Browsing by Author "Cirilli, Simonetta"
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- Assessing Thermal Maturity through a Multi-Proxy Approach: A Case Study from the Permian Faraghan Formation (Zagros Basin, Southwest Iran)Publication . Spina, Amália; Cirilli, Simonetta; Sorci, Andrea; Schito, Andrea; Clayton, Geoff; Corrado, Sveva; Fernandes, Paulo; Galasso, Francesca; Montesi, Giovanni; Pereira, Zélia; Rashidi, Mehrab; Rettori, RobertoABSTRACT: This study focuses on the thermal maturity of Permian deposits from the Zagros Basin, Southwest Iran, employing both optical methods (Thermal Alteration Index, Palynomorph Darkness Index, Vitrinite Reflectance, UV Fluorescence) and geochemical analyses of organic matter (Rock Eval Pyrolysis and MicroRaman spectroscopy) applied to the Faraghan Formation along two investigated Darreh Yas and Kuh e Faraghan surface sections. Furthermore, an integrated palynofacies and lithofacies analysis was carried out in order to integrate the few studies on the depositional environment. The Faraghan Formation, which is widely distributed in the Zagros area, generally consists of shale intercalated with sandstones and pebble conglomerates in the lower part, followed by a succession of sandstone, siltstone and shaly intercalations and with carbonate levels at the top. The integrated palynofacies and lithofacies data confirm a coastal depositional setting evolving upwards to a shallow marine carbonate environment upwards. Rock Eval Pyrolysis and Vitrinite Reflectance analysis showed that the organic matter from samples of the Darreh Yas and Kuh e Faraghan sections fall in the mature to postmature range with respect to the oil to gas generation window, restricting the thermal maturity range proposed by previous authors. Similar results were obtained with MicroRaman spectroscopy and optical analysis such as Thermal Alteration Index and UV Fluorescence. Palynomorph Darkness Index values were compared with Rock Eval Pyrolysis and vitrinite reflectance values and discussed for the first time in the late stage of oil generation.
- 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.
- New Insights on the Upper Triassic Silves Group in Algarve Basin, Portugal: Palynological, paleophytogeography and paleoclimatology advancesPublication . Vilas Boas, Margarida; Pereira, Zélia; Cirilli, Simonetta; Fernandes, PauloABSTRACT: This paper presents the results of palynostratigraphic studies in the Silves Group in the Algarve Basin, Portugal. From bottom to top comprises the Silves Sandstones, the Silves Marl-Carbonate Evaporitic Complex, and the Volcano-Sedimentary Series. This study aims to detail the age of the Silves Group, bracketing the Triassic-Jurassic transition, using palynology. For this purpose, 250 samples were collected from 14 main sections. Previous results from a section above the Variscan unconformity, enabled to date the base of the Silves Sandstones and the onset of the Mesozoic sedimentary cycle in the Algarve Basin to lower Carnian. In this work, the top of the Silves Sandstones, containing Camerosporites secatus, Enzonalasporites vigens, Granuloperculatipollis rudis, Lagenella martinii, Patinasporites densus, Samaropollenites speciosus, and Vallasporites ignacii, is dated to the upper Carnian. The base of the Silves Marl-Carbonate Evaporitic Complex, consisting of Alisporites sp., Araucariacites australis, Classopollis meyerianus, Classopollis torosus, Paracirculina quadruplicis and Triadispora sp., indicates an upper Carnian age. The presence of Alisporites diaphanus, Araucariacites australis, Cerebropollenites macroverrucosus, Classopollis meyerianus, Classopollis torosus, Perinopollenites elatoides, Calamospora mesozoica, and Kraeuselisporites reissingeri allows to date the top of the Silves Marl-Carbonate Evaporitic Complex as upper Rhaetian-lower Hettangian. This study allows to date the Silves Group in the Algarve Basin from the lower Carnian to lower Hettangian (Triassic-Jurassic boundary) for the first time. The Carnian microflora provides new insights of the Onslow Microflora in the Western Tethys.
- New palynostratigraphical data of the Silves Group, Algarve BasinPublication . Vilas Boas, Margarida; Fernandes, Paulo; Pereira, Zélia; Cirilli, SimonettaSUMÁRIO: Este trabalho mostra dados palinostratigráficos que permitem aperfeiçoar a idade do Grupo de Silves na Bacia do Algarve. O Grupo de Silves constitui a unidade sedimentar mais antiga desta bacia e foi depositado de forma discordante sobre os turbiditos do Carbonífero superior da Formação Brejeira, dobrados e falhados durante a Orogenia Varisca. Os novos dados obtidos, permitem-nos apontar o início da sedimentação na Bacia do Algarve ao Carniano inferior e datar de idade Carniano todo o pacote sedimentar correspondente aos “Arenitos de Silves”. As camadas da base do “Complexo Margo-Carbonatado de Silves” correspondem ao Carniano superior, e os evaporitos possuem idade compreendida entre o Retiano superior e a base do Hetangiano, representando assim o limite entre o Triássico e o Jurássico, na bacia.
- 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.
- 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 age of the first pulse of continental rifting associated with the breakup of Pangea in Southwest Iberia: new palynological evidencePublication . Vilas Boas, Margarida; Paterson, Niall W.; Pereira, Zélia; Fernandes, Paulo; Cirilli, SimonettaABSTRACT: In this work, we report the first palynological age for the base strata of the Silves Sandstones of the Silves Group in the Algarve Basin, located in Southern Portugal. The group is the oldest sedimentary unit of the Algarve Basin and was deposited unconformably over late Pennsylvanian turbidites of the Mira Formation, which were folded and faulted during the Variscan Orogeny. The Silves Group comprises a detrital red bed succession, representing the earliest phase of sedimentation associated with the initial rifting of Pangaea. Macrofossils are rare, occurring predominantly in the top layers of this group, and do not accurately constrain the age of the entire group's deposition. From an outcrop exposed in the central Algarve, a grey mudstone bed positioned 2.5 m above the Variscan unconformity plane yielded palynomorphs that date the beginning of sedimentation in this basin to the early Carnian age (Late Triassic). The moderately well preserved and low-diversity palynological association comprises Aulisporites astigmosus, Enzonalasporites densus, Ovalipollis pseudoalatus, Samaropollenites speciosus, Tulesporites briscoensis and Vallasporites ignacii, among others, and is indicative of an early Carnian age.