THE PIONEERING CONTRIBUTIONS AND LEGACY OF WALDO H. ZAGWIJN (1928-2018)

Professor Dr. Waldo H. Zagwijn passed away on 26 June, 2018, in his ninetieth year. His thesis research (Zagwijn, 1960) stimulated palynological investigations into the Pliocene and early Quaternary, and caused a fundamental shift in our under-standing of the transition from the warm and relatively stable climate of the late Neogene to the extreme glacial-interglacial oscilla-tions of the early Quaternary. Distinct in several aspects from the usual methodologies of that time, Zagwijn’s approach can be summarized as: focusing on establishing the botanical identification of pollen grains, following the guiding approach of his supervisor F. Flor-schütz, using botanical nomenclature to highlight these identifications and clarifying relationships between botany and the ear-lier artificial pollen nomenclature; comprehensive and continuous attention to plant macroremains (fruits, seeds, etc.; Zagwijn, 1990) as a mean of integrating classical palaeobotany with modern palynology; palaeoenvironmental interpretations informed by a deep understanding of modern plant ecology and associations; leading investigations in the field, and paying special attention to stratigraphic correlations between (onshore and offshore) boreholes and exposed sections in quarries, using a range of available proxies including heavy mineral analysis. Waldo H. Zagwijn was a visionary in realizing how modern palynology can be used for vegetational and climatic reconstructions in the Neogene, and indeed as far back as Paleogene times

The Messinian Salinity Crisis in the Dacic Basin (SW Romania) and early Zanclean Mediterranean-Eastern Paratethys high sea-level connection

International audienceNew field observations and fossil analyses complete and clarify the strong impact of the Mediterranean sea-level changes linked to the peak of the Messinian Salinity Crisis on the Dacic Basin in southwestern Romania. In addition to the Gilbert-type fan delta already evidenced along the Danube River in the area of Turnu Severin, a new Gilbert-type fan delta is described northward. Early Zanclean bottomset beds are evidenced and dated based on nannofossils at the junction of the two coalescing Gilbert-type fan deltas. A clear sedimentological, morphological and chronologic differentiation is established in the area between the Carpathians Late Miocene piedmont alluvial fans and the early Zanclean Gilbert-type fan deltas. The early Zanclean age of the Hinova clays, where the bottomset beds of the Gilbert-type fan deltas are mostly developed, is confirmed by the occurrence of nannofossil markers of Subzone NN12b and a Bosphorian mollusk macrofauna. Early Zanclean inflow of Mediterranean marine waters into the Dacic Basin is also supported by the record of planktonic foraminifers. In the Dacic Basin, the Messinian Salinity Crisis resulted in the cutting of the Iron Gates by a Carpathians river. Fluvial erosion also affected the residual Pannonian Basin and probably catched the paleo-Tisza River which contributed to the erosion of the Iron Gates and to the fluvial drainage of the partly desiccated Dacic Basin. Arguments are reinforced in favor of a marine gateway between the Mediterranean and Dacic Basin through the Balkans before and after the Messinian Salinity Crisis

Lago Mare and the Messinian Salinity Crisis: Evidence from the Alboran Sea (S. Spain)

International audienceThis paper provides a new environmental, sedimentological and stratigraphic context of the Lago Mare deposits from the North Alboran region and clarifies their chronologic location with respect to the Messinian Salinity Crisis. We present new micropaleontological data (dinoflagellate cysts, calcareous nannoplankton, planktonic foraminifers), correlated with field observations and offshore seismic interpretations. We show that the Lago Mare event known in three onshore localities (Río Mendelín near Malaga, Zorreras near Sorbas, Gafares near Níjar) follows the marine reflooding of the Mediterranean Basin which ended the Messinian Salinity Crisis. Chronologically, these Lago Mare deposits last from the latest Messinian to the early Zanclean. In fact, the first influx of Paratethyan- organisms is revealed by the dinoflagellate cyst record from near Malaga within a Gilbert-type fan delta overlying the Messinian Erosional Surface. Invading molluscs and/or ostracods may have persisted in lagoonal coastal areas more or less affected by discontinuous marine influxes (Sorbas and Níjar). The Malaga area is convenient for a paleogeographic and sedimentary reconstruction which shows the prevalent forcing of sea level changes during the time-interval 5.600-5.332 Ma at the difference of the usually solicited prevalent tectonics. The studied Lago Mare event is the third episode resulting in such a paleobiological assemblage in the Mediterranean region and corresponds to the final two-way water exchange at high sea level between the Mediterranean and the former Paratethys. It documents the onset of the modern marine circulation in the Mediterranean after the reflooding ending the Messinian Salinity Crisis

New insights on the Sorbas Basin (SE Spain): the onshore reference of the Messinian Salinity Crisis

International audienceThe Sorbas Basin is the land reference of the Messinian Salinity Crisis (MSC) that affected the Mediterranean Sea in the latest Miocene. Its stratigraphy has been re-visited using calcareous nannofossils and planktonic foraminifers, which provide a reliable biostratigraphic frame and lead to particularly specify the relationships between the Sorbas and Zorreras members with Yesares evaporites.The evaporites overlie a shallowing upward sequence ending with the deposition of the Reef Unit and Terminal Carbonate Complex (TCC) on the periphery of the basin. The reefal carbonates of the TCC are overlain by clastic deposits that are foreset beds of post-MSC Gilbert-type fan deltas developed on the northern edge of the basin. These sedimentary structures are separated from reefal carbonates and the Reef Unit by the Messinian Erosional Surface (MES). The various facies of the Sorbas Member have been correlated with the bottomset beds of the Gilbert-type fan deltas despite some differences in palaeobathymetry. In the southeastern periphery of the basin, the MES separates the Sorbas Member from the Yesares gypsums. In the central part of the basin, a hiatus characterizes the contact between these members. The Zorreras Member postdates the MSC and entirely belongs to Zanclean. Its white “Lago Mare” layers are lagoonal deposits, the fauna of which is confirmed to result from Mediterranean–Paratethys high sea-level exchange after the post-MSC marine reflooding of the Mediterranean Basin.This study allows to re-assert the two-step scenario of the MSC (Clauzon et al., 1996) with the following events:- at 5.971–5.600 Ma, minor sea-level fall resulting in the desiccation of this peripheral basin with secondary fluctuations;- at 5.600–5.460 Ma, significant subaerial erosion (or lack of sedimentation) caused by the almost complete desiccation of the Mediterranean Sea;- instantaneous marine reflooding, accepted at 5.460 Ma, followed by continuing sea-level rise

New Insights on the Sorbas Basin (SE Spain): the onshore reference of the Messinian Salinity Crisis

The Sorbas Basin is the land reference of the Messinian Salinity Crisis (MSC) that affected the Mediterranean Sea in the latest Miocene. Its stratigraphy has been re-visited using calcareous nannofossils and planktonic foraminifers, which provide a reliable biostratigraphic frame and lead to particularly specify the relationships between the Sorbas and Zorreras members with Yesares evaporites. The evaporites overlie a shallowing upward sequence ending with the deposition of the Reef Unit and Terminal Carbonate Complex (TCC) on the periphery of the basin. The reefal carbonates of the TCC are overlain by clastic deposits that are foreset beds of post-MSC Gilbert-type fan deltas developed on the northern edge of the basin. These sedimentary structures are separated from reefal carbonates and the Reef Unit by the Messinian Erosional Surface (MES). The various facies of the Sorbas Member have been correlated with the bottomset beds of the Gilbert-type fan deltas despite some differences in palaeobathymetry. In the southeastern periphery of the basin, the MES separates the Sorbas Member from the Yesares gypsums. In the central part of the basin, a hiatus characterizes the contact between these members. The Zorreras Member postdates the MSC and entirely belongs to Zanclean. Its white "Lago Mare" layers are lagoonal deposits, the fauna of which is confirmed to result from Mediterranean-Paratethys high sea-level exchange after the post-MSC marine reflooding of the Mediterranean Basin. This study allows to re-assert the two-step scenario of the MSC (Clauzon et al., 1996) with the following events: - at 5.971-5.600 Ma, minor sea-level fall resulting in the desiccation of this peripheral basin with secondary fluctuations; - at 5.600-5.460 Ma, significant subaerial erosion (or lack of sedimentation) caused by the almost complete desiccation of the Mediterranean Sea; - instantaneous marine reflooding, accepted at 5.460 Ma, followed by continuing sea-level rise

Continental and Marine Environmental changes in Europe induced by Global Climate variability and Regional Paleogeography Changes

version originaleMy PhD and post-doctorate researches have focused on paleoclimatic, paleogeographical and paleoenvironmental reconstruction of the Mediterranean Basin and its adjacent seas (i.e. the residual former Paratethys) since 11 Ma. During this time-interval the Mediterranean marine and continental environments were affected by significant paleogeographic changes, forced by global climate and sea-level variability, plate tectonics and regional uplift of Alps s.l. and Carpathians. Two main important events characterize this period: the isolation and evolution of Paratethys and the almost complete desiccation of the Mediterranean Sea, an event known as the Messinian Salinity Crisis. I selected this region because it is very rich in long and continuous sediment archives, which document: (1) climate evolution of the Northern Hemisphere during the Late Cenozoic with respect to vegetation changes, and (2) progressive evolution of initially marine environments towards brackish and freshwater ones. The brackish to fresh environments had a profound effect on the marine organisms (especially dinoflagellates) that responded to the stress by developing a large variety of cyst morphologies, often described as new genera and/or species. Methods. The comparative analysis of pollen grains and dinoflagellate cysts from the same samples is rarely performed for such a long time-interval because it needs a deep knowledge in taxonomy and ecology of the both complementary proxies. I reached this parallel expertise, having the benefit of training in (1) botanical identification of pollen grains from the tropical to boreal zones and their ecological significance by Dr. J.-P. Suc, (2) taxonomy and ecology of dinoflagellate cysts by Pr. M. J. Head. To achieve an understanding of the primary factor inducing morphological variations of dinoflagellate cysts, I developed a biological approach (culturing and growing of present-day living dinoflagellates and inducing stress on microcultures experimentations) under supervision of Pr. J. Lewis (Westminster University, London, UK) and Drs. D. Anderson and D. Kulis (WHOI, USA) during my postdoc appointments. The simultaneous work on living and fossil (using biometry and associated statistical analyses) dinoflagellate cysts has allowed me to initiate the development of a transfer function, widely valid and able for the modelling of the physical parameters of sea-surface waters (salinity, temperature, nutrient contents). Such analyses were performed at high- to very high-chronological resolution, as resulting from the following approach: (1) independently established age-model, based on classical biostratigraphy or radiocarbon ages (for recent sediments), completed by magnetostratigraphy for deposits prior to Mid–Quaternary; (2) comprehensive counting of pollen grains (150 per sample, Pinus or any overabundant taxon excepted) and dinoflagellate cysts (200-300 per sample); (3) interpreting the resulting data with respect to ecological requirements. High- to very high-resolution analyses provides results directly comparable with classical oxygen isotope curves. These signals can therefore also be tuned to the frequency of eccentricity, obliquity and precession cycles. Although palynological proxies can be considered as standard, my integrated approach hoists them at the level of the most competitive methods. Another aspect consists in its present-day background, based on many surface samples from the Mediterranean, Marmara and Black seas, taken during several cruises and sampling parties at IFREMER-Brest and WHOI. To develop parallel analyses of pollen grains and dinoflagellate cysts offers additional considerable interests, such as (1) continuous records of climatic changes and sea-level variations independently from sediment types, and (2) quantifications (using transfer functions) of climate for both continental and marine (to brackish) realms as well as of physical oceanic parameters (SST, SSS, nutrient content etc.).Results and research in progressUsing pollen grains analysis, I developed investigations on vegetation dynamics and paleoclimate reconstructions for the whole Mediterranean region and Western Europe extended to the Late Cenozoic (Jiménez-Moreno et al., 2007; Fauquette et al., 2006). Thanks to the high-chronologic resolution: a. I established the response of regional vegetation to eccentricity forcing in SW Romania (Dacic Basin) and Black Sea (DSDP Site380) whatever the sediment types (Popescu, 2001, 2006; Popescu et al., 2006a);b. I was the first to demonstrate the precession forcing on regional vegetation (Popescu et al., 2006b) through the Lupoaia pollen record (SW Romania);c. in the frame of two PhD theses that I co-supervise, pollen grain and dinoflagellate cyst records from DSDP Site 380 (7 - 4 Ma) were completed from 4 Ma to Present in order to evidence the impact of glacial-interglacial cycles over the regional vegetation and to reconstruct the climate variability for the last 7 Ma;d. I was the first to demonstrate the solar cycles forcing (Hale and Gleissberg cycles) on the regional vegetation (through the “Thermophilous trees / Artemisia” ratio) since the Last Glacial Maximum were evidenced in cored sediments from the Black and Marmara seas (unpublished data), that is a unique outcome. Using the biometric approach on the dinoflagellate cysts in association with statistical analyses, I demonstrated that fluctuations in salinity are partially responsible for modifying size, shape and ornamentation of the cysts, providing the first reliable paleoecological and paloebiogeographic reconstructions of the brackish Paratethyan basins (Popescu et al., palynology , in press). Simultaneously, I performed experimental cultures on a living-dinoflagellate species (Scrippsiella trifida): suggested relationships between cyst morphological variations and stress under controlled salinity are confirmed by the preliminary results, while reproduction rate seems also modified (unpublished data). The multi-proxy (palynology, sedimentology and geochemistry) study on the Aral Sea, done by the first PhD student that I co-supervised, allowed not only the reconstruction of the regional paleoclimate and paleoenvironments, but also permitted to understand the atmosphere dynamics of the last 2 ka over the high latitudes (Sorrel et al., 2006, 2007). Hence, my palynological and biological expertise offers an exclusive tool for establishing a continuous high resolution chronology, paleoclimatic, paleobiogeographic and paleoenvironmental reconstructions. This is particularly important for the basins impacted by important environmental changes, such as the Mediterranean and Black seas, the sediments of the latter being precisely dated for the first time by this approach.I do no want to close this Introduction Section without addressing my largest acknowledgements to those who supported my researches and expressed their interest in my project, providing personal grants and/or financial assistance for achieving my researches, and especially the PhD and master – graduation students that I appreciated so much to co-supervise

Late Miocene and early Pliocene environments in the southwestern Black Sea region from high-resolution palynology of DSDP Site 380A (Leg 42B)

International audienceA high-resolution palynological study has been performed on late Miocene (Messinian) and early Pliocene (Zanclean) sediments cored at DSDP Site 380A (Leg 42B). A late Miocene coastal vegetation has been identified in association with a delta environment. The Pliocene is characterised by competition between the two most important vegetation components, namely humid thermophilous forests and dry steppes, with changes driven by large amplitude climatic variations. These variations are linked to other European reference pollen records and to the global temperature evolution for the early Pliocene, and result in climatostratigraphic relationships at large geographic scale. An orbital tuning is proposed with respect to new data clarifying time control on the section. The Black Sea appears to have dried up in response to the Messinian salinity crisis in the Mediterranean with which it might have been connected during periods of high sea level

Influence des cycles astronomiques sur la végétation du bassin Dacique au Pliocène inférieur d’après la palynologie

Popescu Speranta-Maria. Influence des cycles astronomiques sur la végétation du bassin Dacique au Pliocène inférieur d’après la palynologie. In: Documents des Laboratoires de Géologie, Lyon, n°156, 2002. STRATI 2002. 3ème congrès français de stratigraphie. Lyon, 8-10 juillet 2002. pp. 186-187

Végétation, climat et cyclostratigraphie en Paratéthys centrale au Miocène supérieur et au Pliocène inférieur d'après la palynologie

version originaleHigh-resolution palynological analysis has been performed on five well-dated Early Pliocene sections from southeastern Europe: Hinova, Valea Visenilor, Husnicioara and Lupoaia in the Dacic Basin (southwestern Romania), DSDP Site 380A (Black Sea) which also includes latest Miocene sediments (Messinian). Pollen floras show how this region was relatively protected from floristic extinctions which occurred in Europe during the Late Pliocene and the Quaternary because of glacial-interglacial cycles. A noticeable effect of Asian monsoon has probably encouraged persistence in this area of some themophilous species up today. Altitudinal forest belts have been reconstructed on the southern Carpathians. Palaeo-Danube delta was rich in swamps inhabited by Cypress forest and marshes occupied by grasses (Cyperaceae) as today in Florida and Mississippi delta. The descent of the altitudinal gymnosperm belts is evidenced in relation with each "cooling" with respect to eccentricity 100 kyrs cycles. On contrary, warmer phases forced development of thermophilous trees and lignite deposition. Asian monsoon probably controlled opposing development of swamps and marshes with respect to precession 20 kyrs cycles. Precession minima (monsoon enhancement) advantaged marshes which requires more humidity than swamps. A comparison is possible with the Mediterranean sapropels, the forcing of which being also the precession rhythm. This suggests the establishment in Early Pliocene of a longitudinal gradient over the Mediterranean region. As today, a strong contrast separated vegetation features from Dacic and Pontic realms. In the latter, thermic cycles forced competition between thermophilous trees and Artemisia steppes, the early development of which announces their forthcoming development over the whole Mediterranean region in relation with earliest glacials (2.6 Ma). Such high-resolution pollen analyses provide a very detailed climatic record for the region with respect to global climatic changes between 6 and 3.8 Ma. Resolution of pollen records reaches that of reference 18O curves. So, weak variations in temperature and humidity occurring during the warm Pliocene will be more understood as well as their effects on the vegetation. The European Pliocene climatostratigraphy is confirmed and Central Paratethyan deposits receive for the first time a reliable cyclostratigraphy. Relationships will be easier with the reference Mediterranean marine sections. Consequences of the Mediterranean Sea desiccation (Messinian salinity crisis: 5.7-5.32 Ma) over the Black Sea have been evidenced: they concern both coastal vegetation and dinoflagellate assemblages. A new idea of Mediterranean Sea - Central Paratethys relationships is proposed for a better explanation of the events bordering the salinity crisis.La méthode de l'analyse palynologique à haute résolution a été appliquée à cinq coupes du Pliocène inférieur du sud-est de l'Europe qui bénéficiaient d'un très bon cadre géologique et chronologique: Hinova, Valea Visenilor, Husnicioara, et Lupoaia dans le bassin Dacique (sud-ouest de la Roumanie), Site DSDP 380A (mer Noire) qui inclut également le Miocène terminal (Messinien).L'étude de la flore pollinique illustre comment cette région est demeurée relativement protégée de l'hécatombe qui a affecté la diversité floristique d'Europe au cours du Pliocène supérieur et du Quaternaire en raison des cycles glaciaire-interglaciaire. Une influence certaine de la mousson asiatique y a permis le maintien jusqu'à nos jours de plusieurs espèces thermophiles.L'organisation altitudinale de la végétation forestière a pu être reconstruite sur le versant méridional des Carpathes. Les marécages du delta du paléo-Danube évoquent les environnements actuels du delta du Mississippi et de Floride (« swamps » arborés, « marshes » herbacés). Les étages végétaux supérieurs s'étendaient vers des altitudes plus basses à chaque « refroidissement » selon des cycles de 100.000 ans contrôlés par l'excentricité, tout comme, à l'opposé, les arbres thermophiles (et les couches de lignite) se développaient lors de chaque réchauffement. Une compétition existait entre « swamps » et « marshes » au gré des intensifications de la mousson asiatique sur le sud-est de l'Europe selon les cycles de la précession (période de 20.000 ans). Ces intensifications de la mousson (minima de précession) avantagaient les « marshes » qui demandent davantage d'humidité que les « swamps ». La comparaison avec les dépôts de sapropèles méditerranéens, contrôlés par le même facteur astronomique, fait apparaître qu'il existait au Pliocène un gradient longitudinal sur la zone méditerranéenne. Le contraste est fort dans la végétation, comme aujourd'hui, entre les domaines Dacique et Pontique. Dans cette dernière région, la compétition commandée par les cycles thermiques de l'excentricité concerne d'une part les arbres thermophiles, d'autre part les formations steppiques à Artemisia. Leur développement précoce annonce leur extension à tout le domaine méditerranéen lors des premiers cycles glaciaire-interglaciaire (2,6 Ma).Cette étude à haute résolution fournit aussi un enregistrement très détaillé du climat régional en relation avec l'évolution globale du climat pour la période comprise entre 6 et 3,8 Ma. La résolution atteint celle de la courbe isotopique de l'oxygène de référence. Ainsi, connaît-on mieux les effets des variations minimes de la température et de l'humidité sur la végétation au cours d'une période chaude. Il s'en suit une climatostratigraphie à l'échelle de l'Europe et une cyclostratigraphie des dépôts de Paratéthys centrale qui peuvent ainsi être précisément corrélés aux sédiments méditerranéens de référence.Les effets de la dessiccation de la mer Méditerranée (crise de salinité messinienne, entre 5,7 et 5,32 Ma) sur la mer Noire sont nettement perceptibles que ce soit sur la végétation littorale ou sur la flore aquatique de dinoflagellés. On en déduit une nouvelle vision des relations entre mer Méditerranée et Paratéthys centrale avant et après cette crise