Paleocene ostracods and planktonic foraminifera from the Maria Farinha Formation, Paraíba Basin, are herein presented. Eleven ostracod species were identified in the genera Cytherella Jones, ...Cytherelloidea Alexander, Eocytheropteron Alexander, Semicytherura Wagner, Paracosta Siddiqui, Buntonia Howe, Soudanella Apostolescu, Leguminocythereis Howe and, probably, Pataviella Liebau. The planktonic foraminifera are represented by the genera Guembelitria Cushman, Parvularugoglobigerina Hofker, Woodringina Loeblich and Tappan, Heterohelix Ehrenberg, Zeauvigerina Finlay, Muricohedbergella Huber and Leckie, and Praemurica Olsson, Hemleben, Berggren and Liu. The ostracods and foraminifera analyzed indicate an inner shelf paleoenvironment for the studied section. Blooms of Guembelitria spp., which indicate either shallow environments or upwelling zones, were also recorded reinforcing previous paleoenvironmental interpretations based on other fossil groups for this basin.
Ostracode assemblages of the Poty quarry, Pernambuco-Paraíba Basin, northeastern Brazil, record an abrupt faunal change near the Cretaceous-Paleogene (K-Pg) boundary. Paleoecological and stable ...isotope analyses of ostracode carapaces were used to interpret the paleoenvironmental changes that took place from the Late Maastrichtian to the Early Danian. Ostracode distribution demonstrates substantial changes at and around the boundary with the last occurrences of most species and appearance of new ones. Stable isotope analyses carried out for four ostracode species distributed along the entire succession exhibit oscillations in the isotopic composition before the K-Pg boundary, thus suggesting that environmental changes may have begun slightly prior the boundary event itself. These changes may have triggered the extinctions that culminated at the K-Pg boundary, marked by positive δ18O and negative δ13C excursions. The K-Pg boundary is marked by cooling of bottom seawaters and a decrease in productivity, as well as the beginning of an extensive marine regression.
•The Poty quarry in Brazil exposes the K-Pg boundary.•Changes in the ostracode assemblages coincide with the extinction event.•Isotopic data gained from ostracode carapaces indicate environmental changes before K-Pg boundary.•Paleoecological interpretations of ostracode assemblages are performed.•Isotopic analyses suggest five isotopic stages.
Paleoecological analyses are important tools for the reconstruction of paleoenvironments. This paper had the objective of using analysis of ostracode assemblages and carbonate microfacies of a well ...(Carbomil) and an outcrop (Quixeré) from the Jandaíra Formation, Potiguar Basin, in order to verify how they corroborate and complement the other. Two paleoenvironments for Carbomil Well (assemblages 1 and 2, respectively marine and brackish to neritic environments) and one for Quixeré Outcrop (assemblage 3, marine environment) were identified through the ostracode assemblage analysis. Thin section analysis allowed the identification of two different facies for Carbomil Well, i.e. bioclastic packstones to wackstones, a marine brackish or restricted marine system; and bioclastic grainstones to packstones, a normal, shallow marine system. High levels of alteration on the samples prevented an adequate analysis of Quixeré Outcrop; however, it seems to point towards a low-energy environment. Overall, information provided by the thin sections corroborate and complement data of the ostracode assemblages, which allowed a higher degree of certainty for the paleoenvironmental analysis.
Análises paleoecológicas são ferramentas importantes para a reconstrução de paleoambientes. Este trabalho teve como objetivo utilizar análises de associação de ostracodes e microfácies carbonáticas de um poço (Carbomil) e um afloramento (Ponto Quixeré) da Formação Jandaíra, Bacia Potiguar, a fim de verificar como estes métodos corroboram e complementam um ao outro. Dois paleoambientes para o Poço Carbomil (associações 1 e 2, respectivamente, ambiente marinho e mixo-halino) e um para o Ponto Quixeré (associação 3, ambiente marinho) foram identificados por meio da análise das associações de ostracodes. O estudo das seções petrográficas permitiu a identificação de duas fácies diferentes para o Poço Carbomil, packstonesa wackstonesbioclásticas, representando um sistema marinho salobro ou marinho restrito; grainstonesa packstonesbioclásticas, indicando um sistema marinho raso normal). As amostras do Ponto Quixeré parecem apontar para um ambiente de pouca energia. Em geral, as informações provenientes da análise das microfácies carbonáticas corroboram e complementam os dados fornecidos pelas assembleias de ostracodes, o que permitiu um maior grau de precisão na análise paleoambiental.
Within the Cretaceous Period, the Aptian-Albian interval (125–99.6 Ma, Ogg et al., 2008) was a critical time on a global scale. This is evident from 1) changes in the nature of the ocean-climate ...system brought about by increased ocean crust production coupled with active midplate and plate margin volcanism in a shifting paleogeography (Skelton et al., 2003); 2) cyclic deposition and preservation of common “black shales”, some of them termed Oceanic Anoxic Events(OAE1a to OAE1d) (Schlanger and Jenkyns, 1976; Arthur et al., 1990); 3) periodic changes in redox conditions at the ocean bottom (Oceanic Red Beds, ORBs) (Wang et al., 2009); and 4) rapid biotic radiations and turnovers (Leckie et al., 2002). The Aptian-Albian time is also of interest for one of the most noteworthy geomagnetic events, namely the post-M0r “Cretaceous Quiet Zone”. This long and constant normal polarity superchron without any convincing true reversal to date (Satolli et al., 2008) precludes usage of reversals magnetostratigraphy from the Aptian through the Santonian. The Poggio le Guaine core was designed to provide a high-resolution age model and a high-resolution relative magnetic paleointensity reference curve for the Aptian-Albian interval of the long normal Cretaceous superchron; it was also designed to understand the causal linkages among geological, biogeochemical, oceanographic and climatic eventsas well as their consequences. The core was drilled at Poggio le Guaine, where the most continuous, complete, and best preserved Aptian-Albian succession is exposed throughout the Umbria-Marche Basin (UMB) of the northern Apennines of central Italy (Fig. 1). It represents a continuous record of fossiliferous pelagic rocks extending from the Albian-Cenomanian boundary down to the uppermost Barremian (99.6–126 Ma). In this progress report we present the first preliminary findings of this ongoing project.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
A new genus and species of roveacrinid, Sergipecrinus reticulatus, is described from the upper Aptian and lower Albian of the Sergipe-Alagoas Basin, northeast Brazil, on the basis of abundant cups ...and isolated brachials from core SER-03. This is the first roveacrinid of Aptian age to be described and provides important information concerning the early history of the Roveacrinidae.
This paper reports the occurrence of a Toarcian–Aalenian (Early–Middle Jurassic) radiolarian fauna in the Los Molles Formation, Neuquén Basin, Argentina, as well as comments on its paleobiogeographic ...affinities. The micropaleontologic analysis was carried out in fine-grained rocks from a turbiditic section of the Los Molles Formation. These samples were first chemically processed using only hydrogen peroxide (H
2O
2), and afterward treated with acetic (CH
3COOH) and hydrofluoric (HF) acids. The first chemical procedure permitted the recovery of only few spongy spumellarians, while the second one enabled to recover more diversified radiolarian assemblages. In general, the studied fauna presents low diversity and abundance, with a strong dominance of spumellarians over nassellarians. The fauna is composed by the genera
Paronaella,
Homoeoparonaella,
Praeconocaryomma,
Archaeocenosphaera,
Orbiculiformella,
Praeparvicingula, and some unidentified spumellarians and nassellarians. According to paleobiogeographic models, the studied Toarcian–Aalenian fauna presents a mid to high latitude affinity. It is possible to infer from those data a bipolar distribution of some taxa, such as
Praeparvicingula and probably
Praeconocaryomma, between the Northern and Southern hemispheres since the Early Jurassic (Toarcian).
► The studied radiolarian fauna presents a mid to high latitude affinity. ► This paleobiogeographic affinity is probably due the influence of cold waters. ► We infer a bipolar distribution of taxa since the Early–Middle Jurassic. ► This pattern of bipolarity was previously observed for Upper Jurassic and Cenozoic.
The Maastrichtian - Danian transition is characterized by one of the largest mass extinctions recorded in the geological history of Earth, the Cretaceous-Paleogene (K-Pg boundary). Chemostratigraphic ...indicators (e.g. Mercury) are of fundamental importance for understanding the causes of this extinction and its effects on the environment in which life after the K-Pg boundary flourished. This study presents a new mercury (Hg) concentrations and Hg/TOC dataset for Deep Sea Drilling Project (DSDP) Site 516F (Rio Grande Rise), in the framework of carbon cycle proxies that depict the Dan-C2 event within the ∼500 kyr that followed the K-Pg event, from 66.05 to 65.55 Ma, and their temporal relationship with the Deccan Traps (DT) volcanic event. Enriched Hg and Hg/TOC values were observed between ∼65.89 Ma (963.45 mbsf) and 65.98 Ma (963.73 mbsf), ∼60 kyr before (or 40 cm below) the Dan-C2 event. Furthermore, the stratigraphic position with the highest Hg and/or Hg/TOC values is ∼40 kyr after the K-Pg boundary. Our results suggest that the DT volcanism is unrelated with the Dan-C2 event observed at Site 516, and that the highest Hg/TOC appear to be coeval with the eruption of the Deccan Ambenali Formation lavas at about ∼65.90–65.95 Ma.
•Recognition of Hg and Hg/TOC anomalies for Early Danian in Rio Grande Rise.•Pronounced Hg and Hg/TOC enrichment between the K-Pg boundary and the Dan-C2 event.•Mercury enrichment associated with Deccan Trap eruption (Ambenali Formation).
Changes in oceanic circulation and productivity patterns near Central America have been explained using numerous different tools, such as tectonics, geochemistry and micropaleontology. This paper ...aims to contribute to this discussion through the study of dinoflagellates and palynofacies in the drill core from DSDP Site 153. Based on foraminiferal data, the studied section is divided into the middle and upper Miocene, and our dinoflagellate events also support an age model of ~15 to 8 Ma. IndVal, ecological indexes, and the (P/G) dinoflagellate ratios were used to develop paleoenvironmental inferences. The indicator species are Operculodinium centrocarpum and Tectatodinium pellitum for the MM1 interval, Spiniferites spp. and Impagidinium strialatum for MM2, and Selenopemphix armageddonensis, Lejeunecysta spp. and L. tenella for UM3. Intervals MM1 and MM2 are characterized by a dominance of gonyaulacoids, and inner to outer neritic environments. The UM3 interval is interpreted as an outer neritic environment in the base/middle portion, and inner neritic in the uppermost part, with a shift from gonyaulacoid to peridinioid dominance, suggesting an increase in productivity. During the middle Miocene, productivity is low due to intermittent marine circulation restrictions in the Caribbean Sea, and there is a slight increase during the upper Miocene following reestablishment of the global oceanic circulation. This is directly connected to the occurrence of geotectonic and paleoceanographic events in the region during the Miocene, mainly by mass movements such as the Panama gateway and the opening of the Pedro Channel to the north, changing the surface conditions in the Caribbean Sea.
•Paleoenvironmental reconstruction of the central Caribbean during the Miocene.•Stratigraphic distribution of middle to late Miocene dinoflagellates.•Indicator species analysis, ecological indexes and dinoflagellate ratio (P/G).•Autotrophic dominance in the middle Miocene, and heterotrophic in the upper Miocene.
Early Cretaceous sedimentary basins on the South Atlantic continental margins of South America and Africa are closely related with the Gondwana break-up, and record coeval paleoceanographic, ...paleoclimatic, and biotic changes during the late Barremian–Albian. The Sergipe-Alagoas Basin of northeastern Brazil contains one of the most complete Lower Cretaceous stratigraphic successions of the South Atlantic Ocean, including sedimentary and paleontological records nearly absent in nearby basins on the African/Brazilian continental margins. Fossil-rich sedimentary successions from the Sergipe-Alagoas Basin have allowed to assess: (i) evolutionary stages of the early South Atlantic Ocean; (ii) paleobiogeography of marine incursions (Austral and/or North Atlantic/Tethyan influences); and (iii) local signatures of global-scale paleoceanographic, paleoclimatic, and biotic events. Here we provide an overview on fossil-based biostratigraphic and paleoenvironmental studies of the Sergipe-Alagoas Basin, from the first marine incursions in a continental setting, to fully open-marine conditions. Based on eight fossil groups (ammonites, calcareous nannofossils, echinoids, planktonic and benthonic foraminifera, ostracods, palynomorphs, and radiolarians) from 107 sites, we observed that the marine biota shows strong affinity with Tethyan Realm in the Aptian–Albian interval, and provincialism/endemism is likely tied to the early-stage development of the South Atlantic Ocean. Based on late Barremian–late Albian lithological, paleontological, and geochemical data, we suggest three Sergipe-Alagoas Paleoenvironmental Stages (SAPSs): (i) continental conditions with possible episodic marine incursions (SAPS-1); (ii) transitional system, from continental to restricted-marine conditions (SAPS-2); (iii) transition from restricted- to open-marine conditions (SAPS-3). These local-scale evolutionary stages are correlated with early phases of the South Atlantic Ocean and major late Early Cretaceous paleoceanographic and paleoclimatic events. Moreover, we provide new approaches on the response of low-latitude biota to changing ocean circulation patterns in a hot, ice-free “greenhouse” world.
•Sergipe-Alagoas Basin presents an Early Cretaceous complete marine succession.•Biostratigraphic and paleobiogeographic review about ammonites and microfossils.•Paleoenvironmental evolution since marine incursions to open marine.•Paleoceanographic stages of the early South Atlantic Ocean were presented.•Correlation between the stages with global scale paleoceanographic events.
Short-lived (104–105 years) carbon isotope excursions (CIEs), many of which are associated with some degree of ocean warming, are a feature of the warm climates of the early Paleogene. Here we ...present new calcareous nannofossil and geochemical data through the first of these Paleogene carbon cycle perturbations, known as the DAN-C2 event (65.8–65.7 Ma), from ODP Site 1049C on Blake Nose, in the western sub-tropical North Atlantic. Increased Hg/TOC (ppb/%) and Hg/Al (ppb/cps) ratios recorded at 65.9 Ma strongly suggest that volcanic activity, likely related to Deccan Traps, preceded the DAN-C2 event. Approximately 20 kyr after the onset of DAN-C2, Shannon diversity (H) index shows increased nannofossil species richness, with greater abundances of eutrophic and high fertility species, most likely a response to more intense weathering during the event. During the DAN-C2 event, there is a shift towards smaller morphotypes of the dominant placolith species, Coccolithus pelagicus and Cruciplacolithus primus, together with a calcium carbonate dissolution interval. Finally, we suggest that surface ocean currents dynamics, influenced by an eccentricity maxima cycle, is likely a potential mechanism to explaining the strong δ13C (∼1.3 ‰) negative excursion observed in Blake Nose.
•Deccan Traps eruption recognized at 65.90 Ma in high productivity conditions.•Strong evidence of biotic response to terrigenous input during Dan-C2.•Dissolutions effects impacted carbonate preservation, reducing coccolith size.
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