The development of the Carboniferous Ben-Zireg–Zousfana Trough in the northern part of the Béchar Basin, Western Algeria: implications for its structural evolution, sequence stratigraphy and palaeogeography

✍ Scribed by Fatima Zohra Malti; Miloud Benhamou; Larbi Mekahli; Madani Benyoucef

• Publisher: John Wiley and Sons
• Year: 2008
• Tongue: English
• Weight: 907 KB
• Volume: 43
• Category: Article
• ISSN: 0072-1050
• DOI: 10.1002/gj.1114

✦ Synopsis

Abstract

The sequence stratigraphical study of the Viséan Formations shows the importance of the Ben‐Zireg Trough for the structural development of the Béchar Basin. The sequence stratigraphical approach has allowed to decipher the systems tracts, which have filled the accommodation space of the Ben‐Zireg Trough under tectono‐eustatic control. A deep sea fan recorded by the first flysch‐type deposits transported by submarine canyons was followed by a prograding lowstand wedge recorded in the flysch with olistostromes, a transgressive system tract (TST) identified by flysch‐type deposits without olistostrome, and a highstand system tract (HST) represented by the patch reef and flyschoid deposits. The biostromal barrier and platform limestones indicate also a TST and sometimes a shelf margin wedge (SMW). Thus, these stratal patterns have been identified as Types 1 and 2 genetic sequences of third‐order eustatic cycles and are based on correlations of cross‐sections located around the Ben‐Zireg Anticline.

During the Tournaisian, the Ben‐Zireg Anticline, the Djebel Ioucha, the ‘Grand Erg Occidental’ and the Erfoud areas were uplifted to form palaeohighs, whereas the Zousfana and Saoura Valley areas were situated in a trough position. There were also created sub‐basins north of Ben‐Zireg; from Grouz (Teniet El Haïdoura) to Soltane El Betoum, and southeast of the Meharez High.

During the Early Viséan, an inversion of the Ben‐Zireg High occurred, resulting in a widening and deepening of the Ben‐Zireg–Zousfana Trough. In the Upper Viséan formations, peri‐reefal limestone beds appear in the current position of the Djebel Béchar. Further west in the Chebket–Mennouna–Djihani area occur small patch reefs. On the eastern edge, the bioherm formations were described previously as ‘Waulsortian‐like reefs’ of the ‘Grand Erg Occidental’. These facies recorded the TST. Thus, a carbonate platform became established at the expense of the Ben‐Zireg–Zousfana Trough. Copyright © 2008 John Wiley & Sons, Ltd.