Numerical simulations of tidal and wind-driven circulation in the Cretaceous Interior Seaway of North America

Abstract

Twenty-two numerical experiments using a multi-layer, numerical model of turbulent flow in shallow seas better define fluid circulation and sediment transport paths in the Cretaceous Interior Seaway of North America. Each experiment consists of a different combination of paleogeography, paleobathymetry, Coriolis acceleration, boundary tidal amplitudes, wind stresses, and bed friction. The paleogeographies and paleobathymetries represent three seaway configurations: a seaway of intermediate size and depth (200 m) during a transgressive peak (T5) in late Albian time; a seaway of maximum size and depth (400 m) during peak transgression (T6) in early Turonian time; and a seaway of minimum size and depth (100 m) during a peak regression (R8) in the Campanian. Values for the other key model parameters are: M 2 co-oscillating boundary tides of 0.1 to 0.2 m range at the Arctic Ocean boundary and 0.5 to 1 m range at the proto-Gulf of Mexico boundary; Coriolis accelerations corresponding to 30°N, 45°N, and 60°N latitude; Chezy friction factors ranging from 31 to 70 m ½ s -1 ; and average winter winds and two winter storms computed by the community climate model at the National Center for Atmospheric Research for paleogeographic conditions during the late Albian. Results of the numerical experiments, and comparison of these results with geologic observations, allow the following conclusions. (1) Circulation in the seaway was generally storm-dominated. (2) Typical winter storms crossing the seaway from west to east generated 0.3 m s -1 shore-parallel, geostrophic currents on the shelves north of Arizona, at first flowing weakly to the north, but later during the storm, flowing strongly to the south. (3) Extreme storms could have produced 0.8 m s -1 currents over the shelves, and 0.3 m s -1 currents in 200 m of water.(4) Co-oscillating tides propagated into the seaway as progressive Kelvin waves, and therefore tidal ranges in the seaway were mesotidal to macrofdal along the southeastern margin but microtidal everywhere else. (5) Significant deep-water wave heights and periods of the fully developed wave field are predicted to have been 5 to 6 m high and 10 s, respectively. The northwestern shore of the seaway would have experienced these storm waves approaching from the north, and thus net sediment drift should have been to the south. Limited available field data support these conclusions.