Universidade Nova de Lisboa - Faculdade de Ciências e Tecnologia
Ciências da Terra vol:18 pages:23-28
The warming trend that started in the latest Paleocene and culminated in the Early Eocene Climatic Optimum (EECO)
between 52 and 50 Ma is punctuated by short-lived hyperthermals, like the Paleocene Eocene Thermal Maximum (PETM)that marks the base of the Eocene. Such short-lived hyperthermals are linked to global carbon cycle perturbations and associated with major floral and faunal changes. Orbital pacing is probably triggering these hyperthermal perturbations. After the EECO a cooling trend sets in only interrupted by a short Middle Eocene Climatic Optimum (MECO) in the beginning of the Bartonian; at the beginning of the Oligocene the cooling trend is leading to the start of the present ice-house state with the
growth of the first large Antarctic ice sheets.
The Paleogene timescale is based on the seafloor magnetic field reversals in combination with radio-isotopically or
astronomically dated control points. The GTS2012 used astronomically derived ages in the intervals 66-53 and 37-23Ma and a radio-isotopical age model in the interval between 53 and 37 Ma. It is expected that it will become possible in the future to extend the astrochronological scale to the entire Paleogene.
The stage GSSP’s of Danian (El Kef, Tunesia), Selandian and Thanetian (Itzurun Beach, Zumaia, Basque County, Spain),
Ypresian (Dababiya section, Luxor, Egypt) , Lutetian (Gorrondatxe cliff, Basque County, Spain) and Rupelian ( Massignano section, Ancona, Italy) have already been defined. For defining the Priabonian and the Chattian GSSP’s, suitable sections are to be discussed respectively the Alano di Piave section in the Venetian southern Alps and the Monte Cagnero section in the northeastern Apennines of Umbria-Marche in Italy. The Bartonian, historically referring to marine clays and sands in coastal sections of the Hampshire basin in England, is still lacking a suitable GSSP section; in GTS2004 and 2012 its base is provisionally kept at the C19n/C18r magnetic reversal. Potential Bartonian GSSP sections will be discussed.