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- The first Ichneumonid fossil from the Early Pleistocene of Madeira Island (Portugal)Publication . Góis-Marques, Carlos A.; JESUS, JOSÉ; DE SEQUEIRA, MIGUEL MENEZES; Madeira, JoséIn oceanic islands, well age-constrained deposits containing arthropod somatofossils (body fossils) are rare. However, when available, these are important for providing empirical and independent minimum ages for molecular phylogenetic dating and complementary data on taxonomy, evolution and palaeobiogeography information of the biological groups found as fossils. This is especially important for taxa that speciated within oceanic islands, many becoming single island endemics (SIE). Recently, associated with a 1.3 Ma (Calabrian) fluvial and lacustrine sedimentary deposit from Porto da Cruz in Madeira Island (Fig. 1), a wing, putatively identified as Hymenoptera, was found. Here we describe this wing fossil as belonging to Ichneumonidae, a group with ca. 30% of SIE in Madeira Island. Moreover, this is the first somatofossil of ichneumonid parasitic wasps found in Madeira Island and in Macaronesian islands (i.e. Azores, Madeira, Canaries and Cabo Verde). Since the 19th century, oceanic island attracted several naturalists due to the high probability of finding taxonomical novelties (e.g. Vieira, 2005). Darwin (1859) amplified this interest, as oceanic islands biota presented a central role to explain evolution. Today oceanic islands became the ideal locations to study evolution, biogeography and ecology (e.g. Whittaker et al., 2017). Madeira Island (Central Atlantic Ocean; Fig. 1), geologically a shield volcano of 7 Ma (Ramalho et al., 2015 and references therein), is considered an insect diversity hotspot where 3019 species and subspecies are known, of which 665 are SIE (Borges et al., 2008). This diversity is most probably explained by stepping-stone through palaeo-Macaronesian islands and isolation (Triantis et al., 2010; Fernández-Palacios et al., 2011). Palaeoentomological records are rare in Madeira. The only known record is from the Mio-Pleistocene deposit of São Jorge (see Góis-Marques et al., 2018), where Heer (1857) described an extinct coleopteran, Laparocerus wollastoni, based on fossilized elytra. Machado (2006) in a taxonomic review of Laparocerus considers this taxon as nomen dubium, due to the missing holotype and the impossibility of reapraising its taxonomy. On other Macaronesian archipelagos, especially in the Canaries Islands, several deposits with insect ichnofossils have been described (e.g. Edwards & Meco, 2000; Meco et al., 2011; La Roche et al., 2014). In Azores only xylophagous ichnoentomological traces in charcoal wood are known (Góis-Marques et al., 2019b). The fossil wing was found within laminated lacustrine fine sandstone, associated with plant fossils. The sediments are constrained by two 40Ar-39Ar dates to 1.3 Ma, Calabrian stage (Góis-Marques et al., 2019a). Fossils are kept in the palaeobotanical collection at the Madeira University herbarium (UMad-P) with the numbers UMad-P500a (part) and UMad-P500b (counter-part). The wing fossil was studied under a stereo microscope, and its identification was performed through several sources (e.g. Goulet & Huber, 1993) and specific guidebooks (Prehn & Raper, 2016). Wing description follows the Comstock-Needham system as described by Quicke (2015)
- The Quaternary plant fossil record from the volcanic Islands of Azores (Portugal, North Atlantic Ocean): a reviewPublication . Góis-Marques, Carlos A.; De Nascimento, Lea; Menezes de Sequeira, Miguel; Fernández-Palacios, Jose Maria; Madeira, JoséPlant fossils are known from the Azores Islands, yet poorly studied. We present a comprehensive bibliographical review for the archipelago. A first pre-scientific reference dates from late fifteenth century, while the first scientific description was reported in 1821, accounting for trunks in pyroclastic units and silicified plants within hydrothermal deposits. Throughout the second-half of the nineteenth century and the first-half of the twentieth century, prospection by naturalists and geological mapping work, led to the discovery and description of plant fossils in most islands. From the 1970s onwards, the taxonomic interest ceased, and plant fossils were used mainly for 14C dating. Recently, sediment cores from lakes and peatlands were used for palaeoecological reconstructions and to measure anthropogenic impacts. Generally, plant fossils are younger than 50 ka, although older fossils may exist. Azorean plant fossils include somatofossils of leaves, stems, logs and seeds preserved as impressions, compressions, adpressions, permineralizations, lava tree casts and mummifications. The taphonomy of macrofloral elements is usually related to explosive volcanic activity, while palynological record is associated with lake sediments and peat bogs. The persistence in palaeobotanical and palaeopalynological studies will decisively contribute to disentangle the paleodiversity, palaeoecology, and add crucial information on insular plant phylogeny and biogeography.
- Tracing insular woodiness in giant Daucus (s.l.) fruit fossils from the Early Pleistocene of Madeira Island (Portugal)Publication . Góis-Marques, Carlos A.; De Nascimento, Lea; Fernández-Palacios, Jose Maria; Madeira, José; Menezes de Sequeira, MiguelPlants on oceanic islands can evolve insular syndromes such as secondary woodiness, a generalized trend found in island floras worldwide. This phenomenon occurs through evolution in situ. It is triggered by ecological and physiological stimuli that transform herbaceous annuals into woody perennials. However, well-dated and informative fossils that could help track and frame the evolution of this syndrome are lacking. Remarkably, in Madeira Island (Portugal), there are good examples of Apiaceae that evolved secondary woodiness, like the giant neoendemic Melanoselinum (≡ Daucus). Apiaceae has a very scarce fossil record, despite being a cosmopolitan family and an economically important crop. Here we describe the oldest Daucus s.l. fossil known to date and the first fossil evidence of a plant with insular woodiness. The fossils are preserved as mummified/compressed mericarps within 1.3-million year-old fluvio-lacustrine sediments of the Funchal unit, Upper Volcanic complex, near Porto da Cruz. We assign them to the extant neoendemic species Melanoselinum (≡ Daucus) decipiens. The mericarp morphology shows remarkable stasis since the Calabrian stage of the Early Pleistocene. Our results demonstrate that in the Madeiran Daucinae clade, insular woodiness developed at least 1.3 million years ago, indicating a coeval or earlier immigration to Madeira Island of a Daucus sp. Our results reinforce the role of palaeobotanical research in oceanic islands, supported by stratigraphy and geochronology studies, as a key element for the understanding of plant palaeobiogeography, ecology and evolution worldwide. We expect this contribution to shed light on the evolutionary origins of carrots, and related plant groups, an important element of human food, and to better comprehend the evolution of plant insular woodiness.
- Oceanic Island forests buried by Holocene (Meghalayan) explosive eruptions: palaeobiodiversity in pre-anthropic volcanic charcoal from Faial Island (Azores, Portugal) and its palaeoecological implicationsPublication . Góis-Marques, Carlos A.; Rubiales, Jose M.; de Nascimento, Lea; Menezes de Sequeira, Miguel; Fernández-Palacios, Jose Maria; Madeira, JoséIn Faial Island (Azores Archipelago, North Atlantic Ocean), charcoalified and mummified wood fossils have been reported within late Holocene (Meghalayan) pyroclastic deposits from the Caldeira Formation. Due to their recent age, a detailed study conveys a snapshot into Azorean palaeophytodiversity and palaeovegetation, ca. 7–5 centuries before the arrival of Portuguese settlers to the Azores Islands. Here we provide the first detailed anatomical and taxonomical study of these wood fossils. In total, 41 samples were collected from seven localities, mainly from a ~1200 yr BP ignimbrite. Field work revealed autochthonous and paraautochthonous assemblages, with tree trunks in upright position. The anatomical study of the fossil woods resulted in the identification of Juniperus brevifolia, Laurus azorica, Myrsine retusa, Morella faya, Picconia azorica, Prunus lusitanica subsp. azorica, and Vaccinium cylindraceum. Two fossil assemblages are comparable to the proposed potential natural vegetation (PNV) for the Azores. Surprisingly, P. lusitanica subsp. azorica was the second most abundant fossil wood suggesting that this tree was more abundant in a recent past in Faial Island and probably in the archipelago. This is corroborated by historical accounts, and its modern scarcity was certainly anthropically driven. Identifying Holocene plant macrofossils is essential to properly reconstruct oceanic islands terrestrial palaeoecosystems, especially where forests with high percentage of entomophilous taxa are underrepresented in palaeopalynological limnic record. Further work is necessary to reconstruct Faial Island and Azores archipelago palaeovegetation which is essential to provide an ecosystem base-line for restoration and management.
- Evidence for late Pleistocene volcanism at Santa Maria Island, Azores?Publication . Ramalho, Ricardo Dos Santos; Quartau, R.; Höskuldsson, Ármann; Madeira, José; da Cruz, João Ventura; Rodrigues, AuroraSanta Maria Island constitutes the oldest volcanic island within the Azores Archipelago, with no onshore record of eruptions younger than ≈2.8 Ma. A recent high-resolution multibeam bathymetric survey, however, revealed the presence of a seemingly young submerged wide volcanic edifice at approximately −70/−80 m, on the northeastern sector of the island shelf. The outer flanks of this volcanic edifice are partially eroded by marine erosion, but its general morphology is largely preserved, attesting to its relative youth. The edifice's aspect ratio and crater size are typical of a tuff ring formed by very violent surtseyan to taalian eruptions (with water/magma interaction ratios close to 1), implying extrusion at sea level or in very shallow waters, conditions that are incompatible with the present-day water depth at which this structure occurs. A detailed geomorphological analysis – coupled with a correlation with a modified reference eustatic curve – allowed the formulation and discussion of a formation model for the tuff ring, which involves extrusion during a period immediately preceding a rapid relative sea-level drop, most likely at ≈43 ka. Extrusion during such a period would have allowed for the subaerial consolidation and palagonitization of the tuff ring, increasing its resistance to erosion, before being finally submerged during the Last Glacial Termination. Submersion during the Last Glacial Termination – a period characterised by extremely fast sea-level rise – also helps to explain why this tuff ring was submerged without being completely razed by marine erosion. Our study offers insights on the formation and preservation of tuff rings in coastal environments, and in relation to sea-level oscillations, suggesting that consolidation plays a crucial role in the process. Crucially, our study suggests that Santa Maria's volcanism might have extended well into the very late Pleistocene, raising important hazard implications. Future work is scheduled to confirm this hypothesis, including sampling of the volcanic products by dredging and/or by remote operated vehicle. Our study also emphasises the importance of available high-resolution bathymetric surveys to the formulation of solid volcanic hazard assessments on volcanic islands.
- Investigating collapse structures in oceanic islands using magnetotelluric surveys: The case of Fogo Island in Cape VerdePublication . Martínez-Moreno, F.J.; Monteiro Santos, Fernando Acácio; Madeira, José; Pous, J.; Bernardo, I.; Soares, A.; Esteves, M.; Adão, F.; Ribeiro, J.; Mata, João; Brum da Silveira, A.One of the most remarkable natural events on Earth are the large lateral flank collapses of oceanic volcanoes, involving volumes of rock exceeding tens of km3. These collapses are relatively frequent in recent geological times as supported by evidence found in the geomorphology of volcanic island edifices and associated debris flows deposited on the proximal ocean floor. The Island of Fogo in the Cape Verde archipelago is one of the most active and prominent oceanic volcanoes on Earth. The island has an average diameter of 25 km and reaches a maximum elevation of 2829 m above sea level (m a.s.l.) at Pico do Fogo, a young stratovolcano located within a summit depression open eastward due to a large lateral flank collapse. The sudden collapse of the eastern flank of Fogo Island produced a megatsunami ~73 ky ago. The limits of the flank collapse were deduced as well from geomorphologic markers within the island. The headwall of the collapse scar is interpreted as either being located beneath the post-collapse volcanic infill of the summit depression or located further west, corresponding to the Bordeira wall that partially surrounds it. The magnetotelluric (MT) method provides a depth distribution of the ground resistivity obtained by the simultaneous measurement of the natural variations of the electric and magnetic field of the Earth. Two N-S magnetotelluric profiles were acquired across the collapsed area to determine its geometry and boundaries. The acquired MT data allowed the determination of the limits of the collapsed area more accurately as well as its morphology at depth and thickness of the post-collapse infill. According to the newly obtained MT data and the bathymetry of the eastern submarine flank of Fogo, the volume involved in the flank collapse is estimated in ~110 km3. This volume –the first calculated onshore– stands between the previously published more conservative and excessive calculations –offshore– that were exclusively based in geomorphic evidence. The model for the summit depression proposing two caldera collapses preceding the collapse of the eastern flank of Fogo is supported by the MT data.
- A geological record of multiple Pleistocene tsunami inundations in an oceanic island: The case of Maio, Cape VerdePublication . Madeira, José; Ramalho, Ricardo Dos Santos; Hoffmann, Dirk L.; Mata, João; Moreira, Mário Augusto de AndradeIn the Central Atlantic archipelagos – the Canaries, Cape Verde, Madeira and the Azores – tsunami hazard is often regarded as low, when compared with other extreme wave events such as hurricanes and storms. The geological record of many of these islands, however, suggests that tsunami hazard may be underestimated, notwithstanding being lower than in areas adjacent to subduction zones, such as the margins of the Pacific and Indian oceans. Moreover, tsunamis in oceanic islands are generally triggered by local large-scale volcanic flank collapses, for which little is known about their frequency, making it difficult to estimate the probability of a new occurrence. Part of the problem lies in the fact that tsunami deposits are usually difficult to date, and few islands in the world exhibit evidence for repeated tsunami inundation on a protracted timescale. This study reports on the presence of abundant tsunami deposits (conglomerates and sandstones) on Maio Island (Cape Verde) and discusses their stratigraphy, sedimentological characteristics, probable age and tsunamigenic source. Observations indicate that four distinct inundation events of variable magnitude took place during the Pleistocene. One of the tsunami deposits yielded a high-confidence U/Th age of 78.8 +- 0.9 ka, which overlaps within error with the 73 +- 7 ka age proposed for Fogo volcano’s flank collapse, an event known to have had a significant tsunami impact on nearby Santiago Island. This shows that the Fogo tsunami also impacted Maio, resulting in runups in excess of 60 m above coeval sea-level at ca 120 km from the source. Two older deposits, possibly linked to recurrent flank collapses of the Tope de Coroa volcano in Santo Antão Island, yielded lower-confidence ages of 479 to 390 ka and 360 to 304 ka. A younger deposit (<78 ka) remains undated. In summary, the geological record of Maio exhibits well-preserved evidence of repeated tsunami inundation, reinforcing the notion that tsunami hazard is not so low at volcanic archipelagos featuring prominent and highly-active volcanoes such as in Cape Verde.
- Megatsunamis Induced by Volcanic Landslides in the Canary Islands: Age of the Tsunami Deposits and Source LandslidesPublication . Ferrer, Mercedes; González de Vallejo, Luis; Madeira, José; Andrade, César; García-Davalillo, Juan C.; Freitas, Maria Da Conceição; Meco, Joaquín; Betancort, Juan F.; Torres, Trinidad; Ortiz, José EugenioEvidence for frequent, large landslides on the flanks of the volcanic edifices forming the Canary Islands include outstanding landslide scars and their correlative submarine and subaerial rock and debris avalanche deposits. These landslides involved volumes ranging from tens to hundreds of km3. The sudden entry of large volumes of rock masses in the sea may have triggered tsunamis capable of affecting the source and neighboring islands, with the resulting huge waves dragging coastal and seabed materials and fauna and redepositing them inland. Here, we present new geological evidence and geochronological data of at least five megatsunamis in Tenerife, Lanzarote, and Gran Canaria, triggered by island flank megalandslides, and occasionally explosive eruptions, during the last 1 million years. The exceptional preservation of the megatsunami deposits and the large area they cover, particularly in Tenerife, provide fundamental data on the number of tsunami events and run-ups, and allow proposals on the sources and age of the tsunamis. Tsunami run-up heights up to 290 m above coeval sea level, some of the highest known on Earth in recent geological times, were estimated based on sedimentological, geomorphological, paleontological, and geochronological data. The research results made it possible to estimate the recurrence of tsunamis in the archipelago during the last hundreds of thousands of years, and to establish relationships between tsunami deposits and the probable triggering island flank landslides.
- The bicentenary of Georg Hartung, a German pioneer geologist, explorer, and illustratorPublication . Góis-Marques, Carlos A.; Menezes de Sequeira, Miguel; Madeira, JoséWe present a tribute to Georg Friedrich Karl Hartung (1821–1891), a less-known, non-academic German geologist, on his 200th birthday anniversary. Influenced by eminent 19th century scientific personalities, such as Oswald Heer, Charles Lyell, and Alexander von Humboldt, he performed pioneer geological observations and sampling in the Azores, Madeira, and Canary Islands volcanic archipelagos. Later in his life, he travelled to the USA and explored the Scandinavian countries. His scientific endeavours were published in several books and papers, many of them co-authored by academic German geologists and palaeontologists. His works on Macaronesia are deemed as classics, and many have been enriched by his detailed geological illustrations.
- Physical volcanology and emplacement mechanism of the Central Atlantic Magmatic Province (CAMP) lava flows from the Central High Atlas, MoroccoPublication . El Hachimi, Hind; Youbi, Nasrrddine; Madeira, José; Marzoli, Andrea; Mata, João; Bertrand, Hervé; Bensalah, Mohamed Khalil; Boumehdi, Moulay Ahmed; Doblas, Miguel; Medina, Fida; Ben Abbou, Mohamed; Martins, LíniaThe best preserved and most complete lava flow sequences of the Central Atlantic Magmatic Province (CAMP) in Morocco are exposed in the Central High Atlas and can reach up to 300 m in thickness. Four distinct formations, emplaced in subaerial environments, are classically recognized: the Lower, Intermediate, Upper and Recurrent formations. These formations are separated by paleosoils and sedimentary sequences (mudstones, siltstones, sandstones, limestones), that are in general less than two meter-thick and may exceptionally reach a thickness of 80 m, representing minor periods of volcanic quiescence. CAMP lava flows of the Central High Atlas can be grouped into two main categories: subaerial compound pahoehoe flows and simple flows. The former type is exclusively confined to the Lower and Intermediate Formations, while simple flows occur in the Upper and Recurrent Formations. The dominance of compound flows in the two lowermost units of the CAMP suggests a slow emplacement during successive sustained eruptive episodes. Instead the thick single flows characterizing the Upper and Recurrent units indicate higher effusive rates. Basaltic pillow lavas (always of short lateral extent: 10 to 100 m), showing radial jointing and vitreous rinds, identical to those found in the Western Meseta, are occasionally associated with hyaloclastites in the base of the Intermediate Formation, immediately above clastic sediments, or in the Upper Formation. The occurrence of pillow lavas does not imply a generalized subaqueous environment at the time of the lava emission. Instead, they represent subaerial flows that entered small lakes occupying depressions on the volcanic topography of the Lower and Intermediate Formations. The short lateral extent of the pillow lavas and their constant stratigraphic position, the existence of lava flows with unequivocal subaerial characteristics associated to sediments containing fossilized wood, clearly indicate onshore emplacement.