A new biostratigraphic scheme for the Paleocene onshore West Greenland and its implications for the timing of the pre-volcanic evolution

Based upon dinoflagellate cyst and nannofossil data, a detailed zonation of the Lower Paleocene succession in the Nuussuaq Basin, onshore West Greenland has been established. The succession is divided into the five dinoflagellate cyst zones: Trithyrodinium evittii, Cerodinium pannuceum, Senegalinium iterlaaense, Palaeocystodinium bulliforme and Alisocysta margarita. The dinoflagellate cyst zones are correlated with nannoplankton zones. The stratigraphically most important nannofossils recorded include Chiasmolithus cf. bidens, Neochiastozygus modestus, N. perfectus, N. saepes, Prinsius martinii and Zeugrhabdotus sigmoides. A new zonal scheme has been erected and resolves previous problems relating biostratigraphic and ⁴⁰Ar/ ³⁹Ar data in the region. The Upper Maastrichtian-Lower Paleocene succession records faulting and valley/submarine canyon incision resulting from pre-volcanic rifting and regional uplift of the basin. Two Early Paleocene tectonic phases have been recognized during NP1-NP3. These uplift phases were followed by rapid subsidence during NP4. Initiation of volcanism onshore West Greenland is broadly concurrent with the Alisocysta margarita Zone indicating that volcanism began during late NP4, in accordance with recent palaeomagnetic results and ⁴⁰Ar/ ³⁹Ar dating of the volcanics. On the basis of the first occurrence datum of the dinoflagellate cyst species Cerodinium kangiliense and Alisocysta margarita, it is possible to correlate the lowermost volcanic Anaanaa Member hyaloclastites from the southwestern part of Nuussuaq with sediments of the Eqalulik Formation from the northern coast of Nuussuaq.