Search results for "Ocean"
showing 10 items of 2919 documents
L'arbre de la vie a-t-il une structure fractale?
1999
Abstract We analyse the time sequences of major evolutionary leaps at various scales, from the scale of the global tree of life, to the scales of orders and families such as sauropod dinosaurs, North American fossil Equidae, rodents, and primates including the Hominidae. In each case we find that these data are consistent with a log- periodic law to high level of statistical significance. Such a law is characterized by a critical epoch of convergence Tc specific to the lineage under consideration and that can be interpreted as the end of that lineage's capacity to evolve.
Climate change at the 4.2 ka BP termination of the Indus valley civilization and Holocene south Asian monsoon variability
2003
[1] Planktonic oxygen isotope ratios off the Indus delta reveal climate changes with a multi-centennial pacing during the last 6 ka, with the most prominent change recorded at 4.2 ka BP. Opposing isotopic trends across the northern Arabian Sea surface at that time indicate a reduction in Indus river discharge and suggest that later cycles also reflect variations in total annual rainfall over south Asia. The 4.2 ka event is coherent with the termination of urban Harappan civilization in the Indus valley. Thus, drought may have initiated southeastward habitat tracking within the Harappan cultural domain. The late Holocene drought cycles following the 4.2 ka BP event vary between 200 and 800 y…
Boat traffic in Lampedusa waters (Strait of Sicily, Mediterranean Sea) and its relation to the coastal distribution of common bottlenose dolphin (Tur…
2010
The volume of boat traffic and its potential connection to the coastal distribution of the common bottlenose dolphin (Tursiops truncatus) was evaluated off Lampedusa Island (Strait of Sicily). From July to September 2006 daily surveys were carried out at eight sites along the coast, three times a day, to assess the number, type, and size of boats moving, fishing, or stationed in Lampedusa waters. The study area was divided into four geographic areas: northwest, northeast, southwest, and southeast. Data were analyzed to determine the difference in the number of boats among the areas, sampling months, and times of day. The presence of dolphins was monitored by standardized land-based observat…
Coupures morphologiques et biochronologie chez les Kosmoceratinae de l'Est de la France (Callovien inférieur pp. à Callovien supérieur pp.)
1998
Abstract For the first time in eastern France, a detailed succession of the uppermost Lower Callovian to Lower Upper Callovian Kosmoceratinae is presented, according to the fossils collected in situ at Blye (Jura, France). It is compared with the abundant data from Champagne and Bourgogne. These ammonites may allow more accurate correlations between the subboreal and subtethysian biostratigraphical frameworks. They record numerous morphological changes, sometimes different from those generally accepted. They allow the precise recognition of the limits of the biostratigraphical units, and the definition of successive faunal units available in the lowermost Upper Callovian.
Coralline algal growth-increment widths archive North Atlantic climate variability
2011
Over the past decade coralline algae have increasingly been used as archives of paleoclimate information. Encrusting coralline algae, which deposit annual growth increments in a high Mg-calcite skeleton, are amongst the longest-lived shallow marine organisms. In fact, a live-collected plant has recently been shown to have lived for at least 850 years based on radiometric dating. While a number of investigations have successfully used geochemical information of coralline algal skeletons to reconstruct sea surface temperatures, less attention has been paid to employ growth increment widths as a temperature proxy. Here we explore the relationship between growth and environmental parameters in …
Eurhomalea exalbida (Bivalvia): A reliable recorder of climate in southern South America?
2012
Abstract Due to the lack of suitable high-resolution archives, regional and continental-scale climate dynamics of southern South America are not well understood. Shells of the long-lived, shallow-marine bivalve mollusk, Eurhomalea exalbida (Dillwyn), are likely to contain information on the past water temperatures. As yet, however, no rigorous calibration study has been presented so that growth history traits and the reliability of shell oxygen isotope-based temperature estimates remain unknown. Shell growth patterns and oxygen isotope ratios of four young specimens of E. exalbida from the Falkland Islands (Southwest Atlantic) were analyzed and cross-calibrated with environmental parameters…
Accurate increment identification and the spatial extent of the common signal in fiveArctica islandicachronologies from the Fladen Ground, northern N…
2009
[1] The creation of networks of shell-based chronologies which can provide regionally extensive high-resolution proxies for the marine environment depends on the spatial extent of the common environmental signal preserved in the shell banding and on the reliability of the dating model. Here Arctica islandica chronologies from five neighboring sites in the North Sea are compared, and the strength of the common environmental signal across distances up to 80 km is analyzed using statistical techniques derived from dendrochronology. The signal is found to be coherent across these distances. In a linked study, chronologies based on one of the same sites but constructed by two different research …
Unique growth pattern of Metoposaurus diagnosticus krasiejowensis (Amphibia, Temnospondyli) from the Upper Triassic of Krasiejów, Poland
2013
Morphology and bone histology of femora, tibiae, and fibulae of the temnospondyl Metoposaurus diagnosticus krasiejowensis from the Upper Triassic locality of Krasiejow (Poland) are studied for the first time. The growth pattern of Metoposaurus as preserved in a small growth series of femora, shows a regular alternating sequence of fast and slow growth phases, which are interpreted as representing zones and annuli. The slow growth phases (annuli) of the inner and outer cortex as well as those of different specimens are of a regular broad thickness. Such broad annuli are so far unknown for any vertebrate and make the growth pattern for Metoposaurus unique. These slow growth phases always cont…
The unique skeleton of siliceous sponges (Porifera; Hexactinellida and Demospongiae) that evolved first from the Urmetazoa during the Proterozoic: a …
2007
Abstract. Sponges (phylum Porifera) had been considered as an enigmatic phylum, prior to the analysis of their genetic repertoire/tool kit. Already with the isolation of the first adhesion molecule, galectin, it became clear that the sequences of the sponge cell surface receptors and those of the molecules forming the intracellular signal transduction pathways, triggered by them, share high similarity to those identified in other metazoan phyla. These studies demonstrated that all metazoan phyla, including the Porifera, originate from one common ancestor, the Urmetazoa. The sponges evolved during a time prior to the Ediacaran-Cambrian boundary (542 million years ago (myr)). They appeared du…
Une faune très diversifiée du Pléistocène inférieur de la Sierra de Quibas (province de Murcia, Espagne)
2001
The Quaternary karstic site of Sierra de Quibas (Abanilla, province of Murcia, Spain) has provided a wide faunal list with more than 60 species. The assemblage of the taxa Arvicola deucalion, Castillomys rivas rivas, Eliomys intermedius, Equus altidens, Capra sp. aff. C. alba and cf. Praeovibos allows the correlation with other Spanish Lower Pleistocene sites in the Betic Cordillera, as Plines 1, Orce 3 and Venta Micena. Therefore Quibas can be located between 1.3 and 1.0 Ma. The palaeoenvironmental features of the area around the karstic cavity and the palaeoclimatic regime are inferred.