Search results for "stratigraphy"
showing 10 items of 904 documents
Water chemistry and abiogenic methane content of a hyperalkaline spring related to serpentinization in the Argolida ophiolite (Ermioni, Greece)
2018
Abstract Hyperalkaline mineral springs related to active continental serpentinization are a theme of growing interest since they may contain significant amounts of abiotic gas and have important implications for energy resource exploration, subsurface microbiology and astrobiology. We report the discovery of a new hyperalkaline (pH∼12) spring issuing in the Agioi Anargyroi monastery at Ermioni (Greece), connected to serpentinization of peridotites of the Argolis ophiolite. Two water samples have been collected from separated springs and analysed for the chemical composition of major, minor and trace elements, and isotopic composition (2H and 18O) of water by IC, ICP-OES, ICP-MS and IRMS, an…
Extraordinary rocks from the peak ring of the Chicxulub impact crater: P-wave velocity, density, and porosity measurements from IODP/ICDP Expedition …
2018
Joint International Ocean Discovery Program and International Continental Scientific Drilling Program Expedition 364 drilled into the peak ring of the Chicxulub impact crater. We present P-wave velocity, density, and porosity measurements from Hole M0077A that reveal unusual physical properties of the peak-ring rocks. Across the boundary between post-impact sedimentary rock and suevite (impact melt-bearing breccia) we measure a sharp decrease in velocity and density, and an increase in porosity. Velocity, density, and porosity values for the suevite are 2900–3700 m/s, 2.06–2.37 g/cm3, and 20–35%, respectively. The thin (25 m) impact melt rock unit below the suevite has velocity measurements…
Carbon isotope geochemistry and geochronological constraints of the Neoproterozoic Sirohi Group from northwest India
2012
a b s t r a c t The early Neoproterozoic carbonates of the Sirohi Group, northwestern India, were studied for geochronology as well as for oxygen and carbon isotopes across three different sections to understand their relationship with contemporaneous global events. New single zircon Pb-Pb evaporation data con- strain the age of the Sirohi Group between ca. 920 and ca. 820 Ma, though actual span for deposition of the carbonates may be little shorter taking into allowance the time for peneplanation. Narrow range in variation of 18O values is generally observed in the carbonate which is consistent with generally well-preserved original compositions. Two sections (SA and SS) out of the three t…
Petrography and high-resolution geochemical records of Lower Jurassic manganese-rich deposits from Monte Mangart, Julian Alps
2016
Deposits with unusually high Mn contents sampled at Monte Mangart in the Julian Alps include organic-rich marlstone and black shale with interbedded manganoan and siliceous limestone, which were deposited during the early Toarcian Oceanic Anoxic Event. Mn enrichment during that period has been related to global sea-level change coincident with increasing subsidence rate. The formation of Fe-Mn nodules, marking a hardground at the base of the Monte Mangart section, seems to be triggered by release of Mn from remote hydrothermal vents into a region of relatively elevated submarine topography where oxidizing conditions prevailed. However, very high Mn contents in carbonate phases above the har…
Palaeozoogeographical connections of the Devonian vertebrate communities of the Baltica Province. Part II. Late Devonian
2010
Abstract Late Devonian vertebrate communities within the Baltica zoogeographical Province are analysed for intra- and interprovincial connections. Components within the category of provincial endemics are used to assign the communities to a particular zoogeographical province. Marine and continental, presumably freshwater types of vertebrate dispersal are outlined. During the Late Devonian marine dispersal is displayed by ptyctodonts, struniiforms, and some dipnoans, and continental dispersal by psammosteids, acanthodians, and some arthrodires. Isolation of communities is reflected by predominance of local and provincial endemics; the majority of polydemics and cosmopolitans records wider c…
The rodents of the Pirro Nord fauna (Foggia, Southern Italy)
2013
The rodent fauna of various fissure fillings of the Pirro Nord karstic complex are examined here. They have been collected during several field caingns starting from the 70’s until 2006 and are here examined in a comprehensive matter. Hundreds of specimens of arvicolids, murids and, in much lower amount, Glirids have been recovered from several of these fissures. They belong to the species Allophaiomys ex gr. ruffoi, Myodes sp. Apodemus flavicollis and Muscardinus sp.
Fluctuations morphologiques et hétérochronies chez Toxaster (échinides, Crétacé inférieur)
2003
Resume Plusieurs etapes de la diversification du spatangue Toxaster au Cretace inferieur sont decrites a partir de l’analyse de six especes qui se succedent du Valanginien inferieur au Barremien sur la marge nord-ouest tethysienne. La description des variations morphologiques est fondee sur l’analyse de deux parametres angulaires qui permettent d’identifier trois modules sur le test. La comparaison des trajectoires ontogenetiques des especes T. granosus kiliani et T. retusus , prises comme references, suggere une interpretation heterochronique de type peramorphose. L’elargissement des comparaisons aux adultes des six especes demontre l’absence de peramorphocline, mais atteste que l’evolutio…
Données nouvelles biochronologiques et paléoécologiques sur le bassin sédimentaire côtier du bénin entre le crétacé supérieur et l'éocène basal (Afri…
1998
Resume Un sondage carotte (Ouinhi) et des couples levees dans la carriere d'Onigbolo, situee a une vingtine de kilometres du forage, sur la partie aujourd'hui on-shore du bassin sedimentaire cotier beninois, ont fait l'objet de ce travail. Les conditions paleoenvironnementales, fort inegales d'un niveau a l'autre, imposaient une etude pluridisciplinaire, aussi bien sedimentologique que paleontologique. Les resultats obtenus, a partir des foraminiferes, ostracodes et palynomorphes, fournissent des donnees biostratigraphiques et paleoecologiques nouvelles, apportant des complements a la connaissance de l'histoire de ce bassin entre le Cretace terminal et l'Eocene basal. La grande rarete de do…
Empreintes et pistes de rhinocerotidae (Mammalia, Perissodactyla) du gisement pliocène terminal de Laetoli (Tanzanie)
1993
Resume Les traces (empreintes et pistes) des rhinoceros actuels sont tres mal connues, et une seule empreinte fossile de rhinoceros neogene ou quaternaire a ete decrite a ce jour. A Laetoli 7 sites ont livre des traces de rhinoceros, toutes attribuables au nouvel ichnogenre Dicerotinichnus; les traces des sites H, I et J ne sont pas definissables specifiquement. Les traces des sites A et N (deux pistes dont une a 26 couples d'empreintes et une a 5 couples dont certains de tres bonne qualite) permettent de definir le nouvel ichnobinome Dicerotinichnus laetoliensis nov. sp. attribue a Ceratotherium praecox. Les traces des sites M West et M East (deux pistes a 4 et 8 couples d'empreintes et 4 …
Succession des faunes d'ammonites au Langenegggrat (Préalpes médianes, région de Thoune, Suisse): Une série de référence dans le Sinémurien supérieur
1987
Resume Las succession detaillee des peuplements d'ammonites recoltes dans le Sinemurien superieur (Lotharingien) du Langenegggrat est presentee ici. Ces faunes, qui se repartissent en 5 associations stratigraphiquement distinctes, appartiennent a la partie superieure de la zone a Oxynotum et a la zone a Raricostatum. L'une de ces associations est particulierement originale; elle caracterise la base de la sous-zone a Macdonnelli et est largement dominee par Paltechioceras boehmi. Ces resultats conduisent a un affinement de la biostratigraphie du Sinemurien superieur de cette region et permettent une meilleure comprehension de la paleobiogeographie des regions alpines au cours du Lias inferie…