Search results for "STRATIGRAPHY"

A terminal Cretaceous giant pterosaur from the French Pyrenees

1997

A very large pterosaur cervical vertebra is described from the Upper Maastrichtian deposits of Mérigon, in the foothills of the French Pyrenees. It resembles the vertebrae of Quetzalcoatlus, from the Maastrichtian of Texas, more than those of Arambourgiania, from the Maastrichtian of Jordan. The estimated wing span of the Mérigon pterosaur is close to 9 m, which makes it one of the largest known flying creatures. Giant pterosaurs still had a wide geographical distribution at the end of Maastrichtian time, which is not suggestive of a declining group, although it is difficult to obtain an accurate estimate of taxonomic diversity of terminal Cretaceous pterosaurs on the basis of available dat…

Plio-Pleistocene geological evolution of the northern Sicily continental margin (southern Tyrrhenian Sea): new insights from high-resolution, multi-e…

2003

High-resolution seismic profiles were acquired in the north Sicily offshore region with an innovative, multi-tip sparker array which lacks ringing and has a base frequency around 600 Hz. The new data, combined with published data, suggest that intra-slope and extensional basins formed as a consequence of the late Miocene (?)–early Pliocene shortening and thrusting, and the middle (?)–late Pliocene continental rifting affecting the internal side of the Sicilian-Maghrebian chain. Early (?) Pleistocene to Holocene high-amplitude and high-frequency sea-level changes resulted in repeated sub-aerial exposure and flooding of the shelf, and the deposition of cyclically arranged hemipelagic and shel…

Integrating facies and structural analyses with subsidence history in a Jurassic-Cretaceous intraplatform basin: Outcome for paleogeography of the Pa…

2016

Abstract We illustrate the tectono-sedimentary evolution of a Jurassic–Cretaceous intraplatform basin in a fold and thrust belt present setting (Cala Rossa basin). Detailed stratigraphy and facies analysis of Upper Triassic–Eocene successions outcropping in the Palermo Mts (NW Sicily), integrated with structural analysis, restoration and basin analysis, led to recognize and describe into the intraplatform basin the proximal and distal depositional areas respect to the bordered carbonate platform sectors. Carbonate platform was characterized by a rimmed reef growing with progradational trends towards the basin, as suggested by the several reworked shallow-water materials interlayered into th…

2015

Large volcanic eruptions are major geohazards, so identifying their frequency in the geologic record is critical for making predictions and hazard assessments. Following the discovery of a thick (18 cm) tephra layer in marine sediments from Integrated Ocean Drilling Program (IODP) Site U1396 between Montserrat and Guadeloupe in the Caribbean Sea, we document here how high-precision Pb isotopes, trace elements, and grain morphological analyses of the tephra can be used, together with volcanological models, to identify a large (Volcanic Explosivity Index ?6) Plinian eruption from Basse-Terre, Guadeloupe, at ca. 2.36 Ma. This previously unrecognized eruption is believed to be the largest docum…

Late Holocene erosion of the Canopic promontory (Nile Delta, Egypt)

2017

International audience; The mouths of the Nile Delta are sensitive coastal areas, their geomorphology primarily being mediated by relative sea-level rise and sediment supply. To further document the Holocene evolution of the Nile's Canopic mouth, a core was taken from the southern shores of Abu Qir Bay, close to the ancient Canopic channel. Core bio-sedimentology and chronostratigraphy highlight four stages of marine incursion which are juxtaposed upon the general progradation trend of the Nile coast in this area. Compiled age-depth points from sediment cores taken in Abu Qir Bay underscore two phases of negative sediment budget at the Canopic mouth: (1) a first period, between 3.5 and 2 ka…

Global aridity synthesis for the last 60 000 years

2019

Abstract. A compilation of published literature on the dust content in terrestrial and marine sediment cores are synchronised on the basis of pollen data and speleothem growth phases within GICC05 age constrain. Based on that, aridity patterns for ten key areas in the global climate system are reconstructed over the past 60 000 years. These records have different time resolutions and rely on different dating methods, thus of various types of stratigraphy. Nevertheless, all regions show humid conditions during the early MIS3 and early Holocene, but not always of the same timing. Such discrepancies have been interpreted as regional effects while also due to stratigraphical uncertainties. In c…

New insights into the magmatic-hydrothermal system and volatile budget of Lastarria volcano, Chile: Integrated results from the 2014 IAVCEI CCVG 12th…

2018

Recent geophysical evidence for large-scale regional crustal inflation and localized crustal magma intrusion has made Lastarria volcano (northern Chile) the target of numerous geological, geophysical, and geochemical studies. The chemical composition of volcanic gases sampled during discrete campaigns from Lastarria volcano indicated a well-developed hydrothermal system from direct fumarole samples in A.D. 2006, 2008, and 2009, and shallow magma degassing using measurements from in situ plume sampling techniques in 2012. It is unclear if the differences in measured gas compositions and resulting interpretations were due to artifacts of the different sampling methods employed, short-term exc…

Age and isotopic evidence for the origin of the Archæan granitoid intrusives of the Johannesburg Dome, South Africa

1999

Abstract Results of RbSr, PbPb and SmNd whole rock, Rbr biotite and PbPb zircon evaporation analyses are presented for certain granitoid rocks from the Johannesburg Dome. These data indicate that the granodiorite, granite and leucosome from migmatite were emplaced ∼ 3090 Ma ago, were genetically related and were derived primarily from a source between ∼ 3300 and ∼ 3500 Ma old. A portion of the granodiorite and granite might have been derived from a source between ∼ 4000 and ∼ 4300 Ma old. The tonalite was emplaced ∼ 3170 Ma ago and was derived from a source between 3.3 and 3.5 Ga old. RbSr biotite-whole rock ages, ranging between about ∼ 2614 and ∼ 2080 Ma, probably reflect complete r…

Birth and Early evolution of a Jurassic Escarpment: Monte Kumeta, Western Sicily

2002

The accurate reconstruction of the facies architecture in the Jurassic succession of Monte Kumeta, coupled with a detailed biostratigraphy, allow to define dynamics and genetic factors controlling the conversion of a Bahamian-type carbonate platform to a pelagic escarpment. A change from tidalites to oolites i.e. from the restricted, interior lagoon to a more open-marine sandy depositional environment, records the establishment of a basin south of the Monte Kumeta sector in late Hettangian-Sinemurian times. The oolitic limestones are overlain by earliest Carixian bioclastic grainstones and packstones with micritized grains and by wackestones with radiolarians and sponge spicules, organized …

Fluid escape structures in the north Sicily continental margin

2014

Abstract High resolution and multichannel seismic profiles coupled with multibeam echosounder (seafloor relief) data, acquired along the northern Sicily continental margin (southern Tyrrhenian Sea), document the occurrence of mound and pockmark features, revealing fluid escape processes. Along this margin, morphology of the high-gradient continental slope is irregular due to the presence of structural highs, slope failures and canyons, and is interrupted by flat areas at a mean depth of 1500 m. Seismostratigraphic analysis tools and methods were used to identify fluid escape structures and to work out a classification on the basis of their morpho-acoustic characteristics. The detailed 3D ba…