ESTUARINE CIRCULATION IN THE TURONIAN-WESTERN-INTERIOR SEAWAY OF NORTH-AMERICA

To understand the patterns of lithofacies, marine faunas, organic-carb on enrichment, isotopes, and trace elements deposited in the early Tur onian Western Interior seaway, we conducted circulation experiments us ing a three-dimensional, turbulent flow coastal ocean model driven by GENESIS, a climate model developed at the National Center for Atmosphe ric Research (NCAR). Circulation and chemical evolution of the seaway waters are computed under the following initial and boundary condition s: (1) paleobathymetry according to a new interpretation of the lithos tratigraphy and biostratigraphy; (2) temperatures and salinities of th e Boreal and Tethys oceans and adjacent drainage basins based on isoto pic data, atmospheric temperatures, and precipitation-evaporation magn itudes computed by GENESIS; and (3) mean annual wind stresses over the seaway computed by GENESIS. Results show that the seaway exported fre shened mater much like Hudson Bay today, Runoff from eastern drainages exited the seaway as a northern coastal jet; runoff from western drai nages exited as a southern coastal jet. Both jets simultaneously drew in surface Tethyan and Boreal waters, creating a strong counterclockwi se gyre occupying the entire north-south extent of the seaway, The cur ious stratal and faunal variations of the early Turonian deposits aris e from this gyre and its associated water masses.