Stephen Louwye

Dinoflagellate cyst stratigraphy and palaeoecology of the Pliocene in northern Belgium, southern North Sea Basin

Dinoflagellate cysts and other palynomorphs from the Pliocene Kattendijk and Lillo formations, exposed in two temporary outcrops in northern Belgium, provide new information on the biostratigraphic position and sequence stratigraphic interpretation of these units. Dinoflagellate cysts from the Kattendijk Formation indicate an age between about 5.0 Ma and 4.7–4.4 Ma (early Early Pliocene) in our sections, confirming a correlation with standard sequence 3.4 and implying a slightly greater age than the Ramsholt Member of the Coralline Crag Formation of eastern England. The unconformity at the base of the Kattendijk Formation was not seen, but presumably correlates with sequence boundary Me2 at 5.73 Ma. The overlying Lillo Formation is late Early Pliocene or early Late Pliocene ( c . 4.2–2.6 Ma) in age, and the unconformity at its base may be correlated with sequence boundary Za2 at 4.04 Ma or Pia1 at 3.21 Ma. The Oorderen Sands and superjacent Kruisschans Sands members (Lillo Formation) are both part of the same depositional cycle. They were probably deposited before 2.74 Ma, and certainly before the onset of Northern Hemisphere cooling at c . 2.6 Ma. Evidence from dinoflagellate cysts indicates that both a shelly unit at the base of the Lillo Formation and the lower part of the overlying Oorderen Sands were deposited during a conspicuously cool climatic phase, with warmer temperatures returning during later deposition of the Oorderen Sands and Kruisschans Sands members. Many dinoflagellate cyst and acritarch species are reported here for the first time from the southern North Sea Basin. Selenopemphix conspicua (de Verteuil & Norris, 1992) stat. nov. is proposed.

Northern Hemisphere Glaciation during the Globally Warm Early Late Pliocene

The early Late Pliocene (3.6 to ∼3.0 million years ago) is the last extended interval in Earths history when atmospheric CO2 concentrations were comparable to todays and global climate was warmer. Yet a severe global glaciation during marine isotope stage (MIS) M2 interrupted this phase of global warmth ∼3.30 million years ago, and is seen as a premature attempt of the climate system to establish an ice-age world. Here we propose a conceptual model for the glaciation and deglaciation of MIS M2 based on geochemical and palynological records from five marine sediment cores along a Caribbean to eastern North Atlantic transect. Our records show that increased Pacific-to-Atlantic flow via the Central American Seaway weakened the North Atlantic Current and attendant northward heat transport prior to MIS M2. The consequent cooling of the northern high latitude oceans permitted expansion of the continental ice sheets during MIS M2, despite near-modern atmospheric CO2 concentrations. Sea level drop during this glaciation halted the inflow of Pacific water to the Atlantic via the Central American Seaway, allowing the build-up of a Caribbean Warm Pool. Once this warm pool was large enough, the Gulf Stream–North Atlantic Current system was reinvigorated, leading to significant northward heat transport that terminated the glaciation. Before and after MIS M2, heat transport via the North Atlantic Current was crucial in maintaining warm climates comparable to those predicted for the end of this century.

Shallow marine Lower and Middle Miocene deposits at the southern margin of the North Sea Basin (northern Belgium): dinoflagellate cyst biostratigraphy and depositional history

Detailed dinoflagellate cyst analysis of the Lower–Middle Miocene Berchem Formation at the southernmost margin of the North Sea Basin (northern Belgium) allowed a precise biostratigraphical positioning and a reconstruction of the depositional history. The two lower members of the formation (Edegem Sands and decalcified Kiel Sands) are biostratigraphically regarded as one unit since no significant break within the dinocyst assemblages is observed. The base of this late (or latest) Aquitanian–Burdigalian unit coincides with sequence boundary Aq3/Bur1 as defined by Hardenbol and others, in work published in 1998. A hiatus at the Lower–Middle Miocene transition separates the upper member (the Antwerpen Sands) from the underlying member. The greater part of the Antwerpen Sands were deposited in a Langhian (latest Burdigalian?)–middle Serravallian interval. The base of this unit coincides with sequence boundary Bur5/Lan1. Biostratigraphical correlation points to a diachronous post-depositional decalcification within the formation since parts of the decalcified Kiel Sands can be correlated with parts of the calcareous fossil-bearing section, up to now interpreted as Antwerpen Sands. The dinoflagellate cyst assemblages are dominated by species with a inner neritic preference, although higher numbers of oceanic taxa in the upper part of the formation indicate incursions of oceanic watermasses into the confined depositional environment of the southern North Sea Basin.

Pliocene dinoflagellate cyst stratigraphy, palaeoecology and sequence stratigraphy of the Tunnel-Canal Dock, Belgium

Dinoflagellate cysts and sequence stratigraphy are used to date accurately the Tunnel-Canal Dock section, which contains the most complete record of marine Pliocene deposits in the Antwerp harbour area. The Zanclean Kattendijk Formation was deposited between 5.0 and 4.4 Ma during warm-temperate conditions on a shelf influenced by open-marine waters. The overlying Lillo Formation is divided into four members. The lowest is the Luchtbal Sands Member, estimated to have been deposited between 3.71 and 3.21 Ma, under cooler conditions but with an open-water influence. The Oorderen Sands, Kruisschans Sands and Merksem Sands members of the Lillo Formation are considered a single depositional sequence, and biostratigraphically dated between 3.71 and c . 2.6 Ma, with the Oorderen Sands Member no younger than 2.72–2.74 Ma. Warm-temperate conditions had returned, but a cooling event is noted within the Oorderen Sands Member. Shoaling of the depositional environment is also evidenced, with the transgressive Oorderen Sands Member passing upwards into (near-)coastal high-stand deposits of the Kruisschans Sands and Merksem Sands members, as accommodation space decreased. Applying sequence stratigraphy to our section implies that the Kattendijk/Lillo Formation boundary corresponds to the sequence boundary (SB) Za2 (4.04 Ma), the Luchtbal/Oorderen sands boundary to SB Pia1 (3.21 Ma), and the top of the Merksem Sands to SB Pia2 (2.76 Ma). Finally, the Belgian deposits are compared with marine Pliocene deposits of eastern England.

The Upper Miocene of the southern North Sea Basin (northern Belgium): a palaeoenvironmental and stratigraphical reconstruction using dinoflagellate cysts

Organic-walled palynomorph assemblages from the Kasterlee Formation in northern Belgium provide new insights into the Late Miocene depositional history and palaeoenvironments of the southernmost North Sea Basin. Ranges of key dinoflagellate cysts constrain the unit between 7.5 and 5.32 Ma, that is, a latest Tortonian to Messinian age. The palynomorph assemblage is characterized, amongst others, by Geonettia clineae , an opportunistic species that thrives in mesotrophic, coastal embayments with a low sediment influx. This environmental setting is corroborated by the notable presence of Gramocysta verricula , a species with preference for shallow marine environments. The occurrence of species of the fresh water green alga Pediastrum indicates manifest river discharge in a near-shore environment or embayment. The coastal depositional environment mirrored by the palynomorphs of the Kasterlee Formation succeeds the distinct transgressive and fully marine environments of the underlying Diest Formation in the Campine area. The results from the palynological study, combined with lithological and geophysical data, show that both Upper Miocene formations are two distinct depositional cycles separated by an erosional or regressive phase. The upper boundary of the Kasterlee Formation is correlated with the Me2 sequence boundary at 5.73 Ma. The Kasterlee Formation is herein formally moved from the Lower Pliocene series to the Upper Miocene series. The coastal environment, probably characterized by a shoaling phase, recorded at the border of the southern North Sea Basin, matches the global record of regressive phases in Messinian sedimentary sequences, which are linked to cooling and increasing global ice volume.

NEW DINOFLAGELLATE CYST AND INCERTAE SEDIS TAXA FROM THE PLIOCENE OF NORTHERN BELGIUM, SOUTHERN NORTH SEA BASIN

Abstract New dinoflagellate cyst taxa have been recovered from Pliocene deposits in the Antwerp area of Belgium, where a detailed analysis of the Kattendijk and Lillo formations has yielded a diverse dinoflagellate record for the southern margin of the North Sea Basin. Four new species and two new genera of dinoflagellate cysts are recognized: the gonyaulacaceans Spiniferites coniconcavus n. sp. and Pyxidinopsis braboi n. sp., the goniodomacean Desotodinium wrennii n. gen. and sp., and the protoperidiniacean Scaldecysta doelensis n. gen. and sp. The protoperidiniacean genus Barssidinium Lentin, Fensome, and Williams, 1994 has been emended from new observations on the tabulation of Barssidinium pliocenicum (Head, 1993) Head, 1994a emend. The excellent preservation of the Belgian material accounts for these new observations. Barssidinium wrennii Lentin, Fensome, and Williams, 1994 is considered a taxonomic junior synonym of Barssidinium pliocenicum (Head, 1993) Head, 1994a, which thus becomes the correct name for the type of the genus. The new marine incertae sedis palynomorph Waaslandia geminifera n. gen. and sp. is also proposed.

Holocene salinity changes in the southwestern black sea: A reconstruction based on dinoflagellate cysts

Abstract Dinoflagellate cysts were used as a proxy for reconstructing the salinity variations during the Holocene in the southwestern Black Sea. The aim of this study was to determine the timing of the reconnection between the Black and Marmara seas. Core GeoB 7625-2, located 50 km northeast of the mouth of the Sakarya River, was sampled with a 200-year resolution between 7.42 and 0.52 ka BP. The lower part of the core was sampled with varying resolution. A distinct change in the dinoflagellate cyst assemblages from freshwater/brackish water to saltwater was observed between ∼ 8.25 and ∼ 7.97 ka BP, which is ∼ 0.6 ka earlier than observed in other dinoflagellate cyst studies. This discrepancy may indicate the diachronous salinification of the Black Sea. The freshwater to brackish water assemblage is dominated by Pyxidinopsis psilata and Spiniferites cruciformis, while the most important euryhaline species are Lingulodinium machaerophorum and cysts of Pentapharsodinium dalei. The average process length of Lingulodinium machaerophorum was used as a salinity proxy. Both proxies suggest a gradual reconnection between the Black and Marmara seas, and these findings confirm earlier studies. Peridinium ponticum is restricted to the Black Sea; abundance fluctuations of this species were controlled by salinity variations and changes in nutrient concentrations. Earlier studies have demonstrated that the 800 to 500 year cycles observed in the sedimentary record are related to the intensity of the discharge of the Sakarya River, and linked to the North Atlantic Oscillations. Cysts of Pentapharsodinium dalei and Spiniferites spp. fluctuated synchronously with the clay layer frequency. The poor preservation of these forms may indicate shelfal transport during periods of intense river discharge. The variation in relative abundance of heterotrophic species does not correlate with the clay layer frequency, since upwelling and nutrient supply also influenced their abundances. Lingulodinium machaerophorum shows the highest relative abundances during periods with reduced river input.

Integrated stratigraphy and palaeoecology of the Lower and Middle Miocene of the Porcupine Basin

A high-resolution palynological analysis and a detailed palaeomagnetic study of a marine sequence recovered during IODP Expedition Leg 307 in the Porcupine Basin southwest of Ireland provide new insights into the regional depositional history and palaeoenvironmental evolution during Early Neogene times. The Hole 1318B studied was drilled on the upper slope of the continental margin in a water depth of 409 m, upslope from a province of carbonate mounds (the Belgica mound province). The diverse and well-preserved dinoflagellate cyst associations consist typically of deep neritic and oceanic species, mixed with a neritic component transported from the shelf, reflecting the deep depositional setting at the continental margin. The palaeomagnetic record together with the ranges of key dinoflagellate cyst species constrain the age of the studied sequence between 16.7 Ma and 12.01 Ma, that is, between the late Burdigalian and late Serravallian. The distinct unconformity terminating the Miocene sequence correlates to the global sequence boundary Ser4/Tor1 dated at 10.5 Ma, and represents, according to previous extensive seismic studies, a basin-wide erosional event. The overlying sediments are of Middle Pleistocene or younger age. Downslope from IODP Site 1318, carbonate mounds root on the erosional surface. The dinoflagellate cyst associations from the Porcupine Basin distinctly mirror the global cooling phase following the Middle Miocene Climatic Optimum. Cooling phase Mi3, a short-lived glaciation, is particularly well expressed and here dated at 13.6 Ma. The palynomorph record furthermore indicates a reduction of the productivity and an increase of oceanic oligotrophic species after 14 Ma, suggesting a reduction or perhaps even a shutdown of the upwelling.

ARCHAEOZIPHIUS MICROGLENOIDEUS, A NEW PRIMITIVE BEAKED WHALE (MAMMALIA, CETACEA, ODONTOCETI) FROM THE MIDDLE MIOCENE OF BELGIUM

Abstract Three partial skulls of odontocetes from the Miocene of Antwerp and Kessel, northern Belgium (southern North Sea Basin) are described here as a new genus and species of beaked whale (Ziphiidae), Archaeoziphius microglenoideus. This small new whale is one of the most archaic beaked whales, because of its low vertex, thin and laterally directed premaxillary crests, low contact between the supraoccipital and the frontals on the vertex, and its free atlas. It is also characterized by the strong transverse compression of the frontals on the vertex and a reduced glenoid surface on the squamosal; the two last characters might be considered as derived. Nasals wider than the frontals on the vertex might group A. microglenoideus with the extant larger genera Berardius and Tasmacetus; the nodular frontals and the premaxillary crests are more similar to the condition in Berardius. A sediment sample from the cetacean-bearing strata at Kessel is dated with dinoflagellate cysts as middle Miocene, tentatively late Langhian to early Serravallian, i.e., from ca. 15 Ma to ca. 13.2 Ma. Archaeoziphius microglenoideus is therefore the oldest reported beaked whale known by cranial material.

The Miocene–Pliocene hiatus in the southern North Sea Basin (northern Belgium) revealed by dinoflagellate cysts

A palynological analysis with marine palynomorphs (dinoflagellate cysts, acritarchs, green algae) and terrestrial palynomorphs (pollen and spores) of the Kasterlee and Poederlee formations provides new insights in the depositional history at the southern border of the North Sea basin (northern Belgium) around the Miocene-Pliocene transition. Dinoflagellate cyst stratigraphy constrains the age of the Kasterlee Formation in the Oud-Turnhout borehole between 7.5 and 5.32 Ma. The upper boundary of the formation can be correlated with sequence boundary Me2 at 5.73 Ma of Hardenbol and co-workers, which further constrains its age to the time interval 7.5-5.73 Ma. The palynomorph assemblages reflect a near-coast depositional environment. Where present, the Kasterlee Formation thus terminates the Miocene series in northern Belgium. The overall shallow nature of the latest Miocene deposits is related to a sea-level lowering caused by the onset of globally cooling conditions. For the first time, palynology is applied to estimate the age of the Poederlee Formation, suggesting it was deposited during the Mid-Pliocene warm period. Dinoflagellate cysts and sequence stratigraphy together constrain the age of the unit between 3.21 and 2.76 Ma, and possibly even between 3.21 and 3.15 Ma. The Poederlee Formation was deposited in neritic environments, which shoaled in the upper part of the unit as a consequence of the decreasing availability of accommodation space. We demonstrate that the magnitude of the hiatus between the Miocene and Pliocene series varies strongly at the southern boundary of the North Sea Basin, and lasts in the Antwerp area c. 3.2 million years and c. 2.52 million years in the Campine area.