East-west trending reef belt
Mainly composed of Archaeolithoporella and Tubiphytes.
Abstract of ref. 1327:
Tubiphytes and Archaeolithoporella are two important building calcareous algae in Permian reefs, especially in the Upper Murghabian of Jebel Tebaga (Tunisia). Systematics of the two algae (probably blue-green) is reviewed.
Tubiphytes and Archaeolithoporella were previously poorly known in the Upper Permian beds from Jebel Tebaga. These algae, always associated, take a prominent part in the building of the reefs. The analysis of the reefs, 20 m thick and 60 m wide, shows the following biological sequence: a) Prereefal first stage: settling of clay-marly sediments including several calcareous organisms, mainly Calcisponges and Bivalves. b) Second stage: Whole organisms or
remains are encrusted by a first generation of the stromatolitic algae Archaeolithoporella, which will be colonized in a second time by the blue-green algae Tubiphytes. The former, rapidly attached, show a growth which follow the exact shape of the anfractuosites of Archaeolithoporella laminae. Open spaces and cavities created by the growth of alga assemblages are progressively filled by an internal micritic sediment with pellets. This open space filling by a fine material suggests a growth of Tubiphytes in restricted conditions, where the luminosity is lessen, indicating a sciaphilous alga. c) Third stage: Attachment and proliferation of a second generation of dense Archaeolithoporella.
    They encrust Tubiphytes and other substrates, growing laterally and vertically. The crusts of Archaeolithoporella are parallel to the substrate at the beginning of the growth, but a few millimeters higher appears a mammillated crust, which gives, at the end of the growth, some nodules with concentric laminations, often trapped in interstitial micritic fills.
 These nodules are called here tebagites. This biologic sequence occurs repeatly from the bottom to the top of the reef. Furthermore, examination of relations between the growth of Archaeolithoporella and the early diagenetic features (cements) allows to establish, in addition to the biologic sequence, a diagenetic sequence summarized as following: -
    growth of dense micritic laminae. - Growth of clear and dark laminae (i.e. typical stage). - Growth of vesicular laminae filled by fibrous or botryoidal cement. - Stop of algae growth, followed by a filling of the interalgal porosity with a botryoidal cement or an internal peloidal sediment. In conclusion, Tubiphytes and Archaeolithoporella constitute the main building organisms of the studied reefs. Identical assemblages are known from the Lower Permian of Carnic Alps,
from Upper Permian of Yugoslavia and Capitan Reef in U.S.A. as well, under the name of Calcisponges/Algal/Cements
    Reefs (-CAC, new abbreviation). 