ORCID Profile
0000-0001-7825-3858
Current Organisation
Universidade de Lisboa
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Publisher: Elsevier BV
Date: 2018
DOI: 10.1016/J.MARPOLBUL.2017.10.087
Abstract: Past climate changes provide important clues for advancement of studies on current global change biology. We have tested large-scale biogeographic patterns through four marine groups from twelve Atlantic Ocean archipelagos and searched for patterns between species richness/endemism and littoral area, age, isolation, latitude and mean annual sea-surface temperatures. Species richness is strongly correlated with littoral area. Two reinforcing effects take place during glacial episodes: i) species richness is expected to decrease (in comparison with interglacial periods) due to the local disappearance of sandy/muddy-associated species ii) because littoral area is minimal during glacial episodes, area per se induces a decrease on species richness (by extirpation/extinction of marine species) as well as affecting speciation rates. Maximum speciation rates are expected to occur during the interglacial periods, whereas immigration rates are expected to be higher at the LGM. Finally, sea-level changes are a paramount factor influencing marine bio ersity of animals and plants living on oceanic islands.
Publisher: Copernicus GmbH
Date: 28-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-10397
Abstract: & & The Cabo Verde Archipelago holds a remarkable sedimentary record of tsunami inundations, as highlighted by recent finds on Santiago and Maio Islands. Santiago, in particular, constitutes an exceptional site to study in detail the proximal impacts of the megatsunami(s) triggered by the well-known catastrophic flank collapse of Fogo volcano (~60 km to the west of this island) and one of the most active ocean island volcanoes in the Atlantic. Previous studies identified and documented deposits & #8211 fields of megaclasts and chaotic conglomerates on northern Santiago & #8211 which were attributed to the impact of this megatsunami(s) moreover, the pioneer use of cosmogenic & sup& & /sup& He geochronology on basaltic megaclasts quarried/displaced by the event bracketed its occurrence within the 65-84 ka time interval. Here we present the results of a recent study conducted within the remit of the project UNTIeD, which combined detailed field surveys and U-Th disequilibrium geochronology to review and further document the tsunamigenic conglomerates of Santiago and gain additional insights into their formative event(s). We can confirm the presence of tsunami conglomerates on several sectors of the island, chiefly in the north and southeast of the island. Furthermore, on the northern sector, our study suggests the presence of two distinct sets of deposits, of differing ages, as corroborated by U-Th geochronology on corals entrained in the conglomerates. The older set of deposits is restricted to 60& #8211 m in elevation and yielded coral ages at the upper limit of U-Th techniques (200-450 ka) its origin is still uncertain. The younger and most widespread chaotic deposit can be found from 0 to 100 m in elevation, is poorly consolidated, and mostly mantles a topography partially carved on the older deposit. Coral ages are very widespread from ~58 to & ka (as commonly observed in tsunami deposits) but with the higher-confidence younger ages clustering around 58-65 ka, in agreement with the youngest cosmogenic ages. This suggests a more constricted timing for Fogo's (main) megatsunami at around 58-65 ka, in close agreement with recent studies at Fogo. A distinct and younger deposit, of Holocene age, can only be found at low elevations in Nossa Senhora da Luz Bay and likely represents a local event possibly triggered by a small submarine landslide. Taken together, these finds not only provide a better time constraint and insights on the impact of Fogo's megatsunami but reinforce the notion that the Cabo Verde Islands have been impacted by multiple tsunamis in the last 500 ka.& & & & This work was supported by project PTDC/CTA-GEO/28588/2017 - LISBOA-01-0145-FEDER-028588 UNTIeD, co-funded by the ERDF through POR Lisboa 2020 and FCT, and by projects IF/01641/2015 MEGAWAVE and FCT/UIDB/50019/2020 - IDL, also funded by FCT.& &
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-10423
Abstract: & & The world-wide study of the geological record of the Last Interglacial is key to reconstruct the climatic and oceanographic conditions during that time interval. Here we present preliminary results of a comprehensive field analysis of one of the most extensive and least studied Quaternary fossiliferous sequences in Cabo Verde attributed to the Last Interglacial. It is located at Nossa Senhora da Luz, which is a protected inlet at the SE coast of Santiago Island. The studied sequence shows a set of transitions between fluvial and marine environments, and emersion and immersion events within a confined, highly protected bay environment. The presence, in the upper part of the sequence, of a thick layer of very fine-branched rhodoliths indicates particular ecological conditions within this bay (e.g., shallow and turbidity free waters, stable environmental conditions and/or fast growth) that are absent today and presumably played an important role for the presence of particular invertebrate species during that time. The presence of tidal specimens of the clam & em& Senilia senilis& /em& in life position at an altitude of ~12m above sea-level allowed a re-interpretation of relative sea-level changes, suggesting that the uplift trend of Santiago Island for the Last Interglacial period onwards (3m/100ky) is possibly 70% lower than previously calculated (10m/100ky). Fossils include five phyla, with molluscs being the most erse and abundant. Despite the abundance of some species (e.g., the bivalves & em& Saccostrea cuccullata& /em& , & em& S. senilis& /em& , and & em& Aequipecten opercularis& /em& , and the gastropods & em& Persististrombus latus& /em& and & em& Thais nodosa& /em& ), the general bio ersity is low. The presence of & em& S. cuccullata& /em& and & em& S. senilis& /em& , absent from extant Cabo Verdean faunas, indicates a more humid climate, unlike the dry climate found today. Some horizons are intensively bioturbated with the crustacean burrow & em& Thalassinoides suevicus& /em& . Our new data agree with the hypothesised palaeoclimatic framework of more wet conditions than today for the Last Interglacial in the archipelago.& & & & Keywords: Eemian, Cabo Verde Archipelago, sheltered bay, & em& Senilia senilis& /em& , volcanic oceanic islands, NE Atlantic& & & & & strong& Acknowledgments& /strong& & & & & C.S.M. and A.C.R. acknowledge, respectively, his PhD grant M3.1.a/F/100/2015 from FRCT/A& #231 ores 2020 and her Post-Doc grant SFRH/BPD/117810/2016 by FCT. R.R. and S.& #193 . acknowledges his IF/01641/2015 and IF/ 00465/2015 grants funded by FCT. A.R. and M.R. were supported by the by DFG grant RA1597/3-1. This work was supported by FCT project PTDC/CTA-GEO/28588/2017 and LISBOA-01-0145-FEDER-028588 UNTIeD and DRCT 2019-2022 & #8211 ACORES-01-0145_FEDER-000078 & #8211 VRPROTO.& &
No related grants have been discovered for Carlos Melo.