DYNAMIC STRATIGRAPHY WORKGROUP

Processes and Architectures of Deltas in Shelf-break and Ramp Platforms: Examples from the Eocene of West Spitsbergen (Norway), the Pliocene Paleo-Orinoco Delta (SE Trinidad), and the Cretaceous Western Interior Seaway (S Wyoming & NE Utah)

 

People:

Carlos Uroza, Ron Steel

 

Research question(s):

The key contributions of this research concern (1) the feasibility of shelf-margin

accretion during rising and highstand of sea level, (2) the critical importance of shelf width and sediment supply (and not only sea-level behavior) to bring deltas to the shelf edge, and (3) the possible tendency for tides enhancement in the distal reaches of shallow seaway ramps, caused by narrowing of the seaway and fault-topography enhancement during falling sea level.

 

Summary of work:

This project studies four ancient cases with particular characteristics:

1) A shelf-margin case from the Eocene Battfjellet Formation, West Spitsbergen, Norway, in which deltas were able to migrate to the shelf-edge during rising and sea-level highstand conditions despite the low-supply character of the system.

2) A shelf-margin case from the Pliocene paleo-Orinoco Delta System, Mayaro Formation, SE-Trinidad, in which high rates of sediment supply from the paleo-Orinoco River and exceptionally high subsidence rates due to growth-faulting, produced a spectacular stacking of sandstones on the outer shelf and shelf-edge areas, but with apparently limited sand delivery into deeper waters.

3) A case from a shallow-water ramp, Campanian Rock Springs Formation (Western Interior Seaway), and

4) A case from the same ramp setting as (3) but in an outer-ramp site, Campanian Haystack Mountains Formation, in which a lowering in sea-level translated the delta system tens of kilometers eastwards into the basin.

 

In summary, this project compares and contrasts the character of deltaic deposition in basins with different geometries, sediment supply and subsidence histories.

 

Publications and presentations: 

Uroza, C. A., Steel, R. J., 2008, A highstand shelf-margin delta system from the Eocene of West Spitsbergen, Norway, Sedimentary Geology, Volume 203, Issue 3-4, pages 229-245