Influence of relative sea-level variations on the genesis of palaeoplacers, the examples of Sarrabus (Sardinia, Italy) and the Armorican Massif (western France) - Archive ouverte HAL Access content directly
Journal Articles Comptes Rendus Géoscience Year : 2016

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

(1) , (2) , (1)
1
2
Marco Pistis
  • Function : Author
  • PersonId : 963146
Marie-Pierre Dabard
  • Function : Author
  • PersonId : 840697
Alfredo Loi
  • Function : Author
  • PersonId : 905813

Abstract

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.

Dates and versions

insu-01272116 , version 1 (10-02-2016)

Identifiers

Cite

Marco Pistis, Marie-Pierre Dabard, Alfredo Loi. Influence of relative sea-level variations on the genesis of palaeoplacers, the examples of Sarrabus (Sardinia, Italy) and the Armorican Massif (western France). Comptes Rendus Géoscience, 2016, 348 (2), pp.150-157. ⟨10.1016/j.crte.2015.09.006⟩. ⟨insu-01272116⟩
114 View
0 Download

Altmetric

Share

Gmail Facebook Twitter LinkedIn More