Chemostratigraphy of the 'lower' Sparnacian deposits (Argiles plastiques bariolees) of the Paris Basin

The late Paleocene was marked by an abrupt 3-4‰ drop in the carbon isotopic composition of the ocean, a drop which was superimposed on a longer-term decline during the late Paleocene to early Eocene. The magnitude of carbon isotopic changes during the late Paleocene-early Eocene interval requires that carbon was exchanged between the large marine and the smaller atmospheric and terrestrial carbon reservoirs. This study presents the carbon isotopic record from terrestrial organic matter from the uppermost Paleocene terrestrial sequences that constitute the Argiles Plastiques Formation in the Paris Basin. The most striking feature of the δ¹³C organic record is the presence of a sharp carbon isotopic negative excursion which is similar in magnitude, in direction, and in (inferred) temporal duration to the latest Paleocene marine carbon isotopic excursion. It is proposed that this excursion in marine and terrestrial carbon reservoirs constitutes a precise datum level that can be recognized and correlated between marine and terrestrial Paleocene/Eocene boundary sequences.