GLOBAL CORRELATION OF LATE CENOZOIC FLUVIAL DEPOSITS; AN UPDATE ON IGCP 449

IGCP 449 has been engaging the fluvial community, especially those interested in long fluvial sequences, since 2000. It started in NW and Central Europe and by the end of 2003 will have been represented at meetings on every major continent. Results to date can be summarized under the following headings:

Key sequences

These are the river systems with lengthy fluvial archives benefiting from multiple lines of dating evidence. Targeted for eventual inclusion within the project database, they include:

NW Europe: Thames, Seine, Somme, Maas, Rhine. Central Europe: Wipper, Vltava, Svratka, Danube E Europe: Dniester, Dnieper, Volga, Don Middle East: Orontes, Euphrates Africa: Nile, Vaal/Orange India: Ganges, Narmada, Pravura Australia: Murray/Darling, Shoalhaven China: Yellow River North America: Susquehanna, Mississippi, St Lawrence South America: Parana

Patterns of fluvial sedimentation and valley evolution over Neogene and Quaternary timescales

The data thus far assembled has revealed clear differences between fluvial records in different areas, apparently related to different types of continental crust with different uplift/subsidence histories. These fall into three groups:

1. Uplifting pattern, with extensive terrace staircases, climatically forced. Early and pre- Quaternary terraces are >100m above existing valley floor. Requires young (post-Archaean) crust. Cause of uplift is the subject of debate. Examples: Thames, Somme, Wipper, Vltava, Dniester, Shoalhaven, Yellow River.

2. Subsiding pattern, with stacked fluvial sediments. Requires young crust, subsiding because within or peripheral to sedimentary accumulation basin (sediment loading). Examples: Lower Rhine, Ganges, Körös Basin, offshore Mediterranean coastal rivers such as the Gediz, Büyük Menderes, Axios & Seyhan.

3. Stable pattern, with terrace preservation a factor of diversion events and/or decrease in discharge rather than significant incision. Early and pre-Quaternary deposits occur within a few metres of modern river level. Restricted to ancient cratonic crust, apparently experiencing minimal Late Cenozoic uplift or downwarping. Examples: Narmada, Pravura, Vaal, Lower Volga.

Glacio- and hydro-isostatic effects can be overprinted on these patterns, providing a further link to Quaternary climatic fluctuation.