The Cenomanian–Turonian boundary on the Saharan Platform (Tunisia and Algeria)

Autor: Fettouma Chikhi-Aouimeur, Mustapha Bensalah, Serge Ferry, Hamid Aït Salem, Danièle Grosheny, Mohamed Jati, Fatiha Benkerouf-Kechid, Hedi Negra, Mohamed Ouaja, François Atrops
Přispěvatelé: Ecole et Observatoire des Sciences de la Terre (EOST), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement [Lyon] (LGL-TPE), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon), Laboratoire de géologie, université de Gabès, Université de Gabès, Département des Sciences de la Terre - Laboratoire de recherche n°25, Université Aboubekr Belkaid - University of Belkaïd Abou Bekr [Tlemcen], Laboratoires des sciences de la terre, Université des Sciences et de la Technologie Houari Boumediene [Alger] (USTHB), Unite Rech Petrol Cristalline & Sedimentaire UR 0, Université de Tunis El Manar (UTM), Algerian Petr Inst Boumerdes, Université M'Hamed Bougara Boumerdes (UMBB), Université de Strasbourg, Université d'Alger, PHC 'Tassili' 05 MDU 652, Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement (LGL-TPE), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), Université des Sciences et de la Technologie Houari Boumediene = University of Sciences and Technology Houari Boumediene [Alger] (USTHB)
Rok vydání: 2013
Předmět:
Zdroj: Cretaceous Research
Cretaceous Research, Elsevier, 2013, 42, pp.66-84. ⟨10.1016/j.cretres.2013.01.004⟩
Cretaceous Research, 2013, 42, pp.66-84. ⟨10.1016/j.cretres.2013.01.004⟩
ISSN: 0195-6671
1095-998X
DOI: 10.1016/j.cretres.2013.01.004
Popis: International audience; Several transects made of correlated stratigraphic sections and well logs have been constructed spanning southern Tunisia and the Algerian Sahara (Tinrhert) for comparison with earlier results obtained in the Saharan Atlas. The study is based on fades analysis, sedimentology, biostratigraphy focused on ammonites and foraminifers) as well as whole rock geochemistry (delta C-13). These suggest that the entire northern Sahara Platform underwent marine flooding that commenced just prior to the onset of the global positive delta C-13 shift documented for the Cenomanian-Turonian boundary. This flooding occurred in two phases. The first phase is expressed by the deposition of deeper-water, light-coloured bioturbated mudstones overlying the shallow-water deposits comprising the local Cenomanian successions. But in some places in the Central Sahara (Hassi Messaoud area, Tihemboka Arch) as well as in the Saharan Atlas, shallow-water carbonates kept up locally with the relative sea-level rise to build up isolated carbonate platforms. The topographic lows or saddles between these areas could have been formed through differential accumulation rates. During the second phase, flooding resumed and black shales were deposited over the mudstones in the saddles. The occurrence of black shales in these saddles is limited to the northern edge of the platform (Saharan Atlas of Algeria, Gafsa Trough in southern Tunisia). On the platform, this phase is represented by the same kind of mudstones deposited during the first phase of the flooding (southern Tunisia), or by ammonite-rich chalks in the intra-cratonic basin of the Tinrhert (southern Algeria). Black-shale deposition ceased in the early Turonian. Based on the delta C-13 curve, the latest Cenomanian flooding of the Sahara Platform is roughly coeval with that documented for the US Western Interior. During the first phase of the transgression, that is before the occurrence of the large Whiteinella of the W. archeocretacea Zone in the black shale unit, planktic foraminifers are dominated by small globulose forms of the Hedbergella delrioensis type, associated with Heterohelicidae. Keeled forms (rotaliporids, dicarinellids) are scarce and always very small when present. Perhaps these dwarfed forms were adapted to the restricted environments of the extensive intracratonic seaways crossing the Saharan Platform to the Benoue Trough in Nigeria.
Databáze: OpenAIRE
Externí odkaz: