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High-resolution carbon isotope (δ 13 C) profiles from shallow-and deep-water carbonates in the South Atlantic (Campos and Santos Basins) are here correlated to stratigraphically well calibrated Tethyan sections, constraining the end of major evaporite deposition in the South Atlantic to the early Aptian Oceanic Anoxic Event (OAE) 1a interval. The unusually extensive evaporite deposition would have reduced the global dissolved sulfate inventory, possibly increasing global preservation of organic matter by decreasing sulfate reduction; this could explain the coincidence in timing between OAE 1a and the dramatic negative sulfur isotope excursion over this interval. Therefore, in addition to the coeval eruption of the Ontong Java Plateau, the opening of the South Atlantic may have played an important role in the genesis and character of OAE 1a.

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-Eleven wells (1,765 cutting samples) from the Senonian of Santos Basin were examined, with the record of both marine and mixohaline ostracode faunas. The latter are composed mainly by Fossocytheridea and characterized by medium specific richness and high abundance. Four new species are here described: F. posterodentata, F. ventrotuberculata, F. santosensis and F. anfisulcata and another one is left in open nomenclature. Besides the conspicuous variability, F. ventrotuberculata sp. nov. is the first species described for the genus with valve reversal. The significance of these new species described and their potential for applied approaches are discussed.Key words: Fossocytheridea, Ostracoda, taxonomy, Brazil, Santos Basin.RESUMO -Onze poços (1.765 amostras de calha) do Senoniano da bacia de Santos foram estudados, registrando faunas de ostracodes marinhas e mixoalinas. Estas são compostas basicamente por Fossocytheridea e caracterizadas pela riqueza específica baixa e alta abundância. Quatro novas espécies são aqui descritas: F. posterodentata, F. ventrotuberculata, F. santosensis e F. anfisulcata, e outra é deixada em nomenclatura aberta. Além da notável variabilidade, F. ventrotuberculata sp. nov. é a primeira espécie descrita para o gênero com reversão de valvas. A importância destas novas espécies descritas e seu potencial para estudos aplicados são discutidos. Palavras INTRODUCTIONThe first researches on Cretaceous ostracodes from Santos Basin were done by Benson (1977) and Miller et al. (2002). More detailed taxonomic work began with the description and ecological characterization of the species Afrocytheridea? cretacea and Pelecocythere dinglei by Piovesan et al. (2010).One of the most remarkable consequences of the scarcity of taxonomic knowledge is the limitation it imposes on paleoceanographical and biostratigraphical uses. Ostracodes are the most abundant calcareous microfossil in the Upper Cretaceous paralic deposits of Santos Basin. Considering that this basin was strongly affected by sea-level changes, ostracode populations were influenced accordingly, under conditions favorable for speciation. These faunas are dominated by cytherideids, Fossocytheridea Swain & Brown being the most common genus.The first record of Fossocytheridea in Brazil was by Viviers et al. (2000) in the Campanian of Potiguar Basin, as Sarlatina Babinot & Colin, which is now considered its junior synonym (Tibert et al., 2003). In the latter article, some species of Fabanella Martin, Ovocytheridea Grekoff, Dolocytheridea Triebel, Antibythocypris Jennings and Cytheridea Bosquet, were also reassigned to Fossocytheridea. In other Cretaceous deposits (e.g. Western Interior Basin, USA: Swain & Brown, 1964, Tibert et al., 2003, 2009 West Africa, Mali: Colin et al., 1996) assemblages with Fossocytheridea are interpreted as indicators for marginal-marine environments. The ecological classification of brackish-water environments into oligohaline, mesoahaline and polyhaline used herein follows Belt et al. (2005).The main obje...

An accurate biostratigraphic framework of the Cretaceous marine section of Campos Basin was established based on studíes of foraminifera, nannofossils, and palynomorphs. With the research of 77 wells it was possible to subdivide the Albian-Maastrichtian section in 11 zones of foraminifera,6 zones of nannofossils, and 7 zones of palynomorphs (the study ofwhich was restricted to the Albian-Santonían stages). Some of these zones remain still informal. Three main regional unconformities were found in the biostratigraphic sequence. These gaps correspond to the Early-Middle Cenomanían, Middle-Late Turonlan and Campanían. Less ímportant hiatuses were also found in the area.

-A biostratigraphic and paleozoogeographic revision of the upper Aptian-Albian ostracods of Riachuelo Formation, in the Sergipe-Alagoas Basin, Brazil, was conducted. The studied material comprised 336 samples from several outcrops, along with well cores drilled by Petróleo Brasileiro S.A. (PETROBRAS). After taxonomic analysis, including the description of Reticulocosta edrianae n. sp., a new biozonation scheme was obtained for the Albian interval of that formation, and the paleozoogeographic affi nities of the Brazil-Central West Africa province were reviewed through comparison with results published in the current literature. Several changes were made to previously established ostracod zones. A new code for the Aracajuia benderi Zone (OSE-1), MSA-0, was created, with impact in all of its subzones. The names of the Pattersoncypris ex. gr. angulata (OSE-1.1), 'Patellacythere' sp. GA E 27 (OSE-1.3) and Veenia guianensis (OSE-1.4) subzones were changed to Harbinia sinuata? (MSA-0.1), Praebythoceratina amsittenensis (MSA-0.3) and Reticulocosta edrianae (MSA-0.4), respectively. The Sergipella viviersae Subzone (OSE-1.2) had its code changed for MSA-0.2; also, a stratotype was stablished for it, and the lower limit of the subzone was changed, from lower Albian in previous works to upper Aptian. The Metacytheropteon aff. Metacytheropteron sp. GA C 24 Subzone (OSE-1.5) was renamed MSA-0.5. The uppermost Albian Aracajuia antiqua Latest Occurrence Interval Zone (MSA-1) is herein proposed, following the reclassifi cation Aracajuia benderi specimens of the Aracajuia benderi Subzone (OSE-1.6) to Aracajuia antiqua. Paleozoogeographic analyses showed some faunal interchange with Tethyan provinces, beginning in the latest Aptian, at both specifi c and generic levels. Limited northward marine infl uxes across the Walvis ridge were also observed during the Albian, while larger scale southward migrations occurred in the early Cenomanian. The presence of Brachycytherinae species in the Brazil-Central West Africa province as early as the Aptian indicates a new zoogeographic origin for this subfamily, while explaining the occurrence of the group in both the Austral realm and part of the Tethyan realm during the Albian.Key words: Early Cretaceous, South Proto-Atlantic ocean, marine ostracods, MSA-1 Zone, province interchange.RESUMO -Uma revisão bioestratigráfi ca e paleozoogeográfi ca dos ostracodes do Aptiano superior-Albiano da Formação Riachuelo, bacia de Sergipe-Alagoas, Brasil, foi proposta no presente trabalho. O material estudado compreendeu 336 amostras de vários afl oramentos, juntamente com testemunhos de poços perfurados pela Petróleo Brasileiro S.A. (PETROBRAS). Após a análise taxonômica, incluindo a descrição de Reticulocosta edrianae sp. nov., um novo zoneamento bioestratigráfi co foi obtido para a formação, e as afi nidades paleozoogeográfi cas da província Brasil-África Central Ocidental (incluindo a bacia de Sergipe-Alagoas) foram revistas por meio da comparação com resultados publicados na literatura existen...

lntcgration c f micropaleontologieal information , based mainly on the study of foraminifers and palynomorph s from seven wells, led to the reeognition of th e paleoenvironm ental development of the Potíguar Basin from the Alagoas to the Maastriehtian. Seventeen bioestrat lgraphlcal zones and one subzone have been recognized. Seven episodes-four tr ansgressive and three regressive-could be dete cted between the Early-Middle Albian to th e Maastriehtian , and have been regarded as result from relative global fluctuatíons of the Cretaeeous sea level. A distinctive hiatu s of Late Albian age may be inferred from the absenee of diagnostie index fossils. Fine grained clastic sediments deposited duríng the Late Cenomanian and the Early Turonian show evidence of anoxia. This is assumed to be synchronous with similar events detected elsewhere in many Cretaeeous basins (including some in Braail). Carbo natie cycles have been found to oeeur in the Early-Mlddle Albian, Early-Middle Cenomanian, Turonian and ConiacianjSanto nian, each of th em being represent ed by shallow neritie palcoecological units wíth distinetive mierofaunal assemblages: Early-Middle Albian-Favuse/la spp., calcispherulíds association ; Ear1y-Middle Cenomanian-Trocholína spp. association ; Turonian-marine ostracods-gastropcd s-worrn tubes association ; Santonian-Buliminidae-8iphogenerínoídes spp.-Dinogy mn ium spp.•Deflandrea spp. association.

-This study presents the taxonomy of benthic foraminifera, ostracods, and radiolarians of a sedimentary succession within the Lachman Crags Member, Santa Marta Formation (upper Santonian-lower Campanian), northwestern James Ross Island. Twenty-seven benthic foraminiferal species, six ostracod species, and six radiolarian species were identifi ed. Calcareous microfossils occurrences are restricted to few stratigraphic levels described as tuffaceous sandstones cemented by calcium carbonate, while siliceous microfossils and agglutinated foraminifera also occur in different lithofacies. This suggests a preservational bias in the occurrences of microfossils within the studied section, possibly related to the presence/absence of calcium carbonate cement. The benthic foraminiferal fauna presents a low degree of endemism with the dominance of cosmopolitan taxa (e.g. Gyroidinoides globosus (Hagenow), Gavelinella sandidgei (Brotzen). Consistent occurrences of G. globosus suggest the dominance of deep-neritic to upper-bathyal paleodepths. The ostracod genera identifi ed herein have already been reported for the Cretaceous of the Gondwana region and suggest deposition on a shelf with warm water temperature and normal salinity. The studied radiolarian fauna, the fi rst one described for the James Ross Island region, can be considered Late Cretaceous in age, also presenting the dominance of robust (dissolution resistant) cosmopolitan taxa.