Title :

Shell Beds in Ordovician storm- to tide-dominated deposits, Daoura (Ougarta range), Algeria

Author(s) :

Metatla, Imene [Auteur]
Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 [LOG]
Reynaud, Jean-Yves [Auteur]
Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 [LOG]
Ghienne, Jean-François [Auteur]
Vinn, Olev [Auteur]
Tartu University Hospital
Harouz, C. [Auteur]
Université des Sciences et de la Technologie Houari Boumediene = University of Sciences and Technology Houari Boumediene [Alger] [USTHB]
El Albani, Abderrazak [Auteur]
Hydrogéologie, Argiles, Sols, Altérations [E2 – IC2MP équipe 2] [HydrASA]
Mazurier, A. [Auteur]
Hydrogéologie, Argiles, Sols, Altérations [E2 – IC2MP équipe 2] [HydrASA]
Mahboubi, S. [Auteur]
Université de Tlemcen

Journal title :

Bulletin of Geosciences

Pages :

149-168

Publisher :

Czech Geological Survey

Publication date :

2024

ISSN :

1214-1119

English keyword(s) :

Upper Ordovician
wave-dominated ramp
shell beds
tide-modulated shoreface
cornulitids
tempestites
Daoura
Ougarta
Algeria

HAL domain(s) :

Planète et Univers [physics]/Sciences de la Terre/Stratigraphie

English abstract : [en]

The Ordovician wave-dominated sandstones of the Daoura (Ougarta range, NW Algeria) contain shell beds with cornulitids in an exceptional state of preservation. The objective of this study, focused on the sandstone of the ...
Show more >The Ordovician wave-dominated sandstones of the Daoura (Ougarta range, NW Algeria) contain shell beds with cornulitids in an exceptional state of preservation. The objective of this study, focused on the sandstone of the uppermost part of the Hassi Chaamba Fm. (Sandbian?), is to understand the shell beds from the hydrodynamic and stratigraphic perspective with the combined approach of facies sedimentology and taphonomy. A 40-m section encompassing the shell beds was studied in detail. The shell beds are preserved as dm-scale concentrations in transgressive deposits of 5 high-frequency sequences preserved at the turnaround from a regressive to a transgressive sequence set. The biota in shell beds are dominated by brachiopods, cornulitids and gastropods, suggesting that the related ecosystem extended to the offshore. Three types of shell beds are distinguished, ranging from a conglomerate in the foreshore to a hardground in the offshore transition. In the lower shoreface, the shell beds are interstratified with fine-sand SCS infilling large-scale (up to 20 m in wavelength) troughs eroded in the foreshore by transgressive ravinement. The petrographic and tomographic analysis of a sample of these shell beds shows that cornulitids and, to a lesser extent, brachiopods of the shell beds are perfectly preserved within a matrix composed of bioclasts. This suggests that they were reworked from nearby areas and therefore were present in the foreshore. Aggregation of cornulitids in clusters of 4–5 individuals suggests an adaptation to loose grounds in a relatively high energy setting. The rhythmic alternation of shell beds and sandstones in these deposits suggests a possible role of tides in their formationShow less >

Language :

Anglais

Peer reviewed article :

Oui

Audience :

Internationale

Popular science :

Non

Collections :

• Laboratoire d'Océanologie et de Géosciences (LOG) - UMR 8187

Source :

Harvested from HAL