Cenomanian to Coniacian Water-mass Evolution in the Cretaceous Western Interior Seaway of North America and Equatorial Atlantic
James S. Eldrett1, Paul Dodsworth2, Steven C. Bergman3, and Milly Wright41Shell International Exploration & Production B.V, Kesslerpark 1, 2288 GS Rijswijk, Netherlands 2StrataSolve Ltd, 42 Gaskell Street, Stockton Heath, Warrington, WA4 2UN, UK 3Shell International Exploration and Production Inc, 3333 Highway 6 South, Houston, TX, 77082, USA 4Chemostrat Inc., 3760 Westchase Drive, Houston, Texas, TX 77042, USA
Received: 01 Nov 2016 – Accepted for review: 18 Nov 2016 – Discussion started: 25 Nov 2016
Abstract. The Late Cretaceous Epoch was characterized major global perturbations in the carbon cycle, the most prominent occurring near the Cenomanian-Turonian (CT) transition marked by Oceanic Anoxic Event/OAE-2 at 94.9–93.7 Ma. The Cretaceous Western Interior Seaway (KWIS) was one of several epicontinental seas in which a complex water-mass evolution was recorded in widespread sedimentary successions. This contribution integrates new data on the main components of organic matter, geochemistry, and stable isotopes along a North-South transect from the KWIS to the equatorial western Atlantic and Southern Ocean. In particular, cored sedimentary rocks from the Eagle Ford Group of West Texas (~ 90–98 Ma) demonstrate subtle temporal and spatial variations in paleoenvironmental conditions and provide an important geographic constraint for interpreting water-mass evolution. High latitude (boreal-austral), equatorial tethyan and locally sourced Western Interior Seaway water-masses are distinguished by distinct palynological assemblages and geochemical signatures. The northward migration of a tethyan water-mass into the KWIS occurred during the early-middle Cenomanian (98–95 Ma) followed by a major re-organization during the latest Cenomanian-Turonian (95–94 Ma) as a full connection with a northerly- boreal water-mass was established during peak transgression. This oceanographic change promoted de-stratification of the water column and improved oxygenation throughout the KWIS and as far south as the Demerara Rise off Suriname. In addition the recorded decline in redox-sensitive trace metals during the onset of OAE-2 likely reflects a genuine oxygenation event related to open water-mass exchange and may have been complicated by variable contribution of organic matter from different sources (e.g. refractory/terrigenous material), requiring further investigation.
Eldrett, J. S., Dodsworth, P., Bergman, S. C., and Wright, M.: Cenomanian to Coniacian Water-mass Evolution in the Cretaceous Western Interior Seaway of North America and Equatorial Atlantic, Clim. Past Discuss., doi:10.5194/cp-2016-111, in review, 2016.