{"title":"New insights from the Choteč Event (early Middle Devonian) in the Marhouma section (Ougarta range, SW Algeria)","authors":"Radia Tandjaoui , Abdelkader Ouali Mehadji , Carine Randon , Houssem Sassi","doi":"10.1016/j.jafrearsci.2024.105486","DOIUrl":null,"url":null,"abstract":"<div><div>The stratigraphic reference section of the Marhouma area (the so-called km 30 section) in the Ougarta Range (North Western Algerian Sahara) provides valuable insights for the Emsian/Eifelian boundary (Lower/Middle Devonian) around the main lithological facies change expressed between the Teferguenite Chefar el Ahmar Formation. This paper presents new data allowing to better constrain and locate regionally the previously established boundary and to locate the Choteč Bioevent. This revision places the boundary below the new record of <em>Icriodus introlevatus</em> Bultynck, 1970 in Bed 3. The ammonoid assemblages place this boundary either at the base of level 25 <em>sensu</em> Göddertz (1987), without excluding placing it a position several meters lower, above the “niveau coralligène of Le Maître (1952)”. The “Choteč” Bioevent is distinguished within a likely polyphase, stepwise local development: i) a facies change well-expressed by a shift from benthic bioclastic packstones to pelagic wackestones (styliolinites); ii) an increasing deepening (thickest marly interval above level 25, Bed 2); iii) the <em>Icriodus introlevatus</em> wackestone Bed 3; iv) a bloom of goniatites (including <em>Pinacites jugleri</em> (Roemer, 1843) and <em>P. eminens</em> Chlupáč and Turek, 1977) in Bed 4, and finally v) a bloom of micromorphic brachiopods in Bed 5, which reflects monospecific mass reproduction due to increased specific trophic levels. This scenario happened in an alternation of marl-limestone layers with a <em>Zoophycus-Chondrites</em> ichnofossil assemblage, interspersed by greenish claystones and calcareous nodule rich in dacryoconarids. The platy shell bed (Bed 5) represented by micromorphic brachiopods represents the peak phase of Choteč Event Interval ranging locally from Bed 4 to Bed 5, and corresponding to Göddertz's level 27.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"222 ","pages":"Article 105486"},"PeriodicalIF":2.2000,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of African Earth Sciences","FirstCategoryId":"89","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S1464343X24003200","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"GEOSCIENCES, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
The stratigraphic reference section of the Marhouma area (the so-called km 30 section) in the Ougarta Range (North Western Algerian Sahara) provides valuable insights for the Emsian/Eifelian boundary (Lower/Middle Devonian) around the main lithological facies change expressed between the Teferguenite Chefar el Ahmar Formation. This paper presents new data allowing to better constrain and locate regionally the previously established boundary and to locate the Choteč Bioevent. This revision places the boundary below the new record of Icriodus introlevatus Bultynck, 1970 in Bed 3. The ammonoid assemblages place this boundary either at the base of level 25 sensu Göddertz (1987), without excluding placing it a position several meters lower, above the “niveau coralligène of Le Maître (1952)”. The “Choteč” Bioevent is distinguished within a likely polyphase, stepwise local development: i) a facies change well-expressed by a shift from benthic bioclastic packstones to pelagic wackestones (styliolinites); ii) an increasing deepening (thickest marly interval above level 25, Bed 2); iii) the Icriodus introlevatus wackestone Bed 3; iv) a bloom of goniatites (including Pinacites jugleri (Roemer, 1843) and P. eminens Chlupáč and Turek, 1977) in Bed 4, and finally v) a bloom of micromorphic brachiopods in Bed 5, which reflects monospecific mass reproduction due to increased specific trophic levels. This scenario happened in an alternation of marl-limestone layers with a Zoophycus-Chondrites ichnofossil assemblage, interspersed by greenish claystones and calcareous nodule rich in dacryoconarids. The platy shell bed (Bed 5) represented by micromorphic brachiopods represents the peak phase of Choteč Event Interval ranging locally from Bed 4 to Bed 5, and corresponding to Göddertz's level 27.
期刊介绍:
The Journal of African Earth Sciences sees itself as the prime geological journal for all aspects of the Earth Sciences about the African plate. Papers dealing with peripheral areas are welcome if they demonstrate a tight link with Africa.
The Journal publishes high quality, peer-reviewed scientific papers. It is devoted primarily to research papers but short communications relating to new developments of broad interest, reviews and book reviews will also be considered. Papers must have international appeal and should present work of more regional than local significance and dealing with well identified and justified scientific questions. Specialised technical papers, analytical or exploration reports must be avoided. Papers on applied geology should preferably be linked to such core disciplines and must be addressed to a more general geoscientific audience.