DSpace Collection:https://hdl.handle.net/10316/742024-03-29T06:53:19Z2024-03-29T06:53:19ZThe timing of the deglaciation in the Atlantic Iberian mountains: Insights from the stratigraphic analysis of a lake sequence in Serra da Estrela (Portugal)Hernández, ArmandSáez, AlbertoSantos, Ricardo N.Rodrigues, TeresaMartin‐Puertas, CeliaGil‐Romera, GracielaAbbott, MarkCarballeira, RafaelCosta, Pedro J. M.Giralt, SantiagoGomes, Sandra D.Griffore, MelissaIbañez‐Insa, JordiLeira, ManelMoreno, JoãoNaughton, FilipaOliveira, DulceRaposeiro, Pedro M.Trigo, Ricardo M.Vieira, GonçaloRamos, Alexandre M.https://hdl.handle.net/10316/1141722024-03-25T10:55:29Z2023-01-01T00:00:00ZTitle: The timing of the deglaciation in the Atlantic Iberian mountains: Insights from the stratigraphic analysis of a lake sequence in Serra da Estrela (Portugal)
Authors: Hernández, Armand; Sáez, Alberto; Santos, Ricardo N.; Rodrigues, Teresa; Martin‐Puertas, Celia; Gil‐Romera, Graciela; Abbott, Mark; Carballeira, Rafael; Costa, Pedro J. M.; Giralt, Santiago; Gomes, Sandra D.; Griffore, Melissa; Ibañez‐Insa, Jordi; Leira, Manel; Moreno, João; Naughton, Filipa; Oliveira, Dulce; Raposeiro, Pedro M.; Trigo, Ricardo M.; Vieira, Gonçalo; Ramos, Alexandre M.
Abstract: Understanding the environmental response to the last glacial termination in regions
located in transitional climate zones such as the Atlantic Iberian mountains is crucial
to estimate potential changes in regions affected by current glacial melting. We present
an 8.5 m-long, solid last deglaciation and Holocene chronostratigraphic record
including detailed sediment analysis from Lake Peix˜ao, a pro-glacial lake in the Serra
da Estrela (Central Portugal). The age–depth model relies on a Bayesian approach
that includes 16 AMS 14C dates and 210Pb–137CS measurements, robustly dating the
lake formation at 14.7 ± 0.32 cal. ka BP. This chronological reconstruction shows an
average sedimentation rate of ca. 0.07 cm yr 1 (15 yr cm 1), enabling proxy analyses
at decadal timescales. The sediment sequence is composed of five lithological units:
(U1) coarse and unsorted fluvioglacial lacustrine deposits; (U2) massive fluvioglacial
lacustrine deposits (863–790 cm below surface [bsf]; 14.7 ± 0.32–13.8 ± 0.12 cal. ka
BP); (U3) water current fluvioglacial lacustrine deposits (790–766 cm bsf; 13.8
± 0.12–12.9 ± 0.29 cal. ka BP); (U4) laminated/banded lacustrine deposits characterized
by terrigenous deposits from ice-covered lake periods and episodic events of ice
and snow melting (766–752 cm bsf; 12.9 ± 0.29–11.7 ± 0.15 cal. ka BP); and
(U5) massive muddy lacustrine deposits (752–0 cm bsf; 11.7 ± 0.15 cal. ka BP–present).
The occurrence of U2 to U4 deposits defines the transition from glacial cold
(U1) to net warm postglacial conditions (U5). These climate transitions are marked by
changes in sediments and the presence of very low sedimentation rate periods, possibly
related to the Intra-Allerød Cold Period and the coldest phase of the Younger
Dryas. Our results support the previously proposed timing of the retreat of the Serra
da Estrela glaciers ca. 13.8 ± 0.12 cal. ka BP. The robust chronology of Lake Peix˜ao
highlights the potential of Iberian pro-glacial lakes for dating deglaciation processes
and will lead to unprecedented decadal-to-centennial timescale palaeoclimate reconstructions
in this region since the last glacial–interglacial transition.2023-01-01T00:00:00ZSpatial variations in sediment production and surface transformations in subtropical fluvial basins (Caculuvar River, south‐west Angola): Implications for the composition of sedimentary depositsCruz, Armanda TrindadeDinis, Pedro AlexandreLucic, MavroGomes, Albertohttps://hdl.handle.net/10316/1140982024-03-19T14:23:05Z2022-01-01T00:00:00ZTitle: Spatial variations in sediment production and surface transformations in subtropical fluvial basins (Caculuvar River, south‐west Angola): Implications for the composition of sedimentary deposits
Authors: Cruz, Armanda Trindade; Dinis, Pedro Alexandre; Lucic, Mavro; Gomes, Alberto
Abstract: Several compositional features of sedimentary deposits can be used to reconstruct
environmental conditions of source areas. In this research, bulk X-ray
diffraction
mineralogy, heavy and clay mineral assemblages and geochemistry obtained for
modern deposits of the Cunene River and its tributaries Caculuvar–Mucope
are
integrated with geological/geomorphological characteristics of respective catchment
areas to evaluate to what extent sediment production is spatially variable and
source materials are differently affected by exogenous transformations. Detrital
sources can be classified into four main types based on sediment composition:
felsic, mafic, recycled and mixed. Source contributions obtained with unmixing
models using distinct input data reveal some disagreements, with heavy mineral
assemblages pointing to higher mafic contribution and bulk XRD-mineralogy
favouring
the recycled sedimentary component. However, the three datasets coincide
showing a lower supply from the Kalahari Basin than the large outcropping
areas of its sedimentary units would suggest, which is attributed to the relatively
low rainfall and relief in this region. Where multiple depositional cycles are involved
in sediment production the composition of the river deposits, even their
clay fractions, will not reflect coeval weathering transformations and an under-estimation
of the mafic component probably occurs. This research reveals how
exogenous processes may deviate the composition of the produced sediment from
a simple weighted by outcropping area average of the source units and compromise
(palaeo)environmental interpretations based on sediment composition.2022-01-01T00:00:00ZA multi-analytical evaluation of the depositional pattern on open-air rock art panels at "Abrigo del Lince" (Badajoz, Spain)Nicoli, MariaEftekhari, NegarVaccaro, CarmelaCollado Giraldo, HipólitoGarcês, SaraGomes, HugoLattao, VirginiaRosina, Pierluigihttps://hdl.handle.net/10316/1140752024-03-18T11:27:36Z2023-02-01T00:00:00ZTitle: A multi-analytical evaluation of the depositional pattern on open-air rock art panels at "Abrigo del Lince" (Badajoz, Spain)
Authors: Nicoli, Maria; Eftekhari, Negar; Vaccaro, Carmela; Collado Giraldo, Hipólito; Garcês, Sara; Gomes, Hugo; Lattao, Virginia; Rosina, Pierluigi
Abstract: Microscopic observation correlated with chemical-mineralogical characterization was performed on pigment samples from "Abrigo del Lince" rock art site (V-IV millennium BC), in order to provide contributions to the study of prehistoric schematic art on granite in the province of Badajoz (Spain). The research objectives include the understanding of technological and cultural aspects, as well as of conservation and deterioration issues related to the pictographs. The multi-analytical approach encompasses the integration of microscopic observation, SEM-EDS analysis, micro-Raman spectroscopy, and ATR-FTIR and allowed to achieve a multispectral overview of the samples and to describe their varied composition and the alteration pattern which connects them. The main phases overlying the granitic bedrock and involved in this sequence are as follows: hematite, whewellite, and gypsum. While hematite could be stratigraphically considered the most ancient layer and assigned to the use of red ochre as a pigment, whewellite and gypsum are the main constituent of the alteration layer which forms a patina over the pictographs, due to weathering processes. Finally, the role of biofilms in rock art conservation is discussed, suggesting that, especially for what concern thin and homogenous layers of oxalates, their presence should not be necessarily considered an issue.2023-02-01T00:00:00ZLandslide Susceptibility Assessment of a Part of the Western Ghats (India) Employing the AHP and F-AHP Models and Comparison with Existing Susceptibility MapsBhagya, Sheela BhuvanendranSumi, Anita SajiBalaji, SankaranDanumah, Jean HomianCostache, RomulusRajaneesh, AmbujendranGokul, AjayakumarChandrasenan, Chandini PadmanabhapanickerQuevedo, Renata PachecoJohny, AlfredSajinkumar, Kochappi SathyanSaha, SunilAjin, Rajendran ShobhaMammen, Pratheesh ChackoAbdelrahman, KamalFnais, Mohammed S.Abioui, Mohamedhttps://hdl.handle.net/10316/1140082024-03-14T10:43:10Z2023-01-01T00:00:00ZTitle: Landslide Susceptibility Assessment of a Part of the Western Ghats (India) Employing the AHP and F-AHP Models and Comparison with Existing Susceptibility Maps
Authors: Bhagya, Sheela Bhuvanendran; Sumi, Anita Saji; Balaji, Sankaran; Danumah, Jean Homian; Costache, Romulus; Rajaneesh, Ambujendran; Gokul, Ajayakumar; Chandrasenan, Chandini Padmanabhapanicker; Quevedo, Renata Pacheco; Johny, Alfred; Sajinkumar, Kochappi Sathyan; Saha, Sunil; Ajin, Rajendran Shobha; Mammen, Pratheesh Chacko; Abdelrahman, Kamal; Fnais, Mohammed S.; Abioui, Mohamed
Abstract: Landslides are prevalent in the Western Ghats, and the incidences that happened in
2021 in the Koottickal area of the Kottayam district (Western Ghats) resulted in the loss of 10 lives.
The objectives of this study are to assess the landslide susceptibility of the high-range local selfgovernments
(LSGs) in the Kottayam district using the analytical hierarchy process (AHP) and
fuzzy-AHP (F-AHP) models and to compare the performance of existing landslide susceptible maps.
This area never witnessed any massive landslides of this dimension, which warrants the necessity
of relooking into the existing landslide-susceptible models. For AHP and F-AHP modeling, ten
conditioning factors were selected: slope, soil texture, land use/land cover (LULC), geomorphology,
road buffer, lithology, and satellite image-derived indices such as the normalized difference road
landslide index (NDRLI), the normalized difference water index (NDWI), the normalized burn
ratio (NBR), and the soil-adjusted vegetation index (SAVI). The landslide-susceptible zones were
categorized into three: low, moderate, and high. The validation of the maps created using the receiver
operating characteristic (ROC) technique ascertained the performances of the AHP, F-AHP, and TISSA
maps as excellent, with an area under the ROC curve (AUC) value above 0.80, and the NCESS map
as acceptable, with an AUC value above 0.70. Though the difference is negligible, the map prepared
using the TISSA model has better performance (AUC = 0.889) than the F-AHP (AUC = 0.872), AHP
(AUC = 0.867), and NCESS (AUC = 0.789) models. The validation of maps employing other matrices
such as accuracy, mean absolute error (MAE), and root mean square error (RMSE) also confirmed
that the TISSA model (0.869, 0.226, and 0.122, respectively) has better performance, followed by
the F-AHP (0.856, 0.243, and 0.147, respectively), AHP (0.855, 0.249, and 0.159, respectively), and
NCESS (0.770, 0.309, and 0.177, respectively) models. The most landslide-inducing factors in this
area that were identified through this study are slope, soil texture, LULC, geomorphology, and
NDRLI. Koottickal, Poonjar-Thekkekara, Moonnilavu, Thalanad, and Koruthodu are the LSGs that
are highly susceptible to landslides. The identification of landslide-susceptible areas using diversified
techniques will aid decision-makers in identifying critical infrastructure at risk and alternate routes
for emergency evacuation of people to safer terrain during an exigency.2023-01-01T00:00:00Z