Quaternary Palaeoenvironmental Changes in South Spain
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QUATERNARY PALAEOENVIRONMENTAL CHANGES IN SOUTH SPAIN R. YLL (1) *,C ZAZO (2), J.L. GOY (3), R PÈREZ-OBIOL (1), J. PANTALEÓN-CANO(1) , J. CIVIS (3), C. DABRIO (4), A. GONZÁLEZ (3), F. BORJA (5), V. SOLER (6), J. LARIO (7), L. LUQUE (3), F. SIERRO (3), F. M. GONZÁLEZ-HERNÁNDEZ (3), A.M. LEZINE (8), M. DENEFLE (9), & J.M. ROURE (1). (1) Unitat de Botànica. Facultat de Ciències. Universitat Autònoma de Barcelona. 08193-Bellaterra (Barcelona), Spain. (2) Departamento de Geología, Museo Nacional de Ciencias Naturales, CSIC. 28006-Madrid, Spain. (3) Departamento de Geología. Facultad de Ciencias. Universidad de Salamanca. 37008-Salamanca, Spain. (4) Departamento de Estratigrafía, Facultad de Geología, Universidad Complutense, 28040-Madrid, Spain. (5) Área de Geografía Física, Facultad de Humanidades, Universidad de Huelva, 21007-Huelva, Spain. (6) Instituto de Productos Naturales y Agrobiología. CSIC. 38206-La Laguna (Tenerife), Spain. (7) Área de Geodinámica, Facultad de Ciencias del Medio Ambiente, Universidad de Castilla-La Mancha, 45071-Toledo, Spain. (8) ESA 7073 CNRS/UPMC, Jussieu Boîte 106, 75252 France. (9) URA 141 CNRS, Geographie Physique, Meudon 92195, France. * [email protected] ABSTRACT This paper presents the existing differences between the evolution of the Holocene landscape of the Southeastern and Southwestern areas of the Iberian Peninsula. Moreover, some palaeoenvironmental characteristics of OIS 4 and OIS 3 of the western Andalusia appear. The five presented sequences have been analyzed from palynological and geomorphological point of view. The obtained results show that during the Holocene no significant forest cover existed in the eastern area and that the different phases identified mainly show an alternation of shrub and steppe communities, taking place during the fifth millennium a radical transformation of the landscape and the definitive establishment of the semi-desert conditions that are registered at the present time. In the western area the evolution of the landscape is determined basically by the changes of geomorphological conditions of the coast and the marshland zones of the Guadalquivir and the Tinto-Odiel systems, registering diverse moments of increase of the aridity conditions, without remarkable changes in the vegetal landscape. Sequences obtained do not provide evidence of indicators of human intervention that might be clearly attributable to the pattern of human activities established in the area until a the two millennium ago. KEYWORDS Pleistocene, Holocene, Climatic Change, Pollen, South Spain INTRODUCTION a reduced arboreal cover and has strongly been influenced by erosive processes that have made appear The south of the Iberian Peninsula fundamentally “semi-deserts”. Meanwhile, in the western zone, open presents certain characteristics due to the dryness to Atlantic influence, the Guadalquivir river and its specially in the coastal zones and inner depressions. extensive estuary and marshy zone and the Tinto-Odiel Simultaneously, the existence of important mountains, system conform extensive damp zones. rivers and very extensive marshes zones allows the During the last years, diverse works have studied existence of “islands” with substantial bioclimatic these territories from a palaeobotanical and differences that allow the existence of different palaeogeomorphological perspective (Menendez-Amor ecosystems. In the Eastern zone, the territory presents & Florschütz, 1964; Stevenson, 1985; Stevenson & 1 Moore, 1988; Stevenson et al., 1992, 1999; Zazo et average temperature is 16,7 °C and the precipitation al., 1996, 1999; Dabrio et al., 2000, for the western is 537 mm. More to the north, in the city of Huelva, zone; and Munuera & Carrión, 1991; Yll et al., 1994; next to the Lagoon of Las Madres, the low precipitation Mariscal, 1994; Burjachs & Riera, 1995; Esteban, up to 465 mm and the mean annual temperature is 1995; Riera et al., 1995; Carrión et al., 1995, 2000; 16°C. Rodriguez et al., 1998; Lario et al., in press.; Pantaleón- Cano, 1998; Pantaleón-Cano et al., in press; Goy et al., in press, for the Eastern zone). Vegetation This paper presents a new perspective on The natural vegetation of Laguna de las Madres differentials processes of both zones after new cores belongs to the “dry thermomediterranean” type (Rivas and works. A palaeoecological approach to these Martínez, 1987). The mainly formations are composed differentiated territories has an important value facing by Olea sylvestris, Quercus suber, Juniperus oxycedrus, the evolution with the landscape and the means and Pistacia lentiscus y Chamaerops humilis. Secondary that in addition has undergone important formations dominated by Ericaceae and Cistaceae transformations by an intense and prolonged human shrubs are well developed. At the bottom of the action. depression, the hydrophilous vegetation includes Cyperaceae (Cladium mariscus),Typha, Hydrocotyle, Phragmites and ferns (Dryopteris, Thelypteris); STUDY AREA cultivated areas of Pinus pinea and Fragaria ananassa occur in the surroundings . The western area The vegetation of the National Park of Doñana In the western zone three new sequences have is dominated by Mediterranean scrub in the high zones been studied. One of them in the Las Madres lagoon (Rosmarinus officinalis, Thymus vulgaris, Cistus…) and in the estuarine system of Tinto-Odiel and the other by atlantic scrub type in the depressions, where two in the marshland zone of the mouth of the Gua- dominate the moorlands. Pinus Pinea, Quercus suber, dalquivir river; one in the Lucio of Mari Lopez and the Pistacia lentiscus and Arbutus unedo are also present. other in the coast, in Marismillas, both within the limits The southern end of this protected space is occupied of the National Park of Doñana (Fig. 1). by a coastal dune barrier in which the vegetation is practically nonexistent. The inter-dunes depressions are covered by abundant adapted vegetation, like the Geology Armeria arenaria, Carex and Artemisia campestris. In Due to the geographical proximity of Las Ma- addition to the Pinus pinea, there are dispersed units dres lagoon and the mixed wave-and tide-dominated of junipers and savins. In the zones of salt marsh, the Odiel-Tinto estuary, their Holocene evolution is closely dominant vegetation is Salicornia and the rush. They related. At present, the main estuary is almost exist dense formations of scrub, known as “monte blan- completely filled and largely separated from the open co”, when the Cistaceae and Labiatae abound, and sea by an estuarine barrier that includes the spit systems as “monte negro” in the case of xerophytic scrub of Punta Umbría, Isla Saltes, and Punta Arenilla. vegetation with important presence of “brezos”. The Mari López drill core was recovered from Occupying the most internal zones, in transition the inner parts of the present Guadalquivir estuary, between dunes and the salt marshes, they are the that is enclosed by the spits of Doñana and La Algai- formation of more extensive and compact pine groves da. A multidisciplinary study of the core permitted to of the Park, known like Pinares de Marismillas. recognise several intervals that represent diverse changing eustasy, climate, and neotectonics. Marismillas core is located landwards of the dune The eastern area ridges of Doñana spit, near the limit with the present tidal flats in the lowlands. The lowermost 35m of the Pollen sequences from eastern area were core penetrated blue marlstones of Miocene age (–75 obtained in the coastal fringe of the province of to –100 m) and fluvial conglomerates (–75 to –65m). Almería. The Antas sequence was recovered in the The overlaying blue marls (–65 to –60m) record the lower course of the river Antas, in the Vera basin. The Holocene transgressive deposits (6660 yr. BP), and Vera basin, with an area of 500 square km, is crossed non-dated transitional environments. The topmost by Almanzora, Aguas and Antas watercourses that are 43m were deposited during the last 2300 yr. practically dry during most of the year. The San Ra- Sedimentary environments changed in ascending order fael pollen sequence are located on the south coast of from lacustrine to paludal, spit bar and aeolian dunes. the province, at the eastern edge of the Campo de Dalías, in a formerly marshy zone. The Campo de Dalías has a low relief but is bounded to the north by Climate the southern spurs of the Sierra de Gádor, which rises In the existing metereological station in the same steeply to altitudes of over 2000 m above sea level. Park, in the Palace of Doñana, the registered annual 2 Figure 1.- Maps showing locations of the studied sites. 3 Geology Artemisia barrelieri, etc. Beyond the domain of salt- Geologically the areas studied are included within marshes, vegetation is patched by a diversity of dense the structural unit constituted by the Betic mountain brush dominated eventually by Maytenus senegalensis systems of the Iberian Peninsula. Between the mountain subsp. europaeus, Withania frutescens, Ziziphus lotus, massifs there are Neogene and Quaternary basins, Asparagus albus, Asparagus horridus, Rhamnus which as post-orogenic units represent the filling of the oleoides var. angustifolia, Chamaerops humilis, Olea troughs with autochthonous materials spanning from europaea var. sylvestris, Pistacia lentiscus and Ephedra the Miocene to the Quaternary. fragilis. Characteristic coastal communities on rocky In the Vera basin, where the Antas core was substrates are dominated by the endemic Periploca extracted, important