Sea-level change and human occupation over 6000 years on Areoso Island (Ría de Arousa, NW Iberian Peninsula) (original) (raw)
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Sea level change and human occupation over 6000 years at Areoso Island (Ria de Arousa, NW Iberia)
The coast is very sensitive to variations in environmental conditions. The interaction of marine and continental processes causes a high dynamism, generating depositional formations with a high value for paleoenvironmental reconstruction. This work focused on the case of two edapho-sedimentary sequences located under the current beach, near of archaeological tumuli context at Areoso Island (Ría de Arousa, NW Iberia). With a geoarchaeological approach, sea level rise, environmental conditions and human occupation over 6000 years are interpreted. The results of granulometric and mineralogical data, elemental composition and stratigraphic features, help to identify three formation environments: granite weathering, continental (soil formation and erosion) and marine-aeolian. Geomorphological evolution from the last 6.0 kyr BP has been controlled by climate and sea level change and anthropogenic causes. The continental facies evidence low sea level up to 4.8 kyr BP. After 3.2 kyr BP, the...
Late Pleistocene raised beaches of coastal Estremadura, central Portugal
Quaternary Science …, 2009
We present new stratigraphic, sedimentological, and chronological data for a suite of tectonically raised beaches dating to Marine Isotope Stages 5, 4, and 3 along the Estremadura coast of west-central Portugal. The beach deposits are found in association with ancient tidal channels and coastal dunes, pollen bearing mud and peat, and Middle Paleolithic archaeological sites that confirm occupation of the coastal zone by Neanderthal populations. The significance of these deposits is discussed in terms of the archaeological record, the tectonic and geomorphic evolution of the coast, and correlation with reconstructions of global climate and eustatic sea-level change. Direct correlation between the Estremadura beach sections is complicated by the tectonic complexity of the area and the age of the beach deposits (which are near or beyond the limit of radiocarbon dating). Evidence from multiple sites dated by AMS radiocarbon and optical luminescence methods suggests broad synchroneity in relative sea-level changes along this coast during Marine Isotope Stage 3. Two beach complexes with luminescence and radiocarbon age control date to about 35 ka and 42 ka, recording a rise in relative sea level around the time of Heinrich Event 4 at 39 ka. Depending on assumptions about eustatic sea level at the time they were deposited, we estimate that these beaches have been uplifted at rates of 0.4–4.3 mm yr1 by the combined effects of tectonic, halokinetic, and isostatic processes. Uplift rates of 1–2 mm yr1 are likely if the beaches represent sea level stands at roughly 40 m below modern, as suggested by recent eustatic sea level reconstructions. Evidence from coastal bluffs and the interior of the study area indicates extensive colluvial, fluvial, and aeolian sedimentation beginning around 31 ka and continuing into the Holocene. These geomorphic adjustments are related to concomitant changes in climate and sea level, providing context that improves our understanding of Late Pleistocene landscape change and human occupation on the western Iberian margin.
2019
The Western coast of the Iberian Peninsula stands as an interface between both the Atlantic and Mediterranean climatic influences and marine / fluvial conditions. The paper aims to assess the environmental changes in the last ca 6000 years (both natural and anthropogenic induced) using multiproxy analysis (geomorphological and sedimentological data, elemental and stable isotope content, microfossil assemblages, radiocarbon dating, and historical records) applied to an embayed coast. Afterwards the sedimentation rate (SR) reached high values (0.19-0.48 cmyr-1), as the result of Roman intervention in the drainage basin where pastures and local fires are recorded, together with an increasing dryness. A major disturbance is recorded in the Pollen Assemblages Zones (between PAZ II and PAZ III) and in the sediments around 1863-1706 cal BP (2σ), in the transition from the Roman Age to the Muslim invasion period, probably reflecting a hiatus in the sedimentary record. Onwards, SR reached 0.21-0.57 cmyr-1. Two major hydro marine episodes may have contributed to this fact: the latter is the Lisbon tsunami (1755 AD) while the former may reflect the 16 th Century tsunamis or a great marine storm episode. An aeolian environment prevailed since then and the embayment was transformed into a dune field interrupted only by the narrow channel of the river whose mouth is often closed.
Holocene aeolian phases and human settlements along the Atlantic coast of southern Spain (1999)
The Holocene 9(3):333-339, 1999
A combined geomorphological, radiocarbon dating, archaeological and historical approach permits a refining of the age of the coastal dune systems related to estuaries in the Gulf of Cadiz. Three dune systems are distinguished in this paper. The oldest one, D1, which accumulated under prevailing WSW winds during the first millennium BC, overlays both the occupational horizons of Late Neolithic-Early Copper Age (fourth millennium BC) and the lithic workshop levels’ (fourth to second millennia BC). The middle dune system, D2, containing both Roman and medieval remains, accumulated between the thirteenth or fourteenth centuries and the seventeenth century AD The youngest D3 system is associated with the time of building of watchtowers in the seventeenth century ad but extends to the present; it is related to SW prevailing winds. We explain the absence of aeolian deposits prior to |2700 cal. BP as the result of trapping of a large part of the sediment supply in the estuaries, which starved the neighboring beaches and aeolian settings. Aeolian accumulation reached significant values when sedimentation in the coastal zone changed from being mainly aggradational in the estuaries (|6500–2700 cal. BP) to mainly progradational in spit barriers and related dunes (post |2700 cal. BP). The present analysis of aeolian systems suggests a non-direct correlation, at least in some cases, between coastal progradation of spit barriers and aridity.
Quaternary International, 2008
Sea level and climate changes archived in various coastal environments during the last part of the last glacial and present interglacial periods are investigated by interpolating available geomorphology, sedimentology, palaeontology and geochronology data. The coastal response to these changes depended on the environment and geographic location. Changes of sea level during the rising, transgressive phase are well recorded in the sedimentary filling of the estuaries, whereas during the phase of highstand they are best recorded in beach-barrier environments. The postglacial rise of sea level took place in two phases: a rapid rise until 6500 cal BP, and a second phase of near stability with minor oscillations of metric magnitude. Regarding climate changes, there is no record of changing temperatures in the coastal zones of southern Spain, although there is in precipitation and wind intensity/velocity. After 7-5 cal ka BP, the general climatic trend towards aridity was punctuated by several short-lived (centennial) episodes of increased aridity that occurred with a millennial cycle, often coincident with Bond cool events and, in some cases, with decreases of sea surface temperatures. The absence of human intervention in vegetation composition until 2000 BP suggests that most environmental coastal shifts were climatically driven. r
CLIMATE, TECTONICS AND BEACH EROSION: THE CASE OF ESPINHO (NW PORTUGUESE COAST
Sea level is a very changeable surface. Furthermore, the land may also be moving, in a slower rate, generating relative sea level changes. The causes of relative sea level changes are variable, but the ones that cause more intense variations are related to climate. During Little Ice Age (LIA) Northern Hemisphere's summer temperatures fell significantly below the AD 1961–1990 range. This climate situation was responsible for a greater discharge of rivers, which could lead to a greater transportation of sediments to the coastline. During these cold periods, sea level was lower than in present time. All this could imply a coastline progradation, with the successive abandon of older beach ridges, reinforcing the sandy supply for dune building. The coastal situation should be, in some sense, the opposite of the situations that we face today. In present warm period, rivers carry less sediment than during LIA. Moreover, the recent sea level rise contributes to a coastal migration inlands and the erosion of previous beaches and dunes. Our investigation on ancient marine levels and Holocene cemented dunes suggests that the area near Esmoriz (20 km south of Porto, NW Portuguese coast) is probably subsiding. This possible subsidence, together with recent sea level rise, induced by the end of LIA, could explain the severe coastal erosion that is taking place at Espinho area (15 km south of Porto) since the middle of the XIX century. This example shows clearly the complexity of relative sea-level changes. Because of this complexity, sea level curves are not similar worldwide, as they depend on the interference of multiple timescales phenomena.
Holocene aeolian phases and human settlements along the Atlantic coast of southern Spain
The Holocene, 1999
A combined geomorphological, radiocarbon dating, archaeological and historical approach permits a refining of the age of the coastal dune systems related to estuaries in the Gulf of Cádiz. Three dune systems are distinguished in this paper. The oldest one, D1, which accumulated under prevailing WSW winds during the first millennium bc, overlays both the occupational horizons of Late Neolithic-Early Copper Age (fourth millennium bc) and the‘lithic workshop levels' (fourth to second millennia bc). The middle dune system, D2, containing both Roman and medieval remains, accumulated between the thirteenth or fourteenth centuries and the seventeenth century ad. The youngest D3 system is associated with the time of building of watchtowers in the seventeenth century ad but extends to the present; it is related to SW prevailing winds. We explain the absence of aeolian deposits prior to 2700 cal. BP as the result of trapping of a large part of the sediment supply in the estuaries, which s...