DISTRIBUTION OF DINOCYSTS IN THE SURFACE SEDIMENTS OF SIDI MOUSSA LAGOON : (ATLANTIC COAST-MOROCCO)

The Sidi Moussa lagoon, (32°52′0″ N / 8° 51′05″ W) is located on the Moroccan Atlantic coast between the cities of El Jadida and Safi about 15 km South of the Jorf Lasfar industrial complex, The climate of the lagoon is classified as hot temperate. It is characterised by an oceanic influence. This study of dinoflagellate cyst mapping is the first of its kind from the Sidi Moussa lagoon. the objectives of the present survey were (i) to evaluate to the spatial variation of dinoflagellate cyst assemblages in the sediment along the Sidi Moussa lagoon (ii) to assess the densities of its cysts (iii) to compare the cyst assemblages in this study with that of other sites. The data were collected in a scientific campaign by zodiac carried out from in April 2018 by core following a sampling network of 21 stations distributed randomly in the study area. The surface layer of the sediment cores (3 cm) was sliced and kept at 4° C until analysis. The highest total cyst abundance was 194 cysts. g−1 dry sediment. The Pearson statistical test revealed a positive and significant correlation between cyst abundance and water content, organic matter and of fine sediment. Our study showed the presence of morphotypes of potentially toxic species. The cysts of these species present in the sediment of the Sidi Moussa lagoon could germinate, when environmental conditions become favorable, and in turn could inoculate the water column with the subsequent bloom formation. This study confirms the usefulness of cyst analysis in the assessment of harmful bloom risk in this area important for oyster’s culture.

Dinoflagellate cysts from the Pannonian (late Miocene) "white marls" in Pécs-Danitzpuszta, southern Hungary

Dinoflagellate-cyst based biostratigraphy is an important tool in the stratigraphical subdivision and correlation of the Neogene Lake Pannon deposits. A total of 66 palynological samples were investigated from the Pannonian (upper Miocene) marl succession exposed in the Pécs-Danitzpuszta sand pit in order to evaluate the biostratigraphical assignment and constrain the age of the strata. Earlier attempts to recover dinoflagellate cysts from this important reference section had failed. In our material, six samples contained well-preserved palynomorphs. One sample from the lower part of the succession (D25) contained a probably reworked middle Miocene assemblage. Samples from the middle segment of the succession (D3, D2, D1) indicate the Pontiadinium pecsvaradensis Zone (ca. 10.8 to 10.6 Ma). Samples from the top of the marl (D219, D221) did not give additional stratigraphic information (P. pecsvaradensis Zone or younger). The palynofacies of samples D3 to D221 indicates a relatively distal, calm, occasionally oxygen-deficient, probably deep depositional environment.

Reconstruction of the last cretaceous anoxic event in the Tarfaya Laayoune basin (South of Morocco): Biostratigraphy and Paleoenvironment of the Oum Debaa Formation

The Tarfaya-Laayoune coastal basin developed in a stable passive margin, where sedimentation occurred in shallow bays. During the Late Cretaceous, bituminous and phosphatic series were deposited in the shallow depression such as Sebkha Oum Debaa. In this work, the age of these Cretaceous layers are refined using a palynological approach and their paleoenvironments are described using organic geochemistry. Based on quantitative and qualitative palynological analyses, the sediments revealed a rich and diverse dinoflagellate cyst assemblage (65 taxa); among them 9 important biostratigraphic markers: Andalusiella inflata, Andalusiella ivoirensis, Andalusiella mauthei, Cerodinium diebelii, Cerodinium speciosum, Dinogymnium acuminatum, Odontochitina porifera, Trichodinium castanea, and Trithyrodinium evittii. According to the reported stratigraphic dinoflagellate taxa distribution, an age range of late Campanian to early Maastrichtian is herein proposed for the Oum Debaa Formation. This biostratigraphy update has been correlated to the Tethyan and Sub-Boreal domains. On the paleoenvironmental level, geochemical proxies have displayed an anoxic lagoon depositional which is dominated by an intermediate climate between hot / humid and arid with an often low paleoproductivity regime which induces redox conditions.

Out of the Blue and into the Black: Preparation, Mounting, and Image Rendering of Complex, Chorate Dinoflagellate Cysts for Scanning Electron Microscopy

We describe an experimental approach for achieving an optimal black background for scanning electron photomicrographs of small samples with elaborate and intricate structures. Specimens of the highly ornate, 66-million-year-old chorate dinoflagellate cyst species Cannosphaeropsis franciscana were selected as the subject of this study. Photomicrographs collected following standard aluminum stub surface placement were compared to those taken of specimens mounted using a novel pin-and-pedestal method. This simplistic mounting technique minimizes the need for post-production image editing and extraneous background removal.

New insights on the Late Paleocene-Early Eocene Dinoflagellate cyst zonation for the Paris and Dieppe Basins

The Anglo-Belgo-Paris Basin, historical cradle of the Paleogene stratigraphy since the XVIIIth century, is known by the presence of very specific so-called “Sparnacian” deposits (very diverse and laterally highly variable, predominantly lagoonal to terrestrial facies), which encompass the short stratigraphic interval of the Paleocene-Eocene Thermal Maximum (PETM). Due to the insufficient paleontological record, the “Sparnacian” succession of the Paris and Dieppe-Hampshire Basins still needs a robust chronostratigraphic correlation with other Paleogene records worldwide. In order to refine the stratigraphy of the Thanetian-Lower Ypresian succession in northern France a number of cores and outcrop sections have been investigated palynologically. As a result, an updated version of the Dinoflagellate cyst zonation for the Paris and Dieppe Basins is proposed and contains six new or revised Biozones for this stratigraphical interval: Alisocysta margarita, Apectodinium hyperacanthum, Apectodinium-extreme acme, Biconidinium longissimum-acme, Dracodinium astra, and Axiodinium lunare/Stenodinium meckelfeldense. Based on combined bio-, litho- and chemostratigraphic data, it appears that the dinocyst assemblages, corresponding to the PETM event interval (“Sparnacian” deposits, Soissonnais and upper Mortemer Formations with the most negative 13δCorg values between -27 and -32 ‰ PDB), are characterized by an extreme acme of Apectodinium spp. (70-98%) in both basins, sometimes alternating with an extreme acme of a few gonyaulacoid groups in the Dieppe Basin. Dinocyst assemblages from the PETM interval contain a significant number of atypical, longer specimens of Apectodinium parvum, which could represent an ecological onshore substitute of species Axiodinium augustum in the Paris and Dieppe-Hampshire Basins. The establishment of a new Biconidinium longissimum-acme Zone suggests the absence of an important stratigraphical hiatus previously inferred for the Paris Basin.

Paleoceanography and dinoflagellate cyst stratigraphy across the Lower–Middle Pleistocene Subseries (Calabrian–Chibanian Stage) boundary at the Chiba composite section, Japan

A dinoflagellate cyst record from the highly resolved Chiba composite section in Japan has been used to reconstruct sea-surface paleoceanographic changes across the Lower–Middle Pleistocene Subseries (Calabrian–Chibanian Stage) boundary at the global stratotype, constituting the first detailed study of this microfossil group from the Pleistocene of the Japanese Pacific margin. Cold, subarctic water masses from 794.2 ka gave way to warming and rapid retreat of the Subpolar Front at 789.3 ka, ~ 2000 years before the end of Marine Isotope Stage (MIS) 20. Throughout the fully interglacial conditions of MIS 19c, assemblages are consistent with warm sea surface temperatures but also reveal instability and latitudinal shifts in the Kuroshio Extension system. The abrupt dominance of Protoceratium reticulatum cysts between 772.9 and 770.4 ka (MIS 19b) registers the influence of cooler, mixed, nutrient-rich waters of the Kuroshio–Oyashio Interfrontal Zone resulting from a southward shift of the Kuroshio Extension. Its onset at 772.9 ka serves as a local ecostratigraphic marker for the Chibanian Stage Global Boundary Stratotype Section and Point (GSSP) which occurs just 1.15 m (= 1300 years) below it. An interval from 770.1 ka to the top of the examined succession at 765.8 ka (MIS 19a) represents warm, presumably stratified but still nutrient-elevated surface waters, indicating a northward shift of the Kuroshio Extension ~ 5 kyrs after the termination of full interglacial conditions on land.