Conference Agenda

High-resolution analysis of outcrops, cores, and logs from central Kansas provide new insights into the evolution of the Greenhorn marine cycle in Central, KS. This sequence, comprising the upper Dakota Fm., Graneros Shale, and Greenhorn Limestone, records the transition from non-marine to marine clastic, and carbonate depositional systems that resulted from eastward transgression of the WIS shoreline. This study refines previously outlined stratigraphic frameworks by combining modern chronostratigraphic techniques including U-Pb radiometric age dating and carbon stable isotope analyses with sequence-stratigraphic characterization.

Multiple orders of framework surfaces and major carbon isotope excursions are identified and correlated using absolute age control and relative markers. The lower package comprises a thick succession of coastal plain paleosols and fluvial deposits. An abrupt erosional transition is overlain by a conformable succession of tidally influenced sandstones and argillaceous mudstones that record the transgression of the WIS. The sandstones are overlain by 10m of argillaceous mudstone that comprises at least six parasequences and records successive drowning of the margin. The highstand succession records a transition from detrital (Graneros Shale) to carbonate-dominated marine sedimentation (Greenhorn Limestone). A high confidence regionally correlative ash bed previously hypothesized to be the 95.53 ± 0.36 Ma “X-Bentonite” in the upper Graneros Shale is used to date the maximum flooding surface. Our new ICP-MS and CA-TIMS analyses have produced significantly younger ages, shifting previously interpreted biostratigraphic and stable carbon isotope chemostratigraphic correlations along the eastern margin of the WIS.

The Opole Basin (southwestern Poland) preserves an expanded, fossiliferous Turonian to Coniacian succession, exposed through numerous cement quarries in the immediate vicinity of Opole. It serves as an important composite reference section for this interval in Europe, in part due to a rich record of many representative macrofossil and microfossil groups. Furthermore, it is situated near the nexus of the Bohemian Cretaceous Basin and the Central European Basin, providing unique opportunities for inter-correlation.

Here, we present a revised, high-resolution, integrated stratigraphic scheme of the accessible succession. A new inoceramid biozonation places the succession between the Inoceramus apicalis Zone (lower middle Turonian) and the Cremnoceramus deformis–C. crassus Zone (upper Lower Coniacian). Although the middle Coniacian is not presently exposed, it is observed further to the west in the subsurface. Ammonites are particularly well-represented in the Turonian, including enormous representatives of the genera Lewsiceras and Pachydesmoceras. The succession yields a rich and representative record of both planktonic (Dicarinella, Helvetoglobotruncana, Marginotruncana, and Falsotruncana) and benthic (Gavelinella, Globorotalites, Eponides, Lingulogavelinella, and Protostensioeina) foraminiferal lineages, providing a rare opportunity for the direct correlation of both groups in central Europe. Other invertebrate groups are well-represented, including ostracods (including the stratigraphically important genera Neocythere, Imhotepia, Bythoceratina, and Cytherelloidea), dinoflagellates, echinoids, and sponges. An independent chronostratigraphic framework is provided by a new carbon isotope chemostratigraphic record. This detailed integrated framework may help to better delineate the biotic and correlative significance of this keystone succession.

We present high-resolution (10–25 cm interval) carbonate carbon- and oxygen-isotope records (δ¹³C_carb, δ¹⁸O_carb) for the 162 m thick Chalk section exposed in the cliffs at Seaford Head, southern England. This reference section for the Upper Cretaceous of NW Europe has been proposed as a global reference for the Coniacian–Santonian and Santonian–Campanian stage boundaries and is designated an auxiliary GSSP boundary stratotype for the Campanian Stage. Carbon isotope stratigraphy, comprising 30 named carbon-isotope events (CIEs), supported by lithostratigraphy, macrofossil, microcrinoid, microfossil and calcareous nannofossil biostratigraphy, allows for precise correlation to other key European sections. CIEs provide the means of placing the Coniacian (top Navigation CIE) and Campanian (top Late Santonian Event) stage boundaries, while the lowest occurrence of Cladoceramus undulatoplicatus defines the base Santonian. Our holostratigraphic approach allows for intercalibration of biozonation schemes and chemostratigraphy. Spectral analysis of carbon and oxygen isotope profiles at Seaford Head demonstrates a clear expression of 405 kyr orbital cycles, offering the basis for orbital tuning of the isotope time series. Correlation of the Seaford Head orbital time scale to geochronological ages of bentonites from the US Western Interior Basin permits anchoring of the isotope records to various astronomical solutions. We favour a tuning approach to the La04 sinusoidal eccentricity solution along with a tie of 405 kyr minima to existing Laskar/Zeebe solutions for age calibration of biostratigraphic datum levels. Our results provide a basis for improved correlation and age calibration of Coniacian to Campanian successions at a regional to global scale.

The recent definition of the Santonian/Campanian boundary based on magnetostratigraphy (the C34N-C33R magnetic reversal boundary) by Gale et al, 2023, marks an important advance in attempting to correctly correlate the Santonian and Campanian Stages and their substages far from the European stratotypes. Unfortunately, the Gale et al, 2023 contribution made a fundamental error in the placement of this boundary in the Northeast Pacific (British Columbia, California, and Baja California), the Northwest Pacific (Japan and Sakhalin), and Antarctica. Data will be presented demonstrating that the C34N/C33R reversal most closely aligns with the base of the Canadoceras yokoyamai Zone in North America, Japan, and Sakhalin, and with the base of the newly defined, Anapachydiscus naumanni Zone (lowest Campanian) in Antarctica, allowing direct correlation to Japan and Sakhalin. Based on this error, the diachroneity between the stage boundary stratotype in Italy, and each of these regions, is estimated at one to three million years. In this talk, the state of magnetostratigraphy for the Santonian through Maastrichtian will be summarized with reference to both new magnetostratigraphic results and how chron boundaries in this vast "Pacific Basin" correlate to ammonite and inoceramid biostratigraphy in North America, Japan, Sakhalin and Antarctica. Proposals for new, stage boundary, auxiliary stratotype sections will be presented, as well a new proposal for a three substage Campanian and two substage Maastrichtian defined by ammonite biostratigraphy integrated with magnetostratigraphy. The timing of the first occurrences of globally cosmopolitan, Campanian Stage Baculites species will also be presented in support of a three substage Campanian.

The Oslen-Krivodol section is situated in the western Fore-Balkan Mountains, in a Peritethyan palaeogeographic position. The lower part of the studied 7m section is composed of green to greenish glauconitic limestones (Darmantsi Formation), overlain by thin- to medium bedded limestones, clayey and nodular limestones (Kunino Formation). A complete nannofossil zonal succession could be established, from the uppermost Campanian to the lowermost Maastrichtian, with subzones UC15c^TP, UC15de^TP, UC16a^TP and UC16b^TP. The nannofossil bioevent for the base of the Maastrichtian, the LO of Uniplanarius trifidus, is at 3.25m in the section. Strontium isotope stratigraphy indicates the C-M-boundary around 0.707736±5. Additional nannofossil bioevents include the FO and LO of Microrhabdulinus ambiguus below those two inferred CMB levels, and the decrease of warm-water nannofossil indicators like Watznaueria spp. indicating cooling along the Campanian Maastrichtian Boundary carbon isotope event. Two dinocyst zones have been recognized in the section: the upper Campanian Areoligera coronata and the lower Maastrichtian Cerodinium diebelii Zone. Their boundary is marked by the last occurrence of typical Campanian taxa (Odontochitina, C. robusta, C.horridum, A. fenestra) and the appearance of Maastrichtian forms (C. diebelii, M. carpentierae, Glaphyrocysta). inoceramid bivalves were collected from one level in the upper part of the Kunino Formation, represented mainly by the genus Cataceramus, but Endocostea is also present: Endocostea typica Whitfield, 1880; Cataceramus pallisieri (Douglas, 1942); Cataceramus subcircularis (Meek, 1876) and Cataceramus barabini (Morton, 1834). Based on the presence of E. typica we can indicate the upper part of eponymous inoceramid zone at the base of the Maastrichtian.

Certain doubts regarding the definition of the Global Boundary Stratotype Section and Point (GSSP) for the base of the Maastrichtian Stage (Tercis-les-Bains in southwest France) have led the Subcommission on Cretaceous Stratigraphy to establish a new Maastrichtian Working Group. The main tasks undertaken by the group include verifying the validity of the highest (HOs) and lowest (LOs) occurrences of micro- and macrofossil taxa that were used to define the Campanian–Maastrichtian transition and, if necessary, proposing new boundary indicators, including a primary boundary marker. Three of the twelve currently valid boundary criteria are dinoflagellate cyst (dinocyst) events, but only one of them (the HOs of Raetiaedinium evittigratia and R. truncigerum) has shown real biostratigraphic value. Other formal dinocyst boundary markers either disappear high above the GSSP level (Samlandia carnarvonensis, S. mayi) or has a limited geographical distribution (Corradinisphaeridium horridum). Potential candidates for new dinocyst boundary markers include the HOs of Callaiosphaeridium asymmetricum, Coronifera oceanica, Odontochitina costata, Xenascus ceratioides, and the LOs of Cladopyxidium saeptum, C. verrucosum, Florentinia mayi, Glaphyrocysta expansa, and G. pala. Although Callaiosphaeridium asymmetricum and Florentinia mayi have not yet been found in Tercis (the latter occurs in the geographically nearby Zumaia in northern Spain), all the above-mentioned bioevents have been shown to be geographically widespread, indicating their potential biostratigraphic importance. Understanding the actual relevance of the mentioned dinocyst events requires refined and highly-resolved studies at the GSSP site, including comparison with other Campanian–Maastrichtian dinocyst records precisely tied to the chronostratigraphic framework.