The Late Triassic period is characterized by a series of major faunal and floral turnovers, which culminate in the end-Triassic mass extinction. This final collapse of the biosphere has been linked to the Central Magmatic Province. The preceding bio-events are of similar amplitude but less constrained. It has been suggested that the Carnian pluvial event is caused by the major flood basalt volcanism of the Wrangellia LIP. However, Carnian palaeoclimatic proxy records are scattered and mainly confined to the western Tethys realm. In this contribution we present preliminary palynological data from the Boreal realm. Early Carnian pollen and spore assemblages from Spitsbergen show pronounced quantitative changes in vegetation composition. Several warming pulses and a general trend to a more humid climate characterize the palaeoclimate inferred from principal component analysis of the palynological data. The observed warming events likely correlate with Wrangellia LIP and the Rheingraben event in the Tethys realm, but need further confirmation by additional data.
New data from an integrated palynological (pollen/spores, dinoflagellate cysts, acritarchs), (micro)paleontological (ammonoids, bivalves, conodonts, radiolarians) and magnetostratigraphic study of a 50 m thick Sevatian-Rhaetian transition in the Zlambach Formation (Kleiner Zlambachgraben section near Hallstatt, Austria) are presented. This well exposed Western Tethys key section of alternating deeper water limestones and marls shows successive FO and LO events in the marine faunal and phytoplankton record, as well as in the coeval terrestrial pollen/spore record. Pollen/spore assemblages are dominated by the Classopollis group. However, two distinct palynological zones can be recognized: early Rhaetian assemblages still include a variety of typical Late Triassic elements (Enzonalasporites, Vallasporites, Patinasporites, Ellipsovelatisporites, Partitisporites, Triadispora), whereas middle Rhaetian assemblages show the presence of new elements, such as Chasmatosporites, Quadraeculina, Limbosporites. Dinoflagellate cysts (Rhaetogonyaulax, Suessia, Dapcodinium), are abundant in the higher part of the studied section. Intriguingly, the transition between the two zones is characterized by an acme of dinoflagellate cysts (Rhaetogonyaulax, Noricysta, Heibergella). These events in the palynological record coincide approximately with the FO of characteristic Late Triassic ammonoids (Choristoceras, Cochloceras). The regional and global significance of the nature and magnitude of this event is discussed.
The modern polar cryosphere reflects an extreme climate state with profound temperature gradients towards high-latitudes. It developed in association with stepwise Cenozoic cooling, beginning with ephemeral glaciations and the appearance of sea ice in the late middle Eocene. The polar ocean gateways played a pivotal role in changing the polar and global climate, along with declining greenhouse gas levels. The opening of the Drake Passage finalized the oceanographic isolation of Antarctica, some 40 Ma ago. The Arctic Ocean was an isolated basin until the early Miocene when rifting and subsequent sea-floor spreading started between Greenland and Svalbard, initiating the opening of the Fram Strait / Arctic-Atlantic Gateway (AAG). Although this gateway is known to be important in Earth’s past and modern climate, little is known about its Cenozoic development. However, the opening history and AAG’s consecutive widening and deepening must have had a strong impact on circulation and water mass exchange between the Arctic Ocean and the North Atlantic. To study the AAG’s complete history, ocean drilling at two primary sites and one alternate site located between 73°N and 78°N in the Boreas Basin and along the East Greenland continental margin are proposed. These sites will provide unprecedented sedimentary records that will unveil (1) the history of shallow-water exchange between the Arctic Ocean and the North Atlantic, and (2) the development of the AAG to a deep-water connection and its influence on the global climate system. The specific overarching goals of our proposal are to study: (1) the influence of distinct tectonic events in the development of the AAG and the formation of deep water passage on the North Atlantic and Arctic paleoceanography, and (2) the role of the AAG in the climate transition from the Paleogene greenhouse to the Neogene icehouse for the long-term (~50 Ma) climate history of the northern North Atlantic.
Getting a continuous record of the Cenozoic sedimentary succession that recorded the evolution of the Arctic-North Atlantic horizontal and vertical motions, and land and water connections will also help better understanding the post-breakup evolution of the NE Atlantic conjugate margins and associated sedimentary basins.
