Conference:
IX Congress of RCMNS, 27-30 September 2000, Fes , Morocco.
Author:
Speranta-Maria Popescu.
Abstract:
High-resolution pollen analysis has been performed on the Lupoaia section, which runs from lignite V to lignite XIII (thickness: 123m) of the Motru area. More than 200 samples have been analyzed, that means a sample by 5à cm on average (the sandy layers of the section excepted). The Motru area belongs to a Zanclean paleo-delta, which was build by a tributary of the paleo-Danube (Clauzon et Suc, unpublished). Paleomagnetic measurements have been successively realized by Radan & Radan (1986) and van Vught (2000). These measurements are in good agreement: a long normal episode has been evidenced from the mid-lignite VII to the top of lignite VIII and referred to the C3n.1n (Cochiti). For several (especially climatostratigraphic) reasons, this assignment has been lowered to C3n.2n Chron in a previous contribution.
Pollen flora is very rich and shows repetitive and almost regular alternations of subtropical swamp forest phases and open vegetation phases. The normal episode related to the C3n.2n Chron includes 6-7 o such alternations that are correlated with the precession cycles. As a consequence, time separating lignites VII and VIII can be estimated at 100kyrs as suggested by van Vugh (2000). The lignite-clay repletion might have been forced by eccentricity (van Vught, 2000), but such an explanation cannot be generalized in a sedimentary system, which has been influenced by other parameters (as subsidence, increased in terrigenous transport). At last, relationships with the reference d18Ocurve (Shackleton et al., 1995) are proposed.