Browsing by Author "Mendes, Márcia"
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- The age and depositional environments of the lower Karoo Moatize Coalfield of Mozambique: insights into the postglacial history of central GondwanaPublication . Fernandes, Paulo; Hancox, Philip John; Mendes, Márcia; Pereira, Zélia; Rodrigues Lopes, Gilda Maria; Marques, João; Jorge, Raul Carlos Godinho Santos; Albardeiro, LuísThe Moatize Coalfield belongs to a network of continental Karoo basins of central Mozambique, known as the Zambezi Basin. Palynological and sedimentological studies were performed on four coal exploration boreholes to determine the age, depositional settings, and overall geological evolution of its extensive coal deposits. Clastic formations recognised in this coalfield, in ascending order, are the Vu´zi, Moatize and Matinde formations. Palynomorph assemblages indicate that the Moatize Coalfield succession ranges from Roadian (lower Guadalupian) to Changhsingian (upper Lopingian) in age. Two main depositional phases are identified, whose initiation and development are attributed to regional tectonic events and climate amelioration. The first phase formed towards the end of the deglacial period, characterised initially by fan deltas, represented by the upper Vu´zi Formation, and the shift to lake–delta environments, represented by the lower part of the Moatize Formation. This phase took place from Roadian to the Wordian times. The lake–delta settings indicate a sediment aggradation trend with high subsidence rates in the lake basin, which, together with the associated post-glacial climate amelioration, led to the accumulation of coal deposits in swamps of the delta top and lake margins. The second depositional phase took place from Capitanian to Changhsingian times and related to fluvial environments initiated by uplift that reorganised the depocenter into alluvial plains characterised by bedload dominated rivers (braided) and overbank floodplains. Results obtained in this study provide critical information for the onset of the deglaciation events and the age of coal deposits in this part of Gondwana, important for wider stratigraphic correlation of these events in Africa and throughout the Gondwana.
- Multidisciplinary palaeoenvironmental characterisation of the late Permian Matinde Formation, MozambiquePublication . Lopes, Gilda; Pereira, Zélia; Fernandes, Paulo; Mendes, Márcia; Marques, João; Jorge, Raul C.G.S.The Muarádzi Sub-basin is part of the Moatize-Minjova Basin (MMB), an important Karoo aged coalfield in Tete Province, Mozambique. It is a WNW-ESE trending, elongated sedimentary basin located in the eastern part of the MMB, whilst during the late Permian was situated in the southern-central part of Gondwana. In this study, we undertook a multidisciplinary approach involving the lithological, palynofacies, and palynological analysis of samples collected from 3 coal exploration boreholes (DW11, DW21, and DW141) collected from this sub-basin. A total of 99 core samples were collected and studied, allowing for the characterisation of depositional environments and existing palaeofloras for this sub-basin.
- A new approach to palynostratigraphy of the middle–late Famennian Gafo Formation, southern sector of the Pulo do Lobo Domain, SW Iberia (Portugal and Spain)Publication . Mendes, Márcia; Pereira, Zélia; Vaz, Nuno; Díez-Montes, Alejandro; Matos, João X.; Albardeiro, Luis; Manuel Carvalho Fernandes, Paulo; Jorge, Raul; Chew, DavidNew palynological results from the Gafo Formation (southern sector of the Pulo do Lobo Domain, South Portuguese Zone) are integrated with recently studied sections and drillholes from the Portuguese and Spanish sectors. A total of 44 samples were studied, 27 of which were positive for palynomorph taxonomy. This research revealed well preserved palynological assemblages, including 73 spore species allocated to 28 genera, four acritarch genera, three prasinophyte algae genera plus common chitinozoan remains. Some additional forms were retained under open nomenclature. From this, the first complete age determination for the Gafo Formation in Portugal and Spain was achieved, indicating a middle Famennian (Grandispora gracilis–Grandispora famenensis, GF Biozone) to a late Famennian (Grandispora echinata, VH Biozone) age. A greywacke sample from the same Gafo Formation was dated by U–Pb zircon geochronology and a maximum depositional age of 369 ± 2.5 Ma was obtained. A correlation between these palynological and U–Pb zircon data and the palynoflora assemblages of previous authors was made, as well as with the ages of felsic volcanic rocks found intercalated in the Gafo Formation, confirming the complex stratigraphy of Pulo do Lobo Domain. The results are consistent with stratigraphic mapping and structural interpretations, allowing a middle–late Famennian age (GF and VH Biozone) to be assigned to the Gafo Formation sedimentary rocks. This work has also contributed to a reinterpretation of Gafo Formation depositional facies correlatives (e.g. the Santa Barbara Group in Spain) as being the same lithological unit.
- Palynology of the Albian–Turonian sediments from the Sumbe region, Kwanza Basin (Angola): Implications for paleoenvironment, paleoclimate, and paleogeographyPublication . Rodrigues, Cristina; Mendes, Márcia; Pereira, Zélia; Nsungani, Pedro Claude; Fernandes, Paulo; Duarte, Luís Vítor; Chitangueleca, Belarmino; Sebastião, Lúmen; Aida, Benedito; Esposti, Davide Degli; Freitas, DomingosPalynological 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. (c) 2024 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
- The paleoenvironmental and thermal histories of the permian Irati formation shale in the Paraná Basin, Brazil: an integrated approach based on mineralogical and organic imprintsPublication . Rocha, Haline V.; Sant’Anna, Lucy G.; Rodrigues, Cristina F.A.; Mendes, Márcia; Pereira, Zélia; Lopes, Gilda; Fernandes, Paulo; Pereira, Egberto; Tassinari, Colombo C.G.; Lemos de Sousa, Manuel J.Mineralogical assemblages and organofacies are important sources of information to recover the paleoenvir-onmental and thermal histories of shale deposits. In this study, a detailed qualitative and quantitative charac-terization of the Permian Irati Formation (Assistencia Member) shale is based on mineralogical (XRD and SEM -EDS) and organic components (TOC, Rock-Eval pyrolysis, organofacies, TAI, fluorescence and vitrinite reflec-tance measurements) and provides integrated data about sediment provenance, depositional environment, diagenesis, and thermal history, while supporting interpretations on the Paran & PRIME;a Basin (PB), Brazil, paleogeog-raphy and its correlation to the southwest Gondwana. The results revealed a prevailing type I/II kerogen, with type III kerogen being also present but mainly confined along the paleoshoreline of the PB. The dominance of fluorescent amorphous organic matter (AOM) combined with framboidal pyrite suggests microbial activity in an anoxic-dysoxic neritic-marine paleoenvironment. Additionally, common to abundant well-preserved phytoclasts, as well as the occurrence of Botryococcus braunii, indicates freshwater influx in a brackish marine depositional setting. Immature to early-oil window thermal maturities prevail across the PB, according to the organic maturation indicators. The combined analysis between the organic matter evolution with clay mineralogy, such as the occurrence of interstratified clays (e.g., I/S) and its positive correlation with depth suggest that burial diagenesis reached the transition to early catagenesis on the north, southeast, and south of the basin, attributing a shale oil potential for the Irati Formation on a regional scale. Local scale imprints of the Early Cretaceous Paran & PRIME;a-Etendeka Large Igneous Province (LIP), and its thermal effect in the Irati Formation shale components, are recorded as clay authigenesis (e.g., smectite webby texture and clay coating development), crystallization of minerals by low to high-grade of thermal alteration (e.g., corrensite, talc, lizardite and diopside), and by local scale gas-window maturities. Such thermal alteration, identified in the proximity to intruded sills and dykes, led to a heterogeneous organic maturation pattern with implications on shale gas and shale oil potential of the Irati Formation shale, demonstrating that these subjects in the Paran & PRIME;a Basin should be assessed locally.
- The upper Hauterivian–Barremian (Lower Cretaceous) Arrifes section (Algarve Basin, Southern Portugal): A palynostratigraphic and palaeoenvironmental approachPublication . Mendes, Márcia; Descamps, Gabrielle S.; Fernandes, Paulo; Lopes, Gilda; Jorge, Raul Carlos G.S.; Pereira, ZéliaIntegrated sedimentological, palynological, and palynofacies analyses of the Arrifes section in the central Algarve Basin (southern Portugal) provided new information on the age and environments of this Lower Cretaceous sequence. The sedimentary succession at the Arrifes section consists of fossiliferous inter-bedded limestones, marly limestones, and marls, dated as latest Hauterivian to late Barremian age (Lower Cretaceous) based on key dinoflagellate taxa. During this interval, the Arrifes area records cli-matic shifts and, multiple sea-level fluctuations; overall deposition was in shallow subtidal to intertidal settings, with deposition of carbonate and marly sediments. During the latest Hauterivian to earliest Barremian interval, an evident sea-level fall culminated in the subaerial exposure of the local carbonate ramp with increased influx of clastic sediments. However, during the Barremian, both sedimentological and palynological analyses suggest an overall deepening of the water depth towards the top of the section. These overall increase in the water column are confirmed by oscillation of terrestrial/marine palynomorph groups and supported by dinosaur track levels at the top of the succession; the latter indicate that sedimentation occurred in intertidal to subtidal environments. Finally, an attempt was made to correlate the Arrifes section with other sections from the Algarve Basin, as well as with broader region. These new data suggest a setting in the Tethyan basin influenced during the latest Hauterivian to the end of the Barremian. These new data allow local correlations and new palynological ages and paleoenvironmental interpretations for the Lower Cretaceous succession of the Algarve Basin.(c) 2022 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).