1981/10/01 by Franz T. Fürsich, Franz Theodor Fürsich · 1 citation
Earth and Planetary Sciences · #Marine Biology and Ecology Research #Paleontology and Stratigraphy of Fossils #Geological formations and processes
paper · doi:10.1111/j.1502-3931.1981.tb01690.x
The Upper Kimmeridgian—basal Tithonian clastic sequence at Santa Cruz, Estremadura, represents environments ranging from river channels and flood plains to lagoons and protected bays showing a deltaic influence. Within the marginal marine environments, five benthic macroinvertebrate associations are recognized and analysed in terms of diversity and species composition. All five are thought to be controlled largely by salinity and to represent lowered and/or fluctuating salinity regimes. They can be grouped along a salinity gradient in which the Mesosaccella dammariensis—Corbulomima suprajurensis association, occurring in prodelta silts and marls, represents the closest approach to fully marine conditions and in which the Eomiodon securiformis association, typical of delta front sands, extends into the oligohaline regime. Banks of the Isognomon lusitanicum association and patch reefs of the Praeexogyra pustulosa—Nanogyra nana association are thought to be typical of brachy-to mesohaline conditions occurring in brackish bays and lagoons. Characteristic of the latter salinity regimes is also the Jurassicorbula edwardi association. The integrated approach, using benthic faunas, trace fossils and sedimentological data, leads to a detailed interpretation of the sedimentary sequences and the construction of a biofacies model which can also be used for other parts of the Lusitanian Basin.