THE ESSENTIAL ROLE OF PLANKTONIC FORAMINIFERA FOR IMPROVING CRETACEOUS CHRONOSTRATIGRAPHY

Major advances in understanding the taxonomy and phylogeny of Cretaceous planktonic foraminifera have been derived through the past 45 years of deep-sea drilling and recent discoveries of extraordinarily well-preserved material from marginal-marine settings. These have resulted in a marked increase in the number of globally correlatable speciation and extinction events, many of which have been integrated with chemo- and magnetostratigraphic records. The greatest refinements to Cretaceous chronostratigraphy have been achieved for the Campanian and Maastrichtian intervals with development of well-calibrated age-depth curves from multiple deep-sea sites, restudy of foraminiferal ranges in the classic magnetostratigraphy section at Gubbio, Italy, and orbital tuning of high-resolution carbon isotope records from a number of important pelagic chalk sections. New bioevents integrated with chemostratigraphic data have been documented from studies of exceptionally well-preserved foraminiferal assemblages from Cenomanian-Santonian boreholes drilled in coastal Tanzania, late Aptian-early Albian and late Albian assemblages from deep-sea boreholes on Blake Plateau (North Atlantic) and Falkland Plateau (South Atlantic), and early Aptian and Santonian-Campanian boundary assemblages from Shatsky Rise (North Pacific). Revisions to the taxonomy of the Cretaceous planktonic foraminifera are primarily being led by participants of the Mesozoic Planktonic Foraminiferal Working Group (see http://portal.chronos.org/gridsphere/gridsphere?cid=res_taxondb). Multi-disciplinary efforts to improve Cretaceous chronostratigraphy are being coordinated through the EarthTime EU intiative (see http://earthtime-eu.eu/earthtime/). Results from these and other community-based scientific efforts will lead to vast improvements to the accuracy and resolution of the standard Cretaceous geological time scale.