Search results for "Ocean"

The recovery and radiation of Early Jurassic ammonoids: morphologic versus palaeobiogeographical patterns

2001

Abstract The recovery and radiation of the Early Jurassic ammonoid morphospace, as represented by nine morphologic groups identified in an earlier study, are traced through the first 36 subzones of the Hettangian to Domerian time interval. A quantitative survey of the dispersion of 436 species over 15 palaeogeographical areas reveals seven palaeobiogeographical patterns, each corresponding to an exclusive set of species exhibiting similar characteristics in terms of distribution and abundance. This study combines morphologic, chronostratigraphical, and palaeobiogeographical data in an attempt to investigate possible connections between morphologic recovery and radiation patterns and the his…

Thermal evolution of Tethyan surface waters during the Middle-Late Jurassic: Evidence from δ18O values of marine fish teeth

2003

[1] Oxygen isotope compositions of phosphate from vertebrate tooth enamel were measured to determine the evolution of tropical sea surface ( 0‰ owing to limited growth of continental ice during the early middle Oxfordian. The resulting sea level fall is estimated to be at least 50 m and is compatible with a global regression stage. The middle Oxfordian thermal minimum is followed by a new warming stage of 3–4°C from the middle to the late Oxfordian.

Reconstitution du squelette d'astérides fossiles à partir d'ossicules isolés : intérêt taxinomique et phylogénétique

1999

Abstract Dissociated ossicles of asteroids are frequent in neritic sediments. Until now, this material was mainly used in the identification of species. A new method, associating a morphological analysis and counting of plates, allows the architecture of the skeleton and the shape of the body to be reconstructed. This method provides new elements for taxonomic and phylogenetic comparisons. It also provides indications on the adaptation of the asteroids to their environment. In geological beds, frequencies of the different kinds of plates will allow qualification of bioerosion and taphonomic sorting.

The role of geochronology in understanding continental evolution

2010

Geochronology has become one of the most essential tools in reconstructing processes of continental growth and evolution, and in situ dating of minerals has become common practice through the development of high-resolution ion microprobes and laser ablation inductively coupled plasma mass spectrometry techniques. Zircon has established itself as the most robust and reliable mineral to record magmatic and metamorphic processes. The combination of mineral ages with Sm–Nd, Lu–Hf and O isotopic systematics constrains magma sources and their evolution, and a picture is emerging that supports the beginning of modern-style plate tectonics in the early Archaean. Major fields for future research in …

Shallow-marine carbonates of the tropical-temperature transition zone: effects of hinterland climate and basin physiography (late Miocene, Crete, Gre…

2006

A new breath of life for anoxia.

2008

The middle of the Cretaceous (120–80 Ma) was one of the warmest periods of the past 300 m.y., with tropical sea-surface temperatures well over 30 °C ([Puceat et al., 2007][1]; [Forster et al., 2007a][2]) and atmospheric CO2 levels much higher than today. Therefore this period can give us crucial

Metazoan calcium carbonate biomineralizations: macroevolutionary trends – challenges for the coming decade

2014

AbstractCalcium carbonate-based biominerals, also referred as biocalcifications, are the most abundant biogenic mineralized products at the surface of the Earth. In this paper, we summarize general concepts on biocalcifications and we sketch macro-evolutionary trends throughout the history of the Earth, from Archean to Phanerozoic times. Then, we expose five fundamental issues that represent key-challenges in biocalcification researches for the coming decade: the first one concerns the comprehension of the micro- and nano-structure of calcium carbonate biominerals from a mineral viewpoint, while the second one deals with the understanding of the dynamic process of their fabrication. The thi…

Late Hercynian Plate and Intraplate Processes within Europe

1987

The Hercynian orogenic belt of Europe consists of a central crystalline ridge which is accompanied on both sides by a rather unmetamorphosed foldbelt. It is speculated that the crystalline ridge represents some kind of island arc system underlain by a segment of continental crust. On both sides this island arc system was involved in subduction of oceanic crust, first of the Mideuropean Sea in the North and then of the Paleotethys in the South. When the continental areas to the north and south of the oceanic areas (North America/Northern Europe and Africa) finally got involved in the subduction processes, continent/continent collision took place on both sides of the island arc system. The tw…

A sequence analyzed from the basin to the platform : the Middle Oxfordian calcareous succession in southeastern France

2004

Abstract Middle Oxfordian sedimentation is very homogeneous in southeastern France. It is characterized by a specific alternation of marls and fine-grained limestones (G. transversarium Zone). This work shows that sets of calcareous beds allow accurate stratigraphic correlations in various paleogeographic areas, from the shallow Jura platform to the deep Dauphinois basin. Following a rifting period, this sedimentation illustrates a doming period with decreasing subsidence and water depth. This corresponds to the establishment of a wide marine area more favourable to carbonate sedimentation. Considering sequence stratigraphy, some slight variations occur in the sediment record and lead to in…

Contrôle géodynamique de la sédimentation argileuse du Callovien-Oxfordien moyen dans l'Est du bassin de Paris: influence eustatique et volcanique

1999

The Middle Callovian to Middle Oxfordian clay deposits drilled in the eastern Paris Basin (borehole HTM 102, ANDRA) show a strong mineralogical change occurring in the lowermost Oxfordian (Scarburgense subzone, Mariae zone). Such a change probably results from the initial development of connections between the young Atlantic Ocean and the Paris Basin. A bentonitic layer identified close to the boundary between Lower and Middle Oxfordian and also recognized in the subalpine Basin (South-East of France) at the same age, reflects a volcanic activity probably resulting from an extensional regime located in the North Sea.