Dernière mise à jour le : 20 janvier 2016

Influence of relative sea-level variations on the genesis of palaeoplacers, the examples of Sarrabus (Sardinia, Italy) and the Armorican Massif (western France)

DESCRIPTION

The aim of this work is to analyse the role of allocyclic processes in the genesis of marine Ordovician palaeoplacers laid down on a terrigenous shelf dominated by storm waves. Sedimentological (facies, sequence stratigraphy) and petrographic analyses combined with natural radioactivity measurement (gamma ray) are carried out. Two facies containing heavy minerals are identified: a shoreface facies and a proximal upper offshore facies. Heavy minerals (mainly titaniferous minerals, zircon and monazite) are concentrated in laminae that can amalgamate to form placers that are several decimetres thick. Their occurrence is highlighted by an increase in the total radioactivity (up to 140,000 cpm) and in the U and Th contents (up to 130 ppm and 800 ppm, respectively). The palaeoplacers are the result of a combination of autocyclic and allocyclic factors. In the stratigraphic record, the palaeoplacers are located in the retrogradation phases and express condensation processes in the nearshore environments.

NOTICE BIBLIOGRAPHIQUE DETAILLÉE

keyboard_arrow_right Titre : Influence of relative sea-level variations on the genesis of palaeoplacers, the examples of Sarrabus (Sardinia, Italy) and the Armorican Massif (western France)
keyboard_arrow_right Type de documentation : Articles
keyboard_arrow_right Auteur(s) personne(s) : Loi Alfredo, Dabard Marie-Pierre, Pistis Marco
keyboard_arrow_right Date de publication : 20 janvier 2016
keyboard_arrow_right Nombre de pages : 150-157
keyboard_arrow_right Editeur(s) : Unité mixte de recherche Géosciences Rennes (UMR 6118)
keyboard_arrow_right Tags thématiques : charge en métaux lourds, métal lourd, radioactivité, niveau de la mer, sédimentologie
keyboard_arrow_right Mots-clés libres : élévation du niveau marin/Gamma ray/Heavy minerals/Ordovician/Sea-level changes/Sequence stratigraphy/Armorican Massif/western France
keyboard_arrow_right Langue : Anglais
keyboard_arrow_right N° d'édition (ISBN,DOI...) : 10.1016/j.crte.2015.09.006
keyboard_arrow_right Collection : COMPTES RENDUS. GEOSCIENCE

Contenus associés

Les plus récents

Les plus Consultés

Les plus Recommandés

keyboard_arrow_up Haut de page
thumb_up
Je recommande

2

lecteurs recommandent cet article

perm_identity

1 vue

Je recommande

2

lecteurs recommandent cet article

Partager :