The Cretaceous/Paleogene boundary: Foraminifera, sea grasses, sea level change and sequence stratigraphy
Abstract The tsunami generated by the Chicxulub impact eroded the uppermost Cretaceous surface of the Gulf Coast region (U.S.A.) forming a distinctive topography that was previously interpreted as a sequence boundary. At more distal sites, such as Stevns Klint (Denmark), there appears to be no sequence boundary at the Cretaceous/Paleogene boundary but there is one within the uppermost Maastrichtian, between the Sigerslev and Hojerup members, and another in the lowermost Paleocene (top of Zone P1a). Both of these surfaces are identified by distinctive, phosphatized, and incipient hardgrounds. The changes in sea level involved in the generation of uppermost Cretaceous sequences are thought to have been minimal as, in the Gulpen and Maastricht formations of the Maastricht area (Netherlands), the presence of sea grasses and their associated foraminifera would indicate that the chalk sea floor remained within the range of water depth that would allow photosynthesis (