F. Paris et al., BIOSTRATIGRAPHY AND PALEOGEOGRAPHIC AFFINITIES OF EARLY SILURIAN CHITINOZOANS FROM CENTRAL SAUDI-ARABIA, Review of palaeobotany and palynology, 89(1-2), 1995, pp. 75-90
Palynological investigations carried out on subsurface material have d
emonstrated the occurrence of rich and well diversified Llandovery chi
tinozoan assemblages in the Qusaiba and Sharawra members of the Qaliba
h Formation in Saudi Arabia. Both core and cuttings samples from wells
located in the central part of Saudi Arabia have been investigated. T
he biozonation and stratigraphic correlations proposed here are exclus
ively based on core material. Eight local chitinozoan biozones are dis
tinguished within the investigated Llandovery subsurface strata. Becau
se of significant contamination due to caving in the cuttings samples
these are only used to control the extension of the biozones in the in
tervals devoid of core samples. Several species of the most abundantly
recorded chitinozoans in the Early Silurian of Saudi Arabia are typic
al components of contemporaneous chitinozoan assemblages from the subs
urface of Libya, Algeria and to a lesser extent from outcrops in north
western Spain (e.g. Plectochitina paraguayensis, Conochitina edjelensi
s, C. alargada, C. elongata, Pterochitina deichai, Belonechitina parav
itrea). In addition to these typical North Gondwanan species, a few fa
irly ubiquitous forms are helpful for inter-palaeocontinental correlat
ions (e.g. Spinachitina S. agilis, S. maennili). The relationship exis
ting between North Gondwanan chitinozoan assemblages and the Baltic on
es are quantified for Aeronian time by calculating their respective co
efficient of similarity. A great similarity exists between North Gondw
ana and Saudi Arabia chitinozoan populations from the Middle Llandover
y. On the other hand, moderate to fairly low similarities are noticed
with the contemporaneous chitinozoan populations from Baltica. Such re
sults are consistent with the existence of a wide mid-European Rheic O
cean implying a remote latitudinal position between Northern Gondwana
and Baltica and consequently contrasting climatic conditions prevailin
g on both margins of this ocean. So far, no typical Afro-Brazilian chi
tinozoan species (9.8. Pogonochitina djalmai) have been recorded in th
e Saudi assemblages. Although data on the Llandovery chitinozoan assem
blages from Asia are still limited, some affinities, at the specific l
evel, between the Saudi and the Chinese material are observed.