Search results for "CEO"

Organics versus clastics: conditions necessary for peat (coal) development

1990

Abstract The absence or lack of detrital influx into ancient peat-forming swamps is critical to the formation of low-ash coal. Modern and ancient coal-forming swamps of continental basins show a separation of peat and clastic sediments which is partially fault controlled. In the African rift valleys as well as in the Stephanian intermontane coal basins of France, thick peat free from clastic input may be the result of tectonic activity. In the paralic basins of Morocco (Westphalian B) and Nigeria (Late Cretaceous) coal occur landward of the shoreline turnaround and are related to a relative high stand of the sea, which curtailed detrital influx into the basins. Thus, peat formation occurred…

Jurassic Ophiolite Formation And Emplacement As Backstop To A Subduction-Accretion Complex In Northeast Turkey, The Refahiye Ophiolite, And Relation …

2013

International audience; The eastern Mediterranean region within the Tethyan realm shows a high concentration of ophiolites with contrasting times of formation and emplacement along the belt: In the Balkans, the ophiolites formed during the early to medial Jurassic, and were obducted during the late Jurassic, whereas in Turkey and farther east, structurally intact Jurassic ophiolites are rare and Jurassic ophiolite obduction is unknown. Here we report a structurally intact, large ophiolite body of early Jurassic age from NE Turkey, the Refahiye ophiolite, located close to the suture zone between the Eastern Pontides and the Menderes-Taurus block. The Refahiye ophiolite forms an outcrop belt,…

Diepoxyrollin and Diepomuricanin B:  Two New Diepoxyacetogenins from Rollinia membranacea Seeds

1997

Diepoxyrollin (1) and diepomuricanin B (2), two new Annonaceous acetogenins were isolated from the cytotoxic MeOH extract of the seeds of Colombian Rollinia membranacea. Five others known acetogenins were also isolated, dieporeticanin 1, dieporeticanin 2, diepomuricanin A, rollinone, and sylvaticin. Their structures were elucidated on the basis of spectral data. Compounds 1 and 2 belong to the rare type of diepoxyacetogenins, which are probably precursors of the mono-tetrahydrofuran acetogenins.

DIRECT EVIDENCE FOR CONDENSATION IN THE EARLY SOLAR SYSTEM AND IMPLICATIONS FOR NEBULAR COOLING RATES

2009

We have identified in an acid resistant residue of the carbonaceous chondrite Murchison a large number (458) of highly refractory metal nuggets (RMNs) that once were most likely hosted by Ca,Al-rich inclusions (CAIs). While osmium isotopic ratios of two randomly selected particles rule out a presolar origin, the bulk chemistry of 88 particles with sizes in the submicron range determined by energy dispersive X-ray (EDX) spectroscopy shows striking agreement with predictions of single-phase equilibrium condensation calculations. Both chemical composition and morphology strongly favor a condensation origin. Particularly important is the presence of structurally incompatible elements in particl…

Impact Energy Flux on Earth in the Last 150 Ma as Inferred from the Cratering Records

1998

We have used a compilation of 30 well-dated large impact craters on Earth (i.e., diameters larger than 5 km) younger than 150 Ma, their diameters, geochronologic ages, and the corresponding uncertainties to construct a graph summarizing our current knowledge on the influx of the impact energy onto the Earth as a function of time. From the crater diameters, we estimated the corresponding impact energies through suitable scaling laws. Then to each crater we associated a gaussian (bell) function of time centered at its age. Finally, all the bell functions corresponding to different craters were summed up and the resulting curve was plotted. From this curve, it is apparent that the 65 Ma old Ch…

Use of site symmetry in supercell models of defective crystals: Polarons in CeO2

2017

The authors thank R. Merkle and G. W. Watson for stimulating discussions. E. K. also acknowledges partial financial support from the Russian Science Foundation for the study of charged defects under the project 14-43-00052. A. C. also acknowledges financial support from the University of Latvia Foundation (Arnis Riekstins's "MikroTik" donation). E. K. and D. G. express their gratitude to the High Performance Computer Centre in Stuttgart (HLRS, project DEFTD 12939) for the provided computer facilities whereas R. A. E. thanks the St. Petersburg State University Computer Center for assistance in high-performance calculations.

Functional response of Phytoseiulus longipes Evans and Phytoseiulus persimilis Athias- Henriot (Parasitiformes, Phytoseiidae) to its prey Tetranychus…

2008

Turonian-Maastrichtian biostratigraphy and isotope stratigraphy of the Kopet-Dagh Basin deposits, northeastern Neo-Tethys, Iran

2021

Abstract Planktonic foraminiferal biostratigraphy and isotope stratigraphy analyses of Turonian-Maastrichtian deposits have been carried out in the western part of the Kopet-Dagh Basin. The identification of the planktonic foraminiferal assemblages has led to the recognition of twelve Upper Cretaceous zones (Helvetoglobotruncana helvetica Zone to the Contusotruncana contusa-Abathomphalus mayaroensis zone) from the Tethyan realm. The obtained stable carbon isotope profile correlates with other reference curves, revealing many Late Cretaceous events including the Hitchwood, Navigation, Light Point, East Cliff, White Fall, Late Campanian Event (LCE), Campanian-Maastrichtian Boundary Event (CMB…

A quantitative analysis of wild herbaceous plant species for medicinal uses in four Regional Parks in Sicily (Italy)

2019

This paper illustrates the results of a study carried out in 4 regional Parks in Sicily (Italy) from 2009 to 2010. The study area covers a surface of 2076 km2, the 8% of the territory of Sicily, includes 90 towns and it is characterized by a high degree of plant biodiversity. The main aim of the study was to analyse the extent of the current knowledge on medicinal uses of wild shrub and herbaceous plants in the area, using quantitative indices. The information was obtained using semi-structured interview format performed on a sample of 802 people over the age of 60 who were considered experts in rural traditions. The results highlight that most of the species are used against general health…

Formation of arcuate orogenic belts in the western Mediterranean region

2004

The Alpine orogen in the western Mediterranean region, consisting of the Rif-Betic belt and the Apennine-Calabrian-Maghrebide belt, is a classic example of an arcuate orogen. It contains fragments of Cretaceous to Oligocene high-pressure/low-temperature (HP/LT) rocks, which were exhumed and dispersed during post-Oligocene extensional deformation and are presently exposed in the soles of metamorphic core complexes. In this paper, we illustrate that the arcuate shape of the orogenic belt was attained during extensional destruction of the earlier HP/LT belt, driven by subduction rollback in a direction oblique or orthogonal to the direction of convergence. Since the Oligocene, sub-duction of M…