Fernando Rocha
Fernando Rocha is Professor of Mineral Resources at the University of Aveiro (Portugal), being the Director of Geobiotec Research Centre. His research is focused on clay minerals, industrial minerals in general and traditional building materials, with Medical Geology, Coastal and Marine Geology as secondary interests, having published 393 full papers (154 in Web of Science indexed journals).
ResearcherID: A-4532-2009
Scopus Author ID 8626859600
ORCID: 0000-0002-3636-3933
ResearcherID: A-4532-2009
Scopus Author ID 8626859600
ORCID: 0000-0002-3636-3933
less
Related Authors
Interests
Uploads
Papers by Fernando Rocha
de Roma. Procurou-se assim compreender melhor a identidade cultural dos indivíduos que viveram numa determinada área territorial, apelidada de Baeturia Celtica pelos autores clássicos, num período de importantes alterações sociais e politicas, que se desenvolveram de forma bastante complexa e em múltiplas orientações, quer nas etapas que estabelecem tradicionalmente a segunda Idade do Ferro, quer na efectiva mudança que se opera nas vésperas da nossa Era.
In this work, the first results of ice rafted detritus (IRD) provenance related to Heinrich Events in the NW Iberian Margin are presented and discussed. This study is based on multi-proxies, namely on thorough analyses of Sr and Nd isotope ratios measured in the detrital fraction of the sediment core KC 024-19, from the Galician continental slope (NE Atlantic), aiming to unravel the sources of the terrigenous component of the sampled sediments.
In most of the core layers, the isotope signatures are consistent with an origin, ultimately, in the nearby Variscan continental crust. However, allochthonous contributions were also deposited, namely during the last four Heinrich Events (HE). The non-carbonate detrital fraction of the sediments deposited during the HE1 (in its upper part), HE2, and HE4 displays 3Nd much lower than usual, suggesting that those layers incorporate clasts dropped by icebergs (Ice-Rafted Detritus e IRD) whose sources must have been located in Archaean cratons, such as those of northeastern America and Greenland. The low-3Nd values combined with dolomite peaks support the hypothesis that icebergs fed by the Laurentide ice sheet and launched through Hudson Strait played a major role in the deposition of IRD during HE1, HE2, and HE4. The HE1 layer seems to record a complex evolution of this event, since, at its base, the coarse- grained non-carbonate fraction displays relatively high-3Nd values, pointing to European/Icelandic sources for the icebergs in the initial stages of HE1. The IRD content of the HE3 contrasts significantly with the other HE layers and the non-IRD layers because it has an isotope signature characterized by low 87Sr/86Sr ratios and high-3Nd values. This suggests that the most exotic components of the HE3 layer may have come from East Greenland e Fram Strait and/or result from a mixture of materials from western European and more juvenile (Iceland e Faeroes) crustal sources.
Authors: Virgínia Martins; Fernando Rocha; Cristina Sequeira; Paula Martins; José Santos; João A. Dias; Olivier Weber; Jean-Marie Jouanneau; Belén Rubio; Daniel Rey; Ana Bernabeu; Eduardo Silva; Lazaro Laut; Rubens Figueira
This work aims to study recent climatic oscillations and their influence on sedimentation in the Ria de Vigo, a coastal embayment in Galicia, NW Spain. It is based on the study of clay mineral assemblages, in conjunction with other proxies (granulometric, geochemical, geochronological and microfaunal), in the core KSGX 24. A Benthic Foraminifera High Productivity (BFHP) proxy was used to determine changes in the flux of organic matter (OM) at the bottom of the study area. Total organic carbon (TOC) content is not a suitable proxy to estimate changes in the past supply of OM due to diagenetic processes. The sedimentation was finest in 3 sections: ~ 230–214 cm, ~ 185–73 cm and ~ 20–0 cm. These muddy sections are characterised, in general, by higher proportions of detrital minerals, concentrations of several chemical elements related to lithogenic sources and BFHP values. In addition, these sections are impoverished in carbonates, Ca, Sr and La when compared with the layers with the highest sand content. The clay mineral assemblage of the studied site, characterised by the dominance of illite, intermediate concentrations of kaolinite and minor amounts of smectite and chlorite, reveals the prevalence of a typical temperate humid climate in the last 3 ka BP, the estimated age for the core base. However, the quantities of illite and chlorite increase in the muddy layers. The characteristics of these muddy layers were interpreted as representing relatively cold climatic oscillations associated with the strengthening of northerly winds and the prevalence of an upwelling regime corresponding to well-known periods, such as the first cold period of the Upper Holocene (~ 2.9 ka cal BP), the Dark Ages (between ~ 2.2 - 1.2 ka cal BP) and the Little Ice Age (~ 0.6 ka cal BP).