Percorrer por autor "Fatela, Francisco"
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- Environmental change in SW Portugal during the last 3900 years BP: an ostracoda assessmentPublication . Fernandes Martins, Maria João; Cabral, Maria Cristina; Magalhães, Vitor Hugo; Drago, Teresa; Fatela, Francisco; Oliveira, AnabelaOstracod, geochemical, mineralogical, and sedimentological proxies from a sediment core collected off Sagres (southwestern Portugal) were used to reconstruct Holocene environmental and hydrodynamic changes. Reduced variability of geochemical elements between ~4000 and ~1290 calibrated years before present suggests relatively stable conditions, regularly disturbed by higher-energy events. At ~1290 cal yrs BP, a transition from arid to wetter conditions is suggested based on enhanced terrestrial/detrital input after this time. Ostracod assemblages further captured fine-scale hydrodynamic variability, offering greater sensitivity to oceanographic changes. Our results support a broader pattern of middle-to-late Holocene drying conditions in southern Iberia, followed by a shift to wetter conditions during periods of negative North Atlantic Oscillation (NAO) index. Our study provides new data on offshore ostracods from the western Algarve, underscoring their value for high-resolution paleoenvironmental reconstructions.
- Neoichnology and sediment distribution in tidal flats of the mud‐dominated mesotidal mira river estuary (Portugal)Publication . Shchepetkina, Alina; Drago, Teresa; Santos, Jacqueline; Alberto, Ana; Fatela, Francisco; Freitas, Maria da ConceiçãoInvertebrate burrow morphologies and distributions are presented for the tidal flats of the middle and lower reaches of the tide-influenced (mesotidal), mud-dominated Mira River estuary (SW Portugal) as an analogue for interpreting the ichnology of palaeoestuarine successions. Burrow distributions are revealed using field observations of biogenic and physical sedimentary structures, trace makers, collected grab samples, push cores and lab measurements of grain size, organic matter and calcium carbonate content and linked to physico-chemical stresses. Estuarine tidal-flat surface open burrow distribution and bioturbation intensity are analysed in plan view using free scientific image analysis software (ImageJ) to obtain burrow density, total burrow area and minimum and maximum burrow diameters. The total tidal flat area occupied by organisms ranges from 0.8% to 4.1% in the middle estuary and is 1.4% in the lower estuary. These equate to a bioturbation index of one to two (BI 1–2). However, computed tomography (CT) of push cores (cross-sectional view) taken on the same tidal flats shows sparse to complete bioturbation intensity (BI 1–6), revealing that tidal flat sediments tend to be more biogenically reworked cumulatively over time with overprinting of subsequent tiers and/or recolonized. CT scanning also allows the identification of more burrow types, demonstrates infaunal tiering and provides insights into trace-fossil preservation potential. This research shows that the trace communities are heterogeneous and change spatially and temporally along the Mira River estuary, reflecting a physico-chemical gradient and seasonality. This trend signals changes in sediment composition, substrate type and consistency (sediment compaction and subaerial exposure), salinity, oxygenation, temperature, pH and interplay of tidal versus hydraulic energy.