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Most studies on the geomorphological evolution of the Holocene from the Ebro depression (NE Spain) are focused on the period up to the Roman Epoch (218 BC–476 AD) while some references to medieval (476 AD–15th century) deposits are also occasionally dated. This paper focuses on the establishment of aggradation units on the valley bottoms and slopes of the Ebro depression after 1400 BP, their origin, comparison with other areas, and relationship with global paleoenvironmental changes. These units were produced after the incision phase that marked the end of the large Holocene accumulation (unit H1) around 1400 BP (at the end of the Late Roman Epoch). Morphosedimentary records enable us to establish three aggradation units during the last 1400 years: unit H2 (ca. 1400–650 cal BP); unit H3 – with two H3A subunits (ca. 650–500 cal BP) and H3B (ca. 500–320 cal BP); and the H4 unit (after 320 cal BP). These units are organized following five types of aggradation/incision arrangements with differing complexities. There are also connections among these units and two slope stages in the region. Finally, the genetic relationships between these units and global paleoenvironmental changes are shown (LALIA, MCA, and LIA) and related to anthropic activity. This contribution is the first detailed and systematic approach to the study of morphosedimentary units and sedimentary arrangements during the Recent Holocene in the Mediterranean area. [ABSTRACT FROM AUTHOR]

The present paper deals with the historical evolution of the northern Bay of Cádiz (SW Spain) between the last eustatic maximum (6.5 ka BP) and the present day, by means of a series of independent proxies. The zone is constituted by the tidal estuary of the Guadalete River, filled with saltmarsh sediments during the late Holocene, due to the sheltering of the zone by a confining outer sandy barrier. The northern border of the Bay records an urban settlement of Phoenician Age (first millennium BC), Doña Blanca. A detailed survey was made in the contact between the Phoenician city and the saltmarshes in order to detect other possible urban structures related to the morphological and sedimentary evolution of this environment during historical times. Two campaigns with GPR Stream-X array were carried out as well as aerial imaging and topographic survey with UAV. In parallel, a total of 8 boreholes were made in different parts of the saltmarshes, including radiocarbon dating of selected samples for estimating sedimentation rates in the saltmarshes. Results obtained by georadar prospection and UAV survey revealed the presence of a second urban settlement on the marginal sedimentary plain, very probably installed upon a sandy fluvial island of the Guadelete River. The urban remains, of Punic Age, are partly covered by clay sediments due to the subsequent evolution of these saltmarshes, where sedimentation rates of up to nearly 2.4 mm/yr have been estimated for environments close to fluvial and/or tidal channels and hence more affected by sediment aggradation during flooding episodes. In recent times, river regulation by dams and the artificial desiccation and cropping of the saltmarshes have interrupted the natural trend of the area towards sedimentary silting up. [ABSTRACT FROM AUTHOR]

Pérez-Arlucea, M., Álvarez-Iglesias, P. and Rubio, B., 2007. Holocene Evolution of Estuarine and Tidal-flat Sediments in San Simón Bay, Galicia, NW Spain. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 163 – 167. Gold Coast, Australia, ISSN 0749.0208 San Simón Bay is located in the inner part of a Galician ría. Three rivers enter the bay from the north, forming shallow estuaries. Tidal range is mesotidal (2 to 4 m with an average of 2.2 m). High productivity ecosystems develop due to upwelling processes, which are common in all the Galician rías. The aim of this paper is the study of fluvial and tidal interactions giving rise to distinctive facies architecture in the context of the Holocene transgression. Vertical facies distributions and architecture show alternating units of well-defined estuarine channel-fill and tidal flat deposits. Two millennial-scale, fining-upward sequences show an initial incision evolving into channel fill and tidal flat deposits. An age model has been developed based on AMS 14C and 210Pb and 137Cs dating to put them in the context of the established climatic and sea-level changes. Older dated deposits give an age of 5.9 ky cal BP close to the last Holocene eustatic maximum. Millennial-scale sedimentation rates are about 1.0-1.6 mm y-1, whereas the last few decades show values 5 to 6 times higher. Differences in sedimentation rates are attributed to increasing human influence over recent decades. Incision stages at the base of the sequences (5.1 to 4.8 cal. ka BP and 2.3 to 2.0 cal. ka BP) followed by aggradation are interpreted in terms of high frequency climatic oscillations and related changes in sediment supply and river activity (incision taking place with a decrease in sediment supply). Meter-scale sequences are developed in channel-fill units, indicating superimposed minor, centennial-scale, climatic instabilities giving way to changes in channel activity. [ABSTRACT FROM AUTHOR]