Claus Heilmann-Clausen

Global dinoflagellate event associated with the late Paleocene thermal maximum

The late Paleocene thermal maximum, or LPTM (ca. 55 Ma), represents a geologically brief time interval (∼220 k.y.) characterized by profound global warming and associated environmental change. The LPTM is marked by a prominent negative carbon isotope excursion (CIE) interpreted to reflect a massive and abrupt input of 12 C-enriched carbon to the ocean-atmosphere reservoir, possibly as a result of catastrophic gas-hydrate release, on time scales equivalent to present-day rates of anthropogenic carbon input. The LPTM corresponds to important changes in the global distribution of biota, including mass extinction of marine benthic organisms. The dinoflagellate cyst record indicates that surface- dwelling marine plankton in marginal seas also underwent significant perturbations during the LPTM. We report on the dramatic response of representatives of the genus Apectodinium from two upper Paleocene–lower Eocene sections in the Southern (New Zealand) and Northern (Austria) Hemispheres, where the dinoflagellate records are directly correlated with the CIE, benthic foraminifera extinction event, and calcareous nannofossil zonation. The results indicate that the inception of Apectodinium -dominated assemblages appears to be synchronous on a global scale, and that the event is precisely coincident with the beginning of the LPTM. Apectodinium markedly declined in abundance near the end of the LPTM. This Apectodinium event may be associated with (1) exceptionally high global sea-surface temperatures and/or (2) a significant increase in marginal-marine surface-water productivity. Such a globally synchronous acme of dinoflagellate cysts is unprecedented within the dinoflagellate cyst fossil record.

DINOFLAGELLATE CYSTS FROM THE MIDDLE EOCENE TO ?LOWERMOST OLIGOCENE SUCCESSION IN THE KYSING RESEARCH BOREHOLE, CENTRAL DANISH BASIN

Abstract Rich and well-preserved assemblages of organic walled dinoflagellate cysts in 50 samples from a 154 m thick and almost complete, Middle Eocene to ?lowermost Oligocene section from the Kysing Research Borehole in eastern Jylland, Denmark are systematically described. One genus Costacysta gen. nov., and twelve species Chiropteridium eocaenicum sp. nov., Costacysta bucina gen. et sp. nov., Distatodinium pilosum sp. nov., Echinidinium? lucidum sp. nov., Hapsocysta kysingensis sp. nov., Horologinella? pentagonalis sp. nov., Operculodinium eisenackii sp. nov., Phthanoperidinium cornutum sp. nov., Selenopemphix septum sp. nov., Svalbardella partimtabulata sp. nov., Thalassiphora gracilis sp. nov. and Thalassiphora microperforata sp. nov. are formally described. The genus Hapsocysta is emended, and is considered to be a senior synonym of Piccoladinium. The gradual change of the dinoflagellate cyst assemblages in this section demonstrates that sedimentation was almost continuous during the time span of ca. 12 Ma. The biostratigraphic resolution based on dinoflagellate cyst events is generally finer than the calcareous nannofossil NP biozonation. A comparison with published dinoflagellate cyst data from the Norwegian–Greenland Sea shows that several important events are mainly synchronous throughout the region, suggesting a general similarity of the water masses. An isolated occurrence of Svalbardella suggests a short cooling event during early Bartonian times. The palynofacies in most of the section is almost purely of pelagic type. A more proximal, mid shelf palynofacies and a distinctive episode of reworking coincide with the Upper Eocene Moesgaard Clay and indicate a brief, but rather large sea level fall during the deposition of this unit. The Eocene/Oligocene boundary is tentatively identified near the base of the Viborg Formation, and approximately coincides with increased reworking of dinoflagellate cysts and a strong increase in bisaccate pollen, indicating more proximal conditions and possibly also a climatic cooling.

Paleoproductivity of the northwestern Tethyan margin (Anthering section, Austria) across the Paleocene-Eocene transition

Sediments in the expanded Anthering Section at the northwestern Tethyan margin were deposited in an abyssal environment, at the continental rise to the south of the European plate. The section contains deposits from calcareous nannoplankton Zones NP9 and NP10 and displays the global negative carbon isotope excursion (CIE) in the upper part of Zone NP9. Associated with the CIE is a strong three-fold increase in the rate of hemipelagic sedimentation. This suggests an increased input of siliciclastic suspended material into the basin, which is indicative of enhanced continental runoff at that stratigraphic level. Concurrent acmes of siliceous plankton and dinoflagellate cysts indicate that a high input of dissolved nutrients affected even open marine settings and caused eutrophication of surface waters. The associated high flux of organic carbon to the seafloor resulted in oxygen-depleted conditions and caused the total extincton of benthic faunas. However, impoverished foraminifera faunas indicate that a change of ecological conditions started shortly before the CIE. 133 Egger, H., Fenner, J., Heilmann-Clausen, C, Rogl, F., Sachsenhofer, R.F., Schmitz. B., 2003, Paleoproductivity of the northwestern Tethyan margin (Anthering Section, Austria) across the Paleocene-Eocene transition, in Wing, S.L., Gingerich, P.D., Schmitz, B., and Thomas, E., eds., Causes and Consequences of Globally Warm Climates in the Early Paleogene: Boulder, Colorado, Geological Society of America Special Paper 369, p. 133–146.

Occurrence of major sequence stratigraphic boundaries in relation to basin development in Cenozoic deposits of the southeastern North Sea

The post-Danian Cenozoic succession in the southeastern North Sea is subdivided into seven informal “major sequence stratigraphic units”, comprising twenty-one sequences. The boundaries of the units are easily recognized on seismic sections over the entire study area. The North Sea is an epicontinental basin. It underwent considerable changes during the Cenozoic as regards subsidence rates, direction of sediment transport, and position of depocentres. The six unit boundaries are interpreted to reflect some of the major events in the development of the basin. The boundary between units 1 and 2 (earliest Eocene) is associated with a regional hiatus followed by a large relative sea-level rise, whereas the boundary between units 2 and 3 (Middle Eocene) coincides with a shift in the direction of sediment transport from north to west. The boundary between units 3 and 4 (Eocene-Oligocene transition) marks an important change in the depositional environment of the North Sea with a shift in the direction of sediment transport from west to mainly northeast. In the northeastern part of the study area, thick prograding deposits of unit 4 are situated on distal deposits of units 1, 2 and 3. The transition between units 4 and 5 (latest Oligocene) shows a pronounced basinward shift in onlap, and it is interpreted to reflect a major fall in the relative sea level. The boundary between units 6 and 7 (Middle Miocene) is identified on a shift from a prograding reflection pattern to an aggrading pattern. The lower part of unit 7 is interpreted to represent a starved depositional environment, related to a pronounced increase in subsidence rate. The North Sea sequences are correlated with the Danish onshore deposits. The sequence boundaries generally coincide with an unconformity in the Danish deposits. A glauconitic horizon characterises the initial deposits overlying each of the unconformities.

Stable isotope and biotic evolution in the North Sea during the early Eocene: the Albæk Hoved section, Denmark

Abstract Stable isotope (δ13C, δ18O) and biostratigraphic data are presented for a 20 m thick section spanning the Røsnæs Clay Formation at Albæk Hoved in Denmark. This early Eocene formation is the first calcareous deposit in the North Sea after a several million year period of non-calcareous sedimentation. Nannofossil and dinoflagellate data indicate that the section is unusually complete, spanning lower zone NP11 to lower NP13. Throughout the section, Subbotina spp. dominate the planktonic foraminiferal assemblages. Benthonic foraminiferal assemblages indicate middle bathyal water depths (600–1000 m). Water exchange between the semi-enclosed North Sea and the open ocean has been estimated by comparing the North Sea isotopic records with coeval records for DSDP Hole 550 in the northeastern Atlantic Ocean. Anomalously low δ18O values (−4 to −5‰) for bulk samples and planktonic deep-dwelling Subbotina from the Røsnæs Clay indicate a significant freshwater component in the North Sea. Average salinities in the euphotic zone ranged between 26 and 30 ppt throughout the early Eocene. The benthonic foraminiferal δ18O values indicate generally somewhat more saline and stable conditions in the water mass near the seafloor. During the early Eocene, three principal conditions alternated in the North Sea, depending on regional sea level, position of critical sills and the extent of water exchange with the open ocean. (1) At times of strongly restricted water exchange, calcite dissolution was complete. Grey clays formed and sediment oxygen content was low. Non-calcareous agglutinated foraminifera dominated. This condition prevailed in the earliest Eocene (NP10), during deposition of the lowermost Røsnæs Clay Formation, and at the end of the early Eocene. (2) At times of moderately restricted water exchange, calcite dissolution was important. Calcite content and planktonic/benthonic foraminiferal ratios in the sediment were low. Different grey or reddish brown clays formed. Oxygen content at the seafloor was low to intermediate. Subbotina δ18O values (−2 to −4‰) were generally a few per mil lower than in the coeval open ocean and fluctuated dramatically, due to freshwater admixture. Subbotina-benthonic Δδ13C gradients were high, because of low biological productivity and slow renewal of bottom water in connection with temporarily strongly density-stratified water masses. This condition prevailed during the later half of Biochron NP11, and possibly in latest NP12. (3) At times of more open water exchange, calcite-rich sediments dominated. Deep-dwelling planktonic foraminifera invaded the North Sea and planktonic/benthonic foraminifera ratios were high. Surface-thriving morozovellids, however, were absent, probably because of reduced surface salinities. Subbotina δ18O values (−2 to −3‰) indicate that a freshwater component was present at mid-depth, but salinities were higher and more stable than during more restricted water exchange. Subbotina-benthonic Δδ13C gradients were low, reflecting higher productivity and invigoration of bottom-water circulation. Water mass density stratification was less profound. Reddish brown marls dominated, and oxygen content in the sediment was moderately high. This condition prevailed during most of NP12 and probably during early NP11. High-resolution isotopic profiles over a 5 m thick interval in the upper NP12 part of the Røsnæs Clay Formation reveal that three distinct lithological ‘event beds’ are associated with profound short-term negative shifts (1–2‰) in δ13C and δ18O. The isotopic shifts are of the same magnitude in bottom waters as at mid-depth, implying that they reflect rapid changes in the chemistry of the entire water mass of the North Sea. The events may reflect short-term sea-level falls and/or rapid water mass exchange with other semi-enclosed basins to the north.

From shelf to abyss: Record of the Paleocene/Eocene-boundary in the Eastern Alps (Austria)

In the Eastern Alps (Austria) several marine successions, which were deposited ranging from shallow shelf to bathyal slope and abyssal basin, provide detailed records across the Paleocene/Eocene-boundary. These records indicate a two-step event starting with a prominent sea-level fall and followed by climatic changes. At the northern and southern shelves that fringed the Penninic Basin, the shallow-water sedimentary records are incomplete across the Paleocene/Eocene transition. Erosional surfaces indicate a major sea-level drop, which was terminated by an early Eocene (Ypresian) transgression within calcareous nannoplankton Zone NP12. As a proxy for the onset of this sea-level fall a strong increase in the terrestrially-derived input into the Penninic Basin can be used. The abyssal Anthering section from the northern part of the basin comprises a complete succession from NP9 to the upper part of NP10 (upper Thanetian-lower Ypresian). The thickest turbidite beds of this 250 m thick succession appear just before the carbon isotope event in the upper part of zone NP9, which is used to recognize the Paleocene/Eocene-boundary. A major lithological change from a sandstone-dominated facies to a claystone-dominated facies occurs at the onset of the carbon isotope event. This might be the result of a climatic change, resulting in increased intra-annual humidity gradients and increased physical erosion of the hinterland. Consequently, mainly fine-grained suspended material would have come into the basin and caused an increase in hemipelagic sedimentation rates by about a factor of 6. A similar value has been calculated for the bathyal Untersberg section, which was deposited on the southern slope of the basin, where an increased input of siliciclastic material is associated with a carbonate dissolution event during the carbon isotope event. At the southern shelf, a stratigraphic gap within the Gosau Group in the Krappfeld area (Carinthia) comprises the Maastrichtian and Paleocene. After a sea-level rise nummulitic marlstone and limestone were deposited in the lower part of zone NP12. Since the northern and southern shelves of the Penninic Basin belonged to different tectonic domains, with different potentials of crustal subsidence, the temporal similarity of sea-level changes on both shelves in the latest Paleocene and earliest Eocene suggests that these sea level fluctuations were mainly eustatic in origin.

Eocene dinoflagellate cyst biostratigraphy of research borehole 011-BP, Omsk Region, southwestern Siberia

A shallow marine Eocene section recovered in the cored borehole 011-BP, southwestern Siberia, was analyzed palynologically. Age-diagnostic dinoflagellate cyst events including the first occurrences of Charlesdowniea coleothrypta, Dracodinium politum, Ochetodinium romanum, Samlandia chlamydophora, Areosphaeridium diktyoplokum, Hystricho-sphaeropsis costae, Wetzeliella eocaenica and Duosphaeridium nudum are recognized at successive levels in the Upper Lulinvor Formation (498.0–459.0 m), indicating a Middle-latest Ypresian age. A hiatus spanning the Early Lutetian is present at an unconformity at 459.0 m which underlies sediments of the uppermost Lulinvor Formation (459.0–456.0 m), which are referred to the Middle Lutetian based on the presence of Costacysta bucina, Cordosphaeridium cantharellus and Wilsonidium echinosuturatum. The overlying interval from 456.0 m to 265.0 m (Tavda Formation) is referred to the latest Lutetian to Priabonian primarily based on a combination of published paleomagnetic signals and the presence of Rhombodinium draco, Membranosphaeridium aspinatum, Svalbardella sp., Thalassiphora fenestrata, Thalassiphora reticulata, Rhombodinium perforatum and Rhombodinium longimanum. According to the combined dinoflagellate cyst data and normal magnetic polarity in the uppermost part of the Tavda Formation, marine sedimentation was interrupted in southwestern Siberia during the Late Priabonian (∼34.8 Ma). The dinoflagellate cyst assemblages are illustrated, the new species Thalassiphora dominiquei is formally described and a neotype for Wetzeliella coronata (Vozzhennikova 1967) Lentin & Williams 1976 is designated. The morphology and taxonomy of several taxa are discussed.

The Anthering outcrop (Austria), a key-section for correlation between Tethys and northwestern Europe near the Paleocene/Eocene boundary

A section in the Rhenodanubian Flysch at Anthering, near Salzburg, Austria, records important dinoflagellate events which are also recognized in NW Europe, where they have proved to be reliable biostratigraphical tools in the Paleocene/Eocene boundary interval lacking calcareous microfossils. It is the first direct biostratigraphical correlation between NW Europe and the Tethys in this interval. The Austrian dinoflagellate record suggests that some dinoflagellate events near the Paleocene/Eocene boundary are probably widely recognizable. The calcareous nannofossils in the Anthering section enable a direct calibration between the dinoflagellate events and the standard calcareous nannofossil zonation (Egger et al. in press). In ascending order, the most important dinoflagellate events are: 1) A strong acme of Apectodinium spp. (exceeding 60% of the total dinoflagellate assemblage in some samples) in upper NP9, contrasting to percentages generally between 10 and 25 in the sections above and below. The acme coincides with a negative shift in δC interpreted to probably represent the global carbon isotopic excursion (CIE) (Egger et al. in press). 2) The regular occurrence of Apectodinium augustum approximately restricted to the same interval as the acme of the genus. 3) The first appearance of the genus Wetzeliella in the upper part of NP10. The genus is represented by two species: one is identical or close to the NW European species W. lobisca or W. lunaris. The other one is W. unicaudalis, which is more common. It has formerly been recorded in the North Atlantic Basque Basin (Caro 1973), but not in NW Europe. An interval with bentonite layers occurs between the LAD of A. augustum and FAD of Wetzeliella. The main ash phase of the North Sea Basin occurs in a similar position relative to the same dinoflagellate events. This first-order calibration between NW European dinoflagellate events and the standard nannofossil zonation provides independent evidence for the position of sections from the type areas of the Sparnacian and Ypresian stages in the global stratigraphical schemes. The occurrence of the calcareous nannofossil Tribrachiatus digitalis relative to the dinoflagellate events is similar at Anthering (Egger et al. in press) and in the basement bed of the London Clay (Berggren & Aubry 1998). The new data seem to confirm the bio-chronostratigraphical position of these sections as hitherto interpreted by most workers mainly on the basis of a combination of magnetostratigraphy, tephra-correlation, and absolute datings.

WILSONIDIUM PECHORICUM NEW SPECIES—A NEW DINOFLAGELLATE SPECIES WITH UNUSUAL ASYMMETRY FROM THE PALEOCENE/EOCENE TRANSITION

Abstract Fossil dinoflagellates, when asymmetrical, almost always have features such as antapical horns on the right side reduced relative to features on the left side. A new species here described, Wilsonidium pechoricum, is therefore unusual in having a reduced left antapical horn. W. pechoricum seems to have originated in the northern Tethys in the latest Paleocene. It subsequently spread northwards and became widely distributed in the Peri-Tethys and parts of the Arctic region during the short interval known as the Initial Eocene Thermal Maximum (IETM). The new species was probably favored by extraordinary paleoecological conditions (high sea-surface temperatures and probably also high nutrient levels) prevailing in neritic waters of the IETM; a time during which aberrant morphotypes were also recorded among other planktonic protists. The apparent absence of W. pechoricum from the North Atlantic region suggests that the Turgay Strait may have functioned as a waterway between the Arctic and Peri-Tethys during the IETM. W. pechoricum is the oldest species of the genus Wilsonidium and possibly descended from the genus Apectodinium. Its early appearance points to a Late Paleocene radiation of the Wetzelielloideae before the well-known Early Eocene radiation in the subfamily, and its morphology is in accordance with a monophyletic origin of the group.

The late Paleocene thermal maximum δ13C excursion in Denmark

Two sections with strata of the Paleocene–Eocene transition in Denmark have been studied for stable carbon isotopes in the particulate organic matter. 36 samples were analysed. The sections include the clay pits at Ølst/Hinge in eastern Jylland and the cored borehole DGI 83101 in Østerrenden, Store Bælt. The succession covers the upper part of the Holmehus Formation, the Østerrende Clay, the Glauconitic Silt and lower part of the Ølst Formation (Heilmann-Clausen et al. 1985; Nielsen et al. 1986). A strong negative shift of δC is recorded in the basal layers of the Ølst Formation. These basal beds (the Stolle Klint Clay of Heilmann-Clausen 1995) measure up to 14 m and consist of a finely laminated clay. The negative values, around –30‰, coincide with the lower part of dinoflagellate Zone 6 of HeilmannClausen (1985), which corresponds to the Aau Zone of Powell (1992). The zone is characterized by a strong acme of Apectodinium spp. This is the interval, in which the LPTM (late Paleocene thermal maximum) δC spike was biostratigraphically expected to occur on the basis of published information from the Forties Member of the North Sea (Beerling & Jolley 1998), the Sparnacian in the Paris Basin (Thiry & Dupuis 1998), and the Anthering section in Austria (Egger et al. in press). However, the excursion is 6–8‰ more negative than values below and above, and thus even stronger than the global LPTM spike of 3–4‰. Our study includes a quantification (based on light-microscopy, i.e., a palynofacies study) of the types of organic particles in the same samples as used for the carbon isotope analysis. The palynofacies analysis reveals that the interval with the δC values around –30‰ is characterized by a distinctive assemblage of organic particles, namely a high dominance of amorphous organic matter. The amorphous organic matter in the interval with the δC excursion generally amounts to 60-80% of the total organic particles. Amorphous matter is essentially absent below the excursion, and gradually decreases to values near 10% above. Amorphous organic matter of different Phanerozoic ages is well known from, especially, a study by Lewan (1986) to hold very negative δC values. The so-called l-amorphous kerogens of Lewan thus range between –26 and –35‰. The values in the Stolle Klint Clay fall in the middle of this range. According to Lewan (1986) the l-amorphous kerogens were formed in restricted, less than 200 m deep basins beneath stratified water. Such a basin is a most likely paleoenvironment for the Stolle Klint Clay. It may be concluded that a major δC spike is present in Denmark precisely at the level where the global LPTM spike is expected to occur. However, the very negative δC values in the sediment fall in the range which could be predicted for any ancient sediment of this type of paleoenvironment. The study documents the strong influence on δC values caused by variable amounts of different types of organic matter in sediments, and shows the need for a quantification of the various carbon sources when bulk sediment samples are used for isotopic studies. The results will be fully documented by HeilmannClausen & Schmitz (in prep.).