered diatom chloroplasts, to diverse trochospiral forms during the Maastrichtian using nitrate instead of oxygen for their respiratory pathways. We propose that shifts in the type of primary producers promote a change in the amount and type of preserved organic matter, in bottom water communities, on the lithological composition of the rock-mass, and ultimately on the hydrocarbon generation potential of the studied source rock. The continued rise of southern Tethyan sea level and global highstands during the Upper Maastrichtian, culminating into Arabian Plate-wide maximum flooding surfaces, cause the migration of upwelling activity away from the study area, terminating the high productivity sequence in the Levant.

The δ13C record of Maastrichtian-Paleocene oil shales from Jordan – Stratigraphic and environmental implications for an epicontinental setting

Organic matter (OM) rich marls were deposited in several intrashelf basins in Jordan (e.g. Yarmouk Basin, Lajjun Basin, Azraq-Hamza Basin, Jafr Basin, Eshidiyya Basin) on the southeastern Tethyan margin during the Maastrichtian to middle Eocene. Factors like surface water productivity fueled by upwelling and sea level changes affected their deposition. Potential effects of climatic changes have not been determined yet.We present the first stable carbon and oxygen isotope records of Maastrichtian-Danian oil shales from the Azraq-Hamza and Jafr Basins in south- and central-east Jordan. The δ13Ccarb curves were time-calibrated based on calcareous nannofossil biostratigraphy. Eight notable excursions were identified in the Jordanian Maastrichtian sections. These were correlated with the documented Maastrichtian δ13Ccarb events in the (sub) tropical sections of Italy and the western Pacific: the Campanian-Maastrichtian boundary Events 4 and 5 (CMBE-4, CMBE-5), the Middle Maastrichtian Events 1 to 3 (MME-1 to MME-3) and the Cretaceous-Paleogene boundary Events 1 to 3 (KPgE-1 to KPgE-3). Signs of the Latest Danian Event (LDE) were recognized as well. Total organic carbon (TOC) data exhibit a complex relationship with the δ13Ccarb proxy record. The δ13Ccarb signals are repeatedly dampened due to the OM oxidation and subsequent 12C release. The effect of short term climate changes is observed, but is not always straight forward. Long term climate changes had indirect effects on bottom water oxygenation and OM preservation via sea level changes. The δ18Ocarb data from both sections reveal minor temperature changes in the Maastrichtian. Slight warming is observed in the MME interval. A potential increase of the paleotemperature is reported from the Azraq-Hamza section occurring in the latest Maastrichtian to earliest Danian.

Did Late Cretaceous cooling trigger the Campanian–Maastrichtian Boundary Event?

Did Late Cretaceous cooling trigger the Campanian–Maastrichtian Boundary Event?

Did Late Cretaceous cooling trigger the Campanian–Maastrichtian Boundary Event?

The Campanian–Maastrichtian (83–66 Ma) was a period of global climate cooling, featuring significant negative carbon-isotope (δ13C) anomalies, such as the Late Campanian Event (LCE) and the Campanian–Maastrichtian Boundary Event (CMBE). A variety of factors, including changes in temperature, oceanic circulation and gateway opening, have been invoked to explain these δ13C perturbations, but no precise mechanism has yet been well constrained. In order to improve our understanding of these events, we measured stable carbon and oxygen isotopes of hemipelagic sediments from the Shuqualak-Evans cored borehole (Mississippi, USA) and compared the data with previously published sea-surface temperature (SST) estimates from the same core. We found that the CMBE can be recognised, unambiguously, in the ShuqualakEvans core, and that it is associated with an interval of cooler SSTs suggesting a possible mechanistic link between palaeotemperature change and this event. Determining the precise position of the LCE in the Shuqualak-Evans core is more problematic, but it may also be associated with cooler SSTs. Our combined records of carbon cycling and SSTs compare well with other studies and provide evidence that cooling during the CMBE (and possibly LCE) was global in nature and affected surface waters, in addition to the deep-ocean. We suggest that short-term cooling drove intensification of high-latitude deep-water formation, which in turn led to changes in the ratio of carbonate to organic carbon burial that led to a negative δ13C excursion. Critically, the absence of warming during these intervals implies that the Late Cretaceous events must not have been associated with an appreciable increase in atmospheric pCO2, and was likely associated with decreased pCO2.

Tracking Late Cretaceous environmental change: Geochemical environment of the upper Campanian to lower Maastrichtian chalks at Kronsmoor, northern Germany

This high-resolution study (210 samples/44 m) of the uppermost Campanian–lower Maastrichtian chalk at Kronsmoor (northern Germany) intends to define the inorganic depositional setting of Late Cretaceous chalk deposition as well as to reconstruct contemporaneous sea-level fluctuations and palaeoenvironmental changes. A latest Campanian event associated with significantly decreased carbonate contents and palaeotemperatures is reflected in most geochemical palaeoproductivity proxies and indicates reduced marine fertility across the Campanian–Maastrichtian boundary. Sr/Ca and δ13C remain low afterwards while other productivity proxies show a significant rebound, indicating recovery and a potential qualitative change in marine productivity during the early Maastrichtian. Redox-sensitive proxies indicate overall well oxygenated conditions. The %terrigenous proxy tracks an argillaceous chalk depositional event related to an inferred glacio-eustatic latest Campanian sea-level fall followed by a low sea-level stand until the earliest Maastrichtian. It decreases and stays low up-section, reflecting an early Maastrichtian sea-level rise and highstand, parallelled by increasing and consistently high carbonate contents. However, the concomitant conspicuous variability and increase in other terrigenous input proxies indicate more strongly fluctuating and higher aeolian supply. Time-series analysis of selected geochemical proxies demonstrates the presence of the obliquity (∼40 kyr) the long-eccentricity (∼400 kyr) cycles of the Milankovitch Band. The covariance of productivity proxies and indicators of aeolian input suggests that obliquity forcing of dust input exerted control on (surface) water productivity, CaCO3 flux and the end-Cretaceous carbon cycle.

An integrated study of upper Campanian-lower Maastrichtian carbon isotopes and calcareous plankton biostratigraphy of the Kurdistan Region, northeastern Iraq

New carbon (δ13C) isotope records calibrated by planktonic bioevents provide general support for a late Campanian age assignment of the Shiranish Formation (Fm.) and its boundaries in the Dokan section (NE Iraq). The Shiranish Fm. is characterised at the base by a mid-Campanian unconformity as can be interpreted by absences of nannofossil zones CC20-21. The Shiranish Fm. then spans nannofossil biozones CC22-CC23a (UC15d-eTP to UC16aTP). Results obtained on carbon isotopes suggest that diagenesis affected and compromised a few carbonate samples in the uppermost 50 m of the section. However, once these samples are discarded, pristine trends suggest that the top of the section records a negative carbon isotope excursion that is interpreted as CMBa-c events that straddle the Campanian–Maastrichtian boundary. This interpretation is supported by the lowermost occurrence of planktic foraminifers Rugoglobigerina scotti and Contusotruncana contusa some 30 m above the base of the negative excursion and 10 m below a positive excursion identified as the Maastrichtian M1+ event. Discrepancies in the stratigraphic range of several planktic foraminifer bioevents are highlighted and advocate for the need of many more integrated records of planktic foraminifer and nannofossil biostratigraphy alongside carbon isotope stratigraphy in the eastern Tethys in order to improve regional and global schemes.