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- Early and Middle Jurassic palynostratigraphy of the Lusitanian Basin in the proto-Atlantic contextPublication . Correia, Vânia; Pereira, Zélia; Riding, James; Duarte, L. V.; Henriques, Maria Helena; Fernandes, PauloSUMMARY: A palinologia é uma ferramenta muito útil nos trabalhos de bioestratigrafia e interpretações paleoambientais, e que pode ser aplicada no conhecimento da geologia da Bacia Lusitânica. Assim, foi desenvolvido um estudo palinoestratigráfico de alta-resolução em 8 cortes do Jurássico Inferior e Médio (Sinemuriano superior—base do Batoniano) da Bacia Lusitânica e, neste trabalho, são apresentados os intervalos de ocorrência e bioeventos associados aos principais taxa identificados, nomeadamente no grupo dos quistos de dinoflagelados.
- Palynology and palynofacies studies in the lowermost Jurassic of the Lusitanian Basin (Pereiros Formation of the Silves Group), Portugal: evidence of the first transgressive episodePublication . Vilas Boas, Margarida; Pereira, Zélia; Cirilli, Simonetta; Duarte, L. V.; Sêco, Sérgio Luís Rodrigues; Fernandes, PauloABSTRACT: he Silves Group of the Lusitanian Basin in Portugal represents the initial infill of the continental rifting basins that formed during the breakup of northern Pangaea regions. Evaporites, especially halite, mark the transition from continental to marine settings and the beginning of the deposition in passive margin basins. This work presents the results of the palynostratigraphic and palynofacies analysis of two partial sections from the Pereiros Formation at the top of the Silves Group. The two sections are composed of sandstones, mudstones and dolostones interpreted as deposited in fluvial and lacustrine settings without apparent marine influence. The palynological content is diverse and wellpreserved, dating both sections to the early Hettangian (Lower Jurassic), indicated by the presence of spores Ischyosporites variegatus, Kraeuselisporites reissingeri, Porcellispora longdonensis and the pollen grains Perinopollenites elatoides and Pinuspollenites minimus. The palynological content of one of the sections (Lamas I) is noticeable by microforaminifera linings, suggesting evidence for a hitherto marine incursion at this age in the Silves Group stratigraphy. The beds that yielded the microforaminifera linings are interpreted as having been deposited in an estuarine-type setting, created by the first and short-lived marine transgressive event in the Lusitanian Basin during the early Hettangian.
- New data on the palynology of the Triassic Jurassic boundary of the Silves Group, Lusitanian Basin, PortugalPublication . Vilas Boas, Margarida; Pereira, Zélia; Cirilli, Simonetta; Duarte, L. V.; Fernandes, PauloABSTRACT: New evidence is presented on the Triassic-Jurassic boundary in the northern Lusitanian Basin, Portugal, based on miospore assemblages from a composite Upper Triassic to Lower Jurassic succession of the Silves Group. The latter comprises, from base to top, the Conraria, Penela, Castelo Viegas and the Pereiros formations. Three informal palynological zones have been documented and compared with coeval palynozones from West and South Europe providing new biostratigraphic data to detail the age of the lower and upper formations of the Silves Group and to review previous age attribution. A Norian, possibly earliest Rhaetian age, is documented for the Conraria Formation on the basis of a palynological assemblage referable to the Classopollis meyerianus-Granuloperculatipollis rudis (CG) zone. The Penela and Castelo Viegas formations did not allow a palynostratigraphic revision, due to the not promising lithology for palynological studies. The Pereiros Formation is dated on the basis of microflora assemblages referable, from bottom to top, the Ischyosporites variegatus-Kraeuselisporites reissingeri (IK) zone of late Rhaetian-earliest Hettangian age and Pinuspollenites minimus (Pm) zone of Hettangian age. The discontinuity between the underlying Castelo Viegas Formation and the overlying Pereiros Formation did not allow to define the lower boundary of the IK palynozone. The Triassic-Jurassic boundary lies in the lower part of Pereiros Formation within the IK zone. The microflora assemblages from the Lusitanian Basin show close affinity to those of eastern N America and western Tethys areas. (C) 2021 Elsevier B.V. All rights reserved.
- Palynostratigraphy of the Triassic-Jurassic of the Silves Group, Lusitanian Basin, Portugal [Resumo]Publication . Vilas Boas, Margarida; Pereira, Zélia; Cirilli, Simonetta; Duarte, L. V.; Fernandes, PauloABSTRACT: We studied the miospore assemblage from an Upper Triassic to Lower Jurassic succession of the Silves Group near Coimbra, Portugal. The latter consists of, from base to top, the Conraria, Penela, Castelo Viegas, and the Pereiros formations. The palynological assemblages allowed establishing an informal palynozonation and providing new biostratigraphic that helped constrain the age attribution to the Silves Group formations.
- The effects of the Jenkyns Event on the radiation of Early Jurassic dinoflagellate cystsPublication . Correia, Vânia; Riding, James; Duarte, L. V.; Fernandes, Paulo; Pereira, ZéliaABSTRACT: This contribution is an overview of the Early Jurassic dinoflagellate cysts of the Lusitanian Basin in Portugal, with particular emphasis on the effects of the Jenkyns Event (Toarcian Oceanic Anoxic Event) on the evolution of this planktonic group. We review and discuss data from 214 samples from six Lower Jurassic successions (upper Sinemurian to upper Toarcian) in the Lusitanian Basin. The late Pliensbachian radiation of dinoflagellate cysts was well recognized in this basin. The pre-Jenkyns Event interval is highly productive, with maximum abundance and species richness values. However, this palaeoenvironmental perturbation severely affected the evolution of this group for the remainder of the Early Jurassic. The prolonged recovery of the dinoflagellates in the Toarcian following the Jenkyns Event is not typical of the northern regions (Arctic and Boreal realms), where new species began to evolve earlier compared with southern European basins.
- Preliminary late Miocene palynomorph assemblages from the Quifangondo and Luanda formations, Onshore Kwanza Basin, AngolaPublication . Rodrigues, C.F.; Pereira, Zélia; Mendes, Márcia; Nsungani, P.C.; Fernandes, Paulo; Lopes, Gilda; Duarte, L. V.; Aboelkomsan, W.; Taylor, E.; Tyrrell, M.; Fernando, M. F.; Machado, V.ABSTRACT: A Miocene succession exposed at the Cabo Ledo and Miradouro da Lua sections in the Onshore Kwanza Basin, Angola, was examined for palynology. Palynomorphs of preliminary late Miocene age identified are presented herein. The upper part of the Quifangondo Formation is dated as middle Tortonian in age based on the co-occurrence of the pollen grain Fenestrites spinosus and the dinoflagellate species Selenopemphix armageddonensis. The palynomorph signature indicates a middle neritic marine environment dominated by dinoflagellate cyst taxa. A late Miocene (late Tortonian to Messinian) age is also documented for the first time at the base of the Luanda Formation based on the co-occurrence of the pollen taxa Echitricolporites spinosus, Fenestrites spinosus, Fenestrites longispinosus, Monoporopollenites annulatus, and Retistephanocolpites gracilis. The palynomorph signature of this unit reflects an inner neritic marine (coastal/lagoon transitional) environment dominated by terrestrial palynomorphs and very rare dinoflagellate cyst taxa. The present research contributes data for improving the stratigraphical framework of the Quifangondo and Luanda formations, both of which are recognized as the main potential source rocks and reservoirs of the Post-Salt Paleogene/Neogene Petroleum System of the Kwanza Basin. This significant contribution provides important biostratigraphic and palaeoenvironmental data for defining the vital temporal horizons of these settings in a basin where petroleum exploration is of interest.
- Palynology of the Albian–Turonian sediments from the Sumbe region, Kwanza Basin (Angola): Implications for paleoenvironment, paleoclimate, and paleogeographyPublication . Rodrigues, Cristina F.A.; Mendes, Márcia; Pereira, Zélia; Nsungani, P.C.; Fernandes, Paulo; Duarte, L. V.; Chitangueleca, Belarmino; Sebastião, Lumen; Aida, Benedito; Degli Esposti, Davide; Freitas, DomingosABSTRACT: Palynological investigations in the Sumbe region of the Kwanza Basin, Angola, have identified Albian to Turonian assemblages in four sections of the Quissonde Facies of the Mucanzo, Cabo Ledo, and Itombe formations. These studies aimed to determine their biostratigraphic ages and infer paleoenvironmental, paleoclimatic, and paleogeographic models. The presence of Odontochitina costata, Palaeohystrichophora infusorioides, and Xiphophoridium alatum cysts supports an upper Albian to lower Cenomanian age for the Mucanzo Formation. Litosphaeridium siphoniphorum cyst and the Elateroplicites africaensis pollen found In the Cabo Ledo Formation suggest a Cenomanian age, while Conosphaeridium striatoconum, Heterosphaeridium difficile, and Dinogymnium acuminatum supports a Turonian age for the lower part of the Itombe Formation. All samples predominantly contain fluorescent amorphous organic matter (AOM) derived from phytoplankton degradation, with increasing AOM in the uppermost units, indicating inner neritic marine deposition under dysoxic-anoxic conditions. During the Lower to mid-Cretaceous, the Gondwana breakup caused significant changes, with the palynological indicating a Tethyan affinity with some high-latitude taxa, suggesting a cosmopolitan distribution. The subtropical to tropical nature of the assemblages, along with high-latitude species, indicates a mid-Cretaceous water connection between the Central Atlantic and the South Atlantic oceans, extending to the Kwanza Basin.