Palaeogeography, Palaeoclimatology, Palaeoecology 441 (2016) 391–392
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Preface
Advances and Perspectives in Understanding Cretaceous Sea-level Change The special issue at hand represents the Proceedings of the joint 2nd UNESCO-IUGS IGCP 609 “Climate-environmental deteriorations during greenhouse phases: Causes and consequences of short-term Cretaceous sea-level changes” and ESF EARTHTIME-EU Sequence Stratigraphy Workshop “Eustasy and sequence stratigraphy in the Cretaceous Greenhouse” that took place in Bucharest, Romania, on August 23–25, 2014. IGCP 609 investigates Cretaceous (145 Ma–66 Ma) sea-level cycles in detail in order to differentiate and quantify both short- and long-term records within the new high-resolution absolute time scale based on orbital cyclicity (http://www.univie.ac.at/igcp609/; lasting from 2013–2017). The project serves as a communication and collaboration platform bringing together specialists and research projects from all over the world (from universities and other research facilities, from the industry and from stratigraphic consulting companies). IGCP 609 is focusing on the causes and mechanisms of short-term cycles of 3rd and 4th order, (i.e., about 0.5–3.0 Ma and a few tens of thousands to 0.5 Ma, respectively) eustatic (i.e. global) sea-level changes in the mid-Cretaceous “Supergreenhouse” or “hothouse” periods (Cenomanian–Turonian) during which continental ice sheets are highly improbable and, thus, other mechanisms have to be taken into consideration to explain significant short-term eustatic changes. The focus on short-term eustatic sea-level changes also arises from their importance for stratigraphic application: the interrelation of short-term climate changes and eustatic sea-level changes, their analysis for astronomically driven cyclicities, and their cyclostratigraphic and sequence stratigraphic application. This issue combines an up-to-date overview of our understanding of the causes and consequences of global Cretaceous short-term sea-level changes with reviews and case studies covering more specific aspects. It comprises a total of 13 papers, including 4 reviews and 9 case studies, covering a wide range of aspects related to Cretaceous short-term sealevel changes: their geologic record, their documentation and stratigraphy, concepts, approaches and methods to document and analyze the processes and controlling factors behind, analysis and interpretation, as well as effects on biota and extinction events. 1. Reviews The introductory review by Sames et al. gives an up-to-date synopsis of our understanding of, and research on, the fundamentals of sea-level change today and in the geologic record. Classification, measurement, processes and drivers of regional and global sea level and sea-level changes are elucidated and discussed with respect to their significance in affecting global sea-level changes at different periods of Earth history, timescales and amplitudes with focus on the Cretaceous greenhouse climate episode. By example of mid-Cretaceous data, Wendler and Wendler thoroughly review the drivers and processes behind (short-term) sea-level
http://dx.doi.org/10.1016/j.palaeo.2015.10.040 0031-0182/© 2015 Published by Elsevier B.V.
fluctuations during greenhouse climate. The authors present a more differentiated interpretation of the oxygen-isotope fractionation process during different climate modes. While both aquifer-eustatic and glacio-eustatic forcing have formed a combined sea-level response during earth history – glacio-eustasy is the dominant process during icehouse mode while aquifer eustasy dominates during greenhouse mode. Along with different temperature effects on oxygen-isotope fractionation corresponding to the respective climate mode, this results in considerably different net seawater δ18O values, with respective impact on their possible interpretation. Hart, FitzPatrick and Smart review the presence (or absence, respectively) of sequence boundaries below and above the CretaceousPaleogene (K/Pg) boundary, and whether rapid sea-level changes (falls) around this boundary be N25 m (even 50–100 m), as previously suggested, or much less. Based on the presence and precise ecological requirements of sea-grass meadows and associated foraminifera in respective deposits of the Maastricht area, the authors come to the conclusion that some of the latest Maastrichtian non-glacial (or limited glacial) world, sea-level changes must have been relatively minor, only a few meters. Wendler, Wendler, Vogt and Kuss present the first empirical evidence for a correlation between changes in precipitation, continental weathering intensity, and evaporation and astronomically (long-obliquity) forced sea-level cycles during the (Cenomanian–Turonian) Cretaceous Supergreenhouse period. The authors compare sequencestratigraphic data with changes in the terrigenous mineral assemblage in a low-latitude marine sedimentary sequence from the Levant carbonate platform, Jordan (equatorial humid belt, South-Tethyan margin). By demonstrating covariance between cycles in weathering and sea level the authors present empirical evidence for aquifer-eustasy in the Cretaceous. 2. Case studies (arranged from younger to older) Lamolda, Melinte-Dobrinescu and Kaiho evaluate a high-resolution record of calcareous nannoplankton assemblage changes around the Cretaceous-Paleogene boundary at Agost, Spain. Calcareous nannoplankton assemblage deterioration started already towards the top of the Maastrichtian, at around 7 ka prior to the boundary event, interpreted to be indicative for ocean water acidification. Four successive acme events were observed above the boundary, for which the survival strategy may be linked to the capability of certain nannoplankton species to encyst, and to survive severe environmental deterioration. The correlation between the calcareous nannoplankton assemblage fluctuations and eustatic and climatic changes are discussed. Açıkalın, Ocakoğlu, Yılmaz, Vonhof, Hakyemez and Smit report a case study on stable isotopes and geochemistry of a Campanian–
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Preface
Maastrichtian pelagic succession from NW Turkey. Based on highresolution correlations the authors discuss the implications for paleoceanography, paleoclimate and sea-level fluctuations during this time interval, working on the importance of regional versus global controlling mechanisms. Five δ13C events are identified, four of which are well correlatable with major events in other records around the world, such as the late Campanian Event (LCE), CampanianMaastrichtian Boundary (CMB) and the late Maastrichtian Event (LME). Other events are of only local or regional extend, exemplifying the importance of a multi-proxy study approach to identify tectonic versus climate controls on the archived sedimentary record. In their paper on pelagic environments and foraminiferal assemblages, Wolfgring, Hohenegger and Wagreich give a detailed account of paleoenvironments and changes recorded within a short time interval of the late Campanian. Foraminiferal paleoecology from two different sites is compared and evaluated in terms of oxygenation, depositional water-depths and sea-level fluctuations. Plankton assemblages show a remarkable stability hinting at the late Campanian as a time interval of general foraminiferal stasis without significant evolutionary events, despite the single appearance of a spined morphotype. The authors then speculate on the evolution of R. calacarata within an opening and closing adaptive zone due to progressively changing water masses. Kopaevich and Vishnevskaya investigate comprehensive micropaleontological (planktonic Foraminifera and Radiolaria) data from the Peri-Tethyan Late Cretaceous (Cenomanian–Campanian) of the Crimea-Caucasus area and interpret the paleoceanography, paleoclimate and sea-level changes from this depositional area that was transitional between the Boreal and Tethyan realms. The authors identify three episodes of significant sea-level falls in the area: between the Albian and Cenomanian, at the base of the OAE2 “black shale” layers, and in the latest middle and early Late Turonian. The first paleoceanographic crisis documented coincides with the Cenomanian–Turonian boundary event, which is connected to a sealevel rise, warm greenhouse conditions and OAE 2, and associated changes in the plankton community. Xi, Cao, Cheng, Jiang, Jia, Li and Wan evaluate the Late Cretaceous biostratigraphy and sea-level changes in the southwest Tarim Basin, China. Multi-proxy analyses of facies and sedimentation patterns, foraminifera, ostracods, and bivalves result in a regional, relative sea-level curve. Correlations to the global sea-level curve are established and discussed. A prominent sea-level drop is identified in the early-late Coniacian and may be correlated to the global sea-level curve. Wendler, Wendler and Clarke present sea-level reconstructions from the Turonian of the Tanzania Drilling Project (south Tethys Ocean) as based on integrated sedimentological, sediment-geochemical, microfacies, micropaleontological, and stable isotope data. The authors develop a high-resolution bio- and chemostratigraphy, correlate their sequences with other sections of the southern Tethys, provide an age model, and, combining their data and previously published δ18O values, discuss the consistency of their data with the model of aquifer-eustasy. In their case study on an Albian to Turonian deep marine sequence of the Central Pontides (Turkey), Tüysüz et al. define the Cenomanian– Turonian Kapanboğazı Formation, based on extensive micro- and nannofossil data. They discuss different stratigraphic interpretations of this key unit, and the impact on the geologic and paleoenvironmental setting development of the area. Sanchez-Hernandez and Maurrasse give a detailed look on oceanic anoxic event OAE 1a using a high-resolution, multi-proxy case study from the Pyrenees in Spain. Carbon isotope profiles are used for highresolution stratigraphic correlations. They reconstruct fluctuating oxygen conditions without full anoxia, and discuss regional versus global control on sedimentation. Local tectonics, basin physiography and eustatic sea-level rise are among the main factors controlling local facies changes. Zorina analyses and discusses sea-level controls on the Aptian depositional environments of the Eastern Russian Platform, Eastern part of
European Russia. The author presents a new Barremian–Albian regional 3rd order sea-level curve for the epicontinental sea that covered the area, which for the Aptian only consist of one major cycle (whereas the global curve comprises five 3rd order cycles). A major climate event, the late Aptian “cold snap” is identified, coinciding with simultaneous global and regional sea-level lowstands, and the lower Aptian bituminous shales of the Eastern Russian Platform are considered a regional manifestation of OAE 1a. The papers of this special issue combine different important aspects that are in the focus of IGCP 609. For the first time, a number of papers dealing with Cretaceous greenhouse sea-level changes is put together into this proceedings issue. Processes that control sea-level especially during greenhouse episodes of the Earth history are identified and discussed using both literature reviews and multi-proxy case studies from Cretaceous times. Works on Cretaceous short-term sea-level changes provide multiple case studies and applications of sea level changes in sequence stratigraphy and cyclostratigraphy framework. Alternative processes to glacio-eustasy during hothouse times are introduced, and the aquifer-eustatic concepts are tested in the stratigraphic record and evaluated in more detail by several papers of this volume. Magnitudes and rates of greenhouse sea-level fluctuations and related coeval paleoenvironmental changes are at the beginning to be reconstructed, and correlated into a precise and numerical Geological Time Scale. Acknowledgements We thank Yanping Hou and Krishnaveni R. Kunchala Reddy from Elsevier Science Publishing for continuing support, and, in addition, the reviewers of articles for this volume: Ernesto Abbate, Roque Aguado, Krzysztof Bąk, Claudia Cetean, Clint Conrad, Géza Császár, Hans Egger, Jacek Grabowski, János Haas, Malcolm Hart, William Hay, Jean-Claude Hippolyte, John W.M. Jagt, Mariusz Kedzierski, Jiří Laurin, Ewa Malata, Florentin Maurasse, Jozef Michalik, Sigrid Missoni, James Ogg, Richard K. Olsson, Mariano Parente, Maria-Rose Petrizzo, Piret Plink-Bjorklund, Isabella Premoli-Silva, Gregory Price, Relu Dumitru Roban, Brad Sageman, Bilal Sarı, Robert W. Scott, Mike Simmons, Ján Soták, Lilian Svábenická, Ines Wendler, Markus Wilmsen, Erik Wolfgring, Nicolas Thibault, Chen Xi. Michael Wagreich Department of Geodynamics and Sedimentology, Center for Earth Sciences, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria E-mail address:
[email protected] Bilal U. Haq Smithsonian Institution, Washington DC, USA, and Sorbonne, Pierre & Marie Curie University Paris, France E-mail address:
[email protected] Mihaela Melinte-Dobrinescu National Institute of Geology and Geoecology (GeoEcoMar), 23-25 Dimitrie Onciul Street, 024053 Bucharest, Romania E-mail address:
[email protected] Benjamin Sames Department of Geodynamics and Sedimentology, Center for Earth Sciences, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria E-mail address:
[email protected] İsmail Ö. Yılmaz Middle East Technical University, Department of Geological Engineering, 06800 Ankara, Turkey E-mail address:
[email protected]
