Community dynamics of stabilized dune xerophytic shrubs

Tese de doutoramento, Biologia (Ecologia), Universidade de Lisboa, Faculdade de Ciências, 2016

Silicoflagellates and ebridians from ODP Leg 138 holes

The biostratigraphic distribution and abundance of middle Miocene to Pleistocene silicoflagellates is documented from Ocean Drilling Program (ODP) Leg 138 Holes 844B, 847B, 848B, 849B, 850B, 85 IB, 852B, and 854B from the eastern Equatorial Pacific Ocean. The silicoflagellates were generally abundant and well preserved and frequently exhibited an unusually large range of variation. The upper Miocene of near-equatorial sites includes an assemblage of Bachmannocena diodon nodosa, which includes a bridge across the width of the basal ring. Stratigraphically below this, at sites within 5° of the equator is a lengthy interval of specimens of Distephanus speculum tenuis, which have a fragile apical structure. Both the intervals of Bachmannocena diodon nodosa plexus and Distephanus speculum tenuis are biostratigraphically useful within 5° of the equator, but are less useful beyond that. An unusual range of variation also is observed for Dictyocha in the Pliocene sediments at about the point where D. perlaevis and D. messanensis appear in the geologic record. This variation may be explained by hybridization between diverging species.

Silicoflagellates, actiniscidians, and ebridians of ODP Leg 105 sites

Neogene and Quaternary silicoflagellates, actiniscidians, and ebridians are described from Sites 679 through 688 in the eastern Pacific off Peru. Five silicoflagellate zones and one horizon can be distinguished in the Neogene and Quaternary sequences. The encountered Eocene and Oligocene sequences are barren in silicoflagellates. Several hiatuses were noted in the Neogene and early Pleistocene sequences. Displaced silicoflagellates and ebridians from older strata were found occasionally, with a distinct increase in the Quaternary at Site 688. Distribution lists for species found are presented for Sites 682, 683, 685 and 688. Systematic discussion centers on the Distephanus bioctonarius group, with special reference to Hole 681A. Two new forms (Distephanus bioctonarius f. decimarius and Distephanus speculum subsp. speculum f. pseudoseptenarius) are described from the eastern Pacific Quaternary sequence.

Silicoflagellates of DSDP Leg 90 sites

Silicoflagellates are described from Sites 588 (middle Eocene), 591 (middle Miocene to lower Pliocene), and 594 (middle Miocene to Quaternary) in the southwest Pacific. At Sites 591 and 594 a detailed silicoflagellate zonation is possible, although there are some obvious differences arising from the latitudinal position of the sites in the silicoflagellate assemblages. Comparison between the sequences recovered at Sites 591 and 206 (Leg 21) revealed two hiatuses in the latter, but helped to establish a zonation for this area from the lower Miocene to the Pleistocene and a correlation to standard nannoplankton zones. The stratigraphic implications of the taxonomy used by various authors and the species concept presented here are discussed in detail. Special reference is made to types described by Ehrenberg and to later synonyma, because the Ehrenberg collection is the base for all subsequent descriptions and evaluations of silicoflagellate taxa. Two new genera (Neonaviculopsis, Paramesocena), two new subspecies (Dictyocha fibula subsp. asymmetrica, Neonaviculopsis neonautica subsp. praenautica), and three new forms (Dictyocha perlaevis f. pentaradiata, Distephanus speculum subsp. speculum f. nonarius, and Mesocena ? hexalitha f. heptalitha) are described from the southwest Pacific Neogene and Pleistocene. Associated sponge spicules were noted and will be described in detail in a later paper, but some are documented on Plate 13.