Search results for "Marl"

Séries condensées et indice de préservation d'unité biostratigraphique: exemple de l'ennoiement de la plate-forme nord-bourguignonne (France) au Call…

1999

Abstract Several depositional environments associated with Callovian-Oxfordian condensed series of the southeast of the Paris Basin are defined. As sedimentation rates were very low, variations in palaeodepth, which were synchronous at regional scale, were taken to directly reflect fluctuations in accommodation potential. Within a major trend toward increased accommodation potential, five sharp upturns and one sharp downturn are detected. A biostratigraphic unit preservation index is denned to quantify and discuss the low preservation of sediments in these condensed series. This index is seen to vary with accommodation potential.

Rare earth elements in limestone/marlstone couplets from the Albian-Cenomanian Cismon section (Venetian region, northern Italy) : assessing REE sensi…

1997

Abstract We have studied the REE distribution through the Albian-Cenomanian interval of a stratigraphic succession (Cismon section, Scaglia Variegata Formation, Venetian Prealps) consisting of rhythmically alternating carbonate-rich and carbonate-poor strata which are the sedimentary expression of systematic variations of surface fertility and bottom-water redox conditions in the depositional basin. Limestone semicouplets show seawater-like shale-normalized patterns (HREE-enriched, with negative Ce anomalies and high Er/Nd ratios) indicating a clear dependence on the REE chemistry of surface seawaters. Marlstones and shales exhibit flatter patterns, more moderate Ce anomalies and low Er/Nd.…

Middle Eocene calcareous nannofossils in the Jaca transect (South-central Pyrenees Eocene Basin, Aragón river valley, Huesca)

2020

The calcareous nanoplankton is studied from the base of the turbidite systems of the Upper Hecho Group (Jaca Basin, middle Eocene of the South-central Pyrenean Basin) up to the Gracionepel instabilities, within the Larres slope Marls. This new chronostratigraphic contribution is of crucial importance for the improvement of the detailed temporal and spatial correlation framework of the genetically related depositional systems at basin scale. The calcareous nanofossil assemblage is largely dominated by Coccolithus pelagicus , C. formous as well as different species of Reticulofenestra , accompanied by occasional specimens of several species of Sphenolithus  and Chiasmolithus . The results obt…

Deep-seated gravitational slope deformations in western Sicily: Controlling factors, triggering mechanisms, and morphoevolutionary models

2014

Abstract A study of deep-seated gravitational slope deformation (DSGSD) phenomena affecting areas of various geological and geomorphological settings in western Sicily is described. Western Sicily is underlain by a thin-skinned imbricate wedge of Meso–Cenozoic carbonate and siliciclastic rocks that formed by the stacking of several thrust nappes over the Iblean foreland. Locally, the original thrust sheets are folded and cut by high-angle faults. Large areas of western Sicily now display high relief energy due to Plio-Pleistocene block-faulting and uplifting, and the Quaternary morphogenetic phases are characterised by incision, thereby triggering widespread DSGSDs. To identify controlling …

Sequence stratigraphy and paleo-oceanography of an open-marine mixed carbonate/siliciclastic succession (Late Jurassic, Southern Germany)

1992

The Late Jurassic epicontinental sea of South Germany protruded far to the North forming a wide bay which was rimmed by shallow-water platforms (Swiss and French Jura). This wide shelf is characterized by extensive downslope mud accumulations including siliceous sponge buildups. The bioherms are aligned along the more pericontinental parts of this shelf, which graded to the South into the Helvetic Basin of the Tethys Ocean.

Methane-derived carbonate conduits from the late Aptian of Salinac (Marne Bleues, Vocontian Basin, France): Petrology and biosignatures

2015

Abstract Peculiar carbonate bodies occur in distinct marl layers of the Marnes Bleues Formation (Aptian–Albian, Vocontian Basin, Southern France). The carbonate conduits exhibit pipe- or sausage-like forms and a central channel. Their sizes range between 30 and 60 cm in length and 5–10 cm in diameter. The conduit carbonates consist of automicrite authigenically formed within the sediment. Millimeter-sized aggregates of framboidal pyrite are abundant within the conduit automicrites, probably representing former colonies of sulfate reducing bacteria. The central channel reflects former pathways of reduced fluids in the carbonate conduit. Ni-enrichments at the margins of the central cavity are…

De la ignorancia del arte

2016

L'historique du tunnel sous la manche : une brève revue des contributions les plus marquantes

2014

The Channel Tunnel is the largest underground geotechnical project undertaken in Europe during the 20th century. There have been numerous proposals since the early 19th century, especially by Thomé de Gamond (1867), Potier and de Lapparent (1877), and Destombes and Shephard-Thorn (1971). This paper discusses the history of the most important geological investigations for the Channel Tunnel bored in the Lower Cenomanian Chalk Marl.

Orbitally induced limestone/marlstone rhythms in the Albian—Cenomanian Cismon section (Venetian region, northern Italy): Sedimentology, calcareous an…

1996

Abstract A multidisciplinary study of the upper Albian—Cenomanian portion of the Cismon section (Venetian region, northern Italy) was undertaken in order to characterize the cyclic alternations of carbonate-rich and carbonate-poor layers and to investigate their possible origin and cyclic patterns. Limestone semicouplets are characterized by abundant radiolarians and micarbs (micron-sized calcitic fragments), common planktonic foraminifera, strong bioturbation, good oxygenation as expressed by the Mn* and V/(V+Ni) parameters, high Si/Al ratio, low K/Al, in the absence of pyrite and organic matter. The marlstone semicouplets are, on the contrary, frequently laminated, rich in pyrite and orga…

Orbitally modulated black shale deposition in the upper Albian Amadeus Segment (central Italy): a multi-proxy reconstruction

2003

Abstract The upper Albian Amadeus Segment, which falls within Oceanic Anoxic Event 1c, exhibits cyclical alternations of marls/black shales and carbonate-rich beds that record evidence of orbital climate and sedimentary dynamics. A combined micropalaeontological (planktic and benthic foraminifera, and palynomorphs) and geochemical (stable isotopes, clay mineralogy, and major element distribution) investigation allowed recognition of a remarkable influence of continental material within the black shales. Moreover, the palaeoproductivity record is characterised by a non-linear response to the orbital forcing. The micropalaeontological and geochemical record suggests that upper Albian bedded c…