El registro geoambiental del estuario holoceno de huelva como indicador de la historia evolutiva de sus asentamientos ribereños

Abstract

The coastline is one of the most dynamic, fragile and complex natural environments on the planet. This transition area between terrestrial and marine systems is characterized by intense processes of sediment and organic matter exchange. At the same time, migrations and human displacements have been favored since their inception by the existence of a global coastal strip; both for mobility reasons and for its high biodiversity and productivity. The coast was soon dotted with countless settlements that, over time, would constitute some of the most important archaeological sites in human history. Therefore, the understanding of the coastal dynamics and its evolution through time is crucial for the correct understanding of the distribution and meaning of the regional archaeological settlements. This Doctoral Thesis addresses the study of the Holocene geoenvironmental record (last 6.500 years) of Huelva estuary, southwest of the Iberian Peninsula, through the analysis of three areas (La Cascajera, in Saltés Island; the Palos de la Frontera cove, and the ancient city of Onoba); and simultaneously, its interrelationship with the evolution of the riverside human settlements during the different historical periods. The estuaries of Huelva have been extensively studied from the geological and archaeological perspectives, generally approached independently. In recent years, both disciplines have joined forces, achieving a synergy that has allowed a considerable improvement in the understanding of the interaction between the human settlement pattern and its environment. Geologically, the study of the geological outcrop has been based on the lithological features of profiles and cores from boreholes carried out in the La Cascajera sand barrier and in the Palos cove, with a total of 168 gross samples for different analyses. In the case of the city of Onoba, a geomorphological and morphodynamic cartography was carried out. Moreover, the historiographic documentation of the sites was reviewed. This has allowed to reconstruct the processes that originated the different sedimentary units which have been filling the estuary and, furthermore, to establish a chronology of natural events, anthropic activities and their palaeoenvironments. The multidisciplinary analysis of the upper Holocene sediments of the La Cascajera shows a regressive sequence, from a basal sandy tidal plain to a current marshland, with three intermediate facies (muddy tidal plain, chenier and whashover fans). The barrier emerged in the transit of the 1st Century BC.-2nd Century AD. Once stabilized, a Roman cetarea dedicated to the processing of marine resources was installed, active since the end of the 4th Century AD. until the end of the 5th Century AD. The geoarchaeological study of the Onoba settlement has revealed that the evolution of the cliff relief of Los Cabezos (hills) conditioned the urban layout. In its southernmost area, a large port area, whose activity sustained the city's economy, was developed. The analysis of the soundings of the historic port of Palos shows a transgressive-regressive cycle during the Holocene, evolving from a terrestrial paleo-environment to a coastal-marine one. From this record, it has been possible to date the final period of the maximum of the Flandrian Transgression at 5.300 years. Furthermore, the late Holocene record shows that, by medieval times, the tidal channel of the cove would present colmatation problems, although it would be deep enough for navigation. The interrelation between archaeological findings, dynamics and coastal geomorphology has allowed us to define the natural evolution of Huelva estuary since the beginning of the present high sea level (6.500 years B.P.), as well as its link with the patterns of human settlements by favoring the creation and development of river and sea ports continuously for more than 3.000 years.