Evolution of Maastrichtian paleoproductivity along the southern Tethys margin (Jordan): from upwelling to runoff

The Upper Cretaceous succession in Jordan records the evolution of an upwelling system characterised by the widespread deposition of phosphorites, siliceous mudstones, and carbonate mudstones with TOC contents of up to 30 wt%. Here, we investigate the Maastrichtian succession of Jordan along a basin-scale SW–NE transect (∼61 km) using a multi-proxy approach that integrates sedimentological and geochemical datasets within a high-resolution biostratigraphic framework.
Regional correlations reveal hierarchical depositional cyclicity and a diachronous distribution of organic matter that progressively shifted landward through time. Maximum TOC enrichment occurred under conditions of high paleoproductivity associated with an upwelling system. Trace-element enrichments (Ni, Cu, Zn, Mo, U, and V) further suggest a strong coupling between productivity and the development of an oxygen minimum zone (OMZ), analogous to modern upwelling systems. The organic-rich carbonate interval was deposited from the early Maastrichtian (UC16b) to the late Maastrichtian (UC20a), representing approximately 2.5 myr of sustained high-productivity conditions in central Jordan.
During the late Maastrichtian, a major paleoceanographic reorganization occurred, weakening the upwelling system and causing a split in organic carbon and mineral carbon productivity cells on the Levant shelf. Organic-matter productivity continued into the Paleocene in the nearshore realm (southern Jordan), driven primarily by continental runoff. In contrast, in the more distal, seaward part of the shelf, sediment production shifted toward carbonate-producing planktonic microorganisms.
This study thus provides a dynamic picture of Maastrichtian paleoproductivity in Jordan and presents a model that may apply to other locations along the submerged southern Neo-Tethys Ocean margin shelves.