| Titre | The Bajocian (Middle Jurassic): a key interval in the early Mesozoic phytoplankton radiation |
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| Auteur | Wiggan, N J; Riding, J B; Fensome, R A; Mattioli, E |
| Source | Earth-Science Reviews vol. 180, 2018 p. 126-146, https://doi.org/10.1016/j.earscirev.2018.03.009  Accès ouvert |
| Image |  |
| Année | 2018 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20170383 |
| Éditeur | Elsevier BV |
| Document | publication en série |
| Lang. | anglais |
| DOI | https://doi.org/10.1016/j.earscirev.2018.03.009 |
| Media | papier; en ligne; numérique |
| Formats | pdf; html |
| Province | Canada; Colombie-Britannique; Alberta; Saskatchewan; Manitoba; Ontario; Québec; Nouveau-Brunswick; Nouvelle-Écosse; Île-du-Prince-Édouard; Terre-Neuve-et-Labrador; Territoires du Nord-Ouest; Yukon;
Nunavut; Canada |
| SNRC | 1; 2; 3; 10; 11; 12; 13; 14; 15; 16; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34; 35; 36; 37; 38; 39; 40; 41; 42; 43; 44; 45; 46; 47; 48; 49; 52; 53; 54; 55; 56; 57; 58; 59; 62; 63; 64; 65;
66; 67; 68; 69; 72; 73; 74; 75; 76; 77; 78; 79; 82; 83; 84; 85; 86; 87; 88; 89; 92; 93; 94; 95; 96; 97; 98; 99; 102; 103; 104; 105; 106; 107; 114O; 114P; 115; 116; 117; 120; 340; 560 |
| Région | Monde |
| Lat/Long OENS | -180.0000 180.0000 90.0000 -90.0000 |
| Sujets | Jurassique moyen; Bajocien; Bathonien; micropaléontologie; microfossiles; macrofossiles; distribution géographique des fossiles; profils de dispersion; évolution; paléoécologie; paléogéographie;
paléoclimatologie; niveaux paléomers; paléoenvironnement; Dinoflagellés; paléontologie; Phanérozoïque; Mésozoïque; Jurassique |
| Illustrations | diagrammes biostratigraphiques; graphiques; croquis; coupes lithologiques; cartes géolscientiques généralisées; graphique à barres; photomicrographies; cartes géochronologiques |
| Programme | GEM2 : La géocartographie de l'énergie et des minéraux Bassin de Sverdrup de l'ouest de l'Arctique |
| Diffusé | 2018 03 22 |
| Résumé | (disponible en anglais seulement)
Dinoflagellates and coccolithophores are two of the most important groups of phytoplankton in the modern oceans. These groups originated in the Triassic and
radiated through the early Mesozoic, rising to ecological prominence. Within this long-term radiation, important short-term intervals of evolutionary and ecological change can be recognised. The Bajocian (Middle Jurassic, ~170-168 Ma) was
characterised by an important ecological transition within the coccolithophores, and the radiation of one of the principal families of cyst-forming dinoflagellates, the Gonyaulacaceae. During the Early Bajocian, the coccolith genus Watznaueria
diversified and expanded ecologically to dominate coccolith floras, a situation which continued for the remainder of the Mesozoic. This pattern was paralleled within dinoflagellate cyst floras by the ecological dominance of the genus Dissiliodinium
in the mid-palaeolatitudes. These phenomena appear to be linked to a positive carbon isotope shift, and an interval of enhanced productivity driven by a shift to a more humid climate, enhanced continental weathering and nutrient flux, or by changes
in ocean circulation and upwelling. The latest Early Bajocian to earliest Bathonian was then characterised by the rapid increase in diversity of dinoflagellate cysts within the family Gonyaulacaceae. Through this interval, the Gonyaulacaceae
transitioned from being a relatively minor component of dinoflagellate cyst floras, to becoming one of the prominent groups of cyst-forming dinoflagellates, which has persisted to the Holocene. In Europe, the pattern of this radiation was strongly
influenced by sea level, with the increase in gonyaulacacean diversity reflecting a major second-order transgression. On a finer scale, the main pulses of first appearances correlate with third-order transgressive episodes. A rise in sea level,
coupled with changes in the tectonic configuration of ocean gateways, appears to have controlled the pattern of plankton diversification in Europe. These palaeoceanographic changes may have enhanced water-mass transfer between Europe, the northwest
Tethys Ocean and the Hispanic Corridor, which promoted the floral interchange of dinoflagellates. Whilst sea-level rise and associated large-scale palaeoenvironmental shifts appear to have controlled the pattern of dinoflagellate cyst appearances in
several regions outside Europe, there is no direct correlation between dinoflagellate cyst diversity and sea-level rise on a global scale. Although the Bajocian was transgressive in several regions, widespread flooded continental area was also
present throughout the preceding Aalenian, an interval of low gonyaulacacean diversity. Moreover, although the Middle Jurassic was an interval of major climatic cooling, there was a ~5 myr gap between the onset of cooling and the radiation of
gonyaulacaceans during the Bajocian. The Bajocian was, however, marked by a major evolutionary radiation in the pelagic realm, including ammonites, giant suspension feeding fishes and planktonic foraminifera. These phenomena may indicate an
underlying ecological driver to the radiation of dinoflagellates during the Bajocian evolutionary explosion which could represent an extension of the Mesozoic Marine Revolution. |
| Sommaire | (Résumé en langage clair et simple, non publié)
La plus grande extinction a eu lieu il y a 250 millions d'années. Les taxons restés sont devenus les ancêtres des organismes modernes, et ont
déterminé le modèle d'évolution pour les 100 millions d'années à venir. Le réseau trophique marin a été largement réinventé, avec l'apparition de nouveaux groupes tels que les dinoflagellés et les coccolithophores. Les deux groupes ont laissé
suffisamment de fossiles (comme les kystes de dinoflagellés et les coccolithes) pour permettre l'étude des détails de leurs voies évolutives dans le Trias au Jurassique moyen. Des développements majeurs dans ces groupes ont eu lieu au stade bajocien
du Jurassique moyen, contemporains de changements climatiques, marins, tectoniques et écologiques significatifs. Dans cet article, nous suggérons que le changement des voies maritimes et des bassins océaniques pourrait avoir favorisé des changements
dans la dynamique du changement alimentaire qui sont responsables des changements que nous observons dans les enregistrements fossiles de dinoflagellés et de coccolithophores dans le Bajocien. L'ouest de l'Arctique contient des sédiments bajociens
qui restent mal étudiés, et donc un domaine d'étude potentiel pour la comparaison des tendances observées dans cet article. |
| GEOSCAN ID | 308074 |
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