Luis M. Cáceres

Recent coastal evolution of the Doñana National Park (SW Spain)

Abstract Since the last Holocene sea level rise, about 6900 BP, a series of depositional littoral landforms has been generated at the outlet of the Guadalquivir River, with progradation along the predominant longshore drift (towards the east). The first coastal progradation occurred between 6900 and 4500 BP. The Donana and (perhaps) La Algaida spits, both associated with the oldest and highest marshland in the Donana National Park, are assumed to have been developed at an early stage. Originally, the Guadalquivir estuary was wider and deeper than now, and its environment was mainly marine. The oldest littoral formations have been dated as ca. 4735 BP. They show erosional events, and indicate the breaking-up of earlier spit-barriers to form inlets. The marine environment became increasingly dominant, with heavy erosion of cliffs and a retreating coastline. This period was followed by another sedimentary cycle (4200-2600 BP) that surrounded the earlier eroded barriers. The size of the estuary decreased due to the increasing marsh deposits, and a fluvial environment was born. About 2600 years ago, progradation gave way to a new period of intense erosion. The resulting morphology of littoral strands and erosional surfaces permitted the return to a marine environment. The shoreline again retreated. From 2300 BP, coastal progradation has prevailed, with an erosional interruption at 1000 BP. The present-day outlet of the Guadalquivir is an estuarine delta of inactive marshland (the Donana National Park), the dominant environment is fluvial.

A rock engraving made by Neanderthals in Gibraltar

Significance The production of purposely made painted or engraved designs on cave walls is recognized as a major cognitive step in human evolution, considered exclusive to modern humans. Here we present the first known example of an abstract pattern engraved by Neanderthals, from Gorham’s Cave in Gibraltar. It consists of a deeply impressed cross-hatching carved into the bedrock of the cave older than 39 cal kyr. The engraving was made before the accumulation of Mousterian layer IV. Most of the lines composing the design were made by repeatedly and carefully passing a pointed lithic tool into the grooves, excluding the possibility of an unintentional or utilitarian origin. This discovery demonstrates the Neanderthals’ capacity for abstract thought and expression. The production of purposely made painted or engraved designs on cave walls—a means of recording and transmitting symbolic codes in a durable manner—is recognized as a major cognitive step in human evolution. Considered exclusive to modern humans, this behavior has been used to argue in favor of significant cognitive differences between our direct ancestors and contemporary archaic hominins, including the Neanderthals. Here we present the first known example of an abstract pattern engraved by Neanderthals, from Gorham’s Cave in Gibraltar. It consists of a deeply impressed cross-hatching carved into the bedrock of the cave that has remained covered by an undisturbed archaeological level containing Mousterian artifacts made by Neanderthals and is older than 39 cal kyr BP. Geochemical analysis of the epigenetic coating over the engravings and experimental replication show that the engraving was made before accumulation of the archaeological layers, and that most of the lines composing the design were made by repeatedly and carefully passing a pointed lithic tool into the grooves, excluding the possibility of an unintentional or utilitarian origin (e.g., food or fur processing). This discovery demonstrates the capacity of the Neanderthals for abstract thought and expression through the use of geometric forms.

Late Holocene evolution of the southwestern Doñana National Park (Guadalquivir Estuary, SW Spain): a multivariate approach

Four phases are distinguished in the Late Holocene evolution of the southwestern Donana National Park (SW Spain), based on a multidisciplinary analysis of the sediments present in drill cores. In the oldest phase (>2400–2500 cal. yr BP), a coastal lagoon (the Roman Lacus Ligustinus) was recognized in the central part of this area, partly closed by the Donana spit and limited by fluvial levees. The following phase (∼2400–2200 cal. yr BP) is characterized by high-energy events, which caused the breakthrough of the Donana spit and the creation of new littoral strands in the inner areas. In the third phase (∼2200–2050 cal. yr BP), this new outlet was closed, coinciding with the progradation of the Donana spit. The last phase (∼2050 cal. yr BP–Recent) comprises three periods: (a) an unstable period (∼2050–1950 cal. yr BP), with the deposit of cheniers over the previous levees; (b) an infilling period, with a diminution of the marine influence; and (c) the appearance of temporary ponds between the emerged levees and cheniers.

Analysis of the recent storm record in the southwestern Spanish coast: implications for littoral management.

This work compares the geomorphologic evolution of the Huelva coast (SW Spain), some climatic-oceanographic data of the Cádiz Gulf and the recent storm record of this zone, covering the last 4 decades (1956-1996). An interesting correlation was found between the southwestern wind periodicity, the number of storm periods and the beach ridges observed in the main spits (El Rompido and Doñana). The spectral analysis of the wind time series permits to establish two most probable levels of periodicity: 6 and 9-10 years. Both periods coincide with the storm record and the creation of new beach ridges after a high-energy period. Beach damage, another storm-induced effect, was analysed by deducing different implications for the future management of tourist localities.

The geological record of the oldest historical tsunamis in southwestern Spain

A regressive sequence was determined in the late Holocene evolution of the southwestern Donana National Park (SW Spain), based on a multidisciplinary study of sediments obtained in a drill core. In an initial phase (> cal. 2400 years BP), a shallow coastal lagoon with a partial marine connection occupied this area, with a progressive transition from subtidal to supratidal conditions. The following phase (cal. 2400-2350 years BP) is characterized by a tsunami, with the deposition of an upper chenier. This sedimentological layer is characterized by a ridge morphology, an erosive base, high bioclastic contents and the introduction of marine species toward the inner areas of this old lagoon. This tsunami may be assimilated to one of the historical tsunamis that occurred between 218 and 209 BC. A comparison with other deposits derived from these high-energy events permits to draw the differential effects produced along the western Iberian coasts. SHORT NOTES

Population age structure techniques and ostracods: Applications in coastal hydrodynamics and paleoenvironmental analysis

Abstract Ostracods are microcrustaceans that grow by moulting (eight to nine instars in most cases) and, consequently, studies of its populations need the application of some special techniques. The population age structure techniques [Whatley, in: Ostracoda in the Earth Sciences, 1988, pp. 245–256] are a simple statistical method to estimate paleoenvironmental conditions in fossil/Recent populations of ostracods. For its application, it is necessary to determine the percentages of each instar present in the samples studied, in order to analyze the different types of population age structure histograms and their (paleo-)environmental interpretations. Some potential applications are the (paleo-)energy levels or the sedimentation rates. In this paper, these special techniques are applied to Recent populations of the ostracod Pontocythere elongata collected in littoral sediments of southwestern Spain. In this area, the relative percentages of this species and the adult percentages are closely related with depth and consequently this species was used as a bathymetrical tracer in shallow Neogene areas of the Guadalquivir Basin. In addition, a first three-step multivariate analysis permits the definition of three groups, closely related to the theoretical models proposed by Whatley: (a) Group 1 structure or biocoenosis, present either in Recent low- to medium-energy environments located in erosional coastal stretches and Neogene fair-weather conditions; (b) Group 2 structure or high-energy thanatocoenosis, observed either in Recent river mouths with groynes and Neogene storm and post-storm conditions; and (c) Group 3 structure or low-energy thanatocoenosis, characteristic of Recent, progradational coastal areas and present in the Recent–Neogene deeper areas analyzed in this paper (30–40 m depth). This separation is mainly controlled by intrinsic factors (i.e. the natural growth of this species), whereas the extrinsic factors (i.e. the hydrodynamic levels) are only a minor cause of the distribution of this species in the area studied.

The use of clay minerals and microfossils in palaeoenvironmental reconstructions: The Holocene littoral strand of Las Nuevas (Donana National Park) SW Spain

Abstract Three steps have been established during the Holocene formation of the bar-built estuary of Las Nuevas (Doñana National Park, Spain), on the basis of the clay mineralogy variations and the palaeontological record. The first step is characterized by the presence of ostracodes and homogeneous quantities of clay minerals (17−20% illite, 25−29% smectites), values of smectite (0.64− 0.70) and illite (0.60−0.70) crystallinity indexes, and the ratio of AlVI/(FeVI + MgVI) in illite (0.46− 0.47). This zone is interpreted as a very shallow lagoon with euryhaline conditions. The presence of roots, the progressive disappearance of foraminifers and an increase in the smectite content (up to 35%) define the second step. A salt-marsh environment with low-energy hydrodynamic conditions is deduced for this zone. The third step is characterized by an increase in illite content (up to 35%), and a decrease of the smectite content (up to 21%). The smectite crystallinity index decreased to 0.38, whereas the illite ratio AlVI/(FeVI + MgVI) decreased to 0.36. In this zone, the ostracode assemblage contains numerous juvenile stages of coastal species coinciding with lumachelle accumulations of the estuarine bivalves, abundant foraminifers and the presence of charophytes. This zone represents a strong marine input, probably caused by storms.

Coastal Dunes and Marshes in Doñana National Park

Donana Natural Park is a good global example of the sedimentary filling of a broad tidal estuary during the Mid-Late Holocene, after the last postglacial sea-level rise. The timing of this rise is not well defined yet in the Gulf of Cadiz, since the oldest evidence of coastal sedimentation, located at the right bank of the mouth of the old Guadalquivir Estuary, dates back to ca. 5,000 years ago. The first evolutionary stages of the embayment indicate an obvious marine influence, dominated by waves and storms from the SW. Since ca. 4,000 years ago, protection provided by the growing coastal spit barrier of Donana favored the development of a sheltered marsh dominated by tides and fluvial currents. About 2,200 years ago, since the time Romans controlled the area, the estuary was dominated by marshlands with a wide lagoon at its mouth (Lacus Ligustinus), and the current landscape of Donana started to form. The evolution of the last 2,000 years includes the quick and continuous growth of coastal barriers by longshore drift, the origin of the present-day marshland landscape and the development of dune fields migrating inland towards the wetlands.

Holocene palaeoenvironmental evolution of Saltés Island (Tinto and Odiel estuary, SW Spain) during the Roman period (1st century BC–5th century AD)

A multidisciplinary analysis of Holocene sediments from Saltés Island (Tinto-Odiel estuary, SW Spain) has allowed to differentiate eigth sedimentary facies, according to their textural characteristics, internal structure, paleontology and archaeological content. Its interpretation and the chronological datings carried out reconstruct a transition from a sandy tidal plain to a final occupation by a Roman salting (cetaria) between the 1st century BC to 5th century A. This evolution includes the deposit of washover fans derived from high-energy events between the 1st century BC to 3th century AD. The integration of these new data with others from previous research has allowed partially complete the palaeoenviromental reconstruction of the marine domain of the Tinto-Odiel estuary.ResumenEl análisis multidisciplinar de sedimentos holocenos procedentes de la isla Saltés, situada en el estuario de los ríos Tinto y Odiel (SO de España), ha permitido diferenciar ocho facies sedimentarias, de acuerdo a sus características texturales, estructura interna, contenido paleontológico y restos arqueológicos presentes. Su interpretación y las dataciones cronológicas efectuadas han permitido reconstruir una transición desde una llanura mareal arenosa a la ocupación final de la zona por una factoría romana de salazones (cetaria) entre los siglos I BC y V AD. Esta evolución incluye el depósito de washover fans derivados de la acción de eventos de alta energía entre los siglos I BC y III AD. La integración de estos nuevos datos con otros procedentes de investigaciones previas ha permitido completar parcialmente la reconstrucción paleoambiental del dominio marino del estuario de los ríos Tinto y Odiel.