Juan Ignacio Baceta

Comparative ecological analysis of the ostracod faunas from low- and high-polluted southwestern Spanish estuaries: a multivariate approach

Abstract The distribution and abundance of both living and total ostracod populations from the estuaries of the southwestern Spanish coast are discussed. A total of 68 species were obtained from 120 bottom samples collected in the channels, channel margins and salt marshes. Four assemblages were recognized in this area: (a) Urocythereis oblonga assemblage, with marine species well-represented in sandy substrates located near the mouths; (b) Loxoconcha rhomboidea assemblage, mainly developed in the quiet tidal channels conected with the main channels of the marine domains; (c) Loxoconcha elliptica assemblage, enclosing the most cosmopolitan and euryhaline species, very abundant in muddy sediments and low to moderate hydrodynamic conditions; and (d) Leptocythere porcellanea assemblage, only observed in the clayey-silty channel margins of the most protected ebb channels. In these transitional environments, very unfavorable conditions for the ostracod development were found in: (a) the erosional channels and channel margins; (b) most of the salt marsh samples with high subaerial exposure; and (c) sectors with high metallic pollution levels and acidic waters.

Did the Late Paleocene thermal maximum affect the evolution of larger foraminifers? Evidence from calcareous plankton of the Campo Section (Pyrenees, Spain)

The larger foraminifer turnover (LFT), which marks the base of the Ilerdian stage, may be related to the Late Paleocene Thermal Maximum (LPTM), or be at least nearly coeval with that climatic event. Thus, the impact of the LPTM may have been greater than hitherto realised, having also affected mid-latitude shallow-marine biota. This conclusion has been reached after a re-study of the calcareous plankton of the uppermost Paleocene and lowermost Eocene interval of the Campo section in the central southern Pyrenees. Campo is an important reference section because it contains larger foraminifers, planktic foraminifers and calcareous nannofossils, and their co-occurrence was used to intercalibrate their respective zonal schemes. Previous studies at Campo placed the onset of planktic foraminiferal Zone P5 near the base of the Ilerdian, and the calcareous nannofossil NP9/NP10 chronal boundary (sensu Bybell, L.M., Self-Trail, J.M., 1995. Evolutionary, biostratigraphic and taxonomic study of calcareous nannofossils from a continuous Paleocene/Eocene boundary section in New Jersey. US Geol. Surv. Prof. Pap. 1554, pp. 1‐36) not less than 150 m above the Ilerdian lower limit. By these estimates, the LPTM (known to have occurred in the middle part of Zone P5 and just before the NP9/NP10 boundary) would be an event much younger than the LFT. However, our reexamination of planktic foraminifers suggests that the base of the Ilerdian is probably situated at the middle of Zone P5 (a possibility proposed by Hillebrandt in 1965, but denied by later authors). For instance, Morozovella occlusa has been found for the first time in the Campo section. Its Last Appearance Datum (LAD), which in the Pyrenees was approximately coeval with that of Morozovella velascoensis (event used to place the top of Zone P5), has been identified in beds situated less than 70 m above the base of the Ilerdian. Such thickness represents a time span of a similar magnitude as the one which separated the LPTM and the LAD of M. occlusa in the deep-water hemipelagic succession of the Basque Basin, in the western Pyrenees. Autochthonous calcareous nannofossils are neither abundant nor well preserved in most of the studied interval, with Rhomboaster bramlettei (the marker of the base of Zone NP10) being extremely rare in lower and middle Ilerdian beds, a fact that makes it very difficult to fix the position of the NP9/NP10 boundary in the Campo section. However, the bases of zones NP9 and NP11 have been located, and they support the zonation with planktic foraminifers. These new data suggest that the LFT and the LPTM may have been coeval or nearly so, a possibility reinforced by correlation with sections of the Basque Basin. Specialists of larger benthic foraminifers can easily delineate the LFT in shallow water carbonate successions of the Tethys domain, and they propose to place the Paleocene/Eocene boundary at the base of the Ilerdian stage. On the other hand, the deep

Los ostràcodos actuales de la laguna de Venecia (NE de Italia)

In the Venice lagoon, ostracods from 99 recent samples were studied. The biocoenosis is more abundant in the inner margin, near some little channels. The microfaunal analysis delimited three estuarine associations, with numerous valves of Cyprideis torosa, and one marine association (Pontocythere turbida). Salinity, hydrodynamics, nutrients and substrate are the main factors which control the distribution of these microorganisms. This distribution is very similar in other recent lagoons of Italy.

Total benthic foraminifera assemblages in the southwestern Spanish estuaries

Abstract One hundred and twenty-one samples were collected in three estuaries of the Huelva littoral (SW Spain). The 12,923 individuals picked were assigned to forty-seven species. The analysis of the foraminiferal percentages allows the distinction of seven assemblages: two salt marsh assemblages ( Trochammina inflata and Jadammina macrescens ), four assemblages widely represented both in the channel margins and the channels ( Ammonia inflata, Astrononion stelligerum, Cribroelphidium vadescens, Ammonia ammoniformis ) and one marginal marine assemblage ( Ammonia beccarii-Quinqueloculina spp). The distribution of these assemblages is controlled by the salinity, the altitude above the lowest tidal level and, to a lesser extent, by the grain size, organic matter and the test transport. In the Tinto-Odiel estuary, both effects of heavy metal pollution and sedimentary changes in the foraminiferal distribution were analyzed, indicating some recuperation mainly in the Odiel river, one of the most polluted areas of the world.

Un nouveau site a vertebrés continentaux de l´Eocene superieur de Zambrana (Bassin de Miranda-Treviño, Alava, Pays Basque).

Resume Des fouilles recentes dans lEocene superieur de Zambrana (Alava, Pays basque) ont livre des restes devertebres continentaux, les premiers decouverts dans le bassin tertiaire de Miranda-Trevino. Lassociation fossile est composee de tortues (Chelonii indet.), crocodiliens ( Diplocynodon sp.) et mammiferes, qui comprennent de possibles insectivores (Lipotyphla indet.), carnivores (cf. Quercygale sp.), rongeurs ( Theridomys aff. golpei, Elfomys aff. parvulus , Pseudosciurinae indet., Glamys priscus ), artiodactyles (Xiphodontidae indet.) et perissodactyles ( Paranchilophus sp., Plagiolophus aff. mazateronensis, Palaeotherium sp.). Lassociation de rongeurs et de perissodactyles suggere un âge ludien (Priabonien) moyen-inferieur, correspondant a la biozone MP 18. La faune de mammiferes de Zambrana est comparable aux faunes endemiques de lEocene moyen-superieur des bassins iberiques occidentaux et centraux. Les depots fossiliferes sont des marnes et des calcaires a niveaux de charbon, dorigine lacustre. Letude geologique de la region indique que le bassin tertiaire de Miranda-Trevino a ete fortement influence par lactivite tectonique regionale et que les premiers mouvements compressifs importants lies a la phase pyreneenne de lorogenese alpine ont eu lieu pendant lEocene inferieur.

TRANSGRESSIVE SEQUENCES ON FORELAND MARGINS: A CASE STUDY OF THE NEOGENE CENTRAL GUADALQUIVIR BASIN, SOUTHERN SPAIN

The Guadalquivir foreland basin, located between the Iberian basement northward and the Betic orogen to the South, represents the western sector of the earlier foredeep basin of the Betic Cordillera. Along the northern foreland margin, the sedimentary fill of this basin includes a Tortonian Basal Transgressive Complex (BTC), composed of five internal sequences bounded by transgressive surfaces. Two main parts are distinguished within each sequence: the lower transgressive lag deposits, and the upper stillstand/prograding sediments. Three facies associations were distinguished within this stratigraphic succession along the central sector of this basin margin: unfossiliferous conglomerates and coarse-grained sands (A), fossiliferous conglomerates and coarse-grained sands (B), and yellow medium-coarse-grained fossiliferous sands (C). A fourth facies association (D: blue silty marlstones and shales) overlies the BTC. Deposits of alluvial sediments (facies association A) and shallow-marine/foreshore sediments (facies association C), were recurrently interrupted by transgressive pulses (facies associations B and C). Every pulse is recorded by an erosional, cemented sandy-conglomerate bar with bivalves (Ostreidae, Isognomon ), balanids, gastropods and other marine bioclasts; or their transgressive equivalents. The lateral facies changes in each individual sequence of the BTC are related to: (1) the influence on the northern foreland margin of the tectonic activity of the southern orogenic margin; (2) the palaeorelief formed by irregularities of the substrate which controls the sediment dispersal; and (3) the evolution stages of the sedimentary systems.

El género Heterostegina (Nummulitidae, Foraminifera) en el Mioceno superior del SO de España

Systematic study of specimens belonging to the genus Heterostegina from coquilla levels in the basal sandstone unit of the Neogene series in the western part of the Guadalquivir Basin (SW Spain). The specific determination of these specimens allows us to revise and emend the species Heterostegina gomez-angulensis Perconig. For the first time we describe and figure the microspheric generation of this species. The redescription of the megalospheric forms has permitted to differentiate two morphotypes. We discuss their chronostratigraphic significance.