Polyphased dolomitization of a shoal-rimmed carbonate platform: example from the middle Turonian Bireno dolomites of central Tunisia

Examining the interplay of climate and low amplitude sea‐level change on the distribution and volume of massive dolomitization: Zebbag Formation, Cretaceous, Southern Tunisia

“…Continued sea‐level rise over a vast and flat area in the Cenomanian led to deposition of shallow‐water peritidal and shallow subtidal facies with low diversity, salinity‐tolerant fauna such as gastropod, and miliolid, wackestones to mudstones and a single evaporite horizon (Bodin et al ., ). This suggests variable salinity levels with minimal circulation during deposition (Touir et al ., ). The boundary between the Rhadouane and Kerker Members is gradual and defined by a transition from clay‐free to clay rich marl‐dominated facies (Bodin et al ., ).…”

“…A fully upward‐shallowing succession is seen within the Gattar Member, culminating with the development of tidal flats and deposition of evaporites within troughs in central Tunisia (Camoin, ; Abdallah, ). The Annaba marls, which directly overlie the Gattar Formation in northern central Tunisia, are not seen in the Jeffara Escarpment where the Gattar Formation is covered by the Beida Anhydrites (Touir et al ., ).…”

“…This led to an ice‐free, hot and stable greenhouse climate by the middle Cretaceous (MacLeod et al ., ; Bodin et al ., ). The Upper Cretaceous has a low global abundance of dolomite (Given & Wilkinson, ; Sun, ), although massive dolomitization is observed in North Africa (Abdallah, ; Touir et al ., ; Bodin et al ., ) and southern Europe (Korbar et al ., ; Husinec & Sokač, ; Benito & Mas, ; Iannace et al ., ). This study considers why dolomitization was so widespread in this region, despite calcitic seas, low amplitude changes in relative sea‐level and a humid global climate – none of which are conducive to dolomitization.…”

“…Previous studies document the diagenesis and dolomitization of Albian to Turonian strata in north‐western Libya (Koehler, ; Chaabani et al ., ; El‐Bakai et al ., ) and central Tunisia (M'rabet, ; Abdallah, ; Touir et al ., ), but no previous work has been conducted on the Zebbag Formation of southern Tunisia. The origin of dolomitization within laterally equivalent strata has been variously attributed to reflux of hypersaline brines (M'rabet, ; Abdallah, ; Touir et al ., ), normal marine fluids (Al‐Aasm, ; Touir et al ., ), mixed marine‐meteoric fluids (Koehler, ; Abdallah, ; Al‐Aasm, ) and deep phreatic fluids of continental origin (M'rabet, ). This study will present a multidisciplinary and multi‐scale evaluation, using petrographical, geochemical and field evidence in order to fully evaluate the controls on dolomitization.…”

Paleoenvironmental framework of dinosaur tracksites and other ichnofossils in Early Cretaceous mixed siliciclastic-carbonate deposits in the Neuquén Basin, northern Patagonia (Argentina)

“…Dolomitization is a process that generates an alkaline environment (Bontognali et al, 2010). Vadose dolomitization is explained by different mechanisms (see Touir et al, 2009). In the Agrio Formation, Tunik et al (2009) concluded that dilution of marine waters took place during lowering of the sea level, permitting mixing of marine and meteoric waters as the main reasons of such dolomitization.…”