Boats carved on the Atlantic coast of the Iberian peninsula. Landscape, symbols and people (original) (raw)
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Environmental Earth Sciences
Coastal areas are extremely sensitive to variations in environmental conditions. The interaction of marine and continental processes causes a high degree of dynamism, generating depositional formations of great value for palaeoenvironmental reconstruction. This paper focuses on two pedostratigraphic deposits located under the current beach, in close proximity to archaeological tumuli located on Areoso Island (Ría de Arousa, NW Iberian Peninsula). Employing a geoarchaeological approach, sea-level rise, environmental conditions and human occupation over a 6000-year period are interpreted. The results of granulometric and mineralogical data, elemental composition and stratigraphic features, help to identify three successive environments: continental (rock weathering, soil formation and erosion); a transition to a coastal environment; and the establishment of full coastal conditions. The geomorphological evolution of the last 6.0 kyr BP has been controlled by climate, sea-level rise and...
Archaeological remains as sea level change markers: A review
Quaternary International, 2009
The Mediterranean Sea constitutes a unique basin from an historical and archaeological point of view, as it has been a privileged way of communication for thousands of years for the people that dwelled on its shores. Their passage has left many traces on the seabeds in the areas where the ancient commercial routes passed, and remains of structures where moorings, havens or dwellings existed. Some of these structures, nowadays submerged, offer interesting indications aiding the reconstruction of the ancient coastlines. This contribution aims to examine recent work in coastal geo-archaeology, targeting both (1) gathering and discussion of the data, particularly those pertaining to the Italian coasts; and (2) commentary on the methodological debate and verification of the possibility of a protocol that may contain unequivocal referring elements.To investigate the archaeological evidence currently underwater because of the relative sea level variations (harbour infrastructures, fishponds, villae maritimae, caves – nymphaei, private or public buildings or town quarters, pre- and protohistorical villages, quarries, caves, etc.), a clear and more coherent methodological assumption may be needed. The archaeological interpretation must initially establish the maritime and/or harbour nature and vocation of the site, determine its typology and specific usage, analyze the elements of its building techniques (that reveal themselves as meaningful markers of height or depth at the time of building) and its “functional” elements (the measure of the emerged part with respect to the average sea level), and point out the time of construction, its chronological range of usage/frequentation, the dynamics of its abandonment/destruction/obliteration.The evaluation of both the height and functional depth to the mean sea level depends on the typology of the archaeological evidence, its use and the local tide amplitudes. The surface of a pier surely has a functional elevation different from that of a haulage area or a platea or a pavement.
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.
Paleolithic Landscapes and Seascapes of the West Coast of Portugal
The antiquity of coastal adaptations has gained renewed attention in the last several years as archaeologists have recognized that coasts have long been important foci of human settlement (Bailey 2004; Bailey and Milner 2003; Erlandson and Fitzpatrick 2006; Fa 2008; Price 1995; Sauer 1962; Westley and Dix 2006).
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.
Relative Sea Level, Diastrophism and Coastal Erosion: the Case of Espinho (Portuguese NW coast
The plotting of relative sea level for several stations belonging to the Iberian Peninsula shows different trends. These trends seem to be related with the diastrophism affecting more intensely the Northern and Southern façade of the Peninsula. The marine terraces (Pleistocene) at the North of Espinho (NW coast of Portugal) and the würmian/holocene deposits at the South of this city show opposite tectonic trends that seems to define a tectonic depression corresponding approximately to the localisation of Esmoriz lagoon. At Espinho, coastal erosion began in the middle of nineteen century. We think that the contemporary rising of sea level that began after the end of Little Ice Age, together with a possible subsiding trend, may be responsible for the severe erosion endured by this area.
Porto littoral: the influence of tectonics in sea level changes and coastal morphology
The plotting of relative sea level variations for several stations belonging to the Iberian Peninsula shows different trends. These trends seem to be related with the diastrophism affecting more intensely the Northern and Southern façade of the Peninsula. Porto is located on the riverside of Douro, the most plentiful river in the Iberian Peninsula, which is deeply entrenched on the littoral platform, close to its mouth. This littoral platform is a quite common feature at Portuguese coastline, surrounding it almost in all its length. At Porto area the littoral platform contains several outcrops of cenozoic deposits and it is limited to the interior by a generally step relief (marginal relief) which is probably a fault scarp acting mostly after the earlier deposits had been formed A careful study of those deposits showed up that they are not at all primarily marine as its situation, facing the Atlantic could make us suppose: the marine deposits are disposed only in a narrow fringe lower than 40 m high. The upper deposits have a clear fluvial origin, they go up until 130m and they are clearly disturbed by tectonics. Apparently, a sub-meridian accident produced the subsidence of the narrow fringe (1- 2km maximum width) where the marine deposits are lying. This seems to indicate that the sea retouched this lower block when it subsided along that sub-meridian fault (fig. 1). The newer, marine deposits can be assigned to at least three levels (around 30m, 20m and from 10 to recent sea level) distinguished by sedimentary criteria. They are not everywhere at the same altitude, but they are disposed in a irregular up and down pattern, with a general trend indicating a subsidence towards the meso-cenozoic basin that evolved like an aulacogen during meso-cenozoic times, and begins at Espinho, 15km south of Porto (Lusitanian basin). We will focus on the tectonic style and regional tectonic framework that created the differences between 2 places, one of them appears at the north and the other at the south of Porto area. A aeolian sandstone lying upon a marine deposit (Labruge beach, 15 km north of Douro river mouth, 5m above mean sea level) was TL dated, with a result of 84kaBP. Therefore, the underlying marine deposit must be from last interglacial. In addition, it is possible to correlate other iron-cemented sandstones covering old marine platforms with a similar position, found at several places in this coastline, with the same interglacial. Admitting the sedimentology-based correlation of marine deposits at the North of Espinho they seem to be balanced to south, in the direction of Lusitanian basin (fig. 2). At Aguda beach, some 12 km south of Porto the last interglacial marine deposit is laying at a lower altitude, 1m above mean sea, level fossilizing a wide marine platform. Upon it, we found some lagoon deposits. The upper part of them (around 4-5m above msl) was TL dated with a result of ca. 8ka BP. So, this lagoon deposits are a testimony of continental conditions during last glaciation and/or flandrian transgression.
Single Contributions. Archaeology and Economy in the Ancient World 53 (Heidelberg, Propylaeum 2022) 565–569, 2022
Florian Hermann (Philipps-Universität Marburg) - Felix Teichner (Philipps-Universität Marburg) - Joao Pedro Bernardes (Universidade do Algarve) - Ricardo Soares (Câmara Municipal de Vila do Bispo), Boca do Rio (Algarve, Portugal) – A center of export oriented garum production on the shore of roman Lusitania. Located in the extreme southwest of Iberia, the area of Sagres includes several small fishing ports and archaeological sites (as those around the palaeoestuary of Boca do Rio). These sites still preserve records and elements of a long fishing tradition, as well as from its Atlantic and Mediterranean influences, and the geo and bio-indicators of ancient coastal cataclysms. Through a transdisciplinary fieldwork and an integrated research, the autors seek to clarify the coexistence of these fishing populations with the geo-coastal dynamics and with the communities of seafarers. On the shores of the old lagoon and paleoestuary of Boca do Rio, archaeological research detected an intense fishing and saline occupation with more than two thousand years, whose locations alternate between the beach and the interior lands. In these sites, it is possible to observe the evolution of the instruments and fishing gear. Concomitantly, Boca do Rio natural characteristics yield exceptional conditions for the observation of coastal geodynamics and their effects on the local communities. Moreover, in the surrounding region, the geo-indicators of ancient coastal cataclysms and their consequences are very well preserved. In addition, geo-sedimentological research has demonstrated the frequent invasion of the paleoestuary by high-energy marine events, such as the 1755 Tsunami, whose impact and destructive force can be measured.
Form and Relation to Present Sea Level of Pleistocene Marine Erosion Features
The Journal of Geology, 1965
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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.