Comment on "Orbitally forced climate and sea-level changes in the Paleoceanic Tethyan domain (marl–limestone alternations, Lower Kimmeridgian, SE France) " by S. Boulila, M. de Rafélis, L. A. Hinnov, S. Gardin, B. Galbrun, P.-Y. Collin [ Palaeogeography Palaeoclimatology Palaeoecology 292 (2010) 57–70

Abstract

A recent paper by Boulila et al. (2010) reports on orbitally-forced cycles recorded as marl-limestone alternations in one Lower Kimmeridgian section, Chateauneuf d'Oze (SE France, Tethyan domain). In an attempt to illustrate the in situ (i.e., pelagic) origin of carbonates in marls and limestones, the authors challenged the results of previous work concerning sections from other Tethyan areas of similar age, which demonstrate that nannofossil abundance is originally higher in marls than in limestones. Boulila et al. (2010) present data acquired with optical and Scanning Electron microscopes estimating nannofossil contribution to the rocks. However, their selected illustrations do not support a high contribution of the nannofossils to the carbonate fraction of their samples or their interpretation of the finest fraction of the rocks (micarbs). Furthermore, according to their data on carbonate content of the rocks, they did not analyse true marl-limestone alternations, but slightly argillaceous limestones and limestones. Boulila et al. (2010) also criticize earlier work providing a sequence stratigraphy interpretation of the Chateauneuf d'Oze section. However, contrarily to these earlier works, they did not consider platform-to-basin correlations that are essential in order to understand the sedimentary dynamics at the basin-wide scale. This comment challenges the work by Boulila et al. (2010) that largely underestimates the role of carbonate production on shallow platforms and its subsequent export basinwards as a major mechanism controlling the sedimentation in epicontinental basins.