The role of climate, marine influence and sedimentation rates in late-Holocene estuarine evolution (SW Portugal)
| Autor: | Roberto Bao, Manel Leira, Pablo Arias, Mário Cachão, Susana Costas, Mariana Diniz, Ana Maria Costa, Maria da Conceição Freitas, Aurora Rodrigues, Ana Cristina Araújo, João Batista Duarte, César Andrade, Pedro Costa |
|---|---|
| Přispěvatelé: | Repositório da Universidade de Lisboa |
| Jazyk: | angličtina |
| Rok vydání: | 2019 |
| Předmět: |
010506 paleontology
Archeology 010504 meteorology & atmospheric sciences Paleoclimate Fluvial Field 01 natural sciences Storminess Fluvial discharge Region 14. Life underwater Environmental proxies Sea-level oscillation Climate variability Sea level Holocene 0105 earth and related environmental sciences Earth-Surface Processes Global and Planetary Change geography geography.geographical_feature_category Ecology Drought Flow Paleontology Estuary Valley Sedimentation River discharge Relative sea-level Oceanography 13. Climate action Atlantic coast Geology |
| Zdroj: | Repositório Científico de Acesso Aberto de Portugal Repositório Científico de Acesso Aberto de Portugal (RCAAP) instacron:RCAAP |
| Popis: | Estuaries are sensitive to changes in global to regional sea level, to climate-driven variation in rainfall and to fluvial discharge. In this study, we use source and environmentally sensitive proxies together with radiocarbon dating to examine a 7-m-thick sedimentary record from the Sado estuary accumulated throughout the last 3.6 kyr. The lithofacies, geochemistry and diatom assemblages in the sediments accumulated between 3570 and 3240 cal. BP indicate a mixture between terrestrial and marine sources. The relative contribution of each source varied through time as sedimentation progressed in a low intertidal to high subtidal and low-energy accreting tidal flat. The sedimentation proceeded under a general pattern of drier and higher aridity conditions, punctuated by century-long changes of the rainfall regime that mirror an increase in storminess that affected SW Portugal and Europe. The sediment sequence contains evidence of two periods characterized by downstream displacement of the estuarine/freshwater transitional boundary, dated to 3570-3400 cal. BP and 3300-3240 cal. BP. These are intercalated by one episode where marine influence shifted upstream. All sedimentation episodes developed under high terrestrial sediment delivery to this transitional region, leading to exceptionally high sedimentation rates, independently of the relative expression of terrestrial/marine influences in sediment facies. Our data show that these disturbances are mainly climate-driven and related to variations in rainfall and only secondarily with regional sea-level oscillations. From 3240 cal. BP onwards, an abrupt change in sediment facies is noted, in which the silting estuarine bottom reaches mean sea level and continued accreting until present under prevailing freshwater conditions, the tidal flat changing to an alluvial plain. The environmental modification is accompanied by a pronounced change in sedimentation rate that decreased by two orders of magnitude, reflecting the loss of accommodation space rather than the influence of climate or regional sea-level drivers. FCT by Spanish Ministry of Science and Innovation [SFRH/BD/110270/2015, HAR2014-51830-P, HAR2011-29907-C03-00] FCTPortuguese Foundation for Science and Technology [PTDC/HISARQ/121592/2010] Instituto Dom Luiz-IDL [UID/GEO/50019/2013] info:eu-repo/semantics/publishedVersion |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|