Factors influencing ranges of Jurassic and Lower Cretaceous Ostracoda, Eastern North America and Western North Atlantic Ocean

• F.M. Swain ^[1]
  1. [1] University of Minnesota

     University of Minnesota

     City of Minneapolis, Estados Unidos

     
• Localización: Revista española de micropaleontología, ISSN 0556-655X, Vol. 24, Nº. 2, 1992, págs. 43-66
• Idioma: inglés
• Texto completo no disponible (Saber más ...)
• Resumen

  • Over 480 species of mainly marine Ostracoda have been recorded from Jurassic and Lower Cretaceous rocks of the Atlantic and Gulf coastal plains, and Florida, United States; offshore COST Atlantic and Scotian Shelf wells; and DSDP wells off the USA and off the Guianas, South America. Known duration of the species varies from 2-3 million years to over 20 ma, but about half appear to have ranged between 3 and 7 ma.

    Major appearances of new species took place in the Tithonian and the Albian; significant but fewer numbers of species appeared in the Kimmeridgian, Berriasian, Barremian, and Aptian. Major extinctions of Ostracoda species in this region occurred in the Tithonian, Albian, and early Cenomanian; intervals during which important but smaller numbers of species became extinct are the Berriasian, Hauterivian, Barremian, and Aptian.

    Global onlap cycles discussed by Haq, Hardenbol, and Vail (1987) for the Kimmeridgian to Tithonian, and the late Berriasian to Albian correspond reasonably well with major expansions of Ostracoda populations in the study area. The onlap cycles provided widespread shelf environments with plentiful nutrients to support the Ostracoda.

    Restrictions of the stratigraphic rangers of the majority of the Ostracoda species to around 3-7 ma is suggested as having been mainly due to genetic causes and to competition brought about by gradual reduction in nutrient supplies as the shelves aged. Time intervals during which large numbers of species became extinct in the Atlantic-Gulf region, in the absence of known glacial cycles, are suggested as having been caused by aging of the shelf habitats, reduction in food supplies and influx into shelf areas of continental sediments (marine offlap), and Woodbine-Tuscaloosa (middle-late Cenomanian) clastic red-bed wedges. These influxes, initiated by regional tectonism, restricted the broad shelf environments that supported marine Ostracoda populations, but also provided localized fresh-and brackish-water habitats for certain kinds of Ostracoda.