a. Textures in modern storm sediments. 



b. Geostrophic flow concepts. 



c. Results of flume experiments. 



d. Inferred storm-generated structures within ancient sandstones to 

 construct cross-shelf facies sequences dependent upon water depth, 

 sediment availability, and storm parameters such as return 

 frequency and strength. 



Keen and Slingerland (1993a) note that while these models represent an 

 important conceptual advance, they are qualitative and have not been 

 tested against oceanographic data collected for that purpose, or compared 

 to results of nurherical experiments. 



Keen and Slingerland (1993b) have constructed a three-dimensional nu- 

 merical prediction model to hindcast the oceanographic and sedimen- 

 tologic responses of the western Gulf of Mexico to four historical tropical 

 cyclones. 



The simulations of the numerical model by Keen and Slingerland 

 (1993b) indicate that: 



a. Onshore flow to the right of the storm track generally transports fine 

 sediment landward. 



b. Offshore flow to the left of the storm track transports coarser 

 sediments seaward. 



c. A right-to-left (facing the coast) alongshore flow transports finer 

 sediment in deep water and coarser sediment in shallower water. 



The models of Keen and Slingerland (1993a,b) suggest that coastal geome- 

 try is the controlling factor in determining sedimentation patterns, while 

 in situ sediments are the main source of sediments to the inner shelf. 

 Along the coast in front of each storm, the volume of sediment transported 

 obliquely in a cross-shore direction is a function of the shelf gradient and 

 coastal configuration. Steeper gradients constrain flow to a more long- 

 shore pattern. Concave coastlines promote greater shoreface erosion be- 

 cause of increased setup. 



Chapter 3 Evidence of Cross-Shore Sediment Transport 



39 



