• Aucun résultat trouvé

A review of Silurian dispersed spore assemblages from the Arabian Plate: biostratigraphy and palaeogeography

N/A
N/A
Protected

Academic year: 2021

Partager "A review of Silurian dispersed spore assemblages from the Arabian Plate: biostratigraphy and palaeogeography"

Copied!
1
0
0

Texte intégral

(1)

A review of Silurian dispersed spore assemblages from the Arabian Plate: biostratigraphy and palaeogeography

Charles H. Wellman1, Philippe Steemans2, Pierre Breuer3, Marco Vecoli3

1Department of Animal and Plant Sciences, University of Sheffield, Alfred Denny Building, Western Bank, Sheffield S10 2TN, UK, c.wellman@sheffield.ac.uk

2Laboratory of Palaeobiogeology, Palaeobotany, Palaeopalynology, Liège University, 4000 Liège, Belgium

3Saudi Aramco, Geological Technical Services Division, Biostratigraphy Group, 31311 Dhahran, Saudi Arabia

Establishing a global Silurian dispersed spore biostratigraphy has been plagued by a number of long-standing problems: (i) spores are absent or rare in global stratotypes for the Ordovician-Silurian and Silurian-Devonian boundaries that are located in marine facies; (ii) spore endemicity is high on the dispersed Silurian continents hampering intercontinental correlation. Silurian spores from the Arabian Plate have been described from the Qalibah and Tawil formations. The Ordovician-Silurian boundary is difficult to locate due to the complicated stratigraphy (with downcutting, glacial tillite infill etc.) and extensive palynomorph reworking associated with the Hirnantian glaciation. However, rich Llandovery and Wenlock-Ludlow spore assemblages described from the marine deposits of the Qalibah Formation: Qusaiba Member and Qalibah Formation: Sharawra Member, respectively. Spores are currently poorly documented from the continental deposits from the lower part of the Tawil Formation, but sparse assemblages recovered from cuttings samples indicate a probable Ludlow age. However, rich and well preserved mid Pridoli spore assemblages are now known from marginal marine deposits from a marine intercalation higher in the Tawil Formation. The exact location of the Silurian-Devonian boundary within the Tawil Formation a has yet to be pinpointed. The Silurian spore assemblages from the Arabian Plate show significant differences to those from beyond

Gondwana highlighting the extent of palaeophytogeographical differentiation and hence problems of intercontinental correlation for Silurian spores. Statistical analysis of these differences, using

coefficient of similarity (CS), will be reported in this presentation.

Références

Documents relatifs

In general, unfavorable environmental conditions affect the metabolism of bacteria, leading to inhibition of both growth and sporulation.. The general stress response

L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des

2 Observed precision for global acute malnutrition (GAM), moderate acute malnutrition (MAM) and severe acute malnutrition (SAM) calculated by the classical method (——) or the

The Lower Devonian Posongchong Formation (Wenshan, Yunnan Province, southwestern China) comprises a series of continental clastic deposits, from which 28 vascular plant gen- era

This species presents a small trochospire, a well developed marginal zone, and a central zone with short massive pil- lars, thick chamber walls and very large oblique or

Skillful retrocession of both urban areas and shipping activity between 1977 and 2000 consolidated the emergence of the central region, comprising these two port

G.stearothermoph i lusandM.thermoacet ica/thermoautotroph ica preva lence va lues d id not d i f fer s ign ificant ly between year-2011 and year-2012 samp les , except

Geomagnetic paleosecular variation recorded in Plio-Pleistocene volcanic rocks from Possession Island (Crozet Archipelago, southern In- dian Ocean)... JOURNAL OF GEOPHYSICAL